Tunnel Tabs on Cats

[Liberator24]

I would like to hear from those of you who have some experience with Tunnel Tabs on Cats. I am buying a Liberator 24 and I have seen some Skater 24's with tabs and read a little on the subject from some on this forum, but I am really curious as to the need for them, what their benefits are (if any) and how well they work, how big do they need to be, etc. I would also like to hear from users of these tabs regarding their techniques when using the tabs. As you can tell, I'm in a learning mode and there is no substitute for experience. I have none so I'm hopeing you'll share yours with me.

[jerry]

jerry knows the skater will porpoise between 40 and 75 . the tunnel tab when lowered will stop this . I f you hit the tab going very fast you will bury the nose and stuff the **** put of the boat and maybe even go end over end .. It is nice to have because the boat porpiosing can get annoyning. jerry has spoken

[Liberator24]

Jerry, Thanks for the info, is your experience with the tabs first hand or in the third person?

[WILDMAN]

If you post on Offshore Only, There are many more guys who know about them.

[LaserModVee]

Do what Wildman says and post over on OSO.

If you want more info from other good sources here are a couple that come to mind-

For first hand experience, send an e-mail to a guy that rarely posts on here but goes by the name Dd24skater. Look him up in the members section and ask him about tunnel tabs. He was a throttle man on a 24 Skater for four years and owns his former race boat still today.

Send an e-mail to Lambchop77. He, his father and his brother have driven and owned Skater's from 21 to 32 feet for 15 years now. They have had many of them on Lake X for set up tweaking and are very knowledgable on this subject.


Good luck

[Liberator24]

Don't want to sound too stupid, but I assume Offshore only is a website and my search engine didn't get any hits that looked right. Could you include the URL?

[LaserModVee]

OSO (http://www.offshoreonly.com/forums/index.php?s=)

[Liberator24]

Thanks for the link!!

[Racemore]

tried to get slosh tank info and didn't learn dick.The only responce was I need to run 1/2" line everywhere.I'm not feeding 572's:rolleyes: Tab's on Skaters, i've seen them on a few and they are for river running/porpoise control.I raced a Motion and it didn't need a crutch.Alot of Skaters were racing but i didn't see them running very often.:cool:

[skatermike24]

I have one on my Skater and love it, it let's the boat plane faster and easier, it removes the porpoising I had, which most cats have, and does help on top end. I recommand it!

[TUFFboat]

First of all the use of a tunnel tab is an advanced technique, be intune with your boat before playing. It is bennifical in two ways, high speed, using air pressure, and rough water, using the water pressure.
At high speed you simply lower the tab to give you tail lift. At the same time you would be running bigger diameter props to give you bow lift, and you have just elevatated the whole boat and it goes faster. Bad news is its less stable, if you throttle down with alot of tab it will want to bow steer.
In the rough water (the real magic). Imagine hitting a wave and the bow starts to drive up over it, the boat is going to launch bow high. With the tab down the right amount, the same wave comes down the tunnel and hit the tab which knocks the boat level again. When you get this balance you can trim in less and get more drive forward. Bad news is really bad, If you did'nt set up right or throttle right and stood the boat up anyway, you will open yourself up to a HEAVY stuff. More people have died stuffing the 24 in races than any other way. BE sure you can hear your boat talk to you before you go nuts.
As for the porpoising, a properly balanced boat (read: set-up for rough water) will have a small window of bumping. All the tab does is when the boat lifts up to start the cycle, the angle of the boat changes upward and the tab which is lowered now touches the water and bumps it back down. That gets annoying real fast. If you make the tab bigger to soften the porpoise even more, (lifting from the air as well) you magnify the other problems mentioned above as well.
As for size, the picture in the other thread is all we ran, I've seen one bigger one but the square one solved all my problems.
Buy the boat, its an excellent design, run it for a year, then deside if you even need more.

[Racemore]

For recreational use it takes the nagging traits out and allows a boat to go alittle faster I guess and some may use it racing but it will narrow the amount of margin of error.Sometimes you will find if you learn to work around a problem it isn't as much of a problem.If you get out and play in some conditions it is another variable to deal with and sometimes you may have your hands full and another button to work could be to much.Horsepower is your best source of control.:cool:

Liberator24,i think your boat has the dash moved forward 18" and raised 6" for cuddy access.It seems that it would change center of gravity over the Skater.Might want to consider the wait and see attitude.Drivers Wanted.:D :) :cool:

[jerry]

jerry will have to disagree with tuff boat !! The boat porpoises at these speeds because the boat is trying to lift itself out of the water , not because its poorly balanced . jerry has been in enough skaters ( 24s to 46s ) and they all porpoises!!! The air is being packed in to the tunnel and it drops the boat until there is enough air to hold it up .The tab will sorta close the back of the tunnel to create more lift .Tab should not be hitting the water at 60 mph ,,,,,,, JERRY HAS SPOKEN .

[at100plus]

What can be done to quell the porpoise on a single engine 21 Skater?

I know I'm going to get annoyed with the porpoise, and in calm water, I often like to cruise in the 50 to 60 mph range. What can I do to alleviate the porpoise?

Has anyone here ever seen or heard of the tunnel extensions that Lightning Powerboats uses on his Skater copy? Do they work? Are they only for twin applications?

[Racemore]

To me 21's have a big boat tunnel like a sawed off 24.the air packs the boat more in the middle making you trim up to get the bow flying and it's a loose setup.Running loose can cause problems when you run up on a 3 ft hole from a 2 ft wave and it happens alot on big water.

[woodco]

What TuffBoat described !!!!!!!! ;)

[TUFFboat]

Gentlemen, please lets not make a big deal of porpoising, if your set-up is half decent the porpoise window is small, just stay out of it. And to let it jump all the way down the lake is no big thing, its not going to hurt you. (stuffing will) If your nervous about it, trim in and power through it then let it fly.
Yes you can put a tab system on a single, two little ones on either side of the motor allowing for steering room. But its more weight, more stuff etc. Since porpoising generally happens around 70-75 you shouldnt have any issues at you 50-60 range anyway.
Its much more important to give your little cat alot of respect and enjoy it.
If Jerry checks a previous thread were I describe porpoising he will find that he accually agrees with me.

[sho305]

Most of these I have seen are pretty big tabs for the hull size...I would strongly recommend you know your hull handling very well before you mess with them. I know many who got into trouble with them on a deep vee hull, trying to push it too far with tabs. I would consider them tools for the experienced, especially on a tunnel. Better to get a bigger boat if you are not that experienced and want to run that kind of water fast; or put in the time to learn them well. Just trying to help.:)

[at100plus]

What about tunnel extension. What is it supposed to do?

[sho305]

The same thing, but it is not adjustable. Just packs/traps more air in the tunnel for lower plane speeds and more lift. Maybe not so good in nasty water.

Problem with the tabs is someone will run it way down, then go faster and end up getting out of shape; and when they get some air on a wave it will grab coming down, and slap or stuff(in a tunnel) hard. Most people I knew that got hurt got broken bones/faces from flying around in the boat with the vees. Sometimes flying out, and most times it was a passenger. It was ok until the wave was a hair too big and it launched. Vees slap hard on the side when a tab grabs. It is not such a big deal on a larger boat, say 28' and more. We were breaking seats, mounts, and doors all the time until he got a bigger boat out in lake MI, running maybe 3-4 footers most of the time. We never ran much tab at wot for that reason. Better to have more power and trim down. I think tabs are not really recommended for under 20' boats at all unless they are tiny.

[at100plus]

I'd like to hear John of Lightning Powerboats explanation of the tunnel extension. As far as I know he is the only one running them on the 21 Skater hulls right? John are you reading?

[TUFFboat]

I thought just for fun I would try to describe using a tab on a 24. Those that have been there can instantly relate, those who are inquiring can imagine...
Imagine if you would a group of equally equiped 24' skaters racing in a 3' lake chop. Everyone is trimmed in and thottles to the bar, your crossing the top 1/4 of the waves at around 85mph. Your not really in the water as much as rubbing the top of it. Its like doing a one handed hand stand on the peak of your roof in the wind with people throwing stones at you. Now there is an extremely competent guy 20' beside you with motors sreaming as well. So you reach over a finger width an call the tunnel tab into service, after trim adjustments are made its like your handstand on the roof has lifted up on to one finger nail, your flying high with no real contact. You look over and your pulling that guy by about 1/2 mph. but lap after lap it stretches into enough to do the job. You lived briefly on the very edge of life and got away with it. That makes a tunnel tab magic, it could have been the sword of disaster. choose your path carfully.

[jerry]

jerry thinks the best reason to use a tab is to stop the porpoising . you will get hurt if you use it going real fast . jerry knows that between about 50 to 70 mph where most people cruise at , it gets annoying to keep bouncing up and down , put a little tab in it and it will go away.

[mjwalters]

I am almost ready to install a tab on my 30ft motion . How is your tab mounted with reguards to height ? even with the bottom or up 1/2- 3/4''? :confused: Can antbody post a picture?

[jerry]

heres one jerry rigged

[jerry]

heres a better shot of my work

[sho305]

Hmmm....Jerry knows. Have to say, posting a pic of such a nice rig is just torture with that snow outside my window.:rolleyes:

[Kirk Dunteman]

Jerry, That looks like the same tab I have on my 24 Skater. What does Jerry know about turning the props in or out on the 28 and what speeds does she run?

Lonnie, how you been? Are you going to be at the race in Daytona? I'm supposed to be racing with High Risk for a few races but he's still not sure which ones. I hope to be at the alligator run again this march. Hope to see you!:cool:

[Liberator24]

Very clean!! I have looked at Dana Marine Monster Tabs and they are HUGE! I'm surprized that all you did was install 1/2 a set of (what looks like) Mercury K planes. I just assumed that the tunnel tab was more exotic. Is something as simple as this equally effective to the kind that cover the whole tunnel width? If so, my worries are over. All I need is something to take the hop out of midrange cruising. On the big end they don't porpoise anyway and it would just get tabbed down enough to quell the hop and it would be full up for the rest of the time. I assume the installation is even with the top of the tunnel and parallel to it in the full up position. My thanks to Jerry for putting a picture of the thing in the thread. As the saying goes, a picture is worth ...

Couldn't be truer in this instance!!

[Kirk Dunteman]

Woodco, was that 24 originally Rob Lafluer's Mobil One, or I think Sundance Marine? Then raced by Chip Fendt for a season? This is my 100th post! Its taken awhile to get here but worth the trip!

[jerry]

jerry likes to spin props outward , but everyone has there own opinion . the boat will run 112 on its best day .

[woodco]

Yes it was !!! Good memory ;)

[Racemore]

Where ya been? Don't know about Daytona but I'd like to.Won't make the Alligator.Bought a 23 Daytona and i'm trying to get it together by Memorial Day.When is the Daytona race might run down and check it out.Good to here from you,sea ya Lonnie:cool:

[LaserModVee]

Have you built a motor for that 23 Daytona yet?

If not, what are you thinking about and what speeds are you wanting to hit?

I just remembered showing you pics of that twin turboed 23 Daytona running in the 130s, but I forgot to show you pics of the other one that showed up the same day with a Paul Pfaff supercharged big block running 125 ish. I'll have to look around for the pics of that one.

Until then, here's the turboed Elim!!!

Those boats will run!!!!! <p> http://home.columbus.rr.com/a0000/private/turboelim.jpg http://home.columbus.rr.com/a0000/private/turboelimcloseup.jpg

[Racemore]

The boat is rigged for twins from a original single V-8.It has 1 offshore 2.4 LH cle with a 15x30 Spinelli.The power head isn't included at this point but thats the direction I'm going.I'd put 3 280s on it if I could.:D With Nitros:eek: Don't know how fast that would be with 34's.

I'll be happy to get a pair of 2.4's doin close to a buck going across Lake George heading to Siver Glen.Real happy!!:cool:

I do have an Arneson drive on the back porch and a United Racing Small block chevy,the thought has occured.That boat in the pic is a later model than mine,it has a flat deck and round windsheild.I thought it was a 24.Mine is an 88.it's registered as a cabin cruiser. :)

[mjwalters]

Jerry How does that small tab work? . I am installing one the width of the tunnel around 40'' or so. Dana makes a single tab That is fairily wide 24'' or so. Thanks for the pictures
michael

[Joe L.]

Im glad to here Jerry knows so much about my boat, for the record TNT Marine rigged the Skater, 28 Skaters or at least my boat does not porpoise in the speed range he talks about. The tab works fine at all speeds, but I seldom use it.
This guy Jerry is so full of s--- he makes this board smell...............



Joe L.

[Kirk Dunteman]

sswweeett boat Lonnie. The race in Daytona is April 12,13. I've been super busy between working at the Lake and my own stuff, now the kids have t-ball and so on and so on.......I was hoping to make the Radical reunion but now I have a friends wedding to go to and the wife said i can't miss it. Sometimes they just don't understand.

Woodco, you need to bring that nice Skater down south and play!

[TUFFboat]

I was just reminiscing about the old days earlier, I remember some good times with you and Joe, both Eastern and Skater Express, and all the guys, best fun ever. I heard your still playin around. Do any of these guys know who you are? Hope your doing well, and your folks too.
MW

[JOLLEY]

I remember the white Eastern Express Cat, back when I was crew/go'ffer/glassfixer for team Peppers D-class Cat, twin chief big blocks, at Keonig's (sp) warehouses on 21 mile by Jefferson/ I-94. Haven't seen Humes (Peppers/Exide) or the boys in 10 years. Geeze that has to have been the late 80's (it's still a little bleery!!) Good Luck Kirk, and the rest of the racers this year... Kirk, Jim Merten says 'Hello'. Good Luck Agitator, Woodco, Racemore !!!!!!!!

[TUFFboat]

Now Im wondering if your Express is the old "PUSH IT"? Peppers brings back memories as well, What was his undefeated "B" boat called? What a great division six was.

[JOLLEY]

Small World 'Eh, Good to here from old friends.... I'm sure we'll get a group together for the Silver Cup races..... Got to look up some of the 'OLD' boys. I'll be in touch, Bill:D ;) 'PUSH IT'... I remember it , not sure, but I'll find my boats heritage sooner or later.............. 'Come ON Summer'.......... 6-10 inches of snow predicted for tommorrow. Got Gas at lunch for the sled. HE-HE-HE :o :p :rolleyes:

[Liberator24]

Hey team, I put a tunnel tab on and IT"S INCREDIBLE. Boat will lay down and run flat no matter what the conditions. Just use a little cause it doesn't take much and if you don't keep the bow flyin' you could stuff it, but this is the answer to the porpoise question, no doubt.

[Racemore]

Glad to hear it's working for you.It's getting hot down here.:cool:

[Kirk Dunteman]

Hey leberator 24. Just out of curiousity, which tab did you go with?

[mjwalters]

Hey Kirk I am thinking about a set of dana billet tabs with a 1/4" alu plate connecting the two running one pump. Dana does make a 40" tunnel tab but the damm thing cost $5300 . a set of there 20" tabs is $1800 to much difference in price for me. tunnel width on my 30' motion is 42":eek:

[WILDMAN]

The tab Liberator24 used is a Dana 18"x28" Single ram,$2200. PURPLE!

[Kirk Dunteman]

Thats a good looking tab, I need to replace the one on my Skater. That looks like a nice heavy duty ram. Thanks for the input guys. Kirk

[mjwalters]

Just completed my tunnel tab for my motion30' Started with a dana hp1000 Off to the power coater next

[mjwalters]

another picture

[LPB]

We here at LIGHTNING POWER BOATS are big belevers in tunnel Extensions,not tunnel Tabs,on Larger cats with deep tunnels tunnel tabs work very well and are pretty safe,while up and running they only compress the air and don't ride on the water,on the smaller cats such as my 21' and 24' LIGHTNINGS (skater copys)the tunnels are much shallower,and when you put the tab down,you can get alot of bucking ,and you who'nt see much help out of it on the top side,but with a tunnel Extension you are extending your lifting capablitys,with out the drag of longer sponsons,simple put its like having a 24' tunnel on a 21' boat,more lift for the whole boat,makes for less drag which hopefully makes you go faster!!I don't claim to be the Expert here but we have been testing tunnel tabs and tunnel Extensions for about 10 years and I think most cats should have them,I can asure you that 99% of all new LIGHTNING cats will have one,with all this said theres not one thing thats makes a big diffence,but alot of little things will make a huge difference!!!to all you boaters out there with small cats and tunnel tabs ,be very easy while triming your tab John

[mjwalters]

John thanks for your reply. Your experience is invaluable. My boat is a 30' motion with a 44'' wide tunnel. I am trying to eliminate the midrange propise. It is an outboard boat with twin 300pms Whats is your opinion?
Thanks Michael

[LPB]

Your boat has a very wide tunnel,the bad news is it dose not have alot of compression,I would put a 30to36" tunnel extention,start with the 36" and you can Allways cut it back,I just put a 30" on one of my 30' cats,I would of put a 36" ,but the boat is going to ST Thomas,and the guy who's getting it has no experience in a cat,when you make it to long it can trip you up in the real rough stuff,If you have a go feel for the boat and alot of seat time,run the 36",your boat normaly takes alot of trim,you will find that you who'nt need as much,feel free to call me any time,you don't have to own a LIGHTNING,to get my advice,941-365-2584 John Christensen Good luck with your boat!!

[espen]

I saw the offshore racing fleet of Victory Marine in Dubai run by Americans off course:-).....
28 Skaters with not far from 30inch tunnel extesions...just flat
out from the tunnel roof and no ajustments to it. In europe its popular with a rubber flip on the transom to ajust the air flow trou the tunnel ,ajusted from the drivers seat.
Espen

[mjwalters]

LPB thank you for your reply. Your offer of advice is very generous. I will be speaking to you.
Michael:)

[JOLLEY]

There is a new virus: code name is "work". If you receive "work",
from your colleagues, your boss, via e-mail or any where else, do
not touch "work" under any circumstances!! This virus wipes out
your private life completely. If you should come into contact
with this virus, put on your jacket and take
two good friends and go straight to the nearest pub. Order three
beers and after repeating 14 times, you will find that "work "
has been completely deleted from your brain.

Forward this warning immediately to at least 5 friends.

Should you realize that you do not have 5 friends, this means
that you are already infected by this virus and "work" already
controls your whole life. This virus is deadly. Please pay close
attention to it and take heed.......................... :D

Tunnel Tab project finished ,pix to follow, Cad file shows how it began, changed it a little, I'll post pix asap

[JOLLEY]

another

[JOLLEY]

more

[JOLLEY]

last

[mjwalters]

Jolley What are you using for hyd. cylinders? How much stroke do they have? Have you mounted your tab yet? Level with the tunnel or up a 1/2''-3/4''?
Yea this work stuff sucks! At least that is what I have heard. I try to stay away from it.
Michael

[JOLLEY]

Not installed yet, using I/O trim rams, with shortened throw, merc trim pump. 30deg up, 25deg dn. mounting equal with the tunnel roof (although it has a slight V to it on the OceanExpress hull, so it will be about 2" up from the center) I'll post pix soon.

[Liberator25]

I run a Dana Monster Tab on my Liberator (24 ft) and have had very good experiences with it. Mine is 18" wide and 30" long. I have a tab indicator so I know where it is at all times. My boat has twin 300X motors and likes the engine trim just a little positive (maybe 1/2 - 1 mark on the trim indicator). The boat runs fastest with the nose up just a little, too flat isn't fast and too high scares the crap out me 'cause the boat will kite when I hit rollers or medium size wakes. When the hull attitude is "right" the boat will fly flat when it leaves the water and land flat and soft. I use the tab to control the nose of the boat instead of engine trim because it is more effective and works faster. The other side benefit is that I get the two engines set right (both set at the running trim setting, balanced and symetrical and basically forget 'em) and only have to "deal" with the tab setting when adjusting the hull attitude. Less to do when going fast is better and makes the boat much more instinctive. When taking off from a stop or when trying to get on plane while traveling at displacement speeds, I tab full down and it rolls the boat over on top QUICKER than it ever did using "trim in" on the motors with no tab. As soon as it does start to roll over I just hit the up stick on the tab to bring it to a neutral position (parallel to the bottom of the tunnel roof). That's where I leave it 95% of the time. If the boat ever starts to porpoise, I just TAP the tab down and it goes away immediately - really amazing. This porpoise thing usually starts around 55 or 60 (my preferred cruising speed). The down position is so slightly less than the neural position that there is very little "stuff it" danger. Once the boat gets above 80 or 85 I tab up to neutral because the porpoise is gone and the boat runs flat cause there is plenty of air packed to keep it flyin'. So there you have it, the tab helps on take off, smooths out the midrange porpoise and is no more likely to stuff than a non tab boat on the big end. I never tried to use the tab down lever to increase speed (which increases the stuff %) so I can't say if that would work or not. The use of the tab is very subtle, SMALL adjustment down fixes the porpoise and SMALL adjustment up returns it to neutral which effectively lengthens the tunnel and gives a little additional lift with no "stuff danger". The only time the tab gets a long stroke is on take off to roll the boat over on top and that's it. Everything else is maybe 1" up or down. In my opinion an adjustable tab is better than an extention for the control. It's just that if the control isn't used judiciously it can get you into trouble. Steering wheels are like that too, at speed use them judiciously. Anyhow, that's my 2 cents worth.:cool:

[WILDMAN]

Lib25, I just put one on my 24 Liberator this week. It's a 14x18 K-plane, and it takes care of the porpoise problem fine. When are you gonna get those 34" props on there? What have you run and at what rpm with the 30's?

[mjwalters]

Liberator 25 Thanks for the heads up . My 30' motion with twin 300s porpises at about the same speed as your boat. My tab is now at the powder coater hopefully install this week. What speed do you get out of your 25' liberator? how many rpms do you turn those 30'' props? I run 34'' 3 blade on mine but my limiters kick in at 6200rpm.

[Liberator25]

Motors are SLOWLY loosening up. Right one is ready to rock, left one still not there yet. I noticed this last weekend when my rpm difference became nearly 1000 rpm between the motors with identical throttle settings. I have an In Control split pedal so I was able to adjust while running. I have tighted up the throttle cable on the Lefty and loosened the Righty to try to even them out in the midrange but there is still about 300 rpm difference. This will fix itself in time I hope. My current props are 15"X30" 4 blade merc cleavers and with both motors turning 6700 rpm the GPS reads 101 mph (that's about 14% slip by my calculation). I return boat to Dave in a couple of weeks for some "stuff" (since I have hull mounted low water pickups, I think we may raise the motors another 3/4 to 1 inch, currently the propshaft is at 1 1/4" above the bottom) and the 34's go on then. These new props are 15"X34" 4 blades, but they are lab finished. I figure when the motors are fully loosened up (I've got about 30 hours on them now) and with the lab finished props, I should be in the high teens. The lab props should reduce my slip to around 10% (hopefully). Merc racing prop guru Dennis Cavanaugh seems to think the 34's may not be enough to keep the motors off the rev limiters, but so far I haven't hit them with the 30's. On the X motors the limiter is set at 7100 rpm. IF I can pull 6800 rpm with the 34's AND the slip is reduced to 10%, then the boat should run 121-124. Those are big assumptions, so I'm thinking high teens is more realistic. We shall see and I'll let you know.

Additional suggestions for mjwalters. Sounds like you have the ProMax 300's (not the X motors). If you are already on the limiters then the three blades aren't your ticket. Three blades will normally allow the motors to turn higher rpms (slightly more slip than a 4 blade) and this usually results in increased speed over the same prop in a 4 blade. If you were to increase your diameter (don't know what yours is but this is a prop increase thing and you need more prop to get off the limiters) and go to a 4 blade you should pick up more speed. Right now with the motors laying on the limiters you're leaving some on the table. Just some "theory" for you to consider.:cool:

[Kirk Dunteman]

I'm not understanding how your going to come up with 20 more mph. If you raise your motors higher, I wouldn't be suprised if your slip goes up. Also where are your water pickups located? They could be blowing out your prop some. Dennis is a great prop man, but I can't see more than an extra couple MPH. It must be some special stuff? Let us know how it works out.

[mjwalters]

Liberator You are right I do have reg 300s. My motor height is also 1 3/4'' above the bottom with the standard sportmaster water pickups. My acceleration is poor at low speed so I don't really want more prop. I do have a couple of other sets to try, If the rain here ever stops. My best speed to date is just over109mph on gps. I did swap the lower units side for side, seems to provide more bow lift but I don't have enought time on it to tell if this is the way to go.
300rpm difference is not unusual but maybe they will even out. I thought the revlimiters on the xs was 6700. Good luck with your set up and let us know how it works out.
Michael

[Liberator25]

Kirk, Props aren't the only thing that's changeing, as I said the motors are still loosening up. They seem to be around 90% or so now. When they are up to full power and the props are changed and the motors up higher all this might well be worth 20 mph. The computer on these motors decides when their broken in, not me, so until that happens it's just a wait and see deal. Cavanaugh knows the hull and the motors and the setup and he's pretty convinced that we're going to need to tweak the props to keep it in the 300 x's "desireable" max of 6800 even though the rev limiter is 7100. Since these motors have oil injection (not premix) he does not want the motors turning over 6800. So while all this theory is possible, the proof is in the pudding as they say. Right now I'm just trying to hour up the motors to get them out of breakin mode. I'll let you know what happens (or doesn't happen). I can live with a 100 mph boat so there will be no big disappointments.

[Kirk Dunteman]

Hey Michael, If your hitting 109 with pro max's your doing pretty well. There is a 30 with new 300x's down here thats pretty well hooked up and I think the best he's seen is around 112.

Liberator 25, Damn computers not letting you open it up yet after 30 hours. I remember when you had to rebuild the motors after 30 hours.:D I do like that tab you run. Sounds sweet compared to my little 300C.

[mjwalters]

Kirk Yea I think my boat does run well. I have not had it on a scale but it is light, kevlar and foam construction. Twin full canopies 4 sparco seats. not much else.It does take a lot of trim to make it go. It will fun 104-106 any day with 4 people and fuel. I am eager to try some new props I have bought. Currently running 15x34 3bl labs tuned this winter by Matt at throttle up.: We will see if that helps. We have had 10 straight weekends of rain here in the north east. If this keeps up I going to have to start building an ark.:mad: Did you put new motors on your skate?

[Kirk Dunteman]

Mike, I remember seeing the pics of your boat and talking to you about its setup before. I'm interested in hearing how your throttle up props run. They did some for Critical lift race team,a 36 skater with trip 280's, but I never got a chance to run them while I was on the team. They seem like they know what they're doing though. I've been making my Skater a long term project with putting together Offshore mids with sportmaster cases and my old powerheads tuned up. Just got my new tunnel tab in this week. Now I'm just waiting on a couple of flywheels and I should be ready to finish it up.:rolleyes: Kirk

[mjwalters]

Kirk It has been raining here forever. When I get to run my boat I will let you know about the props. I am also currently installing my tunnel tab, it came back from the powder coater this morning. Good luck with your project
Michael

[mjwalters]

Got the tab together and installed. I need to finish hooking up the switch and hopefully test run tomorrow

[mjwalters]

more

[mjwalters]

last

[at100plus]

I posted earlier in this thread, before I had any hours in my boat with the 300.

With the 2.5, there wasn't really enough power to get out of the porpoise because 80 was about the top speed.

The 300 is a different story. It has more power, better acceleration, therefore it powers out of the porpoise zone (in the 50s) faster. In choppy water it's almost non existent. I just don't go 55 for long that's all.

I love this boat!

It would be interesting to see what a 300 powered 21 does with a tunnel extension though.

[mjwalters]

Mike the porpise zone in my motion is around 65mpn to 80mph right where I like to cruise. most days the bay is to rough to run over 65mph hence the tunnel tab:D

[Liberator25]

I was wondering how the tab worked out for you. Mine was incredible. Just can't believe how much better the boat is with one and how much more enjoyable it is. I'm sure you too are somewhat amazed at how the thing works. These should be "standard" on every twin set up. Just remember to keep the nose up enough to handle chop, rollers, wakes, etc. and when turning. Too much down tab and the stuff thing begins to play in the mix, particularly at speed. Once you crank thru the porpoise zone, just neutral the tab and let 'er rip. You'll like it!!

[Kirk Dunteman]

Liberator 25 I want to hear how your boats running. If you need help breaking them in I'm available.:D Also is your boat a 24 skater copy? And if so, do you know the weight of the boat with the 300x's? Just curious because I have a 24 skater and was wondering weight differnces:confused: Kirk


Hey at 100plus, I viewed your photo album, nice pics of the boat, bezels, and wiring, and so on, but not a single pic of a girl in a bikini in it.:( If it warms up up there see if you could remedy that.

[mjwalters]

Liberator25 I never got my boat off the trailer. The weather here has been terrible. Maybe early this week. I will let you know when I get wet.:mad:




Kirk did you say breaking them or breaking them in?

[Liberator25]

My boat is Skater copy- 24 foot. The seating is moved forward about 18" or so and so the balance point is a little different. The bare hull is 1450 lbs, I think that's a little lighter than a 24 Skater. My boat turns 6300 rpm on a hot day and in the cool mornings (70 degrees) it'll turn 6500. At those rpms (6500) and with 15x30 4 blade merc cleavers, the GPS is reading 100.3. We're going to work on the setup this week and change the props to 15x34 4 blade merc labs. We are also going to put a DDT on it to read the computer to see if we're still in breakin and for how much longer. As this project continues, I'll update "what's happening".

[Mark75H]

About 1961:

[mjwalters]

Liberator 25 15x34 4blades sure seems like a lot of prop. 3blades will most likely be a little faster. I aquried a set of 15 3/4'' x34 3blades but have yet to try them. I was thinking I can always have them cut down if needed. have a couple of sets of 32'' 3 and 4 blades I am going to try also. One thing we all know about props... you don't know how they will work till you put them on the boat. Good luck with your testing. Let us know how it goes. The 300xs should make some real good power.
Michael

[mjwalters]

Mark 75 I love that picture

[JOLLEY]

;)

[JOLLEY]

:)

[mjwalters]

Jolly Nice work your tab looks great. How does the hinge`attach?Is it welded? Lets get those motors on and go.:cool:

[JOLLEY]

Yes welded opposite/opposite on the plates with a stainless rod thru the clearance holes.

[Liberator25]

Michael,

Based on what I've experienced with the 15x30 4 blades, I would agree that the 34's sound too strong, But ... in two Hot Boat magazines a DCB 26 with two 300x motors (different boats, not the same boat twice) ran 107 @ 6400 rpms with 15x34 merc lab 4 blades. Based on this, I felt the hull I was running was faster and had less drag and was lighter than the DCB 26, so my expectation was that the same props, same motors, faster - lighter hull, should turn motors up at least to 6400 and maybe more like 6800. This was confirmed with discussions with Dennis Cavanaugh and so that's why I went this route. The four blades are a little slower than 3 blades, but smoother and that's a fair trade off for me. I'll just have to wait 'till we get the computer and rigging sorted out to see the outcome. I do feel the boat should pull 6800 with the 34's (based on the real world DCB 26 tests). This is unless something is not "right" with the motors or the setup. So we're workin' on these two things this week. Should have some results to report next week after a weekend on the lake. Merc technical guys have suggested the motors are only at 90% "for some reason". This is based on my rpm's of 6300 which is 90% of 7000 (the rev limiter), and their conviction that the motors should pull the rev limiter with this hull. Very interesting stuff!! Of course, the only thing that counts is "how fast will it go", not "how fast is it supposed to go" - Don't ya just hate that!!

[mjwalters]

Liberator25 My 300 promaxs will pull 15x34'' three blades to the rev limeters but they kick in at 6200 rpm. On an average day that is 104-106mph when they are in a good mood top speed is over 109mph. Ran today with 14.5x32'' 4blades. Ran about 102 hard on the limiters with throttle to go, but much better accelaration.
The trim tab I installed works well stops porpoise at cruise speed. Also worth maybe 1-2mph on top end can really feel the boat lift. Just for kicks I will try the 15 3/4 x34'' three blades. Let you know what happens


Ok I did run the 15 3/4''x34 3blade lab cleavers. As expected slow accelaration but cruise speed is 67mph at 4000rpm. Top was 102.8 at only 5800rpm. the tunnel tab did not help top speed with these props. Must already have enough transom lift. I guess I will send these props to Throttle Up in Fla. to be cut down.:p

[fullthrottledps]

what brand is that tab how much was it? and whats thier phone # also I need some other makers and #'s .If any one could plese help..thx Dan

[JOLLEY]

Mine are home made., try ProRoc marine (Papke Tabs), Dana marine products (monster tab), Arneson.:D

[Liberator25]

There are several who feel strongly that you should NOT use a tunnel tab. I know that the use of tabs is a fairly recent development and that SKATER never put one on the early 24's. How do you get thru the porpoise? Negative trim until you get around 90 or so then gradually trim it out? I was wondering about the technique, because the porpoise thing is REALLY ANNOYING so there must be some acceptable workaroud. Whatcha think??? Tell me the secret!!:confused:

[mjwalters]

Liberator 25 After getting more seat time in my motion with the tab installed, my rig feels like a different boat. Ran in some pretty rough water the other day, man with the tab down it felt like an inboard boat. The tab makes a huge differience in the big water in this boat. I would not run with out a tab now. Never felt as though the boat would do anything stupid. But again my boat is 30' How is your rig running? Did you get your prop deal figured out?:p

[Racemore]

You are going to porpoise without the tab but you can stop it with the throttles.You have to chop the throttle and get back on it as it starts to go up on the 2nd or 3rd bounce.It's a timing thing you'll have to practice and get the feel of.Like chine walking you are countering the movement of the boat.It will still porpoise at a certain speed but it will narrow it down within a couple of mph if you can control it.The tab just holds the boat down and it is comfort not speed.I wouldn't use it racing in the ocean because it can cause more problems than it's worth.Just my opinion:) :cool:

[at100plus]

Another way to get out of the porpoise earlier, is to turn right and then back left again as you accelerate through the 50s and 60s. This disturbes the air going through the tunnel and when you reach the high 60s (at least on my 21 ft) the porpoise is gone. When it's rough, mine hardly porpoises at all.

[Liberator25]

I appreciate your input. I'll try the two techniques suggested by Racemore and at100plus. Learning all the "tricks" is what owning one of these tunnels is all about, and what makes it so much fun.

By the way, since the tab holds the nose down, do you suppose the same "effect" be achieved with engine trim? Theoretically, at the onset of the "porpoise zone", you could run a little negative trim into the equation (in place of the tab down) until you get past the porpoise speed and then gradually pull the negative trim out of it and air it out. Since this is only theory, I was wondering if anyone has tried this technique.

Michael, my prop saga continues. I currently have the 15x34 4 blades on the boat. Full fuel, passenger and all my "stuff" the boat runs 105 easily and routinely. I suppose I could empty out the boat and run with a light fuel load and leave the wife on the dock and pick up 5 mph or so. I do know that the 105 number (@ 6300 rpms) is in 95 - 100 degree Texas heat and that will slow you down a lot. I got out one morning early in the season when the air temp was about 65 and the boat pulled much harder and turned 6800 rpms, but I only had the 15x30 4 blades on then. Actually I need a recall on my GPS speedo, cause a quick glance doesn't really get it. It is interesting that the boat doesn't seem to lose rpms when you change from 30 to 34 props. That much of pitch change should be a difference of 800 rpms or so and I just don't see that much difference (MAYBE 200 rpms). The computers on these things seem to adjust. I have never seen 7000 rpms - where the limiters are the X motors - even with the 30's.

[WILDMAN]

Ron, your motors are probably too high. The red 24 I sold to Jim5656 runs 105 at 6000 rpm with the same props. Thats with full fuel and 4 people. Running in a big arc up through the porpoise zone can help you get past it. No matter what you do, if it's flat water, it's gonna hop. Gotta have that tab. The more weight in the boat, the worse it'll be.

[Liberator25]

Just out of curiosity, This picture of Jim's boat has much more positive trim than I run. I tend to run the boat with neutral, or just slightly positive trim. This picture, based on the way those motors are tilted (and the rooster tail following it) seems to have a lot of positive trim. Are you just "playing" in this pic or is the boat running at top speed? Still shots never do things justice. Maybe I'm not running enough trim to really get the thing flying. I guess the fear of blowover keeps me from getting too aggressive with the "up" lever. This is my first tunnel and I have about 60 hours of total tunnel seat time. I feel much more comfortable now than in the begining but certain things still bother me, like outside lean in slow sharp turns (very weird) and too much nose up at speed. I think I tend to be pretty conservative on the trim. I am going to lower the motors back down while I get my Tab fixed. Did you decide to sell me one of yours?:cool:

[WILDMAN]

Ron, I was just playing around with roostertails there. Here's a pic at top speed.

[mjwalters]

Liberator25
If you can run 105mph with those conditions I am sure you will pick up at least 5mph maybe as much as 10mph in ideal conditions with a light load I do have a recall on my gps,and yes sometimes the I see higher speeds with recall then I did while I am driving. A lot of things to keep an eye on .

[at100plus]

Ron,

In my 21, I haven't found trim to make much difference for getting through the porpoise zone. I run from neutral to slighly positive all the time, and the only time I find it really changes anything is when you are going for that last MPH on the top, and when you are going against the wind.

When going for a top speed number, I get that last MPH with jack and trim height, and you feel a bit on edge like it's flying high or going to blow over. It's probably not as likely as it feels.

When I'm going against the wind, I tuck it down to neutral or just below because the wind is giving you the lift to substitute for the trim.

I don't know of anyone that has blown over a Skater type cat. I'm sure it's possible but is it common? Anyone know someone who has? Mostly I hear barrel roll horror stories, and stuffs. I was in some really snotty water last weekend and my left fork stuck a wave a bit. Just barely caught it but that slowed me down.

Regarding the outside lean. I have found if I keep the trim up and keep air in the tunnel (this is about 35 to 40 MPH in my boat), I can turn pretty well without lean. It does feel like it's sliding and or propwalking, but it actually turns pretty good. I only do this in calm water.

[Kirk Dunteman]

MY 24 SKATER WAS BOB ERICKSONS PLEASURE BOAT. THROTTLED BY THE LATE GREAT HURLEY STEPP. HE HAD TUNNEL TABS ON BOTH RACE AND PLEASURE BOATS AND WON MANY CHAMPIONSHIPS IN THE MID 80'S. I TORE THE TAB OFF RACING LAST YEAR AND REPLACED IT WITH ANOTHER LIKE IT, A MERCURY 300C. I THINK THE BIGGER TABS WOULD BE BETTER IN THE CALM BUT NOT OFFSHORE.
LIBERATOR 25- HAVE YOU EVER TRIED 3 BLADE PROPS? HOW HIGH ARE YOU RUNNING, WHATS YOUR X DIMENSION? YOU SHOULD BRING THAT BOAT TO LAKE X ONE DAY AND YOU CAN TRY THEIR PROP SELECTION AND MESS WITH HEIGHTS AND MAYBE GET IT DIALED IN BETTER THAN YOU ARE. YOU SHOULD BE RUNNING THE SPEEDS YOU WERE SPEAKING OF EARLIER. IF YOU NEED PHONE NUMBERS AND WHO TO CONTACT LET ME KNOW, I WORK THERE.

[Kirk Dunteman]

WHY ON A SUNDAY MORNING EVERYONE IS ONLINE INSTEAD OF BOATING OR SOMETHING ELSE? THERE ARE SOME REAL SICK PEOPLE OUT THERE IN BOATING WORLD:) :rolleyes: :cool:

[Liberator25]

Mike,

I have watched your posts from the beginning (while you working out the issues with your new motor) and you seem like a really good guy. I know you are having a ball with your boat. I also took a look at your video. VERY COOL!! I don't know how to add music to a video but that was a very nice job. Thanks for taking the time to share your input. It's good to have solid guys to talk to.

Michael - Ditto on the solid guys deal. I appreciate your experiences and your willingness to share them. I am still in the learning mode as you can tell.

Randy - I'm envious of the rigging you do. I can only imagine how good it is but everybody has the same story so it must be something special. At any rate you are a great resource and valued advisor. Your experience with the Liberator product and specifically with the 24 CAT is very important to me.

Thanks for all the info. I'm going to continue with the tab thing and try to be a LITTLE more bold with the up trim.

[Liberator25]

I, too, just lost my tab. It was a DANA monster tab and too long for the flogging (30"). I think the leverage just got to it. This should not have happened, but it did. I will be replacing it with a smaller one that should have about the same effect but will live under normal weekend lake conditions which are usually choppy. Probably an Eddie Marine unit. I'm disappointed that the thing didn't stay together (considering what it cost), but lesson learned. It's funny that I seem to have to PAY for all lessons, I guess life is like that.

Regarding my X dimensions and props. I have never tried a three blade but I will soon. Some debate on HOW to measure the X dimension on a CAT, but from the bottom point (the point where the bottom of the sponson joins the vertical wall of the tunnel) of the sponson to the tip of the bullet on the gearcase (with the engines trimmed to neutral) I measure 3". But the gearcase doesn't point to a spot just above that tip. It points to spot that is a few inches outside that point. The gearcase tip is 2" above the bottom of the sponson that is DIRECTLY in front of the gearcase. I don't really know which is the correct way to measure. I assume the gearcase has no idea where the bottom of the sponson tip is so the only dimension that matters is the bottom of the sponson DIRECTLY in front of the gearcase. If this is true then my X dimension is 2". My motors are mounted directly to the transom, so I can only adjust one hole at a time and each hole is 1/2". I used to run the motors one hole lower (@ 1 1/2") and the boat felt good. Now with them up one hole to 2", it feels looser, won't steer on the top end and occassional loss of water pressure (2 or 3 times a day) happens, normally in high speed turns. I think the boat is telling me to lower the motors!!:D

[WILDMAN]

Ron, put the motors back to 1 1/2 inch above the bottom.

[mjwalters]

Kirk I was going to go out today. But I was going over my rig and found the propshaft seals leaving the carrier. Looked a little closer bearing carrier is cracked from the propshaft bearing to the seal area. I thought the sportmaster cases would be bettet then they are . In the last 2 seasons I cracked 2 bearing carriers and 1 gear case housing. What can you do, thats boating.




Liberator on my setup I run the lowers 1 7/8'' above the bottom. Higher then that water pressure is unreliable. Thats is with a 10'' transom notch ans a 5'' setback
What broke on the Dana tabs? Dana did not offer any help? He seems like a good guy.

[Racemore]

You guys are tearing tunnel tabs off? Thats because it's a training wheel.And you know there are places training wheels don't work well,like going over bumps.Things come to fast when your running hard in rough water and even more if the 2 ft chop is on 4 ft swells.I like have the least resistance if I land off the wave with alot of angle.I like to run at the same angle the boat would run trimed out in good water and it's easier when your pleasure riding but if your running fast enough to win for an hour throttling over 1000 waves (right hand goes numb from lap 3 to 5)you'll find alot times you don't want help getting the nose down.I see more use on the bigger boats.Im sure that a smaller tab would be the best of both conditions.:cool:

[JOLLEY]

I still love mine, it works, used appropriately ( alot of responsibility ).............................:D :D

[Vicious]

Bill, How is she flying? That awsome with the 415 mpi at the shop that has the rods hanging out of it, We are going to start converting it over to a outboard model we will probably need one of your custom boarding platforms for it!! Seeing it came from the old Redline hull which came from your hull with some slight mods to it! Spark

[Liberator25]

I heard two distinct loud noises. The first was when the screws at the hinge let go and let the front end of the tab go - heard a bang as it flailed away from the hinge. All that was holding it on at this point was the hydraulic cylinder. When the tab got hit by my right prop (the second bang) I felt it in the motor, I thought I had hit something submerged. The two bangs were 1-2 seconds apart. I slowed down immediately and looked at the tab indicator, it was pegged. My wife looked over the transom and told me the tab wasn't there. My first impression was that the hydraulic cylinder had let loose and the tab was just hanging straight down. I could see the upper cylinder attachment was broken. When I got it out of the water was when I realized what had happened. Of the seven screws that held the tab to the hinge, the left most screw was missing like it had backed out, the next one in from the left was stripped like it got pulled out, the remaining 5 were all sheared. That's why I'm sure of what happened first. The prop hitting the tab that was still attached to the boat by the hydraulic cylinder cause the tab to kicked hard left (my right motor prop hit the tab) and this is what fractured the hydraulic cylinder mounting bracket. When that broke the whole thing left and is at the bottom of Canyon Lake. Here's a pic of what's left.

[Kirk Dunteman]

THE CORRECT WAY TO MEASURE IS DIRECTLY IN FRONT OF THE CASE. I RUN MY MOTORS A 1 1/2 ABOVE. ALSO IF THE BOAT ISN'T FEELING "RIGHT", IT PROBABLY ISN'T. ALWAYS FEEL SAFE.....
O.K. SOMEWHAT SAFE. WHILE I DON'T KNOW ANYONE PERSONALLY WHO HAS BLOWN OVER A 24, I HAVE HEARD STORIES THAT ITS POSSILBLE. SO WATCH YOUR TRIM. LOWERING THE MOTORS DOWN WILL DECREASE YOUR SLIP AND INCREASE YOUR LEVERAGE WHILE TRIMMING OUT. TRY SOME 3 BLADERS. THIS SHOULD GEET YOUR RPM'S UP WITH LESS DRAG. IF YOU WANT TO BRING IT TO THE LAKE SOMEDAY, LET ME KNOW.

MICHEAL, BUMMER ABOUT YOUR CASE. ITS NICE TO BE BOATING ON SUNDAY, BUT FOR ME I HAVE TO RUN BOATS ALL WEEK LONG FOR MERCURY THAT THE LAST THING I LIKE TO DO ON THE WEEKEND IS GO OUT IN THE HEAT AND GO BOATING. SO INSTEAD I GET ONLINE AND READ ABOUT BOATING. I EVEN HAVE MY BOSS JOHN SHERLOCK ON SCREAM AND FLY NOW. SICK, SICK, SICK.

[Racemore]

...I have to run boats all week long for Mercury... Quit whinning.:rolleyes: The boss is watching now.:D :cool:

[mjwalters]

Liberator I am suprised where your tab broke. I wonder if the bolts were loose. I know Dana assembles them with locktite I would hope he would help you out some. Have you talked to him?
What do you plan to do now?



Kirk Tough job!:cool: How does it work if one wants to take their boat to the lake for tuning? What are the charges who does the testing?

[JOLLEY]

You got it Spark. I have an extra pivot rod s.s. and all the templates. I really swear by it, we can slow way down with a full boat for cruising by the sand bars etc. plus really stabilize the mid range, at the sweet spot the tab is about 2" down from the tunnell roof to be functional, and that is at 20" aft of the transom !!!!!!!!I'll be by one of these days and drop off the parts and bits. Sorry Liberator about your tab, maybe larger grade 10 fasteners(airplane stuff) It's probably better it flew off or it would have beat both your drives senseless !!!!!!!!!!! Hope you get it squared away.;)

[Liberator25]

Here's a little more to the story. The tab also bent the tie bar between the engines UP about 1/4" so that had to be replaced also (not willing to risk any internal fractures that might have occurred). I guess that happened with all the flopping around of the tab before the cylinder ears broke off and the whole thing left.

Talked with Dana and he is going to make it right. I have to give him credit, he stepped up. At his suggestion I'm moving up to a 32" Monster Tab (two hydraulic cylinders and they are attached much closer to the trailing edge of the tab so there will be less leverage on the screws at the hinge. He feels this is a MUCH stronger unit and will not cause me any further trouble. Gave me a screamin' deal on the new tab so I just couldn't ask for better. Will post pics and tell you how it all worked out. Oh by the way, the motors are going back down to 1 1/2" above the bottom. More to come as the saga continues. Here's a pic of the new tab before powder coating.

[TUFFboat]

Hey Kirk
You do know someone that blew over in a 24, Gary Rotunto in Scaredy Cat. It was in the break wall in a Buffalo race. Although it was not a classic over the top it still blew of the water.
And Gary had and used a tunnel tab. In fact he was one of the first people to use it properly and agressively.
MW

[Liberator25]

I saw the pics of your tab, well done!! The way your hyd cyl attach at the trailing edge of the tab is a good (strong) way to do it. Mine (a single cyl) was only about 2/3 of the way back to the trailing edge. The new tab will be 32" wide at the hinge, tapering to 21" at the trailing edge and 30" long front to back. Made of 1/2" billet. This one is supposed to be King Kong so it should stay on. I understand why you like yours, it really makes the boat fun and gets rid of all the "bad" stuff while letting you keep all the "good" stuff. I should be back on the lake by Saturday.:D :D :cool:

[fullthrottledps]

nice tabn liberator 25 let us know how it works andhow much

[Liberator25]

This is new tab. Two cylinders move 1/2 as fast as one cylinder on the same pump, but only need a LITTLE tab, whereas before I needed more. This is a BIG improvement (no pun intended on the Big part). Porpoise doesn't start until 80 now and is all over by 90. Just a bit of down makes it go away and with this new deal, it is seldom needed. I lowered the motors back to 1 1/2" above the bottom and the boat is MUCH BETTER. Almost feels too hooked up because I was getting used to the other way. A little more trim than ususal to get the nose up and flying and less tab to control the hop and nose. All in all an improvement and I like it a lot better. It feels much safer and it's now FUN to run over 100 again, YEA!!! Here's a couple of pics of the new tab on the boat. Saturday was a good day:D :D

[Liberator25]

Here's another

[Liberator25]

This thing is a stud muffin~~ Those Hyd Cylinders are AWSOME. This whole piece looks like it's cut from a single piece of metal. Dana really builds some Good Lookin' Stuff (really $$$ though). If it lasts like it looks, it will have the life span of U 235!! This looks to be one strong tab:cool:

[mjwalters]

Liberator25 Looks good I am glad Dana hooked you up. Is the hinge the same on this new tab as the hinge on your previous tab?:

[Liberator25]

The new tab has the same design hinge as the old one. The differences in the two tabs are:
1. Size - new is 32" wide tapering down to 21" at the trailing edge and the old one was 18" wide with no taper. They are both 30" long (front to back). This size has a much bigger and stronger hinge with more attaching bolts (9 vs 7) and bigger attaching bolts (3/8" vs 5/16").
2. Hydraulics - new tab has two BIG cylinders, old one had only one. The mounting point at the boat is MUCH more substantial on the new tab. The down side to the two cylinders is that they are slower than the old tab (it's a volume thing).
3. Geometry - The new tab has beefier attachments and the cylinders are at the corners of the trailing edge. This take all the twist out of the tab. I think pressure on the trailing edge (caused by tail first landings in rough water) and normal twisting on the corners as water hit it caused the bolts on the old tab to fracture and finally fail.
4. Operating Principals - Because of it's relatively small size (compared to the new tab), the old tab was more of a "water mover" in that it needed to be down more to get it to work. This made it contact the water more and subjected it to more of a beating. The new tab is an "air mover". It is so much bigger that it has even changed WHERE the porpoise starts (was @ 60 now @ 80). This has really narrowed the porpoise zone and diminshed the need to even use the tab. When used it only takes a little bit to smooth things out. I doubt that the tab is touching water at all with the exception of spray. This greatly dimishes the beating the tab is takeing. Of course this would change in very rough water, but that's not the kind of stuff you would want to run over 80 in anyway.

Here's a pic showing the attaching points on the boat. Note how stout everything is. This is built to handle bigger, heavier boats than mine so hopefully this will translate into reliability - it's a theory:D :D

[Liberator25]

Went to the lake today and played with tab and trim. Followed wildman's advice on more trim. I usually run around 5.5 or 6.0 on the trim setting (5.0 is parallel the bottom) so I normally run just a little positive trim. Today I ran as much as 8.0, but 7.5 seemed to be the best. The boat really picked up the nose (not scary, just good). The boat accelerated harder loosened up like that. The porpoise started at the customary 80 or so and I tabbed it out until 90 then I neutralized the tab. The boat hit 105 as usual, but this time it just kept climbing, so I stayed in it. At 112 I started running up on lake traffic (lake lice, ugh!!)and the boat speed was still climbing - slowly - but I backed off due to the risk of traffic and the unpredictability of jet ski operators. I think that 115 was a there for the taking but more open lake needed to find out. I was by myself and I only had 20-30 gals of fuel on board. The boat was lightened up (I left the tool box, anchors, etc. behind). I had never tried to see what the boat would do under these conditions. My real world top speed with passengers, full fuel and all my stuff is 105 day in and day out. I kept hearing how others had run much more and I couldn't figure it out. I guess now I have. Hard to belive that 800 lbs (120 wife, 80 lbs of stuff and 600 lbs of fuel) can make that much difference! We're talkin' 10 mph here. This was with a set of merc labbed 15x34 4 blade cleavers, and 6500 rpm. The 300X motors need a little time to wind out. There might be another 200 rpm in there. I'll find out one of these days. I calculated my slip at about 14% which is good but not as good as it could be. It is better with the motors down than up.:cool:

[Racemore]

Liberator25,what gear ratio do you have?I come up with 105.8 @ 10% with a 1.78.I really don't know what they offer on a 300x.Sounds like it's getting with it though.:cool:

[WILDMAN]

He's got 1.62 gears. His calculation is 129 mph with no slip. I know he has a GPS speedo. The 24 I just sold ran 106 at 6000 rpm with 300X's and 34" cleavers. That's 12% slip

[Racemore]

Cool,I knew it had to have a tall gear to run that fast.Those motors have balls to turn a 34 with that ratio.I need a couple of them.:D Randy,going to the Glen Labor day?

[WILDMAN]

Be there that Saturday! Got that 23 runnin' yet?

[Racemore]

Hey Randy,the 23,not yet.Just did a salvage on a 50'Chris-Craft houseboat this week so the motor kitty got a $1000.I'm going to order the carpet tomorrow and get new steering hoses(from the helm back so I can put the interior back in.The shrimping is getting good for quanity but the market price is the worst it's ever been,got to get 1250#s to get $1000.The next couple of weeks they should grow and the price will come up a little.It will be a race to the end for sure on the motor.I need a 2.4 offshore efi at a PBR ( Poor Boy Racing) price if you run across one.Anyway I don't think the wife is going if the boat isn't ready but I'll still have the house at South Moon.It WILL be at the End of Summer Blowout though. c ya Lonnie

[Liberator25]

My 300X's are fitted with sportmaster short shafts (20") that have the 1.62 ratio. The 25" shaft is a 1.75 ratio. Mine have the off shore (heavy duty) mounting brackets and trim cylinder. My speedo is GPS - Merc SmartCraft. The speeds are real or at least as real as GPS will give ya! Sometimes the difference between GPS and radar is a mile an hour or so (I don't know which is the more accurate) but GPS is pretty much on the dime.

Randy, whatcha think about that TAB, when they say MONSTER they mean it, HA!!:D

One of the differences is that it really is an AIR manager not a WATER manager. It takes very little tab to make it work, maybe 1/2 as much as my last tab and it was pretty big, as tabs go. This new one looks like a swim platform (which is how I use it when stopped):D

Thanks for the trim tip, my courage was bolstered by your advice and it worked out fine. Learning these boats is a journey, thanks for the directions.:cool:

[WILDMAN]

Ron, that tab really looks cool, but it's certainly overkill. If it works it's worth it though. I wanna see a pic of at least 115 on that GPS. I know you can do it. Have a couple drinks, burn off some gas, kick everyone out of the boat, and let your balls hang out!! I'll be waiting for the pic!!

[Liberator25]

I am going to add a second GPS with a BIG digital readout, the SmarCraft one is an analog with a small digital display. The main reason for the additional GPS is I want one with recall. I have to concentrate on where we're goin' at high speeds so I can only glance at the speedo. With a recall we can get the news at a latter and safer time. I'll send you a pic of the "freeze".:cool:

[WILDMAN]

Ron, just get one of the $100 handhelds. The Max speed will stay there forever until you reset it. It will also tell you how many miles you went and how you got there. You can also put it in anyone elses boat to aleviate the B.S. factor. I have a friend with a 21 Rallysport like mine with a 300 Promax who always swears he's doing 87-88mph. I dropped my GPS in his back seat before he made some speed runs. He came back saying he was running 88. GPS showed 80.7 mph. He would'nt talk to me for 2 months!

[Liberator25]

Randy,

GPS has slowed a lot of boats down:D. I wanted it 'cause of the accuracy and no needle bounce. I don't care for the look of the digital ones, I'm an analog kind of guy, but a quick read is easier with a digital. I had a handheld I used on my last boat, but it went with the boat 'cause I had installed a holder and it looked lame without the unit installed. That is a good suggestion though. I'm sure you know that there a lot more boats that SAY they can run 100 than boats that really will RUN 100. I have dusted several of these and I was only running around 90 to do it. I usually just run fast enough to win and not show it all to 'em, that way when they come back with their procharger, nitrous or what ever I can still handle the deal (that usually really pisses them off:D )

C ya!!:cool:

[northeastcat]

Wow all you guys really got me thinking on this one. I run a Sanger 21' tunnel and I cant get it to stop porpoising. Single engine 2.4 200. I turn it up to 6400 in the right conditions but unless I'm going into the wind or runnin on a chop I cant stop the porpoise over 4000 rpm, not sure of the speed.Speedo only works to 20 or so then drops back to 0. It has a big plate,not quite as wide as the tunnel, with a hinge connecting it to the transom but it is stationary,probably sticks out 16" too. Tunnel extension? Level with the bottom too. The engine is set back 16". Any ideas? should I try a tab? I could probably make that extension into a working tab without much difficulty. Some of what I'm hearin is scarin me though about blow over and stuffin it. Is my boat one I should worry about that sort of thing with? NE Cat.

[WILDMAN]

You may have too much setback. I don't know what prop you're running, but you may want to try a cleaver to lift the back. Too much bow lift will cause porpoising.

[northeastcat]

I bought the boat setup this way. It came with a 26p chopper, I had aquaholic cut it into a lightening ET, porpoise is more tollerable but still there. I run a CLE with a bobs cone and trim tab too. I adjusted the jack to one set of holes higher so I could jack it higher, it does not have alot of negative trim capability so If I set it any higher in the initial jack plate setting I cant get it to stop slipping on take off. NE Cat

[Liberator25]

Doesn't have anything to do with tabs. I was out on Weds and it was a beautiful day. Cold sober, dead calm wind, glass lake, no traffic, no wakes and no reason for what was about to happen. I was cruisin' at about 80 when the boat turned hard left in the hardest hook that can happen and not flip the boat. Everybody got slammed around and one of my buddies was completely out of the boat excet for the death grip he had on a grab handle. It is hard to explain how violent the turn was. After we all decided that everyone was OK the investigation started, what the F_ _ K happened?? We discovered the cause was ALL but two of the bolts had vibrated out on the left motor steering wing (I have a Latham dual hydraulic set up). Of the remaining two, one sheared off leaving only one (that caused the hook left) and that last one was hanging on by two or three threads. There was no locktite used in the assembly and no lock washers or safety wire!! Unbelieveable!! The little plastic covers on the 300X motors (the ones where the square exhaust port is) hide the bolt heads so they weren't visable so I never saw them loosening up. The moral to this story is USE LOCTITE and leave the the little plastic cover off so you can see the bolts. INSPECT YOURS TODAY!!! If this had happened at 100 someone likely would have been killed and the boat might be at the bottom of the lake. This was a serious wake up call and I suggest you TRUST NOBODY to do it right, do it yourself!! MY boat is now at in my garage and every nut, bolt and fastener is being inspected and loctited, safety wired or in some manner secured in a way that won't let this happen again. Please inspect your own boats!!! I have placed my trust in others and nearly got myself and three good friends hurt. No one cares like you do. Do it yourself!! Do it today!!:mad:

[WILDMAN]

OUCH! I had a wingplate loosen up on my 2.5 on my 21ft. Luckily it was'nt covered up and I saw it before anything bad happened.

[Kirk Dunteman]

Thats why its always a good idea for everyone to have some GOOD lifejackets on. Even 80 hurts when you hit the water.:eek:

[Liberator25]

That's a nice lookin' Skater you have there. What size are those three blades? What brand? How fast will it run? Lotsa questions I know, but that is a very nice boat and I'm curious.:cool:

[Boss]

LPB,
Can you post some pictures of your tunnel extensions for me???;)

Thanks John!

[LPB]

Been out of town for few days,try to get tomorrow! thank you john

[LPB]

21 Mini Offshore Cat Tunnel TabExtention

[LPB]

Another pic

[mjwalters]

After viewing the failure of liberators tunnel tab I rebuilt my tab in hope of avoiding any problems of my own. I replaced the 1/2'' thick rails with 1'' wide rails and used shoulder bolts to close up the clearances

[mjwalters]

also replaced all 5/16'' bolts with 3/8'' through bolts with lock nuts

[mjwalters]

and extended the bottom plate down 1/2'' for quicker responce

[mjwalters]

full view

[trbocharge]

mj,

real nice job on that tab!

[Liberator25]

Michael,

You are wise to do as you have done. I would also suggest that you "pre-flight" your boat before each outing. While there are many things that matter, these are among the important ones I now do before each outing.

1. Two drain plugs installed:D
2. I check the bolts that hold the motors on the transom to ensure they are not loose and that they are still there.
3. I check the bolts that tie the steering wings to the motors to ensure they are all tight and still all there.
4. I check each bolt on the steering mechanism to ensure none is loose or missing.
5. I check both props lock nut to ensure all is well there.
6. I inspect the tunnel tab bolts (all of 'em) for looseness or visable damage.
7. I try to shake the tab to ensure the hinge is tight and has no looseness.
8. I check both skegs at the top of the trailing edge for cracks as this seems to be where stress cracks on skegs start from.

I know this is not a complete list, but I have had a few experiences that I never want to have again and this 10 minute inspection will help me to avoid those problems in the future.

BTW - that tab really came out nice. I'm sure it makes your boat look even more impressive when it's on the trailer and I know it works really well in the water. You really have a nice ride and your care will help keep you safe. Like I said, you're a wise man. Good luck:cool:

[mjwalters]

Thanks Guys I also do a walk around or preflight, last year I did catch a cracked carrier bearing where the propshaft seals were leaving. saved the lower unit .
All the work on that tab was done in my shop with a table saw, drill press, router and hand tools. The only original parts used were the hindges and the cylinders.I guess us do it yourselfers can sometimes do ok. Of course sent out for powder coat.:D

[sho305]

That is the kind of stuff I would like to have in my living room...:cool:

[87vantage]

any of you guys have a good used tunnel tab system or know where i might locate one.....Just trying to save a buck or two! Thanks S&F

[mjwalters]

87 vantage How wide a tab do you need?

[87vantage]

Not sure....but from the post on here it sounds like most any decent size will work....i am rigging just for pleasure with the occasional blast to out run these big v bottoms around here! what do you have?

[godspeed]

got a 25 motion w 300x s well i have 3 foot seas one day the next rippiles on the bay and it porposes i thought of using a 14 x 20 in k plane not too small not too big im just worried about rough days and stuffin it

ANY THOUGHTS PLEASE :D

[at100plus]

Dude, I told you, NO TAB. Get used to the porpoise, seek rougher water or don't do speeds between 48 and 68 on the calm days. Tabs are dangerous. And as you can see above, just another thing to break, check etc...

[godspeed]

Dude, I told you, NO TAB. Get used to the porpoise, seek rougher water or don't do speeds between 48 and 68 on the calm days. Tabs are dangerous. And as you can see above, just another thing to break, check etc...

IM SURE YOUR RIGHT MIKE IT JUST BOTHERS ME WHEN THE BOAT HOPS LIKE THAT. :rolleyes:

[WILDMAN]

I would'nt have a 24 without the tab. Porpoising is a pain in the ass, and you don't have to get used to it. On rough days, you don't need it anyway. Once you get past the porpoise, you pull it up.

[at100plus]

Dont let it bother you, just go faster of slower and remind yourself how great it is to have that boat. Trust me, you'll get used to it.

[at100plus]

I'm not sure, but it seems to me that a 14" K plane increases the chance for a trip, even if it is all the way up, am I wrong? It's still sticking out past the tunnel, if you catch a wave with your bow up it's going to catch the stern.

Either way, there's no way you will stuff because of a K Plane when you don't have a K plane. It's more weight, another hyd. system, another thing that can break, and if not used properly or if you screw up, it can cause an accident. My .02 I prefer not to have one and I tell Gospeed not to get one because he likes men and he can't drive worth a damn anyway ;)

[godspeed]

I Just Think If I Use A Small Tab It Work Good Enough To Stop Hopping But Not Big Enough To Stuff The Bow ..does That Make Sense///???

[godspeed]

I'm not sure, but it seems to me that a 14" K plane increases the chance for a trip, even if it is all the way up, am I wrong? It's still sticking out past the tunnel, if you catch a wave with your bow up it's going to catch the stern.

Either way, there's no way you will stuff because of a K Plane when you don't have a K plane. It's more weight, another hyd. system, another thing that can break, and if not used properly or if you screw up, it can cause an accident. My .02 I prefer not to have one and I tell Gospeed not to get one because he likes men and he can't drive worth a damn anyway ;)


FUNNY MIKEY YOU LOVE MEN TOO ....OH YEAH I BLEAD MY STEERING AGAIN AND IT IS PERFECT NOW I CAN DRIVE THAT BOAT LIKE A BULL NOW ..LET ME TELL YOU THAT DAY WE RAN THE MULLIKA MY STEERING WAS FUC*ED AND I WAS WORRIED BUT NOW ITS BETTER AND IM MORE CONFIDENT NOW .BUT I STILL THINK YOUR A TOTAL TURD BURGLER HA HA

[WILDMAN]

I usually use the 14x18 Kiekhaefer. It's about 4" up at full up position. On the 24 Liberator, the hop is 60-80mph. I just bump it down till it flattens out and it's like it's on rails. Then you can cruise at any speed you want and are'nt limited to runing above or below the "ZONE" I've got this 20x20 twin ram on mine. I've never had a Kiekhaefer break. Other brands can.

[godspeed]

I usually use the 14x18 Kiekhaefer. It's about 4" up at full up position. On the 24 Liberator, the hop is 60-80mph. I just bump it down till it flattens out and it's like it's on rails. Then you can cruise at any speed you want and are'nt limited to runing above or below the "ZONE" I've got this 20x20 twin ram on mine. I've never had a Kiekhaefer break. Other brands can.


WHAT TYPE OF WATER ARE YOU IN I RUN 3 FOOT CHOP TOO AS WELL AS FLAT WATER

[at100plus]

60 to 80 is a much worse porpoise zone too. Mine is 48 to 68 and I can usually get it to stop with a yank on the wheel at a little over 50 or a little under 68.

Kevin what speeds does yours porpoise? The 300s I'm sure make it worse too.

[godspeed]

60 to 80 is a much worse porpoise zone too. Mine is 48 to 68 and I can usually get it to stop with a yank on the wheel at a little over 50 or a little under 68.

Kevin what speeds does yours porpoise? The 300s I'm sure make it worse too.

I THINK YOU YANK MORE THEN JUST YOUR WHEEL HA HA HA HA

JUS BUSTIN YOU MIKE ID LIKE TO CRUISE AGAIN W YOU WHEN YOU STOP GOING TO WEDDINGS AND BIRTHDAY PARTIES

MINE HOPS AROUND 50 PLUS TILL ??? 75 MAYBE

[at100plus]

:D You got me!

[apache21]

I think your 25 motion will hop alot more with those 300's. I have learned to control the hop as mike has stated above. If you want a tab this would be the one I would use

[WILDMAN]

I run in all kinds of water, but it's usually flat in the river. You don't need the tab much in one foot or more. If you accelerate and turn the boat just slightly, this allows the air to escape and it won't hop at all until you straighten it out. If you want to just cruise in the zone, and it's relatively calm, it will always hop. I found that turning the props in made a huge reduction in the porpoising. Some guys say it's more dangerous, but I have'nt noticed this at all. One thing about the tab is that the faster you go in the zone, the more you need to put it down futher to reach the water. That's because the boat keeps lifting higher off the water. ALWAYS remember to put the tab all the way up before you start slowing down. Otherwise, when it contacts the water again, it will push the bow down hard. I always mount the tab switch on the throttles since I use it much more often than the trim. Everyone I know that has a tab, would not consider running without it.

[godspeed]

I run in all kinds of water, but it's usually flat in the river. You don't need the tab much in one foot or more. If you accelerate and turn the boat just slightly, this allows the air to escape and it won't hop at all until you straighten it out. If you want to just cruise in the zone, and it's relatively calm, it will always hop. I found that turning the props in made a huge reduction in the porpoising. Some guys say it's more dangerous, but I have'nt noticed this at all. One thing about the tab is that the faster you go in the zone, the more you need to put it down futher to reach the water. That's because the boat keeps lifting higher off the water. ALWAYS remember to put the tab all the way up before you start slowing down. Otherwise, when it contacts the water again, it will push the bow down hard. I always mount the tab switch on the throttles since I use it much more often than the trim. Everyone I know that has a tab, would not consider running without it.

GOOD DISCIPTION BUT I WAS ALSO WONDERING IF YOU RUN OR HAVE RUN 3 FOOT CHOP W A 14X18 TAB BEFORE AND DO YOU THINK IT IS DANGEROUS AS OTHERS SAY IT IS ....I DONT WANT TO BEAT A DEAD HORSE ON THE SUBJECT BUT THE HOPPING JUST MAKES THE BOAT FEEL LIKE A BAD HANDLING BOAT IN THE SENSE OF CARRYING A STRAIGHT LINE WHEN IT DOES IT MY PASSENGERS LOOK LIKE THEY ARE AT A METALLICA CONCERT BANGING THER HEADS BUT ANYWAY....

[Dd24skater]

I have been reading this thread for along time and have to put my two cents in

I have a K-plane on my Skater and refuse to use it! It has been there since the boat left Skater in 1988 and has been disconected since 1992

I know there are alot of reasons why people continue to use them everyday, and understand everyone always wants to faster, but its just not worth it!

Please think long and hard before installing one of these on any cat!

Dd

[WILDMAN]

Dd24, have YOU ever used it? I mean, did you buy the boat with it working? The tab has nothing to do with going faster, just getting through the hop or cruising at that speed. Obviously Skater installed it for a reason.
Godspeed, I've run in 3-4ft chop in a large lake with the tab up. It's like having it not there. It does nothing. If Dd24 does'nt use his, it must at least still be there.
You can use one or not, but I hate it without one. Just my opinion.

[Dd24skater]

I have used it!

I also know how to power through the porpose zone with less than two hops without using it! With enough horsepower, the right props and proper setup you don't need it. The difference is so slight with it or without it that the potential disasters it may cause far outweighs the any benfits it has!

:) :)

[at100plus]

That's what I was getting at.


Maybe the 3 liters don't accelerate hard enough to get through it as easily? I can usually get away from it unless it's dead calm, if that's the case, I just don't go those speeds. You're not likely to stuff if it's dead calm though.... I just wonder if the extension even when in the full up position will make a difference in the rough. I've heard the stationary tunnel extenders on 21's do.

[WILDMAN]

Mike, the extensions would make a difference. The tabs pull up pretty far. Getting past the porpoise is'nt the problem. Sometimes you just want to cruise at 60 or 70.

[at100plus]

It looks like they are paralell with the bottom of the boat. If they came up at a 45 deg. angle above the boat then I would think there would be no trip risk. I could be wrong though, I've never had one.


I can understand why you'd want one in the Liberator if it doesn't stop porpoising until 80. I can cruise at 68 in dead calm no problem.

[WILDMAN]

In my pic it's parrallel. But look at how the cylinders are extended. They come up at about a 20 degree angle. The rear of the tab is up 4"-5".

[JIM5656]

I have to say something useless. Being that I have a tab I guess i have an opinion. I just am not sure what it is...LOL. I can't imagine not having it for cruising. I have had it scare me a little a couple of times. I put it up as soon as I get rippin along. I doubt that 2.5's accelerate faster than the 300's. Maybe? With small props but I use 34's. I say get the tab..Be carefull with it. Jim. :rolleyes:

[mjwalters]

I think if you try, you can stuff you motion with the tunnel tab. But used with a degree of common sense a tunnel tab is a good tool to help you boat stop hopping around in the calm and help to keep the bow down in the slop. Work up on it easy and get the feel of the boat a little at a time. You will most likely feel some bow steer if you are using to much down.
I would not run my 30; motion with out the tab!

[godspeed]

I have to say something useless. Being that I have a tab I guess i have an opinion. I just am not sure what it is...LOL. I can't imagine not having it for cruising. I have had it scare me a little a couple of times. I put it up as soon as I get rippin along. I doubt that 2.5's accelerate faster than the 300's. Maybe? With small props but I use 34's. I say get the tab..Be carefull with it. Jim. :rolleyes:

WHAT BOAT ARE YOU RUNNIN W THE TAB

[Liberator25]

Guess what I think :rolleyes:

[yahoo]

More people have been killed by a tunnell tab.

Dont do it, just either go faster or slower.

CM

[WILDMAN]

Jim5656 runs a 24 Liberator

[Dd24skater]

I AGREE YAHOO!

Dd

[JIM5656]

People get killed because of a lot of things. That is a whole new thread. I am a very experienced driver of many types of high performance boats. I would strongly recommend that if you choose to use a tab that you take a long time getting used to it. It took me a lot longer than I expected to get used to this boat. The tab in my opinion is a very useful addition. But it does come with the warning...........Take your time and learn the ins and out.

[yahoo]

If you must have a tab, calculate where it needs tobe to stop the bouncing, then mount the trim hardware so it will not go lower. This will keep it from accidently being bumped, you forget etc.

CM

[godspeed]

all of this good info makes me really think about it .. it just bothers me when it keeps bouncing but imn the chop the boat is awesome and im very happy w it but most of my time giving people rides in it is when it is safe out and then comes the hop and it feels like im always fighting the boat to keep it steady because not every passenger wants to go over 75 mph