Jackplate wedges to correct shaft angle???

[B.Mac]

Why are wedges used between the plate and the motor?
I would like to correct this positive trim as seen below but I'm not sure wedges will do anything? I have not reached the limit of trim in any direction, it just seems to lever the bow at this angle.
Can anything be done to bring the bow up and still run the shaft dead parallel with the surface or am I needing the downward force of that positive trim to lever the bow up? Will wedges do anything in this application?
B.MAC:D

[Rickracer]

....mo setback. All wedges do is move your range of adjustment in one direction or the other, normally giving you more negative range.

[skydog]

try to lower motor or a prop with more bow lift!!
Skydog

[10.5' Tunnel]

Doesn't bob's machine sell the adjusting wedge jackplate?

[Gerben]

Wedges are usually used for a bit more trim-in (tuck under)
Some hard to plane boats benefit from this.

They have nothing to do with the angle your motor runs at full throttle. (unless you needed loads of trim-out in the first place and benefit from the extra range wedges could give, which will result in an inefficient setup)

Getting motor parallel to water:
Move all weight to the rear
Get bow-lifting prop
More setback
If under 80mph lose nose cone

Have fun,
Gerben

[B.Mac]

Wedges are not the answer......
I think the real problem is not having a solid fulcrum point (12"-14" Pad) to lever against the water and get the bow up, therefore I have to overtrim and plow the stern to get lift......
Does this make sense? I'm running 13" of setback now on a 21' 'Mate that I can lift the trailer tounge with one hand easily.

Without that fulcrum point the "V" plows....if it had a flat fulcrum point it would have to lift......yes/no?
B.MAC:D

[jmdank]

when I am done with the transom, stringers, and floor I plan on constructing a pad. I am needing to know more about this also. your not alone on this one B.

[Techno]

I would readjust your trailer setup. With this little weight on your tongue you can get severe fishtail at higher speeds. My trailer is like yours and the boat slipped back only a couple inches. I didn't know it and had neutral tongue wieght. Wasn't nice.

I'm planning on adding theses wedges as another function is to get the netrual trim point deeper into the guide/ support thingers. Your not supposed to be close to the end. I think zero trim on mine is the 2nd hole from the top and the wedges will get it down further.

Your fulcrum point thing isn't the answer. Somewhere on the site there is a movie of a hydrostream doing 105? Great film and it's not in the water!
Fulcrum angle or lever I think has to do with center of gravity and center of lift.
Plus when you move your engine back you shift 400lbs back too so there is big balance change along with the lever increase deal.

Also check your bottom for a hook since a rocker would be a different problem. Check your transom for stiffness since it can be "trimming" if it flexes. Finaly check the bottom for stiffness since it can produce a hook under power. Someone mentioned jacking the boat up with a pad to spread the load. The boat should move and not flex.

[Airboater]

BMac why not try another prop and jack that motor up I still have that 28 chopper and a 27 SRX.You may be maxed out on HP for a 21fter and adding a pad will increase your speed but it will kill your ride in the bay with 2ft chop and is the motor done yet.:D

[Raceman]

Am I the only one who thinks that setup's doin' a pretty fair job of totin' the nose for a 21' boat? I don't think it'd run that high with a hook in the bottom, even with the setback. My question would be, at what point in the up trim range does it quit picking up speed?

I agree with Techno on the trailer issue. Not only will being light on the tongue make it not pull as well, hit a severe dip in the road and it's much more likely to snatch the hitch off the ball.

[B.Mac]

It wont break loose until I give it the trim you see above. Speeds @ WOT with neutral trim are @ 65-66 I gain another 3-4 mph once the bow breaks loose and you feel the air under it....
I realize however that theoretically optimum speed would be achieved with the motor perfectly vertical.

I am changing one thing: I'm going to a manual Jack due to the Bay chop 70 mph running I do......I'm presently running a 13" combination of an 8" Panther jack and another 5" of solid setback....I'm afraid of that setup in 2' - 3' chop @ WOT. I'm searching for a 10" - 12" Rapid Jack or similar to take that beatin'......

Trailer readjustment coming up....I would freak if my boat hit a tree after all that transom work:eek:
B.MAC:D

[Talon2.5]

hit a severe dip in the road and it's much more likely to snatch the hitch off the ball.

been there done that!! watched the talon go into the on coming traffic lane than head down into a ditch and as i heard the trees crckling i turned my head, couldnt bear to watch the rest, when it finally stopped it was sideways on the trailer :eek:

Bmac, without strakes and a pad be happy with what you have accomplished!!!

[B.Mac]

Originally posted by Talon2.5
Bmac, without strakes and a pad be happy with what you have accomplished!!!

NO!!!!
B.MAC:D

[RichS]

The parts ya got should be alright. But, to lessen the stress on the jackplate the setback should be on the transom and the jack next to the motor.....

[B.Mac]

I bought this parts plate that was installed that way. The design requires the Jack be up aginst the hull and fully supported or......:eek:

I'm more afraid of the lateral stress on the scissor mechanism when chinewalking through 2'-3' bay chop @ 70 mph. I'd hate 'ta get hit in the back of the head with a 400# Merc:eek:
B.MAC:D

[skydog]

Rapid Jack is a great plate but it has no cross braces. Might look a diffarent plate.
SKydog

[B.Mac]

'dis one???? I think it oughta hold....looks like 1/2 " aluminum:eek:
B.MAC:D
http://forums.screamandfly.com/forums/showthread.php?postid=236455#post236455

[skydog]

Looks good!! Good price for sure!!
Skydog

[B.Leonard]

I would say you're doing pretty good for a boat that big and a motor with that little power :D

Anything more will require you to make some big changes since you're starting to well exceed to the original design of that hull.

I think you're right about it plowing, however and I've said this before, if you had more torque (i.e. 3.0 EFI) you could use less trim, run a prop with more cup (i.e. lift the bow) and push that pig to 80.

If you want to do it with that motor you'll need to get on the surface and that will require a pad but will cost you in ride quality. You'll also have to switch to a cone/LWP and surfacing type props.

Since you obviously can't leave it alone and love those "little" motors :D , get to work on the pad. Maybe you should've started it while the motor was in rehab?

-BL

[sho305]

If this hull is like my old Checkmate, it has a plain vee and strakes. What about the newer vees, like superboat/progression/etc that use a small pad with a slight vee or the strakes on the tip of the vee? Looks like they get some air under there without the lift of a pad. That would be easier to add to a straight vee and still have good rough water abilities. Any idea of gains going this way instead of the flat pad in a case like this?

[B.Leonard]

Since he is modifying an existing design I don't think you could expect similar results.

Therefore, to make sure all that work was not in vain, I would not try to turn a Checkmate into a Superboat in my back yard and would go with a simple pad design. Make it wider than normal so you know it's gonna work.

Unless you have a lot of time to try a couple different type configurations, I'd sacrifice a little ride and go with a wider than normal pad. Maybe aerate it like Tony Brucato did to his to minimize the added friction of the extra width.

:cool:

-BL

PS

That is why I'm leaving my Lund alone. I'm content with backing it off to a steady 65mph rather than a gunnel walking 70mph rig. If I want face-flappin speeds I'll break out the Sterling. Can't have it all in one boat without spending 10X the cash :rolleyes:

[Reese]

know my feelings on this subject. You can play with props, try more or less setback, move weight around and spinkle pixie dust but you'll never get to the real number you're after.

A 12-14" pad will probably account for 10 MPH with no other mods...you're gonna need about 20-23" of total setback. I like the idea of using 12" jackplate and adding about 8-10" notch at the transom.

This combination will give you better holeshot and much better top end...best of both worlds. Oh BTW...what's the magic number...my guess it's really 80 isn't it.:D

[B.Mac]

High Performance pixie dust for sale, guaranteed to give you 25% extra horsepower. Just add one 16 oz. bottle to 28 gallons of fuel.
One gallon only $129.99
Please send check......er CASH of three "flexpay" payments of $43.33 to:
B.MAC
Sartasota FL

I hear ya guys....it's pad time.......gotta think this one through real good before I flip this beast.
Yep 80...fer now any way:D
B.MAC:D

[Gerben]

BMac seems to like fiberglassing more the boating. :eek: :D

Get Leonard to chuck the motor back together and have some fun on the water. How many runs did you get after the transon was done?

Get a load of setback, a nice bowlifting prop and have fun. :)
Gerben

[Airboater]

BMac what are you going to do when you reach 80mph !!!want more speed or just be happy with 80 cause your slill going to be behind BL's stearling.What about the resell value are you going to be able to get all the hard work in $$ back when you sell to get something that will run over 80. What about some trim tabs to help with the chime walking its a lot cheaper than a pad.:D

[B.Mac]

But I like speed, especially the feeling of "floating" in a "V" hull......
I ain't paddin' it no time soon, maybe next winter, and whatever speed I get is gonna have 'ta do for awhile 'cause I ain't buyin' no more used boats..........

As it is now, I'm like sodaboy around here.......everybody's gotta slow down 30 mph ta' get a drink from my two big coolers when I'm runnin' WOT....

I'm gonna do some research on padded "V" bottoms, strakes and lifting techniques then at least I'll know where ta' start......
Nothing major......nothing like that transom anyway..

Bruce who? Oh I'll be on that tunnel's tail before too long:D
B.MAC:D

[ShorePounder]

Nothing major......nothing like that transom anyway..

Famous last words... :eek: :D

[sho305]

is in good hands....we would not let him put a 4" thick nuke-proof pad on his ride:D ...so it would be easier than the transom for sure;)

[B.Leonard]

Actually trim tabs just may be the answer.

They will help with your gunnel walk/chine walk to a degree and with a family boat they are an absolute necessity to be able to level the load with several people on board and drive the bow down hard to keep the wife from b%tchn on the way back to dock when it gets rough from afternoon storms :D

That said, there is still time to sell and get something made to go 80mph :rolleyes:

-BL

[B.Mac]

This beast does get ugly at 70 and is a handful....will tabs tame the walking a little at WOT or will they slow me down?
B.MAC:D

[B.Leonard]

You will loose some speed.

Lets face it, when you're trimmed way out and on the edge of loosing control, you will gain 1.3 mph or less over being in control, level and enjoying the ride :rolleyes:

On my Lund I also had to wire them to one Pro Trim toggle to operate both tabs simultaneously. That is the only way to go because for top end they must move together and the same amount with very little concentration from the operator (you).

Bennett doesn't sell the wiring/switch to do that because few people are using tabs while running that fast so it took 3-4 relays and some custom wiring. Their dual switches are hard to operate at those speeds in a boat the size of yours and mine.

Also, at those speeds the boat is so far out of the water (at least mine :D ) that the tabs are 2-3" from touching water so it takes a second or two longer to get them in "range" where they can work. Then when you stop you may find that they are way too low, so you're on that switch a lot. That is another reason why you need them hooked to a single switch.

For top speed they're a bit of a "Band-Aid", but you'll really appreciate them in so many other ways when you're just boating normal w/family on board.

Bennett's run about $400 with the dual rocker switch. Add another $40 for a Pro Trim switch and the relays to make it work.

:cool:

-BL

[goodsax]

B. I have tabs on my enchanter. They great for pulling the kids real slow on the wake board because they force the bow down. I can stay on plain at incredibly slow speeds. But.... even when they are in the fully raised position, they still catch water at WOT. I am planning to remove them this season and see if I can get more bow lift without them. I think I will.

I'm not familiar with the starflight bottom. Both my checkmates, and my friends mate have pads. Is there any pad??? Do you have bad chine walking?? Once on the pad mine rides pretty good. How's your steering and motor mounts??

[Reese]

type outboard boats that I've seen use tabs are gambler bass boats. Instead of placing the tabs on the the back transom they moved them under the hull...much more effective because they didn't need to travel much to make a noticable difference.

Of course the problem of re-engineering the underside of the hull to accept the tabs is not easy. One other problem with the traditional transom mounted tabs is they are alway in the when your trying to get back in the boat...if you ski or tube your not gonna like banging your knees every time you get back in the boat.

I don't thinks tabs will work that great for you but I'll keep an open mind...Hmmm $400, wonder what a new pad will cost...:D

[B.Leonard]

If your hull is not coming completely out of the water and up on the pad (or padless area) in the rear or you have little deadrise in the rear they will catch water. That is true.

I shortened the rams on mine to ensure they would clear. I later found out that Bennett makes short rams for just that reason (and lack of transom space).

You really need to see your boat at speed from the rear to determine how to mount them otherwise you may wind up with several sets of holes on the transom. Don't go by the template they give you.

Gambler does have a cool setup with their tabs.

-BL

[sho305]

Note that using tabs at high speeds in rough water can be very dangerous unless you are very good at it. I have seen 24' vee hulls hook a tab in 3-4'ers and bones got broke.

[B.Mac]

OK Bruce.....This is only a little friendly Lobster competition here ya don't have 'ta get violent:eek:
B.MAC:D

[sho305]

They are fine on smooth water or moderate speeds; or if you are sane. People here in Lake Michigan with the tight waves just get too greedy. You can run too fast with them and get in trouble. They tend to oversize them for the boat also, and then when they grab you really go flying. That is why they recommend pretty small tabs for the hull size. If you are reasonable it would not be a problem. These guys were running 60mph in tight 3-4' waves, actually bigger that day I think. Problem is when you get up on the side and come down the tab slaps your bow down like a brick right into the next wave. Most times we were traveling parallel to shore. Maybe some drinking going on there too.

They would trim it up for speed then lower the tabs to keep it in line. Works great until you get out of shape.;)

[Techno]

Where is your prop shaft in relation to your bottom?
Looking at the picture it seems as if it's deep but hard to tell from a picture.
I'm thinking that at that high an angle the prop goes deeper and you may get away with a higher setting?

[B.Mac]

My best top end and bow lift comes from the shaft @ 3" below the "V". When I raise the motor even 1" the bow drops and it scrubs off 3 mph. I've tried several non-surfacing props and found the Tempest to be the fastest top end. I know a fella' with the same set up and a 280 EFI and he hits a wall at 79mph so power isn't the cheapest solution, it keeps coming back to a pad.

I'm considering a 12" pad running the last eight feet.

I'm also considering allowing the tip of the "V" to protrude through the flat pad a couple inches, what I'll end up with in the end is actually two giant strakes @ 5" wide on each side of the "V" bottom.
B.MAC:D

[Reese]

the V-sticking out the bottom should help keep the aerated water from the prop...but the two 5" wide pads only adds up to a 10"...you can't count the V. Eight feet seems a bit long.

Just keep in mind that Stroker Bass boats are running pads damn near 14" wide...he's a pic of one of them.

BTW...does you hull have any lifting strakes??? I really can't believe you running near 70 with absolutely no pad or strakes???

[sho305]

14"? Geez!
I see it has a raised pad, but it has as much vee as the hull. Might have to step the pad somehow, it looks like it could get pretty high otherwise. Unless that does not matter:confused:

Look/search in one of my pad threads and Tony Brucato was very helpfull on the 'massive strakes mod' he did on his yellow boat; and he included nice pics of it. Also told about the gains he encountered. There is lots of info here in the pad threads, but you will have to figure what you need for the rough water. It seems that the width is needed more with increased weight of motor/hull. The 'Streams have narrower pads, but they are light.

If I ever get to the bottom of my Chris Craft V8, it will have 14" minimum:D I searched:

Tony's here: http://forums.screamandfly.com/forums/showthread.php?s=&threadid=27297&highlight=pad
http://forums.screamandfly.com/forums/showthread.php?s=&threadid=20932&highlight=pad
http://forums.screamandfly.com/forums/showthread.php?s=&threadid=23091&highlight=pad

[B.Mac]

I got them, two steps in the strakes but no pad.........

[B.Mac]

Just a "V"

[B.Mac]

No not in my car :eek: 2 miles out in Sarasota Bay in two foot chop:D
B.MAC:D

[B.Mac]

You got a pic of the bottom of one a 'dem? I gotta lotta questions regarding bottom design, how strakes work, transitioning fron V to pad, placement of pad, height of pad etc. etc.
B.MAC:D

[Reese]

Of the stroker bottom but I can post a picture of a Champion boat that might give you some ideas…I’ll post it tomorrow. Bmac, you probably already know a lot of what I’m gonna post so bear with me if it’s redundant.

You will not be able to change the basic design characteristics of your Checkmate (other than the pad) but there are a couple of cues that are interesting if you look at the pic of the stroker. If you notice closely the very center part of the pad has a slight V…just like you suggested. Second the pad is approximately 1 ½” high before it transitions to the first dead rise angle. That small lip or ledge helps to direct the flow away from any other parts of the boat reducing drag.

Notice how the dead rise quickly diminishes to almost a flat pad as it extends outward…that design really helps with holeshot. These boat are typically using 13-15” of setback along with an 8” transom notch for a total of 21-23” of backset…a lot of 20-21’ bass boats are using similar amounts of backset along with 12-14” wide pads. I’m pretty much coping this design for my own tug project.

Strakes work just like pads except more conservatively…they also help to turn the boat as it banks.

Height of pad…1 to 1 ½” should be just about right. Any less and the water spray might want to cling to the side of the hull’s deadrise section.

Placement of the pad, again depends on how much total setback you want…how long to make it is tougher to answer. Reading between the lines on a couple of obscure articles it seems that with some boats making the length too short may lead to proposing, unfortunately making them too long creates a harsh ride in rough water conditions.

Well that’s all I know…sad to think this represents a year of research…I'll post the pic of the Champion boat and see if I can dig up any articles.

[sho305]

Find a pic of a fountain, that will freak you out. There is one of a Coast Guard jumping a wave that shows the bottom with its multiple steps. From the transom to the pad is like a stairway of steps:) You also have the concern of loosing hull length in essence with lots of relief; making the hull shorter in the water. Like the vector with that big beak, you see Fountain doing that too. I rode in a 28' deep vee that was smoother than a 36' fountain. That 36' was fast for a 36' though.

However, chopping into yours like that would not be easy and there is room for improvement without that. If you look at Brucato's yellow hull, it looks like it has the big strakes close to the vee, then another set of strakes aside that. Maybe that would work for you. I'll try to draw it. Just an idea. Not knowing how to relieve it this way though, except to end the pad parts early. Leaving the vee at the transom might not hurt that much.

I'm getting good with the old Paint program...you know you can draw one side and copy it, then flip the same selection to make the whole thing nice and even:cool:

[Reese]

this will take you to a webpage that should directly load a pdf file which shows the bottom side of a champion boat. The picture quality is not that great but you should get the general idea.

Champion Hull (http://www.copyright.gov/vessels/regs/dvh0057.pdf)

This is another little interesting link that talks about the relationship between lift and angle of attack...it also tends to show that minimum drag is achieved in a small window of opportunity where skin friction and attack angle is maximized.

Skier's Paradox (http://members.iinet.net.au/~bluep/skier-paradox.html)

Of course last but not least is Jim Russells website with a couple of interesting articles about drag, aspect ratios, planing surfaces...check out articles 24 and 25 called "rocket science".

Aeromarine (http://www.aeromarineresearch.com/TBPNews_downloads.html)

[sho305]

Thanks Reese, I love that stuff!:cool: