Pad shape & handling/chine

[sho305]

I wanted to add a pad to my vee. I got many conflicting opinions in that thread. I want to do it once and be done on this boat, don't care about getting the last couple mph out of this 930lb BR. Just want it drivable and a pad under there.

I looked at a pad on a similiar size/weight 17' vee that was wide, about 10-12" and had a slight vee of maybe 5 degrees(much like the little Sharkey Bullet 13'). This would be easy to add to my vee. My question is would this shape pad be more stable and a bit slower than a narrower flat pad? But then more likely to be right/drivable on the first try in adding it to my hull?

Also found some who just made the first set of strakes larger(mine are about 4" out from vee) and seem to like it. I'm thinking 60-80mph top speeds for this boat.

[Reese]

From what I've been told the slight 5 degree vee is used to theoretically give the prop a cleaner less airated stream of water.

Theory aside, the most hydrodynamically desirable shape is flat, flat, flat.

Just remember the narrow pads don't really start working until you reach higher speeds. 10" sounds about right for your boat.

My personnal theory on pad width is:

You'll loose less top speed by having a pad that is too wide as opposed to one that is too narrow.

[175checkmate]

I have a file that shows how to install a pad on a boat that did not have one. The boat in question was a baja. Rickracer sent it to me great stuff. Whats your e-mail?

[WILDCAT2.5]

175checkmate is it possible to have the file to please?

Thanks
Markus

markus@leocell.com

[sho305]

I thought I might be wrong in my thinking the slight vee type pad would be more forgiving handling-wise, and maybe better over wakes...even though a bit slower as it will take more water.

Should I consider chopping into the existing vee? Any recommendations? That would lower the height of the hull, but I don't want to compromise strength. I think you could glass the pad inside, then cut away from the outside and stringer it at the seam....if worth the trouble. I was looking at the stoker bottom pics at HSR, and it has a vee that drops into a pad about 2/3 the way back...that is a way different hull though.

[Tony Brucato]

Don't cut into the existing vee. The strength you would lose would be too great. Consider adding a pair of strakes to either side of center on your existing pad, maybe an inch or so from center.
Rip the strakes at the same angle as your shallow vee out of core material such as Sitka spruce. Epoxy coat and screw these cores onto your existing pad then cover with more epoxy resin and cloth/filler.
Continue to fill and sand as many times as necessary to achieve perfect flatness and sharp edges.

My Hydra-Sports had a similar pad originally and I added strakes and a pad in that manner. It was worth the effort.

Here's a couple of pictures.
http://brucatosvs.com/pad1.jpg

http://brucatosvs.com/pad2.jpg

[sho305]

So it is ok to leave some of the vee exposed? I assume to keep the height down. Here is a pic, not that good but it is as seen here, a straight pointy vee and the first chine is at the pitot.

[Tony Brucato]

A perfectly flat pad would provide more lift for the same amount of wetted surface.

[sho305]

I looked at your pics, very nice job! Thanks for the tips. It looks like you may have a little shallower vee there in the center than mine. I'll have to measure, but I fear a say..10" pad will get high on there at the vee level and flat. I assume that is why you left a tiny vee, that likely matters little on the whole. I should be up there in a week or two and I'll get the level and see where I'm at with 10-12" pad heightwise. If you think that should work well, that is what I will do. I'd rather be too wide and safe, unless it totally kills the ride. With it trimmed down now, you can't feel a thing.

What do I do forward? I hear some say make it 6' long, then just blend it in? Should I mess with a slight inverted vee in the front of the pad? This hull has no core and is sturdy.

Also, I have eyeballed it many times and see no hooks at all. No straight edge, but it is tiny if there and I'll remove. :)

[Reese]

are you using any kind of setback...I can't tell from the pics.

Pads and setbacks go hand in hand...the flat pad creates lift but you need to counter that with some amount of setback in order to lift the bow...otherwise you won't get the full benefit.

Maybe Tony can back me up on this but from what I understand the length of the pad forward has alot to do with how the boat behaves in a the transition zone before it begins to ride up on the pad.

If the pad is too short, the boat will have a hard time finding it's center of gravity and may propoise, the longer pad length helps to stabalize those forces. The only problem is if the pad is too long you'll loose a lot of rough water handling...my guess would be 5' to 6' long.

[sho305]

This is the way I bought it with 2" block on a 20" transom, the black is just a big old plate/protector on the transom. It needs a minimum 8" setback with the light inline for sure. It was setup this way when fairly new. I wanted to put some in the pad but unlikely doing it this way, unless I build it on the transom. I want to find a 2.0-2.4 for it if I can, later. Have to get a boat in the shape I want first. If I do the transom on this the pad will not be that much more.

I suppose I could do it your way, and run the knees right through the transom for 6" or something...what the heck.:confused: Gonna have it all ripped up anyway, might as well do what works best. However, this hull is like Checkmate175s, and has a stringer in the center I would have to work into. I think I could bulkhead it behind the seat and run the mini stingers up the sides some....or make the floor higher up to the front seats;)

Isn't that how an stv is? With the motor mounted on the knees the transom has little to do then. The stock 1.5" should be fine; save me some work there.:)

[175checkmate]

SHO, I send you some pictures. After spending mny hours looking at the bootom of my boat and pondering the meaning of speed I come up with a "add a pad" thats going to be 9" wide and about 6' long. I am also adding 7" of setback to mine. I may wait untill next year to do the pad. (getting sick of glass already). Here is a picture of the bottom of the V on my boat. SHO's looks the same.

[sho305]

Thanks 175Checkmate! Except my first set of (all strakes, infact) strakes goes all the way back...why, I don't know as mine is 1' longer boat and about the same otherwise.

My 16' Bayliner with pad has the same deal with the strakes stopping about 2' short of the transom. You can feel the Bayliner sit back on those strakes so the bow rises yet is still rides smooth...but then it can't get up any higher. Must be a safety thing:confused:

Lets pad them up!!:D Working on the fenders of that truck today, so I'm getting closer to boat time.

[Tony Brucato]

Have somebody take pictures of your boat running at speed to get an idea of how far to run the pad forward. I terminated my pad forward by thinning the strakes the last foot. It looks like an inverted V.

I would design about a 12" wide pad for your predicted 80MPH top speed and current hull weight.
I regreted making my pad only 10" wide on my Hydra-Sports. It wasn't until I removed an additional 300 pounds from the interior that the 10" pad worked properly. Now you can feel that it's on just the pad.

Even if you leave the pad alone and just add some 4 inch wide strakes close to the existing pad you should see a significant speed gain. Handling and ride would be more forgiving as well.

[sho305]

Also had a guy tell me to put about a 1/4 high lip at the back edge of the pad in the last 6". Good idea? Or is that just for little light hulls?

Going to try for 12" then, as this ain't a real light thing with the BR and all...maybe I can get it down to 900, but with the knees I doubt it.

[Tony Brucato]

Don't do the lip, at least not yet. I've been there and done that on my boat.
If you want to do it later, you can prefab some wedges and glue them on temporarily to try. In any case 1/4" X 6" is way to big.
less than 1/8" high X 1/2" is more like it. Without a ton of setback it will just plow the bow of your boat down. Bad thing.

[Reese]

Three questions...

How long is your boat?

I noticed you have a notched section under the transom, do you remember how far back that is from the edge of the pad?

One more thing how much static setback are you currently running?

I'm getting ready to do my own bottom and was currious to see how my calculations compare to others.

[AlaskaStreamin]

I'm going to be adding a pad on a buddies 17' Whaler. We're going to have the luxery of having the hull upside down. I'm going to bondo on a couple of 1"X 4"'s as a form and pour in gelcoat putty until it gets to the height of the the V. (remember the hull is up side down) I'll be tapering the pad back into the hull about 5' from the transom. After the putty dries, pop off the 1X4's and Wha-la instant pad! If it works, I can glass over it. If it doesn't, I will just sand it off with my buffer and 8" 24 grit pad. Heck for a trial, you can use Bondo and gelcoat it.

When playing with something that may very well need adjusting, I just can't see using glass until you're happy with the results and are ready to make it permanent.

I'd bet you could do this with the boat on it's side vs flipping it over each time. Just drain the fuel and pull the battery and loose stuff. I do this all the time adding wear strips. Never had a problem.

[Tony Brucato]

Reese,
My Hydra-Sports is 19'-2" The notch in the transom is 7", the jackplate has 9 1/2"setback. I also have a 1/8" high lip on the pad 26" from the back with aeration plumbed behind it.

[sho305]

Hehehe...I seen the overlay there and wondered if you had air there;) You think it worked? I thought about a step and a little inverted spot with air, then back to flat maybe 3' up the pad...then I just thought about inverting it in the center until I got there from the front? Maybe a channel does not get air back there, or everyone would do it.

[Tony Brucato]

It does work. Look at some of the stepped hulls on offshore boats. The step goes out to the chine on those boats where it can get air to ventilate the notch without extra plumbing.

I don't think the channel going front to rear would help much. Most of the air would stay in the channel.
Aeration all across the running surface to reduce friction but still provide lift is what we want.

[sho305]

I was thinking if you inverted it until the front part of the pad running in the water, then turned it flat the air would disperse under the pad and spread....but I think you may be right as your way it is evenly dispirsed for sure. Hmmm, wonder how I could do this on mine without tons of work, while I pad it. I see Manerhiem(?) using turned down strakes, and it looks to create a spray of water and air bubbles to go under the hull. I saw an offshore that had scoops on the front ducted to the steps also. I got this great one way valve for the sump pump the other day to keep the water....:D Problem here is the small area in the water opposed to offshore. Like yours, just one at the back works here.

[Reese]

on a side note...a few months ago I was reading an article in Hot Boat? about a pretty radical lenco tran outboard...just currious if you guys worked out all the bugs in that setup.

Was the ability to shift gears ultimately helpful for that type of racing?

BTW Sho, for sanity sake I vote for the flat pad with no air scoops or vents.

[sho305]

I see your point Reese, but then again if I go to all the work to pad this and I can move up to 2000 technology...I should. This hull has no core, so air supply is easier. Just need the best place, shape, size and I am good to go. Likely I can put a little step in the center for acceleration and another supplied air in the back for the pad. Maybe I can work the front one into the shape of the front of the pad? Everyone is saying 6-7' pad.

I could put a temp on there and run it before I pull it down in the spring.

[Reese]

with that idea but I just don't think you're gonna get the results your looking for.

I don't question Tony's modifications but I'm not sure that aerated bottoms are that effective on small light boats. They seem to be the rave on offshore boats but that a totally different catagory of boat.

All boats that ride on a pad are already getting an aerated effect...adding more air to the mix is not necessarily a good thing especially if it adversly effect the prop.

Bottom line is that the only way to know for sure is to first build a flat pad and test it...then come back and add whatever new air system you want and test it again.

I think that that a well designed flat pad will account for nearly 99% of the speed increase...how much will additional aeration add to that???

[Tony Brucato]

Reese, That transmission project had a lot of potential. Unfortunately the customer lost interest in the project before it could be refined.
I agree that Sho should build a straight pad first without any tricks and then after establishing a baseline of performance, experiment with one change at a time.
My first efforts with the wedges lost speed compared to the straight pad. I would epoxy my wedge strips where I thought they should go and then test. Back at the ramp I could heat up the wedges with a small propane torch to pop them off, and then glue them in new locations with 5 minute epoxy.
The location that I put them resulted in 2mph speed gain by themselves. I then added aeration and picked up almost 1 1/2 mph additional.

[sho305]

Thanks for all the help Tony, that thing must be hauling the mail now!

I was planing to use wood for the pad and mat/glass it over. If I did do a step, then I figured I might want to do it differently in preperation for that. Maybe not have wood there? Or should I not worry?

[Assassin]

175checkmate is it possible to have the file too please?

yellow_stinger@hotmail.com

thanks...

Assassin

[gaineso]

sho305, I actually posted this over on that political thread where we got to ribbin' about how warm it's NOT up North. Anyway, This is what the pad on my Glasstream looks like. 950 pound hull (guess, 'cause the all up weight is between 1850 and 1900 lbs including 18 gals of gas and full fishin' gear including 2 batteries and a trolling motor. Got real close to 60 today. I know if I took the trolling motor (52 lbs on the bow) off, I could top 60 with an '86 Mariner 115.. The concave area, which runs about 8' forward is supposed to carry a little air back with it. That may be why I have trouble getting my motor up as high as I want it. It ventilates bad over 3" below the pad, even with a total of 12" setback. Steady as a rock at almost 60 though. Not too bad for a heavy 7' wide X 15' long boat.

[sho305]

Thanks Gaineso! I wonder about the concave, as some 'Streams have it too. Some say make it flat...so I don't know. I thought maybe it would keep some air in there. Of course if I am adding it to a vee I likely can't do that.

I know mine will have to be wider, as it is heavier and I would rather error on that side.

[sho305]

Spring is close, and I want to get the slow-liner (bayliner) out and I'm putting a jack on it. Also will whip up some temp pieces for the bottom. It has a pad, but is flat and not raised. So, I am going to try a flat addition on it that raises it up about 1.5", so I can relieve it a little maybe 4-6" at the transom. Plain old flat pad to start with.

Also was looking at my '67 Chriscraft with the V8 I'll fix some day:rolleyes: Here is what the bottom looks like and has a pretty shallow vee. What you think about the red mods? It will blow water up the side when you turn, so I thought I could sharpen the chines as they are about level now and small. It is 19' with a small block Ford keeping the stern down nicely. I'm thinking maybe 12" of pad. Only runs 40+ now with a big hook in it and a two barrel carb. Must be close to an inch hook about 4' from the transom. The rotten slats inside there are about 1" thick. Ouch. Gonna be stringers some day soon.:)

[Reese]

on keeping it simple...you did say you were gonna flip it right...if you don't you're gonna wish you had...easily half the time and work.

[sho305]

I re-read all these pad posts, and thought I would go simple like suggested:) I would like to make a plug and bolt it on to try, then I would flip and glass up permanent when happy with it. I was thinking I could go slightly wider than the existing pad, and maybe 1-1.5" thick. Maybe then I could get 4" of relief or so...whatever I can without making the new pad very high. I can get to most of the pad area inside, so I could bolt/screw something on there easy. Hull looks to be about 3/8" thick glass there, should be only compression force on it...maybe bolt thru to something on the inside. What you think? Just a smooth water speed run or too at 40+.

I think it needs more than 6" setback, so I hoped if I had 4-6" relief on the pad I could get away with 5-6" jack and it would be easier on the transom and steering attachment, etc. Was even wondering if I could use a 2x8 cut and shaped and resined up to test with. That is 1 1/4" about.

[Reese]

a temporary pad and bolt it up through the bottom but I'm not really sure it worth all that trouble. A temporary pad would be great if your calculations were really wierd or way off...I don't think they are.

A 10-12" pad will ultimately be just about right (I'd go for 12") and you've already decided on the approximate height of 1 1/2" which I also agree is good. I also agree that a 6" static setback along with a 6" notch is just about perfect. Only thing left is how long to make it...most are 5-6 feet in length.

It's a lot of work to make a temp pad just to have it glassed in later. I think you've done enough research to make a very good estimated guess...I say go for it and make it permanent. Good luck with whatever you decide to do...one thing's for sure...it's gonna be really exciting to see how smart any of us think we are when it goes back in the water...:D

[sho305]

Ya got me thinking, but I am finishing another project here so I can't rip into it yet. You think that wide? I think it is 8-9" now, I forget. Not enough with the slow motor anyway and not raised. I am going to toss some more wood in the transom too while I am at it, and a crossbrace or two above the pad. Not sure if I should bother extending the strakes back, but might since I'll be there.

I might not be able to find a bigger prop for that motor:eek:

[Reese]

of work to begin with and making it 10" is really only slightly bigger than what you presently have. I know that if you added a 10" pad with a 1 1/2" ledge or lip it would be faster than what you have now...a 12" should be even faster...especially at the speeds were talking about.

You already know that the faster and lighter the boat the narrower the pad...but slower heavier boats need all the lift they can get and a wider pads will do a much better job at these slower speeds.

One more benefit that we don't seem to mention much is that a wider pad should also improve your holeshot and overall acceleration to top speed.

[sho305]

Well, you never know....that inline could jump on over to that hull at some point:) For now, I just want to mess with it the way it is. The pad will be easy for me to do compared to the transom. That was a pain the first go around. I'll shoot for 12" and see what it looks like. I think I can measure it some next weekend, forgot last weekend I was having so much fun trail riding the golf cart.:cool: I'll play with this before I get into a faster one. I can pull this one out with the cart, very handy. It also has the water pickup on the barrel just ahead of the prop, so I should be able to jack it easily until the bow lift goes away and get good water.

Kind of a slug out of the hole compared to the Checkmate. I can only figure the prop is big. Takes off ok, but no rush. It will plane slower though. No punch at any speed really, but gets the job done. Maybe that is just the chryco showing? I can trim it way up and cavitate a holeshot, when it revs I can bump the trim down to the top speed spot and it grabs and is on plane real fast. Kind of abusive though. Otherwise it takes off the same, trim up or down just changes the bow angle. Other boats I had got up faster with negative trim.

It can't be that bow heavy; I lifted the bow (barely) off the trailer when the motor was off.