What Size Ply

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anthony_marquart said:
I think 1/16 would be better for that size.. just my opinion though
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Billy,

I agree. The 60/90 rigger tub I built a few years ago is with 1/16" and is still solid and straight with no repairs ever needed. I have a 60 RR that used 1/32" and has warped and I cannot get it straight again. Will go into the trash. The weight difference is tiny compared to the strength needed for a 67 engine.
 
John Knight said:
anthony_marquart said:
I think 1/16 would be better for that size.. just my opinion though
Click to expand...


Billy,

I agree. The 60/90 rigger tub I built a few years ago is with 1/16" and is still solid and straight with no repairs ever needed. I have a 60 RR that used 1/32" and has warped and I cannot get it straight again. Will go into the trash. The weight difference is tiny compared to the strength needed for a 67 engine.
Click to expand...
Thanks guys. I used 1/32 on my last 67 tub deck and noticed its easy to twist. Im in the process of building a new tub and was wanting some opinions. I will go with the 1/16" ply.John, I should have the sponsons ready by the end of the week and shipped by first of next week. Tell Don to give me a call.

Billy
 
Terry Keeley said:
Put it cross grain and leave a lip and it'll be even stronger... :)
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I put the bottom sheet on cross grain and the top with grain running length wise. Or are you saying to put the top and bottom sheet cross grain
 
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Build the whole thing out of Balsa Wood Billy. That way I won't mess up my prop when I run over it. ;)
 
Scott Norris said:
Build the whole thing out of Balsa Wood Billy. That way I won't mess up my prop when I run over it. ;)
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How about I smack you up side the head with a piece of balsa. That way I wont mess up a good piece of wood. :lol: Oh, and you will have to catch it first before you can run over it.
 
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Terry Keeley said:
diamondback21 said:
Terry Keeley said:
Put it cross grain and leave a lip and it'll be even stronger... :)
Click to expand...
I put the bottom sheet on cross grain and the top with grain running length wise. Or are you saying to put the top and bottom sheet cross grain
Click to expand...
I put them both on cross-grain when I built with wood, learned that from Gary Preusse, works good. :D
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Terry,

If the top or bottom ply is put on with the grain going across, this will take a pretty large sheet of ply to begin with. At least if it is one sheet for the entire ply. Did I get this correct? I am trying to make sure I understand.

Thanks in advance.

Mike
 
Billy,

Go with the 1/16" for the bottom at least. I can't really see a reason to using anything more than 1/32" for the top, since none of it is under any real stress like the bottom is. You could possibly get away with 1/32" for the bottom, but you'd better reinforce it with CF and glass, which will probably have you back to the weight of the 1/16"

I like to build with the tub bottom cross-grain and the top long-grain. The cross-grain bottom makes for a very stiff tub. By the time you cut out all your top windows (engine/tank area, radio box, etc...) there won't be enough left for there to be a difference which way the grain lays. If you use the long-grain for the top, your cowl-lip "ledge" will be much stronger. As for availability, Lone-Star models will cut it any way you want it if you buy a 48x48" sheet. Personally, I would never build anything without continuous surfaces (one piece for every surface).

Thanks. Brad.

Titan Racing Components

BlackJack Hydros
 
Last edited by a moderator:
Brad Christy said:
Billy,
Go with the 1/16" for the bottom at least. I can't really see a reason to using anything more than 1/32" for the top, since none of it is under any real stress like the bottom is. You could possibly get away with 1/32" for the bottom, but you'd better reinforce it with CF and glass, which will probably have you back to the weight of the 1/16"

I like to build with the tub bottom cross-grain and the top long-grain. The cross-grain bottom makes for a very stiff tub. By the time you cut out all your top windows (engine/tank area, radio box, etc...) there won't be enough left for there to be a difference which way the grain lays. If you use the long-grain for the top, your cowl-lip "ledge" will be much stronger. As for availability, Lone-Star models will cut it any way you want it if you buy a 48x48" sheet. Personally, I would never build anything without continuous surfaces (one piece for every surface).

Thanks. Brad.

Titan Racing Components

BlackJack Hydros
Click to expand...
I use 1/16 cross grain on 45 and above for the bottom, but was wondering what would be better for the top. I have it glued up now and used 1/16 just to be sure. Im very pleased with the results. Glad I went with the 1/16. Thanks for your help.
 
Billy on my Whiplash I laminated a sheet of 1/32 ply with Pre-Preg CF before I cut it out. It did not add much weight to the boat at all because there is no excess epoxy to worry about.

normal_HPIM1485.JPG
 
Basically what you are looking at with a twist is shear forces. Everything so far is just to use stronger materials whether different or thicker. When you cut out the top for radio and engine the corners are where you are loosing strength and promoting twist. Any "fillet" or rounded inside corner would be a plus.

You should really try some carbon or glass in the engine compartment. Go down one side, across the bottom and up the other side with one piece about 3"-4" wide. You have then created a structural shape and it does work.
 

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