question on kevlar

[GrapeNutsCereal]

I want to build a 20-21' flats boat like a hewes or maverick. Im wondering if stich and glue using kevlar/foam would be practical. Ive been reading on foam cored and plywood.. Im wondering if I took a panel that would normally be cut out of 1/4" plywood and just cut it out of klegecell and treat the patterns as plywood panels using kevlar would work? I want to build a light, strong boat. I fish in water 8 inches or less and would like to draft shallow as possible. Also are there examples of tunnel shapes for a tunnel hull in a flats boat? Can smooth curves in a tunnel be achieved with klegecell or corecell, (Ive seen the .5" grided corecell). I assume smooth curved tunnels would be better than straight sided tunnels due to less turbulence? Also typically how many layers or weight cloth would be required of kevlar over a hull to achieve the same strength as glass? Half as heavy?

So, overall, am I going in the right direction thinking that a kevlar/foam composite layup (stitch and glu style) would be stronger lighter than a stitch and glue glass boat? If not, is there any benefiet to using kevlar tape on seams in a regular glass layup? Is it compatible?

Thanks for any opinions! Research research.

[JEM]

Few things: You have to vaccuum bag kelvar. Otherwise it floats in the resin and doesn't wet out properly.

Thicknesses for a plywood boat don't directly translate to foam/kevlar. Kevlar will give you the puncture resistence, but not the stiffness you'll need with using foam. Foam gives a weight advantage as hull thickness required increases. It doesn't provide any advantage with thicknesses around 1/4". It's because you need to build up the puncture resistence and stiffness.

A tunnel hull will let you run more shallow when under way. Boat you won't sit as high as with a flat bottom when at rest.

For a DIY foam boat, you need to build up a frame/mold and build the panels around it. It takes some talent and practice. You may want to try a simpler S & G boat out of plywood first just to get a taste for what you need to know.

Hope that helps!

[GrapeNutsCereal]

ok kevlar is out. I'm not into vacuum baggin yet. I was looking into building one of the phantom 18 boats (flats boat). If I had a tunnel in one, couldnt I modify the hull length and transom to include float boxes? Would that give the added floatation that I lost adding the tunnel? Sort of like a motor well. I have heard people call them sponsons, and are very common on aluminum boats. I in fact have them on mine, and with a heavier motor the added flotation is great.

[JEM]

You'd have ask the designer about that idea. Generally speaking, those sound like some major structural changes. But never say never!

[JR-Shine]

There is a lot more too it than that - cant just swap foam for plywood. I am doing this with the ph16 (all foam core). There are a lot of differences from the plywood version. I know we have made this offer in the past, and it still stands: if you buy the materials from our store we will redraw the plans for foam core.

Joel

[Corpus Skipper]

Also are there examples of tunnel shapes for a tunnel hull in a flats boat?

One of the best working tunnels I've come across is on Redfin boats. More or less square, but with a curve at the top, and a small channel on either side. Tricky to build in anything other than fiberglass, but I guess some industrious fellow could work something out with PVC, thin panel......

[GrapeNutsCereal]

Originally Posted by JR-Shine

There is a lot more too it than that - cant just swap foam for plywood. I am doing this with the ph16 (all foam core). There are a lot of differences from the plywood version. I know we have made this offer in the past, and it still stands: if you buy the materials from our store we will redraw the plans for foam core.

Joel

I'm very interested in doing this with the phantom 18, i wish there was a phantom 20. I am a fan of bigger boats and think if I was going to build a boat, I should make it with plenty of room for my buddies! I am curious as you are building a ph16 in foam what the materials cost difference might be? I know that in my area a sheet of 4x8 1/4 aquatek is at 24.00 and 1/4 hydrotek is at 35.00.

Would you put a foam ph16 together the same way as a plywood ph16? Or would you assemble the foam panels on a jig of some sort? I like the option the foam core.

Originally Posted by Corpus Skipper

One of the best working tunnels I've come across is on Redfin boats. More or less square, but with a curve at the top, and a small channel on either side. Tricky to build in anything other than fiberglass, but I guess some industrious fellow could work something out with PVC, thin panel......

is it more or less just a ramp with a dome shaped top? I bet you could bend a sheet of corecell with all the squares on it over a plug... Woila. instant tunnel. Then just glass it into the hull bottom and tape it over a few times? hehe, Now Ill write a book "tunnel techniques!" However I saw a boat that advertises that it doesnt need a tunnel?

http://www.marshall-marine.com/20salt.jpg

Notice how high the motor sits? Im sure the water intake would be above the water line! They advertise only a setback plate on their boats? what is going on here? heh i guess i took this way off topic!

[JR-Shine]

Hi Grapenuts,

The all foam version will cost you more, how much more, Im not sure yet. The foam costs about twice the amount of plywood, and you use more fiberglass which equals more resin too. I dont think it is twice as much but I would guess 1.5 times that of an all plywood boat.

If you are serious about doing this, we will calculate a BOM for the foam version so you can see how much the kit would cost.

If you want a bigger boat, the ph22 is the same basic design just bigger. i am building the 16 because I fish with 2 people 90% of the time. A bigger boat just means more weight and bigger engine (which mean more weight again), so then it heavier and more difficult to pole around. Good luck with what ever you decide to do.

Joel

[GrapeNutsCereal]

So a foam cored boat is going to be heavier and draft lower than it being built out of plywood? I guess you gain strength with the thickness of the hull? Wonder what the difference in draft would be?

[JR-Shine]

Originally Posted by GrapeNutsCereal

So a foam cored boat is going to be heavier and draft lower than it being built out of plywood? I guess you gain strength with the thickness of the hull? Wonder what the difference in draft would be?

All things being equal the foam version will be lighter, and draft less.