kevlar canoe build

[zachjowi]

I've got my materials to start building my mold and am looking to buy the materials for the boat. I'm wondering what is strong enough for the hull. I can't find kevlar that is 9 oz so can I just use 5oz and then add 6oz S-glass like in my picture?

The red layers are the S-glass
The black layer is 5oz Kevlar Style 285 is a 17x17, 1140 denier, 5 oz, 4-harness satin [crowfoot] weave, thickness ~10 mils

******Note: Because Raka only sells the 6oz S-glass in 27" width I would probably have to add a layer below the top ceter piece and under th side two, resulting in 4 pieces of S-glass

You can see a picture here

[gonzo]

I think the best answer will come from the designer. It is not possible to even guess since you are not providing enough information about the hull. The lamination drawing shows that the bottom is thicker. Why are you mixing kevlar with glass?

[zachjowi]

Originally Posted by gonzo

I think the best answer will come from the designer. It is not possible to even guess since you are not providing enough information about the hull. The lamination drawing shows that the bottom is thicker. Why are you mixing kevlar with glass?

The S-glass is to give it added strength. I'm trying tomake the boat from the book "Building Your Kevlar Canoe" I've never designed a boat so I was just looking for sme gernerl advice bout weather or not his will crack, etc. It's about 18' long.

http://www.myrabo.com/k-canoe/kevlar2003.htm

[bntii]

I own one of the beautiful VCP kayaks which is laid up with a carbon/kevlar skin.
I can't tell you much about the layup schedule other than it is made very light and stiff by using a combo fabric like this one:

[gonzo]

Why are you adding strength, don't you trust the designer? It doesn't make much sense to add fiberglass to a kevlar laminate unless is to build a core. You are using it as a skin.

[zachjowi]

Originally Posted by gonzo

Why are you adding strength, don't you trust the designer? It doesn't make much sense to add fiberglass to a kevlar laminate unless is to build a core. You are using it as a skin.

The book' design calls for 8.9oz Kevlar, which I can't find. I can only find 5oz. The book also calls for 5.6oz S-glass 30" wide to go on the bottom like i have drawn, but I can only find 27" at Raka so that is why I am asking if going with these alternate materials wil be enough.

Thanks

[gonzo]

Is the glass on the inside? The drawing shows a double layer of red on the bottom and single on the sides. What is the black? It is difficult to answer without knowing which is which.

[zachjowi]

Originally Posted by gonzo

Is the glass on the inside? The drawing shows a double layer of red on the bottom and single on the sides. What is the black? It is difficult to answer without knowing which is which.

There will be a single layer of 60" kevlar on the inside of the boat, ontop of that will be two pieces of 27" S-glass side by side. Potentially I could sandwich those two pieces with 2 more 27" S-glass pieces. If that makes sense. The reason for overlapping is that the boat is 56" at the ceneter and there would be a gap between the two pieces of fabric. Hope this helps.

Red = kevlar
Black = S-glass

[duluthboats]

It is common to sandwich Kevlar between glass in a layup so you don’t sand into the Kevlar during fairing. I would overlap the seam at the center or use tape and leave off the 2nd layer and put it on the inside. If you have to do any fairing on the Kevlar you are in for a real treat.

[gonzo]

Is the kevlar on the inside or the glass?

[zachjowi]

Originally Posted by gonzo

Is the kevlar on the inside or the glass?

Kevlar is the inside layer

[gonzo]

The kevlar with superior tensile and compressive values should be used in the skins. It is an expensive material for a core.

[DCockey]

Originally Posted by gonzo

The kevlar with superior tensile and compressive values should be used in the skins. It is an expensive material for a core.

Gonzo had the same reaction I did. An alternative would be to use a less expensive and potentially lighter core material than Kevlar. But then it wouldn't be a "Kevlar" canoe.

[thedutchtouch]

no, the kevlar should go on the inside. The reason is that the fiberglass is used as wear protection for the kevlar. fiberglass can be sanded smooth, kevlar gets fuzzy. a fiberglass outer layer would allow the smooth external surface to be maintained.

[gonzo]

A high quality kevlar or carbon laminate is very smooth. If you need to sand, then the mold is bad. It is a workmanship and technique problem.