Glass layup question

[Kez]

Is there a difference in strength between 4 layers of 3 oz cloth and 2 layers of 6 oz cloth in a layup? I would imagine 4 layers of 3 oz cloth would be easier to layup as the thinner cloth tends to conform to the mold better.

What would be a typical layup for a 20 size hull? And how does mat compare to cloth in terms of strength and ease of handling?

Thanks,

kez

 

[Hydro Junkie]

I'd go with the four layers. The weave is finer and doesn't take as much resin to fill it as the heavier weave would. If it's going into a 20 sized hull,the shapes are smaller and, as you said, thinner forms better.

 

[Buddy Benedict]

First start off with thicken epoxy and fill in all the "inside" corners. This will give you sharp corners and less bubbles. I mix mine to a peanut butter thickness. I also agree with using 4 layers of glass.

 

[lohring]

We laid up the XTR-21 (3.5 size) and XT-460 (7.5 size) Leecraft epoxy/glass hulls with one layer of 3 oz then 2 layers of 4 oz cloth. We selectively reinforced the sponsons with carbon fiber and foam for stiffness. We also eventually replaced the wood cross beams with carbon fiber reinforcement. The cowls were one layer of 3 oz and one layer of 6 oz. We tried several pin hole elimination methods. The layer of epoxy partially hardened under the layup worked, but we eventually settled on a spray of epoxy primer as the first layer. We filled all the corners with Cabosil (silica powder) thickened epoxy to eliminate bubbles there.

This gave a very tough hull that was around 1 pound lighter than the polyester hulls. The hulls flex on impact but don't shatter like polyester hulls. I saw an epoxy boat hit the bank during a SAW trial at over 50 mph. All that happened was the paint got scratched. I still have several old epoxy XT-460 hulls. My first epoxy boat set the C mod record in 1999. I finally broke a sponson on it by hitting the retrieve boat. I still have the hull and keep planning to fix it.

Lohring Miller

 

[Kez]

Thanks Guys for your replies. I am laying up a 20 size mono of my own scratch build. The plug and mold turned out quite decent. The plug has a lot of pretty sharp corners (strakes, chine and transom) I will certainly need a lot of cabosil to fill the inside corners.

I will be using polyester resin for the layup so the challenge is to wet out the cloth before the resin set on me. I used to buy this tooling gel coat, which was very expensive and the shelf life was probably a year. I am thinking of using just laminating resin with cabosil and pigment to replace the gel coat. I hope it will work.

I made some radio boxes and fuel tank trays using one layer of 6 oz cloth but it is a little flimsy. I will try one layer of 3 oz plus two layers of 4 oz and see how that turns out.

Thanks,

kez