> I'm not a composite materials specialist and I never could figure out the
> engineering data that was posted here when this topic was first presented.

> It is not particularly intuitive, and there has been a lot of blood spilt
> on this ground over this matter before. One camp says it doesn't make a
> difference. Another camp says it is the ONLY way to go. Again, check the
> archives for the combat reports.

> Here is MY take on the matter:

> As I see it, 2 ounce cloth is not merely 1/3 rd the strength of 6 ounce
> cloth. It must be slightly stronger. Lets say that instead of it being 33%
> as strong as 6 ounce fabric it is 35% to 38% as strong. If this is the
> case, you add up the three layers and you get 105% to 114% of the
> strength. So you pick up a little strength.

> Because each layer of the thinner cloth is woven from finer fibers, it
> will be more likely to stretch, rather than snap under an impact. This
> would make the material more flexible and pliant, as well as more impact
> resistant. It would be more likely to bend under impact, not break.

> With three layers, you have three boundaries to penetrate when you
> encounter a sharp rock. This may increase the ding resistance a bit.

> Think of extremely thick fabric. The warp and weft have to cross each
> other. The thicker they are, the more extreme the change in the fiber's
> direction each time it has to go over or uunder the next cross fiber. They
> are stronger when aligned straighter. The thinner fabrics have more
> material that is straighter because the fibers aren't passing over thick
> crossfibers. They are passing over very thin ones, instead.

> Beyond this I start getting confused by claims and counter claims. What I
> know is that people who have tested the process are happy with it, and
> that if I stock 2 ounce material I'll be able to use as many layers as I
> like to make the glass layer as thick as I like. I have some plans that
> call for using 4 ounce fabric, and other plans tha call for 6 ounce. If I
> get 2 ounce material I get a quantity discount and I can use it for either
> project.

> I may be able to sandwich scraps between two sheets to get the thickness
> of 6 ounce, and have a smooth, easily sandable outer layer, mwanwhile
> using up the odds and ends. This could be a good way to add ding
> resistance to the center of the hull bottom, while using up the odd sized
> scraps. Cutting a rectangular piece of cloth to fit over a mostly rounded
> boat leaves a lot of odd shaped pieces.

> Hope this helps. You should be able to get a better engineering discussion
> of this matter when someone posts a rebuttal to my delusions.

> Paul Jacobson

Paul, I think what George uses is a 3.25 oz 8 harness satin cloth. This is different than the plain weave we all use. It is very tightly woven and takes less epoxy to wet and gives a greater glass to resin ratio. I think this makes a lighter and stronger layup. I wish George would jump in here and explain this to us.

Larry