Attached is a very interesting chart made by West Systems which details tests they did on various cedar strip panel thicknesses and fiberglass weights. I believe Nick has this in one of his books and it is also available on the web.

When I started building strippers, I used the standard low cost 6 oz. E-glass. One full layer inside and out, plus a second layer below the waterline. I have always used 3/16" thick strips.

West System also did research on multipul layer glass lay-ups and concluded it is best to apply one layer at a time. They found when two layers are wet-out together they soak up and hold more resin/weight than two individually applied layers.

AND West Systems recently found lay-up strength will be increased if interior glass is applied diagonally, so treads cross the strip joints at 45˚ doubling the number of treads crossing strip joints and wood fiber orientation.

After many years I have learned the strength of 1 layer of 6 oz. glass inside and out is much tougher than I thought.

I paddle in rocky, mussel chocked waters. I weigh 220 and carry a 100 pounds of gear on wilderness trips, run over rocks and have never come close to breaking the glass surface.

For the last 10 years I've used 4 oz. S-glass fiberglass which as strong as 6 oz. E-glass and more abrasion resistant.

Years ago I tried 4 oz. E-glass and found it did not resist dents well. I have not used it since.

I hope this helps in your choice of strip thickness and glass lay-up.

All the best,
Rob

Nothing is as simple
as we hope it will be.
Sufi sage, Mulla Nasrudin