Theres been a lot of discussion on this in the past, run an archive search for testing, or for layup, and see what comes up. Multiple layers of lighter glass are quite a bit stronger than a single layer, especially if you rotate the fiber directions. And youre right, other factors come into play, such as the technique for wetting and squeeging, and the wood strength. Anytime you remove glass, strength is lower. One way to reduce weight is not to put too much epoxy on, squeege it out carefully to get all the excess resin out. But you dont want to see the white glass fibers, then you've squeeged too hard.

Though I havent tried the 2 oz glass, I have tried RAKA tight weave 2.75 oz, and didnt like it because it was harder to get the bubbles out. Two layers of standard weave 4oz is what my Spring Run has on it, and although I would not want to drag it over rocks, I could if I needed to. One of the first times out, I hit a log with a railroad spike sticking out of it. There were three scratches which went down into the first layer of glass, but not into the wood. It's pretty tough. I have a rowboat with three layers of 6oz on the hull, and drpped it fully loaded onto a sharp corner of angle-iron on the trailer. Again, a deep nasty scratch but not into the wood.

: When does the desired lightness of the craft create strength limitations. I
: am sure the answer is rather complicated and dependent on a whole host of
: factors. I have just completed the forms for my son's Grebe. He is 90 lbs.
: I weigh 235 lbs. and will be building an Outer Island next. I would like
: to not limit where we can paddle our kayaks.

: I would love to build as light as possible....especially the OI given its
: size. If I used three layers of 2 ounce cloth, would that be as strong as
: one six ounce layer of cloth. It appears that there would be a weight
: saving due to less epoxy used. Will the use of 3/16 strips for decreased
: weight be less structurally sound than the use of 1/4 strips given both
: have the same glass applications?

: I have taken a look at some of the strip/glass strength ratios in the
: archives and on different sites. I am curious. For those of you who have
: had years of paddling experience with different layups.....have you run
: into problems when playing with strip width and glass layup in order to
: reduce weight.

: The bottom line is...I want a safe and sound boat for my son and I....but
: light too...so....when does the reduction in strip or glass become
: detrimental to the structure of the kayak? I really appreciate your
: thoughts.
: Bob