: Ted,

: Thanks for the numbers. In light of some of the responses to your post, it
: might be helpful to stress that the original post/question only dealt with
: the weight comparison between 6 oz glass and 6 (5.7) oz CF (because Jay
: Doorly could not find CF lighter than 5.7 oz). It might also be helpful to
: emphasize that handbook and textbook values of density for fiber
: reinforcements are for the fibers - not for bulk properties of fabrics.

: Sam

Sam,

The point I raised, and it is moot because it is proven to be wrong, was that it was my understanding that CF had a certain strength per weight ratio that favored it to FG. Ted's testing was very useful in that we now know that CF and FG of equal fabric weights will not result in equivalent weight when epoxy resin is applied (4x the weight is hard to explain away). The point I raised was that it may be possible to reduce the weight of the CF, by using reduced weighted cloth (which you are indicating may not be available, I was only speaking hypothetical, though I thought it might come in lighter weights) and still acheived the same strength. Now that Ted has posted the numbers, I was wrong, FG is actually stronger, which means you can use less FG to get the same strength boat as one made from CF, but with a penalty in reduced stiffness.

However, now we have an interesting set of facts. CF results in a stiffer structure, albeit with a penalty in weight and loss of ultimate strength and resiliant strength (a term that I am still unfamiliar with). However, perhaps for those building a FG boat, they can go lighter on the FG layers by using one layer of lightweight CF which would add the stiffness allowing a reduction in the amount of FG used. The builder could use a weight of FG that will add the strength needed, although it would not have provided sufficient stiffness had that weight been used in a FG only boat. Whether that kind of construction results in a weight reduction or not, I don't know, I'm inclined to believe not.

Paul