> Poor choice of words on my part. I merely meant that a double 6oz layout
> was stronger than a single 6oz layup (obvious to ALL who post here), but
> the increase in strength was gained with a relatively small increase in
> weight. I did not intend to make comparisons between a double 4oz and a
> single 6oz layup.

> A double 6oz. layup is 25%

> Only tests would tell for sure, but I certainly do agree that the layup is
> the most important factor in panel strength. One observation from this
> test data for other strip thicknesses - a 4oz/1/4"/4oz layup failed
> BEFORE a 4oz/3/16"/4oz layup (150 vs 162 lbs). But a
> 4oz/4oz/3/16"/4oz/4oz layup failed before a 4oz/4oz/1/4"/4oz/4oz
> layup (309 vs 375 lbs). Hmmm, interesting ....

Sorry, my intent was not to crunch numbers. I was trying, poorly, to demonstrate that two equal layups, one a single 4oz. and one a double 2oz., have vast differences in strength.

To sum up my figuring, they would both weigh the same,(9oz.) but the double 2oz. would be nearly twice as strong. (I calculated with 2oz. cloth because a double 2oz. would give the equivelent of a 4oz. single. I wanted to use a double 6oz. and a triple 4oz. but had no data on triples.)

Another interesting point is that being of equal weight, one would assume that materials would be quite similar, and costs would also be close. So with out doubling the price of materials we could double the strength of our kayak.

I also made a poor choice of words. The strength is not in the lay up, it is in the lamination. This may be a case where 2+2 equals 5.

I brought up the idea of triple layups because of my training in automobile fiberglass repair. The data shows that (with polyester resin of course) three layers gives the best strength to weight ratio.

Yes you are right, this is an interesting problem. Ian

> Two light layups are

> The summer is too short to spend it crunching numbers (at least for me),
> so I didn't check your math. An interesting problem for the winter maybe.

> Michael