> Michael, heavier layups are not stronger!!

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%
> heavier and 104% stronger than a single 6oz. A double 4oz. layup is 14%
> heavier and 250% stronger than a single 4oz. Now suppose we had a 2oz.
> cloth. I calculate that a single 2oz. layup would weigh 8.28oz. and have a
> failure at 102 lbs. A double 2oz. layup would weigh 9.02oz. I am not sure
> about the failure point but from the data, lighter cloth gets a higher
> percentage increase in failure point. So, let us conservatively say that a
> double layup would have a 300% increase in strength. This would give us a
> failure point of 306lbs. That means we are 38% stronger than a single 6oz.
> layup and 25% lighter. Now what would happen if we did three layups of
> 2oz. cloth? How strong would we be? Maybe the fact that the strength is in
> the layup will make us realize using 1/8 inch strips is not that big of a
> deal, and has little bearing on the strength of the finished product. It
> is a good way to save weght though, RIGHT GEORGE?

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 ....

Two light layups are
> stronger and lighter than one heavy layup. Three would be even stronger
> and only slightly heavier.

> BTW: if my calculations are wrong, I ain't no engineer and I failed math.

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