> I don't think the info is on their web page, but they did publish results
> from panel tests in the Winter 98 (#10) issue of Epoxyworks. They tested
> 12"x12" cedarstrip and plywood panels with various glass
> schedules. Three point bending loads were applied parallel to the grain of
> the cedar on the strip panels and parallel to the face grain on the
> plywood panels. Some of the results (for 1/4" cedar strip panels):

> glass/wood/glass | panel weight (oz) | deflection (in) | failure (lbs)

> 4oz/1/4"/4oz | 9.0 | 0.45 | 150

> 4oz/4oz/1/4"/4oz/4oz | 10.3 | 0.70 | 375

> 6oz/1/4"/6oz | 9.8 | 0.49 | 221

> 6oz/6oz/1/4"/6oz/6oz | 12.3 | 0.58 | 450

> As expected, heavier layups produced stronger panels. Also, there was
> relatively little weight gain in relation to the increase in panel
> strength. For the 6oz layup, a double layer of glass results in a panel
> that is approximately 25% heavier but supports a 104% higher load - twice
> as strong is not twice as heavy.

> But ..... did they build the panels right? (Sorry - I couldn't resist)

> Michael :o)

Michael, heavier layups are not stronger!! 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? 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.