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Richard,
You'll have to help me a little here, as I'm not yet a builder, but as a
composites design professional (and future builder) I hang out trying to
answer questions such as these. If I understand your design correctly, you
have a glass/epoxy canopy frame which I'm guessing is cored in that region
for stiffness. (If so, what are the approximate core and skin thicknesses?)
There wasn't enough stiffness so the factory devised an additional
reinforcement. That reinforcement is 1/4" foam core with 6 ply skins
tapered athwartships. I don't understand the fore/aft tapering, as it
appears all plies are 5" wide and you're covering a 13" width. Are they
evenly distributed so we really have 2 ply skins? (I understand there are 8
additional plies in the corners but it sounds like these don't really
contribute to the stiffness.)
Regardless of whether your original canopy was cored or not, your best bet
is going to be to add one or two full carbon plies to the OUTSIDE of the
canopy, tapered and faired nicely, plus the same to the inside. If you have
to use 5" material, don't overlap the edges, as the strength is not
necessary, and the overlaps will make fairing difficult. If you have to,
add plies only to the inside, this will increase stiffness only half as
fast. (Meaning you'll have to add twice the total amount of material to the
inside.) If the original canopy was cored, then adding 2 more plies will
give about 2 - 4 times the stiffness. If you have to add it all to the
inside, you'll get 1.5 - 2 times the stiffness. Enough for now. I tend to
get long-winded.

Guy Buchanan Buchanan & Newcomer

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