Screw Edge Distance - in Fiberglass

There's lots of guidance on structural fasteners in aluminum...

But how about fiberglass? Similar to what cowls are made of. Is there a hole edge distance recommendation? 2.5 D from a #8 screw seems close.

blaplante said:

There's lots of guidance on structural fasteners in aluminum...

But how about fiberglass? Similar to what cowls are made of. Is there a hole edge distance recommendation? 2.5 D from a #8 screw seems close.

Click to expand...

2.5 is probably OK if it has a bonded metal load spreader on one side. more D is better.

It really depends... saying "in fiberglass" is like saying "in marshmallow". Without defining exactly the layup schedule of that fiberglass and what load is going to be applied to the fastener it's not rational to believe any good guidance can be given.

Also, if this is indeed a fastener installed in a fiberglass engine cowl I would strongly suggest you consider using a countersunk screw and a stainless countersunk Tinnerman washer to help in ensuring the screw head doesn't start to eat the fiberglass.