[Michael Burbidge]

I built a fiberglass and resin base about 3/8 thick on the back of the rudder bottom fiberglass part. I'm planning on attaching the light by screwing directly into the fiberglass resin. There is no way to get a nut on the screw.

Would you use a sheet metal screw? Or would you drill and tap for a number 8 screw?

I've done some tests and in 3/8 inch resin it holds either screw very securely. I can't strip the threads in the resin.

Image of the mount and test piece below.

I will use a lock washer between the head of the screw and the light mounting ring.

Thanks,
Michael-

 

[alpinelakespilot2000]

I added flox and resin then tapped for #8, Michael. That plus lockwasher has been good for 120 hours so far.

 

[Rupester]

Floxed and tapped

I floxed the backside full and tapped for the screws. Still tight after 1 yr and 100 hrs.