Annsofie and Jonas,

Thanks for posting the pictures – that is an interesting solution for holes that have gotten enlarged by repeated drilling out of old rivets.

It looks like you place the threaded backing plates vertically so they each capture two of the Socket Cap Screws up and down, but how do you hold the four backing plates in place inside the furling extrusion when you lower it into the socket?  Do you use an adhesive of some type?  Also, are the backing plates curved to match the curvature of the furling extrusion?  That would be good for load distribution as well as giving a larger surface for adhesive.

I cannot tell from the picture, but are the backing plates made of stainless steel like the A4-70 Cap Screws? This assembly gets a lot of sea water on it and corrosion between the stainless steel and the aluminum is concerning. Since those are just conventional Socket Cap Screws (aka Allen Head Screws), they are readily available in Aluminum which, combined with an aluminum backing plate, might be a good choice to avoid corrosion and retain the "weak link" safety feature of the rivets. (If you want more strength you might go up from 6mm to 7mm AL, rather than the hugely strong SS bolts.)

One could also use bolts with conventional hex heads that do not stick out so far as the cap screws do, thus avoiding any snagging issues.

As for the issue of the cap screws loosening, I should think either a conventional lock washer (split washer) and/or using some Loctite on the threads when assembling would do the trick.

Cheers,

Craig Briggs, SN#68 Sangaris