I own a 1985 First 29 and had the same problem when I replaced the windows last winter. The ‘29 has frameless Perspex window secured by aluminium inserts which fit from the outside. Inside it has aluminium frames with aluminium screws. The insert head OD was 10mm, body OD was 6mm and the thread 4mm. The screw head OD was 9 mm, and crucially this is a close fit in the frame and is covered by a rubber trim.
The local Beneteau dealer initially said they could get new inserts from Beneteau but that never came to anything. They did find some stainless inserts but they were slightly larger. By that time I had had the new windows made and I didn’t want to drill out the holes and risk chipping.
The solution was to purchase M5 x 6 stainless inserts from www.hadlowmarine.co.uk . I pressed these into the frame after enlarging the holes very slightly. These are short enough not to protrude into the window as the diameter would be a tight fit and cause stress cracking. Then I used ordinary M5 pan head screws from the outside. The net result is that the screw and insert combination is the opposite way round to the original. 3 of the windows now have the original inserts and one has the new ones. but from a few feet away you can’t really tell much difference.
I also used the Scapa 3507 bedding tape from the same source. This was stuck to the window, not the hull. I punched small holes so the screws / inserts were a tight fit in the seal. I had previously tried a neoprene seal from Seals+Direct but that looked very blotchy when stuck to the window due to the way the adhesive had been applied to the neoprene.
Make sure you have several screw lengths as it is very difficult to judge even with careful measurement. You may need longer screws initially to pull it together and then shorter ones to finally tighten it up. Good luck.
Guy,
Thanks for the reply. My boat is also a First, a 32 from 1981. My windows have aluminium frames, hence my desire to stick with aluminium fasteners, but it looks as though I may be forced to go for stainless.
Stainless fasteners should be ok if you use some Duralac or zinc chromate jointing paste. Mailspeed or Force4 show it on their web sites. You could also paint the inside surfaces of the aluminium frames with zinc chromate primer from www.lasaero.com/las/30?part=LAS800, who also do Duralac.