Hi. Just joined the forum so apologies if my contribution is too late for Steffenied. I have a 1988 First 35s5 and about 15 years ago wanted to replace the crazed deck windows but the price from Beneteau was about £3000
. I did remove and reseal some of them which was a horrible job. After many years ashore (sadly) I am in the process of replacing the windows amongst other refurbishment. They are made of 10mm thick Perspex and I believe came in 2 shades from Beneteau of green or grey.
Removal has entailed (after removing handrails) cutting the mastic using long bladed sharp knives and lubricating with soapy liquid etc to stop knife sticking. I used thin wooden wedges to hold the freed part of the window away from the frame recess as I progressed. On some bits, parts of the gelcoat came away with the mastic. I spent ages scraping and cleaning the mastic off the frame recesses using various solvents and cleaners, scrapers etc. It is a long and horrible job
. (Careful with some solvents). It is also a good idea to put sheets under the window to catch all the horrible mastic shreds as you are unlikely to get it off in one clean cut.
All the windows (in theory) should have the same profile but obviously different shapes and sizes.
I gave all the windows to a plastics company which produced a mould using the old largest window and from that a new set of windows. (Still expensive but much cheaper than the original Beneteau price).
Close examination reveals that the old and new windows and widow recesses are not identical with slight variation in the curves near the handrail recess which could be compensated by using only mastic but my preference is to use a UV resistant Very High Bonding Acrylic foam tape to bond the windows and then fill the gap around the perimeter with a mastic such as Sikaflex 295UV. This requires a good match of the profile and means building up in low areas and sanding down in high areas and lots of putting on and removing of each window and using a temporary soft foam tape 5mm thick to determine high or low spots. Most VHB tapes are only 2mm thick but I am trying to obtain a 5mm thick tape to fit the gap. I have also been trying to ascertain from tape manufacturers which is the ideal tape to bond Perspex to GRP as some guides are a bit ambiguous and there are many different tapes.
Another job you may need to do before fitting the windows is putting new gel coat around the window recesses where there have been scrapes, scratches or chips and it is much easier to do it before fitting windows.
My progress has been hampered by the wet and windy weather in the West Coast of Scotland so apologies for not having a completed job to report on.
The crazing on the Perspex does not appear to severely affect its strength but spoils the looks of an otherwise beautifully crafted vessel. I intend to have a deck cover/tarp made to protect the windows from UV damage when not being used. Some owners have covers that just cover the 3 windows on each side.
If any UK based 35s5 owners wish to renew their windows and use my moulds, please get in touch.
Also many thanks to other 35s5 owners who have posted information about this classic boat.