sealing troublesome windows! best mastic ..?

[MystyBlue2]

I use puraflex40. Its £5.50 for 400ml tube from toolstation. Really good polyurethane adhesive, excellent for salt water environments and way cheaper than stikaflex and the like for the same sealing and adhering results.

Failing that, A strip of 5mm neoprene gasket around the full window and bolted through with stainless fixings. Would work out more expensive that way though.

 

[PetiteFleur]

I used Butyl tape, but fitted ss washers between the frame and grp where the screws are fitted, sometimes 2 washers If necessary. Butyl is then not squeezed out and preserving a butyl film along the frame. Worked for me.

 

[TactilePaul]

so, window curve is less than the boats, consequently the corners, where all the rain falling above runs past, are not properly sealed, I can't tell whether the expansion/contraction is compromising mastic or the gap is just too great!?
i am going to repair corner area, and maybe bring it out some with filler?, there was water in the cracks, despite there being no rain of late at end of a sunny day!!.
Interestingly, the forward windows are shaped as opposite to these, with top wider than bottom, consequently the water does pass through the edges, as gravity wants to take it away from the side of the frame!! these windows are the opposite, all water falling above window on deack passes round this area, and through it, on both sides, as not a a rhombus sadly!!!
Any help with this would be appreciated.. not sure if the marine superstore has the sealing tape?, their click and collect system is marvelous.. I have match sticks!..

 

[Rappey]

Sealing glass is easy as many sealant/adhesives bond well. Plastic is a different story .
A previous thread showed some tapes that slid out after being compressed.
It has to be upvc foam tape. It can be hardly compressed or completely flattened
I've taken all the frame screws out to do interior lining yet the frame has stayed curved and stuck to the side of the boat.

 

[Mait]

Would EPDM closed cell foam tape work to seal alu-frames to gelcoat surface?

 

[Rappey]

Would EPDM closed cell foam tape work

I certainly have no idea about that. Upvc foam tape does work though and is readily available from any upvc stockist as it's what is used to glaze some window systems.

 

[PabloPicasso]

+1 for butyl tape. Any window or deck fittings can be sealed well with butyl tape. it never goes off so remains flexible, can be reused if needs be. It's also cheap.

I'd avoid sikaflex and other adhesives in this situation.

 

[john0740]

@goldcrest
I noted that initially you were proposing to use an adhesive such that the screws would be 'decorative' ...
Looking at your photo of the window cutout I was wondering whether these screw holes allow proper tightening of the screws, or are the screws slack in the holes?
Retaining screws would need to be sufficiently tight to compress a sealing tape, but not too tight as would over-compress it, if that makes sense.