Window sealing advice please

[KenMcCulloch]

I need to re-seal some of the windows on Border Maid. They are clear plastic material with metal frames on the outside. The windows are bedded into the wooden coachroof sides with what looks like silicone sealant and the metal frames screwed over that with another layer of sealant. I know there's a UV resistant type of sikaflex but using that seems to preclude ever removing the windows again. Are any of the brands of silicone rubber better, or are there alternative materials that anyone can recommend?

 

[alan006]

Its a good question, Ken, I've always used a polyuethane mastic sealant which does a nice job but is very hard to remove later on.
I don't use Sikaflex for 2 reasons. Firstly it is very expensive and secondly the tubes can have sat on the chandlers shelves for several months before you buy them so they sometimes don't flow as well as very fresh ones. I buy my mastic from industrial suppliers whose stock turnover is much faster so the tube is much fresher when you get it.
The trade brand I use is called Purflex but I think there are several equally good. ( costs me about £6 per tube, last time I looked Sikaflex was about £10 per tube).
I'm not a fan of silicon mastic on boats, as far as I know silicon mastic is designed to work where the seal is under compression.

 

[MarAzul]

A couple of boatbuilders I spoke to on a similar matter recommended bog standard clear silicone £2/tube, as long as both surfaces are dry and clean.In fact they recomended it for all deck fittings. Leave the excess silicone that has oused out under pressure and clean off with a sharp chisel once it has gone off. If you have mechanical fixings holding the window to the coachroof you can use a thin shim/washer between the back of the window and the surface of the coachroof to prevent overtightening and removing all the silicone and loosing the seal. Good luck

 

[Seanick]

The problem with silicon, is that it contaminates surrounding varnish/paintwork. Sanding later on will pick up silicon traces and you will get local fish eyes in nthe varnish. Use BUYTL RUBBER for leak free removable windows. Other useless products for this are Sika, oil based mastics, acrylics and polyurethanes.
Arbomast make Butyl, (BR). Available from real chandlers.

 

[MarAzul]

Ah, I forgot to mention I own a plastic boat!