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mariog
11-09-07, 11:18
I am replacing the perspex side window on my boat, am using the double sided tacked neoprene infill between the coachroof and perspex, then will fill the gap inbetween to make it more waterproof and a smooth nice finish. what type of sealer should I use? should I go for sikaflex or something less hard?

cindersailor
11-09-07, 13:08
Sikaflex will certainly do a good job, but will be a right b*%^!d to to get off again when it comes to doing the job the next time. Think of the poor guy you will be selling the boat to in a few years. Silicone is perfectly adequate and a lot more user-friendly. Note that the adhesive on the neoprene strip is not usually that waterproof so it needs to be sealed in from the elements.

VicS
11-09-07, 13:27
I may be wrong but I think silicone will be disappointing. It will fall away after a couple of years. Sikaflex 291 is the normal adhesive sealant used under fittings etc but there is a UV resistant product, Sikaflex 295 UV, designed for bonding plastic windows. Unfortunately it is only available in black AFAIK

mariog
11-09-07, 14:38
any idea then what sealer I should use the seal the neoprene?

kieronriley
11-09-07, 16:05
do not under any circumstances use silicone ,iwould go one step further and say never use silicone anywhere on a boat .Kieron

cindersailor
11-09-07, 16:17
The adhesive neoprene strip is useful to keep it in place while you are doing the job, but I have noticed that the suppliers indicate that the adhesive is not waterproof. For this reason I just used the plain neoprene held in place with silicone and placed it so that it was a couple of mm from the edge of the perspex and filled the gap with clear silicone, Dow-Corning marine stuff which seems to be pretty resiliant and sticks well. However you will find that the neoprene has a tendancy to shift around as you tighten the screws, lubricated by the uncured sealant. Although I did not try it, it might be worth letting the silicone cure before the screws are fully tightened to combat this. Another tip is to be careful tightening the screws as the perspex is easily cracked. Counter-sunk is neater, but there is a greater risk of cracking, I think pan-heads are probably better from this point of view.

There are some notes on the job at http://www.sealsdirect.co.uk/bbCMS/bbCMSrenderPage.asp?intPageId=9

Boathook
11-09-07, 17:18
I used some 3m silicone? to stick in new perspex in my giot hatches a few years ago. The silicone, perspex and aluminium primer where supplied by the uk dealer. So far no problem and the original was over 20 years !

wotayottie
11-09-07, 17:40
[ QUOTE ]
do not under any circumstances use silicone ,iwould go one step further and say never use silicone anywhere on a boat .Kieron

[/ QUOTE ]

Nonsense. Had a Prout cat which was sealed with marine silicone when built. Never a leak problem in 15 years, and the Blakes through hulls were an absolute bugger to get out because of the silicone adhesion under water. Make sure it is marine grade though - not bathroom sealant - because there are many types of silicone sealant.

IMHO Sika is overrated and consequently over priced. Have used the equivalents from 3M etc with perfectly good results.

mariog
11-09-07, 18:58
There are no screws to hold the perspex in place just the neoprebne and sealant. So I think I need a strong quick drying sealant.

spynappels
11-09-07, 21:43
Might I suggest using Wurth K & D (Klebt & Dichtet), especially the K & D Power. You could probably get it from a local builder or joiner or maybe a hardware merchant. The K & D Power is IMO certified so can be used no problem and is cheaper than Sikaflex and easier to work with when cold.

I am a sales person for Wurth in Ireland, but in a different division, and I will not profit in the slightest if you do get it. I have used it myself on a friends boat and it works very well. It is also available in black, white, grey and brown.

AndrewB
11-09-07, 23:19
[ QUOTE ]
IMHO Sika is overrated and consequently over priced. Have used the equivalents from 3M etc with perfectly good results.

[/ QUOTE ]Sika 295 may be very expensive, but its good. On my boat, it lasted longer than the ali window frames. 3M 5200 is also good but is much slower drying than Sika, so needs greater care to apply. There is a quick-dry version of 3M 5200, but in my experience it is not so good.

davidpbo
12-09-07, 07:49
I rebedded one perspex window using Sikaflex and it crazed, I was new to boats and probably used the wrong type.

For a second window I used a bedding compound from Eagle Boat Windows here (http://www.eagleboatwindows.co.uk/parts.asp)

They were very helpful and the carriage reasonable.