What Should I Use To Seal My Portlight?

[demonboy]

The large portlight in my cabin had been leaking very slightly so I unscrewed the frame from the deck and filled in various cracks and holes with epoxy. I then refitted the frame by Sikaflexing it back into place. Now the leaks are even worse!

When I took the frame off I noticed that it had never been Sikaflexed in the first place. It appeared to have a very thin layer of some putty type material and I got the impression the putty was designed to never fully dry, but that might have been the leak always making it wet. The boat is 20 years old.

What should I be using when refitting the frame? There's a slight chance I didn't use enough Sikaflex as I only have a small amount (you can't buy it in India) but since the stuff spreads out when the frame is put in place, I'm surprised the leak is worse.

Any tips/tricks, bearing in mind I'm in a country that doesn't have marine materials to hand?

 

[Deleted member 36384]

Scapa 3507 Bedding Tape available by mail order from Hadlo Marine. Download their catalogue for upto date price list. This is a good product for sealing. Very helpful as well, drop them an email.

My aluminium frames were sealed with a Sikaflex about 2 mm thickness after tightening mounting screws on the frame. Perhaps you have not used enough Sikaflex.

Hope this helps.

 

[Martin_J]

Between a metal frame and a grp boat I would use a butyl based sealant if the sealant is not intended to actually hold the frame in place. Here in the UK there is a product called Arbormast BR. It is of the type you describe and it has probably lasted the whole 20 years on your boat... It is non setting and when the time comes to change it again it is easy to remove.

You will have to remove all the silicone based sealant beforehand - perhaps use one of those silicone sealant removers.. you wipe it on and then half an hour later wipe all the goo off....

Whichever sealant you use - leave a certain thickness (perhaps a few mm). If you tighten it all down tight and all the sealant squeezes out then there will be no sealant left to fill the gap or to expand and contract with the temperature.

Another point - Silicone sealant will not stick to itself once set. So, whichever way you go you need to clean off all the current sealant.

Hope this helps.

 

[dukes4monny]

There are two places for any framed window to leak:

1/ Between the frame and the hull / deck.
2/ between the glazing and the frame.

I have just rebuilt one of my main cabin windows which I originally thought the leak was between the glazing and the frame, but when I removed the window from the cabin it was clear that the leak was actually between the frame and cabin.
The seals between glazing and frame were in pretty poor shape too (contracted and hardened) and new ones were no longer available, so I found some alternatives which I fitted using some DumDum. DumDum forms a skin but always stays pliable and is non adhesive.
The frame to cabin seal was originally some grey sealer which had gone rock hard. I have replaced this with a neoprene strip which I will also include a bead of DumDum upon final fitting.

A friend of mine who has done a lot of work on various boats suggested DumDum to me because you can actually roll it into a sausage shape which makes it very easy for sealing windows etc.
It's only available in black, which is fine for me because the seals I am using are black. It's relatively inexpensive and a little goes a long way.

Good luck.

 

[demonboy]

Thanks for the replies thus far, they confirm what I suspected.

I'm almost certain that I didn't use enough Sikaflex as I gunged it on and then spread it thin with a spatula. I checked the leak today and the good news is that it is definitely leaking through the seal and not elsewhere more problematic.


I have heard of Dumdum but I'm not sure I can purchase it here. I'll look in to getting it delivered. Arbormast sounds like the ticket though, thanks Martin. Of course my issue here is timing - I have to sort this out before the rains start!

Thank you once again for the replies.

 

[demonboy]

By the way, I came across a silicon gasket-type sealant for engines that does not set. Would this be any good if I can't get hold of a butyl-based product?

 

[alahol2]

I have recently re-bedded my windows on 6mm closed cell neoprene foam tape. Once screwed down, the tape is about 2mm thick. I've tested the windows with a power washer and no leaks. It was much neater and easier than using mastic type jointing.