Re-sealing windows to grp, Sika 291i ?

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PetiteFleur

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Hi everyone, finally got round to removing the two leaking windows for refurbishment. Now cleaned up and new Perspex cut to size, so, I have some Sika 201i tubes - can I use this for both fitting the perspex into the frame and also use it for bonding the frame to the grp coachroof.
The frame is fixed to an internal aluminium frame with selftappers and I will use small washers between the frame and grp so the sealant is not all squeezed out. Or should I use a self adhesive tape for this joint?
I did the other windows years ago and forget what I did........
 
Here's a link to a US company that rebuilds ports. I see the same recommendations from top industry professionals.

http://www.selectplastics.com/index.php/tonys-blog/2-blogs/tonyd/12-sealants

This covers the sealant to bond the plexiglass into the frame.

For sealing the frame to the cabin sides of the boat I would only use butyl tape. Here's a link to an excellent how to on that job.

http://www.pbase.com/mainecruising/nfm_port_lights

Please note that all butyl tape is not equal in quality. I have found in general the gray material is better but I'm not certain that this is a guarantee. Also, if silicone caulk has previously been used to bond the portlight frames to the fiberglass you will have to remove all residue of the silicone to get anything to bond. The silicone oils in the caulk will penetrate into the glass and you will need to sand down into clean fiberglass to insure a good bond.
 
To answer your question rather than going into the usual endless discussions and arguments about which sealant is better or worse, I have sealed my aluminium frames to my GRP coach roof many times using Sikaflex 291, always successfully. Provided you use enough so that it squeezes out all around when the screws are tightened it will be perfectly OK.

My problems, and I suspect yours, is bonding the Perspex, or glass in my case, to the frame. The differential expansion between the two makes long-term sealing a problem. In the end, after countless repetitions of taking the frames out, rebedding the glass, putting it all back only to find it leaked after a short time, I gave up and had it done professionally. They used silicone with a primer, baking the whole assembly in an oven. If your frame divides into two halves that bolt together I think you might find Sikaflex to be acceptable. If yours are more difficult, as mine are, then you may struggle.
 
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If you use a sealant use Sikaflex 295UV if the windows are frameless and the sun can shine through the window at the sealant.
291i is Ok everywhere else.
Don't omit the primer.
Both are expensive.
 
Abormast BR for the frame to GRP seal. Its not too expensive... seals better than anything... is removable later..... clean up with white spirit.
 
skipmac said:
Here's a link to a US company that rebuilds ports. I see the same recommendations from top industry professionals.

http://www.selectplastics.com/index.php/tonys-blog/2-blogs/tonyd/12-sealants

This covers the sealant to bond the plexiglass into the frame.

For sealing the frame to the cabin sides of the boat I would only use butyl tape. Here's a link to an excellent how to on that job.

http://www.pbase.com/mainecruising/nfm_port_lights

Please note that all butyl tape is not equal in quality. I have found in general the gray material is better but I'm not certain that this is a guarantee. Also, if silicone caulk has previously been used to bond the portlight frames to the fiberglass you will have to remove all residue of the silicone to get anything to bond. The silicone oils in the caulk will penetrate into the glass and you will need to sand down into clean fiberglass to insure a good bond.
Click to expand...

Butyl tape is the correct answer-IMHO
 
Thanks everyone. I did ask a local marine window company to quote for just sealing the perspex to the frame - they said they would ring back with a price and I also sent an email with photos and I have not had a reply yet....... So will probably diy as in the past.
After writing this I remembered that I used butyl tape for bedding glass into new windows on our extension a couple of years ago so eventually found it, but it's 12mm wide not 15mm.
Thanks vyv cox for your input, I think I will go ahead using the 291i for both the perspex bedding and frame sealant. I'm guessing that turps, meths or acetone is fine for cleaning any residue but I'll check first on a scrap piece of perspex.
 
vyv_cox said:
Provided you use enough so that it squeezes out all around when the screws are tightened it will be perfectly OK.
.
Click to expand...

Agreed, but do look at the data sheet to see what the recommended thickness of sealant should be. I made the mistake of thinking that the tighter I screwed it down the better the seal; not so - the whole bead seems to need to flex within itself. My layer was too thin and I think the differing expansion rates caused it to unstick and it leaked. It worked when I re-bedded the window with less enthusiastic tightening. Pardon the non-tech language!
 
Scotty_Tradewind said:
As the OP seems answered, can I 'drift the thread' to ask - what's the very best way of removing silicone?

S.
Click to expand...

Chemical methods are unlikely as the stuff resists most things. Mechanical seems to be the way to go, cut, scrape, abrade. Fairly straightforward on smooth surfaces where rubbing with fingers is as good a method as any, much more difficult on rough ones. Best advice is never to use it, although I didn't have a choice with my windows.
 
Rick_A said:
Has anyone used the Aquaseal Mseal 295 for their windows or anywhere else. I know Sika295 is the dogs danglys, but no where seems to keep much stock of it.
Click to expand...

I now use Puraflex 40 from Toolstation. Less than half the price of Sikaflex 291 and seems like just the same stuff. Have used it on windows and on hull fittings, in Greece and UK. Seems to perform well.
 
Scotty_Tradewind said:
As the OP seems answered, can I 'drift the thread' to ask - what's the very best way of removing silicone?

S.
Click to expand...

I posted recently about this particular issue in my "Microplus Update" in the boat building/projects thread. There are accompanying pics which show the process, though it's very straightforward.

Basically, it entails squeezing your item/fitting down to the surface just to the point where the sealant is beginning to squeeze out. Then spray a light mist of water around the join area and tighten things up. This will force the excess out, but it wont stick to anything, as it's all wet, but it does stick where it's supposed to. Cleaning off the excess is then much easier with a paper towel or similar, or just peel it off.
 
jakeroyd said:
If you use a sealant use Sikaflex 295UV if the windows are frameless and the sun can shine through the window at the sealant.
291i is Ok everywhere else.
Don't omit the primer.
Both are expensive.
Click to expand...

I replaced the perspex in my fore deck hatch using the 295UV with primer. A lot of time was spent cleaning off the old sealant, and getting the surface ready.
The primer is ridiculous money, and only has a short shelf life, but still a lot cheaper than a new hatch. Three years on still looks good and no leaks.

I must add that masking off the frame properly makes the job look professional and a lot less messy.
 
Hi KREW2,
Yes I masked it all off to contain the black and runny primer.
Otherwise it could all turn into a mini distater.
Thanks for mentioning the shelf life of the primer , i have some left for my other window but maybe it might be too old when i need to use it.

Ridiculous cost yes , but no leaks :-)
 
To answer the OP's question.
I would be happy to use 291 to fix the frames, but I would use 295 for fitting the perspex.
It's what it is designed for.
 
I've used butyl tape to make a window in a washboard, with SS fixings to hold in place. I found it to be quite a fine balance between tightening enough to properly make the seal without cracking the perspex. I've used CT1 adhesive sealant to rebed a hatch window which has proven very effective & would happily use it again. Others would recommend use of a sealant only rather than an adhesive sealant if there's also mechanical means to hold in place...
 
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