Aluminium Window Frame Sealant

[BB37]

Hello,

Can anyone offer some advice on window sealing and sealant please?

I have just removed an aluminium window frame from a GRP boat because the aluminium/glass seal leaks. It came out easily, and was sealed with a grey substance which had not set, except in a few places on the inside where it was exposed with a large surface area. I don't think it is butyl tape as it had been applied to the threads of the screws holding the frame to the GRP. The sealant had been in place for at least 5 years. It dissolved easily with white spirit.  Does anyone know what this sealant is from this description please?

Also what is the best way to replace the glass/aluminium seal? I have read various articles on this. A rubber U section is one option, but I have read that this should also be sealed with silicone between the glass/rubber and rubber/aluminium, and then there is the troublesome matter of the join in the rubber, which is likely to open up under thermal stress (ie when very cold). I have also read that a complete bed of suitable silicone both sides of the glass makes a good seal. Dow 791 (neutral cure silicone) seems like a good option, being low modulus, and having good adhesion to both glass and aluminium (I have tested this and it is indeed the case as claimed). Has anyone tried this, and have any idea how long the silicone might last? If the rubber U required silicone to seal, why use the rubber at all? 

 

Many thanks,

Ben

[Smoggy]

For the aluminium frame to grp I use self adhesive expaned neoprene tape, easily available in various thicknesses and widths off fleabay, I used 3mm x 20mm and stuck to the frame with the ends overlapped, so far so good and much less messy than trying to wrestle the windows back in with gooey sealant around them.

[OldBerkshireBoy]

I think a product from Soudal was used when my 40yr old leaky windows were refurbed, more of a grey sticky putty out of a tube than silicone and I suspect it doesn`t harden like silicon. Easy to wipe off any over spills as well being a putty like substance.

[WherryNice]

This stuff was given to me by Trevor at Boat Window Repairs when I had my old boat's windows done a few years ago(i took them out and refitted, he did the refurb), it's grey, doesn't set so windows come back out easily but very sticky and can be messy tho I found the Heavy Duty 'Big Wipes' were excellent for cleaning it off.

[Oddfellow]

Arbormast is exactly what you need. 

It is a seriously messy job, but it won't leak, unless you are sparing with it. it cleans up with White Spirit. an LOTS of paper. often best left a couple of days for the overspill to cure a little before cleaning up. You can, actually re-use the overspill IF it isn't full of crap. This stuff dosen't really cure so remains pliable for years, allowing the joint to flex whilst retaining a seal. 

Don't use bear tape as smoggy suggests; it's too unreliable as it needs reasonable compression to work and joints are easy to water to breach. As a pro, I would never use anything but arbomast for windows and many other above-the-waterline deck fittings. 

 

[MauriceMynah]

Is someone using Arbomast an Arbomaster? 

... sorry Andy, couldn't resist it.

[Vaughan]

11 minutes ago, MauriceMynah said:

Is someone using Arbomast an Arbomaster? 

[BB37]

Thank you for your comments and advice. I think I will use the Arbormast as before because it is certainly easy to get the windows out if any further work is needed. 

When I dug the glass out of the frames I found they had been sealed with silicone, which was mostly in fine condition. Interestingly, the seal failure was around where rubber shims had been used to locate the glass in the centre of the U section. These came close to the top of the U, leaving little silicone to provide the seal. If you are thinking of using this technique, I suggest keeping them as deep in the frame as possible. I am going to try putting them back together with just silicone, but working on a flat surface, and supporting the glass at the required height above the outside of the frame. By marking the location of the frame and glass position before assembly I should be able to centre the glass within the frame, and create a complete bed of silicone in the U before assembly. Lots of masking will be required, of course!