Sliding hatch glass bonding help

[raptorheli2]

Hi all,

Got a problem with my new to me boat.

The sliding roof glass bond has failed and now leaking.

Today I removed the hatch (I'll need to do both of them) and in middle of cleaning the old sealant/bonding off at home.

The glass itself has no mechanical attachment to the frame and the glass does carry some loading. The loading it sees is minimal though, the locking handle pulls the glass down onto the hatch deck seal. This means that whatever I use will need to flex.

Would really appreciate if anyone has any advice on what I can use and tips help bond and seal the glass to the alum frame again?

 

[raptorheli2]

Double post sorry

 

[V1701]

I'd use CT1 or OB1, very good adhesive sealants. Use a good quality masking tape and it's quite easy to make a nice, neat job...

 

[Boater Sam]

Agreed, degrease thoroughly with acetone, Let cure for 24 hours before loading. OB1 sets a bit softer in my experience than CT1.

 

[Ian_Edwards]

I've not used OB1, but I have used black CT1 to seal fixed window on my boat, it's a really good adhesive, but in my experience not that UV tolerant.
After couple of years, the surface starts to degrade, and if I run my finger, or a cleaning cloth over it I get black powered coming off it.
I'd look at the Sikaflex Range, there's a range of specifically UV tolerant sealant adhesives, and pick the one that look most appropriate. A little more expensive, but may save you having to do it all again in a couple of years.

 

[raptorheli2]

I've not used OB1, but I have used black CT1 to seal fixed window on my boat, it's a really good adhesive, but in my experience not that UV tolerant.
After couple of years, the surface starts to degrade, and if I run my finger, or a cleaning cloth over it I get black powered coming off it.
I'd look at the Sikaflex Range, there's a range of specifically UV tolerant sealant adhesives, and pick the one that look most appropriate. A little more expensive, but may save you having to do it all again in a couple of years.

The only Sikaflex can see is either 295, which doesn't mention glass bond and there is a 296 which is only for mineral glass-I have zero idea what type of glass is used on the hatch to pick one.

 

[VicS]

The only Sikaflex can see is either 295, which doesn't mention glass bond and there is a 296 which is only for mineral glass-I have zero idea what type of glass is used

The only Sikaflex can see is either 295, which doesn't mention glass bond and there is a 296 which is only for mineral glass-I have zero idea what type of glass is used on the hatch to pick one.

Sikaflex 295UV is for plastic glazing eg Perspex (acrylic) and polycarbonate.

Sikaflex 296 is for all types of mineral glass Surely you know if your hatch is glazed with glass or not.

See the Sikaflex Users Guide Sikaflex Users Guide

and/or the Sikaflex Marine Handbook https://www.toplicht.de/media/pdf/5c/41/56/SIKA_ENRiKlruQPxHNZj.pdf

.

 

[dankilb]

I'd use CT1 or OB1, very good adhesive sealants. Use a good quality masking tape and it's quite easy to make a nice, neat job...

Agreed, degrease thoroughly with acetone, Let cure for 24 hours before loading. OB1 sets a bit softer in my experience than CT1.

As hinted above - not UV stable (beyond a year or two) and can also accelerate crazing in some acrylics because of solvents used to cure polyurethane sealants (inc the non-specialist Sika products which openly advise not using PU for this application).

Just because they’re great to use on the boat, they can’t work for absolutely everything.

In contrast a neutral cure glazing silicon is made for the job, cannot react with any other plastics and give decades of UV stable service.

 

[Ian_Edwards]

As hinted above - not UV stable (beyond a year or two) and can also accelerate crazing in some acrylics because of solvents used to cure polyurethane sealants (inc the non-specialist Sika products which openly advise not using PU for this application).

Just because they’re great to use on the boat, they can’t work for absolutely everything.

In contrast a neutral cure glazing silicon is made for the job, cannot react with any other plastics and give decades of UV stable service.

Can you please suggest a suitable product for a typical yacht hatch glassing replacement, i.e. a Lewmar or similar hatch?

 

[dankilb]

Can you please suggest a suitable product for a typical yacht hatch glassing replacement, i.e. a Lewmar or similar hatch?

If you are opting for a silicon, then Dow 791 (or 895 - the closest to the hallowed 795 used by production builders that is available in the UK). These are sold and certified for installing skyscraper curtain wall glazing apparently.

We used 895 on our acrylic boat windows with zero other fasteners/bonding and I had to remove a 1cm slice from a couple of them after 6 months (insufficient expansion gap in my design/spec!) and they were incredibly well stuck down.

Apparently RNLI lifeboats use the Sika system instead - see post #7 - but when you price that up, inc. the primers etc., it works out a lot more expensive.

Some Lewmar hatches use actual laminated mineral glass, IIRC, so that might change things (no chemical reaction with the acrylic to worry about).

My broader point above is that posters on here of late are very quick to recommend PU sealants unconditionally - when there are in fact a few applications they are less suited for.

 

[vyv_cox]

Can you please suggest a suitable product for a typical yacht hatch glassing replacement, i.e. a Lewmar or similar hatch?

When my frames with toughened glass windows were rebuilt professionally they used a cured silicone product. Apparently the same product is used for windows permanently wet and even submerged. Cannot tell you the name as it was Greek but presumably something similar is available from the big manufacturers.

 

[Macka1706]

Sikaflex 295UV is for plastic glazing eg Perspex (acrylic) and polycarbonate.

Sikaflex 296 is for all types of mineral glass Surely you know if your hatch is glazed with glass or not.

See the Sikaflex Users Guide Sikaflex Users Guide

and/or the Sikaflex Marine Handbook https://www.toplicht.de/media/pdf/5c/41/56/SIKA_ENRiKlruQPxHNZj.pdf

.

SIKA or 3M. both marine versions about equal

 

[raptorheli2]

The hatch is definitely glass but I don't know what specific spec it is.

 

[JFowler]

As Dankilb says use a good quality silicone, as used in commercial glazing systems. Frameless glass walls are bonded with structural silicone. It’s not cheap but you don’t need much.
If the hatch is Acrylic (plastic rather than glass) be wary of using acetone to degrease. It will probably cause crazing.

 

[raptorheli2]

Does anyone have a specific recommend option that is uv stable then? Failing that I will just get sika 296 and primer I guess?

 

[dankilb]

Does anyone have a specific recommend option that is uv stable then? Failing that I will just get sika 296 and primer I guess?

Dow 791 from Screwfix - or Dow 895 (certified for seismic zones!) online.

Otherwise, yes 296 and the primer would be the only polyurethane option I’m aware of.

 

[raptorheli2]

I'll go get Dow 791 tomorrow then.

Thanks for help.