How do I re-bed acrylic into hatch frame?

seanfoster

seanfoster

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The title says it all - I have taken my front hatch off to give it a bit of a refurbish (not sure what make it is but it has seagulls on the knobs).

Generally the frame itself is in good condition, the perspex is in pretty good shape as well, but the original sealant looks like it has been bodged by the previous owner. I've removed all traces of the original, could anyone recommend the correct sealant to use to hold the perspex in the frame? From what i have read so far, a high modulus sealant such as Dow Corning's 791 is right for the job but would like either confirmation of this or other suggestions?

I'm sure this has been asked many times before but a search hasn't come up with anything (or I'm doing something wrong!) Any help would be appreciated!
 
seanfoster said:
The title says it all - I have taken my front hatch off to give it a bit of a refurbish (not sure what make it is but it has seagulls on the knobs).

Generally the frame itself is in good condition, the perspex is in pretty good shape as well, but the original sealant looks like it has been bodged by the previous owner. I've removed all traces of the original, could anyone recommend the correct sealant to use to hold the perspex in the frame? From what i have read so far, a high modulus sealant such as Dow Corning's 791 is right for the job but would like either confirmation of this or other suggestions?

I'm sure this has been asked many times before but a search hasn't come up with anything (or I'm doing something wrong!) Any help would be appreciated!
Click to expand...

As nobody has replied to you post, I suggest you look at this post - http://www.ybw.com/forums/showthread.php?320328-leaking-Lewmar-hatch

When I did mine I also used the purpose made glazing tape to bed it on while holding it in place before actually sealing it with suggested sealant. Hadlow were very helpful and there is lot of good advise on there website. http://hadlo-43547-001.dsvr.co.uk/Pages/Introduction.html
 
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On the other thread mentioned I suggested using PU18. I would say definitely don't use that. Since resealing my hatch after a few months the Perspex popped out of the frame leaving the PU18 firmly bonded to the frame.
PU18 DOES NOT BOND TO PERSPEX. I refitted it again with normal silicone and haven't had any problems since.
 
I did a hatch years ago and used a Wurth sealant intended for windshields.It has a special primer that is applied to both surfaces.As far as I know it's still in place.
 
Spyro said:
On the other thread mentioned I suggested using PU18. I would say definitely don't use that. Since resealing my hatch after a few months the Perspex popped out of the frame leaving the PU18 firmly bonded to the frame.
PU18 DOES NOT BOND TO PERSPEX. I refitted it again with normal silicone and haven't had any problems since.
Click to expand...

Thanks for your reply, I would guess that PU18 doesn't allow for much movement? From reading other articles it is clear that the sealant you use must be able to expand and contract with the perspex which can move something like 5mm per metre over a 20 degree C span, (I'm slightly guessing at these figures as I haven't got the original article to hand) otherwise the sealant will give and water will get in.
 
Sealants used with acrylic and, even more so perhaps, with polycarbonate should be solvent free other wise they they can crack.

They should also be UV resistant

Eg Sikaflex 295 UV
 
seanfoster said:
Thanks for your reply, I would guess that PU18 doesn't allow for much movement? From reading other articles it is clear that the sealant you use must be able to expand and contract with the perspex which can move something like 5mm per metre over a 20 degree C span, (I'm slightly guessing at these figures as I haven't got the original article to hand) otherwise the sealant will give and water will get in.
Click to expand...

..............and that's precisely what happened to me 3 years ago. I used a good sealer/adhesive but the joint just wasnt thick enough and differential movement meant that leaks opened up within a few months. I bit the bullet last summer and did the job all over again........a truly depressing job. So far not a drop inside.
I found an article through this forum from somebody in Australia which I followed in part - he'd been through similar processes.
Decided to avoid any of the tape-based adhesives as i couldn't find one thick enough to deal with movement
 
If you ring up Eagle windows, they can probably supply a kit with all the sealants etc you need, plus instructions. Not expensive, and worth every penny.
 
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