Birdseye
Well-known member
re bedding the ally frame to the grp - what bedding compound is best?
re bedding a leaky hatch
- Thread starter Birdseye
- Start date
vyv_cox
Well-known member
Over the past nearly 30 years I have rebedded just about everything on my boat, including all 8 windows, two hatches plus a new one I installed. Chainplates, winches, windlass, stanchion bases, mainsheet track, cleats, radar scanner post, organisers, clutches, instrument binnacle, skin fittings, log housing. Every one was bedded on Sikaflex 291, or possibly more recently Puraflex 40. Not a single one has ever leaked.
And forget what you have read about never being able to remove them, it is not a problem, even with lightweight things like window frames.
lustyd
Well-known member
Sika 295 UV would be the one, or 292i. Sika 291i is an interior product and not UV stable. It'll work for a while but will degrade if used outside.
vyv_cox
Well-known member
When I was buying Sikaflex I think the UV and 292 versions did not exist, at least in chandleries. I only bought 291 but now Puraflex 40.
Bobc
Well-known member
Abromast BR Butyl.
salar
Active member
Having tried to seal hatches for many years with Sikaflex with varying levels of success (mostly not), I recently faced the massive dilemma of fixing a 1.9metre window frame with 45 bolts (x2) into my GRP wheelhouse. Having researched the market considerably, given the size of the challenge, I opted for butyl tape from Hadlow Marine. Great service and very knowledgeable advice. http://hadlowmarine.com/Pages/seals-bedding.html And the windows haven't leaked!
lustyd
Well-known member
You could use bubble gum and have it not leak immediately after install, the question is what they're like 5 years later. Having used Sika 291 on a previous boat it'll last about 2 years in sunlight before shrinking and becoming chalky. Sailing Uma used butyl as it's currently trendy but that leaked within a couple of years too. From my perspective, if butyl was as good as people often claim, it wouldn't have been replaced by modern adhesive sealants.
laika
Well-known member
If you're sticking in those perspex windows with no frames, fine, use 292. Hatches with a frame where the sikaflex isn't fully exposed to UV? 291 is fine. I rebedded hatches and a bunch of my windows when I bought the boat over 13 years ago and they're still fine.
salar
Active member
If I was intalling a simple porthole I would agree, a modern sealant will be fine. However when wrestling a 1.9 metre long window weighing as much as I can lift, and having to align it perfectly with the matching hole in the GRP and 45 bolt holes, I can assure you having about 3 metres of exposed gooey sealant to contend with as well would have had only one outcome: a sticky mess! Professional window installers still use butyl tape for a good reason. Anyway you may be right; I'll let you know in 5 years' time.
thinwater
Well-known member
He did not say Sika 291i, which is a different product.
Sika 295 is for GLAZING, not sealing frames.
"Sikaflex®-295 UV has been specially developed for the marine industry, where it is used to bond and seal plastic glazing materials in boats and ships."
Sika 291 is absolutely an exterior product. Sikaflex®-291
PetiteFleur
Well-known member
I have used Butyl tape for years without any problems. When bedding windows I put a ss washer between the frame and grp - this prevents the butyl tape being squeezed out. Only recently I've removed the screws fixing the forehatch to the grp as I had noticed a leak from a couple of these screw holes; so wound butyl tape around the screws and reinserted them and you will see a small bead of butyl pop out inside and it should be sealed.
SvenH
Active member
If hulls without big windows in the sides were any good, big yards would not have added big windows in the hull.
Big windows in the hull are the way to go, we should all follow.
