Which sealant for new hatch.

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seumask

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I’m replacing my leaking Houdini forehatch with a new Gebo one. Having hacked out the old one and read the instructions on the new one which say preferably not polyurethane or silicon sealant on account of it being difficult to remove again, not that I am planning to. So you can see I am all of a quandary as to which sealant to use to bed the new hatch in on.
I am thinking Sikaflex 295UV but this is expensive and I think polyurethane. What does the forum suggest, any comments gratefully received.
 
I used Sikaflex 291 when I replaced my hatch cover recently, worked for me...........I don't intend removing it again any time soon..... /forums/images/graemlins/smile.gif
 
Sika 292. You dont need the 295UV, unless you are glueing glass panels where the ligt goes through and shines on the glue. Here you are doing a hatch, so the glue is nicely under the alu frame of the hatch.
3M 5200 is also good, and your chandler/yard probably has another replacement.
You'll need at least a tube for a hatch, be generous. The hinge side of the hatch should be through bolted through the deck, the rest can be screwed into the grp (alltough not recommended).
Apply copious amounts of sealants, place hatch, and start to tighten untill 2mm from the deck, with plenty of sealant being squeezed out. Wait for the sealant to harden and then tighten more. Cut away the sealant when dry with a stanley knife, cleaner than trying to remove it while in its gunk stage.
Don't remove the protective film of the new hatch untill everything is done and the boat is back in the water (don't ask)
 
What I always do is this.I lay a bed of good quality silcone sealant and allow it to cure.One or two hours will do.Then just before fitting I apply a thin coat of fresh slicone and screw the hatch down.The silicone sealeant is very easy to remove later and any that squeezes out can be cleaned with your finger.And it never leaks.
 
Put masking tape around the GRP to catch the sqeezed out Sika. Don't leave on for more than a day - likewise, don't ask /forums/images/graemlins/frown.gif
 
What a timely question. Just finshed the prep work for a new hatch. Has anybody gone the non-setting mastic route recommended by houdini?

I am still undescided between 291 or silicone myself.
 
I had a similar problem a few years ago and had problems getting the UV resist version of Sikaflex. Nobody seemed to stock it locally . I was told shelf life was really poor and that I needed to use an etching solution first (don't know how true that was).

However, I spoke to technical guy for a company making Arbosil. He told me to use Arbosil nnnn (and even gave me a free sample tube). It worked a treat on forehatch and windows and no sign of UV cracking 3-4 years later.

Problem is that I can't remember which number nnnn is I think it might have been 1090. It is still on the boat and tube hasn't gone solid in storage yet so great shelf life. I can check at weekend if you want to try it instead of Sikaflex.
 
At one time I used Sikaflex professionally for all underwater installations of transducers & fittings etc. It was the BEST and shelf live was measured in years until Sika repackaged the product in cheap cardboard tubes and removed the moisture absorbent capsule that used to rattle in the tube base before you opened it. That capsule extended the shelf life, which was snot good for marketing! As Sikaflex is so expensive, having wasted so many of the new type tubes unopened I looked around for another similar product. I found PU18 by Bond-it which is a similar sealant based on the same chemical base and I have used it ever since. It is every bit as good as Sikaflex, but priced better and the tube design is the same as Sika previously used, hence the unopened tubes keep considerably longer than Sikaflex does. I am now very happy again and will not use Sikaflex again having found a superior product at a better price.
 
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Has anybody gone the non-setting mastic route recommended by houdini?


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Quorning (who build Dragonfly trimarans) use this as standard on all their hatches. And I'm pleased that they do. I had the aluminum of one of my portlights fail requiring replacement. It took moments to get the old one out - undo the screws, a quick prise and out it came. The sealant was still gooey despite being years old.

I had a new tube of the same stuff, which I used, but the old stuff looked as though it was still in a suitable condition that it could have been reused.

It's orrible sticky stuff to work with, but seems to do the job, and years down the line makes hatch removal a doddle. It may be fine to say today "I never intend to take this hatch out", but I think they all fail in the end, so using bombproof impossible-to-remove sealant will undoubtably cause problems years later.

And another bonus - as the stuff never sets, part used tubes last for ever too.
 
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