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- 05/05/2012 at 5:57 pm #4440
third and final question tonight from this newbie… I need to replace the gaskets on my mk1 grp buoyancy tank hatches. Does the gasket go on the hatch or the hull? Any reccomendations on where to get the gasket please.
Also do the screws that the catches attach to need rubber washers to seal them?
Tony06/05/2012 at 7:54 pm #10819Charles MortonMember
Trident will discuss things over the ‘phone and I have always found them very helpful.
As to rubber washers, I have never seen them in chandlers, or marine catalogues. Many years ago I made my own out of neoprene in an attempt solve a leak from a centreboard bolt, without any success.
Marine grade sealant in the holes, and underneath the washers, would be my approach.08/05/2012 at 1:16 pm #10826adminMember
I too replaced the perished seal on the rear hatch of my Mark 2 but could not get a seal to the 5 inch water-gauge standard in the Wayfarer Book.
I took a radical step and decided to put the gasket on the hatch instead of the hull. First I laid a straight edge over the top of the hatch coaming to establish that it was flat and in-plane (ie not twisted), that was ok. then I checked that the hatch was similarly flat, that was ok too.
Of course the hatch cover is cambered so if I want to match the coaming top to the gasket I had to create a flat flange inside the cover, which I did by sticking a 20mm wide piece of polyurethane foam all around inside, then made a jig to sand it back so that the flange was parallel with the hatch edge. The pictures explain better than the words. Some woven cloth and epoxy resin made a hard skin which was filled with microbaloons and epoxy resin (a mixture that a mate of mine tells me is technically known as bog), which is easily sanded fair (using that jig again). Finally I obtained some 9mm thick self-adhesive neoprene foam that I stuck onto the flange inside the hatch cover to create the seal. The pictures are not in the correct order, sorry, some things are too hard.
A little bit of rubbing was necessary to get the coaming edge true. I used smoke pellets in the tank whilie I pressurized the chamber by blowing into a pipe to find out where the leaks were, followed by judicious rubbing down (and occasional filling) to get a good seal. Unfortunately I do not have a photograph with the neoprene stuck on (use bicycle repair adhesive to seal the corners), but if anyone is interested I can take a shot next time I am at the club.
It works![attachment=1:2mt6qxvj]IMG_0004reduced.jpg[attachment][attachment=1]IMG_0010reduced.jpg[/attachment:2mt6qxvj][/attachment]attachment=2]IMG_0014reduced.jpg[/08/05/2012 at 6:19 pm #10832SwiebertjeParticipant
I trick often used is to mitre the neoprene gasket only half way and leave the outer half of material in the the corners uncut. Before glueing the mitre is a V-cut with the bottom of the V in the middle of the neoprene ribbon.08/05/2012 at 6:43 pm #10836tempest51Participant
There are a few foam tapes on the market, the density of the foam is what is important, and what ultimately keeps the water out! I bought tape from Porters a few years ago, and as swiebertje suggested, carefully made an incision to half the width at each corner. The tape has formed a perfect seal and is still in place today. I paid about £30 for sufficient length. Don’t be fooled into buying cheaper tape as it’s a false economy. Always remember to remove the hatch after sailing to relax the tape.
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