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Greetings to the 27 community
I recently purchased an early model MkV and among its other needed repairs sports a series of spiffy cracks that run horizontally through the transom/deck joint.
The joint is wide, like 7/8" wide with no mechanical fasteners other than the pushpit bolts and a flag pole stanchion base. I have ground out the crusty bedding material to a point that I can see into the engine compartment and this weekend I will fill her up. Question is what did they use and what should I use to fill the joint. It kind of looks like a thickened polyester of sorts with a slightly pinkish tint to it. My choices are thickened epoxy or 5200. I've never used 5200 and don't know what its final cure is like. Needless to say I'll have to sand and paint the joint once its complete. I'm an epoxy veteran but I'm always looking at different techniques.
Why did it crack? I'm guessing neglect from the previous owner allowing water through the fittings, freeze thaw cycles, friday built boat perhaps, etc. The usual.
Brent Driedger
S/V Wild Rover
C&C 27 MkV #15
Brent Driedger
S/V Wild Rover
C&C 27 MkV #15
;
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5200 is an adhesive, not a filler, and it will not give you a good surface to finish anyway. Epoxy can be used on polyester, and I tend to use epoxy to fill voids and cracks, after appropriate preparation.
But I cannot picture these cracks. Can you post a photo somewhere?
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"New" 1974 C&C 27 Mk II undergoing refit
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1974 Mark II C&C 27
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As Windyday has pointed out, 5200 is an adhesive rather than a filler. If you intend to refinish the exterior surface with new gelcoat, then you should use a thickened polyester material for filling the crack. If you are not going with gelcoat, then use thickened epoxy as it has a greater strength and binding capacity. In either case, use Cabocil (Colloidal Silica) as the thickening agent, as this lends increased strength and holding capacity.
The cracking has probably arisen simply from the fact that the deck and the transom are two different moldings and have different characteristics of flex and expansion. You often see the same thing on boats which have a "scoop" transom in which the deck molding continues over the edge and down the stern to the hull molding. On those boats, the cracks typically occur between the transom and the sides of the hull, rather than between the deck and the transom. This is why Beneteau and Hunter love to cover those seams with big rubber moldings.
If you want a stronger, longer-lasting solution, then get some strips of heavy fiberglass cloth and glass over the joint on the inside before filling the gap. Needless to say, this is both awkward and messy. However, it will provide a strong backing for the filler and help to reduce the likelihood of future cracking. I'm not sure that it is worth the effort, though. Alternatively, you could stuff the gap with butyl caulking (Tremco tape) and then install a number of mechanical fasteners, similar to the seal of your toerail.
Good luck with the resealing process!Marcus from Carriden
Mk III, Hull #847
Marcus Opitz,
Formerly from Carriden, Mk III, Hull #847,
now skippering "Everdina," a 1975 Ontario 32
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If you're looking for bonding capability I'd go with ITW Plexus methacrylate adhesive (MA310 I believe). It's the stuff that's recommended for replacing the cabin windows, which I've done and the stuff works great!.
It's used as a marine adhesive for the hull/deck joint so it's probably exacatly what you're lookinng for. However, I'd check to make sure it can handle the gap you have. Also be aware the the adhesive is a two-part system with a very short working time.
Now I have to go check my boat to see if the transom joint is opening up...
-Pat
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