The trunk cabin to deck joint.

TomY

Alden Forum Moderator
Jun 22, 2004
2,758
Alden 38' Challenger yawl Rockport Harbor
I've pulled off the trim at this joint. Despite rebedding it just a couple seasons ago, water was getting in behind it and lifting the newly applied varnish(frustrating,...) I think I got a bad batch of Boatlife, probably past it's usable date and hence was too stiff to give a uniform "splooge" out all the seams. On top of that, the mahogany is a little chewed up in spots(past screws, a bit of water damage) which doesn't make for a good bedding surface. Also, the gelcoat on the deck along the joint is a little rough.

I thought I'd fix this by getting a smooth bedding surface on both edges by applying thickened expoxy, fairing. Anywhere water can get behind the trim, it can travel fore and aft under the mahogany and come out through loose bedding, screws, even into the cabin if it wicks up past the flange.
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Then I started thinking about what they do with some cabin/deck joints on wooden boats at Rockport Marine(I have friends there who's brains I pick incessantly) They've done some with expoxy filets.

So if I'm going to fill and fair both deck and cabin house damage, why not bond the whole bloody thing together? This joint is never coming apart(unless the cabin is shot), it's screwed and through bolted vertically through the cabinsides, and all screws and bolts I can see have been glassed over as well.

So, I started cutting a chamfer on the edge of the mahogany as I scrapped off some of the gelcoat along the joint area. As a plus, we know well the shaky joint at the cabin front. Due to the angle, there is a long area of cabin that meets the up turned deck flange that will adhere quite nicely. This doesn't address the sagging of the deck forward, but it will help and will not allow that joint to "work", destroying the bedding seal.

I still will need to replace the trim with a conventional bedding compound. I'm not sure I can rely on the epoxy joint to be always watertight(or can I?)That trim/bedding makes sense IF you can get a good application of compound with the right stuff and right conditions(Rockport Marine says this is a crap shoot with bedding wood) which I think I can do successfully now several times burned.

But then,...what about adhering that trim as well to deck and cabin? That might be too far to go but I think I will run it by my friends at RM.

Here's 3 shots showing the worst area aft where some wood needs repair and filling. Next the mid area that is pretty good, showing the scraper I'm cutting the chamfer with. The last is the front side. I have no leaks up here thanks to the slender dutchmen patches I epoxied into saw kerfs cut between the corner posts and cabins.

What do you all think?

Sorry, I can only post one file the site is telling me, I'll try to add the others.
 

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TomY

Alden Forum Moderator
Jun 22, 2004
2,758
Alden 38' Challenger yawl Rockport Harbor
No go on the photos here, I'll try Flikr.

Here's the mid cabin area showing the chamfer I'm cutting with scraper blade and removing gelcoat along deck.
And here's the front cabin joint which is at least an inch deep due to angle. ]
 
May 21, 2008
30
Alden Challenger Portland
Hi Tom,
When I bought Black Star in such a horrible state 4 years ago,I had water leaks everywhere and having to stay onboard as I had no home here being British,I could cover the cabin top but rain water ran along the deck and gave me many wet and uncomfortable nights in bed.
So I cleaned off the cabin to deck joints all around and using 2inch wide glass tape I epoxied this to wood and deck having a 1 inch strip along each,I also ran into the mahogany cockpit surround a couple of inches where the fresh water rot had ruined the wood along its lower edge.This has held up fine and I have done previous repairs on wooden boats I have owned in the UK and been happy with the results.This should allow you to replace your trim if you wish but once you put screws through the glass tape you are risking the integrity of the joint,if you make a neat job with the tape and paint it to match the deck you will not need any trim.
I have since glassed the whole of the coach roof using epoxy as my wood was so bad it was either replace it or that,as long as the mahogany is bone dry it will stick very well,and now having a whole cabin top that is impervious to water ingress no movement takes place,although I have yet to sail the boat and put strain on the cabin top.

Philip Dann
 

TomY

Alden Forum Moderator
Jun 22, 2004
2,758
Alden 38' Challenger yawl Rockport Harbor
Thanks Philip. I hate the idea of putting holes back in the cabin after sealing. But the lower edge wouldn't ever look right now even after repairs, unfortunately. This is why I'm considering placing the trim in epoxy as well. Screws could be countersunk and plugged, a "permenent" fitting(until someone has to remove it :) ) . There may also be a possibility to fashion a finish filet that could be painted as the deck that would raise 1/2" or a bit more? This could also encase fiberglass tape. No holes, done.

With the trim removed for varnish removal, it's easier to wood the cabin at 10 year or so intervals. For that reason, if I replace the trim in bedding, this time I will use oval head screws(left exposed) and Boatlife or similar polysulfide or even something like Dolphinite(or equivalent) that I know I can remove without losing all the trim.

First sign of problems, I'd rebed the reasonably easy to remove trim piece. This would also allow access to the epoxy bond between cabin and deck. Despite 50 seasons, the cabin still looks pretty good.


I have at least a month to let things dry so I plan to get many opinions on this. I'm also looking into a G 10 product from West that mixes a pre thickened epoxy mixture into a caulking tube. It sounds just what I'm looking for, good adhesion and strength but will take some movement.

Once the cabin is beyond repair and needs painting, the decisions are easier. This joint area is for sure the reason the cabins suffer rot if it is not maintained to keep water out.

Thanks for your experience and I'm glad you have things dry below.
 

TomY

Alden Forum Moderator
Jun 22, 2004
2,758
Alden 38' Challenger yawl Rockport Harbor
Making slow progress....

I've cut most of the gain that will take the 1" fiberglass tape, 1/2" up the cabin, 1/2" on the deck. A pull saw taped to a 1/2" block cut an 1/8" + kerf, a chisel to remove the material. I've used a small triangular carbide scraper to take the gelcoat down to form a hollow on the deck for the tape. A real helper has been a homemade sanding block; 1 - 7/16 x 3/4" x 9" cleat and one full sized block with a bevel the small cleat is screwed to. This keeps the cleat at a good angle to bear into the cabin and deck. Sheets are easily replaced with 2 screws.
There are some bad areas to deal with. Here's a spot of rot of which there are several. I'm thinking that above the 1/2" radiused fillet, I'll extend a flat of epoxy up the cabin 1/4" that will be painted. This would cover most of the damage and discoloration.
Here's the forward cabin edge. I'm optimistic this area will especially be improved by this treatment. I don't believe the joint moves, but the deck flexes a bit forward of the joint. This should improve the strength of this problem area with the added epoxy between cabin and deck.
Another showing the sanding block.
Here's what has inspired my to try this. I've been studying several boats at Rockport Marine with an epoxy fillet joint between deck and cabin. Some are done as I'm doing, others have the deck cloth run up the cabin gain and then the fillet over. Here's a larger fillet joint which makes me think running the 1/4" flat(+?) above the fillet, will look fine as it hides most of the rot and discoloration in the problem areas.
Here's another that is way beyond what I will ever achieve, but the same idea.
I thought this was a crazy idea at first until I followed these boats for several years. My friend with one done this way is approaching 20 years on this type of cabin/deck joint, and it looks like new. Further study has shown that this treatment goes back as far as the early 60's when K Aage Neilsen designed some of his boats to be completed this way. Soon I'll be starting the actual glass tape and fillet joint. The good news is, the wood is now bone dry.
 
Jan 27, 2012
12
Tom this is something I've got to tackle as well. Could you sketch out a cross section of what you're planning? I cann't quite fathom how it will look-

We should have the smell of varnish drying through out the house as we start working on pieces in our cellar. Love it!
Thanks, Jon
 

TomY

Alden Forum Moderator
Jun 22, 2004
2,758
Alden 38' Challenger yawl Rockport Harbor
Hopefully this quick sketch will explain Jon. It's pretty simple. Quick kerf cut the saw (taped 1/2" block on its side), fast chisel out of a big 1/16th to and 1/8" deep pocket now 1/2" high. Then a scraper to cut a hollow in the gelcoat(mines pretty bad so it goes down fast), then the sanding tool I cut out to smooth it all out. I'm hopeful this will be an improvement in maintenance and with the coaming repairs, it should be very dry. ]


My plan is to lay the tape in epoxy all around, and then squeeze out a fillet with West 6/10 thickened mixing caulking tubes, finish with a fillet shaped nylon scraper, let dry, fair again, sand, paint fillet and deck, varnish cabin above.

I drew a fillet 3/4" high which would hide a lot of damaged wood. This will be painted the same as the deck up the cabin side. 1" high would hide even more,.... I'm still thinking on how high I could go.

Here's another fillet joint between cabin and deck. In this case, the new glass fabric on the plywood deck was brought up the cabin into a recess all in expoxy. The fillet is finished up about 5/8". Then the wood is taped above, the deck paint goes up to the tape line. Then varnish is brought down from above to tape over the white fillet. That's the visual paint line that has to be straight and fair. As they tell me at RM, the fillet almost disappears to the eye.
 

TomY

Alden Forum Moderator
Jun 22, 2004
2,758
Alden 38' Challenger yawl Rockport Harbor
Whoops! Now I've done it!

I posted the next set of photos of the Cabin trunk to deck joint in the Coaming repair thread. They're both linked so I'll leave as is. Here's the other thread... viewtopic.php?f=1&t=361