Sealing deck to hull joint

[cantstopnow]

I have replaced about 60% of the steel rivets that fasten the deck to hull joint on my CP16 with alluminium ones. Now I need to seal the joint and I am not sure which sealant to use. I have a tube of 3M 5200 but I am hesitant to use it. I am wondering if I should have drilled out the rest of the rivets and applied the sealer to the joint and then refastened the whole thing. Argh.... This is the problem with being an amature.


This is the joint prior to cleaning and riviting.

What sealant would be the best?
Should I drill out the rivits apply the sealant and then re-rivit?
There is a heavy vinyl molding that will be installed after the joint is sealed.

[Mike]

I'm no expert but I would leave the aluminum rivets in, and replace any others that have rusted. I'd remove any wax and then sand down the gelcoat on that flange. Then I would tape over the whole joint using epoxy and fiberglass tape. That will ensure the joint is waterproof. I think if you try and coax sealant in there you'll never get it completely watertight. If you choose the right width tape your vinyl rub rail should cover it all.

I've got it worse. I need to apply fiberglass tape from the inside and there is foam headliner and glue all gummed up there. They actually glued the headliner in before mating the hull and the deck, using it as a sealant.

[Tim]

Unfortunately, when reworking a hull-deck joint it is always best to apply the sealant/adhesive before refastening anything. The material needs to be inside the joint as much as possible.

5200 is an appropriate choice for hull-deck joints because you actually want the adhesive quality of the material, in addition to its excellent sealing properties. Most joints that are affixed with flexible adhesives use 5200 at the time of original production. Unfortunately, a lot of poorly-designed and -executed joints end up failing during the boat's lifecycle. Successful repair is often difficult and time-consuming.

I would not glass over an external flange like yours. It will be a less effective repair, and would be difficult to do well. If not done well, there's a high chance of failure because of the natural tendency of the hull and deck structures to "wiggle" themselves apart over time. The natural unevenness of the joint as seen in your picture, as well as the shattered areas, sharp corners, and the flange design all work against an easy fiberglass job. A joint like yours, particularly on a small boat, is not designed to be firmly glassed in place, either; it's success depends upon a flexible adhesive. Generally, it's this flexible adhesive that holds flanged joints together; the fasteners are typically used more to secure the joint during curing, though they play a role in the long-term integrity of the joint as well--but they're not the primary means of security.

Your best hope for rebedding and resealing the joing is to force 5200 as far into the open areas of the joint before resecuring with rivets or bolts. In many cases, resealing in this manner works, depending on your access and the width of the openings, but sometimes there's really not enough space to effectively force the sealant/adhesive into the joint far enough to accomplish much.

In these cases, where the overall geometry of the original configuration may be failing entirely, sometimes the only way to truly repair and rebed the entire joint is to either completely separate the hull and deck (undesirable for many reasons), or to completely reconfigure the joint in one manner or another to allow for a successful repair.

As with so many things, there is rarely hope of a truly easy or quick fix when a significant structural area begins to fail. It will be difficult to succeed at forcing sealant into the joint, but depending on the extent of the open areas, and/or the extent of the remaining sound areas, you might find success. Good luck, in any event!

[Quetzalsailor]

Unless I missed a detail, this is only a 16' boat. I'd hem and haw a bit. Support the hull well. Remove all the rivets, temporarily bolting every couple of feet as you go to hold things in alignment. I doubt the deck would lift off because (surely!) it will have been bonded down to the hull somewhere. Then, unbolting and rebolting as you go around, open the joint; you may have to take a hacksaw blade to it where the bonding is still adequate. Hold maybe 4-6' at a time open with suitable shims, clean the old sealant off as best as you can: perfectly clean, ground clean is the goal (not solventy-sticky). If you could get it 3/8" open, files or a tape-wrapped stick would be quick and easy enough. Repair any damage to the glass at accident sites or bolt holes. Mask the hull and deck to limit the amount of clean-up; 5200 is about the most awful stuff there is and spreads with strings of goo everywhere.

Find a friend or two and work both ways, probably symmetrically is best, probably starting with the transom is best; unbolt a bit, prise the joint open, add copious, continuous couple of beads of 5200 with extra at the rivet holes. Rebolt or rivet at every hole as you go. Work continuously so that the seal is complete, and so that you don't open and shut it squeezing too much goo out. The first gooey messy bit will teach you how much sealant you need.

You work both ways so that the stuff doesn't set up and leave you with an undealed, unbonded length when you get back to the start. The bolts/rivets shouldn't be so tight as to squeeze all the goo out. I suppose you could replace the bolts with rivets after the 5200 has cured, sealing the rivets in.

A larger boat would be tougher; things are thicker, stiffer; there's more connection between hull and deck, bulkheads, cabinetry.

[cantstopnow]

Thanks. This boat loves to sail on the rail so this joint needs to be tight. I will drill the rivets out (they are only alluminium after all), clean, seal with 3M 5200, and refasten in segments.

I am going to keep the mantra in my head " Nothing gets it done but getting it done. "

[radicalcy]

I did the hull to deck joint on my Com-Pac 16 about 3 months ago. I drilled out all of the rivets. I then used a serrated bread knife to cut out all of the old 5200 that had mostly separated from the laminate. That took about 4 hours.
I then riveted the transom corners and the bow peak to keep the deck from sliding around. There is nothing holding the deck in place other than the rivets and the sealant. Oh, and the cockpit drain tubes, which are pvc encased in fibreglass.
With the deck somewhat stabilized, I used a wood rasp and cleaned out all of the remaining sealant, and roughed up the mating sides of the seam. I used two tubes of white 5200 to reseal,wedging the seam open as I worked. I let it set up for a couple of hours, then wiped off the excess along the outside edge, and re-riveted the whole thing. Total time less set up time...about 10 hours.
I applied the 5200 from outside , but it could have been done from inside as the cabin and quarterberths are totally accessible. Wedging the seam open though, I could see and control the amount of sealant used.
Though only a 16 foot boat, these hulls will flex quite a bit. The deck is somewhat thin, and not cored,except along the gunwhale and transom. so the deck will also flex. I don't recommend glassing over the seam. There is a flexible rub strip that fits over the edge, and there isn't alot of room for forgiveness. The original setup used double stick duct tape along the seam, then the rub strip was applied and attached at the corners with machine screws and corner braces.

[Triton106]

Hi Tim and All,

You said that

the fasteners are typically used more to secure the joint during curing, though they play a role in the long-term integrity of the joint as well--but they're not the primary means of security.

As you know the WC Tritons have outward turned flange hull and deck joints. I have been wanting to bolt them together using #10 bolts (1/4 inches are too thick for the small flange) 6 inches on center. Alternatively I can grind down the flange and glass them over like the way Hal Roth described in his books. I am curious which way will be a stronger joint. FYI. I don't have any leak problem (or at least don't think so). I would appreciate your thoughts.

Best regards,

[Tim]

As you know the WC Tritons have outward turned flange hull and deck joints. I have been wanting to bolt them together using #10 bolts Alternatively I can grind down the flange and glass them over like the way Hal Roth described in his books. I am curious which way will be a stronger joint. FYI. I don't have any leak problem (or at least don't think so).

Just out of curiosity, why do you want to bolt your flange together? Are you questioning the overall strength or integrity of the joint? How is the joint currently secured?

If you want to eliminate the possibility of future leaks, as well as reinforce the joint, and don't mind a big job, then removing the flange and fiberglassing well onto the hull and deck is a good way to go. I don't see a lot of advantage to filling the existing flange full of boltholes at this stage. But maybe there's more to it than that.

You say the joint doesn't currently leak. Is there a compelling reason to do anything to it at all? Do you have big plans for the boat that might benefit from the reinforcement? Sometimes, well enough is left alone...and sometimes there are good reasons for change or improvement.

[cantstopnow]

Here is an update on my little CP16 Deck to hull joint progress.

I decided to replace all the rivets and so that I could apply the 3M5200 between the flanges and be assured of a leak free job. The boat needs to have most of the interior woodwork replaced due to rot so if I was going to unattach the deck temporarily why not take it off completely. It is only a 16 foot boat and well suported on the trailer. I would make the interior work so much easier.

So when I started it looked like this,


Then off came the top...



The interior looked bad...







So I removed it...





Water had gotten in from several routes and gotten under the the loose fiberglass epoxy attempt that the PO had made to seal the cement ballast. Fortunately the cement is in good shape with only a minor area that had softened.
I am planning to smooth up the cement surface and seal it and paint it. I do not know what is most effective, I am thinking about a good penetrating masonry sealer and then Bilge Kote? ??

The expanding foam that was injected at the factory provides flotation, insulation and support, I want to fill the entire area under the new plywood with something similiar. Advice welcomed...

[rshowarth]

Below is a link to a friend's solution for a loose hull to deck joint on his Mariner. This is the second Mariner renovation he has completed.

He fiberglassed the joint inside and then cut the flange off and glassed it flush on the outside.

Mariner Forum Post

[Triton106]

Hi Tim,

You wrote:

Just out of curiosity, why do you want to bolt your flange together? Are you questioning the overall strength or integrity of the joint? How is the joint currently secured?

If you want to eliminate the possibility of future leaks, as well as reinforce the joint, and don't mind a big job, then removing the flange and fiberglassing well onto the hull and deck is a good way to go. I don't see a lot of advantage to filling the existing flange full of boltholes at this stage. But maybe there's more to it than that.

The west coast Tritons' hull and deck are glassed together from the inside. They actually did a very good job and that is why I have not had any issues with leaks (at least I am not aware of any). Since I plan to someday sail out of the gate I would like to strengthen the joint. One of the west coast Triton owner (Ray Alsup, Triton #256) mentioned on his website that he bolted hull and deck together to strengthen the joint. Sound like you prefer glassing them together from the outside.

Thanks for your advice.

Regards,

[Tim]

Hi Tim,

You wrote:

Just out of curiosity, why do you want to bolt your flange together? Are you questioning the overall strength or integrity of the joint? How is the joint currently secured?

If you want to eliminate the possibility of future leaks, as well as reinforce the joint, and don't mind a big job, then removing the flange and fiberglassing well onto the hull and deck is a good way to go. I don't see a lot of advantage to filling the existing flange full of boltholes at this stage. But maybe there's more to it than that.

The west coast Tritons' hull and deck are glassed together from the inside. They actually did a very good job and that is why I have not had any issues with leaks (at least I am not aware of any). Since I plan to someday sail out of the gate I would like to strengthen the joint. One of the west coast Triton owner (Ray Alsup, Triton #256) mentioned on his website that he bolted hull and deck together to strengthen the joint. Sound like you prefer glassing them together from the outside.

Thanks for your advice.

Regards,

Bolts or additional glass would strengthen it, but the real question is whether it's necessary or not, I guess.

If the joint is currently fiberglassed well from the inside, and exhibiting no signs of leaks or other weakness, then the bolts really aren't going to add much. Sometimes the cake is already iced.

Outward flanges aren't necessarily very attractive, and they are more subject to damage from docking, pilings, etc. than flush or inward-flange joints. If you need to change the way the joint is configured for your own peace of mind, I'd suggest that overglassing the exterior would ultimately be stronger and more helpful than simply bolting together a flange that really isn't currently adding much to the joint integrity.

Of course, I am not there looking at your joint, so I can't say with any authority that it doesn't require reinforcing. I've not ever seen a West Coast boat in person. But if the interior glasswork is as effective and substantial as that which holds the East Coast decks in place, I wouldn't be concerned.

Note also that your choice of potential method of reinforcing the joint--bolts or external glass--may also depend on how destructive you want to be to adjacent parts of the boat. Clearly, adding bolts to the outward flange would require less work and also less ancillary work to the surrounding areas. Glassing the exterior of the joint is a big job, and will require much grinding, fairing and repainting of hull and deck to properly incorporate the new material. So the work load you ultimately want to undertake will have a lot to do with your choice.

[Tim]

...why not take it off completely...

Why not indeed. Nice job! Now you're really into something.

[radicalcy]

Cantstopnow,
How about cross posting this on the Com-pac owners site? They'd love to see the photos of your 16.
http://www.com-pacowners.com/
Larry Wilson

[cantstopnow]

OK, that is a good idea... now, what was my password to that site? I'm not supposed to use the same password for everything for security, but I can't possibly be the only one having a hard time keeping them all straight.. This could end up on the "Ramblings" section.

I will post it to the Compac site tomorrow. Thanks .

[PGplastic]

How's it going on the interior? Curious how you installed the new berths and sole. Hope it's close to complete. Post pics if you have them.

Paul

[cantstopnow]

I have had very little time to work on the boat. I run a landscape company and this spring has been very busy. I have started back up on the project and expect to finish it up soon. I will post photos soon.

[cantstopnow]

Hi PGplastic,
I continued this at http://www.triton381.com/forum/viewtopic.php?t=2558
because it realy is a project. I will be adding to it shortly...

[PGplastic]

Thanks,
Paul