Hull to Deck Joint

[David O]

Looked like I might have actually gotten the boat ready by the first of May so I started another project on the boat. The hull to deck joint. The boat has always leaked quite badly along the joint so I took the rub rail off and found very little if any caulking at many locations and what I would call a piss poor example of workmanship installing the deck.
The questions now are:
What is the proper way to attach the deck to the hull?
Should the deck be secured to the hull before the rub rail goes on or is the rub rail a structural component of the attachment?
Should the hull be pulled all the way out to the edge of the deck or is ½ gaps acceptable?
What caulking is the best to use knowing that one-day the deck will probably be removed? (Seem pulling engines and decks are quite common in the Donzi world)
Should the screws holding the rub rail extend all the way through the hull?
Help
David

[MOP]

My 2 cents, if you secure the deck to the hull first with counter sunk screws set in teh old holes and drill all new for the rub rail it makes the job alot easier. The outer holes should be slightly larger, just enough so the screws going through don't cause cracking in the gel coat. A little thread contact is Ok but if you drive them through you can start spiders that will eventualy get longer and show up out from under the rub rail. Luckily so far have not done a Donzi but have done a bunch of others. As far as sealer my preference is clear silicone, its not near as tough as 5200 but with a secure joint it does hold and seal very well. The screw do go all the way through but not much, some guys will through bolt what ever they can reach.

[oldLenny]

What is the proper way to attach the deck to the hull?

If it were me I would glass it after you were happy with its "level" in relation to the hull. Even if just a dozen "6" wide tabs, about a foot long, 6 per side" but few ever do this as they want to get these things apart easily again. It WILL make the hull much more rigid mind you. It wil also make it HORRIBLE to separate next time.


Should the deck be secured to the hull before the rub rail goes on or is the rub rail a structural component of the attachment?

Rub rail is the joint in actuality. My 16 was joined to the hull with large diameter countersunk screws first and then the rub rail was put on after and its' screws travelling through both pieces as well. Trick is not to align the inner screws in a location that will interfere with the rub rail screws. Mark them first on the deck before taking off the rail completely. Many here have put ny-locks and threaded "bolts" through this instead of screws.


Should the hull be pulled all the way out to the edge of the deck or is ½ gaps acceptable?

It should be able to easily be pulled all the way out within reason unless there is a "pile" of glasswork somewhere along the perimeter. It is not going to be perfect but 1/2" seeems unacceptable. Keep in mind that when they trimmed the excess glass off these two joints, (flanges) there most probably did not make these perfectly parrallel or consistant. Some variations up and down. Best to make a mickey mouse jig for the correct height (thickness) of the hull lip to the deck lip for the perfect reveal above and below the rail, and travel around the boat pulling up or pushing down (minutely) till it is the same. Run in countersunk bolts and ny-locks to keep it in place until you add rub rail again. Locate holes so as not to be in the way of Taco Metals rub rail holes.


What caulking is the best to use knowing that one-day the deck will probably be removed? (Seem pulling engines and decks are quite common in the Donzi world)

Sikaflex I.M.O.


Should the screws holding the rub rail extend all the way through the hull?

Yes...
On a side note. I would check/replace tank while she is apart if you are separating the thing. The tub will be glassed in about 4-6 locations to the stringers.

Many here will have better answers than this 'cuz they have done it dozens of times.

There are VERY few of the boats around that you have. Especially nice ones.

[David Ochs]

Dave,
Ditto all of the above. I also used Sikaflex,don't even think of using 5200.
A little help from a skinny neighbor kid can help with those hard to get to inside nylocks.
One thing I wanted to add to what MOP and Lenny have said. The original backing of the joint was a joke. I laminated two 3/16" oak strips and topped that with cloth. If you're replacing the rub-rail, consider taking the time lay out exactly where the holes will be. They won't be the same as the old.
Good luck!

[farmer tx]

David,
If you decide to thru bolt your rub rail
DON'T us a cordless screw gun. It will distort
the rail. You can't see the outside if you are
inside.

Later,
Mark

Don't ask me how I know this.

[David O]

Thanks for the info.
I am not familiar with the term Nylock but the best I can tell is, it is a self-locking nut. The type with the nylon in the threads at the end of the nut to keep it from backing off. If I am correct in my thinking then you guys are suggesting, as the much-preferred way, that I through bolt the hull to deck joint. I was hoping a Nylock was something that could be used by one person from the outside. OH WELL
I have looked more closely at the edges of both the hull and deck and both are quite chewed up, cracked, splintered, etc. so for this summer I think it will have to be just one more quick fix if I stand a chance of using the boat this year. Next winter looks like a deck pull will be in order to rebuild the two edges.
Next questions.
Is Sikaflex to strong of an adhesive to use if I am going to pull the deck next winter?
Any suggestions on the best way to clean out the old silicone/adhesive that is in the joint before resealing?
At least when done there will be no part of this boat that I have not worked on. The gas tank was new when I bought the boat supposedly. I was told it is a 50-gallon aluminum tank. It looks like it has been fiber glassed; at least I know it has on top, not sure of the rest of it. It was moved back and now occupies the floor locker between the seats. I have cleaned it and from looking inside it looks in good condition.
Thanks Again for the HELP
David

[MOP]

In the bad areas it would pay to put a strip or two of glass along gthe inside edge, give you more to screw into and the resin will get into your splinterd spots and toughen them up a bit.

[David Ochs]

Dave,
You asked about cleaning out the old sealer in the joint. If you're going to seperate it this winter, I was wondering if you really need to clean it very much. Perhaps you could get some more in the bad areas. I recall that mine had been siliconed, and it was impossible to get off while the lid was on. And still very much a drag to get it all off. I think silicone is a great product, just not for this application. The Sikaflex isn't a super aggressive adhesive. It's been a long time(7-8yrs) since I used it, but I remember at the time the tube indicated that it was good for this purpose. Once all the screws are out, you can run a thin sharp blade through it to cut it loose.