hull to deck joint?

[David van den Burgh]

Our '79 CD36 is thru-bolted every 10-12 inches just as Rich and Melissa describe. It would be interesting to compile data on the models and years that are and are not thru-bolted. I wonder why the variations.

Yes, we know, we had the trim pieces off to rebed some stantions and the midship cleat.
There were plenty of bolts, closer than 12".

But they obviously didn't do every model/boat the same....

Melissa Abato
CD36 Mahalo, #163

rich

per my comments above, i thought the same thing abouot my CD31 until i had to remove some damaged rail - amidships you can't see the underside of the flange until you remove some trim pieces in the cabin

len

mlaNOSPAM@charter.net

[Tom in Cambria]

I was at the boat yesterday and read through the manual about the hull to deck joint. The Cape Dory manual claims that a joint without fasteners is stronger than a joint with fasteners if done correctly. The deck has to fit down inside the hull and be glassed in and the shelf has to be a certain width and so on. They claim that fasteners weaken the water proof integrity of the joint and quote tests to prove it. At least in some years they consciously chose not to fasten the joint with metal fasteners apparently.

[RichMason]

I plan on putting my 1979 CD 28 through some extensive offshore work in the next few years (didn't we all start with that plan ). I already have leaks in several places around the toe rail so it is coming off as soon as I move the boat to NC. Should I add some more thru-bolts where I can get to the joint as an extra safety measure?

[yves feder w1ux]

Same on my CD27 - which was #4 from 1977. Self tapping screws in evidence, not through bolts.

Next time one of us is down at Robin Hood, would be interesting to ask Andy V. about this

Y.

[tony Batchelor]

I have found the comments about the hull deck joint very informative. There appears to have been little or not standard practice as to if and where through bolts were used.

However, the breakdown of the polyester seal between the hull and deck is something many owners will have to face. Particularly those who like me sail exposed waters which test the integrity of the vessel, almost every time I take it out.

So the Question is, Whats the best way anyone can suggest for sealing the joint.

I have thought about having the whole top side lifted, to clean and remake the joint but heck that would be one hell of a job.

So can the joint be adequately sealed by removing the toe rail scraping out whatever can be scrapped and the flooding the joint with what? GRP resin or is some type of polyester better ?

Has anyone already done this job ?

I would welcome advice to this site or my personal email address.
captaintonyb@hotmail.com.

[fenixrises]

Hi all,

I made a basic drawing to give you some understanding of how the hull is laminated. And then how the deck is installed.

This method was very commonly used by many different builders.

The hull mold is prepared initially by being waxed with a special mold release wax. Then the gel coat is sprayed onto the surface followed by a back up coat of gelcoat, usually black.

Next comes the "Skinout" usually one layer of fiberglass mat covered by one layer of fiberglass cloth. These two pieces of f/g are applied together with resin. This is followed by mat and, on older boats, woven roving. This is also applied together in sufficient layers untill the desired thickness is achieved. Newer boats use a different type of fiberglass fabric, usually bi-axial fiberglass and light weight mat stitched together.

Sometimes addtional layers are added in small areas for specific re-inforcement.

After the "Skinout" is applied a seperate part of the hull mold is bolted to an outward turning flange on the hull mold. This piece of the mold is for the deck flange.

This "deck flange mold" is where many of the problems with leaking hull/deck joints originates. Frequently the flange is made horizontal, atwartships. This does not take into account the angle that the deck forms where it joins the hull. The bow and aft quarters of the deck are narrower, so the angle is less.

The difficulty in fixing the leaks cannot be readily done on the out side. Since the deck sits down on the outer edge of the hull and often inside a small verticle lip formed by the "Skinout" of the hull lamination. This makes the outside corner of the joint tight but leaves a gap between the underside of the deck and the top of the hull flange. The joint is then covered, in the case of Cape Dorys, by a wooden toerail and rubrail. Many other boats use an extruded slotted aluminum toe rail.

Cape Dory used a filler material between the hull and deck. I am pretty sure this was a mixture of polyester resin and asbestos powder. It is strong enough but does not give a lot of time to get the deck installed on the hull. This is why large SS sheet metal screws are used to fasten the deck to the hull. Add to this the screws for the toe rail, the outer through bolts on the stanchion bases, the through bolts for the shroud pad eyes and a through bolted T-track for the genoa leads and you have a plenty strong enough hull / deck joint. "BUT" it is a joint that is filled with holes, each and every one just waiting for the chance to be a faucet from the outside to the inside of the boat.

The difficulty in adequately sealing all the holes is the gap between the underside of the deck on the top of the hull flange. Water can enter through the deck in one location then run through this gap to another location and inside the boat. This makes it hard to determine where the water enters the boat.

The best fix is to insure that the joint is totally filled. But this is hard to do because the overhead liner has a nice downturning flange to hide the hull / deck joint and make accessing it a real pain.

Here's a simple drawing




Take care
Fred B

[Tony Batchelor]

The information Fred has supplied is very infomative, Thanks Fred but the question remains, how best to fix the insidious ingress of water.

given that access from inside the vessel is next to impossible due to all the fixtures and fittings not to mention the headliner.

Has anyone out there in Cape Dory land, ever removed the toe rail and any bolts they found, scraped along the joint. flooded the bolt holes and the seam with thickend epoxy and successfully stopped the water getting in?

I'd love to learn if its possible

[genesis]

1978 cd-30 hull #93 is definitly NOT thru-bolted.

[John Nebilak]

For what it is worth here is another data point. I was in the lazerette on Indigo, my CD 36 and noticed the hull to deck joint and was surprised because it was more substantial than other reports that I had read. I found 5/16" bolts (definitely bigger than 1/4" but not sure if they were 3/8") on 4" centers and also the self tapping screws used on the teak toe rail on approximately 8 to 12 inch centers. I think if a CD were to end up on the rocks somewhere and were completely destroyed you would still have that joint intact.