strengthen bulkhead on C36?

[John]

As I've posted before, I'm about to change the bulkhead on my C36 MK II. This is the bulkhead that separates the head from the salon and is on the port side of the boat. This bulkhead is made up of two parts. There is a part that goes from the hull of the boat to about two feet in. Then there is the main bulkhead that goes from this point and is four feet wide. It is this part that has to be replaced.

If you look closely at the attached photo, you will see a thin, vertical strip of wood just to the left of the ss chain plate. This is where the joint between the two bulkheads is.

While I'm at it, I was thinking of strengthening this construction by through-bolting a stainless steel strap across the joint of these two pieces and then bolting an identical strap on the other side. I figure this would make the bulkhead in effect one continuous whole. Is there any reason anybody would know of that I shouldn't do this?

It wouldn't cost that much, would be pretty easy to do, and I figure would only make it stronger.

 

[jibes138]

Can you tongue and groove the joint?

First off, why not make the whole bulkhead one piece? Is it a shape that you can't install it? Second option would be to make the joint a tongue and groove joint then use epoxy to glue it together when installed. That would make it equivalent to a solid single piece. If you tried to break it I bet the wood would break before the epoxy joint. A third option would be to make the joint like a series of "teeth" that interlock and then epoxy that together. I saw a guy once replace a half of a hull by doing this on a nonsuch 36. Quite a process.

 

[Barnacle Bill]

I assume you have to replace the bulkhead because moisture has gone through the deck where the chain plate sticks through and it has rotted the plywood. This, of course is preventable if one regularly caulked the opening on the deck (and did so after the rig was tuned and tight or otherwise it would perhaps pull the caulking away if done before tuning the rig). It is in two pieces because plywood comes in 4' widths and so they had to splice or butt the two pieces together. My thought is the piece between the 4' section and the hull is merely a filler piece and has little or no bearing on supporting the chainplate which is bolted to the 4' section. If you want to add a strap across the two pieces, you can, but I doubt it will gain you much and, in my opinion will not look great. Might even detract from the boat when it comes time to sell it.
I would try to keep everything as original looking as possible and install the new bulkhead exactly as it was done at the manufacture.
That's my 2 cents.

 

[Tim R.]

I would use marine ply with no veneer, join the two using a biscuit joiner and then apply new veneer to both sides. You get strength, beauty and better than original construction. Tabbing the bulkhead to the hull would also be good.

 

[Maine Sail]

Call..

Before you make any changes of modifications to the original structure I would call Catalina and ask to speak with Gerry Douglas the designer. He is a good guy and I've spoken with him quite a few times when dealing with bulkhead issues on my C-310.

They have designed this bulkhead to do what it needs to do. Part of what bulkheads on Catalina's do is move slightly due to the nature of the build of the boat. The boats flex and a screwed in bulkhead can move slightly where a tabbed or one piece bulkhead may not move with the hull and could create hard spots or stress points. Before "fixing" what the factory did consult with the boats designer for input! Fixing what you assume the factory did wrong may lead to a worse outcome than repairing it the way it was built. In an ideal world you would have tabbed bulkheads but to have them the hull, I would assume needs to have been designed to accommodate them flex wise.

It never hurts to call and none of us on here designed the C-36 so any advice could actually be dangerous.

 

[soulesailor]

Plywood is available in any length and any width you want. The 4'x8' is just the standard and most used/available size. They could have made this bulkhead in one piece if they wanted to. It must be made this way on purpose...for some reason.

 

[Tim R.]

Plywood is available in any length and any width you want. The 4'x8' is just the standard and most used/available size. They could have made this bulkhead in one piece if they wanted to. It must be made this way on purpose...for some reason.

I would think that Catalina installed this bulkhead before the deck so size would not be a factor. However, we are all assuming this is the original construction. Maybe this bulkhead has been replaced before and the limiting factor would be the companionway.

Soule, I know I have seen your boat around as I do not think there are too many named Vittoria. Welcome to the group. BTW, nice avatar. The sand bar looks a lot like the Gosslings but the mountains look like the Camden hills. Where is it?

 

[soulesailor]

Soule, I know I have seen your boat around as I do not think there are too many named Vittoria. Welcome to the group. BTW, nice avatar. The sand bar looks a lot like the Gosslings but the mountains look like the Camden hills. Where is it?

Thanks Tim. Yeah, not too many VITTORIA's out there. You got the Camden Hills right, that's the view from the White Islands off Vinylhaven's Hurricane Sound.

 

[John]

First off: It would not be possible to get a bulkhead wider than 4' through the hatch opening. Even if it were, it would be a major hassle to remove the smaller, outside portion. And it's not necessary since it is intact. (Yes, as I explained in a previous thread, the bulkhead suffers from dry rot due to the fact that the previous owner did not reseat the deck penetrations and they leaked. I've already taken care of that part of the problem.)

I will contact Catalina to see what they think about my plan. Thanks for the input.

 

[John]

talked with Catalina just now. They said that "it wouldn't hurt" to put a strap across this joint as I was thinking. I also asked about the screws on the bottom of the bulkhead. He said that "typically it is through bolted." I guess this means that at different times they did it differently, because mine is just fixed in place with small wood screws, so this will be my other upgrade. I'll post some photos when I'm finished.