Is there a definitive guide to cabin bulkhead separation?

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Is there a definitive guide to cabin bulkhead separation?

Postby bcollins1234 on Mon Jul 23, 2018 9:08 pm

Hello, happen to me. Sailing away and loving my pocket ship...CRACK! I have a separation of the cabin bulkhead and cabin top. Basically the mast/tabernacle torque (maybe loss shrouds) pulled it away.

Have you experienced this? How did you repair it? Pictures appreciated.

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Re: Is there a definitive guide to cabin bulkhead separation?

Postby Shudoman on Tue Jul 24, 2018 9:27 am

I haven't had this problem nor do I know how to fix it. When I heard that some people were having this problem I added an additional 2 layers of 6" biaxial tape to that joint as I was building. Figure now I could blow up the boat from the inside and not have that joint fail. I Also added 1/2 doubler to the inside of the bulkhead to add some additional rigidity there. I remember seeing somewhere on this site where someone repaired this problem. I tried to search for it but couldn't find.

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Re: Is there a definitive guide to cabin bulkhead separation?

Postby craig on Tue Jul 24, 2018 3:42 pm

Maybe this thread of what you are looking for:

Sorry about your problem. It won't be too hard to fix, thankfully. Just use a few layers of fiberglass to reinforce the joint.

I had an issue there but NOT with bulkhead separation per se. During heavy winds, the tabernacle flexed the plywood enough to cause the (rigid) cleats attaching bulkhead-to-roof to separate from the wood. The bulkhead-to-roof plywood joint, which was reinforced strongly with fiberglass and epoxy, never budged. To fix it the separated cleat, I pushed in epoxy to the joint, then added a plywood doubler and beefed up the bolts and washers to cut down on the flex of the plywood. I also significantly tightened my shrouds.

John Harris has come out forcefully against the need for a doubler to reinforce bulkhead 2. I think he is right. In my case, the shrouds were not tightened down enough - something I didn't appreciate the significance of. Had they been tight, I wouldn't have had the issue. When I finally stopped to consider the physics of it, I realized that the shrouds stop the mast from moving forward (and I guess then push the force downwards). If the mast can't physically go forward anymore, then it can't cause bulkhead separation.

I have since removed the silly triangle part of my doubler, but still use the wider oak plywood piece. I have never once had any more issues there, including in stronger wind conditions than I had when the problem first occurred.
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Re: Is there a definitive guide to cabin bulkhead separation?

Postby DanaDCole on Fri Aug 03, 2018 11:15 am

This has never happened to me (maybe I'm just lucky). My tabernacle is bolted to the cabin, but not glued. The shrouds should be taut, but not overly tight when you raise the mast. Under sail, the windward shroud will be a little tighter (but not like a solid rod) and the leeward shroud will be slightly looser--but not dangling. I know these recommendations are a bit vague, but without measuring instruments integral to the shrouds, what can you do. I can say that when I raise the mast I hear the shrouds snap into place and they feel strong and tight, but again, under sail I see that slight loosening of the leeward shroud. (Next time I'm out I'll strum the shrouds after I raise the mast and publish the note they sound :D .)
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