Bulkhead Confusion

[RichP]

When fitting and tabbing a new bulkhead, or partial bulkhead should the bulkhead be flush against the hull and then tabbed in, or should a small gap be left all the way round (but still tabbed in) so that the hull can't 'work' around the stiff spot a bulkhead would create?

The practical part behind this question is, i have taken down the moulded (or am attempting to!) in headlining in my boat and was suprised to find the main bulkhead not tabbed onto the deckhead, instead the moulded lining continues over the top of the bulkhead and continues through the forecabin. I was going to cut it off flush, fill the gap between the bulkhead and the deckhead with thickened epoxy and then tap over it, or would this not be acceptable?

Any help much appreciated thanks!
Rich

[sander06]

That's a good question for The Plastic Classic Forum :: Index, although I'm sure the guys will have some ideas here also. On our boat the bulkheads don't touch the cabin top either. We just filled the space with a flexible caulk and called it good.

[maccauley123]

I know the advice I have heard is the bulkhead should not touch the hull to avoid creating a hard spot. I am doing some bulkhead work and plan to use weatherstripping to create the gap.

[paulk]

Leaving a space is the way to go. This allows the tabbing to spread the load out over a broader area and, as you suggest, avoid hard spots. The Gougeon Brother's book on boatbuilding would be a good source for the latest techniques and ideas.

[sailingdog]

There should be a gap. Filling the gap with a ductile PVC foam is a good way to help ensure the gap stays even and that the tabbing doesn't make too sharp a bend at the joint. Cut the foam in a trapezoidal shape, with the narrow side being the width of the bulkhead and the wider-base side about two-to-three times as wide. This will leave a nice relatively smooth curve for the tabbing to follow.

BTW, the Gougeon brothers are the founders of West Systems IIRC, and information from them can be found at the West Systems website.

[RichP]

So what about the bottoms of bulkheads, obviously unless you can magically suspend them i guess they're going to be touching?
The pvc foam seems like a good idea, although there are some gaps that are almost an inch!

Just finished cutting the deckhead lining flush(ish) with the bulkhead... Covered in fibreglass dust and crap! Just glad i had a decent respirator.

[merc2dogs]

Normally on older thick hulled boats, having the bulkhead touch the hull isn't a problem, with newer thinner hulls you should leave a space.

when using the foam, it only holds the bulkhead up for tabbing, then is just a space filler, all loads are carried by the tabbing and spread out by it to the hull.(so make sure the tabbing is strong enough)

In some areas the tabbing serves merely to hold the bulkhead in place, in others it is an actual structural member.

Ken.

[RichP]

Heres some pictures of the bulkhead in question, before and after grinding... you'll see why it was tricky to get in!

[sailingdog]

If the bulkhead is structurally important, the tabbing should be strong enough to take the loads place on it...or it will break.

[RichP]

Well its never been tabbed to the deckhead in the life of the boat, i'm just planning to do it to stiffen up the boat a bit! Is a 1" gap acceptable to tab over? (Providing its suitably filled)