Calling all engineers...... Bulkhead question

[Grotto]

So just loving the space inside my 83 without the bulkhead installed ( in the process of refinishing) what would the minimum size shape of the bulkheads need to be to transfer the load to the hull. Let's keep the material wood. I understand I would have to re engineer the. Port settee seat back.

 

[justsomeguy]

the minimum size shape of the bulkheads need to be to transfer the load to the hull.

I'd say the builder's specs plus 10%.
Why bother?

 

[greg_m]

My boat never came with bulkheads at all from the PO. I'm sure it did have because all the signs are there... holes for screws and mouldings with recesses for bulkhead placement. My boat was in pretty poor state. I do agree however that the space/open cabin looks great and very much appealing.

My boat did however come with something unique... the upper shrouds are tied into the actual hull with flat bar stainless steel pieces that bolt in place. You can see my thread.

I was considering the bulkhead structures and the following was my obs:
Port side: Porta potti privacy and Settee back rest.
Stbd side: no reason to have any bulkhead.

In terms of spreading rigging loads then consider bare minimum to tie in under the deck down into the mouldings in order to maintain roominess of open looking cabin.

 

[Grotto]

I actually noticed that in your thread a while ago. I also found a very cool stainless arch someone fabricated which eliminated the compression post entirely. I figured your jaguar was built differently. Being from a different factory. I will use the original bulheads for now, I think the “open floor plan” will be part of my upgrades. A curtain can give you “privacy” but honesty everyone in the boat will be eminently aware if someone is using the head in a 22. I will definitely continue my quest.

 

[Will Gilmore]

I also found a very cool stainless arch someone fabricated which eliminated the compression post entirely.

I like that idea. I've been thinking about something like that for my Mariner. The compression post is in the middle of the 'V' berth.
To address your original question about the need for bulkheads on a Cat 22. I don't know specifically about that boat, but the bulkheads are a great way to aid in the construction and forming of hull shape during the original layup. The need for it to maintain shape after construction probably isn't so important. As a design component, they make useful structures for attaching critical load bearing hardware to, such as chainplates and mast steps, and function as convenient dividers. In a larger boat, I'd be in agreement with

I'd say the builder's specs plus 10%.

, but at only 22', the hull and deck can pretty much stand alone.

-Will (Dragonfly)

 

[JRT]

I'd worry about the deck taking loads it isn't designed for.

 

[markwbird]

What bulkhead? The shrouds anchor to the bulkhead at mid cabin so . . . . .. In my experience the members of this site are very poor mind readers. You have to spell things out for them.

 

[justsomeguy]

but at only 22', the hull and deck can pretty much stand alone.

I don't know the boat either, that's why I went overboard.
"If it's worth doing, overdo it."

 

[vhoisington]

Be sure it is a structural bulkhead. Many of the interior "bulkheads" in the smaller boats are nothing more than a plywood separator. If it was not bonded to the hull by fiberglass but just screwed in, then it is most likely not structural and doesn't do anything more than provide space separation. I know on the Catalina 28 even though it looks like a major bulkhead, the interior plywood separating the v-berth from the main cabin is simply a plywood separator and does not serve any structural purpose.

 

[rpludwig]

why not call the folks at Catalina and get their 2 cents?

 

[Jacktar]

The cat 22 bulkheads are attached to the liner and hull outboard and anchor the shrouds. Kinda structural.

 

[Grotto]

The cat 22 bulkheads are attached to the liner and hull outboard and anchor the shrouds. Kinda structural.

Exactly have to transfer the load from the chainplates to the hard points where the bulkhead attaches. I may be overthinking but the stresses from the chainplate must radiate out from the attachment points. Just don’t know how that looks. Some of the wood cut away may give the bulkhead strength to take the load from the uppers and transfer it through the hull.

 

[Gene Neill]

My bulkheads are only attached to the liner with a few small machine screws, not to the hull at all. The screws are small, and the liner is thin. I give it all very little credit for being structural. If the deck above the bulkhead rotted out, I expect the handful of tiny machine screws in the liner would fail very quickly.

If I were of a mind to eliminate the bulkheads entirely, I would just use an oversized backing plate for the upper shroud and be done with it. In my mind, that's all the bulkhead serves for, structurally speaking: a backing plate.

But I'm not an engineer. I did ride a train once, but I didn't drive it. (They wouldn't let me.)

 

[Grotto]

My bulkheads are only attached to the liner with a few small machine screws, not to the hull at all. The screws are small, and the liner is thin. I give it all very little credit for being structural. If the deck above the bulkhead rotted out, I expect the handful of tiny machine screws in the liner would fail very quickly.

If I were of a mind to eliminate the bulkheads entirely, I would just use an oversized backing plate for the upper shroud and be done with it. In my mind, that's all the bulkhead serves for, structurally speaking: a backing plate.

But I'm not an engineer. I did ride a train once, but I didn't drive it. (They wouldn't let me.)

Interesting, mine are attached with 4 big screws into the liner, just beneath the shelf and two at the bottom of the bulkhead as well as a couple of pretty puny bolts through the fiberglass.

 

[Grotto]

So one of these is NOT original or at least not to this boat same teak oil on both bulkheads. Lucky I really don't care. Mainly refinished to protect the wood. (Till I go to the open floorplan)