100yr old classic boat bulkheads

[rangebowdrie]

Particularly in sailboats with keel stepped masts, a bulkhead is placed close to the mast to take compression loads on the hull. The shrouds try to squeeze the hull sides together.
Without that bulkhead, (or if it's severely cut away,) builders frequently install a tension rod to prevent the hull squeeze from lifting the deck, transferring an athwartships compression load into a vertical tension load, but this entails a "beefed-up" side deck/cabin side/coach-roof structure as the side decks and coach-roof are not in the same plane.

 

[TANSL]

@fallguy,
I haven't explained myself well, or you don't understand me well.
I don't want the OP to remove the bulkhead. What I want is for him or someone knowledgeable to analyze the structure and see if, if the bulkhead is removed, it should be replaced with a structural member to compensate for its absence.
The windows must be supported, of course, but they could be supported, if that were the only problem, by an appropriately sized beam. (One or two people standing on the roof produce more load than the windows, for example.) There are other factors, besides windows, that may require the structural effects provided by a bulkhead. But if that bulkhead is decorative, there's no reason not to remove it.
There is a fairly old construction technique, vault construction, which allows for structures without bulkheads, with only pillars around the perimeter and robust ribs. I'm not saying this is the case with the ship. What I'm saying is, and I agree with you, that the situation needs to be studied and that the OP shouldn't listen to anyone who tells him what he can do without knowing anything more than you or I know.

 

[fallguy]

There is no magic.

The bulkhead supports the window, at a minimum, and cannot be removed without (something) replacing it.

 

[TANSL]

What would you think if I said (but I didn't, or I'm not going to say) that the windows are hung from the strong beam of the cabin roof and supported laterally by strong trusses on the sides. In addition, there are a pair of pillars, one on each side, about a third of the way along the beam, which transmit the loads to the cabin floor?
The vault construction also transmits the loads to the sides, which are the ones that must be the strongest.
There are some other possibilities, which I won't mention, that would allow the bulkhead to be eliminated. Let it be known, once again, that I don't want to eliminate the bulkhead; I just want to explain that there can be much more to it than what one can see in the photo. Structures are not designed guessing what might happen.

 

[fallguy]

The kind of stuff a naval architect may also be concerned with is a window, in of itself, is not really much of a support. And so athwartship motion of the higher superstructure must be reduced or ‘dealt with’.

This gets WAY outside my paygrade, but removing the bulkhead would also lead to failure at the blue arrows. This is why a new structure would probably need to be contiguous across the boat. And while I guessed someone raised the bulkhead; it is possible, the small piece of plywood supporting the middle window is tied to the last beam of the lower roof and sufficient. But removing the posts and bulkheads would require someone to decide how to stop movement at the top of the roof as well as the windows offer little and their construction is not continuous arch or really structural at all.

This is a second strike against removing the bulkhead. Almost certainly, the windows would fail at the arrows and probably in a small chop.

If the original design had made the window rails continuous arches; the window could be more structural, but the stile and rail construction renders that idea mute. These are rather simple principles a decent house builder can appreciate. But he cannot offer the remedy, nor can I.

 

[fallguy]

What would you think if I said (but I didn't, or I'm not going to say) that the windows are hung from the strong beam of the cabin roof and supported laterally by strong trusses on the sides. In addition, there are a pair of pillars, one on each side, about a third of the way along the beam, which transmit the loads to the cabin floor?
The vault construction also transmits the loads to the sides, which are the ones that must be the strongest.
There are some other possibilities, which I won't mention, that would allow the bulkhead to be eliminated. Let it be known, once again, that I don't want to eliminate the bulkhead; I just want to explain that there can be much more to it than what one can see in the photo. Structures are not designed guessing what might happen.

Windows were not ‘hung’ in construction methods used 100 years ago. Jeepers, Ignacio. Your assertion that we cannot tell the OP the bulkheads are required is just wrong. From your own experience, you must be able to appreciate the bulkhead carveout was done to allow sufficient structure to still support the window.

No wonder people argue with you. It is amazing how you are unwilling to accept a minor correction. And to the end, you would misdirect the OP to think some magic allows the removal of support structures.

 

[fallguy]

Bulkheads are diaphragms. They do not normally work in compression, but in tension. They prevent the hull from deforming.

We should be careful referring to the hull in this conversation because this bulkhead, may or may not be needed for the hull, per se, but surely is for the superstructure. The OP comes here looking for holy water, and doesn’t get any from me, but he may misread your comment and believe this bulkhead can be removed as it is not needed to ‘prevent the hull from deforming’.

I’m quite sure you can appreciate how your words could be abused here. And I support your comments with my blue arrows picture by suggesting that very deformation you refer to…

 

[TANSL]

@fallguy , Again, I'm not telling the OP that he can remove the bulkhead.
I think I can accept any correction, if it's solidly based. But honestly, I don't know what you've corrected me on. I don't consider myself corrected at any point.
On the other hand, I believe you and I are expressing opinions, and an opinion doesn't have to be corrected. A statement could be corrected, but an opinion isn't. I, at least, didn't intend to assert anything. You can say I've given an unrealistic example, but nothing more.
With all due respect, I'll leave this conversation now because I believe we can no longer contribute anything useful to the OP, but we might discourage other participants.
Cheers

 

[kapnD]

A single picture dies not provide enough information to even hazard a guess to answer the OP’s question.
An 100 year old boat has most likely been substantially altered from original design over the years, modern materials introduced, and changes made, possibly with disregard to an engineering standpoint.
Can we possibly have a look at other views from both inside and outside the vessel?

 

[rangebowdrie]

Shallow hulled boats of carvel planking, (particularly of bent frame construction along with lots of cabin/cockpit structure and but little real decking,) are surprisingly flexible.
Depending upon length and wave period the hull tries to alternately sag in the middle or at the ends.
This action tries to flex the hull sides in-and-out.
In places such as where the cabin level(s) change, companionway entry, and large hatches are, (like over engines,) it was common to have heavier beams with knees to absorb those stresses, what are called "Panting beams".
They keep the hull sides from "panting" in-and-out, like heavy breathing.