100yr old classic boat bulkheads

I have a 100yr old classic boat that needs a refit on the interior. The main cabin ceiling height is a little on the short side. So i want to open it up more to include the helm & galley. I have two timber posts there and what looks to be two bulkheads.

I believe the posts may be structural but I also think the bulkheads can be removed. The previous owner thought that they cant be. I've attached a photo of the bulkheads and looking for any advice if they can be removed or not or what I should look for here

 

Welcome to the forum. If anyone, just by looking at the photo, tells you what can or can't be done with bulkheads, please thank them sincerely and ignore them.

 

Thanks for the heads up, is there anything special i should be looking for to see if its a structural bulkhead?

 

I honestly don't know what definitive advice to give you. For example, consider the connection to the hull and check the thickness and composition of the bulkhead, the type of wood, and reinforcements, if any. The best course of action would be to have an expert conduct an on-site inspection of the bulkhead and the adjacent structure.

 

In non-monocoque hulls (i.e. clinker or carvel as opposed to FRP or cold molded) bulkheads are very important. They, the ribs, beams, and floors hold the vessel in shape and distribute the load to the planking. As TANSL states, a detailed analysis is needed to move them, just like a detailed analysis was used to place and size them in initial construction

 

I have two sets of bulk heads at the front of the helm and the rear. The boat is 100yrs old so the bulkheads were most likely replaced at some point. I'm 99% certain the front bulkhead is structural. Hearing what you guys are suggesting I think the first step will be pulling the floors out this weekend to see how both bulkheads are connected to the hull and comparing the installation of the bulkheads front & back for any variances. FYI all the bulkheads on this boat are 12mm ply wood

 

I think, it's just an impression, that 12 mm of thickness, without any kind of reinforcement, will not be enough to consider it structural.
But it will also depend on the type of wood and the configuration of the board.
By the way, what a beautiful boat!

 

I will go out on a limb here and advise you to leave those bulkheads alone. The combination of bulkheads and posts certainly don't make the hull weaker,but removing them definitely will.I suspect that the plywood may have been a replacement for tongue and groove panels and it may be a lot less old than the rest of the boat.Consider how the forces are distributed into the hull when the boat is lifted in slings,which most are these days. If you can find somebody who recommends that significant structural components can be removed,try to get him to accept the liablity for the costs of cleaning up the pile of wreckage and building you a replacement boat-nobody will give such an assurance.

 

Bulkheads can be thought of as a diaphragm, and even a thin one can offer great strength depending upon its free span and presence or lack of stiffening structure attached to it, (like cabinetry on one or both sides.
It appears that the bulkhead is supporting the overhead of the forward cabin where the three windows and their frames join together.
I would suppose that without that bulkhead that a sizeable transverse beam would be required to support that junction of structures that have no other means of transferring their vertical loading to the hull.
Me? I'm not so sure I would want only the thin arc of the forward cabin top taking the load that the framework of those windows are transferring down, (and how much the bulkhead is supporting the window structure).
You have a situation, (side view,) where three different horizontal levels all join at different heights, deck/forward cabin/house.
A bulkhead is the simplest way to tie them all together.

 

I will only disagree with @TANSL a bit.

Those bulkheads are bearing points. Simply stated, the lower bulkheads support the end of the lower roof and the structure above. Just from a simple bearing perspective; the end of the lower roof might NOT need to be supported, but the support consolidates and stops movemenr of the lower roof abeam. The upper roof requires the lower sections for same. My hunch is that the cutaway was done during a refit and is already a modification, or someone did a calculation and decided the opening and arch above was sufficient.

Now, where I agree with @TANSL is that removing or altering these bulkheads cannot be authored without a real study by a competant NA.

The other thing you have in front of you seems to be forgotten by you. This vessel made it 100 years! The reason it made it 100 years is abeam movement of the house has been reduced by that very structure. If you want to replace it or open it; you need to make it stronger than existing and not weaker. This means your modification would require more than demolition.

 

The arch above the windows may support the roof, but the bulkheads support the windows and frames under, not to mention consolidation of the two structures. In the absence of the bulkhead, for example, the higher structure could move to port while the lower roof could be moving to starboard. The bulkhead prevents these structures from moving in opposite ways, for example.

I think you need to embrace the bulkhead, appreciate it as a constraint and design within the constraint, or pay an NA to make the existing BH stronger with a small opening like the one on the left.

My hunch also, is that someone also probably altered the walkway head height as it seems rather high, but just a hunch.

 

Perfect, discussion usually leads to clarification of problems and agreement.
I also have to disagree. My opinion is that, with just a photo, it's impossible to determine the consistency, strength, and rigidity of the bulkhead. It could be made of very weak material, covered with a beautiful 0.5 mm thick teak veneer. On the other hand, you have to consider that the strongest beam in the world, if not properly supported at its ends, is useless (except as a decorative element). That's why it's vitally important to check how the bulkhead is attached to the hull structure.
That said, I agree with you on everything else.

 

The OP wants a blessing to remove the bulkhead.
From the simplest view of building structures, not even boats, mind you, the load of the windows and their lower frames require a support. The window frames themselves are stile and rail construction and cannot do it! In home construction, for example, a minimim load carrying wall is required. Typically, this is a 16” o.c. stud wall with a double cap 2x4 on top (a bulkhead!) The window frames are not it, nor are the posts as you examine the windows closely. A home, by the way, encounters far less actual movement than a boat. And so the bulkheads are supporting the windows, Ignacio. This is a basic concept that nullifies the OPs desire to remove the bulkhead.

I would assert that the likely case is someone already removed part of the bulkhead that lowered the headroom of the companionway and they did so to avoid ducking. This was an error. I can make this assessment based on the simple fact the span is a bit much for no added support based on a cursory understanding of building anything. Is it possible I’m wrong? Yes, but not on the balance of my comment, and probably I am not wrong.

This overall ‘assessment’ is based on simple building principles and not on the c.v. or education of a naval architect. I apologize and mean you no disrespect.

Where your assertion is wrong is I can tell him he cannot remove the bulkhead just by looking at it. I do make the assumption the last beam of the lower roof is the same as the others (it appears so in the pic).

Where your assertion is correct, is I am not qualified to offer him a means to remove it.

In building construction, the modern use of laminated lumber has offered us ways to carry loads that did not exist before. So, he could probably find an architect to design a structure that would be smaller than the existing bulkhead, but I’m quite certain he loses the cheat on the companionway. So, for example, let’s say an architect tells him he can provide some laminated structure 2.25” thick and 4” all around under the windows with radiuses on the top. The likely case is the companionway headroom is lowered by proper design.

We must disagree if we must, but he cannot remove the bulkhead. This is easy to assert as the bulkheads support the stile and rail window frame.

 

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

 

Assuming that were true, which it isn't, what does that have to do with this discussion?
Just like a shell panel or any reinforcement, one side of the bulkhead works in tension and the other in compression. Anyone with a basic understanding knows that.
A bulkhead may or may not be a diaphragm. It depends on how the designer conceived it and the structural purpose the designer assigned it.
On that ship, it could be a structural element or a simple room divider. We can imagine things, but we shouldn't make any assumptions.