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Old 09-09-2014
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Cut out centers of bulkheads: possible?

Can we cut out the plywood centers of bulkheads without compromising bulkhead strength? We have considered cutting them out and replacing them with lexan, but would rather have the openings, to increase air flow from bow to stern.

(And no, we will never have overnight guests. And yes, we will curtain off the toilet for privacy, ho ho.)

If you've done it, or can refer me to a thread that addresses this topic, please let me know. Thank you !

NWS
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Old 09-09-2014
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Re: Cut out centers of bulkheads: possible?

You must describe more on how you intend to do this.

A comparably small hole can be cut away, but there must be sufficient left of the bulkhead to stiffen hull & deck.

Also, boats differ. => complete construction needs to be inspected.

/J
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Re: Cut out centers of bulkheads: possible?

The reason I'm asking the question is that we don't know the right way to go about cutting out some of the center of the bulkhead --- and hope some other sailors will share their experience. That is, if anyone has ever done it at all.

(By the way, how big is a "comparably small hole"?)
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Re: Cut out centers of bulkheads: possible?

What size/type of boat are we discussing?
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Re: Cut out centers of bulkheads: possible?

Quote:
Originally Posted by northwestsailor View Post
The reason I'm asking the question is that we don't know the right way to go about cutting out some of the center of the bulkhead --- and hope some other sailors will share their experience. That is, if anyone has ever done it at all.

(By the way, how big is a "comparably small hole"?)
Fair. Let's say it is usually rather safe to cut out a hole of 5"-7" in a buldhead of a 25 ft ++ boat.

We are on a slippery slope. Some bulkheads form an integral part of the boat, contributing to hull stiffnes and so. Others may be designed in another way, where the bulkheads to not contribute very much to stiffness - some bulkheads are mounted in some few points only (I have heard boatbuilders claim this as the egg shell principle, and -"eggs hold together, don't they").

To get any comments of value you must give much more information on boat, construction and all. Maybe there is an owner of a similar one, who has some experience of the bulkheads.

My general comment (apart from all the other here): most boats have too little mechanical strength. I would hesitate before making any big holes in the bulkheads.

/J
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Re: Cut out centers of bulkheads: possible?

We haven't bought the boat yet --- I'm in the process of doing research to find out what kind of compromises and trade-offs we'll need to make. And one of the compromises concerns interior layout.

We are looking for a 27' to 30' coastal cruiser. If we can't open up the interior, we'll need to choose one that already has an open interior --- and probably give up something else we'd like to have in the boat.

(We've created a set of priorities; I'm looking at how we can achieve them).
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Re: Cut out centers of bulkheads: possible?

I think it would be safer and better for resale to pick a boat that already has an open interior. Aft-head layouts have a much more open interior than forward head layouts. If the aft-cabin door on our boat is open you can see from the forepeak all the way through to the transom. There are no big structural bulkheads, the chainplates extend through the cabin to knees on the lower hull.

The only door that we close on the boat on a regular basis is the one to the head.
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Re: Cut out centers of bulkheads: possible?

Yes, we hope that we'll find a boat with an aft toilet --- in part because using a forward toilet in a heavy sea can be very queasy-making --- but also for the reason you give. However, there are aft toilets that are such a huge waste of space, that we'll settle for a forward toilet. We'll be replacing it with a porta-potty in any event.

And that comment may, I think, hi-jack this thread. Let's get back to the question:

Has anyone cut out any portion of their bulkheads and, if so, what did you do and how?
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Old 09-09-2014
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Re: Cut out centers of bulkheads: possible?

If it's ventilation you are seeking then it would be much wiser to purchase a boat that has good ventilation. Many boats are designed for northern climates and have very poor ventilation below. If you are going to use a boat up north, then great ventilation shouldn't be a major concern, because you'll be closed up a lot anyway (think rainy PNW) and fans will be the big thing.
When you start looking at boats, open all the hatches and see what you get. Opening ports in the cabin sides and hull are nice, only if they do not allow water to flow into them, when it rains. An aft cabin boat without ports in the transom will be hot and uncomfortable in the aft 1/3 or so of the bed.
Summer in the tropics (or a hot, still day anywhere) is a tough one to solve, especially when the wind dies and the mosquitoes come out.
When you are sailing, if you are prudent, you won't have hatches or ports open, so you are back to fans.
Drilling holes seems a bit of overkill, when there are some boats out there that have great ventilation, already. Every boat is a compromise, so pick the features that are important to you, and start from there.
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Last edited by capta; 09-09-2014 at 01:07 PM.
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Re: Cut out centers of bulkheads: possible?

Carpenters usually tell plumbers and electricians that they can drill out the center 1/3 of a structural beam without weakening it much, so I'd guess (if I had to guess) that you could make a hole mot more than 1/3 or 1/4 the dimension across the bulkhead and still have it function. Assuming it was strong enough to begin with.

Some of the new Beneteaus, I think the B50? Actually have cosmetic removable bulkheads forward, and they've simply added enough structure against the hull and deck not to need them.

It really would depend on the boat, on what loads are in that area, on the whole build quality, and probably should be signed off with a consult from the maker (if they are still in business) or a marine architect. But if I had to guess, 1/4-1/3 might come out. You might want to sister up an extra 1/2" of material to the rest of the bulkhead to compensate.
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