Moving bulkheads

Discussion in 'Metal Boat Building' started by Squidge, Nov 26, 2012.

  1. Squidge
    Joined: Nov 2012
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    Squidge New Member

    Hi there,

    I'm planning on buying a cruising boat which my partner and I can live on for a year or two while we prepare ourselves to sail... well who knows where.
    We've recently looked at a nice 32 ft steel cutter that seems to tick a lot of our boxes. She's steel for a start, solidly built decks, rig, fittings etc, seems like an all round well thought out ocean cruiser (if a little on the compact side) and most importantly she's within our budget (which I should say now is very limited).
    The only big drawback is that the boat doesn't have a separate double berth cabin, which as we've now both come to appreciate (I wasn't so bothered originally but I've since been convinced) would really be a bonus if we're living on it for an extended period. You may be thinking to yourselves that we're asking a lot from a small yacht but I've gone over the plan dimensions and I think we can solve the issue with a bit of a re-fit. The forward 'chain locker area is quite generously sized, directly aft of that is a relatively large head and wash basin. My thoughts were that we could move the second forward bulkhead aft (re-locating the head further aft and loosing the unnecessary basin), possibly move the chainlocker bulkhead a foot or so forward and there should be enough room for a double berth. All this moving about would be at the cost of one single bench seat berth and a small locker.
    My first question to everyone is that given that the hull is 6mm steel, and the bulkheads appear to be made from ply (approx 10mm), are they likely to be structural and will moving them be likely to cause any problems? - I should just clarify that I won't be removing any bulkheads, simply moving one approx 1 ft forward and the other 2-3 ft aft.
    My second question is that since I would be going to all the effort to do this I was thinking it might be a good idea to make the forward bulkhead watertight. Would this require considerably more engineering and could I use some sort of laminated ply construction to the bulkhead or should it be steel?
    I'll certainly be asking these questions to a surveyor at some stag if we decide to go for this boat but I'm just asking now to get an idea of whether it would be feasible.
    Really would appreciate everyone's suggestions. I've attached a couple of photos of the large forward chain locker and the second forward (head) bulkhead (sorry- my fat arse is blocking most of the shot).
    Cheers,

    Matt
     

    Attached Files:

  2. Ad Hoc
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    Ad Hoc Naval Architect

    Matt

    If the BHD is plywood, and nothing else, this is a 'minor' BHD i.e. not structural. It is simply a partition.

    Thus the only problems would be ergonomic.
     
  3. gonzo
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    gonzo Senior Member

    Considering the thickness of the hull, the bulkhead is not structural. That is a heavily built hull, which can be a bonus if a small speed penalty doesn't matter.
     
  4. michael pierzga
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    michael pierzga Senior Member

    Ive never seen a metal boat with a plywood structural bulkhead. You should be OK with doing as you plan.

    You might put some thought into controlling salt water intrusion from your anchor chain setup into the forepeak.

    Salt in the forepeak is a troublesome maintenance, corrosion , issue with metal boats.
     
  5. gonzo
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    gonzo Senior Member

    Chain lockers are a place where Rhino liner or other plastic coatings of the same type can help. They are made for pickup beds and take a lot of abuse.
     
  6. Squidge
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    Squidge New Member

    Thanks to everyone for the prompt replies. I'm glad to hear that my modifications don't sound too ambitious. I've sketched out a few floor plans which I think will work, I'll try to scan them and add to this thread at some stage.
    Thanks Gonzo - from what others have told me and what I've researched she's relatively heavily built- reassuring in my mind but I suppose there will be an inevitable speed trade-off. As I said though she'll be cruising so speed won't be the primary concern. I guess we'll find out with a sea trial. To my eye she doesn't look like a total tub - I've attached a few photos. Would you guys say she looked like a fair seaboat? - moderate freeboard and overhangs, canoe stern, quite a long fin keel, skegged rudder, 32' length, 10'6" beam, 5'8" draft, 6.5 tn displacement. I like the idea about using the pick-up liner. I actually have an old one lying around in the yard.
    Michael - Good idea, I was thinking of extending the hawse? pipe right down to the chain-well for that very reason and then insuring that any water can drain freely into the bilge from there.
    Does anyone have any suggestions around building a watertight forward bulkhead? I think since I would be going to the trouble of moving bulkheads anyway then I may as well construct a watertight one. But firstly is it even necessary in such a heavily built steel boat? I've heard horror stories of boats striking shipping containers and the like- would this be sufficient to pierce a steel hull? If so, could a GRP re-enforced ply bhd have sufficient strength to hold the possible head pressure of water? Are there any simple formulae for determining the thinkness of a bhd/hatch size for a given compartment volume? Anyone know a good manufacturer of watertight hatches which could potentially do the job?
    So many questions!!!
    Thanks again everyone.
    M
     

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  7. michael pierzga
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    michael pierzga Senior Member

    Difficult to do a correct waterproof bulkhead on a small boat. If the bulkhead is the correct volume it takes up too much interior space.
     
  8. Squidge
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    Squidge New Member

    Can you clarify a little more please? As far as I understood, a watertight bulkhead would be designed to give you some chance of keeping a boat afloat if it was holed at the bow? Would it not then just be a case of creating a compartment in the forward 3-4ft of the bow which was capable of containing any flooding?
     
  9. michael pierzga
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    michael pierzga Senior Member

    3 or 4 ft of space lost in a small boat is allot. A waterproof door in the bulkhead is an option , but its an expensive one.

    The boat Im sailing now has three waterproof bulkheads. The forward waterproof bulkhead is accessible only via a deck hatch. The aft bulkhead protects the rudder bearing and is only accessible thru a deck hatch.
    The engine space is waterproof and uses a waterproof door.

    The result of these bulkheads is added safety but drastically reduced interior volume for living and reduced natural air flow, ventilation, in the boat. .

    In the end its up to you.

    A small crash bulkhead forward is worthwhile.

    Protecting the rudder bearing with a small waterproof containment is also worthwhile.
     
  10. Squidge
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    Squidge New Member

    Thank Michael,

    I like the idea of a watertight compartment isolating the rudder bearing! I think that would be quite simple in this boat - the rudder mechanism has good access from a rear hatch. A bulkhead could be fitted directly in-front of the frame supporting the cockpit sole (see attached photos - the last photo is looking forward inside the compartment towards the rear of the engine). The only problem I could foresee would be a loss of access to the rear of the engine, although you'd have to be an 8 yr old contortionist to feasibly work in that space anyway.

    Would you recommend fitting steel bulkheads where they are intended to be watertight or would some form of ply re-enforced material be sufficient?
    Cheers,
    Matt
     

    Attached Files:


  11. michael pierzga
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    michael pierzga Senior Member

    Well, entire boats are made of wood. A ply bulkhead will work. It may not be the perfect solution but anything that keeps water from flooding the hull and sloshing around, disabling the entire yacht is positive . Your rudder bearing or main engine exhaust could fail at anytime .
    On the best small craft anything that may fail and flood the yacht is kept behind a waterproof bulkhead. The engine room is a classic. If all hull perforations and sea water handling gear is kept behind a waterproof bulkheaded room you have a high level of safety.

    Of course the size of a boat makes many safety details a pipe dream .

    Remember a waterproof bulkhead needs to work hand and hand with a bilge pump.

    With a steel boat avoid any added detail that may promote corrosion by trapping water , limiting ventilation or making visual inspection maintenance difficult.
     
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