new bulkhead wont fit!!!

[yourmomm]

hi. recent fire destroyed one bulkhead made of 6mm ply and faced on both sides with mahogany T&G panelling (6mm each side). the bulkhead only existed on the port side of the vessel, but was bolted directly onto the boat's oak frame on this side. i could make the new bulkhead onboard but this would be difficult due to space considerations...much easier to make it ashore-problem being, i would need to lift the deck to get it in!! i will therefore obviously have to make it in sections to reassemble once down below-does anyone who has experience of this sort of work know-will this be safe/stiff enough?! many thanks

 

[Blueboatman]

6mm ply doesn't sound particularly structural,even with 2x 6mm t+g glued facings...but then again if its a 6metre cold molded boat it may serve some purpose. The mast may/may not sit on top or it comes through and is keel stepped.
Generally I would say try to speak to the builder,the designer or an owners club/experienced other owner before doing anything ?

You could always make 2 new 6mm ply bulkheads ashore,one being with the outer veneer's grain running vertically and the second one's veneer grain horizontal. You can then cut each into a couple of pieces to get them through the hatch,reassemble each and glue the 2 bulkheads together.What strength you lost by way of your cuts is recompensed by the new double thickness bonded layers...
Whether you then have an extra space to accommodate 6mm t+g on each side is another matter but chances are you will.
Hope that helps.

 

[boatmike]

Presumably you can't get it down the companionway in one piece... Common problem! If I visualise the problem from your post you have a wooden vessel with oak frames (lucky you!) and this was just a half bulkhead on one side of the centreline with none the other side. In this case try to section the bulkhead vertically so that any joints are vertical but the bulkhead is stilll bolted top and bottom. If you can then double the joint on one side, fine. If not it is very unlikely that at 6mm it was intended to be structural anyway. It would of course help to know what boat it is, how big, where the bulkhead is etc. but without knowing this this is the best answer I can give..

 

[yourmomm]

thanks-very helpful thus far-and yes boatmike-you visualise correctly, and your assumptions about my boat and the bulkhead are spot-on-the boat is a 9.8m (12.6m including bowsprit and bumpkin!) one-off curtis and pape iroko-on-oak ketch-this bulkhead doesnt serve much structural purpose aside from general stiffening and separating the main saloon from the rear port cabin-certainly no mast supporting function. thanks all for advice-anymore appreciated!

 

[boatmike]

Excellent! Those Oak frames are the structure and the important thing to maintain is a vertical "pillar" if you can visualise that as near to the centre line as possible. So make the centre section as wide as you can and possibly "double" the vertical as near as you can to the centreline. I have done a similar job on an old pilot cutter by inserting a 2"x"2" hardwood pillar as near to the CL as possible and then infilling with ply. Could be an alternative for you and provide a nice finish for the inside edge of the bulkhead ?

 

[yourmomm]

thanks boatmike-thats super-helpful. i was thinking of doing similar with a supporting hardwood post near the centreline, but had considered a more complicated joint than a simple vertical one....your advice will save lots of time and effort!!

 

[boatmike]

If you have a router you can cut a 6mm slot down the post for the ply to slot into. Also where the ply joins, overlap by an inch or so and use the router to bring the ply down to 3mm. Glue and pin in situ and it's better than new...
Don't bother thanking me again, I am getting embarassed! /forums/images/graemlins/wink.gif

 

[kds]

With a similar problem on an old Atalanta, I routed 3mm off edge for 20mm on each ply piece, so that the two parts lapped over each other and epoxy glued them. No increase in thickness and joint will be reinforced by the veneer each side.
Worked !
Ken