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 Making the strongest bulkheads possible...

I started with the plans I had and from them fabricated a pattern with cheap bracing ply. This was used to trace the outline for the multiple parts and to verify the correctness of the measurements. Only one of the bulkheads was wrong (Back web of the back beam) but it would have been a terrible waste of time and materials if I hadn't done it this way so, for that reason alone, the patterns were well worth it.

   Here we go.... This is one side of my main beam or mast bulkhead. The parts are cut from 9mm 7 ply marine plywood. The joints are staggered! This is one of the reasons I favoured the layered approach. I didn't like the scarfing idea... too sloppy. I think staggered butt ends will be stronger. The parts were all set up and coated twice with "Bote-Cote" epoxy with their additive for penetrating and preserving timber. I let it go until it was firm but still a bit tacky. I never had a problem with this ply outgassing except if it was caught in direct sunlight. This photo is near sunset though. Took all day to set the coats of epoxy.


With about a kilo of glue mix....

   Get the edges covered..
   and joined...
   all of em...
   then start spreading the lot...
   I used a brush and a squeegee to spread it..
   And now the other halves..
   And start nailing in "locating pins" when you are sure you have the panels joined securely...
   again, watch the edges...
   Then I threw every heavy thing in sight and drove in a few screws as well.
   This is what it looked like the next morning.
   Clean up the edges a little and the overflow of glue by the joints.
  And she is ready to laminate. 
   First I got all my materials ready and cut to size.
   The the same routine, Boat-Cote Resin with preservative and wait till it goes firm and start laminating.
   We were working with smaller batches of resin, only about 400 grams. First wet the surface then apply the cloth, we had it rolled up on the side, then start wetting the top side in sections. When the cloth looks good and wet and it has been consolidated in, all air removed, then squeegee away any excess to the next area to be worked and while I was mixing a new batch, Kay would be rolling on the peel ply and consolidating over that again.
   One length of peel ply done and so wetting the lower part now.
   Watch the edges, it is real easy to underwet those parts and the weight of the cloth can allow an air pocket to creep under the edge. But on the other hand, what a mess if a bunch of it runs over the edge... so be careful on the edges.
   And rolling on the peel ply
   And consolidating in again...
   and if you have a cold night, which we did, then the next morning, give her a blast of heat.
   The back web of the back beam was laminated just the same except this was just one sheet of 9mm ply. Instead of a scarfed joint on this panels, what I did was, I taped the other side on a butt joint. That side was going to be inside a structure anyway.. and on the other side I cut a groove into the line at the joint and filled it with glue mix. With the heavy tape on the back side (750 gr tri ax) and the 450 gr DB covering both sides end to end, I feel very confident of it's strength.
   Here I am filling the grooves and the holes left over from the screws that were used to stabilise the joint before taping the other side.
   This is a little fore and aft bulkhead ahead of the mast beam. I cut three pieces of 9mm ply. I relieved most of the wood out of the centre piece, leaving bracing struts, and covered the whole thing with Bote-Cote epoxy and treatment and joined her all up like the others.
   Nails in place to keep anything from slipping around. Did I mention that the nails are removed after the glue sets? Do I need to????