USOM Bulkheads

As my USOM construction gets back underway, next to the TP52, I am curious about what other people use for bulkheads. The hull is 2 layers of 5.7 oz. carbon and a layer of light s-glass that has pretty much been sanded away. I was planning on using manufactured honeycomb cored carbon panels that I would cut out. But I was thinking today there have got to be other wood options that result in a relatively close weight, since stiffness doesn’t need to that of a cored panel. The max bean is only 6". Any thoughts?

Why bulkheads? With that much carbon, seems like you’d only need deck beams and sway beams for the fin trunk.

My beam/internal panel material of choice is 1/4" balsa sandwiched between 1/64 ply. Very light and very stiff, although not as sexy as carbon fiber honeycomb composites.


Well my plan was to have 4 bulkheads. From bow to stern:

  1. Containing the turnaround block for the sheeting system, about 1" behind the bow.

  2. Forward mounting postion for the radio tray, as well as the forward edge of the mast step.

  3. The rear edge of the keel trunk (keel trunk and mast step are integrated).

  4. Containing turnaround block for the sheeting system.

I plan on using a drum winch, the winch will be mounted in the center of the boat, directly in front of the mast. While the rudder servo and recieiver will be mounted on opposite sides of the keel trunk. My deck is going to be a slight skiff design. Normal “cokcpit” area, with only a slight elevation in the bow (about 1") which ends right before the mast, which will be mounted somewhere in the 15"-17" range from the bow (not including bumper). I am going to a robust boat, since no one in my area races them, I want to make sure it last and can handle heavy use without too much worry.

Which will def. open the question, if I want strong, why worry about weight?

Well it isn’t soo much the weight but just how sexy a scratch built, all carbon boat would be, so in a sense, more of a pride thing than much else.

I use an idea from the Logic hull purchased from Bob Sterne. Try a sandwich of 1/64 ply 3/16 balsa and another 1/64 ply, light, strong, simple, and available at well stocked hobby shops. Clyde

Being somewhat of a “foam type of guy” - I will use household insulation foam, and hot wire cut to whatever thickness I need. I then laminate some 4 oz. glass to each side for bearing bulkheads, and 2 oz. cloth for non-compression type bulkheads. For the multihulls, I will use 3/4 inch foam, with a piece of pine laminated to the top. The bulkhead shape is cutout and shaped. Then the layer of glass on each side. I only use this heavy of a bulkhead for cross beam attachment points. Wood is drilled and a “T” Nut is epoxied in so beam bolts can be screwed directly into the nuts. I didn’t think the foam would be strong enough for beam attachment nuts by itself. Am considering similar for the 1/10 VOR boat - but would leave the foam bulkheads inside. Somehow a 70+ inch hull doesn’t seem to be as weight sensitive as a 1 meter hull !

When I did my 1 Meter tri - I inset glass tubes on top of each hull/float and filled and faired. The cross beams slide-fit into these so only bulkhead was in main hull for mast support - nothing in the floats.

In either case, epoxy thickened with microballoons handles the fillet between hull and bulkhead. This takes away any “hard points” where twisting or compression might cause cracks.

If you can get some toner from a copy machine, you can always add to the epoxy giving you “black glasss” which from a distance “looks” like carbon fiber. You can also buy carbon filler from Gougeon to make your glass black and very slick. It will be flat black after filling and sanding, but you can always brush on a light coat of varnish to get gloss if you want that.

This is the cosmetic thing - nothing too exotic - but it looks that way.