Tuesday 31 March 2020

More sticks

Here's the rest of the sticks for rigging; in total I have the mast, boom, bowsprit and spreaders.

The spreaders are solid, and are simply a lamination of a Tassie oak either side of a Jarrah core, shaped appropriately. I have to make some bracketry from bronze to attach them to the mast but allow them to pivot.

The boom is a much simpler construction compared with the mast. I started by making a 3m length of sail track with 30mm x 12mm jarrah boards, scarfed into 3m lengths. Then I scarfed a second piece of jarrah for the bottom of the boom, and planed it to 24mm x 30mm.

These were both glued to a 3m length of 19mm x 75mm Tassie oak, and a bit of a slot was cut in the aft metre to allow for a block to increase outhaul purchase. Using a block, I can either go for 2:1 by attaching directly to the clew, or else 4:1 by looping through the clew back to the end of the boom.

I also cut slots in the side pieces for the outhaul to exit, and finally I mirrored everything on the other side. Then I glued it up and went at it with the power plane to make a boom-shaped thing.

The ends are 55mm round,and the center section is 55mm wide by 75mm deep. The taper at the mast end is short, over about 800mm, to ensure I've got full thickness at the vang attachment point. From the main sheet attachment point to the end of the boom it tapers over a distance of about 1400mm.

The rear shows the slot for the block, about 16mm by 35mm:

Also visible is a bit of vein in the tassie oak. It's not very deep and is right at the end of the boom, so I don't think it compromises the strength of the boom at all. In fack I think it looks really nice.

This shot shows one of the outhaul exit slots nicely. With a 2:1 outhaul I simply did an exit slot on each side, each of which will have it's own cleat, meaning the authaul can be easily tensioned from either side of the boom.

And finally here's the whole boom, showing it's droopy belly around the vang attachment and mainsheet attachment.

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