Tag Archives: yard jaws

Caledonia Yawl Project: Spar Building part VI

The boom and the yard come second only to the birds-mouth mast in complexity. The jaws required some attention to detail.

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shaping the yard

The process of going from a square piece of glued up wood to a tapered cylinder is now becoming familiar. But there are still individual particularities to each piece as you have to read the wood and each facet might require planing in a different direction to avoid grain pull out.

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I started to decorate the place with the draw-knife cuttings which are so much fun when they are the full length of the spar.

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Careful mapping of the facets when you get from 16 sided to 32 sided is worthwhile. I found that marking the 32 edges then helped me keep track of where I was when I cut it down to 64 sides. On the yard that ends up being just one or two passes with the planer set very fine. It is in my mind the trickiest part of the process.

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After sanding the yard with 36, 60, 80, 100 and 120 grit sandpaper I was onto the boom. The time spent making this spar gauge based on Harry Bryan’s design in Wooden Boat magazine 277 was worth it but it was kind of bittersweet to think this was one of the last times I’d use it for awhile. (note: I still might use it to make the oars)

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The jaws require a transition from round to square which is an extra challenge when shaping the spar. In the end once marked it is relatively easy to do.

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I still have some of the reclaimed Honduran mahogany that was pulled out of home demolitions by a renovation contractor who was retiring and selling off their stockpile of old window and door frames. I now wish I’d bought more for future projects. But for this project I have enough.

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As per Ian Oughtred’s plans he specifies the jaws should be 22mm thick and made of two pieces. I added a 5mm marine ply to the mahogany to get to 25mm and it will do well to reduce the chances of splitting along the grain on this curved piece.

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I’m also attempting to make some copper rivets according to the September 2015 Small Boats Monthly article by Christopher Cunningham for the yard and boom jaws. I was able to order #6 gauge copper wire and I’m using some leftover 1/2″ copper pipe for the roves.

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spokeshave for the transition from round to square
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The last ridge going from 8 sided to 16 sided on the boom. The last spar!

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Marking the ridges from 32 to 64 sides on the boom and then shaving them down.

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Gluing the jaws layup with the wedges so that I can do some further shaping before gluing them to the yard and the boom.

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Gluing the boom jaw pieces together.

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Then shaping the pieces into something that looks relatively nice. I used the Japanese rasp, the block plane, the spoke shave, the belt sander and the random orbital sander to get it into it’s desired shape.

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The boom and yard jaws dry fitted.

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… and then all glued up. Tomorrow I’ll do the final shaping on the yard and boom and some sanding of the epoxy. All the spars will get sanded down to 150 grit tomorrow and all set up for varnishing. I’ve also got a bunch of little fittings to make that will need to be screwed onto the spars. Most are just little thumb blocks, but I also have to make the jib fairleads. I’m getting close to being able to rig it all up.