Caledonia Yawl Project: spar building IV

This summer it is now a race to have the rigging done before we take our vacation in the second half of August. My intention is that we have the boat ready for some day trips and camp cruising. I’m setting a deadline for myself. So over the last month I’ve been regularly plugging away at the spars. I started with the most complex being getting the main mast glued up.

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I cut the taper on each of the 8 staves which was tricky as they are small pieces and hard to keep square when vertical as the birdsmouth cut did not have two even ends to rest on.

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I ended up resting them on their sides and planing them with the block plane at 90 degrees. it was easier to clamp and not too hard to keep things square.

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The next step was to make the 8 sided top and bottom plugs for the mast. The top plug had to be long enough to cover the area needed for the halyard sheaves. So i made it 50 cm long as I will have the sheaves one on top of the other instead of side by side.

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Dry fitting the top plug into the tapered mast. That was the more complex part of the exercise. Getting the inner diameter taper right. Fortunately this does not have to be perfect as a little space can be filled my thickened epoxy.

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Mapping the taper of the the base plug of the mast I decided should be longer and go as high as to where the boom rests against the mast. Partly because I’m thinking of fixing the cleats for the halyards onto the mast and would like to have more material for the screws to grab onto.

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Testing the diameter of the base plug with an off cut of the main mast staves. This piece was longer and the taper a little trickier to get right as it covered both a flat section and the reverse taper at the base.

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Then I cut out a taper of material on the inside of the mast plug to ensure there are no hard edges that could impact the flex of the mast or create a breaking point.

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Finally everything was ready for gluing. I decided to do this in two steps. gluing up the staves in two clamshells by taping two of the birdsmouth sides. This will allow me to then on the second step to glue in the plugs and the remaining two stave edges.

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I put all six of the staves to be glued upright and slathered them in unthickend epoxy and then squeezed the microfiber thickened epoxy with a piping bag.

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14″ Zap straps worked great to clamp it all together and a bag of 100 was way more than needed. But we have my friend’s two masts for his Penobscot 17 schooner rig to do later. I did use vice grip pliers to pull the zap straps tight. I found this really made a difference.

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Once the epoxy cured overnight I was able to open up the clamshell and remove the clear packing tape I’d used. I did a little clean up of the squeeze out epoxy on the inside where the plugs would go using a heat gun and a small scraper.

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But left things as the are for the rest of the mast. I also decided not to coat the inside with epoxy. my reasoning is that it might be worthwhile to let the wood breath on the inside. There should not be any water ingress or holes in the mast.

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Then the final glue up of the main mast with both plugs well coated in thickened epoxy.

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It was such a pleasure to get to this point and see this complex interlocking set of small pieces of wood come together into a solid monolith.

I will weigh this mast as in theory you save approximately 35-40% of the weight by building it this way. It is however a significantly longer process to make. Some advantages is that you can work form smaller stock and with a few scarfs not necessarily have to have full lengths that you need. Building a solid mast with two pieces glued to each other however would be much faster and for a boat this size with sitka spruce maybe not yet unmanagable as far as weight. I’d be a little more reticent if I had to work with douglas fir which is very strong but also heavier. I feel very fortunate to have had the time to source sitka spruce.

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