Spar Building

The mast support came out very well so it is on to the mizzen mast. The top section of Skorpa'a masts are hollow wooden spars sheathed with carbon fiber braid. The idea is to make them as light as possible. At the top of the mast every ounce makes a difference, both when under sail and when raising and lowering the masts at the boat ramp.

Sitka spruce is light and strong also pricier than the construction grade Douglas Fir I have used for most of the solid wood on the boat.

The hollow mast is made up of 8 staves 10 feet long and tapering from 1 1/4 to 7/8 of an inch. I set up a jig to hold the pieces straight and in place. Graham likes to tack the first stave down to a series of blocks that have been leveled and that is what I decided to do.
Unless you have a lot of extra hands the sections of pvc pipe are needed to hold the staves until they lock together. I cut an octagonal plug for the tip and a piece of plastic tubing holds the base open. I am not using any glue here just practicing. 

Seven staves birdsmouth side up are getting a very light coating of unthickened epoxy.

I made a notched spreader to help apply the thickened epoxy quickly and evenly, and as thinly as possible.

The first few staves go in pretty easily, but as you get past the half way point it is a little trickier.
With a little help form Sally who put down the camera to assist I got the last stave locked in.

Some people use hose clamps or wire ties but I think this idea I got from Charlie Jone on the Mess a Bout forum works great. I cut several old bicycle inner tubes into long strips. They go on quickly and put a gentle squeeze on the spar. The next day I unwrapped the tubes and cleaned up any squeeze out. I had two beautiful octagonal spars.

I drew a series of lines which guided me as I planed down the last two feet to give an additional taper. The I drew some more lines that allowed me to plane down the edges to make a 16 sided polygon. Whatever you call that.

You can see the lines on the mizzen.

By the time you get to 16 sides you are not that far from round so I planed the edges by I until the spar was close to round.

The mizzen is 16 sided.

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Once I got the spars as round as I could with the plane I used sanding blocks made from cardboard or PVC tubing to round them completely.