Sunday, January 19, 2014

The Matinicus Double ender- Part 23

Spar Time!

Click HERE to view part one.

The original sail plan. Fores'l was increased to 80'.

A full set of spars for a lug yawl is a bit of an undertaking. The pieces are not big or heavy, or complex either, but there's a lot of them! Five for this boat, and it would be six with a boomkin, but I'm tacking the mizzen sheet to the rudder head so don't need that stick. Mouse is a special boat, and not a cheap one, so I went for the best spar grade Sitka spruce I could find at M.L. Condon lumber. I can remember once paying around $2 a board foot for this stuff, back in the 80's. Try $8.50 now! But I picked out some nice sticks. I also had an old mast blank from my Penguin that I cut up and re-purposed. That stock went into the new mizzen mast.

The fore mast is a solid stick, but the rest are hollow birdsmouth, except the mizzen boom which is so small that a hollow construction is not worth the effort. I glued up the fore mast in three pieces of 5/4 stock, dressed to 1-1/8". I don't have room behind the jointer for 16'  stock, so I trued up the edges with my circular saw and a home made track beam, clamped to the boards along a chalk line. After truing one edge, I ripped the sticks to width on the table saw, then flattened the high spots on one face of each with my fore plane before sending them through the planer.

I made a saw track to true the long edges of my spruce.

The three sticks for the solid fore mast.
After gluing up the blanks, I popped a centerline down the length of each side and laid out the tapers from the center out. I sprung a batten around the marks for a little parabolic curvature, rather than a straight taper, and cut to the lines on the bandsaw. I trued the faces flat and square before laying out the cuts for eight siding with a little quick and dirty spar gauge.

Sawing out the tapers.
Spar gauge used for laying out the eight siding.
 I left the fore mast square in section from just above the partners down to the tenon. The round section fairs into the square with a sort of scallop. I cut close to the lines with a drawknife, then finished up the flats with a plane, working the scalloped bits with a spokeshave. The sixteen siding I did by eye, just striving to keep the flats equal in width.

I cut close to the lines all around with a drawknife.

This is how I transitioned fro round to square.
Sixteen siding by eye.

The foremast tenon.
 At the same time that I was working the fore down to round, I was cutting the birdsmouth staves and gluing those up. This method of spar building utilizes a formula to derive the stave widths and thicknesses for a given radius. One edge of each stave is cut with a 90 deg. vee groove, and the other edge is left square. The taper is cut on the square edge. One stave of each spar is marked out, cut, and trued up with a block plane, then that stave is used as a pattern to mark the other seven.

The vee groove is cut on the shaper.

Using a tapered stave to mark the rest of the eight pieces.

Three spars worth of staves.
Each square edge nestles into the vee of the next stave, with eight staves making an octagon. Glue is applied in each vee groove, and the spar is assembled and clamped with hose clamps. I then glued octagonal plugs in the ends of each stick, to close them off. 

Applying glue to all eight at one time.

The staves are assembled, and secured with hose clamps.

End plugs.
The hollow spars were sixteen sided just like the solid one, by eye. I keep threatening to make a set of spar planes, but I haven't done it yet. I ended up buying a nice radius spokeshave from Veritas, which fits every spar except the large end of the fore. This shave worked great on the spars, as it will on oars as well. It's a very well made tool that makes truing a round much easier. For sanding, I used a trick that I picked up from the WB forum, probably from Clint Chase. I made a box sander from plywood and a sanding belt that conforms readily to a changing, round shape. I made an 80 grit and a 120 grit box, then finished up with some 180 grit by hand.

My radius spokeshave. An excellent tool!

Flexible sanding box. I got the idea from Clint Chase and Steven Bauer.

It conforms to a changing diameter easily.
The fore mast has a sheave for the halyard, let into a through mortise at the mast head. Rather than chop a mortise though, I cut a "u" shape in the top, then glued in a block to close the box. Easier than chopping by far. The sheave pivots on a brass rod driven through the mast.

Fore halyard sheave fits into a "u" shaped mortise.

The top is closed off.

The finished mortise.
The mizzen utilizes a "dumb sheave" for the halyard. This is just a hole drilled in the mast head to take the halyard. That sail lives on the mast. The halyard is there just to allow reefing, so it doesn't go up and down much.

The set-up for hole drilling in a spar. This is the fore boom, I believe.

I drill a small pilot first, then come in from both sides with a larger bit.
After sanding all the spars, I put on a sealer coat of shellac to keep them clean, then headed out to the club to set up the sails for the first time.

Spars are shellacked to keep the dirt off 'til varnishing time.
Next time we'll set up the rig!


eebe4 said...

Nice description! I'm curious to know the length and weight of your main mast when you get the chance. My Sooty's 17 footer is less than 19# I think. I calculated a solid version would be 27#. That's with Douglas Fir and a 3.25" diameter at the partners.
Did a lot of hull sanding today. Second fairing application. Epoxy coating tomorrow.

Jimbo said...

I didn't weigh it Eddie, but the spruce is very light. It's quite easy to step.I'll have to check the length, but I think it's 16'. Cricket's mast (21') is hollow, doug fir, and is much heavier.