Wednesday, June 21, 2017

St. Jacques Log 21 Jun 17 Mast and Sprit

06 Jun 17:

Went and picked up some 14 foot spruce 2x4s for the mast and sprit. Cut them down so we had 2 pieces, one set to make a 2 1/2 inch blank for the mast and one set to make a 1 3/4 inch blank for the sprit. The mast is 11' 7" and the sprit will be 12'3".

Left them long so we can pick the best section after they are glued up. Fastened them together with Jamestown Distributors TotalBoat THIXO thickened epoxy.

09 Jun 17:

Took the clamps off the spars. Marked the circumference on the end. Cut 45 degree angles on each edge just outside of the mark with the table saw. Now they are 8 sided.

(Edit: Stop. That circle is required 2 1/2 inches. No room to spare. So at this point we needed to cut the corner bevels perfect AND turn the blank exactly from the center in order to maintain that diameter. Stay tuned).

Eight sided the spars. (Edit: We should have marked center before eight siding, it was hard to mark afterwards as our bevels were not all equal. The result was us finding the wrong center for turning the spar and as a result the diameter was less than desired.)

21 Jun 17:

Built a shaping jig for the spars and router sled. Main box was made from 2x6 lumber with 1x6 ends and 1x6 feet. One end can be moved to accommodate different length spars. Drilled a 7/16th inch hole in the spar ends and inserted dowels. We cut the mast side profile on 2 lengths of 1x6 lumber and screwed those to the box, just proud of the box, that is what the router sled will slide along, guiding the router up and down in order to get the desired diameter. There was a little experimentation to see how high to place those taper patterns, too high and the router bit wouldn't cut as deep as needed, too low and the excess wood on the blank would bump against the bottom of the sled. The router sled was made from 2x6 guides and a 1/4 inch plywood base plate. A thicker base plate, maybe 1/2 inch, would have been better as that base plate would deflect down a bit with excess pressure and we had to watch that. The router is a DeWALT compact trim router with a Bosch 3/8 inch flush bit.

In theory we would have been able to set the router to just barely touch a flat on the blank, then turn the blank and get a nice even circle cut evenly all the way around. In practice we found our 8 sided blank was a little lopsided and the dowel hole was a bit off center, so we cut more off of one side than the other. We adjusted by cutting a little deeper on one side, which resulted in a spar diameter around 2 1/4 inches the design 2 1/2 inches. It seems very strong irregardless, and based on our experience that we have carried similar square footage on a Sunfish wooden mast that was 2 inches in diameter, we will give this mast a try and see how it does. This issue became even more evident on the sprit, which we had cut to exactly 1 3/4 inches. Two attempts to cut an exact round spar out of the blank were unsuccessful. What we will do to fix that is be more precise on eight siding the spar and start with a bigger blank.

Note how the inner 1x6 guide tapers down at the far end to allow a deeper cut. Both ends are tapered per design.

We could hold the sled in one spot and turn the blank by hand to cut a groove, or we also held the spar still and moved the sled to cut one aris. Just depended on what mood we were in. We checked the diameter with calipers. In some areas the rotating blade of the router would catch small bits of the blank and start it turning like a lathe. That would have been great to do the whole spar that way but the blank was out of round and the jig bounced around.

Nice views of the tapered ends and profile templates.

This idea came from a youtube video on how to turn a cylinder from the Woodworkers Guild of America. We scaled it up but did not make the bottom of the box solid, that way sawdust could fall to the deck and we swept it up later. We also used dowels in the ends vs the hardware that they used. After trying a few blanks, we might go get the hardware to hold the ends similar to what they used.

Once the mast was rough cut we took the belt sander with 40 grit and lightly ran it perpendicular to the mast. The mast would rotate, fast if we let it, but we could control the speed by slowing the mast with a gloved hand or by varying the angle and pressure that we held the sander. Parallel to the mast = no rotation. 90 degrees to the mast, lots of rotation. We also sanded some areas along the grain and rotated the mast a few degrees at a time to shape areas around the tapers. Final sanding was by hand with 120 grit.

Mast was sealed with Jamestown Distributors TotalBoat Wood Sealer. Then lightly sanded with 120 grit. Then we applied TotalBoat Gleam Marine Varnish Satin. Repeat sanding and varnish times 2. The wood sealer is great, it makes a nice base for the varnish and it does not seem like we have to build as many coats of varnish. We prefer the satin finish over high gloss. We also like the varnish kit that Jamestown Distributors provides with the quart kit, it includes 2 paint pots, 2 stir sticks, 2 foam brushes, 2 paint strainers, and a pair of latex gloves FREE.

This is the mast after we sanded the wood sealer, ready for the first coat of varnish. Wiped down before varnish was applied. A light sanding between coats creates a better surface tooth for the varnish to grip and it is easy to see where the shiny varnish is covering the scuffed areas.

3rd coat of varnish.

Log of St. Jacques.

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