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Making Spars for my Puddle Duck Racer

My Chosen Rig is a Leg O' Mutton Sprit Sail

leg o mutton sail

This is a simple triangular sail that has proved itself many times over.

It has many advantages, simple, self vanging, the shape of the sail prevents the boom (sprit) from lifting, the sprit is hight enough not to bonk you in the head and it shows good performance.

It requires a higher mast than a 4 sided sail, it is harder to reduce sail and because of the sprit which interferes with the sail on one side there is a "bad side". I have the same effect on the Skerry but I don't really notice any difference and sometimes the bad tack is the better tack. I don't know why. Above is a handsome sail (photo courtesy of Shorty)

Since I already had a tall mast, I decided to use it. It's my experimental carbon fibre mast. I had made the tube and never actually finished it or used it on a boat. I had intended to make a leg 0' mutton sail for the Skerry.

I did not have a good sprit for it so I decided to make one.

Making a new sprit for my PDRacer

I decided not to use the bird mouth method of making spars because I thought it would be more work so I decided to glue up a sprit and leave a gap in the centre for less weight. I did not have a good piece of solid wood to use. The Lumber yards in this part of the woods were singularly lacking in clear 2x10 or more clear stock. Usually you can get a wide piece and find enough clear wood to make a spar but not this time. It doesn't help that the woodyards are outside and there is 3 feet of snow on the ground.

I had some nice clear pine so I decided to use this. It's light and quite soft. I had used pine for the Skerry mast so I think it is strong enough.

plan for spritSimple spar plan. I had originally aimed at 2 1/4 inch diametre but when I checked my Skerry sprit, it was less than that for 4 feet longer and so I decided to go for 1 3/4 inches with a 3/4 inch cavity.

plan for sprit join boards for sprit
My boards were only 8 feet so I scarfed them to be a couple of feet longer. I won't need that much I think. It's a short skarf joint, it should be longer but the pieces will be glue up against other pieces so not much stress on the scarf joint. I roughly cut the joint with a plane and finished with the belt grinder.

sprit join boards for sprit
After cutting my board I tried to dry assemble them and I found that the boards were floppy and unmanageable and that I could not figure out a way of keeping a cavity in the middle. I decided to glue up the 2 thin pieces and insert some spacers inside. The spacers add no real weight and create an even cavity. The spacers at the ends are longer so that I can drill holes or attachment points through them and have something solid to drill through.

sprit trimmed blank
I glued up the sides of the blank and after setting, trimmed extra using the table saw. It was easier to trim after than before because the pieces are not so flexible now that they are joined. In the end I think it would not have taken any more time to cut the birds mouth pieces and they would have been easier to shape. It would have been simplest of all to make a spar out of a single pieces. I think I mostly wanted to try an alternative method.

sprit trimmed blank
The blank quickly rounded up using a plane. Once I had a good shape I used a band of sanding paper, in fact an old belt from the belt sander, to finish the sprit round. Since there are no knots and the wood is soft, it went very fast and within a couple of hours I had a shaped spar. After consideration I think the sprit is too large and heavy. So I took my block plane and shaved a layer off. I also shed a pound. The spar now weights 3.3 pounds. The same weight as the carbon fibre mast I intend to use with it. I had made this mast a while ago but never finished it because the boat was also on hold. Here is how I made my carbon fibre mast.

sprit sprit
I put a hole at one end and a slot at the other end. The hole end will be for the end of the sail, I will also attach the sheet through it. The mast side gets a slot. I did this for the Skerry Sprit and it has worked really well. The Skerry sprit has a pointy end and I found this works but is sometimes annoying trying to spear the top of the sail in the wind. I'm hoping that he hole can be attached to the end of the leg of mutton and avoid the spearing exercise.

The sprit is now ready to finish. I'm not sure if I will paint it or varnish. Varnish is prettier but takes more maintenance. The sprit is quite rigid and quite light. It can bend only a little.

Since I can't ventilate the shop I'll wait till I can open doors and windows to paint. It's frightfully cold these days. -20 something right now and getting colder.

emails: Christine

This web site reflects my personal ideas and doesn't represent anyone else's point of view.