apple pie construction showing stitch and glue method of boatbuilding

Lengthening my Sprit

I now have a nice new sprit sail for my Skerry Boat but the peak is not being tightened very well because my sprit spar is too short.

I had started making spars for a balanced lug but given up because I decided to stay with sprit sails. (Read about Sprit sails and how they are the most efficient rig in existence!)

I measure the diameter of the existing sprit and the diameter of the spar and they were exactly the same. Sometimes I just get lucky!

I had hoped that cutting the tip of the existing sprit would miss the solid plug I had put in the end but I did not. I was going to put a dowel through the center of both pieces and just epoxy everything together. I'm working outside at the boat club and conditions are a bit rough.

sprit has been cut to allow me to add a piece

I sanded the finish off the area of the cut and actually thinned the wood to compensate for the extra thickness of the fiberglass. I made a paste of thickened epoxy and wood flour and used this to glue the 2 pieces together.

The nice tidy picture does not show the huge wind that blew up with millions of tree seeds all over the place and the fiberglass strips getting blown around covered in debris! That's why there are not too many in between photos. It was a struggle to keep everything from blowing away in the gusts.

glued sprit extension using a butt joint

I had prepared some fiberglass strips to tack the 2 pieces together and I used these as band aids to stick them together in the right position. I had some wood splints that were perfectly straight and plastic wrap to tie everything together. After a couple of hours the fast epoxy had set enough to continue.

3 layers of fiberglass cloth strengthen the birdsmouth sprit

After moving to a more sheltered area, I sanded the joint smooth and applied 3 pieces of 6 oz fiberglass cloth. The 3 pieces were staggered so as to not make a bulge. I had sanded the area when I prepared it so that it had been thinned down to allow for the cloth thickness. I decided on 3 thickness (plus the original strips that first tacked the extension on) because I had not put in a dowel inside. I think this is all overkill really but I like to overbuild.

I wrapped the cloth in shrink wrap again because there was still lots of bit flying around because of the wind. The whole extension also got a coat of epoxy to seal it.

3 layers of fiberglass have hardened on sprit extension

The plastic wrap has been removed and it created some ridges of epoxy. The cloth is well filled and nice and flat. Sanding will smooth out the ridges.

3 layers of fiberglass have hardened on sprit extension and have been sanded

After some sanding the joint is quite smooth and most of the ridges gone. The taper of the end is quite visible. I had made a taper on the spars I cut to get the extension. I completed the sanding out of the ridges and added a last coat of epoxy on the whole extension including the dowel at the end. Its very hot today and there is no wind where I'm working so I don't have to worry about flying debris. The epoxy set very smoothly and only needs a few coats of varnish. The colour will never perfectly match but Next time I varnish the whole spar I'll put a bit of stain in and this will help blend the extension.

The end is simply a 3/8 dowel drilled into the end of the sprit and glued in with thickened epoxy.

final coat of epoxy has hardened on sprit

Tried out the extended sprit on the new sail. It is much better. I will have to experiment how to set it to best effect. The joint is clearly visible if you look for it but not offensive. Another 6 inches would have been better but I did not want to have spars longer than the inside of my boat. I went sailing and the boat went really well. The new sail set much better and the balance of the rig was so good that I did not have to use the rudder at all. It just tracked straight. Its a good thing because I forgot to put down the rudder and only a small part of the rudder was in the water. I never noticed!

I try to be accurate and check my information, but mistakes happen.

email me if you find mistakes, I'll fix them and we'll all benefit: Christine