Building a Hollow Gaff

Weight and windage--the killer W's--cannot be eliminated from any sailing rig, but they should be minimized. Compared to the Bermudan rig, the gaff rig is particularly prone to the W's, and is one reason why too many gaffers go to windward about as well as their bad reputation says ...

With this in mind, I have decided to replace the old solid gaff (the spar to which the head of the mainsail is bent) with a hollow one. A hollow gaff should be just as strong and, I hope, about half the weight.

The gaff will be constructed from eight staves (think of an old fashioned barrel) of vertical grained Douglas Fir. Before cutting, we must do a little algebra to figure out the width of the staves to form a 3.5 inch diameter gaff when rounded ...
And then we cut the staves with a table saw, setting the blade at a 22.5 degree angle, so that, when glued together, the staves will form a 45 degree angle. The staves are tapered at one end in proportion to the desired taper at the end of the gaff.
The staves are then glued together in pairs.
Then the pairs are glued together to form half of the spar.
Into the ends I insert octagonal plugs. This is most important at the throat (the end abutting the mast), as the bolts used to secure the gaff jaws will very likely crush a hollow spar when tightened.
Finally, the two halves are glued together. Epoxy is spread throughout the inside of the spar to prevent any ingresses of moisture on the inside.
Since the gaff intersects the mast at an angle (approximately 40 degrees from the vertical), some curvature in the gaff jaws is desirable. I shall use the old gaff jaws as a mold for laminating the new ones. Each laminate is a pattern made of 0.25 inch ash.
After gluing, the gaff jaws are planed and sanded.
Now we return to shaping the gaff. I plane off the eight corners to form a sixteen sided gaff, and then use sanpaper inside half of a PVC pipe to make it round.
The gaff jaws are through-bolted with 5/16" threaded SS rods. A #10 wood screw will be added to secure each tapered end. The swivel-slide in the center pivots on a 3/8" SS rod. I increased the size of the slide compared to the old gaff to better distribute the compression load generated by the peak halyard and the mainsheet (a considerable amount of force--I had to re-leather the slide about three times per year with the old gaff).
After coating the gaff, slide, and jaws with a wood sealer, I bolt on the jaws, applying some generic black goop (LifeCaulk) for bedding.
Finally the gaff will be given a good sanding in preparation for painting, varnishing, and leathering.

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