Build a hollow spar

The rig for my boat Ruth Avery  was built by the previous owner.   I have since modified her very high peaked gaff mainsail to a more conventionally peaked gaff, around 40 degrees from the vertical.   She also originally had a solid gaff made of Douglas fir which weighed a little over 40lbs., which is a fair bit of weight to have high aloft, especially in light winds when the sail begins to slat.   So I will build a hollow gaff which will weigh a little less than half the original.

The gaff will be constructed like a long barrel, made of eight staves.   The staves are ripped from Douglas fir planks using a table saw with the blade set at 22.5 degrees from vertical, and thus each stave joins at 45 degrees (8X45=360 degrees).   Also each stave must be tapered at one end so the gaff will be tapered toward the peak. 

We will begin the gluing process with pairs of staves:

Then two pairs for half the gaff:

Now we have two halves we only need to glue together.  However, we first need plugs for each end–and especially at the throat end–in order to make the ends solid.  This so that the through-bolts which will hold the gaff jaws at the throat do not crush the gaff when tightened.  At the peak end we want solid timber for the fairleads to which the peak will be tied as well as the topsail sheet will be run (even though I have since ceased bothering with a topsail, I’m no boy racer anymore …).

Then we glue the whole thing together:

Now, on to the gaff jaws.  I will use ash for the jaws.  To get the correct curvature, I will use the old jaws (underneath in the photo below) as a laminating jig for the new:

After some sawing and sanding we have the finished product:

We attach the gaff jaws to the gaff with through-bolts.  We also need to add the tumbler, which goes in the crotch of the gaff jaws and will swivel on one of the bolts so that it always lays flat against the mast.  The tumbler is designed to take inward pressure of the gaff against the mast which is created by the peak halyard.  Both the tumbler and gaff jaws will be leathered on the inside where they come in contact with the mast:

The head of the mainsail will be bent to the gaff with robands.  Notice the holes in the jaws for securing the throat halyard to both the gaff and the sail.  Similarly, small fairleads secure the span for the peak halyard (the span terminates with an eye at both ends, the spar runs through both eyes).  After varnish, paint, and leather, the mainsail is bent on to our new gaff and flying proud.

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