Mast and Spars

My blog 31^st July 2018 described the laminated manufacture of the mast. I deliberately constructed it during the summer months to take advantage of the warm weather to aid the penetration of the epoxy into the fibres of the timber, it was then machined square to size and set aside. I have been looking forward to continuing the process of rounding and finishing along with the manufacture of the boom, gaff and bowsprit. I first planed down the correct taper in its square form before marking with a spar gauge then planning off the corners to form an octagon. I then continued to work it round with the plane and then abrasive paper on a block with a rotating action when pushing the block along its length, however, I found it time consuming and considered the results less than acceptable, I decided that I needed mechanical assistance. My solution was to manufacture a timber cylinder with a hole bored down its centre to allow a threaded stud to be inserted, nuts and penny washers were fitted either side to secure the cylinder allowing an approximate 40 mm projection on one side and 200 mm on the other. I then slid over a length of 15 mm copper tube and secured it loosely with two locking nuts at the end to allowing free rotation . The contraption was then secured in an electric drill chuck with the drill speed set low. I then inverted a sanding belt, thread it over the mast, inserted the rotating cylinder and applied tension to drive the belt by friction, unfortunately the belt refused to rotate around the mast but sanded the cylinder instead! I realised that I needed to increase the diameter of the cylinder to greater than that of the mast for the rig to work, I therefore re-constructed the rig with a lager diameter cylinder and tried again. Success, it worked wonderfully well and I was able to produce a beautifully round mast by roughing it down with a coarse grade before progressively using finer papers to achieve a smooth finish.

My home made mast rounding tool.

In action.

Dust flying everywhere, result!

Because of my intention to fit navigation lights and a VHF antenna, I customised the head of the mast to accommodate an LED Tri-Colour and antenna bracket. It was necessary to increase the 50 mm diameter mast head to 90 mm, I therefore made up two blocks with a half round machined into each face, when glued together they would then form a 16 mm diameter duct for the cables. In the lathe I turned the block down to an aesthetically pleasing profile then turned on a 30 mm diameter spigot and shoulder which would fit in to a corresponding hole bored in the mast head. The cables were pulled through the whole mast assembly prior to gluing, due care was taken to ensure that the epoxy did not squeeze out internally into the duct, therefore preventing potential cable replacement at a future date. 

The two blocks with half round ducts machined into each face.

The finished mast head ready for release from the lathe.

The architects designed masthead incorporates a 10 mm diameter hole drilled through approximately 40 mm down from the tip, the peak halyard passes through and is secured by a knot tied in the end. I was unable to adhere to this because of my cable duct throughout the mast; I therefore fitted an additional two eye mast hound which also provided me with a potentially useful spare forward facing eye. Both of these hounds were bedded onto the mast in epoxy mixed with fibres, to prevent possible rotation, a bronze countersunk screw was inserted either side of each hound. To prevent potential rotation of the main four eyed mast hound, I filed half round grooves into the inner face, sheathed around the mast then bedded the hound in epoxy onto the sheathing.

Because I have opted for a roller furling jib, the forestay is attached to the mast by means of a loop which, is prevented from sliding down by a wooden block. I considered that with this design there was a potential for the wire stay to wear around the mast, I therefore sheathed this area to provide a tougher wearing surface. I also saturated the base of the mast in epoxy and gently warmed it through with a heat gun to assist its penetration into the grain; this I hoped would toughen the fibres of the wood and provide a harder wearing surface against the steel tabernacle.

The completed mast and spars showing the additional two eye mast hound

VHF antenna and Tri-Colour navigation/anchor light. The base and the upper

reaches of the mast above the four eye hound will be painted white,

all other areas and spars will be clear varnished.

The base of the mast saturated in epoxy, teak cleat fitted to the fore face 

for the jib halyard.

The gaff jaws all laminated, clamped up, set and ready for release.

The manufacture of the gaff jaws was an interesting and enjoyable exercise.

This structure consumed the last of my home grown ash.

The boom gooseneck.

Work began on the build 12^th February 2017. Today is the day I have been working on the boat for two years and has so far consumed 1,968 man hours. Onwards and upwards, the finish is just peaking above the horizon!