Mast Man

The mast was left with the cross section of a hollow octogone in the last episode.  It is time to make it a round cross section.

More Facets

A five inch diameter disk was screwed onto the mast head to define lines turning the octogone into a sixteen sided polygon.  One facet of the sixteen sided polygon has been cut along the mast length in the above image.  The mast end and disk was sniped in this first effort.  Future cuts would use a hand plane at the ends to avoid such snipes.

A rule is placed against the disk to determine the dimension, equal distance from the apex, that defines the edges of the new facet.  A template was made to mark this dimension on either side of the apex along the mast length.  A line then drawn with straight edge, from mark to mark, defined the facet edges.  A powered plane roughed out the material between the lines followed by hand plane refinements.  I later learned there are better and easier ways to mark out the facets, but this is the method I used.  

Rounding the mast has created the most sawdust in this whole boat build.  I shall be chasing out sawdust from these operations for years to come.

Rounding

The newly created sixteen sided polygon required a round of sweeping before continuing with mast rounding operations.  An inverted sanding belt was placed around the mast and driven by a drill motor powered drum.  A length of pipe, slipped over the drive shaft offered a hand grip on the drum side opposite the drill motor.  This was a little tricky to operate but was manageable with some practice.  The facets merge into roundness as a finer sawdust re-permeates the entire shop.

Initially a smaller diameter drive drum was used that could not overcome the sanding belt friction against the mast.  A drive drum diameter similar to the mast diameter provided the solution.  The drum was wrapped in duct tape to improve traction with the sanding belt.  A day and one half effort with this tool produced the rounded mast.

Sheave Boxes

The plans call for a curved surface to be cut through the masthead for lines (halyards) to run over while raising and lowering head sails.  I chose instead to use a sheave box on the fore and aft masthead faces so the halyards will not chafe against a static curved surface.  The sheave axle is only captured by insetting the sheave box into the mast.

 A fare amount of work with a router, a drill and mostly a chisel produced the inset cuts need to receive the sheave boxes on both mast sides.  

Masthead Crane

The main sail has two halyards to position a gaff spar in the sail's head.  This requires a masthead attachment point for two blocks to receive the halyards and direct them down to the gaff.  The attachment is a thickness of plywood epoxied into a slot cut in the masthead.  The blocks are lashed to a hole cut through the plywood crane projecting past the mast circumference.  A later image will show this crane feature.

Cutting this slot required the router fixture shown in the image above.  The fixture is held to the mast by wedges pressing against the mast and oversized holes in the white mounting fixtures.  Raised edges, on the surface the router rests on, control the slot width and length.  A similar smaller fixture was used for the sheave box insets.

 The router fixture worked very well creating this large deep slot.

Masthead Plate

The masthead will be covered with a stainless steel plate for mounting the navigation/anchor light and other future items.  Power leads supplying the masthead mounted items must be clamped so the lead weight does not placed loads on electrical connections.  To that end the conduit lead exit points have been modified with upward sloping slots that keep the leads below the masthead plate.  The sloping slots also inhibit water from entering the conduit runs.

Here the navigation/anchor light is mounted on the masthead plate top.  Wedge shaped blocks are epoxied to the underside and fit into the masthead sloped slots.  The screws, supplied with the light, are just long enough to barely start into the light's threaded base.  I need three longer screws, but I could not source them locally.  The next shipment will supply me with 100 screws, I'll be set for a lifetime!

The masthead plate is installed on the masthead top.  The plate's wedge blocks will be cut down and allow electrical leads to pass underneath.  A clamping force is provided as the masthead plate is screwed to the masthead.

Sheathing

I could look at the above image and wonder "What kind of animal is this?".

The mast was sheathed in carbon fiber fabric and coated with a fairing compound.  The mast was supported in three places to maintain straightness as the epoxy cured on the fabric.  Wheels supported the mast so it could be rotated as sheathing was applied.  The sheathing was applied in stages so the wheels would not run on wet epoxy and become adhered to the mast.  The wheels were later repositioned to run on a cured area while maintaining straightness so additional fabric could be applied.

I considered using a carbon fiber sleeve to sheath the mast all at once, but this would be an intense amount of work for one person at one time and the wheels might become bonded.  I wonder if this conductive fabric might limit the effectiveness of the internal radar reflectors.  This tall conductive stick may also increase the chances for lighting strikes.  I could fret about many things, but rest easy knowing I have a strong long stick.

On the right end is the mentioned masthead crane where the main halyard blocks attach.  The four horn shaped projections restrain the mast support shrouds that loop around the mast and extend down the side opposite the horn to anchor on the hull shear (hull upper edge). 

Completed Mast

The mast has received two coats of primer, three coats of top side paint and two sheave boxes.  The mast construction is done and I await an additional hardware shipment to raise the mast on the boat for the first time.  That will be a tale for the next episode.

Who was that mast man?