The mast on a Drascombe Gig is a heavy bit of timber. At approx.
7.3 meters long and 90 mm in diameter it's stepping each time we rigged Tra
Bhui was something that needed a bit of care and planning. After adding the
Plastimo roller reefing system last year the total weight of the mast and
rigging became such that its erection became more than a bit of a challenge.
While Drascombes with cabins benefit from a mast mounted on
a pivot, the configuration of the Gig meant that such an arrangement was not
really possible. An alternative solution was required that not only allowed the
mast to be easily lowered in a controlled manner, allowed the mast when taken
down to be retained within the boat (no overhang) and which allowed the mast
when being taken down to miss landing on top of the outboard.
The obvious answer was to make and fit a tabernacle which is
defined in the Oxford English Dictionary as "A partly open socket or
double post on a sailing boat’s deck into which a mast is fixed, with a pivot
near the top so that the mast can be lowered to pass under bridges". While
this is basically what Drascombes with cabins have, a tabernacle on the Gig was going to be a much larger
construction.
Considerations when considering the suitability of a
tabernacle:-
1.
For a tabernacle to work the base of the mast
would need to swing forwards, a movement blocked by the front thwart. This
would therefore require the front thwart to be removed.
2.
The foot of the mast would need to also swing
clear of the "Samson" post. This would mean that the pivot point
would need to be moved as far back and as far up the mast as possible. It also
meant that the base of the mast would need to be modified as the mast position
meant that the pivot point could not be moved far enough back without the
tabernacle having to incorporate either a very sizable bit of timber or a metal
space frame.
3.
The tabernacle would need to allow the rake of
the mast to be adjusted if required
4.
The mast pivot would need to be off square to
the centre of the boat to allow the mast
to lie off centre when it is down and thus avoid the outboard
To work out the best position for the tabernacle and the
mast pivot, I made a mock up using some gash 20 mm chipboard. Having removed the
front thwart - this also acts as a mast brace I was able to place the mock up
in the boat and move it around to try out a few different options. Given the
shape of the Gig's floor molding and lack of "square" edges and
surfaces this took a bit longer than I had hoped and involved a good bit of
trial and error. Eventually I determined what I think is the best place for the
pivot. I also determined a suitable shape for the tabernacle which would not be
too obtrusive and hopefully in keeping with the lines of the Gig.
The next step was to make up the two sides of the
tabernacle. I planned to use a length of Iroko for this and had managed to find
a bit that was 40 mm x 300 mm x 2000 mm which would I thought be ideal.
With the basic shape cut out I was concerned that the two
halves looked too crude and in a moment of madness decided that I should carve
a pattern into them to make them look a bit more interesting. Given that as
with all my 'projects" I have to fit them into the few days that I have at
home each year (along with catching up on jobs around the house etc.), this was
probably not the most sensible idea that I have ever had!
The pattern that I chose was based on circles and curves,
although pretty simple it did involve a good bit of time, but it was a good
excuse to get out the chisels and mallet. The finished product will never win
an award but hopefully it does add a bit of interest to what otherwise would be
rather plain lumps of timber.
With the two halves now made the next step was to measure
the mast, drill the pivot hole and then try a dry assembly. This was all done
with the mast lying on the ground and worked out OK. Before going any further I
would have to cut the bottom of the mast off and that really was the point of
no return! The cut would be approx. 200 mm from the bottom of the mast in the
form of a step which would allow the top and bottom sections to interlock
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| Dry assembly of tabernacle and mast on the ground |
With the mast cut, the cut off part was set into the bottom
of the tabernacle. It would make use of the existing mast socket to help resist
the forces on the bottom of the mast. The tabernacle itself could now be
mounted in the boat. The base being held in place by the cut section of the
mast engaged in the original mast socket and by the addition of an Iroko base
plate secured into the floor strengthener which runs just across the boat just
behind the mast foot.
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| Mast standing in tabernacle - no standing rigging in place |
The top of the tabernacle is held in place by a new thwart
made in two parts. Each part picking up on the original thwart mounding points
and a recess cut into the tabernacle with a router.
The finished tabernacle appears pretty secure and allows the
mast to be easily raised and lowered. At the time of writing this Tra Bhui has
not been back in the water for the 2015 season so it will be a month or so
before integrity and suitability of the tabernacle will be proved in earnest.
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| Changing design of front section of cargo deck |
Of course changing one thing on a boat has consequences one
of which in the case of adding a tabernacle is that the front section of the
cargo deck will no longer fit in place, but fortunately I have plans to modify
that anyway as opening it when the camping tent is up was problematic.
Additional Pictures to follow
