Tabernacle

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

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.

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.

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