Mast Tabernacle Sleeve

[Adrian Langford]

Dear all,

Whilst putting Meisje away I notice that the stainless sleeve through which the mast tabernacle pivot bolt passes has moved up the mast by approx 0.5mm, creating a gap at the bottom of the sleeve.

I had epoxied the sleeve in place last winter, and now wonder whether my method of holding the mast in place is in fact not ideal.

When our mast is up we leave the pivot bolt in place and do not use the bolt at the lower front edge of the mast.

Assuming there is a slight gap between the bottom of the mast and the base of the tabernacle, all compressive forces down the mast must pass through the pivot bolt and its sleeve. I think this is not good for 2 reasons:

1) The bearing surface area between the top of the sleeve and the mast is very small, which results in a high pressure on the mast timber. This has resulted in our sleeve moving a little and could in theory cause the mast to split just above the sleeve.

2) Forward thrust, twisting and considerable fore-aft bending forces at the base of the mast are transmitted through the pivot, which is at the top of the tabernacle. This places higher loads at the tabernacle-to-deck fastenings then if the mast were attached to the base of the tabernacle.

I am considering removing the mast pivot once the mast is up, and using the bolt across the lower forward edge of the mast to restrain the base of the mast from sliding forwards. This is exactly the system used on my Wanderer, and I wonder whether this is the original intent of the designer. The advantage of this is that the pivot sleeve forces are eliminated, and tabernacle torsion and bending forces are vastly reduced. The only disadvantage I can see is that if there is a slight gap between the bottom of the mast and the tabernacle, then the mast will drop as the pivot bolt is removed. In order to reinsert the pivot bolt I will have to drive a wedge in underneath the mast. This is a slight nuisance, but one I'm prepared to put up with for the sake of making the mast and tabernacle system stronger.

Any comments?

Adrian and Roger, Meisje.

[Greybeard]

Falcon, which is a South African boat, doesnt have a sleeve like you describe, just a steel bush through the mast for the pivot bolt. With the mast in place the foot rests on the bottom of the tabernacle. I always leave the lower bolt in place as an additional safety measure which would keep the mast upright should the forestay come adrift for any reason.
Rather than leave the mast unsecured at the base could the sleeve you describe not be repositioned to the point where there is no gap under the mast foot, or alternatively could the base be packed with an appropriate thickness of stainless steel sheet?
Steve

[Adrian Langford]

Good idea, Steve. Do you remove your mast pivot bolt during the season?

Cheers,

Adrian.

[Greybeard]

Not at all. It's there as a safety measure should one of the rear stays come adrift, though in fairness, if one does fail because of wind strength the bolt ain't gonna help a great deal is it? Leaving it in the mast also means there's less chance of it heading off into that mysterious 'safe place' during the summer.

Steve