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John Lansdell
Jun 19, 2013 - 8:44AM
Main Mast Tabernacle and Fc'sle Door Deformation
It may be helpful to explain my experience in this area.
Like many we started to experience problems with the door beginning to jam, apparently due to the crushing load from an unevenly supported tabernacle aft section.
Having had a look at it, and done some research, my view was that the weight of the mast, and the downthrust of the shrouds should not be supported by the hinge bolt on the aft side of the tabernacle, but by a wedge under the heel of the mast, preferably on the forward side, which moved the centre of the downthrust to the centre of the plate of the tabernacle, and thus directly onto the support post behind the saloon bulkhead.
To achieve this, I slackened off all shrouds, and the forestay, put a substantial baulk of timber across the handrails where they are attached to the deck, then used a car jack on further blocks of wood to physically lift the hinge pin and thus the mast. At this point it was possible to drive a wedge in between the floor of the tabernacle and the heel of the mast, and leaving the hinge free to rotate, as it now carried no load.
Our door now opens freely, and we did not need to put in an additional mast support.
SeaDog Name (if owner or crew) Twotails
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Eric Richardson
Jun 21, 2013 - 7:12PM
Re: Main Mast Tabernacle and Fc'sle Door Deformation
Hi John
A good point, I seem to remember Peter French saying something about it years ago. I am not sure if all the Tabernacles are the same. On Taliesin the pivot bolt went through a vertical slot in the Tabernacle and when the mast was up the bolt was about a quarter of an inch above the bottom of the slot and under no load. Sounds good, but brings another problem!!
When raising the mast it's base makes contact with the Tabernacle base and is subject to very high loads as it is forced to raise the mast slightly. This produces bending loads on the Tabernacle and also deforms it's base untill a sufficient contact area is established. Once vertical of course it becomes ideal with all the loads on the mast base and none on the bolt.
I guess its take your pick time for anyone replacing a Tabernacle.
All the best
Eric
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