mast support

Ardenfour

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I want to increase the strength of the main bulkhead below the mast, as presently is 12mm ply which I feel is inadequate, and I've just removed a laminated teak 4" x 2" beam which supposedly was supporting the mast and ran across the bulkhead against the coachroof. This beam was held on with 4 brass screws which sheared when I turned them, and by some grp mish-mash and resin which I think was gluing the beam to the bulkhead - could just about hold the weight of the beam. The beam itself seems a sturdy affair and I will retain this (there are 2, fwd and aft of the bulkhead) I plan to epoxy them back on and fix them with 4 12mm stainless rod through the 2 beams and bulkhead. I'd also like to add two support pillars either side of the doorway, but am not sure how to spread the load at the foot of these posts. Another two beams across the bottom resting on the keel, perhaps? Can anyone advise, please? Thanks
 

ashanta

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28 Apr 2003
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I have metal plates either side of the bulkhead spreading the load. They blend blend in to the white, painted surface of the bulkhead and are certainly strong enough.

Regards.

peter
 

William_H

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Sorry i don't know the boat type but it sounds like you have a central arch for access with mast support either side of the arch or access hole. Obviously the best mast support is a pole from keel to mast base however supports either side of an access is ok. at the bottom the hull is probably quite strong either side of the keel however a support beam (under floor beam) would be best to ensure rigidity, epoxy it to the hull, wood or metal would be ok.
similarly under the mast an athwart ship beam under the mast base out to the vertical supports is necessary to reinforce the cabin top. Don't forget that it is the vertical dimension (just where you don't want to intrude on headroom in the access) that provides the real strength. The posts can be wood or metal but I might suggest that you temporarily jack up the cabin roof (from the keel) a little before fitting the vertical supports so that when you remove the jack the load will come mostly on to the vertical supports. Or you could use extendable metal tube supports with screw extension built in to get some pressure. The thing is when sailing the mast will exert downward pressure which must be resisted and transfered to the keel and eventually to the chainplates any flexing or crumpling of this support will cause the stays to go slack especially the forestay reducing windward performance.
You might consider extendinjg the chain plates down the hull inside or down the bulkhead to a point where a beam or pole one each side can go to the base of the mast or mast support cross beam because this is the path much of the load will take. ie so the chain plate pulls up onto a pole which transfers the pressure to the mast base. Of course this does not help the transfer of forestay load to the mast base which can only be done via the keel. basically if you can get it stiff it will be more than strong enough. good luck will
 
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