mast compressing deck

J

jwsmyth

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I've noticed the beam on the underside of the coach roof taking the mast compression is sagging quite badly to the point where the heads door scuffs it. Is there a quick answer for this or is it a re-decking job with new beams? Any advice greatly appreciated.
 
This is a problem on Albin Vegas too. The 'quick' answer is to remove and re-hang the heads door a half-inch lower, I'd be surprised if there wasn't a gap beneath it to allow it to be lowered.

The longer/permanent answer with the Vega is to ease the standing rigging, slowly jack-up the compession beam, complete with the deck and mast above; leave it to 'set' for a few months, then bolt/screw/glue a 6mm stainless steel plate (shaped to suit curve of the deckhead) to the front face of the mast support beam, remove the jack/prop and re-tension the rigging.
 
Thanks for the advice, there isn't really room for a compression post, the beam currently there is pretty small i think, but its been there for nearly fifty years. A beam alongside the current one to bulk it up sounds the easiest option, maybe a stainless plate aswell. What do you think?
 
A pair of posts each side of the companionway is easier than beefing up the beams. 2"x2" mahogany or similar will be stout enough. Top end fastenened to beams by small pad with hole for the post, bottom end on to a floor or bridge between two floors. On a plastic boat, glass in a couple of large pads to spread the load.
Redecking would only be a last resort, and the new beams will only sag again, unless you improve the design by adding to the structure. I am suprised the bulkheads don't help in this way.
 
The mast is just aft of the nearest bulkhead annoyingly!! but is stepped on a large plate to spread the weight but that doesn't seem to work as the middle beam seems to take most of the load. The problem with putting a pair of post's in is the access to the heads, a post would get right in the way but would certainly solve the problem.
 
[ QUOTE ]
A pair of posts each side of the companionway is easier than beefing up the beams.

[/ QUOTE ]
I agree. Border Maid was changed from a keel-stepped to a deck stepped mast, and the coachroof rebuilt, sometime in the 1960s. The mast is supported by two rather elegant laminanted posts at the ends of a pair of staggered half-bulkheads, thusly:
[image]
Beams.jpg
[/image]
The mast is stepped on top of these posts on a couple of lengths of s/s angle and it seems to have been a good plan.

Hope it helps.
 
Hi there again,
a heavier section beam could be produced (the right curve) and located alongside the distorted beam, this does not have to be full length, but the longer the better, particularly if it could land on the extreme beam shelf or be supported on the shelf with blocks etc. The beams could be bolted together after jacking up the sagging beam as best if there is no way of installing compression post/s. This would help I am sure. The beam could be laminated or sawn, but if sawn, something like oak would be best.


John Lilley
 
Thank you everyone for your input.....really really useful. The photo of the two posts helps as well. I will probably beef up the exsisting beam and try a put a couple of uprights in to. She is in a shed this year (Lathams, Poole) which will really help work progress!
Thanks again.
 
How about a demountable post, which could be fitted in place as part of the preparations for going sailing, and taken out and stored when you're having an evening aboard. Using the heads when on a passage might be a problem, but not one that couldn't be overcome by heaving to, which would also be kind to the occupant of the heads.
Peter.
 
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