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Old 18-12-2009, 12:13   #1
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Deck-Stepped Mast

Do all deck-stepped mast's have some sort of vertical member underneath them (in the cabin) - I think this is called a jackpost?

My mast is on top of my cabin with no visible plate or other means of attachment - it's recessed below the deck slightly, but it can't be that much since there's no significant change in the ceiling of the cabin below it (which has no headliner). There are also no penetrations/bolts/missing fasteners in the ceiling of the cabin to suggest some other member used to be there.

One more question - what is the definition of a 'fair' led sheet - one which does not chafe on anything?
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Old 18-12-2009, 12:32   #2
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Mine has a compression post to the keel.
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Old 18-12-2009, 12:41   #3
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Not all boats have a compression post smaller boats like your often did not but rather had a bulkhead close by, From the looks of it you have an old Pearson? if so you should be able to find some info on the web on that model.

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Old 18-12-2009, 12:49   #4
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There are some wood members around that point (chainplates?) - is that what you mean?

It's a southcoast sc-23 - there is some, very limited info, online

Thanks!
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Old 18-12-2009, 13:12   #5
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Not all boats have a compression post. On smaller boats, the cabin may have enough strength to support the mast. Some larger boats have fabricated beams to carry the load to the hull or other structures capable of handling the compression load.

Your best bet is continue to search for information on your boat and see if it was designed and built without a compression post. If there is no evidence that a post was ever there, it's a good sign that it was designed not to need one.
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Old 18-12-2009, 13:32   #6
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Quote:
Originally Posted by sandycohen View Post

One more question - what is the definition of a 'fair' led sheet - one which does not chafe on anything?
That is correct.
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Old 18-12-2009, 14:52   #7
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a southcoast 23 does not have a compression post, the bulkhead provides enough support to keep the cabin from crushing.
the chainplates are the metal fittings that the shrouds connect to.
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Old 18-12-2009, 15:15   #8
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Thanks Sailmonkey! Does the fact that it doesn't have (by design) a compression post mean the boat is not suited for sailing in certain conditions, or is it equally able to handle vertical and horizontal loads as a boat with a compression post, other things being equal?

Follow-up question - what is holding the mast up? There are no visible fasteners above, below, or aside the mast - is it just standing there on its on weight and the standing rigging tension??
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Old 18-12-2009, 16:15   #9
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Aloha Sandy,
You've gotten some good answers. Most deckstepped masts have some form of tabernacle that the mast sets on or in. Yours might be a stub that the mast fits onto when it is stepped. If your stays and shrouds are ever loosened the little stub (maybe 2 to 3 inches high) will keep the mast base from sliding sideways or fore and aft.
A "fair led sheet" might need to have a few more words around it so as not to be taken out of context. A fair led jib sheet might be one that not only leads clear of all forms of chafe or friction but also led to provide the proper draft in the sail for whatever wind conditions there are.
Any pictures of your mast base?
regards,
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Old 18-12-2009, 16:33   #10
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Hi There - No up close pictures, but I do have pictures of the boat in my gallery on this website.

It's hard to believe the whole thing is just on a small protrusion. When the boat is at rest, none of the shrouds are taught (when I am on a tack, of course one side is taught and the other slack).

Thanks

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Old 18-12-2009, 16:43   #11
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the mast just sits on a little stub, less than 2", less than 1", closer to 3/8". The shrouds, while they may appear loose, won't allow the mast to jump up 1/2" to clear the step. I'll see if I can get a picture this weekend for you, there's a southcoast 23 in, well......lets say distressed shape......sitting in the marina with the mast strapped to the deck.
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Old 18-12-2009, 16:47   #12
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Sandy
Even when you are sailing most of the load on the mast is straight compression or straight down on the mast. The stays distribute and transfer loads to the rest of the boat structure. There are likely several fasteners under the mast that hold the step in place you cannot see with the mast up. These are not necessarily thru bolts as the load on these fasteners would be almost all side shear. Hope this helps

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Old 18-12-2009, 19:21   #13
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My boat has two smaller posts that make a passage to the fore.

b.
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Old 24-12-2009, 16:58   #14
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So the southcoast had already been removed, here's the step from a gulfcoast 22.


Click image for larger version

Name:	<a title=camera dumper 461.jpg Views: 103 Size: 408.3 KB ID: 12060" style="margin: 2px" />
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Old 24-12-2009, 18:13   #15
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BTW a tabernacle is a hinged mast step. which allows the mast to be lowered - going under a bridge.

Often the mast will be fitted over a post that fits inside the base of the mast. This post is fixed to the deck to stop any lateral movement. The Standing rigging stops vertical movement.
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