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SkiprJohn · 13-11-2011, 15:14

I don't know if anyone answered your question about flexing but it should not. My boat had the same problem when I first bought it and I traced the whole thing down to a rotten block in the bilge and the douglas fir 4x4 compression post. I replaced the block with teak and replaced the douglas fir with stainless square tubing. Should be solid from keel to mast.
kind regards,

David_Old_Jersey · 14-11-2011, 04:10

Quote:

Originally Posted by boatman61

I used 2 section of scaffold poles and collar... threaded on one end and a plate welded to the other...
Screw the collar right down on the lower(Keel) piece then attatch the other and adjust till happy.. need to measure up right..

Did it on a Hurley... worked a treat..

Mind... I had cut out the non crucial bulkhead...

That'll be tucked away for future reference

Mast post compression is a common "Feature"

on my model of boat (30' Seadog - 1970).......I did a lot of research at the time on what is a good fix

vs a bodge

.........and bought one that had already been fixed

(and fixed visibly well - in fact a little OTT

).

Note the beam bracing under the post.

The original bracing is the (top) lighter coloured wood.

Not 100% finished off yet (I have a list of those jobs

).

The post is not solid wood but four pieces of hard wood (not plywood) that have been glued (epoxied?) together into a hollow box. The only reason I know this being that I drilled in to fix the door hinges - have looked very closely a number of times and still can't see the joins

.

The puzzle I was left with was how to rehang the door (door hole now being an inch smaller)......a lot of puzzling on that (but the sort of thing I love

). Ended up with the same sized door

, a bigger (usable) door frame and better forepeak coat storage

Door got moved forward a 5 or 6 inches, fold back hinges fitted to the (new) Mast post....and built a new starboard side door frame........which was it's own puzzle

David_Old_Jersey · 14-11-2011, 04:18

Just to mention that on some older boats the practice was to have a wooden wedge between mast post and under deck......the idea being that it could always be "adjusted"

. and indeed needed to be to stop it simply working out. A hangover from all wood construction I guess.

In practice what tended to happen was that a few PO's down the road that someone spent years puzzling over what that wedge they found on the floor was for

.......and the resulting air gap between mast support and deck gave predictable results.......

TassieBloke · 14-11-2011, 04:33

Look, i am going to jump in here to say just and say a few words as an Engineer. You really need to transfer all the load from the mast to the hull in the bilge, which orsirissail has eluded to.

A SS compression post has been mentioned, and I would seriously recommend this as a permanent solution, rather than to rely on wood which may, or may not rot over time, thus perhaps repeating the exercise again in a number of years. Even a just a 1" dia thickwalled section with proper plates top & bottom will do the job nicely. As to the 'truss' bracket thing, if you choose that path, then put another bracket on the opposite to balance the buckling that a single bracket will induce into the wooden panel (this is due to a number of reasons outside the scope of this discussion).

One thing that has not been mentioned so far, is the potential ingess of moisture/water into the area surrounding the mast/deck interface. Have you investigated if the moisture has travelled further afield (based on the assumption that the deck is cored with some sort of material, rather than solid).

Hope this helps somewhat.

Bloke

SkiprJohn · 14-11-2011, 10:37

The reason I don't like the bracket idea is that I'd be constantly running my head into it unless it was protected with a bulkhead of some kind. However, it would make another handhold?
kind regards,

gixerjen · 15-11-2011, 14:56

Wowsers! Guys, thanks a bunch - I really appreciate your opinions and advice!

All of them....

Quote:

Originally Posted by Charlie

I am not familiar with the type or size of boat so the pressures may be too small to worry about deforming the timber.

I think I have a plate if you want me to draw a picture ?

Given that the repair I've mentioned which was carried out by a member of the owners club, was approved by his surveyor, I think I should be alright?! That guy seemed to think his repair was stronger than original!

Anytime - tell me what you want drawn!

Quote:

Originally Posted by boatman61

[FONT=Comic Sans MS]I used 2 section of scaffold poles and collar... threaded on one end and a plate welded .......

I believe you can buy those - ackroprops maybe?

Quote:

Originally Posted by osirissail

You might consider permanently fixing the problem by installing a stainless steel tube/pipe between the keel and mast step. This is what you will see on larger boats with deck-stepped masts.

Loved your answer on forces - thank you!

Quote:

Originally Posted by TassieBloke

... put another bracket on the opposite to balance the buckling that a single bracket will induce into the wooden panel (this is due to a number of reasons outside the scope of this discussion).

I get you..... I think? Could I just put a strip on the reverse side? It categorically does not need triangulating there so could I just run an equal sized strip down the bulkhead to stop the bulkhead rippling?

Quote:

Originally Posted by SkiprJohn

I don't know if anyone answered your question about flexing but it should not. . . . . Should be solid from keel to mast.

Possibly, but probably not so concisely

Thank you, that's what I needed to know!

Quote:

Originally Posted by SkiprJohn

The reason I don't like the bracket idea is that I'd be constantly running my head into it unless it was protected with a bulkhead of some kind. However, it would make another handhold?
kind regards,

Ha, I'm 5' 6" so it'd be out of my way!

. . . . Nah, it's be right in the corner so out of the way for the most part.

Several of you have mentioned running a direct line of force from the mast to the keel. On a bilge keel, am I able to just brace down to the sole? Directly under the mast is my bilge, which is partitioned (glass fibre) and to know what's under there structurally I think I'd have to cut it? I can not see a centre crossmember or any other structural part I feel I could brace to??

I am fairly certain that the bulkhead and everything else is sound. I can't work out the reason for the failure - looks like the boat's had previous repair, and as previously stated, it's a common fault (possibly due to off centre bulkhead?)

cburger · 15-11-2011, 15:09

The main reason my new boat was so cheap it that it had a rather dire case of mast compression. It appears to be a common problem on these and the owners club details repair procedure.......

I have been following this thread with some interest. Many of the orignal Westsail boats had similar problems as the main bulkhead was terminated slightly below the deck under the mast allowing for compression of the deck. Bud Tapin the former factory manager for Westsail has descriptions of how to properly fix this problem. I would be happy to scan his writings and get them off to if you wish as well as a couple of pics of these methods to insure a strong load distributing mast support that is currently used on my boat, let me know.

gixerjen · 15-11-2011, 15:14

That would be awesome please! Even if it's not directly applicable, anything I can learn about the design / structure of these boats is definitely a bonus! Thank you very much!

cburger · 15-11-2011, 15:20

I would need to email you the scanned data in a PDF format, please provide an email address, you can send that to me in a private message.

grebowen · 26-12-2011, 22:48

cburger, I have a 26' American Mariner, 1977 vintage, also with mast compression, causing a rippling effect on the cabin roof. The cabin roof is plywood core which is rotten. I think, repair plans in pdf format you mentioned for gixerjen, would also apply to my situation. If you would be so kind as to email me a copy at grebowen@me.com I would be very grateful.

Thanks in advance.....

Greg Bowen,