Compression Post Blues

[sea yawl]

Sailors,
I would like to hear from some veterans of mast compression post problems.

I am looking at a Southern Cross 31 with lots of deck crazing,
cracking around stanchions etc. A survey has turned up no concerns
about deck or hull integrity. My concern is the apparent slight
crushing or dishing of the cabin top in the area of the mast step.
Also, there are parallel cracks in the fiberglass surface where the
cabin top meets the deck in the area of the mast.

The survey did not determine a reason for the dishing. The surveyor
looked for but did not observe a compression post problem.

First, does deck dishing around the mast step indicate a serious
problem?

If so, might hidden compression post problems exist that require
disassembly for observation? What parts of mast removal and
compression post disassembly require yard expertise and what parts can
be done by a do-it-yourselfer? What $ values might be assigned to
different repair scenarios?

Any light you can shed is greatly appreciated.

Jim Lavery
s/v Polar Bear

[Portobello]

Hi Sea Yawl - a previous boat of mine had a similar issue. Mast deck stepped - steel post to keel yet there was a slight concave where the mast met the deck. I could see no way that any of it could compress without some serious distortion of the post. So I was at a loss. I bought the boat anyway and had no problems. If your post is wooden then there could be movement or, similarly, if there is a core in the deck that has compressed that could cause a slight depression. None of it would be difficult to rectify for a reasonably handy person. Good luck with it.

[Stillraining]

Jim..He should have had a moisture meter with him ..what did that show in that area?

I had a small dishing under my mizzen mast step on purchase and it was the only place on the whole boat the surveyor found any moisture..Sure enough when I had that area rebuilt we found some deteriorated deck coring...Irwin used a method of using small plywood blocking for their cores and an area about 18" in diameter was wet and deteriorating..we removed it all and glassed it up solid.

FWIW..Gel coat crazing ...if not an actual crack deep into the matting is not a real serious condition but more a cosmetic one. It can lead to water penetrating places you don't want it to by capillary action..but generally it is not structural, but does indicate a flexing of the surface below it above what the gel coat can handle over a peroid of time or a gel coat that was laid up to thick in the first place...All can be fixed from the topsid but it is labor intencive....I'v got my share of thoes to deal with as well.

[Celestialsailor]

I'm not sure this surveyor has a whole lot on the ball. The dishing could have been caused by the mast step being too short in the first place or the heel under the mast step having a problem. With the stanchions, water could be softening the deck under them as the are in compression there.

[Boracay]

Is it possible that the compression post has pushed the bottom of the boat (keelson?) down a little and that the abeam sheer has moved inwards slightly?

It may be a good idea to check tabbing and location of the bulkheads fore and aft of the mast, not to mention looking to see if the bulkheads have buckled.

[sea yawl]

Portobello,
Thanks for encouragement. I'm reasonably handy but not sure I want to take this on without a better idea of the actual problem.

Stillraining,
No moisture meter. I watched and listened while he sounded the cabin top. It sounded solid.
Agreed re. gel coat crazing. Not structural but may allow water penetration into core. Lots of work.
If you don't mind, about how much $ and time went into removing the mast, glassing the damaged area, and replacing the mast?

Celestialsailor,
In fact the surveyor suggested the boat could have left the factory in this condition. It's a possibility but leaves unanswered what needs to be done to correct the cabin top distortion.

Boracay,
No obvious problems with bulkheads and tabbing. Might be good to take another look though.

Thank you all for your thoughtful responses.

Jim Lavery
s/v Polar Bear

[barnakiel]

Move away the liners and place long rulers / battens under the mast , just next to the post - is the roof even or has it sagged? If it sagged then there is either an issue with the post (if say wood) or at its food, or under it. If the roof is even then you probably have sandwich roof and the sandwich material has deteriorated and allowed for compression. If so, it is serious and you will have to take the mast out, cut the thing open, replace the core (go for marine grade plywood this time) close the whole thing and then comes the mast on top. A lot of work. And you will need to read up a lot before you go for it - both about handling epoxy and avoiding hard spots, etc..

b.

[SkiprJohn]

Sounds like folks have just about covered everything. I'd check the area just atop the keel for softness and moisture. If the wood compression post extends to that area or if there is some blocking or a bulkhead that might have become rotten or delaminated you've found the problem. You can always solve the problem by replacing any rot or delamination and then if the post is still short shimming it. Are the turnbuckles screwed in to the max? If so, that would indicate that the compression post is compressing too much and there is softness somewhere.
regards

[David_Old_Jersey]

No hands on experiance, but that was no accident as pre-purchase research of my boat model revealed this as a common age related issue. So after researching what it looked like, how to fix and how much I made sure I bought one that a PO had already sorted.

Obviously I don't know how your boat is constructed, but mine has solid GRP decks, except under the mast, which sits on a raised glassed in wooden pad above the forward main bulkhead / main cross beam. Underneath was a wooden mast support (approx 2 inches square) that also formed a part of the forward door frame. It was supported by a similar sized glassed in beam accross the bilge.

The problem was simply due to age and being a tad underbuilt (underdesigned) over 30 odd years the glassed in mast step had compressed, then the GRP cracked, the wooden pad slowly rotted, then compressed even more - the side effect being to weaken the cabin top so it also started to compress, with the mast support not being man enuf to counter the long term process downward..........albeit on mine had not yet got to the stage of actually cracking the deck / cabin top. But that would have simply been a matter of time. Whatever, once the mast starts heading south it ain't gonna later change direction

The solution was to cut out the GRP mast step, replace the wooden pad (soft wood - now marine ply) and reglass (and very neatly done it was ), under decks the supporting deck beam was doubled up in hardwood, with an additional hardwood mast support built in. Going from around 2 inches sqaure to around 5 inches! A might fine piece of varnished woodwork it is and supported by an additional sized piece of woodwork glassed in accross the bilge. (unfortunately I have no photos on this computer). To be honest I think the fix was well OTT!, but I can understand why the PO went that far - indeed not only was the fix in place one of the reasons I bought, the fact it was done so clearly well was a big decider.

The cost? I didn't get the bill but I recall the PO said around a couple of thousand, which kinda tallied with my estimates. DIY? not for me, but fundamently not impossible, although I would put it into the category of "if you've gotta ask............"

BTW one other thing I learnt along the way on the mast compression front is that some setups are designed for a wedge to be inserted either at the foot of the post or at the top - if not inserted the mast is of course then compressing into an air gap..........and easy for owners not to check the wedge is still good, or indeed not to know it is meant to be their at all........

Finally, although not having seen the boat in question I would not be entirely happy with the surveyors comments of seeing no problems, maybe before progressing with an offer bring in a professional to price up the job?

[Stillraining]

3500.00 but I made them give me a no surprises bid so they inflated it somewhat to cover their rear...and they did all the work from the inside..requiring dropping the headliner and lots of trim pieces..
.
FWIW
That's the only way I do business with a yard anymore...T&M does not work for me...Give me a firm price and stick with it or I take my business elsewhere...I'm expected to run my business that way we should all demand they do as well.

Why would I do that you ask and pay an inflated price up front...Try a 6k overage on a 13k estimate with out even a phone call or being told about it because it was a T&M job..that will do it...At least my way I know what it will be for sure from the get go. It has saved me thousands already during this current refit...as they cant pull and shnanigans on me..and yes they have tried..

[sea yawl]

Barnakiel,
Thanks for step-by-step troubleshooting procedure. Very good test for sagged roof. Yes - sandwich roof on cabin - possible core deterioration. Good logic.

SkiprJohn,
Sounds like I need to disassemble entire support system and check all for rot as long as I am in there. Very good thought about checking the turnbuckles. I'll do it.

David_Old_Jersey,
Concur completely: "once the mast starts heading south it ain't gonna later change direction ."
Also, lots of merit to your technique: Let a PO do the repair. I may be someone else's PO.
Thanks for rough cost estimate, and also notes on wedges.
By the way, surveyor looked for problems but could not see, nor could I. Some disassembly may be required to locate the problem(s).

Stillraining,
Great! A hard number. Thanks. That is a big help. Yes I agree, and good point it is better to agree up front to a hard bid than go with time and materials.

All,
Thank you once again for your thoughtful responses and firsthand experience. I have a much better sense about the hardware and how it may go bad, and I have a rough feel for cost. I feel ready to talk to the yard to get their opinion and estimate.