Compression post rotten

[Alctel]

While my mast is down, I took off the teak casing on the compression post and jabbed the wood underneath with a screwdriver and found this

The top few inches is dry, but rotten. Strangely there is no sign of sagging around the mast step.

Can I just chainsaw off the top 6 inches and epoxy on another block? Or even just fill with thickened epoxy? Or should I replace the whole shebang?

 

[rbyham]

Gotta wonder about initial cause of this rot. Must have been some water intrusion at some point. If the rest looks good I would cut out the rot in a squared out shape and epoxy in a new block.

 

[Alctel]

The wiring from the mast wasnt sealed properly.

 

[kloudie1]

Compression Post Top Rot

I had only a small top rotted spot on mine when I re-did the cross beam.. I routed out the bad stuff and made an oak block to fit.. then soaked the block in the green wood preservative .. soaked the innards of the teak-faced post as well then epoxied the block in place after a few days of drying in the sun.
As long as you are sure that the water has been stopped, a well fitted plug block epoxied in is a great fix.

 

[rardiH36]

Alctel:

Can't help with your question, but thanks for posting your findings. A few questions from me:

- Any issue to remove the teak fascia board? I presume just carefully remove the bungs and unscrew? Any glued parts to contend with?

- Do you have any idea what is inside the liner channel above the compression post. i.e. just to the left of the dome light? Must also be some sort of block to further allow compression from underside of the deck to the actual compression post.

- Just in case you haven't, have you also checked the condition of your mild steel compression pipe in the bilge? I've posted a couple of pictures of mine.

 

[Alctel]

Does anyone have the original measurements for this thing? What was it made of, pine?

Also, to questions,

- Nope, no glue. The screws are really soft so easy to strip, so be careful.

- solid fibreglass I think. I'll have to go check.

- yeah, checked it last year. Rusty, but I have off all the rust and it seems pretty solid still. I will seal it at some point.

 

[rardiH36]

Alctel:

Thanks for your information. Will be helpful for the day I might need to dig into the area. Or with your findings, maybe I should do it sometime soon. Just to check if my boat is OK ... Or if not, get the area shored up before serious issues develop.

 

[DianaOfBurlington]

Make the block-- for now.

Can I just chainsaw off the top 6 inches and epoxy on another block? Or even just fill with thickened epoxy? Or should I replace the whole shebang?

I like the idea of the new block. It might be a little unsightly but that could be remedied with creative woodworking.

In making the block, use similar wood (teak or mahogany) or else something like white spruce. DO NOT fall into the too-common fallacy that pressure-treated yellow pine from HoDePo is appropriate because, after all, it's already 'rot-proof'. Pressure-treated yellow pine has NO place whatsoever on any quality yacht... period. (Especially NOT in compression! --yikes.) I'd use good mahogany; teak being a second choice.

Also, align the grain the same way. People will say this will be bad; the two lengths of wood will mash end-to-end and some length and strength will be lost. This is true any time you attempt to butt wood together for a compression load. The proper thing here would be to make a scarph joint; but we don't want to have to derig the boat and remove the whole post for this.

(That said, it may be easier-- check and see if you can't just remove the post from the bulkhead as with my H25.)

So, to install the block, chopsaw about 1/4" off the end of it and epoxy to its bottom end a 1/4" block of fiberglass board-- preferably Garelite G-10 or that red electrically-insulated board. You can get either in a vast variety of sizes from McMaster-Carr in NJ (mcmaster.com. They ship promptly, anywhere). This will work well as a dam or butt-block to separate the two pieces of wood and will work very well in compression, such as for mast steps, backing blocks, or like on our C44s the ends of the bowsprit. With the top of the post cut cleanly and all three pieces thoroughly treated in WEST epoxy, you shouldn't have a problem.

At some later date, consider taking down the mast, to relax the loads, and making an all-new compression post. Chances are it's only screwed to the bulkhead, stiffening the plywood which takes all the load. Mine's like this; it's a common structure. Kept in column, plywood is actually pretty good in compression. The post can be made about 1/8" too tall and installed with the help of a mallet, so long as the plywood-deck tabbing will allow it.

While you are looking at mcmaster.com, consider a piece of Garelite tubing for the wiring. A short length can be installed through the deck structure, using plenty of epoxy and making a smooth fillet around its perimeter to keep water away from the tube itself. This should protrude as far down below the cabintop as aesthetics will allow, to keep any dripping water away from the underside as well. Just make sure there's a place for drips to drop away from the lower end of the compression post. If you have enough slack in the wires, fashion a drip loop inside the mast, able to be formed with the mast hanging by the crane about 6" off the deck, and then wrap the wiring and the top of the tube with electrical tape and/or butyl tape before the spar goes down. The drip loop can be tethered with lightweight cord to a blind screw in the metal mast step, to keep it in position as a low point.

 

[Alctel]

Hey guys,

Ended up using fir, as that was what the old post was made of. The new post was all one block, and I didn't bother cutting a wiring slot in in like the old one - in fact I completely epoxed up the hole in the mast shoe, I will run the wires out a hole in the side of the mast, through some hose and into a through-hull installed in the cabin roof. Should keep everything waterproof.

I made a blog post on it here, with some pics http://www.gudgeonblog.ca/?p=1490

Of note - the roof structure of the H36 is so damn strong it was managing to hold up the entire mast with virtually no sag, entirely by itself (helped slightly by the thin teak coverings on the post)

 

[Alctel]

Alctel:

Thanks for your information. Will be helpful for the day I might need to dig into the area. Or with your findings, maybe I should do it sometime soon. Just to check if my boat is OK ... Or if not, get the area shored up before serious issues develop.

Didn't see this the first time round, but yes. I'd check if you haven't checked it for a long time.

The H36 were built strong and in my case held up the mast by the roof alone for goodness knows how long, but it's always nice to have piece of mind. Probably takes a couple of hours in total to remove the teak facade, check, and then put it back.