Another idea to "fix" compression post

[Jared1048]

Talking with a friend turned me onto this idea and I'm liking it...

With the mast down take out compression post. Saw off half inch off the top. get aluminum bar (something the size of a chocolate bar about .75 inches thick and 8-10 inches long and about 4 inches wide) and place that on top of compression post and sandwich it in. Add 2 screws to hold the "plate" to beam. Place compression post back now supporting "plate" which is supporting beam.

A small detail that will need to be addressed is the gentle curve of the beam (whatever its called). After The load is off the cabin beam I was thinking of taking some playdoe and making female mold, then making a male mold. Take this mold into machine shop and have them sand the plate to match the slight curve.

I like this idea because of the simplicity of it. Thoughts or concerns?


Cheers,
-Jared

 

[Steve Dion]

I don't think that removing that portion will solve the problem. Most of the time the pine boards that were used to support the mast are also rotten.

Have you removed the teak cover to completly expose the compression post? The teak was only to cover up the pine.

Besides that once you have the mast down and exposed the post you are deep into the project.

There is also a chance that you have rot in the crossmembers too.

The best solution is to replace the post with either aluminum or stainless steel. That should eliminate this problem for ever more.

 

[Jared1048]

I have removed the post before and its fine on both ends. about a year ago I cut out about a 4x4 section of the beam that the post supports and it was wet. I replaced it with an aluminum block that that half an inch taller than what I cut out. I thought that doing this would place 100% of the load on the post but I was wrong. There was still a tiny bit of load on the other two sides of the beam and its cracked at that point to show its being stressed a little.

i'm currently thinking about sanding down that extra half inch so its flush across the beam then doing the "plate" method.

Hope this makes sense. I can post pictures if it helps.

 

[Allan12210]

Jared,

With the plate method you will then be allowing the deck to take the load of the mast. As the wood inside the beam continues to compress through rot or just creep the beam will crush against your plate. That beam is not strong enough to support any significant load. It just gives stiffness to the deck so you can walk around on it. The deck is supposed to float and the load transfers from the mast step via a direct couple (that wood inside the beam) to the top of the compression post. Having that wood in there in that direction (cross grain) was a poor design. The better way for you is to remove your post, cut as small a hole as possible in the beam with a multitool and cut that wood up in there in half. Shove the two pieces away from the opening so you can put a block of aluminum with a hole or slot in it for wires to pass through and glue it to the underside of the deck. That block will be the thickness flush to the bottom of the beam. Then you can use your plate to hide the hole and trim the compression post to fit. With the solid chunk in there you do not need a thick plate...1/4" max will do. With a hole just slightly bigger than the top of the post you won't need to conform to the curve of the beam either. A little bead of white silicone caulk around the perimeter of the plate will finish it nicely. There is no way that plate can move once it is loaded up so no screws are necessary. This way will also require a minimum of machining that will save you money. A couple of holes and that's it. There are discount metal suppliers on line where you should be able to get your aluminum block already cut to the right thickness and plate super cheap. I think one is www.discountsteel.com

Good luck.

Allan

edit...Well that's the problem trying to post using my phone...I didn't see your second post. So most of what I said may apply. When the deck takes the load it will crack as you have seen. Just try to match the thickness of whats inside with the bottom of the beam and your plate should be really thin as it is only to hide the hole.
Allan

 

[Jared1048]

I think we are on the same page.

I'm going to sand the aluminum block thats in there so its flush with the beam then do the "plate" method to support the block and the beam on both sides.

Once I drop the mast I need to find a way to make sure water doesnt sit in there somehow. From the limited number of pictures I've seen I havent noticed any weep holes or routes for the water to escape.

 

[DianaOfBurlington]

Don't put anything in this vital structural chain that isn't adequate for compression. This means not using softwoods like pine or fir, plywood, or plastics like Starboard, and not putting anything flat (so grain can be crushed) or able to shift out under load.

I made a new post out of epoxy-laminated white spruce and shimmed it with Garelite G-10 plate. This was after I filled the (rotten) core of the deck above it. I also have a fabricated G-10 mast base adhered and faired to the deck. Poured-in-place epoxy and machined fiberglass beat metals every time, simply because they're chemically compatible with what the boat is already made of. Take advantage of the available technology, step outside the 'easily known' (i.e., products at Home Depot) and have it right.

I've written oodles about this very topic and it may be worthwhile to search for the archived posts.