Compression post - Replace or not?

[Charlie98117]

I have a Hunter 34, they have a known issue with water intrusion below the mast step that leads to a project to fix the damage. Typically the problem is wood blocking in the fiberglass beam rots and compresses resulting in bulging fiberglass and sometimes the compression post rots too. The fix is substantial since you really need to hog out all the rotten wood in the beam.

I had a bulge which led me to believe it was a sign I had the rot and the problem was only going to get worse. I haven't tightened up the shrouds because I didn't want to put added force on the post. I've scheduled a mast unstepping for 2 weeks out and lined up a rigger to replace all the 30 year old standing rigging. Today I went out to get started opening up what is necessary to remove the post. I removed the backside trim and what I see is making me think there really isn't a problem other than some crappy production line workmanship.

The wood compression post doesn't really show any sign of water stains and what I see on top of the post appears to be a piece of thin plywood used as a shim. I think this is the only thing that has deteriorated and compressed. I don't see any sign of deformation of the fiberglass beam. If I tap along the length of the beam I don't hear any hollow spots. I won't know for sure until I get it out but it looks to me there really isn't any structural damage to repair and I think this project just got a whole lot easier.

 

[kloudie1]

Since you are that far along, it would be good to investigate a little further.. Attached picture of my post shows no damage in the parts you can see in your post right now.. but as you can see, there was a rotted section that had not progressed far enough to see without removing the post. I routed out the rotted parts and replaced with a carved oak plug that was epoxied in.. then treated the whole thing (not the teak wrapper) with copper napthenate. The crack in the glass beam where it meets the door trim looks pretty much like mine did.. attached picture... and the wood in the cross beam was totally rotted.. If there is no damage at all in your post top, then you probably are OK, but look very carefully.
.

 

[Charlie98117]

Thanks for the photos Claude. I did study your 2010 thread but don't remember seeing the photo from the backside. It looks like you had a lot of deformation of the beam and is that a wrinkle in the frp at the top? The bottom of the beam on mine does look straight from both sides. I will at least continue with the plan and remove the post, I have an 83 with the large mast step so maybe I don't have as big a problem as some of the later boats. Definitely will pull the mast step and look over everything from the top while I'm at it. I just don't want to tear it all open if there is no reason.

 

[Charlie Jones s/v Tehani]

There IS a reason. Peace of mind. Investigate, and repair while on the hard. So much easier than having something go wrong with compression post while sailing

 

[kloudie1]

you are correct, Charlie.. I had a slight wrinkle in the front part of the beam that was hidden by the trim, and the bottom was depressed a bit.. I noted that yours does not show those, but the crack on the front, over the vertical trim, is a very first sign .. The large mast steps didn't seem to have as much trouble as the short ones.. ya may have an opportunity to dodge the bullet.. Glad you decided to check the post top..

 

[Allan12210]

The problem will probably continue to progress, especially when you tighten the rigging back up to spec. Then it will loosen again, and you will tighten, and so on. In my case, the top of the post did not deteriorate as I did not have water intrusion, but the crossways piece of lumber in the beam compressed. Too much of it had been removed to allow passage of the wires that the load was concentrated in a small area. Note the pronounced curvature in the wood at the notch. Granted, I have the small mast step plate, but still, I think you are seeing the same effect. Once you pull the post, maybe you can use an inspection camera to look up inside the area and decide on what to do next. Its not necessary to remove the bulkhead like I did unless the beam is completely fractured and has to be repaired.

 

[Charlie98117]

Allan, are you saying all that damage occurred and you had no water intrusion at all? Seems like a workmanship issue with the wire routing. Hopefully mine is not so serious, the beam itself shows no deformation at this point and it taps out solid. When I get the post out is the opening for the wiring big enough to get an inspection camera in?

 

[markwbird]

I have done this repair as well. Wood rot is not necessary the problem. In fact I would say that it is usually not the problem. It is poor construction. The bearing area between the header beam and the top of the compression post is too small and it crushes the wood. My repair was less extensive than most of the others that you can read about here. I screwed a 1/4" thick steel plate to the underside of the header beam to bridge the gap created by the channel cut in the beam for the wiring. The plate is the width of the beam and about 12" long.

 

[Charlie98117]

I'm starting to dismantle the bench seat for removal of the compression post but not sure how much I need to take apart. It looks like the top and end panel need to come off but it appears the top is held on by screws from the underside that would be a bear to remove. Can anyone recall the best way to open things up enough to expose the wiring at the bottom and remove the post?

The mast comes off tomorrow, excited to get this project underway!

 

[kloudie1]

top has to be unscrewed from inside the storage cubby on starboard; tough to access. It will try to jam and won't want to come out but go slowly and wiggle the top and it will slide aft and out.. then the "L" shaped part, the end panel and the aft panel should come out as a unit. On mine, I needed a 14 inch philips head extension for the screws next to the keel. The wood jumble picture is all the wood parts that had to be removed, stowed in the vee birth.

 

[Charlie98117]

Thanks Claude, photos always help. I haven't looked closely inside the storage cubby but I can feel the top extending inside so I will look for those. I think I can also feel 2 screws alongside the holding tank that appear to be holding down the top from below. Do you recall anything there?

 

[Charlie98117]

Had a busy couple days but the mast is down and the compression post is out. What I found is not bad at all, the wood is solid and there appears to be no issues with the fiberglass beam. My post was not carved out as bad as others I've seen so the bearing area was not compromised. I don't think it was bearing properly though because of the lump of wires they pinched between the post and beam compressed. Yeah, really. It appears to me all the settlement I see can be attributed to the wire loom flattening and compressing into the top of the post.

The only thing I can see on the top of the post is an indent where the wires were squished.

The fiberglass beam shows no sign of deformation and the moisture meter looks OK so I'm thinking I'm just going to put things back together, replace and reroute the wires, shim properly and call it good.

 

[jibes138]

Try G10 for the shim material. Stuff is hard as a rock and won't rot

 

[Charlie98117]

Try G10 for the shim material. Stuff is hard as a rock and won't rot

I was thinking of blocking off the perimeter and injecting epoxy. Seems like that would get full contact and fill all the irregularities.

 

[jibes138]

Just plain epoxy may not be very strong. Strength comes from the reinforcing fiber and the higher the reinforcing material as a percentage of the total the stronger the layup. Better to at least get some cloth or chopped fibers in there to strengthen it.