Comments on Support Under Compression Post

[savagepoint]

I've been wondering what's under the compression "structure" on my S2 8.0B sailboat and what kind of shape it's in as there had been some water intrusion before I re-cored the cabin top. There's always been maybe 1/8-1/4 inch depression in the plywood around the base.

I drilled a hole and put a camera down there today expecting to find some kind of rotting support. What it looks like to me instead is that the one stringer providing support there is in pretty good shape but has either moved or was never properly attached in the first place. Am I on the right track there and any suggestions on an appropriate repair?

Thanks,
-Zach.

 

[bajansailor]

Here is some background info on your boat from Sailboat Data -
https://sailboatdata.com/sailboat/s2-80-b

Is that big lump of timber in the photos the bottom end of a vertical compression post under the mast, or a horizontal member (stringer?) in the bilge?

Re how you had to drill a hole to have a look in the bilge in this area - does this mean that you would have to cut out the sole in the forward end of the saloon if you wanted to get better access?

 

[savagepoint]

Yes. I drilled a hole in the salon floor about 8" aft of the compression post, then put a camera down facing forward. The lump of timber is the horizontal stringer supporting the compression post area: 1st photo is center, then starboard, then port side. It's hard to see but I'd estimate that it's 12-18" long and attached at each end to stringers that run fore/aft and are tabbed to the hull. It appears to slant downward from port to starboard where it almost appears that it has moved pretty extensively.

 

[bajansailor]

Thanks for the explanation - I think I understand it now.
So that timber beam should ideally be in contact with the underside of the sole above it?
If this is the case, then it is not currently providing any support at all.
Is the mast stepped on the cabin top, with a pillar coming down inside, and the base of the pillar resting on the cabin sole?
If so, would it be feasible to leave the existing timber beam (as shown in your photos) in place, and bond (with epoxy) some timber inserts to fill the gaps at the top and bottom?
However this would most probably require chopping the cabin sole out - and if you do this, you can then inspect the beam much more closely before making a final decision.
Or have it got it all completely wrong?

 

[fallguy]

Full on confusion here.

you are going to need to draw it all out and a three view drawing would be best

the part that creates the most confusion is how a stringer would move

if it indeed has fallen over sideways, or was made too short to contact the sole, then it is no longer working as intended, or never did

To repair it, you would need to cut out access by removing a section of sole. Then you would insert a piece of timber bedded into epoxy peanut butter. Or, if the floor timber has fallen over, remove it and bed in a new one which is more difficult to do right.

If you cut the sole away, cut it an inch or two inside of the attachments so you can epoxy glue cleats back in for the sole access repair hole.

Absent a drawing, it is really hard to advise more.

 

[savagepoint]

Yup. That's my view of it - but this is my first time viewing anything under the cabin sole. It does not look like it's providing any support at all currently. Mast is desk stepped with a compression post made up of half a bulkhead and three pieces of hardwood that are screwed together around it to form a strong corner under the mast. To do any repairs, I was considering just opening up a permanent access panel in the cabin sole and just leave that part of the bilge accessible. My questions sort of fall around:

- what would have held that thing in place originally? Seems like at most it was maybe some fasteners and maybe some glue but that looks debatable.
- what would be the recommended repair for it assuming the wood itself proves to be solid. I was considering drilling two additional holes straight down through it and running some bolts through to at least pull it backup tight to the plywood. but re-fastening the ends to the longitudinal(?) stringers I'm not sure what would be recommended.
- the boat is currently on a cradle resting mostly on it's keel - is that good in this case, or should the repair be done when the hull is more in it's more natural state?

Thanks,
-Zach.

 

[savagepoint]

fallguy - thanks for the reply. I'll try to work up some kind of drawing. I don't <think> it flopped over because there wouldn't be enough space for it to stand in the other dimension. it's actually a fairly wide timber. I guess the next step is to just open it up and determine that for sure. And yes - the idea that it moved at all just isn't seeming right although there's maybe some evidence of that on the starboard side of the stringer, where it almost looks like it slid down and a fastener started to show through the top. I'm just thinking it came unglued at some point or was never in contact to begin with.
-Zach.

 

[bajansailor]

If you can open up the access to this area, I think you just need to make sure that the whole space from top to bottom is filled with timber, bonded in properly.
Then it will all be in pure compression, and it will have enormous strength, and nothing will be able to move or break.

In addition, re the three pieces of hardwood that are screwed on (are they just facia / trim pieces, or are they structural?) in way of the aft inboard corner of the heads bulkhead, it might be prudent to unscrew them (if this can be easily done) to inspect the condition of the wood underneath.

 

[Blueknarr]

I would drill a camera hole on the other side.

I think it is construction error and the under sole support never happened. The beafed up bulkhead is transferring the whole compression load the the side hull.

REMOVE the mast before any support is taken away. If those trim pieces are structural, then removing them with the mast in place could be BAD.

Bolts thru the sole will hold the beam in place while FG tabs cure.

Repairing on the hard will probably facilitate mast removal and replace. Otherwise no preference for in water or on land.

Good luck

 

[savagepoint]

Yeah I should have mentioned earlier that the mast is off and she's on a cradle on my lawn at the moment so probably the perfect time to address this. Seems like the bar is pretty low here to make it better than it currently is so I'm going to go ahead and open up an access panel following fallguy's advice and get my hands, tape measure, and a better camera on it and then I'll report back. One way or another I'll get photos from the forward side too. The keel is an encapsulated lead keel/bilge area. 1-2ft aft of the compression post area there is a plywood bulkhead under the cabin sole that is tabbed to the hull and cabin sole for support. Even if this timber stringer from the photo were properly glued in place, the compression load would be on it and the longitudinal stringers and side hull. I'll report back with better pictures, but I think this area is actually forward of the actual "lead/heavy" part of the keel so if I were going to add extra support under that timber, it would basically be going straight down and tabbing in to the hull/leading edge of the keel like another bulkhead.

-Zach.

 

[fallguy]

Can you add pictures from above here?

 

[gonzo]

If you are going to cut a hole, might as well cut it over the affected area so there is access for repair.

 

[savagepoint]

Hey There,
Sorry for the delay. I just found time today to cut that hole and take some pictures and measurements. The first photo "access_hole" is from the salon looking forward at the bulkhead that forms the wall of the head. The two hardwood trim pieces that form the corner along with a third inside the head sandwich together with the bulkhead to form a "compression post." The "beam" in question that supports it under the floor is actually a 1-1/4" x 6-1/2" board lying flat against the 1/2" plywood floor between two stringers that run fore-aft and are tabbed into the hull. The "beam_stbd" and "beam_port" photos show the different amounts of separation from the plywood on each end. There's no way it ever stood vertically, there's no where near enough room. Lying the way that it is, there's only about an inch between it and the hull at each end.

If that board was ever glued in place it was really superficial. I can relatively easily move the end that is separated on the starboard side but I can't really move the end on the port side at all. I suspect there may be some fasteners involved before they laid the cabin sole down. I put the bottle jack from my truck in there and I can push it back up - to a point but can't make it flush against the underside of the cabin sole because the plywood has been depressed about 3/16" directly under the compression post and I think it hits and pushes there first. There's a little water damage to that cabin sole plywood, but I don't think a lot. It's solid - just deflected a bit.

All of the timbers down below including the one that came loose look to be in great shape. Certainly never know they spent 40+ years in the bilge of a boat. I don't believe that support board can come out/be replaced without cutting it down the middle. It's just too tight and too little space to move it.

I'm wondering a couple of things:

1) if I were to leave some pressure on that with a jack under there for a while would that deflection in the cabin sole plywood ever straighten out?

2) Since it's in great shape, how would you feel about pushing some thickened epoxy in there, pushing it up as far as it will go and then tabbing the ends of it in with fiberglass.

3) in one of my earlier posts I was wrong, the bilge directly under the
compression area over the keel is horizontal, flat, and hard enough to probably be the surface of the encapsulated lead keel. I could add a post coming directly up from that, or a thick bulkead in there to add support.

Thanks for any input you have on this.

-Zach.

 

[Blueknarr]

Thanks for the update.

My solution

-Look for fasteners and remove loose board.
-Sand mating surfaces clean.
-Epoxy and screw it back into place.
-The gap shown can be filled with thickened Epoxy.
-Add post directly under mast
-Replace soft sole.

It is a lot of work with lousy access. The bulkhead is probably going to still do 100% of the work. Better safe than sorry.

Good luck

 

[DogCavalry]

If it has been fine for 40 years, it's a non issue.
Tap in a composite shim in the middle to open the gap a little, and load it up with cabosil thickened epoxy. Push it in hard with a small trowel from the side you can access until it comes out the other side. Close it back up again. Better than new (because new was wrong).