Houston, we have a Problem - H36 Compression Post

[chichiflys]

Well, I think I have officially joined the club. Apparently a club that seems to be reserved more for H30 owners, but nonetheless, it's a club with many members. We have a 1982 H36, owned previously by my folks. The old man made many upgrades and took tremendous care of this vessel. One aspect of that it seems to have experienced the end of it's lifespan.
The sub-sole mast support post of the H36 apparently was different then the I-Beam approach used on the H30s. In our case, it was a cast-iron tube, encapsulated (I think) in fiberglass on the bottom, and bolted to the underside of the cabin sole on top with a plate welded to it. Many years ago my father realized the post was rusting due to a water leak, so he wrapped the post in fiberglass and filled it with resin. He seemed to think it would give him some time...well 30 years later it seems to have started to fail. My "should I be concerned meter" is at about a 9.9 out of 10 at the moment after reviewing current pictures and seeing what appears to be buckling and compression failure of the post and resin concoction. I have searched the forums and read many tales, mostly concerning H30's. I realize the fix is similar regardless of specific boat type. But whilst I search for a boatyard with space that I can put her on the hard, remove the mast and get to work, anyone have any H36 specific tales to share?
My present plan, is to remove mast (yes I've seen a post or two about fixing this without un-stepping the pole, but I actually have a few other things that could benefit from having a mast on the ground so I plan to take this more costly approach), remove the trim/casing around the wooden post if nothing else to inspect the wooden post between the cabin top and cabin sole, and then remove/replace the failed/rusted iron post. My initial thought was to replace it with an aluminum or SS item, but reading Diana's posts from John C II, made me contemplate a more intricate fix of structural stringers, etc. But I'm not sure how realistic that is on a H36.
So until then, what have previous H36 owners done in this situation, if anything? I apologize for the pictures, I will gather more tomorrow, but for now I can see what appears to be a bucking of the iron/fiberglass....which may explain the "wrinkling' I've recently noticed on the cabin top just aft of the mast...Thanks!

 

[David in Sandusky]

There are lots of us with 25, 27, 33, and 37c Cherubini’s. I don’t think many 36’s were made, but we have some on this board. It may just take a little longer to hear from on of them.

Welcome in any case!

 

[David in Sandusky]

Here is a thread of h36 owners discussing your issue:

1980 Hunter 36 mast step

I decided to teach myself to tune my rigging. I get to the first turnbuckle and it is adjusted fully in. I had it looked at by a rigger and he said the mast step needs to be replaced. When I looked at it, the piece below the floor, it is badly rusted. Odd the surveyor didn't mention it. Before...

forums.sailboatowners.com

 

[chichiflys]

Thanks David - I've now aded Rardi's thread to my bookmarks....lots of reading to do.

 

[RoyS]

I had to replace my 1980 H33 compression post. It was structural aluminum tubing and not cast iron. Serious corrosion was caused by a copper ground strap attached to a keel bolt. Made a nice battery in the salt bilge water. By all means remove the mast first. I used an adjustable lally column to stretch the cabin top up a bit to swap out the post. Bought the post made of the exact same material, cut to exact size from Metals Depot. Good luck.

 

[chichiflys]

Thanks Roy - that's some pretty gnarly corrosion. I appreciate the input, this will be a fun one!

 

[Dalliance]

I have one of the later H30’s with the crazy steel tube structure extending out to the chainplates, but my recent solution to deal with the corroding base plate & bottom end of the vertical tube below the compression post may be relevant to you.
Last spring, with the mast down, I cut out the bottom half of the post and base plate and created a new corrosion proof base of high density G-10 fiberglass. It’s a stack of 3/4” & 1/4” G-10 sheets cut into 3” squares, epoxied together and set into a bed of thickened epoxy. The two thicknesses provided height adjustability. The bottom end of the cut off steel tube is socketed into the top and set in 5200. I think you could do something similar with a full height post to the underside of the cabin sole.
In hindsight, the only mistake I made was cutting G-10 with a sabre saw instead of a circular saw. The material is so dense (You can actually drill & tap it for bolt connections.) that the blade flexed and I ended up with sloppy cuts. Still functional, but not my normal standard of workmanship.
The extra nuts on the keel bolts where just to protect the threads from the saws-all blade and epoxy.

 

[chichiflys]

Thank you Dalliance - interesting solution - definitely rot-proof I'd think. Also great idea on the keel bolt protection. I see a few sawz-all blades in my future. The iron post I have is filled with epoxy resin, will take a while to hack through it.

 

[chichiflys]

Did a little exploratory surgery today - was cold and snowing so didnt spend too much time...was able to remove the forward trim piece covering the wood post between the cabin top and cabin sole. While there is clearly evidence of water leaking at some point it was dry and in good shape soI hope that is just an old leak which caused the original rusting of the pipe...I'll need to check during a good rain to see if there is any more water coming in. But hopefully there is no need to mess with that wooden post. Got a better look around at the rotting iron pipe underneath the sole. There is an access plate located in the shower basin I think Rardi alluded to - I'll need to sacrifice it in order to remove it as it is severely bedded to the floor and will only come out in pieces; but fabricating a new one is the least of the problems. Hope to get that plate off soon to see what kind of maneuvering space I have for the tools needed

to cut out the old pipe once I get her on the hard and de-masted.

 

[chichiflys]

Was able to remove the shower pan access plate. Much better visibility of the post area as well as more damage evident. This is looking aft as well as a shot looking up/aft. Tossing around a few ideas for a repair, assuming I can remove the old stuff, remove/clean a lot of the material on the bottom portion and smooth the hulls sides. Was contemplating combining a joist (laminated mahogany boards) support idea that John C. II recommends with a jack/screw using a 1" or even larger SS bolt with a plate welded to the top (see .pdf)....perhaps it's overthought but I like the idea of being able to adjust the height of the support vs. trying to wedge in a (just the right size) small post, block, tube, etc. with the mast off and boat on the hard. Seems like the hull will deform enough once she's splashed with the mast back on vs. what the hull/keel shape is without the mast when on the hard so being able to tweak the height seems like a good idea. Before going down that road, is a1" SS Bolt with a tensile strength of 70,000psi strong enough to distribute the load to the joist/hull connection? Any Mech Engineers know how to convert tensile strength to compression strength? Again, am I overthinking?

 

[chichiflys]

Scrapping the jackscrew idea.....latest brainstorm is to bond some joist/stringers to the hull using 1" Coosa board, 2 of them (if not 3) than top it with a single Cossa board (like a box). Then sandwich a Cossa or G10 support piece between the joist/box and underside of cabin sole. Rot proof, no metal to corrode, lightweight, should be significantly strong with the mast compression load dispersed to hull sides. Just hope to have the room to work it in there. I'll de-mast the rig, and do the work with the boat in the water vs. on the hard with a potentially deformed hull/keel/cabin sole, etc. Hope to video and document well.

 

[chichiflys]

Had the mast removed today, began the cutting of the pipe, several blades to get through the epoxy....will need more. Almost made it through and then the blade got pinched, so it must still be under some compression load despite the mast being gone. Will purchase more blades (recip saw) and commence the cutting. Probably will need to make another cut a few inches above this cut and remove a section of the pipe, then hopefully can pry it off the underside of the cabin sole, I suspect there is some 5200 or something waiting for me there.

 

[Dalliance]

Had the mast removed today, began the cutting of the pipe, several blades to get through the epoxy....will need more. Almost made it through and then the blade got pinched, so it must still be under some compression load despite the mast being gone. Will purchase more blades (recip saw) and commence the cutting. Probably will need to make another cut a few inches above this cut and remove a section of the pipe, then hopefully can pry it off the underside of the cabin sole, I suspect there is some 5200 or something waiting for me there.

Maybe you can wedge in a temporary block of wood or a small jack. It took two cuts with the SawsAll to be able to pry my post base out.

 

[chichiflys]

Finally able to remove a section of the pipe, horrible job at an even cut, but shouldn't matter so long as I can remove the remaining upper portion that appears to be adhered to the underside of the cabin sole. Baby steps (and lots of recipes saw blades) I guess. Time to wedge a (mini) crow bar....Plenty of metal left (measured 1/4" thick walls) on the pipe towards the upper portion, down to less than 1/8" remaining on a portion of the pipe that was near the base. I suspect this pipe was still fairly strong and that the base that it is bedded into was failing, hence the cracks and sunken depression evidence all around it. I think this is a good example of why John C II doesn't recommend using the keel as a support for the mast....

 

[chichiflys]

Slow progress to some degree. Realized the upper portion of the post is epoxied to the underside of the cabin sole, it is not coming off. So I cut out another 2” off the upper portion of the tube. It’s as far as I can reach to cut it. Nearly impossible to accomplish in such cramp quarters, as such the cut is not level, but better than earlier cuts. Now I’ll dig out the rotted bottom portion that is buried in resin, and god knows what else. Also attempted a quick template of A joist, needs adjusting but it pretty close for a first guess.

 

[chichiflys]

More progress. Was able to cut out the "stump" that was adhered to the keel. Still some cleaning required, but forward movement nonetheless. I'll fill in the area with new resin and glass to smooth it all out. Mockup of a joist plus a partial "box" to cover the upper post remains which will give the upper portion an even surface to which to tie into the joist...somehow. Either a jackscrew or G-10 boards stacked or on edge (or both). The upper box will be made out of 1/2" thick G-10 board, and then filled with epoxy resin and inserted around the upper pipe extending from the sole floor...if that makes any sense.

 

[RoyS]

If you intend to form a solid base that spans the bilge you can wet out a piece of fiberglass cloth, wait until it starts to set, then bond the bottom edge to the bilge base and prop up the rest to make a dam on each end of your envisioned base. After that sets up completely you can mix and pour and fill the damed area with epoxy thickened with structural fillers to make a solid base. You have to be careful of the epoxy heating up too much but small batches poured in over a few hours will work fine. If your solid block will cause your bilge to have a separate area of trapped water place a piece of 1" pvc pipe on the bottom that connects the two sides and then pour the base. G10, on the other hand, is difficult to shape.

 

[chichiflys]

Thanks Roy. Ideally I can bond the joist to the hull sides and leave a space at the bottom so that it doesn't rest on the bilge area - this will allow a way for water to move aft...other option is to just bond a post to the bilge as was originally done by Hunter - supposedly it's not ideal but seemed to work for 40 years without any structural issues....

 

[chichiflys]

About ready to clean up the bare bottom, add resin to fill in all the crevices and embed a 1/2 plate of G10 (5x8) to create a level spot on the keel floor. Most likely I'll install a short post on the keel and use this to house the screw jack/bolt. I found some cedar with which we'll construct a 4.75x4.75 post with a hole in the middle for the screw/jack bolt assembly. If this works well I may use this or construct a box out of 3/4" G10 just to get any wood out of the bilge (although the cedar post will be coated with resin so should be OK for a long time). 1:1 mockup of foam board has been fitted and seems to be OK. The joist idea hasn't been eliminated yet, but it is proving to be a challenge to get a good fit as the hull sides are so complex and it's very difficult to work in there. I still need to install a box around the upper post that remains (mock shown on the top part of the pictures). This will be constructed of 1/2" G10.

 

[Dalliance]

Thanks Roy. Ideally I can bond the joist to the hull sides and leave a space at the bottom so that it doesn't rest on the bilge area - this will allow a way for water to move aft...other option is to just bond a post to the bilge as was originally done by Hunter - supposedly it's not ideal but seemed to work for 40 years without any structural issues....

This was my conclusion after also exploring spanning the bilge with a glassed in stringer. Really hard space to work in and, while the post is unconventional, it has worked for forty years. It just needs to be corrosion and rot proof.