H30 - replacing the compression post

[H30Gary]

I'm in the process of replacing the compression post / I-beam on my 1980 Hunter 30. Some photos of what I am doing are below. You can see that the old I-beam has rusted and is warping from the off center load on the web. The plywood floor has delaminated and warped under the load of the compression post.

I've replaced the carbon steel I-beam with a copy made from 316 stainless steel. A G10 plate sits atop the I-beam, to replace the plywood. I plan to sister up a new compression post adjacent the old one, so it lies directly in line with the mast and the keel, not off to the side as the old compression post did.

One question I have is how much should the new compression post raise the deck? My guess is that over the years the deck has slumped at least an inch (1/4" here, 1/4" there, etc.) A small bottle jack can easily raise the deck from below by an inch if not more. When I do this however, it lifts the deck off the bulkheads. Is this a problem? I kinda think other than from a visual standpoint, it's not a problem, I'm simply pushing the deck up to where it originally was.

 

[lnikl]

I don't have a H30 but I wonder if you have a door to the fwd berth and if you could jack it until it fits as the door dimensions would presumably be the same as when built

 

[kito]

Based on your first picture with the original I-beam and compression post, it looks to me that there wasn't much sag in the first place, not unless there was rot on the top of the post. The post looks good at the botom and the steel I-beam was still in one piece (unlike mine). If it were me I would just shim under the g10 until maybe it's 1/8" above the cabin sole to allow for the weight of the mast and shroud tension. If the bulkheads are pulling away from the cabin ceiling then my guess is that it's shimmed to much. I am going through this now myself. Not sure why Hunter made the shower drain so it flows past the I-beam in the first place. I plan on extending mine to the lower area of the bilge so my automatic pump will keep my new aluminum beam out of the water.

 

[H30Gary]

Lee -
Good idea, thanks. On the 30 the door is a slider so unfortunately can't tell by it.

Kito -
Yes, I think the compression post settled downward about a 1/4" or so, much less than your case. The post also indented into the cabin top about a 1/4" or so. So maybe my estimate of 1"total settling is too high.

I was very pleased to see as you observed that the compression post is in great shape - no rot whatsoever. Stains were present on the teak at the top of the post suggesting water intrusion, but again there was no rot at all on the post itself.

The water probably was coming in where the wires for the mast light and vhf passed through the deck. These went through holes in the deck which were once sealed with silicone or maybe 5200, but I suspect the seals are no longer water-tight. There was also no way to inspect these seals without pulling the mast. I plan to relocate the penetrations to where they can be inspected, and use some sort of proper thru-deck fitting.

This area of the deck under the mast step has also compressed down about a a 1/4 to 1/2 inch. As far as I can tell, the core is still solid - I've tapped and stepped and drilled inspection holes - it all seems dry and strong with no soft spots. So, wondering what to do. I definitely think the concave area needs to be built up to flat or even a little convex (so rainwater does not collect). So, should I just do that - build up the sunken area, or should I strengthen the core by drilling holes in the region and injecting West Epoxy, then build up the top?

 

[kito]

Just my guess but that concave area is due to core rot under the mast. That's why jacking up the compression post has no effect on that area. Tough call but if it were me I would take an oscillating saw and cut the first layer of fiberglass off the whole top of the raised area. Dig out the wet rotted wood and epoxy in a new piece and the fiberglass piece that was cut out. I just wouldn't feel right about just filling in the concave area with epoxy and setting my mast base on it.

 

[H30Gary]

Kito,
You are probably right that there is some core rot going on. I've drilled into the area and as far as I can tell the core is dry and sound. Can't explain why it sunk in though. In any case, my proposed fix would be to drill small holes in the top layer on 1" centers, fill these with West Epoxy, then build up the top with heavy roving and fiberglass cloth so it is up to the old level or a bit higher. The roving and fiberglass will be pretty thick (~1/2") and should spread the load from the mast step to a bigger area. I'm hoping to avoid cutting the top layer.
Thanks,
Gary

 

[kito]

On my H30 project boat, I have run across plywood that looks sound and dry but can dig it out with my fingernail.

 

[H30Gary]

Today I fit in the new compression post. Its sistered up against the old post, on centerline with the boat. (I had to cut off about 1/2" of the old post to get the new post to be on centerline.) The bottom of the post rests on the new G10 base. The top of the post is currently under the cabin top liner. The liner is a bit deformed from resting on the old post. I plan to install a large 1/4" SST plate between the new post and the liner to distribute the loads to a wider area.

I sealed the ends of the new compression post with West epoxy, but hope to seal the area so water never gets there.

This mod cost about 2" in width of the companionway, but I think it is worth it to get the compression post in line with the mast and keel.

Cheers,
G

 

[hummingbirdbassist]

Had same issue and replaced with similar set up, great minds!!!

 

[kito]

What wood did you use for your new post?

 

[H30Gary]

What wood did you use for your new post?

I used Douglas Fir from Home Depot. DF is pretty high on the charts for compressive strength. As far as I can tell, the old post was DF. Maybe not the best choice, but what I could get my hands on readily.

What did you use? Also, did you extend the teak around the new post?

 

[H30Gary]

One of the things I am glad Hunter did NOT do is glue everything together; parts are simply screwed together, not screwed and glued. This project woulkd have been a nightmare if everything was glued together. But since the parts are simply screwed together, they can be readily disassembled and reused.

Another interesting thing I learned after the fact is that the wood screws on the boat are Frearson Head. These look very similar to Phillips Head screws, but are functionally quite different. A Phillips screwdriver will seem to fit in a Frearson head screw, but really the fit isn't right and the head will strip if there is any significant load on the screw at all. Thats what happened to me on most of the 50 or so screws I had to remove to get everything apart. At the time, I thought the screws were just "stuck" due to old age, but really I was using the wrong screwdriver bit. I wish I had known the difference beforehand, but, live and learn.

 

[hummingbirdbassist]

Gary who built your base? When I started the post 60 minute compression post , I got some crazy private emails, but guy built it for me and installed in about an hour, he made mine quite thicker than yours but theory is the same and very stable! Good work

 

[kito]

One of the things I am glad Hunter did NOT do is glue everything together; parts are simply screwed together, not screwed and glued. This project woulkd have been a nightmare if everything was glued together. But since the parts are simply screwed together, they can be readily disassembled and reused.

Another interesting thing I learned after the fact is that the wood screws on the boat are Frearson Head. These look very similar to Phillips Head screws, but are functionally quite different. A Phillips screwdriver will seem to fit in a Frearson head screw, but really the fit isn't right and the head will strip if there is any significant load on the screw at all. Thats what happened to me on most of the 50 or so screws I had to remove to get everything apart. At the time, I thought the screws were just "stuck" due to old age, but really I was using the wrong screwdriver bit. I wish I had known the difference beforehand, but, live and learn.

Frearson head screws...that's good to know but a little late in my case I have probably removed 300 of them during my restoration. Only stripped the heads of a few but thought it was due to being installed 35 years ago and made from some kind of soft brass or bronze material.

 

[coleman]

...Not sure why Hunter made the shower drain so it flows past the I-beam in the first place. I plan on extending mine to the lower area of the bilge so my automatic pump will keep my new aluminum beam out of the water.

Would any of the shower sumps fit? You could convert just about any sturdy plastic tub (battery boxes come in many sizes...) that would fit if a complete sump kit off-the-shelf doesn't.

This is the one I have (below). H37C bilge is probably quite a bit larger but this is a fairly compact assembly. You'd need the bilge to be 9.5" wide where this particular model would be installed. Keeping the bilge dry whenever possible, never intentionally placing gray water into the bilge, and leaving the primary bilge pump clean and clear for it's real purpose are all good reasons not to drain the shower pan into the bilge.

Size 8-1/4" L x 9-1/2" W x 5-1/2" H
Ports Inlets 1-1/2"
GPH 500 Single Port
​

http://www.jmsonline.net/shower-drain-1port-mercuryfree.htm?gclid=CKP4hLvLjb0CFYsWMgod21sA-g

 

[H30Gary]

Today I installed lag bolts to tie the new compression post to the old one.

 

[H30Gary]

Gary who built your base? When I started the post 60 minute compression post , I got some crazy private emails, but guy built it for me and installed in about an hour, he made mine quite thicker than yours but theory is the same and very stable! Good work

The base was built by a local fabricator (Matthew - Benchmark Custom Welding) here in San Diego. I measured the old beam, drew up a sketch, and he made it in a couple of days. He charged $200, which I consider to be pretty reasonable. Your aluminum block was probably cheaper. I didn't see your solution till I was already in process with mine. In any case, it looks stout and I'm glad its working for you.

 

[Alctel]

Hi - thanks to the rash of threads on this issue I checked out my hunter 36 today.

I'm not to keen with what I found - the first photo shows how it looked originally - and then I was able to scrape away a lot of crossion untill I hit solid metal, shown in the second pic.

How does this look? I am marginally worried at the amount of material I scraped off, but the remaining pole seems to be solid.

I've also attached a picture of the top of the compression post - is that split supposed to be there?

One good thing is that the mast is not sunk at all.

 

[H30Gary]

Alctel -
My guess is that you are OK. When steel turns to iron oxide (e.g., rust), it expands a lot. So although you might have scraped off a fair amount of rust, the actual amount of base metal consumed is probably not that much. Plus, the design of your metal base (a piece of pipe welded between two plates) is much better stress-wise than the I-beam design found in the H30. In fact, I considered considered making my replacement SST support that way.

The crack at the top appears to be only in the teak covering the actual compression post (hard to tell really, but that would be my guess anyway) so should not be anything to worry about. Even if the crack were to extend into the compression post IMHO at least, I don't think that would be a problem since it lies parallel with the load pat in the post. I'm guessing again that a prior owner may have cracked the teak in the process of removing it at one time. A few of my covering boards crack a little when I removed them.

The top area looks absolutely pristine - no compressing into the cabintop liner, etc. Do you think someone could have rebuilt this area in the not too distant past? It looks almost better than new! A rebuild could explain the crack in the teak facing board.

I'm curious also, on the H36, is the compression post directly under the mast or off set to one side a little?

Gary

 

[Alctel]

Alctel -
My guess is that you are OK. When steel turns to iron oxide (e.g., rust), it expands a lot. So although you might have scraped off a fair amount of rust, the actual amount of base metal consumed is probably not that much. Plus, the design of your metal base (a piece of pipe welded between two plates) is much better stress-wise than the I-beam design found in the H30. In fact, I considered considered making my replacement SST support that way.

The crack at the top appears to be only in the teak covering the actual compression post (hard to tell really, but that would be my guess anyway) so should not be anything to worry about. Even if the crack were to extend into the compression post IMHO at least, I don't think that would be a problem since it lies parallel with the load pat in the post. I'm guessing again that a prior owner may have cracked the teak in the process of removing it at one time. A few of my covering boards crack a little when I removed them.

The top area looks absolutely pristine - no compressing into the cabintop liner, etc. Do you think someone could have rebuilt this area in the not too distant past? It looks almost better than new! A rebuild could explain the crack in the teak facing board.

I'm curious also, on the H36, is the compression post directly under the mast or off set to one side a little?

Gary

That's reassuring, thanks. I'm going to scrape all the rust off and maybe coat the iron in something to make it more resistant - though not sure what yet.

I'm not sure about the history of the compression post - I wouldn't be surprised if it had been rebuilt at some point, there is 0 sag under the mast.

As to your question, I'll take a look next time I'm at the boat.