Posted by Jamie on 11/2/2009, 18:56:46

I was wondering if anyone knows if it is feasable to replace a compression post with a beam in the cabin. Has this been done before? I realize this would be re-distributing the downward forces to the gunwales instead of the keel but is the purpose of the compression post just to keep the cabin roof from sagging or is there more going on here than I understand? A bulkhead might be a solution as well, since I just want to open up the middle area of my small and cramped cabin. (I have an Evans 16 with a cuddy cabin that has been closed in with cabin doors added) Sorry about the long post and thanks in advance for any advice you can give me!

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Posted by Dave S on 11/2/2009, 23:02:09, in reply to "Removing compression post"

I once owned a neptune 16 which had no compression post. The overhead of the neptune cabin was very thick as though the manufacturer had installed a beam to carry the load. I now own a seaward 25 which uses an arched bulkhead to support the mast. The arched bulkhead idea is pretty good although it could have been better executed in the seaward.In a small boat like yours, a short beam flanked by two thin posts would likely be less clausterphobic than a bulkhead, provided they don't pass through the V berth. The flicka 20 has a load carrying beam in combination with an off center compression post. Another approach might be to modify your rigging with quick acting shroud tensioners to reduce compression while at anchor in conjuction with installing a compression post which is removable or purhaps hindged to fold out of the way. I also own a Montgomery 17 in which I have chosen to embrace the compression post. I have wrapped the post in oak which is attractive and provides many advantages. The new hollow oak post acts as a conduit for wiring between the battery and mast mounted tricolor light, a mounting surface for two swiveling reading lights which also provide directional lighting for the galley and quarter birth. Wrapping the post also provides a larger diameter and smoother surface to the post in the event that I accidentally bump my head against it. Furthermore I have mounted a small gimboled oil lamp, which acts as a cabin heater of sorts, on the post. Hope some of this helps.

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Posted by Dave Whitney on 11/3/2009, 4:52:10, in reply to "Removing compression post"

I read once where someone made his compression post removable - allowing it to be locked in place while sailing, and removed while camping. At anchor I suppose the cabin roof wouldn't be under that much strain? Sort of like having the best of both worlds.

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Posted by Mike Turner on 11/3/2009, 5:33:51, in reply to "Removing compression post"

The compression post doesn't just keep the cabin top from sagging, it also carries the compression load of the mast down to the keel. My boat (Rob Roy 23) uses an arched teak beam instead of a compression post, but the beam doesn't take the load over to the gunnels. Instead, it takes the load to two compression posts, which form a door through the bulkhead beteen the salon and forepeak, which in turn rest on a "floor" of wood that spans the cabin under the sole, and rests on the keel. So the compression force is still on the keel. The compression force can be substantial, even on a small boat, when the rigging is set up. I found this out when I tried to remove a screwed-down section of the cabin sole to remove my marine toilet for repair - couldn't figure out why I couldn't move the piece of sole after I'd removed the screws, until I realized that one of the compression posts was partly resting on it (the post was notched to accept the sole, and continued on down to the floor resting on the keel). Chainplates are the same way - when properly installed, they attach to bulkheads or other means of transferring the forces and loads of the rig, to the keel. Small boats may not have that much load - but it's probably more than we realize, including shock loads of improperly tuned rigs. Whatever method you adopt, also periodically check the compression post, beam, etc. to ensure its integrity. Any water intrusion in a wood post can lead to rot, and trouble. On my old Catalina 30, which used a wood compression post, the head's shower drained to the bilge, right past the base of the post. The water allowed rot over time; the rot allowed the post to sag; and the sag resulted in a dishing of the cabin top on the deck beneath the mast. This was such a common problem that Catalina had info on its website about the options to fix it, and even sold a replacement base for the post. Mike Turner Rob Roy 23 yawl "Fiddlestix" Mobile Bay, Alabama

Link: Fiddlestix for Sale - Reduced Price

Posted by Jamie on 11/3/2009, 16:30:24, in reply to "Re: Removing compression post"

Thanks Dave, Dave, and Mike. Food for thought. Perhaps the best advice is to learn to embrace the compression post. I had thought of hinging it also. I had wondered why some boats in my size range had posts and some didn't. I don't want to take any chances structurally - I understand building engineering but not boat engineering. I also know from past experience that something that seems ok on your boat in moderate winds fails very quickly in heavy winds. The Evans 16 is a nice sailing boat, and fast. It outsails my friends' Siren 17 by a large margin in any kind of weather. It originally came with a cuddy cabin and I wonder if that's why it has the compression post since there was no bulkhead to close in the cabin. It now has a bulkhead closing it in but without talking to the designer I don't know if that would make a difference. (The boat was built in the 70's in Ontario and has been out of production for a long time) Thanks again, and thanks to SCA my favourite magazine for having this forum. I read it all the time but haven't had much opportunity to post.

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Posted by Dave Laux on 11/4/2009, 3:23:24, in reply to "Re: Removing compression post"

Take a couple of pictures or make a dimensioned drawing and I will take a look at them if you wish. This is not rocket science. You just have to disribute the load to the hull some way. The post is not the only way. Dave

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Posted by Sean, 'Jo, and yes..Bosun! on 11/4/2009, 19:47:08, in reply to "Removing compression post"

It's been done, looks to be done very well indeed and the entire project chronicalled on Charlie Phillips webpage. I love it when folks put a great project done so well on here for us all to see! Awesome job! Here's the link: http://wwp19.home.comcast.net/~wwp19/arch.html

Link: P-19 compression post replacement with arch

Posted by Jamie on 11/7/2009, 21:19:24, in reply to "Re: Removing compression post"

Thanks Dave L. for the offer. Thank you Sean et al for the link to the P19 site. That is exactly what I had in mind but didn't know it until I saw it! I had a good look at things today and I think that is very do-able. I teach construction and machine shop at a high school so I have confidence in building an arch properly but I was unsure of the engineering side of it. In fact I will get our engineering teacher to assist with my final arch design. Once again thanks for the responses from everyone.

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Posted by Steve W (NY) on 11/9/2009, 13:12:18, in reply to "Re: Removing compression post"

I had seen that page and I just couldn't find it in my links.....what a resourse the internet is. Take Care, Steve

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