Adam Brown has an excellent post about replacing the compression post here. (Oct 2016)

I am considering the purchase of an Allied Seawind II and have had the prospect boat surveyed. The survey pointed up a few problems. The most serious problem is some rot in the compression post for the main mast and the cross member which it supports across the cabin top. Have you had or heard of this problem? Do you know how much it will cost to replace the rotted pieces?

Date: Thu Nov 30, 2000 12:22 pm
The compression post is a problem with most Seawind IIs, but it is not an unsolvable one. In brief, most cut a hole either in the most flat area of the cabin sole in the forward cabin, or alternatively below the shower grate in the head, and install a 6-8 inch round or similar access panel. Then they accomplish two things inside. 1) After clearing out the "rot", they jack up the mast (some even use a very small hydraulic jack) in whatever way, and once in proper position, they block it, and then fiberglass the whole thing in solidly. (there are many variations of this, however) (2) Clearing a better passage for trapped water from these upper reaches of the bilge back toward the stern where it can drain eventually into the main deep bilge beneath the cockpit will allow moisture to dissipate from that area, which is what caused the problem in the first place. This is a "design flaw" like so many boats have, but should not alone, I think, deter you from purchasing one of the finest yachts available in its size and class and functionality otherwise. Regarding the cross beam atop the mast (cabin top), I don't have any answers for that, since I've not heard of that being a problem.

Date: Thu Nov 30, 2000 1:20 pm

Crossbeam: My mast post appears in fact to be a mere door jamb, achoring two doors and the forward head bulkhead. I feel most of the load is taken by the bow-shaped laminated beam, above the mast post and under the cabin top. This beam is very clean and sound in appearance, and I check regularly the doors fittings (wooden slats nailed or glued along the mast post) that might open up at the top as a token of that beam yielding. One (head door side) did bend open slightly after a stranding in a freak hurricane storm that destroyed or stranded 17 boats at American Yacht Club. That disappeared after taking off the mast for upgrading work the following winter and never reappeared, so I suspect the stranding efforts, and/or mast stays that were ill-tuned, a bit too tight, at the time.

Date: Fri Mar 23, 2001 5:35 pm

I finally bit the bullet and put a hole in the shower pan. The out of plumb door turned out to be a good indicator. The compression post was a sponge.

My question for the day is: What is the best way to cut the compression post and keep the cut square? I'm planning to cut a larger hole in the shower pan and make parts of the sole removable just fore and aft of the post. My first thought is to put a long blade into the Sawzall and go with that. Any suggestions with regard to cutting and what a good size for the sole access would be?

Date: Fri Mar 23, 2001 8:08 pm

I hope my post is still OK, but I intend anyway to open the sole as I mentioned in an earlier ms, reacting to the membe who had put in a Bomar hatch. The 6" tight porthole I opened 2 years ago close to the post has not made it easy enough to (a) empty the space (with a plastic bilge pump, then a sponge), (b) clean up the drain holes to the aft bilge through the water tank, (c) inspect the post base.

So I intend in the next month (boat was lauched yesterday) to open thoroughly the sole, by drilling four holes and bevel sawing (so that the cover may not fall through) a trapeze, leaving only an inch or two around for structural value. I shall put two hinges on the head side so that it can be easy to lift and close, with a stainless bar added on the opposite side that will lean on the remaining sole edge, and be secured by one or two lugs, thus keeping the storage space below safe in case of knock down or "turtling". Much cheaper than the touted Bomar and just as functional. Note that inside showering should be exceptional, as I run a flexigle shower from the exiting shower tap, to reach the deck through the fore hatch. Saved a lot of seawater drips in the cabin after swimming and snorkeling.

Date: Sat Mar 24, 2001 9:05 am

My compression post seems OK, so I can't directly address your problem. However, since now I have a 6 inch round access port in the head sole I need more access for stowage and to clean up the limber holes (if any! Water has been accumulating there).

My plan is to cut a big square or rhombus shape in the head sole, and then to embed vertical bolts in the lip. I'll make a lexan cover that goes over the open space. A rubber gasket will seal the cover, and screw-on knobs (available from Small Parts inc) will force the cover down against the gasket. This way the hole size can be large for easy access down there, and the shower will still drain properly.

I elected to not do the Bomar hatch as the lips on it will collect shower water, and I have to use their sizes, so can't max the hole size.

Date: Sat Mar 24, 2001 9:29 pm

I thought I remembered this from the chronicles of GiGi. I wanted to post it so that it's in the archives. I'll also add the whole process to the knowledge base when I've finished my project.

I may point out that the mast compression post had rotted in GiGi much the same as most of the SW IIs. My repair was quite unique and much less painful than some that I have read about. After cutting a 10" Beckson access panel into the head shower basin and another 8" X 11" hatch in the sole outside the head we had enough room for two hands to work in the tight area. Next we placed two 2x4 braces under the step area and braced them outboard at the vanity and the closet. We drove wedges in at the lower protective pads to raise and support the loosened rig. A very sharp and flexible, Japanese made backsaw was used to cut off the butt end flush under the sole. We widened the sole on either side of the post by two and a half inches to accommodate two matching cheeks made from green oak. A slight, curved cut was made in the forward head door to fit it around the rounded top of the cheek that extended above the door transom two inches. An 1/8" plywood form was fitted in place and we packed concrete over two centerline PVC drain tubes and four pieces of crisscrossed rebar reinforcement. When the 'crete was set a three inch thick block of Angeline was placed on top of the platform and a quarter inch plate of galvanized steel plate mounted on top. The two green oak cheeks were screwed to the port and starboard sides of the compression post above the sole with the screws angled slightly downward to press the cheeks against the new base pyramid. There had been some deflection of the oak main support beam under the step so we decided to fabricate a companion plate to be slipped between the coachroof liner and the beam with holes that matched those in the deck step. This was used to deflect some of the rig weight and spread the load over a larger surface. When the braces were removed the head and cabin doors both indicated proper clearance. The rig was retuned and we waited another week before sailing her. She shows no sign of any dimensional change since.

Date: Sat Mar 31, 2001 3:10 pm
With all this talk about the compression post, I started checking out mine. I just acquired SWII hull 113K and have noticed a percieved design flaw. My post is only about 1.75" wide and the mast step is offset about 7/8" to port (not centered exactly atop the post). Is this consistent with any of your arrangements?

Date: Sat Mar 31, 2001 4:57 pm

Do you have a true, self standing compression post? or, like on my hull 80K, you have a square post, not thick nor columnar, that serves as a triple jamb to 3 doors (2 off the head, starboard athwartship, and along the centerline; one between the two cabins, athwartship portside), while the mast compression and weight stresses are mostly borne by a thick cross beam? If so, a small offset may not be critical.

Date: Mon Apr 2, 2001 8:59 am

Our compression post is approx. 4" square and sits directly on the keel centerline embedded in a epoxy like substance. We treat the post annually with a wood preservative, a green color fluid and after 14 years of service its still hard as a rock.

Date: Fri Jun 22, 2001 3:23 pm

I see that we have someone else tackling the compression post. I'll write up the details later but this is a quick and dirty about how I'm doing it. I tore out the shower pan, door threshold and part of the cabin sole. Cut the compression post with a long sawzall blade leaving about two inches below the sole. Cut a piece of white oak to fit into the two inch well in the bilge. Cut the old piece on a radial arm saw a couple inches below the top. Measure the space from the bilge to the old piece when held in place. Cut the new piece on the radial arm saw, w/o changing anything, to fit (longer is better in my opinion). Put the new piece in the well. Force in the old piece. Shrouds are loose. Cut 3/4" marine ply for sides, front and rear. mark the placement. Remove everything and drill through for 3/8" stainless bolts. So far two in new piece and two in old piece. Reinstall with bolts. Use wood screws to affix front and rear pieces.

Date: Tue Oct 9, 2001 6:08 am

We cut a hole into the head sole so that we could access the compression post, found that it was solid, but every year we coat the lower portion with a wood preservative that prevents root. This has kept the post like the solid oak its supposed to be. We also keep the opening in the sole open for air circulation when the vessel is not in use. This has worked very well for the past 14 years.

Date: Tue Oct 9, 2001 2:31 pm

My curiosity regarding the compression post leads me to some questions.

When I cut off the butt end of the compression post I discovered a plywood, or the remnants of, pad that appeared to have been partially glassed into the hull. It was about an inch larger than the post butt. When you treat the butt end as you have mentioned, are you able to see a similar pad?

My next question regards keeping the forward bilge area dry. In the early years I chased deck, chainplate, hull-deck joint and various other places that are notorious weak points and repaired them. The collection of water in the fwd. bilge combined with an inherited, oily slime has never been capable of draining through the weep tube even after many attempts to keep it clear. Have you found a solution for this apparently inherent pool of water? I have read of several owners who stow wine in there. I doubt I was ever able to store anything but my bilge water collection.

Date: Tue Oct 9, 2001 7:16 pm

Regards the compression post, ours sits on a fiberglass mount that sounds like a piece of plywood glassed in before the oak post was set into position. It is about 3/4" thick and about 5 & 5 " estimated, the oak post sits atop it.

As to the drain, I used a Jet engine cleaner/degreaser purchased at a local chemical company and sprayed into the area below the sole. Then I used a green plastic wire purchased at Radio Shack which had the necessary stiffness and pushed it down the 1/2" hole until it came out in the deep bilge area under the engine. The cleaner degreaser then worked its way through as I moved the wire back and forth many times. This was then flushed with a mixture of soap and water, and dryed. Today its clean as a hospital, and we do use the area for 22 litres of wine which is where and what we carry in that space. As we use up the wine, we store the empty bottles back in the space, we don't carry the wine in their original container, but place it in used coke plastic bottles which are bulletproof in any weather. Never had one break yet, came close once.

 As to water collecting there, possible it could come from the hull to deck joint. We did have water collect there until we examined the aluminum rail, we found that the large screws that run horizontally through the rail were much to long and penetrated the hull, destroying the extremely well designed joint. We removed the rail, replaced some wet wood, some 1/4" SS bolts, and ground down the screws to ensure they would not penetrate the hulls integrity. Then applied epoxy compound inside to plug up the holes made by the screws when the rail was first installed.

Since then all water from heavy seas and rain have stopped running into that area. We now have to clean out the dust that collects there. It used to be I had to run the bilge pump for a minute or more after a rain, and it all was coming from the screws that penetrated the hull, ran down into the bilges, both forward and aft.

Date: Thu Oct 11, 2001 10:06 pm

I have seen several types of compression post "solutions".

Paul can tell you more accurately of his on SeaQuill

My Flicka has a poured epoxy solution . The area had glass epoxy poured in to fill the hole. It is now encased in epoxy and the few inches above the height of the epoxy block is also coated in epoxy. No water can get into the lower wood area. This will work only in the care where the post is ok to start with. It no longer is a low area so water can not pool there. The draining of the bilge area is another issue.

Summerwind 004k in Miami has a replacement block under a new stainless tube. The tube is covered with nice wood work so it appeared original.I am not sure of the size of the SS post but it shows no sign of sag on the deck.