Compresion post repaired - Page 2 - SailNet Community

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Go Back   SailNet Community > Boat Builders Row > Islander
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  #11  
Old 11-06-2011
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Quite a project. I'm glad it worked. My approach was no less complicated and started with the observation that the 1979 mast base casting had small divots in the vertical flange on both sides which were apparently to provide a pathway for water to exit the casting. Unfortunately, there were no corresponding divots on the bottom of the factory mast itself. While the mast was off, it was a matter of 5 minutes with a chain saw file to open up divots in the bottom edge of the mast to match up with the holes in the base. As for the wiring, I ran everything down 6" of garden hose which fit quite nicely into the existing hole in the mast base and stuck up 6". There was another smaller hole which I simply threaded and plugged with a matching threaded PVC plug. I fastened the hose in with a good dollop of 3M 5200 caulk. The mast base itself was bedded with 3M 4200 after the usual prep (drilled out epoxy through-deck holes after drying the core, etc.) while it was removed. I filled the garden hose with expanding foam around the wires which could end up too permanent if I ever have to pull the mast again but we're sick of drips. So I figure that unless we forget to check the weep holes occasionally the water will never get 6" deep in the mast. So far, so good but nothing is forever. I figure my point of failure will eventually be the 5200 caulk seal between the hose and the base but if water can't pool up in the base I'll still stay "pretty dry". Our cabin top dimple was not too bad (< 1/8") so we decided to live with it. This can only mean that the entire cabin top deflected down which is probably a bad sign and explains the creaks and cracking sounds as we lifted the mast. As "Hellosailor" pointed out, it also speaks to the stiffness and quality of the deck and cabin top core in the Islander 28. The PO had sadly neglected to maintain his deck fittings so I have had ample occasion to examine the effects of leakage into the core and its durability is absolutely remarkable with nary a soft spot (yet) responding to tapping and discreet drilling.
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  #12  
Old 04-03-2012
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Re: Compression post repaired

Ok, I have some deformation at the top, cabin sole, and bulkhead self in the compression post area on my Islander 28. I came up with this thread when I searched my problem. Therefore, I am posting on this old thread to keep the subject matter together. No pictures of the issue were ever posted, and I have some, "pictures are worth a 1000 words".

On surveying the issue, I believe many Islander 28 owners will have experienced the problem, and looking for how the problem was corrected. I have a few ideas, but need some experienced advice.

First, I noticed under the cabin sole there are two cross supports under the compression post area, marked "A" and "B" in the third picture. These two cross supports ARE NOT the same height at original construction of the boat, which doesn't make since, because the 3/4 inch plywood floor would surely deform in this area with the pressure of the compression post. So, to fix this problem, I will have to add material to the lower one to meet the higher one. I plan to use epoxy glass reinforced, I have to make up about 5/16 or so. Doing this will make part of the head sole a different height, I will have to even out the floor by feathering the fiberglass material to meet the old floor.

Second, none of my wood is rotten, so removal of the 3/4 plywood cabin sole, the 3/4 plywood square under the wood 4x4, is going to be a tough job. I need to remove part of the sole and the 3/4 plywood piece under the wood 4x4 that forms the corner of the head in the bulkhead area. I plan to replace both pieces with GP03 Electric Grade fiberglass. I can buy it from McMaster Carr in many different sizes and thickness, and I can easily epoxy or resin it to the fiberglass floor and supports.

So, I'm going to loosen all of the rigging and jack up the cabin top at the metal compression post area, as mentioned earlier in this thread to perform the cabin sole repair.

I still have several issues with the current compression post design, the plywood counter is between the wood 4x4 and round metal flanged post. So, once again plywood is bearing the load, not good, and deforming at this location too. The deformation is actually recessing the counter top. So, I was planning to cut out the counter top the same diameter as the flange, remove it, and replace it with the fiberglass board or delrin, a high density plastic. If I cut a hole in the counter top, the two piece compression post would no longer have the counter bulkhead keeping the compression post plum to each other or the cabin top. My question here, would I need to attach the 4x4 wood portion of the compression post to the cabin sole to keep the post plumed to the cabin deck?

I was even thinking about removing the wood 4x4 and extending the metal post to the GPO3 fiberglass by making a matching metal post section to bolt to the current one and bolt it to the GPO3 fiberglass. I'm not sure if I should bolt it to the cabin sole if I go this route, the current set up is not fixed to the cabin sole.

I believe the total deflection at the cabin deck, picture one, is equal to the deflection of picture two plus the deformation of the counter top. You cant really see the actual deformation of the counter top in picture four because it is all around the metal flange, but it is around 3/16, it is NOT the deflection you can see of the counter top to the bulkhead wall, which you can see because of the different wood color.

So, do my ideas seem good or should I try something else?
What are your thoughts?
Attached Thumbnails
Compresion post repaired-compression-post-bulkhead.jpg   Compresion post repaired-compression-post-cabin-sole.jpg   Compresion post repaired-compression-post-floor.jpg   Compresion post repaired-p2220593.jpg  

Last edited by 510datsun; 04-03-2012 at 02:13 AM. Reason: change photo
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  #13  
Old 04-03-2012
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Re: Compresion post repaired

I'll have a shot at some answers but "experienced" is probably an overstatement of my qualifications. First, even if the fix gets nasty, stick with it because the boat is worth the effort. The Islander 28 is a sound and sweet-sailing boat. What year is your hull because your pictures show something a little different from what I see? For example, the 5/16" difference between the two cross-members doesn't exist on my hull. If I were to do things over again (besides using dielectic materials) I would have pulled the mast rather than jacking it up. We pulled the mast later anyway and I was impressed with how much easier and less nerve-wracking it was not having the jacking system in the way and the mast poised above my head when I repaired the mast base. In my opinion, the plywood-under -compression has got to disappear no matter what - it's just trouble waiting to happen. The all-steel post is a good way to go but it may obliterate the corner of the head bulkheads. The infamous 4"x4" post seems to be in the way so a lot of cabinet work may be needed to put things right. I wasn't worried about keeping everything plumb because the 4"x4" post seemed very firmly attached to the bulkheads, one of which is tabbed to the hull and I had also bolted it to the steel post. I think the entire assembly needs to flex and move a little under heavy conditions and I'm not so certain that everything rigid and firmly attached is the best idea. However, I must admit that the thought of my mast slipping off the compression post and shooting like an arrow through the bottom of the hull is a bit terrifying. My fix seems to be working even after we have been bounced around so I guess it's still better to be lucky than good. I'll try and keep my promise of pictures. Off-topic but how do you intend to deal with the missing vinyl headliner? Maybe on another thread?
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  #14  
Old 04-03-2012
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Re: Compresion post repaired

Datsun, at this point it is anyone's guess whether those two "beams" were ever supposed to be the same height. "I still have several issues with the current compression post design," But I have seen Bob Perry's original drawings for the boat, and it was designed to have the mast either supported by a simple vertical compression post, or keel-stepped.

Apparently someone at Islander "had a better idea" and used this zany scheme to open up the interior and give the boat a palatial cabin. One might seriously consider throwing out some scrap wood and metal, and installing a simple vertical post, and just telling folks to exhale and squeeze by if they want to go forward of it.
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Old 04-03-2012
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Re: Compresion post repaired

Amen to that! You shouldn't expect to be able to tango in the cabin of a 28' boat. Anyway, it's not that much of a squeeze and that's what I would do if I was starting over with the mast. The boat as built (and properly maintained) is not unseaworthy at all but it would be more seaworthy with this modification. Great design but there are few points where you have to wonder what they were thinking on the production boats.
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Old 04-04-2012
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Re: Compresion post repaired

Datsun,
Go to the 2nd page of the thread titled I-28 Keel Stub Construction, I posted some pictures there of my I28 during the mast step rebuild. I replaced everything below the timber post with solid fiberglass; I made my own ¾ inch fiberglass plate material to replace sole and to build up a new mast step support beam.
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Old 04-05-2012
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Re: Compresion post repaired

Datsun, I have come to the conclusion that these boats are more "plastic" than we think. Everything seems to be moving a bit and maybe that is a survival strategy! I'll try to attach some images of our repair but I noticed our boat is not identical to yours. We have a "sold in" 1979 version...
PC
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  #18  
Old 04-08-2012
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Re: Compresion post repaired

Ok, Thanks for you replies all!

I have a 1976, I-28, hull #23, I recently removed the tile floor with a drain in to the bilge, a rare shower/head option. Ya, a shower in the head, sure would like to witness that task. I'm lucky to sit on the throne and read a paperback, forget the newspaper.

I have decide to replace the cabin sole with the GPO3 fiberglass, replace the piece between the cabin sole and 4x4 with GPO3 fiberglass, cut a hole in the counter top the size of the flange, and replace the counter portion between the 4x4 and metal post with the GPO3 fiberglass too. I can epoxy the fiberglass to the 4x4 at both ends.

I decided to go that route because it would all be doable by jacking up the mast and kind of a retro-fit, modifying what is already there. I will take pictures of my fix and post them up after I finish the project. It may be a while before I get it done, but I promise to post it up to help I-28 owners having to deal with this issue.

I really like my I-28, and get compliments on it every time I'm out on the water, got one just today!

As for the headliner, I was going to post up a thread on my idea for that fix. So, look for it soon.
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Old 04-08-2012
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Re: Compresion post repaired

In case you are wondering about what GPO3 is, I used it as a spacer when I did my thru-hulls. I used kitty hair, polyester resin with glass fiber, to bond the spacer to my hull. I tapped the spacer and bolted a thru-hull spacer to it. Here is a picture of the GPO3 fiberglass, the red material.

You can see the blue tile floor, too.
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Old 04-08-2012
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Re: Compresion post repaired

510, a lot of the plywood on the I28 is "Bruneel" plywood, which is damned strong stuff. I don't recall ever looking at what that little countertop section is made from, but if that's also Bruneel, it is already as strong as fiberglass. Unless you're planning to refinish the whole strip, it might not pay to bother changing just that bit under the post.

A tile floor...good lord, there's room for a whole new HGTV show, on renovating heads! (VBG)
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