Mast Compression Fix on Cal 28

Discussion in 'Fiberglass and Composite Boat Building' started by Thorpydo, Sep 8, 2012.

  1. Thorpydo
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    Thorpydo Junior Member

    I have a 1964 Cal 28, hull 41.

    The deck has deflected down somewhat as evidenced by a crack in a timber that rides along the upper edge of the main bulkhead, a gap that has opened up in the door, and a crack in the fiberglass liner.

    The compression post and mast step look to be in good, solid condition. It is clear to me that the deck stepped mast has pushed down hard enough to deflect the inner liner.

    I believe the boat has been like this for quite a while and I have been out sailing almost every weekend, without a problem. Though, I do not know if the deck is deflecting while I am sailing, hard on the wind. It is possible that the liner has settled in (read cracked/deformed) so that it is now better supported by the hull underneath and there is no deflection while sailing. It is also possible that it is deflecting.

    In either case, I would like to sail blue water with this boat and need a good solution. It is odd to me that there is no beam under the liner. We hear about the 'dreaded steel beam'. This boat doesn't have one, but now I kinda wish it did.... I think I need to install some semblance of a beam to carry the load to the hull, or maybe the keel. Access is limited to the seat just adjacent to the compression post and from the galley. I do not want to cut the inner fiberglass liner to install a beam because in this boat, the inner fiberglass liner is the only thing supporting the compression post.

    Do you guys have any suggestions?
     

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  2. alan white
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    alan white Senior Member

    Sounds like whatever blocking sat originally between the mast and the compression post has rotted and compressed. If so, the deck would have deformed a bit.
    It could have happened very slowly over time and you took up on the slack with small adjustments of the turnbuckles as you would anyway to make up for stretch.
    A beam isn't needed if the mast is directly supported. Just some very solid blocking in the space between the inner liner and the deck. That seems to be what's in need of replacement and you should also check the whole area of the tabernacle for wetness in the core.
     
  3. Thorpydo
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    Thorpydo Junior Member

    I don't see how you have come to your conclusion.

    To me, it looks like the inner liner has cracked and deformed, higher stresses were then applied to the cross beam over the bulkhead and so it cracked.

    I have found no indication of rotting, anywhere. I have found cracking in the inner liner that would allow it to deflect down, and slightly forwards. That forward movement of the inner liner allowed the step that the compression post sits on to move forward, and come slightly out of plumb. I am pretty confident in this assessment, due to the cracking in the inner liner and the compression post being slightly out of alignment.

    Assuming this is the case, how would you go about bringing support back to the structure?
     

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  4. PAR
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    PAR Yacht Designer/Builder

    I'm pretty familiar with the Cal 28 and you're correct the liner has deformed, but the bulkhead and compression post to port of the saloon/head passageway also bare load. If memory serves, the bulkhead has a beam built into the top of it and this is a common place to see damage when the rig has crushed the areas above it.

    I also remember model run changes to this arrangement to address the problem. Some have a bit of steel, others an aluminum tube, all to help support and transfer loads to the hull shell. The post sits on a molded portion of the liner and inside this is a wooden beam, often with a bracket bonded to the liner laminate. Above the liner, bonded to the under side of the deck also can be found more material, plywood, aluminum or steel reinforcement, again to support the loads. The age of yours suggests it may not have the model run changes to address these issues. Unfortunately, you're not going to like the steps you'll need to take to reinforce the area.

    As you might imagine, the whole lot of the under deck supports, compression posts, bulkhead, liner and under liner support have both shifted and compressed (you've seen this). You can remove much of the "garnish", such as the post, the 1 by beam at the top of the bulkhead, etc., but the real problem lies between the deck and liner and hull shell and liner.

    I've seen some success with removing a section of deck, at the mast step and R&R the reinforcement piece this way. The bulkhead and compression post re-alinement/repairs are straight forward, but you'll probably have to cut open the locker and get at the bottom compression post support. It's probably broken it's tabbing and/or rotted away. None of this is particularly unusual for a half a century old yacht. In fact, you're lucky they built this thing on the heavy side.

    It is possible to pull down the overhead, make repairs and reinstall or renew the overhead. I've also seen some who've removed the post and replaced it with a traditional compression post (stainless tubing), with a bracket on top to receive the mast step through bolts. The original compression post was "backed out" and used as a decorative pilaster over the steel post, which hides it. The termination below the liner has been addressed a number of ways, but the best I've seen was again a flat plate flange, weld to it's bottom (like the deck plate) and lagged to a hunk of hardwood, that was bonded to both the hull shell and liner. This eliminated the 2x4 beam/post that was bonded to the liner and directly transfers loads to the hulls shell, which is what you want. The problem with the original arrangement was too many pieces to keep in column, which they knew, so they did bond the crap out of things to help keep it solid.

    Hows your steering? I have a lot more comments and model run upgrades to steering issues over the years. Many folks have lengthened the rudder 6" - 9" to get better response, especially at lower speeds and under power, with a small engine.
     
  5. Thorpydo
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    Thorpydo Junior Member

    I couldn't have asked for a better response. This is exactly what I was looking for. I will have to read it over a couple more times before I can respond. Thanks a bunch!
     
  6. Thorpydo
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    Thorpydo Junior Member

    Your memory serves you correctly. I do see damage to this beam. It has a significant bend in it and has a crack on its bottom edge, on center line of the boat

    I have not seen any steel or aluminum in the structure. I have checked out the wooden beam laminated into the inner line with one of those 'cameras on a stick', viewing from starboard side. It doesn't look to have rotted. Viewing from the port seat locker, the glass holding it in place is still in tact. I have not found a bracket bonded to the inner liner. Above the compression post, I see some fiberglass tape used to cover up the area. Don't know the condition of what is behind it. I think you are right, I don't have most of the running changes.

    Problem between inner liner and hull shell is clear to me. Between deck and liner (I assume this means the ceiling) not as much. Do you expect rot in the wood within the mast step? Or the plywood simply collapsing? I haven't seen any indication of problems in this area and that is why I am suspect.

    What is the purpose of removing a section of deck? I don't understand that unless you are talking about rebuilding the area directly under the mast. As mentioned earlier, compression post support looks to be in decent shape.

    Not sure I understand pulling down the overhead either? Again, unless you are only talking about the area directly under the mast.

    I agree completely, that the original arrangement has too many pieces to keep in column and that a stainless tube from cabintop to a hunk of hardwood provides a much better load path.

    I really like this solution, except for one detail. We are dealing with compressive forces imposed from the mast, but also tensile forces imposed from the windward shroud. In the original arrangement, tensile forces are transferred from the chainplate to bulkhead to inner liner which balance with the compressive forces applied to the inner liner. The hull shell could be removed entirely and a solid load path remains. I would like to keep that redundancy in the load path by bonding the hunk of hardwood to the main bulkhead. This would also mean replacing the main bulkhead and I would need to look into the feasibility of it. I don't know if half a main bulkhead would fit down the companionway hatch, for instance. It's also a lot of work, but I'd like to do this fix once and be 100% confident in it. This thinking mimics the steel beam in later cals with tabs that bolt into the bulkhead.

    I suppose the alternative would be a hunk of hardwood/stainless compression post while keeping the main bulkhead in place. I will have to cut out parts of the inner liner to install the hunk of hardwood and would have to be careful to keep most of the inner liner in tact. The inner liner forms part of the wall aft of the head, for instance.

    Check out the solid model to see if we are on the same page.

    I'm also wondering about strengthening the area directly under the mast, between cabintop and maststep. I believe I have plywood in there now, and don't believe it is rotting (I slightly enlarged the lag bolt holes in it about a year ago). But again, if i'm going through all of the other effort, I might as well make it all as bulletproof as I can. My first thought was to drill two large diameter holes with a holesaw in the maststep. Connect them so that I have a slot hollowed out in the mastep. G10 plate, laminated together to build up thickness, slightly smaller than the slot. Install with thickened epoxy.

    Any suggestions or solutions there? What kind of forces are we dealing with in the compression post? Will G10 be too low modulus? I will also need guidance sizing the compression post.

    Steering. Undersail it doesn't seem to be an issue. I have to be careful in marinas or mooring fields, but then I'm under power and if I need a tight turn, I can tilt the outboard (in well) which seams to work pretty well. I haven't sailed any other boats this size though, except a J24 (and it turned on a dime) so I don't have a lot to compare.

    I'd love to hear what you have to say about model run upgrades or anything else related.

    One steering related issue that I would like to address would be the rudder post to tiller interaction. It is too sloppy and needs to be more rigid. The hardware at the bottom of my tiller is simply two bronze bars bolted to tiller and axle. I have seen other cal 28 rudder posts with a cast bronze 'U' shaped part that fits around the post and provides a much more rigid connection.
     

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  7. Thorpydo
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    Thorpydo Junior Member

    Or perhaps a G10 beam for its better longevity.
     

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  8. PAR
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    PAR Yacht Designer/Builder

    Yes,, between the underside of the deck and the headliner, there's a gap and it's filled with plywood (originally), which was bonded to the deck. G-10 would be a fine substitute for this piece, which has likely crushed or rotted. You can look at a piece of wood, but not seen signs of rot. You have to probe it. The wood's density will be apparent pretty quickly when you find rot. I'm not sure of the size of the reinforcement under the mast step, but I'll suspect it's pretty big.

    Compression loads on your boat are carried to the hull shell by way of the liner contact points. These loads eventually have to be distributed to the hull shell and the idea was lots of contact points over a large area, which is technically valid. Lateral loads from the chain plates do the same thing, though the bulkhead serves a bigger role on this point.

    The drawing you have looks fine, but I'm not sure about the lower attachment. I would bypass the liner all together and bond directly to the hull shell. I'd do this by cutting out that locker, for access that's easily hidden after the repair. This will permit a proper mast step that can be bonded to the hull shell over a wide patch. Several layers of biax, some plywood or G-10 bonded and tabbed in and you're good to go. For extra measure, you could also bond the compression tube, maybe a welded flange so it lands cleanly on the liner and bulkhead. I'd be inclined to make it a solid, non-removable assembly, all covered with trim, so know one knows you where in there.

    By removing the headliner, I mean there's a plywood or veneer skin attached to the liner. This can be removed, which will hide cuts and repairs made to gain access to the under side of the deck's mast step. Once the repair is made, you'd patch the cut out portion of the liner back in, and re-bond a new headliner veneer back in place. This will save the exterior deck cutting and patching, which will be harder to make look nice.

    Replacing the bulkhead is a pain in the butt. Nope, it will not fit down the companionway hatch. You'll have to cut it while below, though a laminate could work. You could build it in 4 pieces, making a 2 layer sandwich and assembly it in place. This is the way I'd go. If doing this, do NOT make any of the seams, for the pieces land anywhere near the passage way opening top corners. This will just promote stress risers and offer a path for a crack to propagate. I'd also consider a heftier beam along the top edge too, which should be a nice, dense hardwood.

    As far as model run upgrades, there were many covering several issues, some included the mast step. Details on these are hard to come by, as often they were just instructions to the assembly crew. Again, I've seen aluminum steel and a few different approaches, all that seem to have been factory applied.

    Yes, the tiller/shaft connection was changed to include a cast bronze "pinch fork", which was more reliable. It wouldn't be difficult to reinforce what you have or make up a piece that is heftier. I dislike forks and prefer something that mechanically locks, like a socket head over a bolt type of deal. These are reasonably easy to cast or have machined up.
     
  9. philSweet
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    philSweet Senior Member

    I owned a '63 until quite recently. It was okay but the boat that I replaced it with had this same problem. Like PAR said, the good news is it's built like the proverbial brick outhouse. The hull is all layered woven roving and is quite rubbery (I could oilcan my hull with the palm of my hand). I think you need to pull the boat out of the water to do this fix. The liner is seriously warped and you aren't just going to be able to push it back with the boat floating. Haul it out. Check the keel joint for a "smile" at the front. Pull the mast and unrig it. Maybe run some ribbands supported by boatstands at the bulkheads. Explore any keels issues first. Hopefully this isn't a problem, but the keel attachment has to be made right first if it is.

    Then you can set about getting the liner back where it belongs. I had to jack the liner on my Catalina over two inches and replace the mast support underneath. Figure on a week of 20 hour days in a yard. Drape and mask the entire interior with plastic and drop cloths. It's going to get messy.

    And one little trick. If you want to cruise her, you'll want some eyestraps in the liner to tie/bungy stuff to. At least you will use them if you have them. When straightening the liner, install 1x2 cleats top and bottom pretty much wherever you can to keep it flat. Screw right through the liner. You can mount little eyestraps where the holes are when you are done so plan accordingly. I ended up adding a thick layer of glass to the undeside of my liner. Boy was that fun. Does anyone make disposible gloves that come up to your shoulder?
     
  10. Thorpydo
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    Thorpydo Junior Member

    PAR,
    See attached photo of maststep. We're only talking about rebuilding the raised section of the maststep and below it, not any part of the 'flattop'. Is that correct?

    I'm not sure what you mean by this. In the picture shown, I was trying to illustrate a hardwood or G10 beam that sits across the bottom of the hull shell, a compression post is bolted to the beam. The bulkhead is laminated to the beam. A liner is not involved.

    You are suggesting biax or plywood or G10 bonded flat against the hull under where the hardwood or G10 beam would sit, to distribute the load in the hull shell in that area. Is that correct? Tab in beam to hull.
    I thought the compression tube would land on the beam and that the liner wasn't involved?

    Do you see replacing the bulkhead as prudent thing to do? Necessary?
    I was thinking that I would be cutting out the liner below the bulkhead and that then it would be necessary to replace. But now I see options of installing a beam while leaving the liner below the bulkhead in tact. Maybe I should leave it in place. Again, no sign of rot, and this one I have drilled holes into.

    Can you show a picture of the 'socket head over bolt' type solution?
    I have an NC mill but haven't worked with bronze. I'd assume the workflow would be to machine a plug that would then be cast?



    philSweet,
    What part of the liner are you refering to? The inner liner on the floor or ceiling? And why does that necesitate putting the boat on the hard? I plan on removing the stick and rigging, but really see no need to pull the boat out of the water.

    Maybe this is a reason to pull the boat, but why can't I inspect that area with the boat in the water? I SCUBA dive and will take a look next time I scrub the bottom.

    Any tips on inspection? Again, can I do it underwater and from inside the boat? I have occasional felt the keel rock while the boat sits on her mooring. It is more pronouned because the table is supported by the keel so it rocks as well. I have never felt anything of the sort while sailing. When moving it feels solid.
     

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  11. philSweet
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    philSweet Senior Member

    I meant the floor liner. My only tip on keel inspection is do it while the boat is hanging in the slings after being pressure washed and before being set on blocks. Preferably with the rig still up.

    This aint good. Haul it and deal with it before you go offshore. If others have screwed with it you may find the joint stuffed with Bondo. Or it may have all fallen out and that is why she's going thunk-thunk.

    I remember seeing an amazingly well documented flattop rebuild on the web, but can't find it anymore. You should drop in on the Cal owners site and ask about it.
     
  12. bntii
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    bntii Senior Member

    Years back I gave a cursory in the bilges of my Cal 27 just before we set out on a voyage.
    Big surprise- every nut on the keel bolts were missing or nearly so as they had dissolved from corrosion.
    No bilge pumps or any other wire in the bilge water so I can only think they were a less noble alloy and time caught up to them..

    Take a peek at the bolts and see if anything is amiss in the bilges and yes haul the boat to look into it.
     
  13. PAR
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    PAR Yacht Designer/Builder

    Another thing to look for when in the "bilge" is the contact points of the liner itself. These commonly break free and the liner moving was likely what you felt, not the keel moving.
     
  14. Thorpydo
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    Thorpydo Junior Member

    The ballast is encapsulated within the hull shell and there are no keel bolts.

    I have to haul to replace a couple thru hulls and that is right around the corner. I will inspect then.

    Thanks guys!
     

  15. philSweet
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    philSweet Senior Member

    I must be getting senile. Why didn't I remember that?
     
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