Wooden Mast Repair

Discussion in 'Wooden Boat Building and Restoration' started by MastSplit, Nov 13, 2007.

  1. MastSplit
    Joined: Oct 2007
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    Location: Ottawa, Canada

    MastSplit Junior Member

    I would be interested in hearing from anyone experienced in the repair of thin-walled wooden dinghy masts.
    I have a 1949 International 14 with an original 26 1/2 foot Sitka Spruce hollow mast. The mast is laminated in four vertical sections (along the length) and I recently experienced a 26" split at the lower end. I successfully repaired that damage but I'm afraid that the old glue on the rest of the mast will give way and I'll lose the mast catastrophically. One lamination on the port side is already separating slightly and I'm worried that it will be the single stress raiser that will introduce complete failure whilst sailing. This mast is about 2" in diameter at the narrowest point which is about 48" above the base, and yet it's hollow!
    My plan would be to split the mast, clean up the mating surfaces and reglue it, the overall idea being to maintain its historical appearance and integrity so that I can sail the boat in light winds.
    This mast is intact othewise.
    If anyone has any constructive suggestions, I'd like to hear from you.
     
  2. Bergalia
    Joined: Aug 2005
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    Bergalia Senior Member

    Yes, it's the only way to go. Work on a flat surface (garage/shed floor). Try and seperate the sections by running a blunt blade (an ordinary table-knife should do) down the seams - careful not to splinter the faces. Examine the hollow 'core' for rot. Add a coating of timber preservative anyway (but avoid slopping onto faces to be glued.) Use a scraper (single-edged razor blade or similar) to throughly clean old glue residue. remove all hints of dust and flakes. Then re-glue using suitable marine glue. Use broad bandage to hold sections in place until set. (Several sets of hands needed). Remove bandage and sand away any surplus glue - revarnish and re-attach fittings.
    Well worth the effort. And good luck.:)
     
  3. MastSplit
    Joined: Oct 2007
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    MastSplit Junior Member

    Thanks Bergalia for your common sense reply. You mentioned marine glue for the re-glueing process and having read numerous other replies to other mast repair threads and observed that a lot of the recommendations for re-assembly is with the use of epoxy, I was wondering if this would be a better alternative. Could you please comment?
    Also, what are broad bandages?
     
  4. Bergalia
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    Bergalia Senior Member

    Hi again MS. Hard to be 'exact' on the use of the 'right' epoxy. I'd certainly use it as most brands allow a small amount of flexibility which will be essential in a working timber mast. I hesitate to name names - not being sure of those available in your part of the world. A word with your local carpernter/wood worker/boat builder should give you an idea. Explain that you want it waterproof, strong, and flexible under strain. But no doubt other members will weigh-in with suggestions.
    As to the 'broad bandage' - I 'cut' my own from an old bedsheet. (My wife is still looking for it). Linen is good as it is strong and has a certain amount of 'stretch' when pulled...and tends to shrink when in place, holding the glued timber tight. I found 15cm (6 inches) easy to work with, and could be applied with a slight overlap of the edges so that the whole joint/s are held fast, in one continuous, consistent grip (difficult to achieve with clamps).
     
  5. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    TiteBond III will be fine for your mast and save the expense and mess of epoxy. Used bicycle inner tubes make wonderful spar clamps. Just wrap them around, tie or clamp the ends and they apply as much or as little pressure as you desire. TiteBond III needs tight, well fitting joints.
     
  6. Bergalia
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    Bergalia Senior Member

    Dammit PAR...after all these years...why didn't I think of that.

    MS - just you listen to your Uncle PAR...He's right up to date with modern technology...(like bicycle inner tubes...:D) But seriously his advice never, never, fails to be top notch.
     
  7. alan white
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    alan white Senior Member

    Just a suggestion---- no matter what glue you might use, the wood itself hasn't much tensile strength. My suggestion is to glass the mast with very light glass (2 oz?)---- all that's needed is that it be tensily superior to the wood itself.
    The glass/epoxy layer would add almost nothing to the mast's weight and would be invisible too. No glue joints should open up afterwards. The real advantage of doing it this way is that once the mast is cut apart, it would take a lot of skill to put it back together correctly. By sheathing it, the labor is not only reduced by a lot, but the result is actually much stronger than if it is only glued.

    Alan
     
  8. Bergalia
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    Bergalia Senior Member

    Good point Alan - however PAR and I were working to MS's original plan to: ".. split the mast, clean up the mating surfaces and reglue it, the overall idea being to maintain its historical appearance and integrity so that I can sail the boat in light winds."

    It's the word 'integrity' which led us to offer our original advice. (Hope I'm not taking too much for granted PAR by answering on your behalf).

    But that's not to say, Alan, that MS should ignore your suggestion.
     
  9. nordvindcrew
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    nordvindcrew Senior Member

    mast repair

    an idea for dis-assembling the mast: I've found that warm vinegar actually will soften many glues. I've used it to disassemble furniture and kitchen cabinets. May work on the mast. Just brush it on and let it soak in for a while then try the dull kitchen table knife. Might avoid splitting the individual pieces of the mast.
     
  10. alan white
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    alan white Senior Member

    The idea is there to noodle on. Obviously the boat is built like a violin.

    A.
     
  11. PAR
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    PAR Yacht Designer/Builder

    I dislike the use of 'glassing the mast, unless using exceptional thin staves and biax (or other high elongation fabrics) cloth to decrease weight and increase stiffness. Bendy masts are a good thing and if stayed properly will remain under compression, which wood, especially Sitka spruce is especially well suited for. I've seen 'glassed masts sheer their sheathings, usually taking a thin (epoxy penetrated) layer of stave with it. Unless high elongation fabrics are used, it's a waste of effort in my opinion.

    Use a dull butter knife or putty knife to separate the staves, which will likely be lapped into each other. It's easy to split off a piece on the corner of these laps, so use care. Soaking in water, vinegar and paint stripper can soften things up as can heat. Much depends on the adhesive, which should be determined. Sand along one of the seams until bare, then coat with mineral spirits. If the glue line looks purplish (what I'd expect to see on that age spar) it's glued with resorcinol, which is a fine glue, but age will beat it up. After nearly 60 years, how can anyone ***** too hard, resorcinol is good stuff. If the glue line is tan to brown it could be aliphatic resin (also good stuff, but not water proof). It isn't likely plastic resin, but who knows.

    Also note the aft facing stave will probably be of thicker section then the rest (this is normal) so be aware of this as you work her apart.

    Work neat and clean, you'll do fine.
     

  12. alan white
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    alan white Senior Member

    The job must be well matched to the ability of the carpenter. That is why I mentioned another method. Not that it's the better way. Nor did I say that just any cloth would do. While I'm hearing (I think) that there is but one way to skin this cat, I can see how disassembly of the staves has inherent risks far beyond simply sheathing the mast. A lot of skill is required.
    That's all. I don't know about the experience of the technician, or that of anyone reading this who's assuming it's a snap. On average, the greater risk might well be the surgical method.

    A.
     
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