Cork Talk - Making Your Spars Airtight So They Float

Discussion in 'Sunfish Talk' started by oldpaint, Jul 8, 2017.

  1. oldpaint

    oldpaint Active Member

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    I recently replaced my 1969 AMF Alcort Sunfish lower spar with a donor spar that was the upper spar on a Super Sailfish. I moved all the original hardware, blocks and the straps that hold them over and added fancy thick sticky tape to the gooseneck area to prevent the corrosion that forced this work. Today I added new corks inside the spar.

    The bow end has the interlocking eye bolts and its easy to see that the endcap can't really be made to be airtight. I took the endcap down to the hardware store and was suprised that they had four drawers of Midwest Fastener cork stoppers. These are the aggregate type, not the natural cork type used in the 60’s but close enough. Size number 18 looked correct when held up to the endcap, slightly bigger than the outside diameter of the spar. They were $2.05 each. I bought a pair. Back home I relieved the inside edge of the spar with emery cloth and also cleaned out old caulk. I used silicone grease to lubricate the cork and the inside of the spar. To avoid damaging the cork. I held the flat end of a ball peen hammer against the cork and tapped the ball end with another hammer. I bought the silicone grease at the same hardware store a month earlier in the plumbing section. That type of grease shouldn't attack the binding glue holding the cork together (time will tell).

    The outhaul end was fast. PB blaster on the pin holding the endcap. Forced the pin in using a small nail after dulling the point. Took off the encap, saved the pin and did not loose it! Installed the cork in the same way, put the cap on and tapped the pin in.

    As far as masts go, A few years ago I used the advice on the forum to use a racketball in each end. They do the job.
     
  2. Light and Variable Winds

    Light and Variable Winds Well-Known Member

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    Most spar corrosion seems to be attacking from the exterior; however, I still give a spritz of anti-corrosive to the interior after caps are removed/replaced.
     
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  3. oldpaint

    oldpaint Active Member

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    The corrosion on my original spar was on the outside. A lot of pitting where the gooseneck had been clamped, to the point that its strength looked compromised. I had filled the pits with epoxy which kept them from getting worse, but that didn't add any structural strenth. Anyway I started this thread in case anyone wanted information on replacing the cork. It'll be easy to find with a search.
     
  4. Light and Variable Winds

    Light and Variable Winds Well-Known Member

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    If you've saved your old spar, I'd suggest cutting off a 16" length.

    Lengthwise, cut a 1 inch section out of it, making it into a giant "split pin".

    With its natural affinity to retain its original shape, it can be driven inside the spar to reinforce the area where the clamping force of the gooseneck has weakened the spar. (Or will weaken it, by eventually crushing it).
     
  5. oldpaint

    oldpaint Active Member

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    Neat idea. One thing I found on my old boom was that the mainsheet blocks had gouged grooves into the boom over the years. I checked the Sailfish boom and it was also damage by the blocks. That's why I converted the Super Sailfish upper spar into a Sunfish boom. I suspect this is a common to a lot of boats. Structurally doesn't make much of a difference, but having a spare spar in good shape it made sense to change it out.
     

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