Laser boom inner sleeve

Discussion in 'Laser Talk' started by stuck in the 80s, Oct 19, 2011.

  1. Rob Hair

    Rob Hair Member

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    I'm also very happy that the sleeves are still available. I recently bought two older boats (#555 and 116810) and needed sleeves for both. I'm not racing them, but do take some comfort in not worrying as much about applying lots of vang tension.
     
  2. Denome

    Denome New Member

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    For those interested: I purchased a boom sleeve from APS and it arrived this week. It is for a boom on a 1978 laser (sail no. 53741). It is an 1/8 inch short of 36 inches, making it just shy of 900 mm. Diameter is 1 11/16 inches. I will try to add pictures.
     
  3. cskudder

    cskudder Active Member

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    +1 from me FWIW

    Mine's a 1973 boat which I only sail for fun. I just put $50 into a "custom-engineered" 15:1 vang, which y'all know vastly improves performance, but it's a revelation and a treat to me. I've used it a couple times now and have watched that old boom bend. I stumbled upon this thread recently, and it's the first I've heard of a sleeve inside. And having watched the boom bend, the sleeve is now at the TOP of my Christmas list.

    So there's at least one of us, one more of us, out here buying this stuff. I dunno and can't figure if we're a big enuf group to keep it economical/profitable for APS etc to keep selling sleeves, but I'm getting mine soon and am very glad I can, before the boom breaks and costs me more.
     
  4. Denome

    Denome New Member

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    Here are photos of the boom sleeve sold by APS. Sells for $33 and includes gooseneck plug and rivets (which if bought separately is priced at $11).
     

    Attached Files:

  5. Merrily

    Merrily Administrator Staff Member

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    If the builder doesn't continue making them, then APS will not be able to sell them.
     
  6. cskudder

    cskudder Active Member

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    Thanks a lot Denome. Can you try to measure the thickness of the wall of the tube? Even approximate is of course ever-so useful.
     
  7. 49208

    49208 Tentmaker

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    IIRC, the wall thickness of the builder supplied sleeve is less (almost half) of the tube used for the boom itself..
     
  8. tonyquoll

    tonyquoll Member

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    The boom inner sleeve I received today measures 900mm long, 44mm outside diameter and has a wall thickness of 1.8mm. Not sure how to convert that into fractions of an inch.
    Denome measured 1 11/16 inches, which I think is 43mm; slightly smaller.
    My boom (Laser 24877, from 1976 Australia), measures 50mm outside diameter with a wall thickness of only 1.5mm. It bends noticeable when I crank the vang on!
    Two problems arise with fitting the sleeve:
    - the end plug is damaged after being tapped out; ordered a new one.
    - there's a 3mm gap between the sleeve and the boom tube. Could have been worse; was expected to have to hammer it in and struggle getting it past the small bend, where the vang attaches.
    Photo: The new sleeve inserted into the old boom
    [​IMG]
     
  9. tonyquoll

    tonyquoll Member

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    Found this thread, which describes installing a boom sleeve: http://sailingforums.com/threads/boom-reinforcing-sleeve-installation.5404/
    It confirms the sleeve is usually smaller diameter than the boom inner, as measured above. They mount them along the bottom of the boom.
    For positioning, they say to refer to the Class Rules, which say:
    "18. BOOM (a) A metal sleeve supplied by the builder of maximum length 900 mm may be fixed inside the boom. The sleeve shall not extend aft of the point 1220 mm from the front end of the boom (including plug)."
    1220 (max distance) - 900 (sleeve length) - 6(gooseneck plug) = 314mm of variation. However the mainsheet block is fitted about 1100 from the end of the boom, so if that is also to be riveted to the tube, then there is only about 110m of variation left.
    I guess having the boom sleeve extend to 50mm aft of the mainsheet block, 1156 from end of boom with cap fitted, 240mm from gooseneck-end of boom tube, would easily be within the rules. This would also provide maximum stiffness at the vang; where mine bent & I've had booms (on other type of boat) fail in the past.
     
  10. AlanD

    AlanD Former ISAF Laser Measurer

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    Make sure you position the sleeve correctly as the position can be easily measured should a measurer feel like it.
     
  11. stuck in the 80s

    stuck in the 80s Member

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    A big thanks to all that went out there way for me to get this information,

    its set in time now on this forum,

    for anyone else who may need this invaluable information the future
     
  12. tonyquoll

    tonyquoll Member

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    Are you agreeing with my proposed placement, or not?

    Reminds me of these great sailing tips:
    To get your boat going at top speed, you need to trim the sail correctly and use your bodyweight properly.
    The best way to win races, is to be first across the finish line.
    Winning championships is easy; you just have to finish with less points than the other competitors!
     
  13. urbo100

    urbo100 Ian

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    Haven't read all the posts but another effect of more boom bend is that it makes the foot of the sail shorter, i.e. the clew and bottom of the luff get closer. This then causes the distance between
    the foot and the boom to get bigger which causes a fuller sail, which is what you don't want when you're cranking on the vang to depower the sail. Thats why on a lot of boats that have a
    loose foot they have a boom with a deep section which reduces boom bend.
     
  14. martyn

    martyn Member

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    You could always pull on some more outhaul, thus extending the foot of the sail again.
     
  15. tonyquoll

    tonyquoll Member

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    the issue with mine, was that sufficient vang and outhaul to hold the sheet flat would put a massive bend in the boom, likely to create a permanent bend and cause it to break.
    It was necessary to limit the load, in order to protect the boom.

    Wondering why the boom vang is also called a kicker. Why would you ever kick it?
     
  16. Wavedancer

    Wavedancer Upside down? Staff Member

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    :) You kick it when the boom hits your head because the vang is on too tight during a tack
     

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