Loose footed mains

Discussion in 'Sailboats' started by Polarity, Dec 12, 2003.

  1. Polarity
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    Polarity Senior Member

    Hi All

    A lot of the recent Open 50's and 60's seem to have loose footed mainsails.
    Whats the benefits / down side?

    Thanks

    Paul
     
  2. tspeer
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    tspeer Senior Member

    Pro's:
    - Better shape in the foot
    - Simpler to build the boom
    - Easier to attach the sail
    - You can letterbox the spinnaker

    Cons:
    - Not as convenient for storing the main on the boom
     
  3. SuperPiper
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    SuperPiper Men With Little Boats . .

    Were the A/C boats loose-footed? I thought that one of the boats tinkered with a wide boom section to further reduce spillage under the foot.

    In the Uffa Fox days, the vang may have been used to bow the boom and to flatten the mid-section of the mainsail.
     
  4. gonzo
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    gonzo Senior Member

    Loose footed mains cause the boom to get out of column more than if it is laced or in a groove. This means it has to be stronger, therefore heavier.
     
  5. SailDesign
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    SailDesign Old Phart! Stay upwind..

    Gonzo - I had always worked on the pricipal that a loose-footed sail with end-boom sheeting was the perfect way to ensure that the boom stayed in column. Adding a vang obviously negates this, though, which explains why many open-class boats have no fixed vang.
    As far as the loose foot advantages, my favourite is the fact that any water that lands on the sail can escape quickly, preventing capsize in many cases. This is not personal experience, but reported from customers since 1990...
    Steve
     
  6. Paul B

    Paul B Previous Member

    I don't understand this thought at all. The load path for the main along the foot goes from the clew (above the boom) to the tack (also above the boom). Whatever material was riding in the track was simply along for the ride. This was especially true with the very baggy foot pockets that were made from very light cloth, sometimes even from nylon.

    The majority of the loading vertically is from the clew to the head along the leach. It doesn't matter if the sail is loose footed or not.

    Therefore a loose footed main would not be any more apt to go out of column than a main with a boltrope in a track.

    Loose footed mains have worked well for boats like the Laser since the early 70s, and every race boat main I've seen for about the past 15 years has been loose footed, including the AC boats.
     
  7. PaulCoffin
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    PaulCoffin Junior Member

    tspeer,

    I've got to ask: What is letterboxing the spinnaker?

    Thanks,

    Paul
     
  8. gonzo
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    gonzo Senior Member

    The vang gets the boom out of column and also the sheet if it not attached to the end of the boom. With the foot of the sail attached to the boom the effort is spread out more. The lower part of the sail can be more efficient if it is attached to the boom when going upwind. Observe the direction of the wind on the sail. It goes upwards, with the angle increasing with heel. The boom and mast are the leading edge at high angles of heel. It would depend on the boat to what degree it affects it.
    Paul B:
    I'm curious, what kind of boats have you seen?
     
  9. dougfrolich
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    dougfrolich Senior Member

    PaulCoffin,

    Re; "Letter Box" When one recovers the spinnaker through the slot (of a loose footed main) between the mainsail and the boom.
     
  10. SuperPiper
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    SuperPiper Men With Little Boats . .

    Wyepacket

    Since this thread brought up the question, I have been studying the Wyepacket photos.

    With the mainsail foot tight upwind, one would swear that it had a foot groove. However, the downwind photos show the main with its "shirt tail" hanging out.

    Where is the shirt tail when the boat is sailing upwind? Does it retract into the boom? It does not appear to be either hiding to leeward or folded to windward when the outhaul is ON. The shirt tail is similar to the deck gasket that the Italians used on their jib during the A/C. I don't believe that it is substantial enough to provide power to the rig.
     
  11. Paul B

    Paul B Previous Member

    Shirttails?

    The first generations of loose footed mains had a lot of foot round "hangdown" that could be quickly rolled and stuck in place with a small piece of velcro when going upwind. That seems to have gone away in recent itierations, with much less cloth below the tack-to-clew load line. There is still some extra cloth, but not so much to require it to be rolled.

    Most high tech carbon booms these days are made without any groove at all for a boltrope or slides.

    The clew is simply attached to the boom with a velcro strap that goes through the clew and around the boom a couple of times. The tack is still pinned as usual. Attach the outhaul and you are ready to hoist.

    When the outhaul is ON the main is in the same position as it would be with the foot of the sail in a channel.


    I don't know why someone would think the sailcloth would add structural strength to the boom, to resist the bending load of the vang. For that to happen the sail would have to become flat, with load bearing along the entire foot to the head and luff. Maybe if you made it out of a flat sheet of aluminum and welded it to the boom and mast...
     
  12. gonzo
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    gonzo Senior Member

    The foot attached to the boom spreads out the effort instead of the load being concentrated at one end.
     
  13. Paul B

    Paul B Previous Member

    Silly raceboat designers, sparmakers, and sailmakers

    Somehow they just don't understand this concept. They continue to go against this theory and produce those loose footed mains. You know, the ones that cause the booms to be overweight and the sails to be inefficient.

    How do people like that get to the top of the profession?

    I guess they'll never learn...
     
  14. jonathan
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    jonathan Junior Member

    Another benefit of having a loose footed mainsail.
    Generally on Open 60s, some multihulls and the like, the gooseneck is not on the mast, but on the deck, a little bit aft of the mast. What that does is that as you sheet out, the sail bellies out by itself, just like releasing the outhaul. It also allows the rotating mast, if fitted to rotate freely without having to take the loads from the boom. On non rotating masts, it is one load point less on the mast.
    Ok, so maybe those were benefits of having the gooseneck on deck... Ah well. ;) But seriously, I don't think you can have that arrangement without having a loose footed main, so I guess it applies....
     

  15. SuperPiper
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    SuperPiper Men With Little Boats . .

    Some of the entry-level sport dinghies do not have a boom at all. They rely on a batten and a mainsheet aft of the sail. This is like sailing with a jib only.

    But for those of us who still have foot grooves, what are the advantages of an attached mainsail? Should we scrap our booms? Will a sail with a foot rope work as a loose-footed main?

    Jonathan, I like the discussion about the deck-stepped gooseneck.
     
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