Where do i put the sail and lee board?

Discussion in 'Sailboats' started by Chikokishi, Aug 8, 2011.

  1. Chikokishi
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    Chikokishi Junior Member

    [​IMG]

    I built this sailboat a couple years ago and i had a major issue of when i was sailing it would sail at an angle to straight because my sails position caused the boat to turn around the leeboard.

    Now my girlfriend and i would like to build mini sharpies and sail them (http://www.simplicityboats.com/minisharpie.html) But i would like to know how to figure out where the leeboard and sail should be? As the side of the boat is curved it would seem that you can only put the board at the point where it would be straight with the boat, but then where do i put the sail/ how do i figure that out?

    Chiko
     
  2. Chikokishi
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    Chikokishi Junior Member

    Iv been looking at pictures, and the board seems to go near the center of the sail. By chance does it go at the center of effort on the sail?
     
  3. CutOnce

    CutOnce Previous Member

    Generally, a little forward of the COE - making the boat carry a little bit of weather helm (so letting the tiller go causes it to automatically slowly turn upwind and stop). You have to take the jib into account and balance to two centers of effort according to percentage of sail area contribution.

    In your picture above, the leeboard looks much too far aft, and the boat would probably display severe lee helm (trying to turn downwind constantly).

    You have to add shimming to the leeboard attachment point to get the leeboard to be on hull centerline, even if it isn't at the middle of the boat.

    There is lots of good reading on this (maybe way too much). Experiment with clamping the leeboard on in different spots till it feels right.

    -
    CutOnce
     
  4. lewisboats
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    lewisboats Obsessed Member

    CutOnce is correct...From the old mk1 eyeball I would expect the center of the leeboard to have to have been placed about 1/4 of the length of the boom aft of the luff of the sail and then a bit of mast rake to tweak the feel. That is WAY too far aft. A daggerboard would probably be needed for that boat to get the centers placed properly.

    You will have to find the centroid of the sail area (Jim Michalak has good instructions on how to do this in his news letters{ http://www.jimsboats.com/15oct10.htm }) and adjust the mast position and to some degree the leeboard position to get these properly located. What kind of sail rig will also have an effect on where it goes. A sloop rig like your old boat will necessitate the board go further forward while a low aspect square sail completely behind the mast will have the board further back. Getting everything to fit into a really small boat is like stuffing sumo wrestlers into a Smart For 2...a little on the tricky side.
     
  5. Chikokishi
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    Chikokishi Junior Member

    Thanks for the info! On the boat pictured i ended up taking the jib off because even with the rudder fully turned the boat would still crank for the wind. With that boat i decided i wanted to learn how to sail and i built it within the month. Since then i have learned a bit more!

    Is the center of sail area and the center of effort the same spot?

    With the two boats we are building now we are considering gaff, sprit, or lanteen. Which would you suggest for a 7'8" boat on small lakes? We want to keep them cheap so i want a sprit or lanteen, but i like the classic gaff look. I dont know, ideas?

    Chiko
     
  6. BATAAN
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    BATAAN Senior Member

    The answer is 'put it in the right place' and that is where the helm is neutral almost, with very slight tendency to turn into the wind.
     
  7. BATAAN
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    BATAAN Senior Member

    Single spritsail.
     
  8. BATAAN
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    BATAAN Senior Member

    By which I mean clamp it on with a wedge and slide fore and aft until it's right.
     
  9. Chikokishi
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    Chikokishi Junior Member

    Bataan,

    Thanks well do that when we get them in the water. What kind of spritsail? Do you have any links that could help? Iv found many different types.
     
  10. BATAAN
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    BATAAN Senior Member

    Mast as far forward as possible. No standing rigging. Mast is greased and can easily rotate. Rectangular sail. No boom. Sprit has a 'fork' on the bottom and sits in a loop of line tied to the mast. Top has a shoulder and fits in an eye. See books by R.D. "Pete" Culler for all details.
    Here are two larger examples, but the proportions are the same and for a small boat the mast goes in the extreme bow. Your boat is a little bit too short to really work well, and 11' would be much better.
     

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  11. BATAAN
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    BATAAN Senior Member

    One example of an 11' sailing scow. This one has a sail that is far too heavy.
     

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  12. Chikokishi
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    Chikokishi Junior Member

    I was wondering about those, when the wind shifts to the other side, what keeps the sprit from getting in the way of the sail? Or does the sail fold over the sprit?
     
  13. CutOnce

    CutOnce Previous Member

    Sail goes right on top of the sprit on one tack. Performance if technically better on one tack, but in reality isn't a major issue. Probably a point or two difference in the tacking angle, or a little less speed on one tack. At the size of boat we are talking about the differences would be unnoticeable.

    --
    CutOnce
     
  14. BATAAN
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    BATAAN Senior Member

    You get a wrinkle and an unmeasurable difference in sailing.
     

  15. Chikokishi
    Joined: Mar 2010
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    Chikokishi Junior Member

    [​IMG]
    [​IMG]

    Here are the two types that i have found. Is there a big difference between them other than one is gaff and the other is sprit? I really like this shape.

    Thank you for all the help, sorry if i am nit picking the discussion.

    Chiko
     
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