Where do i put the sail and lee board?

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

  1. BATAAN
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    BATAAN Senior Member

    Sprit needs no halyard as you furl by rolling it up and lower it by removing the mast.
    Liking the shape and having it work are two completely different things.
    Liking is about emotion. Sailing is engineering.
    A rectangular sail gives large area and a vertical leech without a boom.
    Vertical leech works better because it doesn't collapse in light air.
    Your gaff sail there is on an 11' foot boat and has a boom, very different from your less than 8' shoebox.
    If you had a boom it would have to be high enough to duck under, making the sail much too high and too small.
    http://www.polysail.com/spritsail.htm
    Also google "sprit sail" images, then follow the links....
     
  2. lewisboats
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    lewisboats Obsessed Member


    Technically no...but practically...maybe. A sail is a 3 dimensional object and the wind doesn't always come directly off the beam. The "rule of thumb" is the CE and the centroid of the sail are the same but in practice the CE moves around with different points of sail and the heel of the boat. The balance of the boat will always be shifting and you will feel it at the helm. The main thing to concentrate on is getting the boat to be manageable on all points of sail at all heeling angles. Generally a bit of 'lead' (as in I am leading you in this race) is given to the CE based on the shape of the hull. The wider the after half is as compared to the forward half generally requires more lead to counter the weather helm generated by heeling. As the boat heels it changes the under/at surface shape and it generates more weather helm as it pushes to windward. To counter this the sail area is moved forward so as to push back. Too much and you have a lee helm (not desired at all), not enough and you are slowed down by your rudder as you fight to keep it from rounding up. You also have a tiring and unpleasant experience to keep the boat going straight. On such a small boat the numbers are fuzzy because the main factor in the balance of the boat is your own weight. You can nose it up or nose it down (changing the Center of Lateral Resistance) through shear weight shift. You can even steer the boat this way. Putting the Geometrical CE of the sail over the middle of the board is a very good starting point which can be adjusted by raking the mast fore and aft a bit (start with a bit of rake built in). You can then fine tune the ride on all points of sail by shifting your weight slightly fore and aft.

    For simplicities sake I would go with a Sprit rig (an actual sprit rig rather than a sprit boomed Leg 'o mutton or something else). Set your sprit high on the mast with a second point further down, slightly loose lace the sail with rope or wire ties and leave it loose footed. This will allow you to lower it and if you have a second sheet attachment along the leach you can reduce the area being used and effectively reef it a bit. A couple of cringles to bundle the foot up would be a good thing to add.

    Steve
     
  3. Chikokishi
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    Chikokishi Junior Member

    Iv had to google search just about every other word in this post, but thanks for the information!
    What do you mean by lead to the ce?
    "Generally a bit of 'lead' (as in I am leading you in this race) is given to the CE based on the shape of the hull."

    And thanks for that link to the spritsail site, iv been trying to find building instructions. I think ill go with that one and just convince the gf that its what we need. Im going to do a bit more learning before i post another question, and its probably already been answered. =)

    One last thing, do you know of any sites with better spritsail building detail? Like for the sprit itself? I keep running in circles and cant find much.

    Thanks for the tips!
     
  4. GTO
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    GTO Senior Member

    He means that the sails center of effort should be a small amount forward of the boat's center of resistance.

    It's my opinion that on smaller boats, to figure the CLR (the boat's center of resistance to lateral , or sideways, motion), you must include the submerged portion of the hull and also the rudder. On your particular boat, that puts the CLR well aft. Even if you move forward in the boat, raising the stern and submerging the bow, the CLR is still going to be aft.

    Go to www.instantboats.com and look at the plans for the tortoise and brick. Similar boats to what you have. That should provide you with a good example.

    Edit: Ooops, maybe not. Those two don't have good pictures available. Do a web search on Tortoise and Puddle Duck racers. That should get you going.
     
  5. Chikokishi
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    Chikokishi Junior Member

    GTO:

    I am actually building the mini sharpie, i gave a link to it in the first post. The white boat pictured was a failed attempt that i tried a couple years ago.

    Just as a side thought, if i put the boat in the water and found the point on the side where if i push it it doesnt rotate... wouldnt that be the center of resistance?
     
  6. BATAAN
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    BATAAN Senior Member

    That would be the static CLR. This has little to do with the dynamic and changing sailing CLR.
     
  7. Chikokishi
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    Chikokishi Junior Member

    On a boat my size would the resistance spot really move that much?

    Also, iv been reading that spritsail site you gave me. What are the v-darts for? Are they required?

    Sorry for all the questions! Iv been researching all day and i have not found much good information.

    For the record, we are not building these boats with intent to race or anything, we just want something that will go across a small lake without hassle. My last boat would go into the middle, but id get stuck because i was unable to tack or anything with it to make it back. Oars were extremely useful, but it was not very fun.
     
  8. BATAAN
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    BATAAN Senior Member

    V darts not necessary. Nice sail can be made from painter's tarp.
     
  9. Chikokishi
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    Chikokishi Junior Member

    That makes it much simpler. Iv been looking at a long of sprit rig pictures and i think i got them figured out.
     
  10. GTO
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    GTO Senior Member

    Given the very small cockpit on the mini-sharpie, the CLR won't move much because you won't move much.


    I suggest you build a different boat, instead of trying to figure all of this out in a day or two. You've been shown a couple of good examples. I'm biased toward the Dynamite Payson / Phil Bolger collaborations, since I built the 16' Windsprint. It's great for 2 and some gear. And all the calculations are already done. All you have to do is build it and hit the water. And the lug sail is relatively easy to build. The forum also offers great support from its moderators.

    www.instantboats.com

    If you want to build two boats, you could look at the 12' Teal. Windsprint and Teal are both "easy" to build sharpies. Here is a link to a Teal. Note that one of them doesn't have flotation blocks so it is subject to swamping.

    http://www.andrewlinn.com/2011/110716_missoula/index.htm

    The flotation issue is discussed here:

    http://instantboats.com/phpBB3/viewtopic.php?f=6&t=2947
     
  11. BATAAN
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    BATAAN Senior Member

    Strongly suggest you build something like WINDSPRINT from Payson and not try to figure all this out yourself. Really a good little boat that would make you much happier possibly.
     
  12. Chikokishi
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    Chikokishi Junior Member

    I looked at the larger boats, the reason i am building these little mini sharpies is because i dont have a boat trailer, or money to get one. And if i bet bigger than 12' id have to register it - also dont have the money for that. Plus the lakes here are frozen 9 out of the 12 months (ugh). And as i said, im not out for speed sailing, or long distance sailing, or even sailing on big lakes. These are more for my bf and i to go sit in the water and cruize like..2 mph out into the middle of the lake, and then be able to make it back.

    When i get out of school (And after iv built my ultralight airplane) i Want to build a bigger boat, in particular i want to build the Single handed Schooner. (by P. bolger) I absolutely adore that boat. But thatll be when i have a good job and money so i can supply myself with fibreglass and the right materials.

    Nope, these boats are just going to be a pond boat with a sail. Thats why i want it to be simple, and to have a relative idea of where to put things on it. My last boat failed miserably but i think i know what it did now.

    My biggest issue now is that i cant find clear directions for making a snotter rig. I see lots of pictures, but id like somethign with dimensions so that when i try to raise it up it doesnt keep fallin down on me.

    Chiko
     
  13. BATAAN
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    BATAAN Senior Member

    The snotter is like this, and it is held up by a very small thumb cleat screwed to the mast. The tightening loop at the top sits on the little cleat, there is a small bullseye or thimble seized in and a tail.
    R.D. Culler can explain it much better than I. He said he prefers manila rope for this job because it is not slippery.
    Getting his book PETE CULLER'S BOATS would make things easy for you because I think you're doing things the hard way. No motor = no registration usually, and rowing, paddling and sailing small craft are often exempt, so check out what's really happening before you decide things. A too-short boat is a very poor boat and length is the most important factor for satisfactory use.
     

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  14. BATAAN
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    BATAAN Senior Member

    12 footer don't need no trailer.
     

  15. Chikokishi
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    Chikokishi Junior Member

    Thank you again Bataan, youve been a major help! Does it matter a whole lot where i put the sprit? Because if i put it higher i could make the sprit shorter. But would that make it harder for the sprit to hold the sail up? Thats my biggest question.

    I know how to make a snotter now though =)

    Chiko
     
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