Gust Response

Discussion in 'Sailboats' started by SuperPiper, Dec 7, 2009.

  1. SuperPiper
    Joined: Jan 2003
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    Location: North Of Lake Ontario

    SuperPiper Men With Little Boats . .

    Yes! That is almost exactly . . .


    . . . the opposite of what I had in mind.

    I suspect that a keel that provides the same planform area but has less resistance to rolling will have a long chord at the hull and have a short chord far away from the hull. That is pretty much the shape of a conventional keel. However, I suggest that it will be proportionately thicker at the tip than close to the hull.

    So I have tempered the idea of intentionally heeling my boat. Sailing heeled is not efficient. However, if caught by a gust, one form of dynamic gust response may be that the boat will heel until I can re-trim the sails and/or adjust her heading. When I find the new trim, the boat will roll back down and it may pay back some of the invested potential energy.

    Coming out of a gust, "it doesn't accelerate. Just doesn't slow down so quickly" according to TeddyDiver.
     
  2. tkk
    Joined: Jul 2009
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    Location: Finland

    tkk Junior Member

    When righting back from the heel, doesn´t the sail move as well creating a little bit more apparent wind? Like a bird flapping a wing.

    That was what I though originally you were after.

    If you rock your boat back and forth in dead calm and tack the sail properly on each swing you should be able to propel it. Like "air sculling" :-D
     
  3. capt vimes
    Joined: Apr 2009
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    Location: Austria

    capt vimes Senior Member

    it will not pay anything back...
    the heeling will slow her down because of the increased drag... and the 'pay back' by rolling is insignificant....

    oh.. and 'intentionally' heeling is no good idea...
    it means that you either have a wrong trim or too much sail hoisted for a given wind... ;)
     
  4. bistros

    bistros Previous Member

    Dinghy sailor here, so discount experience accordingly ...

    In super light winds, heeling intentionally can cause a sail to assume intended shape better than having it hang drooping and shapeless if it is kept vertical. Having the correct sail shape is critical to rig efficiency in light winds, so it is standard practice to force heel on dinghies in very light wind. Proof is in all the races won.

    Intentional heeling is also done during roll tacks and gybes - where legal and rule abiding sailing can cause the boat to generate drive from the kinetics of using body weight to make the boats roll drive the rig. Don't know how many times I've used kinetics to drive the boat during no-wind situations, as we don't have stinky motors that relieve us of waiting in the middle of the water for wind.

    That being said, dinghy (no to low wind) techniques are not all that applicable to people that have lead poisoning!

    --
    Bill
     
  5. SuperPiper
    Joined: Jan 2003
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    Location: North Of Lake Ontario

    SuperPiper Men With Little Boats . .

    This is what started the thought process.

    My little boat has a strake molded into the bottom of the hull on either side of the retractable keel. I'm convinced that their sole purpose was to provide rigidity to the hull in this loaded area. However, I'm also convinced that these can be replaced by glassing the liner (berths, bulkheads, etc) to the hull and creating stringer profiles inside the finished hull.

    I have not seen strakes on performance keelboat hulls. I don't think they have a hydrodynamic function. In fact, they probably interfere with the smooth flow around the hull. And, they probably create drag while the boat's roll angle is changing.

    Can I get rid of them?
     

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  6. Cheesy
    Joined: Aug 2008
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    Location: NZ

    Cheesy Senior Member

    At a guess I would say that they are there so you can beach it without having to worry too much about scratching the hull
     

  7. SuperPiper
    Joined: Jan 2003
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    Location: North Of Lake Ontario

    SuperPiper Men With Little Boats . .

    Help me with this project, please.

    I have a number of glassing projects this winter. The tailings from the epoxy pot will get poured into the strakes on the inside of the hull with some glass scraps: a sort of mish-mash. When the filled strakes are more or less fair with the inside of the hull, I will grind the entire area smooth and apply a number of layers of bi-axial.

    How many layers of 6 oz? Can I use Gerr as a reference?

    Then, the protrusion on the outside of the hull will be cut and ground to create a little bit of a divot. Several layers of glass will be applied until the hull is fair.

    How many layers of 6 oz on the outside? Can I use the Gougeon manual as a reference?
     
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