Stepped Planing Hulls/small sailboats

Discussion in 'Sailboats' started by Doug Lord, Apr 9, 2005.

  1. Doug Lord

    Doug Lord Guest

    Does anybody have any knowledge of experiments utilizing a stepped planing hull on sailboats under 20'- particularly with reference to the Plum stepped hulls?
    I know that Yves Parlier built an Open 60 planing cat using stepped hulls combined with rudder hydrofoils.Parliers steps were large "traditional" steps but it seems that there might be gains possible in adapting some of Plums work with small steps to planing sailboats.
    Any thoughts or info would be greatly appreciated!
     
  2. gggGuest
    Joined: Feb 2005
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    gggGuest ...

    Moth Steps

    IIRC there was a Moth design back in the 60s which had a very small step aft. My very dim and shadowy memory suggests it was an influential design in other ways but not in that one. That was when they first started going thin (by those days standards) with wings. I *think* may have been Nervous Breakdown design.
     
  3. Doug Lord

    Doug Lord Guest

    Plum steps

    From what I understand of these steps they can be quite small and still have a big effect in wetted surface reduction and in facillitating early planing. It appears that maybe they could be incorporated in such a way as to be retractable. And could possibly be used with a rudder hydrofoil instead of the original Plum type foil....
     
  4. ken61137
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    ken61137 New Member

    stepped hulls for small cats

    Boatek in the mid 90's did a stepped hull with a wing sail. It was unique in that it had an air intake venting out into a reverse v step so the step was running on foam
    Unfortunately Bob Quinton has now passed away but his wife as far as I know is still keeping his web site active
     
  5. Doug Lord
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    Doug Lord Flight Ready

    Stepped Planing hulls for Sailboats

    Thought I'd check again to see if anyone has read, seen anything about or experimented with Plum/Clement type steps for dinghy hulls? The step would be quite small...

    The original proboat article that piqued my interest: http://www.proboat-digital.com/proboat/200510/?pg=168
     
  6. daiquiri
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    daiquiri Engineering and Design

    The problem here is that Dynaplane was efficient because it was meant for a powerboat, which operates at 0° heel. I don't see how could it be applied to a hull which need to operate through a range of heel angles, continuously changing it's underwater form...
    If you are considering a retractable device, then something like this might be a much simpler and lightweight solution:
    http://www.boatdesign.net/forums/boat-design/midship-interceptor-24913.html
     
  7. Doug Lord
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    Doug Lord Flight Ready

    ============================
    Thanks, daiquiri. I'm considering this on a planing dinghy that is sailed flat-no heel. I appreciate the interceptor info-I'll check it out.
     
  8. Doug Lord
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    Doug Lord Flight Ready

    Wow! That seems like a far simpler solution. I'll look at it closely. It would be real simple to set up and experiment with. Thanks again Daiquiri!
     
  9. Chris Ostlind

    Chris Ostlind Previous Member


    No such thing.

    Beyond that, any speeds being sailed that do not match the tuned optimum for the stepping, will experience excessive drag, resulting in a boat with really crappy all-around performance.

    Basically, a One Trick Pony
     
  10. Doug Lord
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    Doug Lord Flight Ready

    Well, I raced several different planing dinghies for years and the boats were sailed flat in planing conditions downwind-and upwind on a boat capable of upwind planing.
    The beauty of the possible application of Clement's take on Plums work is that the boat can be configured for multiple loading conditions. Clement says: the dynaplane boat is more fun to run than a conventional planing hull because "the operator can maintain an optimum running trim angle in different water surface and loading conditions, simply by adjusting the vertical position of the stabilizer." The rear foil makes all the difference and is unlike "normal" powerboat step design.
    -----
    Thanks to Daiquiri, I have written to Jurgen regarding the Midship Interceptor
    that appears to have some of the properties of Clements design in a very simple system. I'm looking forward to finding out more. One of his comments was certainly intriguing :" At high speed the drag will be about the same as on a boat with foils, but a boat with a midship interceptor is much simpler and sturdier." And, of course the interceptor and its stabilizer can be made fully adjustable and retractable. Sure worth looking in to.....
     
  11. Chris Ostlind

    Chris Ostlind Previous Member

    .....
     
    Last edited: Dec 10, 2009
  12. ancient kayaker
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    ancient kayaker aka Terry Haines

    Don't see why a small boat can't be sailed flat if the skipper is heavy enough, since foilers and boards clearly can. Weather heel may or may not be beneficial but it is certainly optional. I imagine the advantages of a step could easily turn into a disadvantage if course and conditions do not permit planing, though, so the retractable interceotor concept might be the way to go for a sailboat. I hope you try this one, Doug, and keep us posted on the (good or bad) results.
     
  13. Chris Ostlind

    Chris Ostlind Previous Member

    Well, Terry, if you believe that, then I have some garden property for you in the desert of Southern Utah where you'll swear that you're in the fertile Garden of Eden free of rainfall and all that seems to bother man in his pursuit of a sustainable life. Wait till you see it.

    Haul out your engineer's sense of reality and tell me that a skiff will always be at an attitude of zero degrees from horizontal/vertical, depending on your reference, no matter the conditions. No... I didn't think so.

    When one makes specious claims, one needs to own-up to the frivolity of same when proven to be incorrect. You'll notice that the same character chooses to hold the World Champion of foiling Moth sailing to a very strict interpretation of everything the Champ may say. I think it's only appropriate to hold said claimant to the same razor's edge of accountability in what comes forth from his mouth/keyboard.

    Enough said.

    The flat/horizontal hull form claim is bogus and always will be.
     
  14. HJS
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    HJS Member

    Midship interceptor

    Doug Lord

    Thank you for your interest in my midship interceptor.

    You are absolutely right that the concept can be used for fast sailing dinghies. Have myself thought about using it on some of my E-class sailing canoes, but the class rules will not allow it.

    I have made comparative model tests with the Dynaplane concept and found that it can be equivalent under limited circumstances. The advantage of an adjustable midship interceptor is that it can be adapted to the need of lifting force. It is important that it can be adjusted different at keel and chine. In this way, the boat's transverse stability can be adjusted so that the heel is reduced to a minimum.

    The major work lies in finding a balance between all the dynamic and static forces in various speeds and loads.

    I am currently preparing a research work at the Royal Institute of Technology in Stockholm in order to identify the midship interceptorn function. The work will be the basis for calculating the effect of the interceptor over a wider range.

    Good luck

    Jürgen Sass

    www.sassdesign.net
     

  15. ancient kayaker
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    ancient kayaker aka Terry Haines

    Er ... I wrote "Don't see why a small boat can't be sailed flat if the skipper is heavy enough ..."

    When I step on my small sailboat it heels on whichever side I sit or stand. Ditto when I put up the sail in a breeze. I can easily balance it so it's sailing on an even keel. Not always the best thing to do in a flat-bottomed skiff of course, but it's no technological challenge. If it were important to some aspect of the boat's design that I sail it on an even keel, I certainly can. This doesn't apply to a multi-tonne monohull in a howling gale but we're only talking about dinghies here.

    -or were we talking about different things, Chris?
     
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