Speed Dream 27 Prototype

Discussion in 'Sailboats' started by Doug Lord, Sep 20, 2011.

  1. Doug Lord
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    Doug Lord Flight Ready

  2. Doug Lord
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    Doug Lord Flight Ready

    Interesting new design devlopment for the Speed Dream Project: Vlad is now going with a stepped planing hull. Prototype should be launched soon:

    (See update posted on SA)

    click on image to see step:
     

    Attached Files:

  3. Alik
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    Alik Senior Member

    I always said that having hull 'partly supported' by hydrofoils makes no sense...
     
  4. Doug Lord
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    Foil Assist

    -------------------
    Well, a lot of designers disagree with that. DSS uses a foil to partially support the boat(and increase RM) and has proven successful on a couple of boats so far. And then there are the multitude of other eaxamples of the use of "foil assist" on monohulls: the National 12, the Chreub, the brand new Arup and the I-14, and at least two Open 60's using curved lifting foils. Don't want to leave out multihulls where most if not all race boats are now using "foil assist"
    in the form of curved lifting foils from beach cats to the 130' Banque Populaire-the fastest round the world record in history.
    Alik, was that a misprint or did I misunderstand- you couldn't possibly believe that foil assist doesn't work-can you?
     
  5. Alik
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    Foil will increase RM and might create side force. But if we are talking about hull partly supported by foils (as on Vlad's original scheme), it seems more reasonable to have hull completely lifted by foils, not dragging the belly in water with added resistance of foils.
     
  6. Doug Lord
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    ----------------
    Alik, all the boats I mentioned in my last post use foils to partially lift the boat. All are very, very succesful. Some of the multihulls are designed to lift a large proportion(70%) of the weight on a single ama foil like the older ORMA boats and the new MOD 70's. They leave a small amount of the weight to be supported by buoyancy and act as pitch control for the boat.
    Vlads original concept utilized a version of DSS to partially lift the boat and increase RM. I can't tell whether or not he is still going to use that foil with the stepped hull-I've written to him to find out and will post his response here.
    Here is some reference material you may find interesting:

    Renderings: 1) Quant 28(now replaced by the Quant 30) with DSS, JK50 with DSS soon to be launched cruiser racer,
    Picture: 25' DSS "Brace, Brace, Brace"
     

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  7. Alik
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    Alik Senior Member

    Will see; seems they have done some calculations.

    On foiled boats - many sailboats are being designed using empirical approach not really maths behind; I remember one successful CSTAR trimaran which lost the foils during race and became faster :)

    What is interesting - use of planing hull shape (such as stepped hull) usually assumes lift on hull, not on foils. And for typical planing hull resistance of appendages (P-bracket, shaft, etc.) would be 15-20%. With foil, we are talking about much higher percentage...
     
  8. Doug Lord
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    Doug Lord Flight Ready

    ==============
    Biekers work on the I-14 lifting foil is very detailed as is Kevin Ellways. But Morrelli and Melvin, Vincent Laurent Prevost(?sp) and others including the designers of USA17, designers of several Open 60's and others including Hugh Welbourn-top ,well regarded NA's have looked at foil assist very, very carefully and found that it works well-and more than likely used extensive maths(!) in addition to extensive real world testing. And it the cases of I-14s, National 12 Dinghies, Open 60's,ORMA 60's, Mod 70 multihulls , Banque PopulaireV(round the world record), A class cats, Quant 28, "Brace..." and many others the results are proof beyond a shadow of a doubt of the viability of well designed and engineered foil assist applications.
    As to your last comment: the large tri's Sodebo and Idec-about 100' LOA- were originally built w/o lifting foils but after their experience at sea the skippers insisted that lifting foils be added-not so much for speed as for improved handling.
     
  9. Alik
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    Alik Senior Member

    Sailboat designers use less math then You might think... In sailblat design world, there are no budgets for real research and a lot is done by intuition.
     
  10. Doug Lord
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    Doug Lord Flight Ready

    ---------------
    The Hydroptere Team designed a 40'(?) test boat called "Hydroptere.ch"(thread in multihulls) that uses variable geometry hulls to create a planing step in the transition to full flying foiling. During the transition (while on the step) they use "foil assist t-foils".
    Parlier, whose planing cat pioneered a multihull step design also used rudder t-foils.
    And you're probably familiar with Eugene Clements very small step powerboat designs that used a rudder t-foil. I've enclosed his design booklet below if you haven't already seen it.
     

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  11. Doug Lord
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    Doug Lord Flight Ready

    ===================
    Be that as it may-the results speak for themselves. I think you may underestimate the "maths" used in top level raceboat designs and especially by Bieker, Welbourn, Morrelli and Melvin etc. But whatever tools they use they produce proven results for lifting foils used as "foil assist".
     
  12. Alik
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    Alik Senior Member

    This is completely different story; they use foil instead of aft lifting surface. It makes sense in theory, once friction drag is major component for planing hull they replace aft lifting surface by more efficient hydrofoil.
     
  13. Doug Lord
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    ===================
    It is, however, foil assist, right? Of course it is........Parlier, Hydroptere.ch......
     
  14. Alik
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    Alik Senior Member

    Yes, I agree about the results and met some of those guys. As to maths - in most cases limited to stationary modelling (such as VPP); I am well aware of what is used :)

    Would be good to see some maths behind Vlad's project.
     

  15. Doug Lord
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    Doug Lord Flight Ready

    ================
    I hope to have a lot more info and I'll post it here though I'm not sure how detailed it will be. He is constantly making improvements to the design and is trying to come up with a monohull that will be faster than current state of the art multihulls-that is a high mountain to climb.
     
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