Speed Dream 27 Prototype

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

  1. Alik
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    Alik Senior Member

  2. Alik
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    Alik Senior Member

    Seems he is going to present something at IBEX this year... See seminar programme.
     
  3. Doug Lord
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    Doug Lord Flight Ready

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    Doubtful. I know Hugh Welbourn personally and he would never sign off on BS.
    DSS has benefits other than just reduced wetted surface and increased RM and it's starting to show a very small advantage at 6 knots-thats logical. If the foil didn't show an advantage why would they use it? Its 100% retractable. I see nothing out of line there....
    Why not write Hugh and ask him about it?

    Early Speed Dream 27 prototype render showing DSS type foil with lateral resistance "tips":
    click on image-
     

    Attached Files:

  4. Alik
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    Alik Senior Member

    Why does it have reduced WS?? Should be increased WS compared to boat with no foil. Moreover, foil moving in proximity of free surface would also add wave resistance! So advantage should be reached at certain speed when RM is getting important.

    Are there any scientific publications on this foil, not just marketing from website? As usual, there is always more marketed advantage than real advantage, just be 'careful pessimist' to check it out.
     
  5. Doug Lord
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    Doug Lord Flight Ready

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    The foil lifts vertically and reduces displacement by the amount of lift.
    More info ,post #9 here: http://www.boatdesign.net/forums/sa...30-twin-dss-foil-equipped-keelboat-42710.html
    http://www.boatdesign.net/forums/sailboats/quant-28-foil-assist-keelboat-dss-38421.html
     
  6. Alik
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    Alik Senior Member

    This is marketing material again; it would be interesting to see real comparison with all known data for compared options.

    What I wonder is: if we look at resistance curve of typical hydrofoil craft, can note that mode with partial submersion of bottom and partial support by foils gives greatest resistance, there is a main hump on resistance curve. So why this mode is used as design point for boats?
     
  7. Doug Lord
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    Doug Lord Flight Ready

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    What is a "typical hydrofoil craft"?
     
  8. Doug Lord
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    Doug Lord Flight Ready

    Speed Dream

    Still haven't heard from Vlad(but I will) and in searching around I found this:
    http://www.doylesails.com/news/tag/speeddream
    Now, the verbiage in this announcement mentions a "25% increase in RM from the lee foil" BUT the picture attached shows no visible lee foil but does show a rather conventional vertical daggerboard with no surfaces that would produce vertical lift even when heeled.
    The picture also clearly shows the step in the hull.
    (lookat the original renders on the first page to understand the changes)

    video published by Lyman Morse-builder of the proto March 7,2012: http://www.youtube.com/watch?v=dJuhwRwjPmg

    click on image:
     

    Attached Files:

  9. sharpii2
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    sharpii2 Senior Member

    It is clear that the thinking on this project is evolving.

    The stepped hull is clearly designed to plane, leaving me to wonder about the utility of the DSS foil

    Once the boat starts planing, with a stepped hull, it can skip across the water like a stone, offering very little surface resistance.

    The extreme cant of the ballast keel allows this to happen with no fear of stalling or breaking the surface.

    Presumably, once it gets planing, wind gusts will only add speed, as the friction will max out at a certain point, as the hull will be in the air as much as it's in the water.
     
  10. Doug Lord
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    Doug Lord Flight Ready

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    I'm not positive its not going to be used on the Speed Dream proto but the latest render does not show a DSS foil. But don't forget DSS has been used successfully on at least two fast ,planing hull boats so far-the Quant 28(and now Quant 30) and "Brace, Brace, Brace.
     
  11. Perm Stress
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    Perm Stress Senior Member

    It is because increased resistance comes hand-in-hand with increased righting moment=more driving force available.
    As it appears from published real-world data (Like yachting world yacht tests) this trick works in a sense that driving force gain is bigger as resistance gain many conditions.
     
  12. Alik
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    Alik Senior Member

    Might be, but should be modelled; from my estimates they are not. 'Yachting world' tests - those are pure marketing; actually I stopped reading this magazine years ago. Unless it is published on serious peer-reviewed scientific paper where one can see what is compared to what, I would not trust those results.
     
  13. sharpii2
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    sharpii2 Senior Member

    I'm not disparaging the DSS foil.

    On certain boats, it will be an excellent device.

    I would much rather figure out how to move it from side to side under the boat, than trying to figure how to deal with the massive loads of the canting ballast keel. (which I think should be outlawed in racing, because it requires an engine constantly. For the fastest mono ever, I'd be willing to make an exception).

    But on SPEED DREAM, I afraid it will be more of an encumbrance.
     
  14. Doug Lord
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    Doug Lord Flight Ready

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    Yves Parlier used a stepped planing hull on his big cat. There was even a plan to use variable geometry to eliminate the step in light air. As fas as I know that was never implemented.(It was implemented on Hydroptere.ch) I don't know the details yet but the step on Speed Dream as shown would be a big drag in lite air. Parliers step didn't add to the boat until speed was over 20 knots where resistence dropped precipitously. Be interesting to see how Vlad intends to do it. Also will be interesting why he would have dropped the DSS foil if, in fact, he has.
     

  15. Paul B

    Paul B Previous Member

    More fluff, and misleading fluff at that.

    The title of the video is "SpeedDream Under Construction at Lyman-Morse Boatbuilding". Yet somehow there is no footage of the boat or prototype under construction.
     
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