New Technology:Quant 30-Twin DSS Foil Equipped Keelboat

Discussion in 'Sailboats' started by Doug Lord, Apr 16, 2012.

  1. Doug Lord
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    Doug Lord Flight Ready

    Quant boats have done it again: this time a high performance 30 footer equipped with twin retractable DSS foils that eliminate 60% of the ballast of a "normal" raceboat similarly equipped. Narrow and light with folding racks. http://www.quant-boats.com/home.html
    More here: ( be sure to check out the fact that the foils are curved in planform so that both foils can be retracted next to each other)!
     

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  2. sean9c
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    sean9c Senior Member

    Now that they have a website all they need to do is build the boat. Then there might be something to talk about.
     
  3. Doug Lord
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    Doug Lord Flight Ready

    Quant 30

    ==============
    You might ought to do a little reading-it doesn't sound like you have: there is a good deal of "science" on the second page of the pdf with concrete performance info on the Quant 28 which you may recall does exist.The info for the new boat is validated by the fact that they have so much experience with the 28. They've supplied more detailed info here than most sailboat builders by a long shot.
    Details presented in the pdf include plenty to talk about especially the wierd planfor of the rotating/retacting foils and more-check it out, you might find it interesting.
     
  4. Paul B

    Paul B Previous Member

    Yeah Sean, you've miised the "science" of sailing at TWAs of 400, 450, and 520!


    You also must have missed this piece of "science": "The foil is also useful when tacking because it smooths the entire system..." I mean, doesn't that say it all?


    Then there is this: "In the best of cases when reaching, a DSS sports boat will be sailing almost twice as quickly as comparable conventional yachts."

    I wonder what defines this "best case"? Would it be the Quant using a kite while the comparable boat uses no kite?


    I've read the .pdf twice and I still don't see anything that could be considered "science". Once again someone needs to learn the difference between proved and claimed.
     
  5. sean9c
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    sean9c Senior Member

    Your post was regarding the Q30. They haven't built it, so far it's just pretty pictures and hot air.
    You think that .pdf is science? It reads like a sales pitch to me. A poorly written one at that.
     
  6. DCockey
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    DCockey Senior Member

    Why the keel? To provide righting moment in case the boat is knocked down?

    Anyone estimated the added drag due to the DSS?
     
  7. Doug Lord
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    Doug Lord Flight Ready

    =====================
    Yes. DSS has been extensively tested for over five years-I imagine every element of sailing with and without DSS has been tested thoroughly. It is a proven technology with race results to back that up.
     
  8. DCockey
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    DCockey Senior Member

    I'll rephrase my question. Is there any non-subjective data available to the public on the drag of the DSS foils?
     
  9. Doug Lord
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    Doug Lord Flight Ready

    =============
    There is a lot of non-subjective data that the L/D ratio of the foils is excellent so I'm told. Write to Hugh Welbourn if you want to explore this. PM me and Ill give you his e-mail.

    Comments by Hugh Welbourn from SA:

    #1
    Draaaag....and no, none of us do drag without a good reason)

    Look at it this way - every item in the water causes drag, so to be there it has to have a good reason to be doing something important...so keel holds a lump of lead on the end and also provides sideforce which you need. Rudder produces sideforce. Both have viscous and induced drag but you need them.
    Hull supports the thing in the water thanks to Archimedes, and has viscous, induced ( from leeway ) and wave drag.

    So the DSS foil adds viscous and induced drag, but also can operate in various modes depending on immersion depth - so close to the surface it can be a nice effective planing surface, partially ventilated then likewise but a lot of the viscous drag has gone and if its got there then you aren't using all the RM/lift that it might be producing so it doesn't need to be working hard as a fully immersed foil.

    Lift and RM....both are significant, and each design has its own requirement in how to best approach the foil and overall balance.

    If you look at the video then you can visibly see how little the hull is contributing to wavemaking, wetted surface is low and also well aerated, and so we're bimbling along steady 15-16 knots and maxed 17 in about 10 TWS and only three up - me driving, German Journalist along for the ride and Kos up front.
    Boat is in perfect balance, wouldn't be doing those numbers without the foil.
    Bit later on the breeze came up from a thunderstorm and we were doing the same numbers and a bit more just on the working jib.

    Lots more video from that day, and the weather side views make it look as if nothing is happening - practically no spray, stuff all hull in the water. But note, I'm not trying to fully fly the boat as then you get into all the trim problem - so its designed to have natural dynamic stability.

    And btw - we've done extensive testing on the 27 in big waves and seas down off Sotogrande and never had any issues from launching off waves or burying or any signs of tripping.


    ====================
    #2
    Upwind - well the thing here is to match the wing parameters to the boat so that the net result - in steady state - is just slightly in your favour. So RM gain outweighs the drag cost.
    However, what we then find is that as soon as there's any chop or seaway to move the boat around, then the damped motion in all axes makes a significant improvement that is seen on the VMG - even when you only seem to be sailing maybe a tenth quicker than you might. Now that comes from logged data and was a bit of ( pleasant! ) surprise to me until I figured out the dynamics of what was going on.

    And don't forget, you don't need to use the wing at all until you are running out of natural RM, so no draaaag....until its starts to work and then the balance is in the your favour.

    Its all a pretty finely balanced configuration but we've got a good handle on thing now from all the r&d and sailing and how to configure the different types of boat to work.

    Downhill vmg - then same again - if you don't need the wing trickling along then its out of the water, but as soon as you can get into the situation where you can AWA sail then the more power you have to use the better. Bit like cats or skiffs, but cats can't get the spare hull out of the water until theres enough breeze, and skiffs or canters all have a fixed max RM.

    So the AWA you sail on the 28 downhill is always well forward, but the angles you actually gybe through can be less than more conventional boats.

    Thing is, got two boats in one here - the light wind one is skinnyish with very low drag, but you can add in the grunt when you need it....

    Start of the Bol d'Or - dead downhill, bit of breeze - ourselves and the 36' trapeze/canter Full pelt bolted off the line at 15+ and were a mile clear of the fleet in 10 minutes - and crossing gybes with some of the cats that started 300m in front of the mono fleet....they were a bit confused to see us in 'their' water

    ---------------
    http://www.boatdesign.net/forums/sailboats/design-dss-foil-assist-keelboats-41729.html

    ---------------

    1) Welbourn on the design of a mini 6.5 proto using DSS,
    2)-3) Design and development of DSS-Daily Sail article,
    4) Seahorse article:
     

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  10. Doug Lord
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    Doug Lord Flight Ready

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  11. Gary Baigent
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    Gary Baigent Senior Member

    I'm with DCockey, Doug, referring to the keel; it seems the design/development crew are trying for a compromised, neither one thing nor the other, belts and braces situation ... why have a dopey keel if the boat is to be DSS high performance ... and why not design/redesign? a purist big dinghy hull since the major power is coming from, and relying on, DSS. This example will just be another (backward?) keel boat with a little extra horsepower ... when perhaps, it could be a real performer.
    I'm suggesting a sealed wing mast - if people freak out about capsize - decades ahead of the conservative, conventional rig they're using. They have to bite the bullet, no compromise - just imo of course.
     
  12. Paul B

    Paul B Previous Member

    If I understand the literature correctly, the plan is to sail this boat in the Swiss lakes. If so, the class it would be sailing in requires self righting.


    Don't hold your breath waiting for a realistic answer.
     
  13. Cheesy
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    Cheesy Senior Member

    Can someone explain the non dimensional "DF" and maybe the formula for it, I had a quick look but it doesnt seem quite right, maybe its just a couple of typos?
     
  14. Doug Lord
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    Doug Lord Flight Ready

    =======================
    I believe it is a metric version of displacement /length ratio(DLR). Check the pdf below, page 15:
     

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  15. Doug Lord
    Joined: May 2009
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    Doug Lord Flight Ready

    Quant 30

    Just received these pictures of the tooling on the 30:
     

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