Aercraft - Sailer ?

Discussion in 'Boat Design' started by Manfred.pech, Jun 8, 2016.

  1. Manfred.pech
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    Manfred.pech Senior Member

    Aircraft or Sailer ?

    http://www.v-rex.eu/

    [​IMG]

    The floats at the ends of the wings are tanks for water ballast.
     
  2. Doug Lord
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    Doug Lord Flight Ready

  3. Manfred.pech
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    Manfred.pech Senior Member

  4. Doug Lord
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    Doug Lord Flight Ready

    VRex

    I'm not sure. It doesn't seem to have the potential of SailRocket because it seems to rely on "normal" righting moment and apparently "normal" foils. But we'll see...
    What do you think?
     
  5. Manfred.pech
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    Manfred.pech Senior Member

    Sorry Doug, I am not a Naval Architect and not able to do all the calculations and the engineering to make such a design flying and safe. A design work which is only revolutionary and nice on the eye is completely worthless without models and tests and math.
    To combine aerodynamic and hydrodynamic elements in a vessel like above needs research, hard work and financial fundamentals. Therefore I do not dare to try a statement.
     
  6. Skyak
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    Skyak Senior Member

    I would dare say it can work under the right conditions but I can not imagine how it could work in all the conditions that likely to occur.

    I can't help thinking that at some point the craft will get caught by a gust from behind and go right over.

    I would sure like to know what their control plan is. What is human and what is machine -what power source parameters.
     
  7. serow
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    serow Junior Member

    I can see this coming a mighty cropper now and again when it goes from about 60 knots to zero in a couple of seconds then cartwheeling over a ditched float. Yes I know they've thought about it and it can't happen because the wind will spill before they hit the sea bla bla bla.
    Still, good luck to them and fingers crossed.
     
  8. Skyak
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    Skyak Senior Member

    I still recall the last time I flipped my cat. Goofy gusty day, I was gybing around and the wind just kept following me and getting stronger. I did 270 degree turn ducked down on the tramp ready for the boom to cross and the wind just built from behind and dumped me. I was sailing much faster than the average wind and directly into the average direction that day.

    I am sure all their calculations are based on the boat being so much faster than the wind that apparent is always ahead of the beam. Can you imagine trying to get that thing out of a crowded marina?
     
  9. Doug Lord
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    Doug Lord Flight Ready

    Can you imagine getting SailRocket out of a crowded marina?! VRex is a speed machine-not a daysailer......
    =========
    PS- regarding what I said earlier about "normal" righting moment: IF they can effectively do Veal Heel* like a Moth, their RM will be anything but normal. At the height they show those foils they may be able to increase RM possible up to 50% or a bit more. It increases Moth RM-20-40%.

    * Veal Heel is a windward heeling technique first developed in the Moth by Rohan Veal. It has a number of advantages one of which is a big increase in the righting arm and therefore righting moment.

    [​IMG]
     
  10. daiquiri
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    daiquiri Engineering and Design

    Regarding the V-Rex:
    Don't know, but I have like a feeling that those underwater foils are meant to create a downwards and not an upwards lift... The upward force seem to be the lift from the leeward wing in ground-effect.
    It is an equilibrium of forces which might work above a certain speed, but the transition from full stop to that speed is what really puzzles me.

    Hope that they did they calcs very carefully, because if the underwater foil stalls, it will be a big bang.

    The movable water ballast implies energy storage, electric pumps, sensors and other electronics, so I guess that the whole craft will have an automatic flight-control system, with a movable canard at the bow for pitch control.

    Automatic flight control system is something I have been advocating for years here, as the IMO only mean of making foiling sailboats usable by common untrained and non-athletic boaters. I will never believe in the success of various Gunboats and similar until I see them implement a reliable fly-by-wire with a full control over the foils system. Automation is a part of the future of sailing, like it or not. ;)
     
  11. Doug Lord
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    Doug Lord Flight Ready

    V_Rex

    The info page Manfred posted says this: (I hadn't looked carefully at the link Manfred posted-there is a lot more info there than I realized. It's worth a close look!)

    " V_REX converts its own weight into positive sail pressure. Speeds of more than 60 knots make it the new king of speed"

    Isn't that what any sailboat does? And they use water ballast to take off. I would think the crossarm wings control veal heel(they hope) which controls RM and may allow ditching the water ballast at a certain point. Most of the renders show Veal Heel......

    At any rate I wish them good luck!
     
  12. Manfred.pech
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    Manfred.pech Senior Member

    Don't mix it, Doug! You have posted the link first and you are the only one to understand the Veal Heel concept of Peter Steinkogler (successful Tornado sailor in Austria).
     
  13. Skyak
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    Skyak Senior Member

    There is a lot more on the site since I last looked. Now it is revealed as as a speed record attempt looking for funding.

    As such I would move on to the questions -Can it beat the record? and can it reach 60Kn it claims -or should I say They have already declared themselves the "speed kings" and assumed the 60kn speed.

    For starters, lets pick up where sailrocket left off
    My recollection is that sail rocket had reached the limits of their water foil in terms of cavitation. Based on foil angles, sail rocket is loading their foil significantly less than V Rex and V rex has a T configuration which has greater drag at the junction.

    In the sail I would also give the advantage to the sailrocket wing -higher lift, higher L/D, and better control. V rex site says they will use a Tornado sail rig -makes me wonder where the $600,000 will be spent.

    The last point is that Sailrocket is just plain naturally stable, vs V rex losing energy to control. The only losses sailrocket has that V rex does not is the skimming hulls -but those were small and lightly loaded.

    It sure doesn't look faster to me.
     
  14. daiquiri
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    daiquiri Engineering and Design

    Yeah, but that's how it works, usually. They can't collect money from sponsors if they don't promise big things. ;)

    True. But let's imagine a situation described in my previous post. Nearly all the lift created by the WIG at the lee side. In that case, the underwater T-foil serves just to balance the moments and create some sideways force. It means that it should pull down instead of pushing up. In that case the cavitation at the junction is avoided, as it is in the region of high pressure.

    I agree. But that might change at a next design stage, after and if they realize that the current rig design is inadequate.

    Yes, it could be so. On the other side, if the lee wing is indeed a WIG, then it would also give the boat an inherent roll stability, as a lift of a WIG increases as the distance from the water surface decreases.
    If the pitch control could be obtained with the canard visible at the bow, then the control losses could be quite small.

    Of course, this is just for the sake of discussion. I actually know nothing of how that stuff is actually supposed to work - just guessing. :)
     

  15. Doug Lord
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    Doug Lord Flight Ready

    VRex

    There is another difference between VRex and Sail Rocket: this boat can sail on both tacks.
     
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