Whites Dragons-mini hydroptere-esq

Discussion in 'Multihulls' started by Doug Lord, Oct 13, 2010.

  1. Doug Lord
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    Doug Lord Flight Ready

    Whites dragons: designed and being developed at University of Gonova(Genoa)....Different then Hydroptere in that it is a cat and has two rudder T-foils. More similar to Hydroptere.ch minus the retractable steps/planing hulls.
    ----
    From Doug Schickler on SA:

    I would be remiss not to mention other supporters: cut-paste:

    www.ribacomposites.it
    www.modelleriabrussolo.com
    www.styacht.com
    www.YCI.it
    www.angeloglisoni.com
    Cantieri Punta Manara
    Rostan
    North Sails Carasco

    ---foils are supported partially and retracted by a carbon tube that is pivotably attached to the foil and pivotably attached to a sliding car on the underside of the forward cross beam-no "shocks".
     

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    Last edited: Oct 19, 2010
  2. Doug Lord
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    Doug Lord Flight Ready

    Whites Dragons

    From the front page of SA:

    Concept:
    The main goal was to create an easy boat, simple to transport, which can be sailed on foils instinctively, hardly different than a regular cat. Further, it had to be tremendously fast.

    Design and Construction:
    The two students designed and ultimately self-built this 2 person hydrofoil cat, almost exclusively of carbon fibre. Working with carbon A class hulls as a starting point, and borrowing the sail plan and mast directly from the Tornado class, they were well on their way. Simulation based design, tutored by Davide Tagliapietra, focused on flight dynamics, VPP, foil hydrodynamics (CFD) and accurate dimensioning of newly built components using Finite Element (FEA).

    The choice of V (surface piercing-dl)foils, devoid of the need to actively alter the lift surface, fit the simplicity and transportability concept well. The hydrodynamics of the foil at the free surface, the limits on stability, and the impact on platform beam are the compromise.

    Then they went and learned how to build a boat as well. Starting with pointers and tips from a small composite boatyard Punta Manara, they climbed the learning curve. At the end, vacuum bagging substantial components came easy. For the foils and main beam, they turned to the pros at Riba composites.


    Here you see just how wide the platform is, with a trampoline 2x wider than long!

    Principal Data

    LOA 7m
    LWL 5.5m
    Beam 4m (!)
    All up weight 125kg
    Mainsail area 16.35 m2
    Genneker ca. 17-20 m2

    Testing and Refinement:
    The project was first tested in tow in late September. Huge efforts were necessary to handle the concentrated loads on the platform induced by carrying the weight and developing the righting moment on such small areas. The tensile structure originally made of synthetic cables has been completely replaced first with steel rod and then remade with carbon straps to give rigidity.

    By October the boat was sailing regularly and the results were convincing. The cat was flying high and stable on its hydrofoils, easily carrying one 75 kg person and even foiling with 160 kg of crew in 12 knots of wind. Handling was easy, just as predicted. The most recent session on Wednesday of this week saw the boat flying very smoothly and easily.

    Speeds over 20 knots with only the main were achieved.
    Tests were carried out with two crew and the genneker, pushing the boat ever harder. With the genneker, the boat was able to fly in about 6 knots of wind. Due to a lack of instruments, the best indication so far of sailing angles is that the apparent is well forward when the boat is up. Video.

    Next steps for refinement will be concentrating on proper sizing and positioning of V foil fences in order of increasing high speed performance. One of the next steps will be further sail development, a new main, and a flatter genneker is also under development.

    Further the team will address the righting moment limitations of the design. In addition to double trapezing, which has not been utilized to date, the mast will be significantly canted, providing a portion of the lift, allowing for a wider stance of the foils.

    Plans:
    Regattas such as Round Texel, Bol d’Or, Multi cento and perhaps some record runs. The boat will be at the Dusseldorf Boat Show in the new year, on display at the request of the Tornado World Champion Roland Gaebler.
     
  3. Doug Lord
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    Doug Lord Flight Ready

  4. Doug Lord
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    Doug Lord Flight Ready

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  5. SouthernComfort
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    SouthernComfort Hillbilly Engineer

    Whats the probability of one of these taking a sudden nosedive due to debris or part failure?
     
  6. rapscallion
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    rapscallion Senior Member

    That looks like a fun ride!
     
  7. Doug Lord
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    Doug Lord Flight Ready

    ============
    From what I gather it is very well engineered so part failure is fairly unlikely. Hitting debris depends on the conditions where it is sailed. Probably unlikely.
    Team Hydroptere has worked on a system to avoid partially submerged objects or objects just under the surface which is definitely important for a big foiler in the ocean.
     
  8. SouthernComfort
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    SouthernComfort Hillbilly Engineer

    Thanks for the response. Sorry if it was a dumb question, i'm new to the true multi hull design world. My only multihull experience has come from 5 years building boat docks by way of a 30 foot pontoon, and my 24' pontoon. I didnt take into consideration the geography of where these would likely be sailed. I'm thinkin of my debris infested Cumberland river. Thanks again.
     
  9. Doug Lord
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    Doug Lord Flight Ready

  10. Tom.151
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    Tom.151 Senior Member

    Doug;

    Would you try to explain something to me about those main foils...

    the tips on the main foils are turned down (as are the tips on Hydroptere).

    I was laboring under the belief that the tips of lifting foils were best when turned up - capping the end-flow onto the low pressure side of the foils, as opposed to trapping the high pressure on the bottom surface.

    Perhaps I have tacitly inferred from the newer generation of aircraft wingtips that this is the reasoning behind the choice, but I would like to learn which is correct - tips up or tips down, and why.

    Thanks for any sense you can help make of this phenomenon,

    TomH
     
  11. Doug Lord
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    Doug Lord Flight Ready

    Whites

    Tom, I read a story on the Hydroptere site, I think, that the tips were down but vertical(not 90 degrees to the foil) because that tip is used to enhance lateral resistance when going very fast. Probably the same on Whites, but I don't know for sure.
    PS I found this picture showing the tips-the angle they're at is very similar to the angle on Hydroptere so I'd be 99% sure that their purpose is the same. And since they're both surface piercing foils the tip would be a much larger percentage of the immersed foil area at top speed.
    click-
     

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  12. Gary Baigent
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    Gary Baigent Senior Member

    They are turned down to give some bite (anti-leeway, lateral resistance, whatever) I like bite, because plane 40-45 degree angled foils, no tips, are not the best in going to windward; not bad but not the best. The angled windward foil hooking the water, does next to nothing either ... because with leeway and the angle of attack around 2-3-4 degrees, is actually going through the water at around zero or 1 degree or so. Plus it is ventilating because half or more of it is out of the water. So contrary to what some say,(unless the windward foil is set at negative angle of incidence, high drag though) not helping the boat climb to windward. But the deeply immersed near vertical tips do help. However, I doubt that Hydroptere is much of a beating to windward boat, outstanding close reaching though it may be.
     

  13. Tom.151
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    Tom.151 Senior Member

    Thanks Doug,
    certainly make more/better sense (than I inferred) for the purpose (than I inferred) of the tips - the 2nd photo in the original post made the tips look v.much shorter that the view you posted above. They still look small, but considering the lateral component of the lift vector is additive maybe not.

    Thanks Gary, for the added details.
     
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