Monohull Speed: Speed Dream by Vlad Murnikov

Discussion in 'Sailboats' started by Doug Lord, Jan 8, 2010.

  1. Paul Scott
    Joined: Sep 2004
    Posts: 303
    Likes: 8, Points: 0, Legacy Rep: 84
    Location: Spokane, Wa

    Paul Scott Senior Member

  2. Paul Scott
    Joined: Sep 2004
    Posts: 303
    Likes: 8, Points: 0, Legacy Rep: 84
    Location: Spokane, Wa

    Paul Scott Senior Member

  3. Paul Scott
    Joined: Sep 2004
    Posts: 303
    Likes: 8, Points: 0, Legacy Rep: 84
    Location: Spokane, Wa

    Paul Scott Senior Member

    last one- kind of complex though- there is a term for this- force alignment, and comes from Bernard Smith. Ketterman also used a downward pulling foil on the trifoiler, actuated by the 'feelers', which could go either way, pulling and pushing up and down.

    Frankly, I don't know why a small aerohydrofoil wouldn't work as a a base for a kite foiler, as long as the kite was attached to the base and not the sailor. 3 little trangles and 2 tubes of carbon and a kite. Probably not that simple, but.....

    http://www.monofoil.com/
     
  4. Doug Lord
    Joined: May 2009
    Posts: 16,643
    Likes: 315, Points: 93, Legacy Rep: 1362
    Location: Cocoa, Florida

    Doug Lord Flight Ready

    ==============
    This is worth thinking about-from Peter Lynn-thanks for the link:

    There was one hydrofoil development we did (that is, myself, Robert and Pete) that I'm not yet completely sure was mistaken. This was the "mophs" initiative. Standing for "mode optimising planing hydrofoils" these are hydrofoils that work as such until a certain threshold speed, then rise to sit on the water's surface and plane. The problem they solved was the speed limitation that hydrofoils are subject to by ventilation- in practice, about 45knots (certainly less than 50kn anyway). Mophs aren't subject to this limit. In chop or waves they blast through the wave tips with un-attached flow over their top surfaces rather than rising to each wave- which is also less bumpy than a conventional planing hull in such circumstances and may even generate less drag. For kite sailing though, mophs don't become necessary until speeds are above what we're limited to (for now anyway) by other considerations, so moph development ceased by about 2001
     
  5. Doug Lord
    Joined: May 2009
    Posts: 16,643
    Likes: 315, Points: 93, Legacy Rep: 1362
    Location: Cocoa, Florida

    Doug Lord Flight Ready

    -----------------------------------------------
    Ketterman "DLA" :

    HYDROFOIL SAILBOATS IN GENERAL
    "Hydrofoil boats can be categorized into two categories; 1) Incidence controlled hydrofoils* and 2) surface piercing hydrofoils. The difference lies in the way the boat maintains the proper altitude above the water surface. A surface piercing hydrofoil boat maintains proper height by varying the amount of foil submerged. The boat raises up as the speed increases and reduces the amount of foil submerged and therefore the lift. The boat finds equilibrium at the proper altitude. An incidence controlled hydrofoil sailboat has a mechanism that controls the angle of attack of the foil to maintain the proper altitude. It is generally believed that surface piercing is simpler, but incidence control is more efficient. In reality, it is the method that works with fewer problems that is simpler.
    From the beginning it was felt that incidence control was better suited for a sailboat even though most of the existing hydrofoil sailboats were of the surface piercing type. There are many advantages of the incidence controlled foils; however, the most important is what I call the DLA (dynamic leveling affect). This is the increase in righting moment or stability due to the ability of the windward foil to pull down. The DLA has little affect on the low wind performance, but it essentially makes the top speed of the boat limited to the strength of the boat. Conventional boats with a finite amount of righting moment can only extract so much power from the wind, but with the DLA, the righting moment is virtually unlimited.
    Intuitively many people think that the added drag of the windward foil plus the increased induced drag of the leeward foil would offset the gain in righting moment, but calculations show and practice proves otherwise. The dynamic leveling affect not only produces a dramatic increase in top speed, but is also responsible for all the other key features that this stability provides.
    The other major advantage of the incidence controlled foils is they are less affected by the waves and other surface affects. Drag and losses associated with the surface are the major reason incidence controlled foils are more efficient.
    All hydrofoil sailboats have problems with ventilation; however, surface piercing foils have larger problems, because the foils are piercing the surface at a smaller dihedral angle which makes it easier to ventilate."

    ------
    * On the Trifoiler the entire foil was moved to control RM, lift and negative lift hence the term "incidence controlled foils". On the Rave the incidence was generally fixed at +2.5 degrees for the main foils though some owners found a way to decrease the incidence on the windward foil. Lift and negative lift on a Rave foiler is generated by the wand (designed by Dr. Sam Bradfield), a surface sensor(dragging in the water) and attached directly via linkage to a flap on each main foil. The wands are independent just like the trifoiler "incidence controlled" foil sensors.

    http://www.hobiecat.com/sailing/TriFoiler History Original/Magazine Articles/Multihulls 1990.htm
     
  6. RHough
    Joined: Nov 2005
    Posts: 1,792
    Likes: 61, Points: 0, Legacy Rep: 793
    Location: BC Summers / Nayarit Winters

    RHough Retro Dude

    If you could get this to work it might be the best of both worlds. I am pretty much convinced that for high speeds planing surfaces have more potential.

    Where foils shine seems to be flying through the "hump". It takes less power to stay on plane than it takes to get there.

    My gut feeling is that below some speed, long and skinny is lowest drag and above some speed planing is lowest drag. In between is where hydrofoils rule.

    I also suspect that one of the reasons that bigger skiffs are not faster is because of aerodynamic drag, not hydrodynamic drag.

    R
     
  7. Doug Lord
    Joined: May 2009
    Posts: 16,643
    Likes: 315, Points: 93, Legacy Rep: 1362
    Location: Cocoa, Florida

    Doug Lord Flight Ready

    ====================
    I agree ,especially after reading Beavers paper on the aero drag of a Moth that was so substantial. That goes for the 26'Mirabaud as well. They've proven faster than a Moth but one look at that thing shows tremendous aero drag. I think this is an area where a lot thought should be given. And probably an area where the preliminary renderings of Speed Dream seem to be very good.
     
  8. Paul Scott
    Joined: Sep 2004
    Posts: 303
    Likes: 8, Points: 0, Legacy Rep: 84
    Location: Spokane, Wa

    Paul Scott Senior Member

    A proof of concept RC by DL? :)
     
  9. RHough
    Joined: Nov 2005
    Posts: 1,792
    Likes: 61, Points: 0, Legacy Rep: 793
    Location: BC Summers / Nayarit Winters

    RHough Retro Dude

    Yep. One of the things that seemed obvious to me in AC33 was that DZ was much cleaner aerodynamically than A5. I got pretty well beat up by a bunch of people over on SA for daring to say so. The proof was that DZ walked the big cat. :)

    Tubes, struts and wires are great for weight control, but very bad for drag. If a design looks like a WWI biplane, chances are it will be as slow as a WWI biplane.

    If the rules allow, just getting the leeward rack of a skiff to retract into the lee of the hull would increase speed.

    If you are willing to give up any hope of speed while the hull in is the water, the hull shape should be designed for the lowest drag while flying. That might end up looking like a board with a stepped mast and racks to reduce lateral hull area. The surface area would kill you in sea-hugger mode, but once out of the water it could be faster.

    Speed Dream has some good ideas, but I think the control systems and the power needed to run them will keep the project from reaching it's potential. I honestly don't see why anyone would put that much effort into a program just to keep a "mono-hull" label.

    R
     
  10. Doug Lord
    Joined: May 2009
    Posts: 16,643
    Likes: 315, Points: 93, Legacy Rep: 1362
    Location: Cocoa, Florida

    Doug Lord Flight Ready

    ===============
    I doubt it ,Paul. At model scale planing seems to work a bit differently but I am going to build a new test model so maybe. Wouldn't be that difficult to try...
     
  11. Paul Scott
    Joined: Sep 2004
    Posts: 303
    Likes: 8, Points: 0, Legacy Rep: 84
    Location: Spokane, Wa

    Paul Scott Senior Member

    Rrough- An early modern 18 (It's in Higher Speed Sailing) had wings exactly as you describe. Very much the IC/Moresby Canoe/Class A cat plank approach.

    To really clean up aero, the Moths will have to take a possibly painful look at their rules.
     
  12. Paul Scott
    Joined: Sep 2004
    Posts: 303
    Likes: 8, Points: 0, Legacy Rep: 84
    Location: Spokane, Wa

    Paul Scott Senior Member

    Low Reynolds # effects?
     
  13. Doug Lord
    Joined: May 2009
    Posts: 16,643
    Likes: 315, Points: 93, Legacy Rep: 1362
    Location: Cocoa, Florida

    Doug Lord Flight Ready

    ===================
    I don't think that is his reasoning, even remotely: Vlads' interest is in speed period and I think he believes that in combination with lifting foils a mono could be faster than a multi with foil assist. I tend to agree with him.....The downside is that it will take a huge amount of development/experimentation which is where his new 35 footer comes in.
     
  14. Doug Lord
    Joined: May 2009
    Posts: 16,643
    Likes: 315, Points: 93, Legacy Rep: 1362
    Location: Cocoa, Florida

    Doug Lord Flight Ready

    =============
    Probably-I'm not sure I fully understand it. I've built numerous 36-60" models using my "Power Ballast System" that damn sure should have planed
    but they didn't even though they greatly exceeded hull speed. On the other hand, guys like Savitsky and Eugene Clement got (apparently)good results from relatively small planing hull models.
    Hydrofoils seem to work quite well at very low Reynolds numbers.
    I think there is something I don't quite understand-maybe I'll figure it out someday.

    Note: the chord at max on the F3 foil was a 1.375" and it would take off in a 5 knot wind.(or when being towed by hand by one of the Hobie pedal kayaks)
     

    Attached Files:


  15. Paul Scott
    Joined: Sep 2004
    Posts: 303
    Likes: 8, Points: 0, Legacy Rep: 84
    Location: Spokane, Wa

    Paul Scott Senior Member

Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.