Monohull Speed: Speed Dream by Vlad Murnikov

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

  1. bulk-head
    Joined: Dec 2007
    Posts: 58
    Likes: 2, Points: 0, Legacy Rep: -5
    Location: Antigua

    bulk-head Junior Member


    Good man.... now...Back on topic please.....
     
  2. Paul Scott
    Joined: Sep 2004
    Posts: 307
    Likes: 8, Points: 18, Legacy Rep: 84
    Location: San Juan Island, Washington

    Paul Scott Senior Member

    I have a small question which I hope might belong here: it seems to me that the conversation has been centered around powered up conditions on craft which are using lift (hull, foils,, boards, etc.) and what little leverage that can be found with weight to control lift devices (sails, kites wings). So at the limit, it seems to me that this amounts to small differences trying to keep lift from blowing up in your face. As Phil S over in SA has put it to me, it's the instability of the Moth system that makes it work. I suppose you could say that about the Windsurfer, Kite and Multi's too. But it seems the specific type of lift outside of propulsion is what makes each of these craft better in one way or another beyond displacement conditions to just beyond the point of fully powered up, and then it's trying to figure out how to depower just enough to keep things going, which is a discussion that is beginning to creep into this thread, I think. And I think this is why windsurfers have consistantly stayed at the the forefront of speed because, while an upright rig is more powerful, a canted rig is effectively reefing instantly. The Moth uses lift almost exclusively, but in an unstabile configuration, which gets a bit hairy at the limit, Kites are just beginning to understand more controllability, but at what cost to the rider, and multi's still flip over. But this is where Bethwaite's idea of leverage comes in handy, because in these particular unstable systems, this is really all you've got, unless you use monohull style ballast, which is becoming faster and faster, as it ideally works towards stability. Without intending to send DL to paraphrase the Famous Speech in King Henry V again, what about Bruce foils? It's one way to use dynamic force for stability rather than weight leverage, but maybe there's a problem there I'm not aware of? Can't sail one in a speed trench? Uncontrollable in a Kite which is where it would seem to be the most desirable? Too much power is a system? (Using Formula fins on light air Kites seems kind of a step in this direction- but it's a light air application.) The idea keeps on popping up, but obscurity seems to descend....... Maybe rules punish the idea?

    Hope this doesn't seem too obvious a question.

    Paul
     
  3. Doug Lord
    Joined: May 2009
    Posts: 16,679
    Likes: 346, Points: 93, Legacy Rep: 1362
    Location: Cocoa, Florida

    Doug Lord Flight Ready

    ============
    If I understand you correctly you are considering the use of a foil to add stability? You say "Bruce foils but I guess I really don't understand the difference between "Bruce Foils" and surface piercing foils except that "Bruce Foils are most often referenced, as far as my dysfunctional memory can recall, as foils used to augment stability -generally, on one side of a boat.
    The best examples I can come up with for foils used for stability are the foils on a Rave, Osprey or Hobie trifoiler with independent altitude control systems that allow a boat so equipped to generate its own RM up to the structural limits of the boat. Works well at high speed despite the extra drag due to the increased loading of the foils. I know of one proa, the name escapes me, that used one "Bruce Foil" that was manually adjusted each tack by the skipper.
    On a Moth this would probably not work because of rules-I don't know about on boards or kites that seem to have RM pretty well taken care of.
    ---
    However, I had an idea that MIGHT be able to be used on a bi-foiler other than the Moth: use very small "power foils" at the widest point of the boat-extend the beam a little if necessary to unload the foil. The idea would be to have more sail on the boat than the RM possible from crew weight and veal heel could handle past say 12-15 knots of wind then deploy the small foil and wand to pull down on the windward side. I did some preliminary calculations that seem to show that the small foils could add a lot of RM in stronger wind with an acceptable L/D ratio and yet would not penalize the boat in lighter air except for a slight amount of extra weight.
    Here is a rough sketch illustrating the idea:
     

    Attached Files:

  4. Doug Lord
    Joined: May 2009
    Posts: 16,679
    Likes: 346, Points: 93, Legacy Rep: 1362
    Location: Cocoa, Florida

    Doug Lord Flight Ready

    foils for RM or ballast

    This is a comment by Tom Speer( and it is a direct quote, not a paraphrase) :

    " I asked Mark Pivac why Spitfire had water ballast instead of using dynamic downforce on the windward foil. His answer was, "So it only has to be lifted once." And he was dead right. The leeward foil has to lift both the weight of the boat and the downforce from the windward foil. If either downforce or ballast are used, the load on the leeward foil is the same. However, there is a drag penalty for creating the downforce. There's no drag penalty for the ballast."

    I'm not sure I fully understand this because it seems to me that there would be some penalty for carrying xtra weight at takeoff but then again if you fill the water ballast only when you need it this makes more sense.
     
  5. Paul Scott
    Joined: Sep 2004
    Posts: 307
    Likes: 8, Points: 18, Legacy Rep: 84
    Location: San Juan Island, Washington

    Paul Scott Senior Member

    By 'Bruce Foil' as I first saw one, I mean a surface piercing foil that pulls down, not lifting up. Seems to me that you can't get much more elegant, abstract, or minimal than a kite pulling up and a foil pulling down, whether surface piercing or not. Seems a mite more to the point than trying not to skid across the water. Harder to jump over 20' sailboats, though.

    I wouldn't want to be the kite sailor holding the two together, though....

    I know I can find some pics of the concept, but I'm off to some Christmas cheer!

    Ho ho ho

    Paul
     
  6. Gary Baigent
    Joined: Jul 2005
    Posts: 3,019
    Likes: 132, Points: 63, Legacy Rep: 509
    Location: auckland nz

    Gary Baigent Senior Member

    Well. obviously there is a drag penalty for carrying ballast of any sort, but the drag of a negative lift windward foil (which is a Bruce foil, I think), has to be also very high. Maybe someone has done calculations showing the difference between the two, taking an average ballast weight on an equal length design to that of a negative angle of incidence windward foil. My guess is the draggy windward foil will be more damaging to performance.
     
  7. P Flados
    Joined: Oct 2010
    Posts: 604
    Likes: 33, Points: 28, Legacy Rep: 390
    Location: N Carolina

    P Flados Senior Member

    For the above point, Tom Speer got it right where so few others have even noticed.

    Any force generated by moving fluid over a surface creates drag. The more the force, the more the drag. The one force we can get without a drag penalty is when we use simple ballast for the downforce.

    Longshot is a craft that looked capable of so much more with some additional development.

    Imagine if all crossbeams on Longshot were round beams shrouded by twist-able airfoils linked to the forward floats such that on each side the airfoils would be the same angle of attack as the J foils. You have to have the crossbeams anyway for structural reasons, they are producing drag as is, so why not get some lift and active control out of them.

    Add in the ability to take on water ballast in a windward tank using a scoop tube that can be lowered into the water. Now for a specific one-tack run, remove the windward J foil and start out with the ballast tanks empty. As the boat powers up, you take on ballast into the windward tank as needed to keep the windward side of the twist-able crossbeam airfoil close to a neutral angle of attack. The movement gives some active control at very low AOA's so drag is very small. This would completely eliminate any drag from a windward J foil in the water. The leeward J foil would probably need to be designed to run deeper to let it deliver the required lateral forces, but this would not be a problem.

    For the discussion on Kiters and roll balance. Cheesy, you are probably right about using more kite load adjustment control than I wanted to admit. However, I am pretty sure I see more heel as the conditions get heavier. I am still convinced that the with the geometry such that max heel can get the overturning moment arm so small is very important in the really heavy stuff.

    And for using Kites on boats, I keep expecting to see more of this, but the logistics of launching, controlling and landing are not trivial. I have dreamed of a large fixed Biplane wing assembly that would float on the water with the wings pretty much vertical. As the craft sped up, the horizontal surfaces on the wing assembly could then be angled to produce lift and fly the entire assembly to the desired altitude just above the lousy surface air. This has an advantage of eliminating the need for wing twist as there is negligible wind speed gradient say 50' up.
     
  8. Gary Baigent
    Joined: Jul 2005
    Posts: 3,019
    Likes: 132, Points: 63, Legacy Rep: 509
    Location: auckland nz

    Gary Baigent Senior Member

    How about this year's project from Yves Parlier. Now we're talking of a BOAT.
     

    Attached Files:

  9. RHough
    Joined: Nov 2005
    Posts: 1,792
    Likes: 61, Points: 0, Legacy Rep: 793
    Location: BC Summers / Nayarit Winters

    RHough Retro Dude

    The big difference is that weight is limited. You cannot get ballast weight to become heavier with speed. You can add ballast with a water ballast system, or move ballast with a canting keel or sliding deck ballast but once you are at the limit your power is fixed.

    Using a foil to produce the force to counter heel instead of weight gives you righting moment that acts like continuously variable ballast weight.

    The RM is not free in either case. Ballast weight needs to be accelerated and causes extra drag below the RM limit. Why lift more weight than you need?

    Paul has imagined a very fast combination. Extend the force vector from the rig to windward until it passes through the water plane and down to the centre of effort of the foil. Now you don't have to lift any weight with the hydro foil(s) the Rig does all the lifting directly. You are left with the hydrofoil lifting exactly opposite the rig force. This is the thinking behind the Monofoiler project.

    What is happening is that you are transferring the lifting load from the foils to the rig. You have to pay for that in drag from the rig, mother nature serves no free lunches. :)

    Doug is right on with the comment on structure. The forces involved lead to heavier structures, so you have a weight penalty in the structure that has to be heavy enough for the maximum loads even when loads are small. If you can use this structure to create RM the structure becomes free ballast.

    The three point systems like the Hobie and Rave (Was it Longshot that was the basis?) did not get developed to run at sailboard and kiteboard speeds and again Paul has hinted at a possible reason. It might be that you need less total surface area in contact with the water to plane at high speed than foil area to create the same lift.

    The neat thing about all this is there are so many ways to skin a cat once you are not constrained by rules that are type forming.

    R
     
  10. RHough
    Joined: Nov 2005
    Posts: 1,792
    Likes: 61, Points: 0, Legacy Rep: 793
    Location: BC Summers / Nayarit Winters

    RHough Retro Dude

    You pay for the ballast in drag, the lifting surface is either larger (more drag) or more highly loaded (more drag).

    The question is for the same RM which system has more drag.

    If you don't have to worry about rules, you don't need to water start a kite. Inflate a lifting body with hydrogen as your rig and you can "sail" it at any windspeed.

    Wacky Green Machine idea #OU812:

    Use the ships power to separate Hydrogen from the water to inflate the kite sail, once the kite sail is flying and working you don't need as much ship's power for the passage. As you near port where the kite is not practical, you deflate the kite, store the hydrogen for the next time or use it to power a fuel cell. Could you extract enough energy from the wind to pay back the energy used to "make" the hydrogen?

    R
     
  11. Doug Lord
    Joined: May 2009
    Posts: 16,679
    Likes: 346, Points: 93, Legacy Rep: 1362
    Location: Cocoa, Florida

    Doug Lord Flight Ready

    I wonder if the one using Veelheel has the least drag for the amount of RM (on a large ocean going boat)? I was really startled to find that the proportion of RM from vealheel on a theoretical 60' foiler was over 40%. That seems like a figure that would open some doors relative to stability. The downside, for sure, is the complexity required to make something that size work particularly if it is to be selfrighting. Movable keel, movable on-deck ballast(water ect). Probably would have to be maintained at the right angle electronically or "flown" by one guy watching the angle all the time. I think it has potential that should be looked at but it definitely wouldn't be a cruising boat.....
    Speed Dreams side mounted foils may be the best allround ocean record solution-at least for now.
     
  12. P Flados
    Joined: Oct 2010
    Posts: 604
    Likes: 33, Points: 28, Legacy Rep: 390
    Location: N Carolina

    P Flados Senior Member

    All righting moment schemes use up force or lift on the leeward side (at a hull, planing surface, hydrofoil or airfoil) and down force to the windward side. The distance between these forces is the moment arm and the more you separate the two forces, the less the size of the force has to be.

    When you use ballast for a down force, there is NO DRAG if it is enclosed in an existing structure. If the ballast is crew hiking out or on a tramp, there is air drag. The down force is really just the weight which exists even if there no air/water flow. Regardless of how you get down force on the windward side, there will be an upward force required on the leeward side.

    The air drag for active ballast (crew) is an interesting discussion on its own.

    For roll control on a C Cat with one hull flying, the only drag associated with righting moment is the drag the leeward hull (and potentially foils) generates to produce the lift to leeward and the air drag of the ballast (crew) on the windward side. I have wondered if a C Cat at max speed would actually go faster with the crew prone just above the windward hull and water ballast taken on. The overall weight would be higher, but the air drag would be lower. If the foils are very efficient and picking up a big percentage of lift, you can probably generate more total righting moment this way even though the moment arm is not as long. For heavy air conditions, I have even thought of a fold out or slide out a beam (similar concept to the International Canoe) with a 14" wide x 5' long flat on the end where the crew could crawl out and lay down face into the wind. The skipper would have to manage all the controls, but single handers do this all of the time. The total righting moment could be increased with a reduction in total air drag. Again, the C Class rules allow more flexibility than most.

    It would seem that many of the smaller/faster classes have would benefit from more effort in minimizing air drag from the crew.
     
  13. P Flados
    Joined: Oct 2010
    Posts: 604
    Likes: 33, Points: 28, Legacy Rep: 390
    Location: N Carolina

    P Flados Senior Member

    Doug,

    Long before the moth foiled, people dreamed of using windward heel such that the weight of the rig provides ballast for righting moment. If you take this to an extreme, a high center of gravity is actually a plus. Hanno Smits is credited with a concept that has a wing with pilot way up inside. The wing heels to windward while the craft rides on Tee foils. You have to poke around some on his web site, but a lot of his stuff is interesting anyway. http://www.wind-water.nl/monitor.htm

    Alan Kruppa, has a patent on using a High CG wing tilted to the windward for ballast https://docs.google.com/fileview?id=0B08eDMTRSu-jNWU2NWE3M2EtOWE4Yi00MGFhLWEwMzQtYzhkYzk4OWJlZWY5&hl=en&authkey=CJesnTU He also has a web site discussing his concepts. http://www.radboat.com/

    How far you can push this concept and still handle the logistics of launching, control underway, tacking, etc. is a big question.
     
  14. Doug Lord
    Joined: May 2009
    Posts: 16,679
    Likes: 346, Points: 93, Legacy Rep: 1362
    Location: Cocoa, Florida

    Doug Lord Flight Ready

    ============
    Thanks for the info! There appears to be a lot to gain in making a "60'Moth" work......
     

  15. Paul Scott
    Joined: Sep 2004
    Posts: 307
    Likes: 8, Points: 18, Legacy Rep: 84
    Location: San Juan Island, Washington

    Paul Scott Senior Member

    here's something

    http://www.sailrocket.com/node/169 ...n.com/projects/ingenious/sail/kwing/kwing.htm
     
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.