Sailrocket 2 set to launch

Discussion in 'Multihulls' started by P Flados, Feb 19, 2011.

  1. SteveMellet
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    SteveMellet Senior Member

    I'm blown away, Paul finally did it..
    Doug I don't really see Sailrocket as a foiling boat, it is more like a jet aircraft with one hand dragging in the water ! :D
     
  2. prograd
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    prograd Junior Member

    This is impressive!
     
  3. Manfred.pech
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    Manfred.pech Senior Member

    Are there any drawings of the foils - comparing the new and the older one ?
     
  4. Doug Lord
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    Doug Lord Flight Ready

    Sail Rocket

    ---------------
    There is some stuff in this thread and there is a lot more on the website-but you'll have to do a lot of searching.
     
  5. Manfred.pech
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    Manfred.pech Senior Member

    Thank you Doug. This might be the best one - comparing the development: Smaller ist better.[​IMG]
     
  6. Doug Lord
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    Doug Lord Flight Ready

    SailRocket

    Manfred, now that they've made history I'm going to spend a lot of time studying exactly how they did it. It is a significant breakthru for foiling sailboats-I'm so very impressed!
    And it is quite a tribute to Bernard Smith and the 40 knot sailboat. Too bad he didn't get to see this....
     
  7. P Flados
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    P Flados Senior Member

    Doug,

    SR2 set the record with 2 foils in the water.

    One was the rudder up front and one was the main foil set up so that the net vertical component was to pull DOWN.

    The wing is very canted and provides more upward force than the entire weight of the boat.

    The boat does not use foils to lift the boat up and as such does not fall into the category that most would call a "foiler".

    It is a Bernard Smith conceived arrangement with almost directly opposing major force vectors.

    [​IMG]
     
  8. Doug Lord
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    Doug Lord Flight Ready

    ====================
    Paul, I don't think it makes a bit of difference if the foil lifts up or pulls down-it still relies on foil action to function. The Rave, Osprey , Skat and Hobie Trifoiler all rely 50% on the windward foils pulling down for max RM.
    I'd say it most certainly is a foiler.....
     
  9. P Flados
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    P Flados Senior Member

    Doug,

    "Foiler" and "foiling" have taken on specific meaning.

    As you know, at the very basic level some form of "foil" is used for most sailing. An airfoil and a hydrofoil are actually the same devices, a blade using the flow of fluid past it to produce the desired force nearly perpendicular to the chord line. The normal "foils" on a boat are the rudder and the keel/daggerboard/centerboard. The "foil" in the water is needed such that the net horizontal vector between the sail and foil(s) can provide the forward thrust needed to sail. There are exceptions. For example, a Hobie 14 or 16 tuned to have a neutral helm can use the hulls instead of a "foil". Few people would call a boat hull a "foil" although it can provide the same function.

    My old sunfish had a dagger board the acted as a "foil" providing lift when I was heeled over even though the "foil" was very crude (a flat surface with rounded nose and some amount of taper on the back edge).

    It is a given that most sailing uses "foils", but we do not call these boats "foilers".

    If we take a survey of people that know the fundamentals of the question, the vast majority would say that a "foiler" is a boat that will use foils in the water to provide the vertical lift needed to support the weight of the boat and lift it out of the water. A "foil assist" configuration is one where the foils in the water reduce the amount of hull submergence by a significant amount when compared to a configuration where all foil surfaces are vertical when the boat is at rest.

    As for SR2, the front pod is a planing surface that stays firmly in contact with the surface. At speed, the rest of the boat weight is being supported by the wing. Therefore, in terms of what supports the weight of the boat, it is a combination of a planing boat and an airplane. Unlike Longshot, Trifoiler, Rave, Moth, Hydroptere (boats that do "full foiling"), this comes closer to my concept of a boat that "flies" (a boat using airflow induced vertical lift to support the weight boat) than any other sailboat I know of. The vertical forces from the main foil are really intended to just compensate for excess upward force from the wing and to provide passive altitude control for the rear of the boat.

    I am a fan of foiling and am convinced that foiling can effectively be used in many applications where the drag penalty that comes with generating lift is more than offset by a reduction in hull drag.

    For many craft, foil assist provides performance enhancement at a reasonable cost. Since there is no need to deal with altitude control, the least complex choice is just a matter of making all of the parts and pieces of the right shapes and lining them up in a beneficial orientation. Foil assist with adjustments to allow optimizing for a range of conditions is better, but again we add cost and complexity.

    Actively controlled full foilers do have their place, but this is only appropriate where the significant extra cost/complexity is justified.

    Passive altitude control on a full foiler has typically used opposed inclined surface piercing foils that are not as efficient (Hydroptere is the current champion of this configuration). The AC 72 from ETNZ looks to be a possible creative solution to reduce inefficiency for a passive altitude control scheme.

    I am actively scheming on how to use inclined surface piercing foils for a small proa configuration. All surfaces would be inclined to provide both lift and the correct direction side forces. This would allow passive altitude control with no "wasted" drag created by opposing foil generated side force vectors. Bernard Smith (the "The 40-Knot Sailboat" guy) actually made some boats that have this feature. However I see plenty of room to push farther down this path using some of the technology/material advances of recent years.

    I know you are enthusiastic about this technology. However, I would ask that you consider that you may tend to make statements that are "stretching the truth" to the point of potentially being counterproductive. I have learned much from many of your posts. I see you as an innovator and someone willing to "do the math" and do the research that adds to the collective knowledge. I try to not "stretch the truth" as some people get all emotional and twist things around regardless of intent.
     
  10. Doug Lord
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    Doug Lord Flight Ready

    SailRocket

    =================
    Paul, I emphatically disagree with you for the reasons stated in my last post. There is no doubt in my mind whatsoever that defining SailRocket as a foiler is accurate. If you say it isn't then you have to say that other boats using 50% downforce from the foils are not foilers either, I would think.
    It is lift(down) created by a foil that allows SailRocket to function-without it
    there would be no speed record. I think it is hard for some to get their head around a foil pulling down, but it has been used successfully for years.
    As for "stretching the truth", I have never knowingly done that and as far as I know I have never been accused of that except in this case by you. And I disagree.
    ---------
    I have considered whether this would be more properly defined as "foil assist". I don't think so because a "foil assist" boat just slows down a little w/o the assist from the foil whereas SailRocket would simply not function without the downforce created by the foil.
     
  11. high on carbon
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    high on carbon Wing Nut

    From wiki:

    The term "hydrofoil" is commonly used for the wing-like structure mounted on struts below the hull of a variety of boats (see illustration), which lifts the boat out of the water during forward motion, in order to reduce hull drag; as such, the term "hydrofoil" is often used to refer to boats using hydrofoil technology. Most of this article is about this type of hydrofoil.

    I am inclined to agree that in common usage a hydrofoil refers to a boat the "flys" above the surface of the water by the lifting action of foils in the water.

    Properly speaking, SR is not a hyrdofoil, it is a planing tripod. more specifically when I am drawing boats, I refer to boats like that, as a "balanced forces" craft. Specifically the foil in the water is not providing righting moment either as it is on a rave etc. They pull down in a way where the foil is away from an axis of rotation.

    On SR there is no axis of rotation about which the foils act, quite the contrary, the forces act through a simple axis the directly connects the foil in the water to the foil(wing) in the air, everything else is just along for the ride and to provide directional stability, thus it is a balanced forces craft.

    So Doug, no it is no more a foiler than a 12 meter is. Yes, it has foils, a foiler that does not make it however. If it's not touching the water, it's more a function of the wing lifting the mass of the boat out of the water.

    MC
     
  12. Doug Lord
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    Doug Lord Flight Ready

    Sail Rocket

    Ok, thanks Magnus. I guess I'm mostly convinced, Paul.
    PS-Thanks for the quick answer!
    ---------------------------------
    The thing that has been nagging me is the fact the the foil is not lifting the boat up or supporting the boats weight in any way.* But any evaluation of the foil in terms of what it does for the boat is still a bit troubling to me because it is such a critical element.
    * Found these under "Facts" on the website
    •The back of the boat will lift onto the curve of the foil at around 25 knots. The leeward float will begin to fly clear of the water over 50 knots. Only the main foil, the rudder and the ‘step’ of the forward float will be in the water at high speed.
    --
    •The curve of the main foil determines how high the boat rides
     
  13. high on carbon
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    high on carbon Wing Nut

    Well basically all sailing craft have foils of some kind or another, principally to counteract the forces of the sails. SR is just a very pure distillation of that idea so that no force or energy is wasted on doing anything other than exactly what is needed to counteract each other.

    Regular boats complicate matters by having to deal with buoancy and they rotate about the center of floatation, on SR, there is no need to do that. The boat floats when still, but is picked up like a kite boarder when at speed, just skimming a bit over the waves, which is planing lightly.
     
  14. Doug Lord
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    Doug Lord Flight Ready

    Sail Rocket

    But SR is as dependent(or more dependent) on the lift from the hydrofoil as it is on the lift from the wing or planing float.
    It's tough for me to shake this analysis of the boat based on the action of and importance of the foil. This boat is as dependent on lift from the foil as is any other hydrofoil, right?
     

  15. Corley
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    Corley epoxy coated

    With the success of this attempt it makes you wonder what the future direction of this type of speed sailing craft will be.

    For example would it be possible or beneficial for the concept to scale to a larger platform? Or would that just yield more weight and no appreciable benefits? Recent sailing speed records seem to point to smaller craft being more able to achieve high speeds over a short course with no wave action. Is there a cutoff point where extra size simply becomes counterproductive in this sort of attempt? Or is that arbitrary?
     
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