MPX-11 Very Small High Power Trimaran

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

  1. caiman
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    caiman Junior Member

    On the subject of a 'speedo' cable type 'shaft',there are commercially available cable drives that are designed to be used with a drill to get into confined areas,if this drove a worm gear which operated the flap,then the pressure of the flap would be on the worm(which will naturally stay where it stops)rather than on the cable?Have a low gearing and drive it by a reversable cordless screwdriver type motor?Or by hand with a 'brace and 'bit'?
    Sorry if the idea is crap,it's just what sprang into my head.
    Cheers
     
  2. Doug Lord
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    Doug Lord Flight Ready

    Control systems

    ===============
    Thanks, caiman. I haven't looked for the right kind of cable yet-its good to know that they are available. In my application, the cable would be used to facillitate the control of the flap on a "J" foil by a surface sensor(wand) via a bellcrank unless some sort of direct linkage to the wand is possible.
     
  3. Doug Lord
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    Doug Lord Flight Ready

    MPX-12 Basic Specifications Page-updated thru Version 5 of the Design Specifications
    11/13/10


    ===================================
    MPX-12 Specs

    -- LOA-12' 7"

    -- LWL-12' 7"

    -- Main hull beam-5.29'-

    -- Main hull beam at the waterline -3'

    -- Overall beam- 17.5'*(15' cl ama to cl ama) updated and corrected 8/19/10--NOTE: approx the same overall Beam/overall Length as Hydroptere.(not including gantry on MPX-12) *tentative as of 11/10/10

    -- LOA- ama-10'

    -- Ama LWL(F&A dimension of planing surface)-1.5'

    -- Ama beam- 2.5(max and max at waterline-tentative)

    -- Ama Buoyancy - 3.25 cu.ft/ 208lb / 53% of sailing weight

    -- Sail Area- 178 sq.ft /25.5' mast length. Slightly taller than a scaled down A Class Cat.

    -- Main foil planform area-1.6 sq.ft

    -- Rudder foil planform area-1.3 sq.ft.

    -- Draft(max) -3.5' tentative

    -- Draft @ 10 degrees -2.2' tentative

    -- Weight-159lb all up,ready to fly minus crew

    -- Total sailing weight(displacement)- 395lb-

    -- Max crew weight-236lb

    -- Minimum crew weight(at max power)-120lb (boat can sail in same windstrength with minimum or maximum crew weight(!)

    -- Max Pressure/w/o reefing 1.8 lb/sq.ft( 1.8 for F18 cat)

    -- Designed Sailing Angle- 10 degrees from 5 knot wind. Maintained by wand surface sensor in conjunction with main hydrofoil and rudder hydrofoil.
    System allows hydrofoil to lift up or pull down automatically-regardless of wind(up to 1.8lb. per sq.ft) or crew weight(120-240lb.)

    -- SA/WS:
    a. not flying main hull-5/1
    b. flying main hull-13.8/1(moth on foils=13.65/1)

    -- SA/D= 47.47/1

    -- W/SA= 2.42 (With a 236lb crew on MPX this ratio is still better than Moth w/Veal or Payne!) (Weight/ Sail Area="sail loading"-quick and dirty comparative ratio for low resistance boats-particularly foilers. 26' Mirabaud and 11' Moth about the same.

    -- SCP/total weight= 72.9% (according to Bethwaite above 30%=capable of upwind planing)

    Notes:

    ---The crew will sit on a very comfortable sliding seat with a backrest.

    ---The seat will slide a maximum of 2' .

    ---The boat will have a simple robust folding system-nothing to take apart-ready to go in 5 min.

    ---This boat will use just two lifting hydrofoils which are critical to its operation.


    For more detail and comparisions to other boats see the Version 5 specifications sheet- post 186, page 13.

    +++++++++++++++++++++++++++++++++++++++++++++++++++++
    The Theory behind the MPX-12(based on proven performance of similar technology) :


    1) The hydrofoils' principal job is pitch control and sailing angle(heel) control. Pitch control is critical as is a well controlled heel angle for the planing ama to be effective(optimum running angle). The sailing angle is controlled by the surface sensor(wand) setting and is adjustable. The ama
    may use a small fully submerged foil set at a fixed angle to assist the planing ama in certain conditions.

    --------------

    2) The foils are designed to lift the boat off between 6 and 8 knots of boat speed-about 5 knots of wind. With the 16.5' beam the thing wouldn't fly the main hull until over 15 knots of wind or so without the lifting hydrofoils on the main hull. Most people sail in 10 or less so it is essential to have the boat perform exceedingly well in those conditions. In up to 10 knots of wind there is no need for the amas to touch the water since the crew has the ability to move to keep them clear-after that, the leeward ama gradually loads up until it is carrying most of the weight. As that is happening the foils unload reducing their drag considerably. The reserve "power" of the foils is always there for pitch control. This allows the wetted surface of the main hull to disappear early and the drag of the foils to drastically diminish as speed picks up. The beam is necessary to generate the tremendous righting moment required to sail fast in a breeze.

    --------------

    3) A side benefit of a wand controlled main foil is that not only will it lift vertically but once the boat starts to heel beyond the "set" altitude(heel angle of 10 degrees) the wand causes the flap on the main foil to go up generating downforce(extra RM) as necessary up until the maximum recommended speed where the sails should be depowered and/or reefed. This allows a very wide crew range since a 120lb kid would be able to sail with the same maximum wind pressure as the heavy crew because of the extra RM from the downforce of the foil.
    Response of the altitude control system is virtually instantaneous. Some of the early posts in this thread discuss other boats that use an altitude control system for VERTICAL LIFT and DOWNFORCE-like the Rave and Hobie Trifoiler.

    ---------------

    4) This system is critical for the performance of the boat-without it in light air or heavy air it would be a dog. All of it works together and is inter-related-without one part of the system the whole thing is useless.

    ---------------

    5) The MPX system is not just about performance: it is about performance that is easy on the crew. No other boat this length anywhere that I have seen has the combination of high performance potential, based on comparative design analysis, and crew comfort as does the MPX 12(or any boat using this system). The crew sits on a sliding bench seat that is exceedingly comfortable at the design sailing angle of 10 degrees. The seat allows the crew to move up to 2' athwartship and 3' fore and aft but the movement is only necessary when racing. For just daysailing the crew can sit in one position should they choose to.
    The foil system is completely automatic requiring only that the crew engage it. The foils are retractable and the boat can easily be sailed off a beach and trailered with the foils in their retracted position. The boat folds so that it is within the legal limit for trailering anywhere. The system will be very simple and very quick.

    ===================================
     
  4. Doug Lord
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    Doug Lord Flight Ready

    MPX-12 for two people?

    This came up the other day: could the MPX-12 take two people? The answer is yes if they each weighed 118lb. Trying to crowd more than about 236lb total on the boat would defeat the intentions of the design.
    However, if the thing was scaled up two feet to 14'7" LOA/LWL it could theoretically carry a crew weight of 368lb on a hull+rig weighing 248lb with 239 sq.ft of sail. The W/SA rises a bit to 2.57 and I'm sure elements of the design would have to be tweaked for it to function within the "ethos" of the MPX concept: extreme high performance, low physical demands on the crew.
     
  5. Doug Lord
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    Doug Lord Flight Ready

    Mpx-12---testing

    I'm going to test the foil concept of the MPX-12 on a large model being built to test the viability of a automatically self-righting small trimaran. The same platform will be fitted with radio control and the MPX foil system:
    1) lifting main foil on daggerboard,
    2) rudder t-foil
    3) wand type altitude control used to maintain a sailing angle chosen by the skipper-nominally 10 degrees.
    Additional evaluation of planing amas, ama foil assist(curved and t-foil), dual crossarm mounted wands controlling ama foils AND main foil.
    The decision on whether to go ahead with this prototype will be made based on the test results.----

    Follow this thread: http://www.boatdesign.net/forums/mu...-self-righting-trimaran-test-model-36058.html
     

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  6. Doug Lord
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    Doug Lord Flight Ready

    Variations on the MPX theme

    The previous post 196(below) shows some of the possible variations with the MPX foil system but one wasn't mentioned: the use of a small ama and curved lifting foil which is 100% retractable.

     
  7. Doug Lord
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    Doug Lord Flight Ready

    MPX-12-How and why its different -and better

    There is much detail in this thread about this little boat and the unique system that makes it potentially a very fast small trimaran-much faster than all current designs I've seen.
    The most important single element in this design is the use of hydrofoils to control the sailing angle of the boat, provide incredible pitch stability and allow the main hull to take off in very light air-about 5 knots. Any small tri with this much beam and without these foils used in this manner would have too much RM to fly the main hull in less than 15 knots or so.
    Any small tri(12') with this much SA and not using foils would be a pitchpole waiting to happen.
    The MPX foil system can allow the sailing angle to be adjusted and can be used with different types of ama systems-from the experimental planing amas , to planing amas with foil assist, to small high L/B ratio hulls with foil assist ,to the same with full flying amas. In each case the ability of the boat to handle the power in both light air and heavy air is directly related to the bi-foil arrangement of the foils on the main hull and the altitude control system. They significantly improve the sailing characteristics of a small trimaran by allowing it to use the power of an over square platform in heavy air coupled with the tremendous advantage of flying the main hull very early in light air.
    There is simply nothing like it anywhere.....
    ------
    PS- if anyone knows of a design, at this length, that they think could potentially compete with the characteristics described above and be faster please
    let me know. I'm almost certainly going to build a prototype of this boat as soon as the fullsize version of the SRT/Trapwing is complete. It is being considered now to incorporate the MPX foil system on that hull for testing(and fun) but then I think a 12 footer incorporating what we've learned by then is called for. My enthusiasm for this design continues to grow.....

    new pictures-click on image and then again on resulting image for more detail:
     

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  8. Doug Lord
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    Doug Lord Flight Ready

    MPX-12-design/testing/problem solving

    The biggest problem with the MPX-12 system is the sailing angle of heel. While the wand equipped main foil will control that angle it will hurt windward performance without a good solution-at least from takeoff* to about 10-12 knots windspeed.
    The reason is that when the foil is lifting up while the boat is sailing at a 10 degree angle of heel a component of that lift is pulling the boat to leeward. The good news is that as the boat goes faster the lift on the main foil decreases until it reaches zero. At that point it is no longer hurting vmg to windward.
    There were two solutions previously mentioned for this problem:
    1) cant the daggerboard main foil 10 degrees so that the main foil is horizontal,
    2) pivot the main foil at the daggerboard/main foil joint.
    These will be tested on the model being built now(see link above). There may be another benefit that could be derived from either of the above solutions:
    the board/foil could be canted/pivoted 20 degrees to allow the lift developed by the main foil to have a component pulling the boat to weather.
    This would be similar to how "Veal Heel" works on monohull bi-foilers(like the Moth, R Class and Mirabaud) and could result in improved windward vmg.
    * Note that at take off the sailing angle could be adjusted below 10 degrees since it is easily adjustable. Crew weight just after takeoff may play a role since, for racing, the ama would not be immersed then (depending on crew weight and position).
    ---
    Leaving the board system fixed does not appear to be a viable way to go....
     
  9. Munter
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    Munter Amateur

  10. Doug Lord
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    Doug Lord Flight Ready

    Mpx-12

    =============
    Leeway is not the problem-as you claimed -the problem is the small component of lift to leeward generated by the main foil in a narrow range of wind and boat speeds when the system(incl. wand) is maintaining a specific sailing angle. The vertical fin and rudder generate all the lateral reistance required by this boat.
    The foil causes a very small problem in wind up to 10-12 knots windspeed(maximum)-above that there is no problem. In fact, when the main foil starts to pull down the system acts just like a bi-foiler with Veal Heel from the perspective of the main foils' contribution to upwind work. This is an effort to refine the system and perhaps improve it. The foil problem would be more important on a version of the system where the design sailing angle is greater than 10 degrees.

    PS-
    1) the first mention of the potential for a problem with the foil was mentioned in post #8 of this thread and several times thereafter including where the potential "fixes" were first proposed.
    2) as mentioned earlier the sailing angle of the boat is completely adjustable and in the lightest(takeoff wind) the angle could be adjusted down. In those conditions crew weight could be used to help reduce sailing angle. So even with no "fix" whatsoever the impact of the small component of mainfoil lift to leeward would be in a very small range of wind and boat speed.
    3) it is definitely worth considering a pivoting foil or canting daggerboard + foil because aside from fixing the foil lift problem to leeward, occuring in a very narrow range of wind and boat speed, the mainfoil can be reconfigured to have a small component of lift acting to reduce normal leeway thereby unloading the daggerboard, reducing drag and improving upwind vmg.
     
  11. Doug Lord
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    Doug Lord Flight Ready

    --------
    SOLUTION

    A light blinked on today that solves the above problem without any need for a canting daggerboard/foil combo or pivoting main foil:
    By using a properly designed curved lifting foil as part of the ama(planing or otherwise) the ama can be flown at the same time the main hull is designed to fly-(approx. 5-6mph wind). This will allow the main hull to be level which will eliminate any leeward component of lift from the main foil. Crew movement can be used to assist the curved foil during the period where the main foil is lifting between 60 and 80 % of the boats weight. As explained previously, the MPX theory uses two foils in a bi-foil arrangement on the main hull in order to allow the main hull to lift off in light air. Without the foils the main hull would not lift off until at least 15-20 knots of wind especially on a very wide(square or over square) trimaran.
    With the foils, early main hull takeoff is possible and, as speed builds, the main foils are unloaded(!) so that, at a certain apparent wind, the boat is supported 100% by the ama + curved foil. Pitch control of the whole boat is then the main function of the two main hull foils in addition to controlling sailing angle by lifting up or pulling down(via wand based altitude control). The ama's curved lifting foil can be designed so that, as speed picks up, it is retracted and/or the angle of incidence of the lifting portion of the foil is changed. The ama foil can be set up to be toed in so that the lateral resistance portion of the curved foil helps to unload the daggerboard/main foil combo from having to provide lateral resistance.
    ======
    IMPORTANT: at the point that the the mainfoil is nearly(meaning of "nearly" to be determined by testing) unloaded the flying angle can increase to 10 or more degrees since then the main foil has no net force vector to leeward. Whether using the "Devils Tail" planing ama or a "normal" very small ama the small curved lifting foil will play a major role in overcoming the initial loading of the main foil at take off and up to a 10-12 knot true wind-eliminating the leeward component of lift.
    The critical beauty of the curved foil is that its lift characteristics can be changed at will(by adjusting the angle of incidence and/or retracting a small or large amount) and the curve of the foil along with its area can be matched to the requirements above-not just on the MPX-12 but on any tri. The curved lifting foil can be designed to perform like a surface piercing foil whose altitude is controlled by speed during the period described above- between takeoff and the unloading of the main foil. With an assist by crew movement during this period, the foil can be designed to be very lightly loaded when performing this function. Later, as speed increases the foil would work in concert with some ama buoyancy and not be very susceptible to ventilation.
    Most small tri's are not designed to fly the main hull because the RM they generate is just too great requiring humongous SA to try to fly in light air. Light air is the predominant wind in the USA and so, in my opinion, flying the main hull is absolutely necessary if one is to approach the maximum performance possible with a small tri. Further, utilizing the MPX system allows the tri to be designed as a square or over-square platform adding power to carry sail in the strongest of wind. The MPX system, with the addition of the small curved foil to the ama, is a completely interrelated system where all components function together in light and heavy air to maximize the potential of a small high performance trimaran.
     
  12. Doug Lord
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    Doug Lord Flight Ready

    Mpx-12

    This is preliminary ama design for the Self-Righting Trimaran test model refered to in post 254 above. This type of ama will serve as backup for the planing ama should it's performance not meet expectations. In the sketch it is 10'LOA and .66' wide(8") and for the MPX-12 application would be reduced to approximately 7'LOA by .46' wide(5.5").
    This ama is not designed to be used in "normal" sailing-if it is used it will be backup for a curved foil designed to support the total boat weight at X speed with the main foil and rudder foil handling pitch and heave while essentially unloaded.
    This ,again, allows the main hull to fly way earlier(in lighter wind) than it otherwise would.


    click on image for more detail:
     

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  13. Doug Lord
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    Doug Lord Flight Ready

    MPX-12--- More philosophy:comfort

    The technical aspects of this boat are pretty awesome in many respects offering potential speed second to none in 12-14' trimarans-and the MPX "flight control system" is about to be tested on a 5' model. The boat will be light , easy to beach sail and above all fun like no other 12' tri currently sailing as best I can tell.
    But aside from all that stuff one thing really sets this thing apart: comfort. I'm 100% convinced that fast sailing does not have to require an athlete nor is it a requirement for high speed performance sailing that you hurt after a few hours on the water. It just seems to be the way it is and thats something this boat, I hope, will change. The fact is to sail this boat-whether you're heavy or light-you'll sit in an extremely comfortable sliding seat that won't have to be moved more than a couple of feet each side. As much thought is going to be put into achieving incredible comfort and ease of sailing as is being put into the development of the MPX flight control system.
    I believe that "comfort", I mean real comfort- can be engineered into a boat like this especially because of the other characteristics of the boat.
    When I build the proto, comfort will be an equal priority with exceptional high performance.

    follow the testing and development of the MPX system on the Self-righting Trimaran model here: http://www.boatdesign.net/forums/mu...elf-righting-trimaran-test-model-36058-5.html
     
  14. Doug Lord
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    Doug Lord Flight Ready

    MPX 12-High Performance Trimaran Technology

    I've just done more research on the net-looking to try to find another small trimaran with the power and potential of this one. The MPX technology as applied to small trimarans appears to offer a dramatic increase in the performance of these little boats. And, as best I can find, there is absolutely nothing on the market today that could compare to the technological advances represented on this little boat and its big sister the SRT. See the testing thread , noted above, for continuous updates on the test model. I'm encouraged that the field still seems wide open for a little hot rod like this that will be so remarkably easy to sail.

    PS- If anyone runs into a design-proposed or existing- that you think is similar to this boat in terms of power, speed or comfort please bring it to my attention. I would really appreciate any information that I may have missed...
     
    Last edited: Jul 17, 2011

  15. Doug Lord
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    Doug Lord Flight Ready

    MPX-12--angle of heel/powering up

    This is a possible change to the MPX-12-and it may be tested on the SRT model referenced above. A friend and I were discussing how the MPX system
    particularly on the 12 would behave in waves. The wand system is designed to control sailing angle to around 10 degrees but is adjustable. The main foil will lift the boat from the lightest air to 12-15 knots where it will essentially be
    unloaded except for its role in pitch control. A curved foil will be used as standard to make up for the slight leeward component of the main foil in this range-the foil will also reduced the required lifting area for the planing ama and help the ama in rough conditions.
    It occurred to be that in wind over-say 12knots, with waves that it might be beneficial to allow the sailing angle to increase to 15-20 degrees getting the main hull higher off the water preventing or significantly reducing wave interaction. The rig problem(loss of power) could be solved easily with a canting mast-very simple at this size boat. And the foil depth could be increased if necessary. Since the main foil is virtually unloaded at that windspeed there would be no increase in the leeward component of the main foil-in fact as speed increases the foil would begin to pull down which would cause a windward component to the main foil and that would tend to unload the lateral resistance portion of the curved foil, reducing drag. So everything looks ok, except for the ama.
    The ama is designed to plane and to be flat at a sailing angle of 10 degrees so if the sailing angle was increased to 15 or 20 degrees we have a problem.
    The solution my friend and I came up with was to build in a structurally strong pivot at the juncture between ama and "curved piece" allowing 5-10 degrees of easily adjusted movement. The curved foil trunk would move with the ama.
    I've got to give more thought to this and talk it over some more and see if it could(or should) be incorporated into the SRT test platform. Possible improvement in heavy conditions........?
     
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