MPX-11 Very Small High Power Trimaran

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

  1. Doug Lord
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    Doug Lord Flight Ready

    ===============
    The critical thing is NOT the increased area but the increased aspect ratio and possibly sweep. Our estimate is that it may take up to 2 sq.ft. per ama to achieve this. A very unique shape to the planing area is being considered based on the work of Eugene Clement(see pix). The estimate for increased weight on the prototype is 4lb total which has been been "deducted" from the original crew weight of 240lb. Some who actually read the material may recall that the 240lb. was used to give leeway for just such a purpose as this. The SA/ws ratio remains virtually the same and sailarea will increase about 15 sq.ft(down a bit today). The W/SA(weight in pounds divided by sail area in sq.ft. ) is much better-significantly better than the Moth or any other small sailboat and thats true even with a 236lb crew!
     

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  2. Doug Lord
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    Doug Lord Flight Ready

    MPX-12---design

    ============================
    There are solutions opening up for testing this new(or any new) planing configuration by making modular removable panels that can allow a number of bottom configurations to be tested. These can be tested with the powerboat mentioned before or with a "control surface" on one side of the boat and the experimental surface on the other side. The "control" surface would probably be relatively conservative,i.e., flat.
    IF Clements work can be applied to a planing surface like this there are big potential gains in efficiency and reduction of drag and planing area. For Clements system to work it is essential that the pitch(running angle) of the planing surface is controlled and that is one of the main advantages of the MPX-12 : the hydrofoils can precisely control the pitch of the boat if the system is designed properly. Further, roll stability is controlled by the foils as well. That means the ama
    operates virtually independently of any forces acting on it as a result of its movement thru the water. This can be a positive or negative but the design of the ama
    anticipates that the nature of this system is that the ama may go thru waves rather than over the top in certain conditions. The "wave piercing" design forward of the planing area should help make this more of a positive than a negative in terms of drag and overall boat performance.
    So, a lot of effort will go into evaluating the Clements system to try to determine if it is a worthwhile experiment during testing. The viability of Clements work in this application may be the single most important determinent of ama planing area and total drag at planing speeds.


    for more on the amas see posts 159 and 160 on page 11
     
  3. Doug Lord
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    Doug Lord Flight Ready

    MPX-12----design/ daggerboard

    ==================================

    I've decided to go forward with a "tilting" daggerboard that will improve windward performance at the same time it solves an intrinsic problem with a trimaran using a bi-foiler arrangement on the main hull. The bi-foiler arrangement is critical to the function of the MPX-12 in that it allows fairly precise control of the angle of heel of the boat, superb pitch control and very early takeoff of the main hull in light air. Early takeoff would not be possible w/o this system. Without early takeoff the wide beam on this boat would be impractical from a performance standpoint and this would be just another slow 12' trimaran.
    A downside to the multiple advantages of the two foils is that when the foil is lifting up(most,but not all of the time) it also creates a force pushing the boat to leeward. This has not been acceptable to me since I first realized it would happen and the tilting foil solves it 100% and goes further: it actually allows a net improvement in windward performance by acting to reduce leeway and unload the daggerboard.
    I'm working on a design for the board/foil system that will allow it to be as robust and effective as a "normal" T-foil equipped daggerboard. The system may include a method that allows automatic tilting of the hydrofoil as the crew changes position in a tack or gybe using the sliding seat to good effect for the motive power. It may also be possible to set the range of tilt.
    I may build a model of the board/foil combo to test it....
     
  4. Paul B

    Paul B Previous Member

    How will you "go forward" with it? Will you make an actual drawing of it? Will you build it?
     
  5. cardsinplay
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    cardsinplay da Vinci Group

    It's still an area increase, no matter how you cut it, Mr. Lord. An area increase that was not a part of the calcs that you said was, how did you put it; "in exactly the configuration it needs to be to meet my design goals."

    What is so difficult about addressing that comprehensively?

    What the rest of us see is that you messed this up and are trying to talk your way around it. Immediately, this calls into question any of your other calculations and it's more than reasonable to take that position because this is such an important part of the entire strategy of the boat's operation. You got this wrong and the whole thing then fails to function as repeatedly specified.

    If you are willing to say that the ama was all wrong, then what's the problem admitting that dozens of other calculations are also very wrong? Your penchant for lots of numbers has failed you in a very big way.
     
  6. Doug Lord
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    Doug Lord Flight Ready

    Version 5 and updates*-start 11/8/10

    MPX-12--FLASH TRItm featuring the "Devils Tail(tm)" ama*


    1. Version 1-top of page 1-estimated production specs.
    2. Version 2-top of page 2-one-off specifications reflecting higher weight of the one-off boat while maintaining ratios close to version 1. Refinement of some parameters as the design has progressed.
    3. Version 3-top of page 3-continued refinement.
    4. Version 4- page 10, post 138-continued refinement.
    5. Version 5- page 13, post 186- change to sail area and planing area of ama. Change to immersed area of daggerboard because of addition of tilting hydrofoil which reduces the required daggerboard area. Rudder area reduced.

    ---As stated previously IF this thing is built it will be done as a one off which means it will be heavier that the production(molded) estimate in post #1.
    A small conceptual model is being built now-pictures are now posted in this thread and on this page-more to come. Work on the model has been instrumental in helping to refine the one-off design.
    And,this is a hot little boat as you'll see in a while.......
    -------------------------

    Note #1: the MPX-12 uses planing hulls because at this size displacement hulls carrying this kind of weight can't be "skinny" enough to take advantage of the low resistance characteristics of a high L/B hull-particularly with the main hull. It may be possible to use a skinny (L/B 14/1 or higher) ama hull coupled with a hydrofoil but the SA/ws ratio would be adversely affect and the boat would be slower.
    --
    Note#2: The MPX-12 uses two lifting hydrofoils-one on the rudder and one on the main foil. These foils are critical to the function of the boat. The system they comprise will be called the Flight Control System(FCS) and its derivation and application is detailed in the first few posts of this thread. See the following for more info:

    =================================================
    The Theory behind the MPX-12(based on proven performance) : (added 10/1/10)
    1) The hydrofoils' principal job is pitch control. Pitch control is critical as is a well controlled heel angle for the planing ama to be effective and at the same time to be low to no drag in light air and minimal drag when planing at the most efficient planing angle which is 100% maintained by the hydrofoils(and adjustable as well).
    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 without the foils the thing wouldn't fly the main hull until over 15 knots of wind or so. 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-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. 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.


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

    -- LOA-12' 7" - changed 9/15/10
    -- LWL-12' 7" - changed 9/15/10
    -- Main hull beam-5.29'- changed 9/15/10
    -- Main hull beam at the waterline 3' (correction 8/7/10)
    -- L/B-mainhull at waterline-4.19/1(planing hull/planing threshold: 5.3knots-1.5 SLR / 7knots-2 SLR ) (change 9/15/10)
    -- 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-6'
    -- Ama beam- 1.5'(max and max at waterline)
    -- Ama L/B- 4/1(planing hull/planing threshold-4.89 knots(aspect ratio of planing surface varies between 2/1 and 1/1)
    -- Ama Buoyancy - 3.25 cu.ft/ 208lb / 53% of sailing weight / RM just due to buoyancy= 1560ft.lb.(HM in 10 knot breeze=960 ft.lb)
    -- Sail Area- 178 sq.ft /25.5' mast length. Slightly taller than a scaled down A Class Cat. updated 8/19/10
    -- Main foil planform area-1.9 sq.ft.updated 8/19/10
    -- Daggerboard immersed planform area(boat @ 10 degrees)- 1.05 sq.ft.(coupled with tilting main foil for lateral resistance)
    -- Rudder hydrofoil immersed planform area(boat @ 10 degrees) - .8 sq.ft.
    -- Rudder immersed area-1.3 sq.ft.
    -- Draft(max) -3.5'
    -- Draft @ 10 degrees -2.2'
    -- Weight-159lb all up,ready to fly minus crew updated 8/13/10(Compare with the Baigent designed "Flash Harry 19.7' by 19.7' with 190+ sq.ft on a wingmast at 150lb! Post #104 this thread)
    -- Total sailing weight(displacement)- 395lb- updated and corrected 8/19/10
    -- Max crew weight-236lb updated 11/8/10 ( note this gives a little wiggle room for hull weight)
    -- Minimum crew weight(at max power)-120lb (boat can sail in same windstrength with minimum or maximum crew weight(!)
    -- Max Mainfoil loading - 157.5 lb/sq.ft. in .3lb wind pressure @ takeoff @ 80% total load. NOTE: this is LESS mainfoil loading than a Moth with Veal(very light) updated and corrected 8/19/10---Loading DECREASES as speed increases.
    -- Wand- altitude control system used in combination with the lifting hydrofoils on the daggerboard and rudder. Can be used to control sailing heel angle and compensate for different crew weights. Allows the boat to fly the main hull much earlier than it otherwise would.
    -- Max Pressure/w/o reefing 1.8 lb/sq.ft( 1.8 for F18 and 18 tri) The boat should be reefed(or the sail twisted off) in these conditions to prevent potential structural damage. After testing a warning label similar to the one installed in the Rave cockpit would probably refer to max speed or max apparent wind.
    -- 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) updated 8/4/10
    -- SA/D= 47.47/1( updated 8/13/10 )
    -- W/SA= 2.42 (236lb crew-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)-updated 8/13/10
    -- SCP/total weight*= 72.9% updated 8/13/10 -see note below
    -- MAX RM-3402 ft.lb.+(60lb. foil downforce X 7.5)=3852 ft.lb.( 1.7 times the super high powered 12' skiff) updated and corrected 11/10/10
    -- MAX HM(before reefing/depowering)-3852ft.lb updated 11/10/10
    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.
    --- See Wand above: this boat uses just two lifting hydrofoils which are critical to its operation.
    ---Ideas under consideration:
    a. jib pivot point traveler( see bottom of page 2)
    b. small "ballestron"/rotating whole rig with "ribbon square top jib"( see bottom of page 2)
    c. "mini ama foils"-see post #34

    These are all targets albeit very realistic targets and the potential is just flat wild.



    ===========
    Change, 8/4/10: Definitely will add 2' gantry to boat. Will be adjustable in overhang and facillitate rudder hydrofoil angle of incidence change.

    Change, 8/13/10: Beam to increase to 15' CL ama to cl ama, 16.5' overall all. Allows nominal 9" clearance of main hull at a 10 degree angle of heel with amas at a 10 degree cant(bottom outboard with boat vertical). RM does NOT change.

    Change, 8/13/10: Boat to use gybing/canting daggerboard +mainfoil. Eliminates leeward component of hydrofoil at designed sailing angle of 10 degrees. Gybing board(F18 Capricorn and several dinghies) improves windward performance. As noted above the boat uses a sliding seat that moves a maximum of 2' and can be used to move the canting/gybing board from tack to tack(8/19/10)

    Change , 9/15/10: Seven inches added to overall length. Main hull beam slightly increased.

    Change , 9/19/10: Angle of cross arms changed for model and prototype. Angle of ama increased 3.6 degrees on model only(probably).This will change set angle of heel of boat as set by the wand if it is maintained for prototype.


    Change,11/8/10: Planing area of ama (at 15 knots) to be approximately doubled with a substantial change in aspect ratio from 1/1 to 3/1(three times as wide as the F&A dimension if achievable) Note: again, only affects the wetted area for planing starting at 15knots boat speed.
    Note: no significant change in weight anticipated, though with the extra SA more weight can be carried. Approximately 2 sq' may be added per ama ,though the important change is that of aspect ratio. If the full two sq' per ama were added weight increase would be about 4 lb which will show up as a reduction in crew weight so total all up sailing weight will not change.

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

    More Power, Much more Comfortable, Much easier to sail than ANY similarly powered up 12' boat!

    --More Power: more sail area than almost any current 12' trimaran. Much more beam and power to carry sail than any 12' trimaran-in fact more than any 12' sailboat period. The only 12' design I know of capable of automatically adding righting moment as it is needed and which maintains maximum righting moment regardless of crew weight in the range of 120 to 240 pounds. Usable power: the only 12' trimaran design that matches the numbers for the Moth in Power to Weight(W/SA) and Sail Area to Wetted Surface ratios.

    --Much more comfortable: sumptuous seating with 3" cushions w/backrests-nothing like it in any current boat with this much power at this length. Seats slide easily up to 2' athwartship.

    --Much easier to sail: the design of the boat limits required crew movement to 2'-no running across a tramp-just a small cockpit. No hiking or trapezing required. Much less physically demanding than any other small boat with this much sail area. Sheet leads from forward-not aft like on some cats. Amas fold for easy and quick transport. Easy to reduce sail area(or increase sail area).Daggerboard and rudder(and ama foils,if used) retract for beach launching. Weta type dolly(SC version)-the best I've seen for a small tri. Gantry(extension that holds rudder) retracts to shorten overall length.
    Difficult to capsize or pitchpole but will have a simple righting system in that event. Buoyancy at masthead will prevent turning turtle.
    updated 9/24/10



    More later.....

    *Devils Tail was from a comment by Gary Baigent in post # 40
    -------------------
    --*SCP(sail carrying power)= the RM in ft.lbs divided by the distance in feet between the CE and CLR.
    SCP/total weight-To get Bethwaites ratio SCP is then divided by the total weight in pounds.SCP/Total Weight- A ratio of 30% or better permits upwind planing.
    IMPORTANT NOTE: this ratio was mis-written and has been corrected as of 10/1/10. The word "into" was somehow substituted for the word "by" in the formula-my humble apologies!


    Previous Revision of this page complete 10pm, 8/19/10 .

    +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
    ===========================================================================================
    +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

    Important Stats-see below

    This is an update of post 19,p2 reflecting the changes to the specifications:


    The changes to the boat to facilitate a one off(and on which the model is based) shown in the post above reflect a very high SA/ws and a low W/SA.
    A) The Sail Area/wetted surface ratio:
    --
    Wetted Surface, main hull flying-------------
    --
    Main foil-(1.9 sq.ft. planform area)--------------3.8 sq.ft.
    Rudder foil-(.8 sq.ft planform area)--------------1.6 sq.ft.
    Vertical Fin/dggrbd(1.76' immersion)------------ 2.1 sq.ft.
    Rudder----------------------------------------1.4 sq.ft.
    planing surface(ama)approx. as of 11/8/10------4 sq.ft.
    ____________
    TOTAL WETTED SURFACE---------------------12.90sq.ft.
    MXP-11(12) SA=178sq.ft.

    SA/ws= 178/12.90= 13.8/1


    ---------------------------------------
    Comparison to Moth:
    --------------
    Main foil (planform area 1.1 sq.ft.)-------------2.2 sq.ft.
    Rudder foil( planform area .88 sq.ft.)-----------1.76 sq.ft.
    Vertical Fin/dggrbd(18" immersion)-------------1.17 sq.ft.
    Rudder---------------------------------------1.17sq.ft.
    _________
    TOTAL WETTED SURFACE-------------------- 6.3 sq.ft.
    Moth SA= 86 sq.ft.

    SA/ws-86/6.3= 13.65/1

    =====================================

    B) Main foil loading(assuming that the main foil supports 80% of the weight/load). On the MPX-12 the foil lifts both up and down.

    ---Because of the nature of the foil system on this boat the highest foil loading occurs in the lightest air(.3lb. per sq.ft. wind pressure) at takeoff. In this case the main foil loading is 252lb. of vertical lift( 157.5 lbs. per sq.ft. main foil area).
    The next highest loading is with the minimum weight crew in maximum conditions(1.8lb. per sq.ft. SA pressure) where the the load is 187 lb. down force ( 116.8 lb. per sq.ft. main foil area).
    Summary:
    Heavy Crew-Max vertical lift: 252lb(157.5 lbs per sq.ft.)
    Lite Crew-Max downforce: 187lb( 116.8 lbs per sq.ft.)
    ----------------

    ---Comparison to a Moth(vertical lift only-main foil @ 80% only) :
    Lite crew(154lb)=160 lb/per sq.ft.
    Heavy crew(180lb)=178.9 lb. per sq.ft.
    ===========================
    C) W/SA=weight in pounds divided by sail area in sq.ft.( sail loading-smaller=better )

    --MPX-12=all revised:
    a. Heavy=395/178= 2.22
    b. Lite= 275/178= 1.54

    ---------
    --Moth=
    a. Heavy= 246/86= 2.86
    b. Lite= 220/86 = 2.56

    ==========================================================
    ==========================================================
    Interesting A Class & C Class Cat comparisons with Moth and MPX-12--ALL WITH 175 lb* crew:
    *(2 X 175lb. for C Class)

    1) W/SA(weight in pounds divided by sail area in sq.ft.) smaller better :
    a. Moth(66+175=241lb) 241/86= 2.8
    b. A Class Cat( 150+175= 325) 325/150= 2.16
    c. MPX-12( 155+175= 330) 330/178= 1.85
    d. C Class Cat(approx.)-680/300= 2.27


    2) SA/WS(sail area in sq.ft. divided by wetted surface in sq.ft.)
    Note: A Class calculated with one board, one rudder and flying one hull. In addition 10% of its wetted surface is deducted to account for lift from the new curved boards.

    A) FLYING: (higher=better)
    a. Moth(from above) SA/ws= 13.65/1
    b. A Class Cat(wetted surface=21.53 sq.ft) SA/ws= 6.96/1(corrected)
    c. MPX-12(from above) SA/ws= 13.8/1
    d. C Class Cat (wetted surface incl 1 board,1 rudder=35.63sq.ft./approx.) SA/ws= 8.42/1

    B) NOT FLYING : (higher=better)
    a. Moth- SA/ws= 3.51/1
    b. A Class- SA/ws= 5.56/1
    c. MPX-12- SA/ws= 6.73/1
    d. C Class Cat(approx.)- SA/ws= 7.5/1


    ====================================
    *page updated and corrected 8/19/10 Updated 9/28/10,
    page updated 10/8/10
    ----

    Gino Morrelli(famed multihull designer with Morrelli and Melvin):
    "Foils are definitely the way to go: it's an instant turbo".

    ----

    Images with modified ama geometry to be added later.....

    foil areas and SA/ws corrected 11/14/10
    Note: modifications to this page will not be complete for a few days and updates may be added at any time-11/8/10
     
    Last edited: Nov 14, 2010
  7. cardsinplay
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    cardsinplay da Vinci Group

    You just have to know this in your heart, Doug; that this ongoing, posted-every-day list thing you do has become an albatross hanging around your neck. It could be informative and inviting because of its simplicity and ease of read. Instead, it is a behemoth chunk of Internet wall paper. Please do yourself and everyone here a favor and pare that dirge down to a simple melody, or get rid of it altogether.
     
  8. NoEyeDeer
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    NoEyeDeer Senior Member

    I'm glad to hear that you now have an actual boat using this setup. Please post pix. Kthnx. :)
     
  9. Doug Lord
    Joined: May 2009
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    Doug Lord Flight Ready

    Mpx-12

    =============
    Thanks for your comment. Much appreciated.

    (click on image and then on resulting image)
     

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  10. NoEyeDeer
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    NoEyeDeer Senior Member

    That is not an actual boat. :) A nice video of the boat using the two foils which are critical to its operation would be more convincing. I'm sure you are capable of providing such a thing.
     
  11. Doug Lord
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    Doug Lord Flight Ready

    Mpx-12

    -------------------------------
    Oh? Coulda fooled me..... Oh yeah: thank you for your comment(s). Much appreciated.
     
  12. Doug Lord
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    Doug Lord Flight Ready

    MPX-12-----Design

    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.
     
  13. Doug Lord
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    Doug Lord Flight Ready

    MPX-12----design comparisons

    Just for the heck of it today I figured up the maximum RM for the exciting ,powered up 12' skiffs. Well, with two 170 pounders on trapezes the RM of a 12' Skiff is 2244 ft. lbs. Thats max unless, of course, a heavier crew sails the boat. The Skiff has a 28' mast and their sail areas aren't published(anywhere I can find them so far) but they have three rigs-light air, medium air and heavy air. Of all the boats I've been able to find information on these boats are the most powered up of all 12 footers anywhere in the world-mono or multi.
    Now, the MPX-12, with the foil adding a small amount of RM, has 1.72 times this righting moment-3852ft.lb.! In otherwords: no other currently produced 12 footer mono-or multi- can match the MPX-12 preliminary design for power to carry sail*.


    *One possible exception is the Cherub Banshee trimaran version for which I can find no info. Apparently it has 166 sq.ft. of SA.
    http://www.boatdesign.net/forums/mu...l-tri-s-10-14-why-not-33417-8.html#post386079

    UPDATE: estimated max RM of Banshee tri 2680ft.lb but, after all, it says "fast cruising trimaran" right on the plans......
     
  14. Doug Lord
    Joined: May 2009
    Posts: 16,555
    Likes: 295, Points: 93, Legacy Rep: 1362
    Location: Cocoa, Florida

    Doug Lord Flight Ready

    MPX Foil System

    Below is the original post about Arnie Duckworths Happy Feet with the bi-foiler "pod" that can slide athwartship.
    I neglected to mention a little known trimaran by Kotaro Horiuchi -a major hydrofoil pioneer. His system is actually closer to my MPX system than is Happy Feet as it uses a surface sensor and two foils on the main hull. Not much is known about Horiuchi's tri but it is definitely good looking and with his track record probably performs very well.
    Both these boats and the Rave(and my F3) were major inspirations for my work on the MPX system and MPX-12 in particular.


     

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  15. Doug Lord
    Joined: May 2009
    Posts: 16,555
    Likes: 295, Points: 93, Legacy Rep: 1362
    Location: Cocoa, Florida

    Doug Lord Flight Ready

    Ama buoyancy

    I'm convinced that the buoyancy of the ama is important to make this tri forgiving and easy to handle in certain circumstances.
    The system to change the running angle(of attack) of the ama is not complex but once the right position is found only minor adjustments will have to be made and the angle of incidence adjustment of the main foil and rudder foil will take care of it.
    The potential of high top end speed is part of this design since the main foils unload as they go faster and the planing surface shrinks as it goes faster without any unwanted changes in attitude as a direct result of the speed.
    But in tacking it will be a good thing to have good old fashion buoyancy to prevent a capsize.
     
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