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

    MPX-11 prototype model

    I have the three hulls of the model complete-now comes the hard part-finishing: sanding ,filling, sanding, filling, assembly and painting. The model will fold just like the real boat. Some changes to the original specs will be introduced to allow a one off to be built at a weight that is realistic while maintaining (or exceeding)the ratios in post #1.
    I can't afford to build the molds that would be required to meet the projected weight at the bottom of the first post-though I'm 100% convinced that that weight is realistic for a production version. And as I've had a chance to get more into the design of this speed machine I've come to the conclusion I'll probably build one down the line after some other stuff is finished-or maybe somebody else will.
    Model pictures will be posted here.....
     
  2. Doug Lord
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    Doug Lord Flight Ready

    MPX-11(12) -more on design

    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.
    These are the revised specs:

    MPX-11,no, no I mean 12 for the one off!

    Note #1: the MPX-11(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.
    --
    Note#2: The MPX-11(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 subsequent posts.

    --LOA-12'
    --LWL-12'
    --Main hull beam-5.17'
    --Main hull beam at the waterline 3' (correction 8/7/10)
    --L/B-mainhull at waterline-4/1(planing hull/planing threshold: 6.9knots. (correction 8/7/10)
    --Overall beam- 15.5'(14' cl ama to cl ama) updated 8/7/10
    --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
    --Weight-162.3lb all up,ready to fly minus crew updated 8/7/10
    -- Total sailing weight- 400lb
    --Max crew weight-237.7lb updated 8/7/10 ( 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(!)
    --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.
    --Sail Area- 155 sq.ft /23.5' mast length. Slightly taller than a scaled down A Class Cat. updated 8/4/10
    -- 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.
    -- 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= 45.65/1( updated and corrected 8/5/10 )
    -- W/SA= 2.58 (same as Moth w/Veal!) (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=69.8% updated 8/4/10 -(NOTE:Bethwaite says a planing hull with a ratio above 30% will plane upwind-see note below)
    --MAX RM-3360 ft.lb.+127.5lb. foil downforce updated 8/4/10
    --MAX HM(before reefing/depowering)-3487.5ft.lb updated 8/4/10
    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. gybing daggerboard like some dinghies and the Capricorn F18 Catamaran
    b. canting mast
    c. adding a rudder gantry like the Cherub, Moth, I-14, R-Class and others*
    -*particularly since the rudder is going to have a foil and we can't have too much pitch control. Increasing the distance between the main foil and rudder foil is seeming like a better idea all the time-though I never have liked them aesthetically.
    ===========
    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, 8/7/10: Beam to increase to 14' CL ama to cl ama, 15.5' 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. Weight increase 2.3lb.

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

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

    More later.....
    -------------------


    --SCP(sail carrying power)= the RM in ft.lbs divided by the distance in feet between the CE and CLR. To get Bethwaites ratio this number is then divided into the total weight in pounds.SCP/Total Weight- A ratio of 30% or better permits upwind planing.
     
    Last edited: Aug 7, 2010
  3. Doug Lord
    Joined: May 2009
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    Doug Lord Flight Ready

  4. Doug Lord
    Joined: May 2009
    Posts: 16,643
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    Location: Cocoa, Florida

    Doug Lord Flight Ready

    MPX-11(12) -more on design

    The changes to the boat to facillitate 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-(1.5 sq.ft. planform area)--------------3 sq.ft.
    Rudder foil-(1.3 sq.ft planform area)------------ 2.6 sq.ft.
    Vertical Fin/dggrbd(2' immersion)----------------2 sq.ft.
    Rudder----------------------------------------1.6 sq.ft.
    planing surface(ama)--------------------------2 sq.ft.
    ____________
    TOTAL WETTED SURFACE---------------------11.2 sq.ft.
    MXP-11(12) SA=155sq.ft.

    SA/ws= 155/11.2= 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-11(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 at takeoff. In this case the main foil loading is 242.4lb. of vertical lift( 161.6 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. pressure) where the the load is 221 lb. down force ( 147 lb. per sq.ft.).
    Summary:
    Max vertical lift: 242.4lb(161.6 lbs per sq.ft.)
    Max downforce: 221lb( 147lb 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 )

    --MPX-11(12)=
    a. Heavy=400/155= 2.58
    b. Lite= 280/155= 1.8

    ---------
    --Moth=
    a. Heavy= 246/86= 2.86
    b. Lite= 220/86 = 2.56
     
  5. Doug Lord
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    Doug Lord Flight Ready

    MPX-11(12)---design quandary

    Heres the problem: As designed with a 12'(3.66m) beam, CL to CL of the ama, the boat will sail at a 10 degree angle of heel with the lowest part of the main hull 6"(.15m)* off the (flat) water.
    However, if I increase the beam to 16'(4.88), CL to CL(5lb weight gain) of the ama, she'll fly at the same angle 12"(.3m) above the water.
    This would not affect anything else significantly.
    I don't want to go above 10 degrees AOH.
    If you have any constructive thoughts that could help me think this specific problem thru I'd appreciate it. The basic question is: Is it worth it to gain a nominal 6" of main hull altitude for an additional 4' of beam?

    * corrected, sorry.

    ------------------
    For consideration: The overall beam of Hydroptere is 1.35 times its length overall. The length of this boat including the rudder gantry but not the rudder is 14'(4.27m), 1.35 times 14= 18.9'(5.76m).........
    Not affected:
    1) tacking
    2) the folding system
    3) RM is not affected because of the design of the foil control system and would remain what it is with the narrower beam.
    Not affected significantly:
    1) weight (ready to sail incl crew from 400lb to 405)
    2) pitch control may be slightly improved.
    Affected:
    1) Cost of carbon tube-an increase of around $600US.
    -------------------
    DECISION-8/9/10- Beam increased 3' to 16.5 overall(15' cl ama to cl ama) . Boat to sail at 10 degree angle of heel with nominal clearance of 9" between main hull and flat water. This is from lowest point of angled main hull.Weight gain+ 3.18 lb. Spec sheet above NOT updated.
     
    Last edited: Aug 9, 2010
  6. Doug Lord
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    Doug Lord Flight Ready

    MPX-11(12)---design/sailing question

    I've mentioned earlier that a small boat like this is an ideal candidate to consider a canting mast. Its been done before on other dinghies.
    Well, I've come up with a system that would allow the rig AND daggerboard to be canted simultaneously with just one line. So if you were to use the system it would require adjusting the "cant" line each time you tack-would probably be left centered downwind. Canting the board(hydrofoil) would be very helpfull upwind where the 10 degree heel angle would cause a potential reduction in VMG .
    Remember this is supposed to be an easy to sail, comfortable and very fast little boat. Unlike most dinghies this size very little movement by the crew is required.
    So it seems to me that having the option to use or not use a system like this is in keeping with the spirit of the boat.
    What do you think about this specific system?
    =========
    DECISION-8/7/10-Mast Cant: There does not appear to be enough to gain to cant the mast back to +10 degrees(to windward 10 degrees with boat heeled to leeward 10 degrees.) And I'm convinced that the gain from leeward 10 degrees to vertical is a gain not worth the pain at this point. Down the line it would be relatively simple to experiment with and measure any increase in performance.
    ---
    DECISION-8/9/10-Board(foil) cant: See post 24
     
    Last edited: Aug 9, 2010
  7. Eralnd44
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    Eralnd44 Wanderer

    I have problems with language. I know this. Last seven posts are you and not another. Is this your answer and not understanded?

    It is that nobody cares.

    Eral
     
  8. Doug Lord
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    Doug Lord Flight Ready

    ===================
    It is a diary of a design from conception thru model and maybe a prototype. Thanks for your comment.
     
  9. Doug Lord
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    Doug Lord Flight Ready

    MPX-11(12) -more on design: possible canting board/foil solution

    Because this boat will be sailed at a more or less "normal" heel angle of 10 degrees(maintained automatically by the wand) the main hydrofoil will generate a small force to leeward negatively affecting the boat's ability upwind. This is unacceptable to me.
    So I have come up with a possible solution that will require some time to consider. The F 18 Capricorn uses "gybing" daggerboards to aid upwind-like several other monohull dinghies. I've wanted to incorporate this somehow. One way of accomplishing the same thing would be to cant the daggerboard/foil assembly in the same manner the Moth daggerboard/foil assembly is canted when the boat is sailed with veal heel. But on this boat that would involve a minimum of 40 degrees cant tack to tack because you start from the boat heeled "normally" 10 degrees.
    This is my idea: build a "vee" trunk into the boat that would be fitted with a cassette into which the daggerboard is mounted. The board/cassette assembly would cant 10 deg tack to tack and be able to be centered(horizontal, fore and aft axis). Inside the cassette the daggerboard/foil assembly would pivot around a vertical axis plus or minus 3 degrees or so(range adjustable)-a gybing board. The board/foil assembly would be vertical when canted under sail.
    The crew would have to manually 'cant' the cassette ,while the board/foil combo would probably automatically pivot. Probably is a big word and the problem is that the board/foil combo will have 200+ lbs load on it either up or down at different times. This makes the attachment of the board/foil combo to the cassette problematic-especially in light of the requirement for the board/foil combo to pivot within the cassette AND have a no-slack linkage to the wand.
    If the system can be worked out, the result would be an improvement upwind-more so on this boat than on a dinghy because the small force pushing to leeward would be gone as well.
    I basically like the idea but its going to take more thought to finalize it.....


    DECISION-8/9/10-I will definitely use this system. Have a tentative design solution that allows board/foil combo to cant 10 degrees, and the board/foil combo to gybe(adjustably) up to 3 degrees each side. Further, the system would allow the hydrofoil angle of incidence to be adjusted without interfereing with either the "cant" function or the "gybing" function. And the attachment of the mainfoil flap to the wand is not compromised in any way. The board is retractable by removing one pin. The system will work using a cassete within a cassette system. The trunk is designed with a "vee" shape so the board and cassettes will fit. The "major cassette" is attached with carbon pins to the trunk. This cassette is pulled from side to side by the crew unless and until an automatic "cant" system can be devised. The "major" cassette is wide enough to allow the 6" chord daggerboard + the "minor" cassette to pivot up to 3 degrees each side of the centerline automatically . It will allow this movement while under 200lbs load vertically,either up or down. Further, the "minor" cassette allows the board angle of incidence to be adjusted. The board is held in the boat by a single pin thru the "minor" cassette.The smaller("minor") cassette is attached to the larger cassette with a pin and two thrust bearings. Now, this sounds complicated when it is written out but when you consider what it does its not so bad. It eliminates the one negative affect of using a hydrofoil to control sailing angle: a small side force generated to leeward. However, the only boat to use a system remotely close to this one(the cat "Happy Feet") does not use such a system-probably because their foil pulls down more than it lifts up. At any rate this is a tentative way to proceed that solves the problem.....
     
  10. Doug Lord
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    Doug Lord Flight Ready

    MPX-11(12) -more on design: possible canting board/foil solution

    Another idea has surfaced that may have merit: The gybing board uses the force of the leeway itself to move the board to a + 3 degree position-and it does it automatically. This boat is unique in that it is using lifting hydrofoils that have to function while the boat is sailing with a 10 degree angle of heel.
    And that angle of heel produces a small force from the main foil(only when it is lifting vertically-when it is developing downforce it is ok at the 10 degree angle because the small force helps the boat go to weather).
    Now, what if there were a simple way to harness the power that pushes the vertical fin over from tack to tack to rotate the mainfoil 10 degrees? That would simplify the board system at the trunk a lot-eliminating the cassette and the "vee" trunk.
    It would require machining the t-foil hub to allow this to work. Basically, it could potentially work with a single rotating shaft coming down the foil or with one of two "piston" rods acting to move the main foil. There would be little or no load on the mainfoil resisting this movement.
    It might be too fragile-I don't know yet-just a possibility at this point.
    -----------

    DECISION-8/9/10- While this system(pivoting hydrofoil) holds some potential I will not pursue it any further at this time.




    Mirabaud's(26' monofoiler) "bulb"-Bulbs like this can allow simple foil changes as on Mirabaud or maybe facilitate the movement(pivot) of the main foil:



    (click on picture and then on the image that results)
     

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  11. Eralnd44
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    Eralnd44 Wanderer

    Now I am sad to have make a contribution to this topic.

    It goes nowhere.

    Please excuse me now.
     
  12. Doug Lord
    Joined: May 2009
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    Doug Lord Flight Ready

    =================
    Thanks for your "contribution(s)".
    --
    I'm sorry you feel that way. As I said earlier this is a diary of a design: I have described every system that this boat uses or might use in detail-mainly because their application to a boat like this is unique -and critical to its performance. I have described some problems I have run into and what their solutions are-at least the ones I've figured out so far.
    And last but not least I have presented more design detail than you are likely to find for any other boat presented on these forums. Because the boat-and the way it works-is so unique it is very important to do these detailed numbers now as part of the initial design: if the numbers don't add up then the boat won't work.
    This design has progressed almost daily with the changes to the original spec sheet clearly marked and a model of the prototype is being built as part of the development of the design.
    Because this boat uses technology in a way that it has never been done before on a small trimaran I have tried to explain everything in detail as the design matures. If there is something you don't understand don't hesitate to ask a question, but when you say this I think you are not reading the posts.
     
  13. Doug Lord
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    Doug Lord Flight Ready

    MPX-11(12) -more on design: summary of solutions

    Summary of recent design problems and their solutions:

    1) Beam, heel angle, post 20: Beam increased to 15' CL ama to CL ama(16.5' overall). Allows a nominal 9" clearance of main hull while permitting a sailing angle of heel of 10 degrees( maintained by wand). This can be adjusted ,if necessary, after testing. Also allows nominal 2" static clearance to lowest point of ama in flat water with boat level fore and aft and side to side.

    2) Mast "Cant", post 21: No mast cant initially.

    3) Hydrofoil Pivot, post 25: This would be done in lieu of canting the board/foil combination. Not to be pursued for now.

    4) Board/foil "Cant"/ gybing board, posts 21 & 24: Using this system: it eliminates negative side force generated by hydrofoil at a 10 degree angle of heel while permitting vertical fin to "gybe" and angle of incidence of hydrofoil to be adjusted. Allows board/foil combo to be retracted simply by removing one pin. See post 24 for more detail.
    ==============

    Next Spec Sheet update on page 3......
     
    Last edited: Aug 11, 2010
  14. Doug Lord
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    Doug Lord Flight Ready

    MPX-11(12) -more on design: wand(altitude control system)

    As mentioned throughout this thread, this boat uses a wand based "altitude control system" or more correctly,in this application, sailing angle control system or Flight Control System(FCS). The wand, as a surface sensor, was first used years ago on the "Mayfly" hydrofoil and most recently was re-invented by Dr. Sam Bradfield in an improved version used on his Rave and other boats including the new all carbon Osprey. John Illett, adapted Dr. Sams wand to the Moth hydrofoil in 2000 creating the first wand based automatic altitude control system for the Moth hydrofoil. Bradfield also developed the first planing wand around 1999 that was not adopted by the Moth guys until fairly recently in the form of "paddles".
    So back to this boat: the 11(12) will use two wands off the bow(at present) each installed at 10 degrees to the vertical. This allows only one wand to be in the water when the boat is at its normal flying height( sailing angle) and keeps the wand wake clear of the mainfoil and rudder.Flying height(sailing angle) is adjustable by varying the wand length.
    The wands work more like the RAVE system than the Moth system: the sailing angle is set which helps the boat to fly the main hull much earlier than it would otherwise. If the heeling moment were to exceed the righting moment the main hull would tend to lift. In this case the wand changes the flap angle on the main foil so that the foil pulls down adding to the righting moment-like the windward wand/foil on the Rave. The system will keep very accurate control of sailing angle regardless of wind speed or crew weight( from 5 knots wind up and 120-240lb crew weight to max pressure of approx. 1.8lb./sq.ft w/o reefing/depowering). It adds vertical lift or downforce instantaneously as the requirement is sensed by the wand.
    The dual wands operate off a common axle at the bow of the boat with shock cord used to hold the wand(s) against the water.
    ---
    See posts 2, 4, 5 & 7 for more on the theory and history of the FCS(Flight Control System).
     

  15. Doug Lord
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    Doug Lord Flight Ready

    MPX-11(12) -more on design

    ======================
    Will definitely use a version of this rig(with a single sheet/ see post # 9) but the following
    are being considered:
    1) Using jib boom/lower endplate as shown in the sketch of the Trapwing 15 from the design Challenge thread under "Sailboats". Rigged somewhat similarly to a typical RC sail jib except the pivot point of the boom is tied in to a traveller so that the leading edge of the jib is on the CL upwind.
    2) a version of a "balestron" rig(or swing rig in RC model parlance) where the pivot point of the jib boom is attached to a spar that is attached to the mast and pivots with a rotating mast. Keeps the same main/jib slot regardless of how much main is eased. Can be set up to allow the new spar to rotate slightly off the wind.
    =========
    I'm leaning toward #1 but would like to try #2 with the skinny square top jib at some point.

    rough sketch of jib pivot traveller:
     

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