MPX-11 Very Small High Power Trimaran

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

  1. Eralnd44
    Joined: Oct 2006
    Posts: 68
    Likes: 2, Points: 0, Legacy Rep: -38
    Location: Eurohut

    Eralnd44 Wanderer

    mr. doug make to much for parts on flashingtri. maybe mr. doug have romantic place in head for many parts and hard as to say goobye on way he think.

    good story to know and maybe not good boat. not safe in boat in story.
     
    Last edited: Oct 1, 2010
  2. CutOnce

    CutOnce Previous Member

    Mr. Lord:

    Given your main foil is directly controlled by a single wand, how do you plan to make it symmetrical on both tacks? Placing it on centerline would exacerbate wand induced foil ventilation.

    Given you are specifying a gybing daggerboard, how do you plan to handle the angular movement of the board in regards to the wand linkage? All field results to date suggest that zero slop in the wand linkage is an important factor in controllable foiling.

    Given you are specifying a canting daggerboard, the same issues as above apply - how do you expect to avoid inducing slop into the control linkage as a result of the moving board?

    If you are planning to solve the two above problems with a bicycle-style bendable linkage casing of fixed length, how do you plan to assure enough reduction of friction to make the system responsive enough for the application? Bicycles basically are a pull-only system with return handled by spring tension, but you are specifying a bi-directional push/pull system as it has to work for both up and down force generation. At 30 miles per hour and a 14 foot wavelength, you would be expecting this type of system to deal with 3.2 hertz peak to peak frequency (cycles per second) on a regular basis.

    Given you have specified a bi-directional foil which can be used for both lift and downforce, how do you deal with the wand putting the foil in it's highest drag / highest lift configuration while the boat is in sub-foiling mode? This would seem to increase the speed necessary for take off. Basically, you are designing for highest foil drag at the worst possible time (as do Moths and others).

    It would seem you would need a very heavy wand tip to maintain a negative lift control position when to boat exceeds your maximum allowable ride height. Maintaining a negative lift angle of attack on the main foil will require a lot of input from the wand, as the foil will naturally tend towards neutral "no lift" position due to hydrodynamic pressures How do you see this conflict of forces being resolved? Very heavy wand tips certainly exacerbate the problem with inducing foil ventilation. In the real world, I could see the water flow across the foil forcing the wand to remain neutral (effectively lifting it clear of the water once the maximum ride height was exceeded. This would negate your increased righting moment potential.

    In principle, building a much lighter (20-30%), much more expensive small trimaran on the scale of a Weta is do-able - as is foiling just about anything, given enough power and righting moment. So although I can see the technical possibility of your concept working, I do think there are lots of serious issues to be solved in the real world, instead of by using a calculator and formulas. Let me join the chorus of folks suggesting you actually build the boat in the real world. Light weight on this order comes at the expense of reliability - as so capably demonstrated at the recent ICCC event.

    In the real world, your problems are best solved by decoupling the mechanical inputs from the control systems and using an electronics-based brain to drive electrically powered control systems. This approach makes it far easier to resolve the problems outlined above - but it does raise the question "Is it still a sailboat?" if it requires electrically (or hydraulically) powered control systems. Completely mechanical feedback loop control systems have significant limitations in their applications to complex problems.

    I'd love to see it working, and solving the problems above (in actuality, not theory) would be a coup worthy of serious respect. Given the cost-no-object nature of your approach, I could see this working, but far too expensive to ever become more than a one-off exercise.

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

    Doug Lord Flight Ready

    Mr. Lord:

    1)Given your main foil is directly controlled by a single wand, how do you plan to make it symmetrical on both tacks? Placing it on centerline would exacerbate wand induced foil ventilation. At this point I'd probably use dual wands though a centerline wand would work with a canting main foil though it might interfere with the rudder.Also, a wand off the back end of the boat is not excluded so far. One thing: I've worked with wands for many years full size and with models. The wand location is not finalized at this point.

    2)Given you are specifying a gybing daggerboard, how do you plan to handle the angular movement of the board in regards to the wand linkage? All field results to date suggest that zero slop in the wand linkage is an important factor in controllable foiling. I'm not sure but I've had a lot of experience with wand linkages and solving complex linkage problems having designed and patented a video piloted helicopter in the 80's-and many other complex linkage problems since. This has not been addressed yet but I'm completely confident in being able to work it out. The degree of canting of the board and whether or not the board will gybe is not finalized. Because the angles will be small a flexible cable will probably work-but I haven't gotten that far yet. It does not seem like a major problem. The Rave sails with two foil positions and my first full size foiler had two foil positions as well-a flex cable can work wonders if it is done right. I know how to do it both ways-wrong and right- thanks to my experience with models, my first foiler and the Rave.

    3)Given you are specifying a canting daggerboard, the same issues as above apply - how do you expect to avoid inducing slop into the control linkage as a result of the moving board? see above

    ----
    If you are planning to solve the two above problems with a bicycle-style bendable linkage casing of fixed length, how do you plan to assure enough reduction of friction to make the system responsive enough for the application? Bicycles basically are a pull-only system with return handled by spring tension, but you are specifying a bi-directional push/pull system as it has to work for both up and down force generation. At 30 miles per hour and a 14 foot wavelength, you would be expecting this type of system to deal with 3.2 hertz peak to peak frequency (cycles per second) on a regular basis.
    ----

    4) Given you have specified a bi-directional foil which can be used for both lift and downforce, how do you deal with the wand putting the foil in it's highest drag / highest lift configuration while the boat is in sub-foiling mode? This would seem to increase the speed necessary for take off. Basically, you are designing for highest foil drag at the worst possible time (as do Moths and others). The boat is designed to take off in very light wind-around 5 knots-and the key to speed is getting on foils-as soon as the boat lifts off the drag goes way down. This foil system continues to UNLOAD the faster it goes as well....All foilers with fully submerged foils and an altitude control system operate at a high Cl at or just before takeoff.

    5) It would seem you would need a very heavy wand tip to maintain a negative lift control position when to boat exceeds your maximum allowable ride height. Maintaining a negative lift angle of attack on the main foil will require a lot of input from the wand, as the foil will naturally tend towards neutral "no lift" position due to hydrodynamic pressures How do you see this conflict of forces being resolved? Very heavy wand tips certainly exacerbate the problem with inducing foil ventilation. In the real world, I could see the water flow across the foil forcing the wand to remain neutral (effectively lifting it clear of the water once the maximum ride height was exceeded. This would negate your increased righting moment potential. Thats not how it works-this will be a system similar to a Rave(which I have sailed a lot and which generates "downforce" with windward foil even with a +2.5 degrees angle of incidence)) except that the foil may not be symmetrical(not determined yet). The Rave system and my system on the F3 used an adjustable application of force on the wand-but generally the only time extra force was applied was in chop to increase the speed of response-not necessarily the force. I will experiment with manual control where the wand can be "turned off" as have many different foilers. But I think the automatic wand system will be the best. By "very heavy wand tips" are you referring to the planing wands that have a wide flat tip? That concept was invented by Dr. Sam Bradfield and does not require more force to work. He did this 10 years before the first Moth did.

    6) In principle, building a much lighter (20-30%) (see #8 below-and post 104 ), much more expensive small trimaran on the scale of a Weta is do-able - as is foiling just about anything, given enough power and righting moment. So although I can see the technical possibility of your concept working, I do think there are lots of serious issues to be solved in the real world, instead of by using a calculator and formulas. Let me join the chorus of folks suggesting you actually build the boat in the real world. Light weight on this order comes at the expense of reliability - as so capably demonstrated at the recent ICCC event. Well, I haven't finished the design yet but it is looking very good and may well be worth building a prototype. There is no other tri design anywhere ,as best I can tell, that makes use of the technology that this boat does. It is basically all simple stuff that has been used separately on numerous different boats but is combined in a unique way here. I'm afraid that, so far, I see no "serious issues"-based on 50+ years experience in sailing and design and close to twenty years in foil design and experimentation.

    7) In the real world, your problems are best solved by decoupling the mechanical inputs from the control systems and using an electronics-based brain to drive electrically powered control systems. This approach makes it far easier to resolve the problems outlined above - but it does raise the question "Is it still a sailboat?" if it requires electrically (or hydraulically) powered control systems. Completely mechanical feedback loop control systems have significant limitations in their applications to complex problems.
    In principle,I'm not opposed to this at all and will probably experiment with electronics a lot. I don't have an electro-phobia and believe that electronic control systems for small boats can be made to be very reliable. Of course, thirty years of radio control design and experimentation helps.

    8) I'd love to see it working, and solving the problems above (in actuality, not theory*) would be a coup worthy of serious respect. Given the cost-no-object nature of your approach, I could see this working, but far too expensive to ever become more than a one-off exercise. I completely disagree with your last sentence-far too little work has been done to jump to that conclusion with this boat and far too much work has been done with the basic systems to arbitrarily classify them as "far too expensive". You should also realize that 155lb** for a 12' tri is not ultra light by any means-and the max crew weight of 240 lbs. gives lots of "real world" leeway. The degree to which this boat can or can't be done cost effectively for production is impossible for you (or anyone else) to determine with the information you now have.
    Thanks for your comments-I appreciate them. Doug

    --
    CutOnce

    * Which definition of "theory" are you referring to:
    1) a compendium of ideas that need "proving",or
    2) a compendium of proven systems organized in a way such that an "expert"
    in the field could reliably predict the outcome?


    ----
    **again, see post 104


    pix: dual wands on Mirabaud and a Moth: (click on image)
     

    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

    MPX-12-----Disassembled for transport

    Notice that the gantry is fully retracted. This is just one method of transport-the boat will also fold quickly and easily:

    (click on image and then on resulting image)
     

    Attached Files:

  5. Eralnd44
    Joined: Oct 2006
    Posts: 68
    Likes: 2, Points: 0, Legacy Rep: -38
    Location: Eurohut

    Eralnd44 Wanderer

    mr. doug have a shy style to talk on this flashingtri. boat will hover and spin in air for trailer mount to go. sailor must only to think and boat does so. mr. doug to make model and foto soon.

    magic like the fairies in fable. like smoke in wind.
     
  6. Doug Lord
    Joined: May 2009
    Posts: 16,679
    Likes: 346, Points: 93, Legacy Rep: 1362
    Location: Cocoa, Florida

    Doug Lord Flight Ready

    MPX-12---gantry

    To illustrate better how the gantry works here are a couple more pictures:


    (click on image and then again on resulting image)
     

    Attached Files:

  7. Eralnd44
    Joined: Oct 2006
    Posts: 68
    Likes: 2, Points: 0, Legacy Rep: -38
    Location: Eurohut

    Eralnd44 Wanderer

    is more weight. is more part to not work since dirt also salt make to stick.

    why to many flashingtri parts mr. doug. simple all time is best. not so much as to breaking. make flashingtri on so many parts and to make boat easy to not working. big problem and not to go away. i not happy to make fix as to sail.
     
  8. Eralnd44
    Joined: Oct 2006
    Posts: 68
    Likes: 2, Points: 0, Legacy Rep: -38
    Location: Eurohut

    Eralnd44 Wanderer

    is still bad point for ama. no need for point. make danger to sailor. make danger on to other boat since begin design try.
     
  9. Doug Lord
    Joined: May 2009
    Posts: 16,679
    Likes: 346, Points: 93, Legacy Rep: 1362
    Location: Cocoa, Florida

    Doug Lord Flight Ready

    MPX-12---Main hull detail

    Main hull alone:

    (click on image and then again on resulting image)
     

    Attached Files:

  10. CutOnce

    CutOnce Previous Member

    How about a happy MPX-12 mascot?

    Could not resist making a happy mascot from one of the images! The mascot just jumped off the screen for me.

    The model pictures provided (even without the amas) hint at a pretty complex shape and female mold tooling. Do you intend to build molds before prototyping?

    Also, the aka attachment points are quite a bit inward of the max beam on the after crossbeam. Why not use the width available for structural support, and simplify the design? Was your decision based on engineering criteria or aesthetics?

    --
    CutOnce
     

    Attached Files:

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

    Doug Lord Flight Ready

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

    Gee, thanks for the picture-its cute and a little friendly.... Some shapes will be built from quickie tooling-if a prototype is built.
    Seems pretty simple and strong enough as is.Yes. But I will consider this as time goes on...
     
  12. Eralnd44
    Joined: Oct 2006
    Posts: 68
    Likes: 2, Points: 0, Legacy Rep: -38
    Location: Eurohut

    Eralnd44 Wanderer

    mr. doug is to make trappingwing then to flashingtri maybe. Long time wait for trappingwing now. since more than year.

    mr. doug say once as trappingwing most imoprtant project as i see to old post here. now curious why project becomes dead.

    why dead trappingwing mr. doug.

    how to make no point of danger with flashingtri ama. stab other sailor. maybe stab sailor for flashingtri when crashes. why important to make stab point as to other shape not for big danger.

    mr. cutonce face is happy in sky. you make fun post.

    mr. doug how to make quickie tooling as you say. make boat red there also as to red trappingwing. so big as to red. why not to use next color. can be confused as to red trappingwing and red flashingtri.

    So as to look for spear and to stab sailor who make a crash and go to front of boat on water. important as to stab sailor so normal ama have no work as to this style. :p

    blood business for flashingtri maybe.
     
  13. Munter
    Joined: Jul 2007
    Posts: 285
    Likes: 11, Points: 18, Legacy Rep: 125
    Location: Australia

    Munter Amateur

    Apparently happiest upside down.

    In case it isn't clear. Doug is not here for feedback, he's here for recognition of his design talent. That is how he can knock back a comment on a simple structural improvement with the response "it's fine as it is"
     
  14. Cheesy
    Joined: Aug 2008
    Posts: 315
    Likes: 12, Points: 0, Legacy Rep: 189
    Location: NZ

    Cheesy Senior Member

    maybe a silly idea but wouldnt it be a lot easier to use a pair of the surface running foils instead of the devil tail amas, you could always have a more conventional ama above the foil to add some bouancy when its needed, it would be significantly easier to change a foil position than tweak the centre of lift of the amas.....
     

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

    Doug Lord Flight Ready

    ====================
    Its not a silly idea-there are a few tri's already in existence with surface piercing(is that what you meant by "surface running"?) foils instead of/or along with an ama. See post 34 for the idea of using very small retractable T-foils with each ama-probably for rough conditions.
    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.
     
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.