High Performance MPX Foil/Self-righting Trimaran-The Test Model

Discussion in 'Multihulls' started by Doug Lord, Dec 28, 2010.

  1. Doug Lord
    Joined: May 2009
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    Location: Cocoa, Florida

    Doug Lord Flight Ready

    MPX Test Model

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    Thanks. My gut feeling is the easier it turns the better. I'm not concerned(at this point) with any structural problem. Appreciate the info.
     
  2. Doug Lord
    Joined: May 2009
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    Location: Cocoa, Florida

    Doug Lord Flight Ready

    MPX Test Model-Gaff Control Device(GCD)

    ----------------------------
    See the original illustrations below. I should have pictures of this device rigged
    to the gaff tomorrow. I'm not 100% sure it has any value but it sure has an effect on the gaff depending on the setting: tightening the gaff control line("peak halyard") as the gaff swings to the side. It doesn't seem to require as much movement of the GCD as I'd thought might be necessary but the full range is available.
     

    Attached Files:

  3. Baltic Bandit

    Baltic Bandit Previous Member

    Why go through this complexity and not be able to adjust it dynamically? seems to me a simpler solution would have been to simply extend the mast a bit (essentially what you have done) and run the gaff tension line down the mast to a fairlead and then to a servo. That way you could have been able to control the gaff tension on the fly and actually experiment with the performance changes of different tuning

    as you have it built, it looks like you can only adjust it statically from the shore which means you won't have repeatable runs
     
  4. PerthMini40man
    Joined: Jan 2014
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    Location: Australia

    PerthMini40man Senior Member

    Latest action from this afternoon is here.
    http://www.youtube.com/watch?v=-Be15lPHjIA&feature=youtu.be

    Starting to get it to foil upwind which is a challenge. All about getting just the right amount of power out of the rig,. Not too much. I now have enough info to start making changes to the foils. The port foil is good for foiling in lighter winds, the starboard foil works well in a breeze, but only on a beam reach. There is a fine edge between success and failure!
     

    Attached Files:

  5. Doug Lord
    Joined: May 2009
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    Location: Cocoa, Florida

    Doug Lord Flight Ready

    ==================
    Ian, can you adjust the angle of incidence of the port and stb foils by radio?
     
  6. Doug Lord
    Joined: May 2009
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    Location: Cocoa, Florida

    Doug Lord Flight Ready

    MPX Test Model

    Here are shots of the gaff, peak halyard, upper outhaul, GDC rigged to the mast ready for the main. And the mast tang where both shrouds and forestay(s) will attach to the spectra strop. Also the the boom outhaul ready for the main:
    click-
     

    Attached Files:

  7. Baltic Bandit

    Baltic Bandit Previous Member

    PM40 - can you comment on what benefits you think you are seeing from having a fully battened main rather than a gaff rigged one?
     
  8. Madrc570
    Joined: Aug 2013
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    Location: Australia

    Madrc570 Junior Member

    other Specs

    Hi Doug, Sorry for the late response

    Below are all the sail are/ foil area/ weight ratios for my boat, the wetted surface area I will post later.

    I figured out how to get the exact sail area on AutoCad 2D the other day and it is the following

    Total Sail Area: 3798cm^2 (587in^2)


    Ratios:

    SA/ Weight:

    1.25kg to 3798cm^2

    2.75lbs to 587.3in^2

    213.5in^2 /lb



    Main foil area to Sail Area Ratio (same for metric and imperial):
    1: 36.21



    Cetreboard foil loading TO

    4.5g/cm^2

    0.065lbs/in^2



    Ama Foil Loading TO

    3.75g/cm^2

    0.06lbs/in^2

    Keep in mind everyone, the loading is really low at take off because the boat has a low take off speed (around 1.25m/s) I scaled down the f3 take-off speed to my boat size at it was 1.75m/s but because this is small and fiddley and I can't build things as well as Doug I reduced that by a fair bit. To get an idea of this speed, 1.4m/s is supposedly average walking pace.



    The set up is surface piercing foils on the ama's at the front and a main T foil on the centre board with a servo controlled flap.

    I Think this is everything Doug, the foiling foil loading will vary depending on the speed and down-force but its around 0.1 lbs /in^2 at 3m/s



    -Curtis
     
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  9. Doug Lord
    Joined: May 2009
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    Doug Lord Flight Ready

    Good stuff, Curtis-thanks!
    UPDATE- the "Master" post is now 947 and has been updated. All thats left is pretakeoff and after takeoff total wetted surface from you and the other guys.Then I can add the SA/ws ratio's.....Thanks for your help!
     
  10. Doug Lord
    Joined: May 2009
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    Location: Cocoa, Florida

    Doug Lord Flight Ready

    MPX Test Model-Mast +Main-2/2/14

    Wow! finished the main and rig today. One hell of a powerful main-wants to knock you over... Will be hard to carry the boat if there is a wind change while walking down the beach. Appears to be a problem two thirds up the luff-may be a bit of excess material but I'm not sure-had no vang on-sailmaker already knows about it since I spotted it a few months ago. We both decided to sail it before doing anything......he and I realized that to second guess a sail design with no wind in it (and act on it) is NUTS!
    Other than that the thing looks gorgeous in the wind! Great milestone for the project!

    Pictures-No one around to help get a picture with wind-she looks good and is very powerful. For size, note the doorway to the left:
     

    Attached Files:

  11. Baltic Bandit

    Baltic Bandit Previous Member

    to my eye of having sailed a lot of high perrformae skiffs and windsurfers, that sail really needs full battens. you already have an overtensiond gaff as yo have a stress wrigkle running rom the aft end of the gaff to the tack that's going to be moving your draft aft at the top of the sail right were you want it moving forwards and flattening the sail. Seriosuly. Take the tme, take it back tto the sailmaker and have them put on full battens.
     
  12. Doug Lord
    Joined: May 2009
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    Location: Cocoa, Florida

    Doug Lord Flight Ready

  13. Baltic Bandit

    Baltic Bandit Previous Member

    So I'm curious as to what you find impressive about it, from what I could see it takes quite a bit of time to get up on foils - requiring a fairy strong puff to move.

    And it tacks through roughly 120-130 degrees, which means that with leeway its CMG is around 75deg TWA. Doesn't seem that particularly impressive to me.

    I would hasten to note though doug, that they've managed a pretty solid squarehead main without any gaff. and as a result they have quite a nice leech shape.

    I think you need to have a chat with your sail designer now that the thing is rigged. put it in a dryland trainer base - like that which the windsurfers use - and see what it looks like loaded up - no you don't need to hurt your back with it, just attach a temporary stay to a tent peg in the ground and run a second peg as the attach point for the main sheet. (well ok a third one cuz your gonna need a forestay)

    I think you will find that you need to rethink the main
     
  14. tmark
    Joined: Sep 2006
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    Location: Stratford

    tmark Junior Member

    Congratulations on sticking with it Doug.
    This is a complex project with hundreds of pieces.
    It needs to be said that without individuals such as yourself, who have the dedication and imagination to design and build from scratch, we'd be a much poorer world. There's plenty an armchair critic out there who could take a lesson from your playbook.
     

  15. Doug Lord
    Joined: May 2009
    Posts: 16,679
    Likes: 349, Points: 93, Legacy Rep: 1362
    Location: Cocoa, Florida

    Doug Lord Flight Ready

    MPX Test Model

    =====================
    Thanks very much, Trevor!
     
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