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 boat

    The winch arrived from Australia today(see post 247). The outside of the package was badly torn but everything was ok. Seems to be a holdup at Rockwest getting my carbon tubes out-they say it "should" be shipped out tomorrow-more than a week late. Good quality stuff at good prices but I happened to oder one of the tubes that said "new" on it and that was an understatement!
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    A lot of cats and tri's use something like indoor-outdoor carpeting inside a rudder cassette or daggerboard trunk to allow the board to be firmly held but easy to move. I've been trying to find something like that for the ama foils so that if I want or need to, I can retract the foil by radio using a servo. I've found a foam that I think will work but what concerned me was what if it doesn't-would I have to rip the whole trunk out? I just came up with a solution: a thin piece of carbon would have the foam glued to it and would be inserted in the trunk-if it doesn't work I can just slide the foam+ carbon sheet out and change the foam and reinstall. Glad I figured that out now!
     
  2. Petros
    Joined: Oct 2007
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    Petros Senior Member

    why do you need an adjustable gantry for the rudder/aft foil? why can't you just have it fixed in the correct position? do you need to be able to trim it's location by moving it for and aft?

    It just seems like an unnecessary complication if it is better aft, just fix the location there and eliminate some moving parts and extra weight.
     
  3. Doug Lord
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    Location: Cocoa, Florida

    Doug Lord Flight Ready

    SRT/MPX test model

    ---------------
    Well, with a foiler the correct position is as far aft as you can get it(more or less)-the point being to maximize the distance between main and rudder foil for pitch stability(while still keeping about 80% of the load on the main foil at takeoff). So since this is a test model, I decided to set the boat up to be able to adjust the rudder foil position to see just exactly what a difference it makes.
    Because of the unique foil system on this boat(where the mainfoil starts to unload as soon as the main hull flys), the pitch authority would probably be sufficient with the rudder foil at the transom but I want to learn more about what happens. It will be adjusted manually on the beach.
    ---Rudder foil at the transom: 83% of the load on the main foil at takeoff,
    ---Rudder foil 6" aft of the transom: 79% of the load on the mainfoil at takeoff.
    ---Increase in foil system footprint 17% with rudder foil at aftmost position.
     
  4. Doug Lord
    Joined: May 2009
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    Doug Lord Flight Ready

    MPX/SRT-test model

    Got the main hull completely sanded today-needs to be filled and hopefully only sanded once before being ready for Duratec. Matt McDonald(of Falcon Marine LLC)is going to spray all three components(main hull and two ama + curved piece units) with Duratec which will allow me to start the final sanding at 200.
    My new camera seems to have a couple of problems: the registration software won't allow the name to be registered. And, though I'm reasonably intelligent some of the time, no matter how many times I read the so-called instruction manual there is nothing that will allow me to upload pictures. So simple with the Kodak: just connect the camera to the computer,a little window comes up to allow you to name the pix and then they are automatically transferred to the picture file. Very frustrating with the Olympus!
     
  5. Doug Lord
    Joined: May 2009
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    Location: Cocoa, Florida

    Doug Lord Flight Ready

    MPX test model

    Finished sanding the ama's today-ready for filling.
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    The ama's are designed for incidental contact with the water at speed and the back end is shaped to allow relatively low drag moving a low speed. But, I'm going to test the concept of a foil assisted planing ama. The picture shows the approximate additional area that must be added to the ama bottom. This comes up now because I'm about to bond the ama to the "curved piece". The curved piece is installed parallel to the nominal static waterline but the bottom of the ama needs to be at a 2.5 degree running angle which has to be carefully cut out of the "curved piece" before bonding.
    The aft 7" of the ama with or without the area mod shown below must run at 2.5-4 degrees adjustable with the rudder foil. The original 4 degree set up for the running angle has been changed to 2.5 degrees since there may be small fluctuations in the boats running angle that can be controlled with the rudder foil, if need be. I'm afraid that setting the ama up for 4 degrees would be a mistake resulting in too much angle on the ama in some conditions.


    --Pictures Left to right: 1&2- ama plus planing mod, 2&3 "normal" ama shape(not carbonized), 5&6 "curved piece"(styro not yet carbonized) that will be bonded to the ama shortly and then carbonized(ama shown after carbonizing and before sanding and grinding) :

    click-
     

    Attached Files:

  6. Submarine Tom

    Submarine Tom Previous Member

    Well, that's pretty interesting Doug.

    I was thinking of the same approach on my race boat.

    I certainly don't want to highjack your thread so, if you prefer, respond on my thread "Quick, Easy 3-Man Canoe Plans".

    Do you think this approach would be worthwhile on 1" draft outriggers on a six knot canoe/kayak?

    The planing may only get them out of the water which may not even offset the wetted area benefit...
     
  7. Doug Lord
    Joined: May 2009
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    Doug Lord Flight Ready

    ===============
    Thanks Tom! I'm not sure there would be a lot of benefit at that speed. Just off the top of my head , maybe the lowest wetted surface hull would be best?
    Of course if the ama is real short it's planing threshold will be low too so it might work. But when you consider waves the advantage seems to go back to the low wetted surface shape. What do you think?
    PS- why don't you put a link to your thread here....

    =================
    Found the link ,Tom: http://www.boatdesign.net/forums/boat-design/quick-easy-3-man-canoe-plans-46038.html
     
  8. Submarine Tom

    Submarine Tom Previous Member

    Thanks Doug.

    Sorry, don't know how to do the link thing, otherwise I would have.

    I would tend to agree with you.

    What I might try is a screw on attachment to simply test it out on the prototype.

    Cheers!
     
  9. Doug Lord
    Joined: May 2009
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    Location: Cocoa, Florida

    Doug Lord Flight Ready

    MPX/SRT Test Boat

    The carbon tubes-primarily for the rudder gantry system - are set to arrive today from Rock West Composites.
    I just talked to Tony Stillman of Radio South in Brunswick, Ga about the batteries and charger I should use for this boat. I had had a previous recommendation from someone else to use LiPo batteries but if you make them mad they burst into flame! Tony suggested that I use Lithium Metal(Lithium Ferrite) @ 2000ma per battery pack which are more rugged than the Lipo batteries with a zero risk of fire caused by mishandling. Still got to watch out for water ,though.
    When I was professionally building RC sailboats we used Ni-Cads and Nickel Metal Hydride batteries were just becoming available-about 1995. Today everybody is using the lithium batteries and they are wierd-whether LiPo or L-Metal: they have two leads coming out for charging and you have to use a charger that automatically "balances" the cells-a critical function I'm told. I guess I'll be learning some new bits of battery technology!
     
  10. CutOnce

    CutOnce Previous Member

    You will .. and so will Boeing ... and the National Transportation Safety Board. In one month's time you will probably have head hunters calling you to sort out their issues.

    --
    CutOnce
     
  11. Doug Lord
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    Doug Lord Flight Ready

    Hah! Could be... In the work I do in my Real Job, I have been involved in testing lithium batteries about 4 years ago. They were used as emergency lighting for airliners. None of them used balanced cell charging technology but it was real hard(nearly impossible) to blow them up or cause them to catch on fire.
     
  12. P Flados
    Joined: Oct 2010
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    P Flados Senior Member

    I saw a video of a laptop doing a meltdown due to "a simulated short" with a lithium based battery at a test lab.

    The moral of the story was that if your laptop starts to smoke, get rid of it fast and think about the damage it is about to cause.
     
  13. Doug Lord
    Joined: May 2009
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    Location: Cocoa, Florida

    Doug Lord Flight Ready

    MRT Test Model

    =================
    Just so that it doesn't melt down the damn boat! The expert on batteries, Tony, told me the LiFE lithium batteries are significantly better than other older forms of lithium batteries especially LiPO......You have to use a charger made specifically for the battery that automatically balances the cells during charging. The weight savings in RC applications is just phenominal over gel cells, NiCads or the Nickel-Metal Hydride batteries of the "old" days.
     
  14. Petros
    Joined: Oct 2007
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    Petros Senior Member

    There has already been people hospitalized, and several house and car fires started by "runaway" lap top battery reactions. the new high power density batteries have a small risk of these kind of failures, the laptop industry has been trying to keep it out of the news since they do not want it to harm their sales, so they have been paying these people off with large settlements, and non-disclosure agreements.

    Now Boeing has found out in a very real and public way the problem with these "new technology" battery packs, it is only a matter of time before it becomes wide spread knowledge that high density batteries are not always stable, and can release all their stored energy in one fast "whoosh!".

    A long time friend of our family has their 20 year old son going through firefighter training, one of the big unknowns is how to protect both occupants and rescuers from the large battery packs in hybrid and electric cars. they need new equipment that can safely sever the battery cables BEFORE they can attend to any injuries. So even if the occupants are bleeding to death, they will have to tear open the battery compartment (after they locate it), use the specially developed tool to cut through the battery cables, and than attend to the injured. I would hate to see what happens when an electric car sized battery has a runaway reaction; GM has already offered to buy back all of their Volt cars after several such "mishaps".

    These modern high tech batteries are turning out to be very dangerous and unstable, at least for mass consumption. If you sell 40,000 lap tops with these high tech batteries, and "only" one in a thousand fail, that is 40 chances to kill one or more of their customers (or their customers family) in one production run. What is the risk to have several million hybrid car batteries running around in pubic? Or several hundred thousand electric cars running around?
     

  15. Submarine Tom

    Submarine Tom Previous Member

    Sadly, a risk, I suspect, society will be willing to accept.
     
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