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

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

  1. Doug Lord
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    Doug Lord Flight Ready

    Thanks, Troy! I still enjoy that kind of sailing too. For years as a kid I raced a Gaff headed sloop called the "Fish" class. It was designed by one of the Herreshoffs and was the club boat for many yacht clubs along the Gulf coast.
    Unfortunately, when kids at other clubs were learning about spinnakers-we didn't -main,jib, whisker pole.
     
  2. DennisRB
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    DennisRB Senior Member

    Congrats Doug!! Looks great. Do you have much info on the speeds it reached?

    The high camber tip foils look to work great to achieve early foiling, but won't they cause a lot of drag in anything but light foiling conditions with anything but ice flat water? High camber foils to provide lift are nothing new at all and are used all the time when lift matters more than drag. Seems even in the lightest chop the flap will be thrashing the waves as the flap will be right on top of the water. Have you considered how this will effect speed and drag?
     
  3. Doug Lord
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    Doug Lord Flight Ready

    Fire Arrow Foiler / MPX Foil System Testing and Development

    Dennis, read post 1617-1618--I think it answers your questions. If not I'll try to explain further.
     
  4. DennisRB
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    DennisRB Senior Member

    No it doesn't answer my question. You say that there will be no extra drag once the flap is out of the water. I am saying that this wouldn't appear be the case in anything but totally flat water.
     
  5. Doug Lord
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    Doug Lord Flight Ready

    Fire Arrow Foiler / MPX Foil System Testing and Development

    You're right that the rougher the water the more there will be incidental immersion of the high lift portion of the foil. But that's ok with me because it allows foiling in conditions that normally wouldn't permit the boat to foil. And in those rougher conditions they'll be more wind-I don't think the drag will be significant though a foil without the i-flap would likely be faster. It's like everything in design-its a compromise to allow early foiling. As I trim the foil down it will be interesting to see how much i-flap area I can remove and still have early takeoff.
    See next post for more on this---
     
  6. Doug Lord
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    Doug Lord Flight Ready

    Fire Arrow Foiler / MPX Foil System Testing and Development

    Dennis, your questions got me thinking. My original plan was to cut down the flap leaving just the amount of high lift that I needed for early take off. In going over it all carefully as I decide what modifications to make to the ama foils, I'm thinking I may have skipped a step. After the last light air video I decided I would go all out to get the thing in the air-no matter what it took. So I brought the main & rudder foil up to an area where they had the same foil loading as the F3(which took off in very light air) and changed the area of the ama foil so that it had more area and a 15 degree flap attached to the foil on the uptip portion of the foil. The step I skipped was to try the uptip portion with greater area but no change in angle of incidence/no flap. If that works it will be less drag throughout the speed range and looking again at the GC32 picture below settled it: the port foil will be modified to take out the 15 degree flap but leave the planform area as is. If the area doesn't do it then I can add in the high lift flap as necessary .The starboard foil will be left with the i-flap as is until we sail the two together and see what happens. Thanks for helping to spark my thinking on this!
    So for the next sail:
    1) My sailmaker and I ,with some ideas from Magnus, will go over the main until it is right,
    --
    2) The port ama foil will have the i-flap removed and be tested with the same planform area-just no flap,
    --
    3) Surgery will be done on the mast to allow a 2' removable section for reefing.

    Pictures-1) GC32 with the UptiP foil breaching the surface at very high speed,
    2) picture showing the original idea to remove portions of the i-flap to reduce drag. Instead, for the next sail, I'll remove the i-flap and leave the planform area as is. If it works that way it will be a lower drag solution throughout the speed range:
     

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  7. Doug Lord
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    Doug Lord Flight Ready

    Fire Arrow Foiler / MPX Foil System Testing and Development

    In getting ready to do the foil and rig mods I noticed something I haven't posted. Last Thursday after foiling the boat for the first time on video, I was ,shall we say, a bit excited. So when I got home I could barely contain myself to get everything unloaded so I could do the video upload to you tube.
    Got the rig in the house first-it rides in the car on top of the main hull then came out and pulled the boat out. There was a little drag and I ASSumed the crossarms were caught on the tarp-so I just pulled harder(without looking!). But ,oh no that wasn't it: the wand retainer that holds the wands up for transport had come loose and both wands caught on the car and both broke! On the port side the paddle broke clean off, on the stb side the tube that supports the adjustable part of the wand split down the middle. Horsefeathers!
     
  8. Doug Lord
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    Doug Lord Flight Ready

    Fire Arrow Foiler / MPX Foil System Testing and Development

    Here are a couple pictures of the modification process on the port UptiP foil. I thought I'd have to have a couple of F & A cuts to bend the flap up
    but I cut too far on the left side and the whole thing bent up. Now I'll glue balsa on the bottom side to hold the former flap in place and then fill and carbonate the top side(after a little grinding). The foil will wind up with the same area as with the i-flap, only it will be a thinner version of a 63-412 section with 4 degrees of "washin"(the opposite of washout) where the angle of incidence of the foil increases 4** degrees from the radius to the tip(twist)*. Removing the flap should reduce the drag substantially but the question is how will it affect early takeoff. It will be easy to tell when sailing with the unmodified starboard foil. If it costs too much in early takeoff the flap will be put back in place. If the no-flap version works ok as far as early takeoff goes, then the starboard i-flap will be removed.
    * if it works="posiTWIST" UptiP foil- to a more limited extent than the i-flap this foil will tend to generate more lift in the last third of the uptip because the tip will be exposed at speed making a net gain for lighter air and reducing the high lift portion of the foil when the tip breaches the surface.
    **Looks more like 3-3.5 degrees when it's done
    --Update: top side carbonated/peel plied-bottom tomorrow, finish Friday-see last picture:
    ------------------------
    I found this in my research on variable geometry airfoils. Some who follow this thread might find it interesting: http://www.boatdesign.net/forums/hydrodynamics-aerodynamics/flexsys-51054.html#post698689
    -----------------------
     

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    Last edited: Jul 31, 2014
  9. Doug Lord
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    Doug Lord Flight Ready

    Fire Arrow Foiler / MPX Foil System Testing and Development

    Heres the short version of the video. The long version is on the previous page. Some problem tacking probably due in large part to the radio dual rate/expo that I set up so I couldn't turn it off. The rig also played a roll in slowing tacking. It's likely to be the radio,primarily, since in previous videos the boat ,generally, tacked fine except for rudder induced pitch-ups. To prevent those I went too far with the programming to de-sensitize the rudder.
    ===========

    Here is the url to my youtube channel which has all the videos done so far, plus an oldie but goody: https://www.youtube.com/channel/UC6S7JPG1d2uZ91lqt7ObyIw

    ==========



    https://www.youtube.com/watch?v=7Mok3d4KiMI


    Note pictures A and B below: the cool thing is that the lee ama altitude stays about the same even after the main hull flys-illustrates the excellent altitude control of the UptiP foil:
     
    Last edited: Aug 1, 2014
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  10. Doug Lord
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    Doug Lord Flight Ready

    Fire Arrow Foiler / MPX Foil System Testing and Development

    Here is the finished port foil with the i-flap removed. Final wash-in=3 degrees-that is : the angle of incidence of the uptip portion of the foil increases from zero at 3.5" from the center of the radius to the +3 degrees at the tip.

    click--
     

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  11. Doug Lord
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    Doug Lord Flight Ready

    Fire Arrow Foiler / MPX Foil System Testing and Development

    I've been working on the rig to eliminate excess twist which should be a natural with this rig. I've used a similar rig on almost every RC and fullsize boat I've built and never had the excess twist problem that has been hard to get rid of-mainly because it has been low priority until now. The GCD(Gaff Control Device-originally mentioned page 63, post 932) is going to be eliminated. While it has some merit in stronger winds it messes up control of the head in lighter wind because the gaff halyard attachment point is intentionally off axis. It will be replaced with carbon tube mast extension tied into the new jib strut. The strut will project about an inch forward of the leading edge of the mast to take the jib halyard so the normal jib can be used with the shorter(reefed) mast. That way there are going to be no recuts to the main or jib for the reefing system.
    In experimenting, a lot the biggest problem I found was that I simply didn't get enough pre-tension on the gaff halyard before tightening the vang and downhaul. With the right tension the rig can be de-twisted perfectly ,yet still react with excellent gust response by simply adjusting the vang. The gaff halyard pretension has to be there in light or heavy air and that's where the problem with the GDC came in. The level of tension sorta fooled me because it is a LOT more that I remember on previous rigs using this system-and the reason for that has to be the bigger head-the largest I've ever used in proportion to the length of the boom. Under this level of tension the GDC would bend causing a "bump" when the gaff would change sides. It's conceivable with this new level of tension that in light air the gaff could get stuck on one side or the other. So the GCD experiment is over tonight.
    ---
    The new reefed main will go from 2507 sq.in(17.4 sq.ft.) to 1912 sq.in.(13.3 sq.ft.) The wing mast will go from 179.8 sq. in.(1.24 sq.ft.) to 141.4 sq. in.(.98 sq.ft. ) and the jib(for now) will remain at 704 sq.in.(4.9 sq.ft.).
    So main + mast + jib is reduced 18.6% and and main +mast is reduced 24% for the reefed rig.

    Picture-click for some clarity- I tried to show the new mast extension tube and jib strut as well as the current GCD:
     

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  12. Doug Lord
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    Doug Lord Flight Ready

    Fire Arrow Foiler / MPX Foil System Testing and Development

    Well, my 7 year old computer died Monday night. I've got a new one and a friend is looking into recovering all my files. Work files were backed up but all my pictures and design related documents weren't.
    I made a new mast extension to replace the GCD(see above). I added a much more powerful purchase to the "peak halyard" and added several full length battens. Now the sail looks real good and I can completely de-twist it. In fact, it looks so good I'm going to sail with it again before I add the reefing system. I'd bet it has at least a third more power in lighter wind now. On a sail this size the fancy cut seems to cause small wrinkles-probably almost impossible to get those small pieces exactly right. That said, the sail looks much better and the twist is now 100% controllable. The biggest problem with twist was that I simply did not put enough force on the peak halyard. It needs more force in light air than in heavy air.

    Click-
    In picture 3, #1 is a single block w/becket, #2 is a double block, #3 is a fixed single block, #4 is a bracket that ensures line always leads from center regardless of mast rotation, #5 is a single block:
     

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  13. Doug Lord
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    Doug Lord Flight Ready

    Fire Arrow Foiler / MPX Foil System Testing and Development--Reefing

    Took an irreversible step tonight-I cut the fantastic mast from Forte Composites in two places. Yeah, it makes me nervous. The segment cut out of the mast allows for removing 20.625" from the bottom of the main. The piece is simply removed and the bottom segment inserted into the top segment, luff wire tightened,bottom of main rolled up and retained by velcro, tack and clew re-attached and voila!-the rig is shortened by 4 sq.ft..
    The same jib will be used, and can be removed to further reef the rig.
    Main+ jib before reefing: 3390sq.in.(23.5 sq.ft/2.19 sq.m) After: 2796 sq.in.(19.4sq.ft. / 1.8sq.m). Rig is reduced by 17.5%. With rig shortened and jib removed, by 38%. It's a simple way to reduce sail and with the exceptional righting moment of 66ft.lb., should extend the wind pressure range substantially.

    Click-
     

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    Last edited: Aug 14, 2014
  14. Doug Lord
    Joined: May 2009
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    Location: Cocoa, Florida

    Doug Lord Flight Ready

    Fire Arrow Foiler / MPX Foil System Testing and Development--Reefing

    The reefing system is complete and ready to sail. To unreef the rig: 1) loosen vang and peak halyard, 2) undo luffwire,downhaul,tack and clew, 3) unroll sail, 4) insert mast section, 5) redo #2 & #1 and that's it. Can be done in about three minutes-reefing or unreefing.

    Pictures-click for best detail,L to R, 1) & 2) Rig reefed and main rolled up. You can see the tabs where the tack and clew attach to the reefed sail, 3) Reefed rig with mast segment that is removed, 4) Velcro pieces on sail to hold rolled sail. First used this system 20 years ago-works well:
     

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  15. Jim Caldwell
    Joined: Aug 2013
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    Location: Cleveland, Ohio

    Jim Caldwell Senior Member

    And, half of an end plate!
     
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