Windknife trifoiler build

Discussion in 'Multihulls' started by revintage, Dec 7, 2018.

  1. revintage
    Joined: Nov 2016
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    revintage Senior Member

    Have fine tuned the foil section, with Doug Halsey helping me doublecheck it in XFOIL.

    I have also made the router file for the paulownia core.

    Think this is as good as it gets for a DIYer, using the Foil Nose for the first 27% and a flat bottom. The new N12FLATZ still uses the added +/- coordinates from NACA0012, where I have slightly manipulated the thickness from 27-46% chord length in Excel. Used the Pressure Coefficient Cp function in JavaFoil, to visually check the result and tame the irregularities.

    The first two XFOIL graphs was kindly supplied by Doug H.

    cpdoug.png cavZ2.PNG N12FLATZCROSSCUT2x10.png Skärmklipp.PNG cp.PNG
     
    Last edited: Nov 21, 2019
  2. nwguy
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    nwguy Junior Member

    It actually foiled very well. I just had structural failures when sailing at high speed with 2 people. Repaired one thing, then another thing broke, then another.
     
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  3. revintage
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    revintage Senior Member

    Sorry Jim, had to read your reports again. I understand it foiled well with only you on it, found the image below. It would probably only have needed more SA for two persons to foil earlier? Get the impression that you couldn´t adjust incidence on the rudder foil and because of that had to stand to balance it lengthwise?

    [​IMG]
     
  4. nwguy
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    nwguy Junior Member

    It foiled well with 2 people, only took about 12-13 knots of wind too. It just was weak in some critical locations. The final straw was a big crack in the junction of the forward aka and one of the side plates that were welded on the ends to attach the amas. The main foils' angle of attack were adjustable via 3 bolts per foil. You had to go to shore and use wrenches to do it. The rear t-foil's angle of attack was adjustable via a pin that went through the rudder cheeks and through various holes in the top of the rudder. You could do it while sailing, but you had to stop to do it. So no, the foils were not actively adjusted like a moth, with the feeler out front. That's a very hard problem to solve. I actually enjoyed "riding" it by moving around to change the angle of attack. You could instigate getting up on a foil that way and then leveling it out once you got going. Very exhilarating. I windfoil (windsurfer with hydrofoil) too, and you need to weight shift on that too to maintain level flight.

    What are your plans to control angle of attack?
     
  5. revintage
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    revintage Senior Member

    The rudder incidence will be set by turning the tiller extension, as I have bought a Waszp rudderbox and the gears inside it. It is actually the same system as Doug Halsey has built himself. About the mainfoils both will at first be manually controlled from where you sit. We have discussed adding an electronic system but that will be when and if we can make the boat work.
     
  6. nwguy
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    nwguy Junior Member

    I'll be interested to hear what happens with this.
     
  7. revintage
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    revintage Senior Member

    Hi Jim,
    We have discussed this a while ago on my Frankenfoil Sverige group . If you are on FB, please join.
     
  8. revintage
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    revintage Senior Member

    These are the N12FLATZ section coordinates.
     

    Attached Files:

  9. tspeer
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    tspeer Senior Member

    You might want to run those Xfoil analyses again using 1<Ncrit<3. I don't think you'll ever get the kind of laminar flow in water that is predicted using Xfoil's default Ncrit=9.
     
  10. revintage
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    revintage Senior Member

    Thanks for pointing that out. Anyway this might be of less importance as the analyses are just for comparision between sections?

    Adding a *.dat/txt file if you wish to check it, I would really appreciate if you did, makes me curious and eager to find out.
     

    Attached Files:

    Last edited: Nov 27, 2019
  11. revintage
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    revintage Senior Member

    Have been working on the A-cat center hull and realized the rear beam pocket is far to much to the rear. Instead of adding fittings on top of the deck, my idea is to cut out the original beam pocket including reinforcement and mount it from the underside a little further forward. This should be doable as the hull is ca 1.5cm wider if moving the pocket 0.5m forward where a smaller slot is cut. Building up new surfaces where the original pocket was, should not be a big problem.

    054C16F1-F843-4785-AE9A-638234CEB7D2.jpeg 3F36A3ED-37B0-4FA1-ABEA-ACCAA84819B4.jpeg 1AAB1636-42CC-4AE4-8B15-BC47CA74C3D1.jpeg 243EFE92-7993-4FCC-8FA2-C658C9EB268A.jpeg
     
    Last edited: Mar 2, 2020
  12. revintage
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    revintage Senior Member

    Cut out the pieces and will now fit the beam pocket under the forward slot. The rear beam will now sit perfectly to be sheeted from.
    cut out.jpg
     
  13. revintage
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    revintage Senior Member

    Rear beam waterstays.
     

    Attached Files:

    Last edited: Mar 26, 2020
  14. revintage
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    revintage Senior Member

    Settled for this version, where I will use the roller bender I built last summer, to make a 20x20mm square alu rod be inline with the waterstays. The "striker rod" will be 15mm round alu. M6(M8?) eye nuts on the outside.

    rearwaterstaypar3.png bender2.JPG eye.jpg
     

  15. revintage
    Joined: Nov 2016
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    revintage Senior Member

    Quite a while since I updated. Have found a broken in two Flying Phantom Elite carbon mast with 76x180mm section and everything is ready for epoxying. The mast was 9.6m and I managed to get the necessary 7.9m plus 0.6m sleeve out of it. Instead of messing with an inside reinforcement for the spreaders, I took the easy way out and opted for an outside sleeve.

    Just waiting for the PRO-SET ADV-175/ADV-276, recommended by Hamish at Wessex for the job, to arrive from abroad.

    The epoxy comes in 400ml cartridges to be mixed 2:1. Anyone who has got an idea how to use the cartridge without the far to expensive dispensing gun? Should be doable by modifying a std single cartridge gun.

    IMG_6528.jpeg IMG_6498.jpeg IMG_6527.jpeg Skärmavbild 2020-06-02 kl. 8.12.34 em.png
     
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