Skid Fin for Crackerbox

Discussion in 'Mono Forum' started by Phil Fowler, Dec 13, 2018.

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  1. Dec 13, 2018 #1

    Phil Fowler

    Phil Fowler

    Phil Fowler

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    on a cracker box hox do you determine the location of the forward skid fin ?
     
  2. Dec 15, 2018 #2

    GraysonTaylor

    GraysonTaylor

    GraysonTaylor

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    Behind the center of balance.  My Eaglet (flat bottom) had a skid fin that was right about the center of gravity and you had to steer it to go straight.  I removed it and never got back to trying it out without a fin. .....
     
  3. Dec 17, 2018 #3

    Phil Fowler

    Phil Fowler

    Phil Fowler

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    Thanks Grayson. 
     
  4. Dec 19, 2018 #4

    David Bryant

    David Bryant

    David Bryant

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    so you would check CG with engine, radio-box (with gear), and all hardware mounted, before mounting?
     
  5. Dec 20, 2018 #5

    Grimracer

    Grimracer

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    When I designed the Gunslinger for Aquacraft I did a butt load of testing on fins and drive placement..

    I for the life of me cannot remember where the fin ended up..LOL

    Seems to me it was round 25% but I just dont remember. I was however WAY surprised about the placement of the drive. Off the transom and down the keel line IS NOT the best way to set this up.

    Grim
     
  6. Dec 21, 2018 #6

    GraysonTaylor

    GraysonTaylor

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    Yes, the Cg with all the hardware installed.  Just before where the shaft comes through the hull is probably it. I had glued and screwed my fin, so removing it was major surgery. That's why I  wanted to test with no fin.
     
  7. Dec 21, 2018 #7

    Christian Lucas

    Christian Lucas

    Christian Lucas

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    Hi,

    have you ever run a crackerbox with an outrigged turnfin . Outrigged turnfin on the corner inside lokated short after the c.g. ?

    i have very good result with outrigged turnfins on monohull as when cornering the water on the pressure side of the fin will not lift the hull like a skidfin that is lokated in the middle under the hull. To get the same left and right hand cornering performance i tryed outrigged fins on both side of the hull. Very important is that the fin is mounted only by (i like 3 ) round screw bolt so that the water can free stream between hull and fin . For a future hull i will test turnfins with servo drive to give them an higher angle of attace wile turning, like a rudder but at a forward position. 

    Happy Amps Christian
     
  8. Dec 28, 2018 #8

    NAMBA860

    NAMBA860

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    Do you have a pic of this set up you can post
     
  9. Jan 1, 2019 #9

    Christian Lucas

    Christian Lucas

    Christian Lucas

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    Hi,

    belong to the c.g. i would place it after the c.g. . There it has to be bigger but prefent the boat from spin off. If the fin is much forward of c.g. it can be much smaller as the lever arm to c.g. is longer but you need a very good ruder with strong mechanics as spin off is done easy.

    Happy Amps Christian

    71380A7A-11D1-4A0E-BF1C-6215E2DF13E6.jpeg

    821626A2-B976-4336-ABC4-D5D25B39364C.jpeg
     
  10. Jan 3, 2019 #10

    Mark Anderson

    Mark Anderson

    Mark Anderson

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    That fin would be much better if there was a third attachment point above or below the other two. Interestingly, Dave Villwock has/had a full scale Super Stock/ Pro Stock flat bottom with an outboard mounted turn fin. He and George Woods Jr. set several records with it. It does not have the stand offs there is an addition to the hull that the fin mounts to. If they are legal in cracker box, it would be a big advantage over a keel mounted fin.

    IMG_1957.JPG
     
  11. Jan 7, 2019 #11

    Phil Fowler

    Phil Fowler

    Phil Fowler

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    Wow thanks for that Guy's Great information.
     

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