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Thread: turn fin adjustment

  1. #1

    Default turn fin adjustment

    how do u adjust the turn fins and how much do i have to move it. any pics???

  2. #2


    Many posts on this but it sounds like raising the fins by using the lower hole on the fin and screwing it to the top hole on the boat, follow the angle of the outside hull and drill another one for the top and plug the bottom one. I just bent mine for the angle. I understand they need to be raised but I will try this first. The stock position is REALLY bad for cornering and you can see it when it comes at you, It leans to the outside.

  3. #3


    Has anyone tried these boats WITHOUT the turn fins installed? Cats usually don't need them... Though I know the sponson angles on these ones are relatively flat, so maybe it does...

  4. #4


    I have,,,brings a whole new meaning to the term "squirrley". I put them back on after only one run without them.

  5. #5


    ...this is good for me to know....

  6. #6


    Quote Originally Posted by Doby View Post
    I have,,,brings a whole new meaning to the term "squirrley". I put them back on after only one run without them.
    Interesting... I have one of these hulls, but have not run it... I think this hull needs some rethinking as to the sponson angles...

  7. #7


    This may be a simplification of what is actually needed, but if I keep the stock turning fin position in terms of drill holes, can I simply:
    1) bend them to match the edge of the hull
    2) shorten them instead of raising their position where they attach to the hull?

    For those of you who have been slowly trimming the fins down, what tools have you been using? Any good recommendations of how much was needed to trim? As I surgeon, I know how much easier it is to take material away then it is to add it back on if you've gone too far...

    Tweaking this boat would be so much easier if I owned a full set of tools and had a hobby shop in my condo...

  8. #8

    Default fins

    I shortened and angled mine worked for me I also sharpen them.I used a vise , hamer and angle gage and to cut them I used a cut off wheel on my die grinder.[IMG][/IMG][IMG][/IMG]
    Last edited by krusty; 07-01-2009 at 10:28 AM. Reason: add text

  9. #9


    Looks good, Krusty, thanks...What inline hardware setup is that? Am I crazy, or are those the original drill hole placements and stuffing tube position?

  10. #10

    Default hardware

    it is a fuller's hardware set up for a cat and you use the top two holes but have to drill two lower holes I then used flexible epoxy on the in side to seal it up. I also used very thin servo tape between the strut and the boat and did the same with the trim tabs. The epoxy is also to add strength here are a couple of pics.[IMG][/IMG][IMG][/IMG]

  11. #11


    Ah, ok - it looked like the fullers setup but thought maybe you found a short cut...thanks!

  12. #12


    @ Krusty how much did you shorten them down? How long are they from the corner on the outer side to the bottom (if you get what i'm saying)

  13. #13

    Default fins

    They are about 1 1/4' long from out side corner to bottom. If I remember right I shortened them by 1/2', which is the distance between the two mounting bolts. instead of raiseing them to the top hole which is 1/2" I cut and bent them. You will need a vise.

  14. #14


    Tools are no problem, have a workshop in the garage with all the needed tools and plenty more.
    Already sharpend mine, sharp as a knife and cuts a paper like a hot knife through butter.

    There is plenty of mph lost by the turnfins, i got these results with my stock BJ26 runing 2S 20C Lipo's (except from the battery trays that has been removed)

    Before Sharpening 54.9 Km/h - 34.3Mph (Stable @ Top speed)
    After Sharpening 57.9 Km/h - 36.1Mph (Stable @ Top speed)
    Removed Fins 60.3 Km/h - 37.7Mph (A bit shaky @ Top speed, uncontrollable in corners)

    @ Krusty: Is there a big improvement in the handling? And did you gain or loose some speed on the top b doing this mods?

  15. #15


    Over stock I found a huge difference I can now make high speed corners, stock it would flip. Thanks for posting the speed diferences it sounds like I sould leave my fins on I was going to remove them to ensure I broke 50 mph but it does not seam worth it from what you said.

    When I did these mods I did not have my gps yet so to be honest with you I am not sure. with my stock esc and motor on a x - 442 she ran 39.7 mph two day's ago and my best is 44 mph on the stock set up.
    Last edited by krusty; 07-05-2009 at 07:56 PM. Reason: added

  16. #16


    The speeds i posted may be fooling you. Note that i gained about 1.5Mph after removing the fins. But i'm also only doing mid-High 30's, the drag coused by the fins would be greater as the speed increases.

    As the speed doubles the force quadruples the drag, this is in air, not sure how it is in water but as the drag is greater in water it may even be more.

  17. #17


    Just to post my experience with messing with the turn fins

    I angled my turn fins in, without shortening them, The boat seemed VERY stable like this, my fastest run with them was 38.5mph.

    When i removed the turn fins, the boat seemed to be able to turn much sharper, but was very wild and wanted to dance at higher speeds. My fastest run with no turn fins was 38.9mph, but my battery power was dwindling at this point, so i will have to try with full charged batteries.

    I am using fullers hardware on my boat, just to clarify.

  18. #18
    Join Date
    Nov 2007


    back when I had my black jack, I simply cut 1" off of the fins. It didn't really make a difference in speed with the cut shorter and sharped nicely. My boat ran 45 mph with the stock motor and 53 mph with an ammo 2300 on 12 cells. I did remove the stock drive adding a strut and offset rudder.

  19. #19


    very cool ! you ran some great numbers I hope I can join you in the 50 mph club soon!



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