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  1. #1
    Member murewa's Avatar
    Join Date
    Sep 2009

    US box fin position

    Tried to find an existing thread on this but 'fin' is too short for the search and 'position' is one hell of a common word in the technique forum.

    Enjoying my new 85lt when it gets really windy and choppy, even though I'm not even attempting gybes, just staking it at each end of the reach.

    It's helping my control technique and waterstarts but definately need to leave my gybe attempts to the 105.


    This is first board I have with a USbox attachment. My fins have about 2 - 3 cm of space either side once in. Currently I'm just lining it up in the middle.

    What effect would moving the fin forward or back have? Is this desirable and if so when?

    Also, especially with smaller fin and bumpy chop spin outs are still a bit of an issue. When moving over chop what is most likely technique flaw to cause these?

    excessive back foot pressure / not enough back foot pressure (especially when taking upwind course when overpowerd)? Entering water after small air fin first or flat?

    Last edited by murewa; 23rd August 2012 at 11:09 AM.

  2. #2
    Quick reply, via phone.

    Putting fin more forwards makes board looser in the turns or twitchier.
    Moving the fin back gives the board more directional stability and may help with your spinnout issues.

    But spinnout is more usually about technique. It happens when there is too much sideways load on the tail of the board either from your weight or because of how you've set up the rig. Try moving the harness lines back an inch and try raising the boom a bit. Both those should help improve mast foot pressure - where rig load applies more to the front of the board.
    Last edited by basher; 23rd August 2012 at 12:19 PM.
    Now back in the UK.

  3. #3
    Senior Member
    Join Date
    Nov 2009
    A lot depends on the fin design. Typically there are 2 types of fin for US boxes.....swept back wave fins, and more upright crossover fins. You can also get small freeride fins but these are mostly powerbox fitting now. If you are just blasting across your patch of water you are better off with a cross over fin which will give more lift and more grip. Adjusting the fin position is as per Basher's post but if you are using a wave fin the difference is going to be fairly marginal given that this design of fin makes the board pretty loose anyway.

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