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  1. #43
    Senior Member Graemef's Avatar
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    If you use a tendon joint, watch the distortion, it's to weather not to leeward.

    Pic your board up by the footstraps and the rig at the boom, the front of the board is lifted at the mast foot.

    See how long you can continue forward motion when not attached to the board i.e. in a both feet off the board drag, the board slows immediately. There is little to no driving force through the mast foot, it's just a steering and pivoting component, weight only gets applied when you apply it for whatever reason. Or when the rig depowers or moves more vertical in transitions, the bear off etc

    Yes the trim of a board can be altered by moving the mast foot forward, but that only applies because you move forward with it.

    90% of the driving power goes through the straps or your feet via the deck.

    How many times has the board nose completely cleared the water when you're manouvring for a water start or the board flipping if you engage the power without the nose being offwind or you have some weight on the board.

    The maximum power that goes through that mastfoot is the weight of the rig if not canted to weather, unless you apply mastfoot pressure, or the wind is very light, generally it is negative.

    The only time there is any serious downforce is when you are driving hard off wind, but that's because the bottom of the rig is trying to drive backwards towards you and in so doing drives the nose down in the same way a vang on a boat drives the boom and the battle there is to alleviate it with stance changes.
    Last edited by Graemef; 16th November 2017 at 03:35 PM.

  2. #44
    To realise how wrong some of that is you just have to imagine the mast foot not attached to the board. I'm still a believer in mast foot pressure.

    Yes there is a sideways component to the U/J load and at times it's to windward and at other times to leeward. But there is always a (much more significant) downward component unless you are jumping the board.


    If, like me, you ever stand up your rig on the beach to get the harness lines correctly positioned, you can do a simple test.
    If you plant your mast foot in sand or on grass or mud to do this then the weight of the rig alone buries the mast extension a bit. Then when you sheet in against the wind, it sinks further.
    Then when you hang off the boom you might find it sinks even further...
    I suppose you could then raise the boom and see if it sinks further still.
    Last edited by basher; 16th November 2017 at 04:57 PM.
    Now back in the UK.

  3. #45
    Senior Member Graemef's Avatar
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    Quote Originally Posted by basher View Post
    Then when you hang off the boom you might find it sinks even further...
    I suppose you could then raise the boom and see if it sinks further still.
    I'd suggest you go and talk to your 'son' in the supermarket trolley maybe he can explain it to you.

  4. #46
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    Quote Originally Posted by basher View Post
    To realise how wrong some of that is you just have to imagine the mast foot not attached to the board. I'm still a believer in mast foot pressure.

    Yes there is a sideways component to the U/J load and at times it's to windward and at other times to leeward. But there is always a (much more significant) downward component unless you are jumping the board.


    If, like me, you ever stand up your rig on the beach to get the harness lines correctly positioned, you can do a simple test.
    If you plant your mast foot in sand or on grass or mud to do this then the weight of the rig alone buries the mast extension a bit. Then when you sheet in against the wind, it sinks further.
    Then when you hang off the boom you might find it sinks even further...
    I suppose you could then raise the boom and see if it sinks further still.
    Now try putting the mast foot on a hard surface instead of sand and see what happens better still to emulate the situation of a board sitting on water, mount the mast foot on a small wooden board with castors ( e.g a plant pot mover). You will see then that the vast majority of the force is directed either to windward or to leeward depending on the pivot angle created by the boom and your body angle.

  5. #47
    Senior Member Graemef's Avatar
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    If our new 'father' figure were correct you'd never get airborne in a jump and all jumps would be nose first and freestyle tricks would be a lot lot more difficult. Ironically the lighter the wind the more pressure on the mast foot or when as i said before driving hard downwind but at most other times when you have your own weight supported by the boom, it becomes pivotal in the load sharing.

    The other key time when mast foot pressure is important to drive the rail is riding waves, hence more upright rig and stance brings more mast foot pressure into the driving component which then helps engage the rail further forward, but then at the top of the wave on the cutback it's gone again, maybe he'll get that bit if we switch into 'wave speak' something he does at least pretend to understand, did you get that son?

  6. #48
    Quote Originally Posted by mikerb View Post
    Now try putting the mast foot on a hard surface instead of sand and see what happens better still to emulate the situation of a board sitting on water, mount the mast foot on a small wooden board with castors ( e.g a plant pot mover). You will see then that the vast majority of the force is directed either to windward or to leeward depending on the pivot angle created by the boom and your body angle.

    Are we allowed to stand on the board with castors?

    Think about it.

    That's a good example of internal versus external forces.


    There's a good reason why Windskate boards can only go forwards or backwards. If they were fitted with castors they'd just blow downwind.
    Last edited by basher; 16th November 2017 at 06:58 PM.
    Now back in the UK.

  7. #49
    Quote Originally Posted by Graemef View Post
    If our new 'father' figure were correct you'd never get airborne in a jump and all jumps would be nose first and freestyle tricks would be a lot lot more difficult. Ironically the lighter the wind the more pressure on the mast foot or when as i said before driving hard downwind but at most other times when you have your own weight supported by the boom, it becomes pivotal in the load sharing.

    The other key time when mast foot pressure is important to drive the rail is riding waves, hence more upright rig and stance brings more mast foot pressure into the driving component which then helps engage the rail further forward, but then at the top of the wave on the cutback it's gone again, maybe he'll get that bit if we switch into 'wave speak' something he does at least pretend to understand, did you get that son?

    It's a good job your upwind leverage thing doesn't apply to short boards when wave sailing.

    Are you sure you have thought this through?
    Now back in the UK.

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