Page 2 of 17 FirstFirst 1 2 3 4 5 6 12 ... LastLast
Results 8 to 14 of 116
  1. #8
    I wonder if he means forward mast foot pressure or sideways mast foot pressure?

    Clearly, it's like the blind leading the blind sometimes.
    Now back in the UK.

  2. #9
    Senior Member
    Join Date
    Dec 2007
    Posts
    2,376
    The way I think of this, is the board is attached to the water by the fin and pivots around it. Ok it doesnt actually do that, but helps explain the feeling of what happens in my mind.

    Moving footstraps, mastfoot, CoE of the sail, harness lines forward and backwards is the same as moving a force to a pivot point, the further away you move it the larger affect it has.
    ( http://www.bbc.co.uk/schools/gcsebit...ts/revision/1/ )

    Where the boom joins the mast must change the balance of the forces, as the sailors is hanging off it. So if you move the boom higher, when the sail is raked back on a board, that force must also move back. Vica versa when you lower the boom.

    I've nicked this pic from Zara Davies' facebook page from Luderitz and drawn red/yellow/green blobs on the mast and corresponding blobs on the board vertically underneath.

    So raising the boom is similar to moving the mastfoot back (see the How to make your board fly' video)

    Does this make sense?

    PS, the water isnt very flat there!

    Click image for larger version. 

Name:	G2.jpg 
Views:	279 
Size:	46.5 KB 
ID:	15722

  3. #10
    Quote Originally Posted by phil_in_poole View Post

    So raising the boom is similar to moving the mastfoot back (see the How to make your board fly' video)

    Does this make sense?

    No.
    Now back in the UK.

  4. #11
    Senior Member
    Join Date
    Dec 2007
    Posts
    2,376
    Quote Originally Posted by Wing 11 View Post
    We all know from practice that higher boom lift nose up.

    Every time I thinking about this I have confusion.

    When we put boom up,harness lines stay more vertical so we can transfer more weight on sail ,therefore mast foot pressure(MFP) also increase.
    Bigger MFP must hold nose down..

    Can someone explain why than boom up lift nose up ?
    What type of kit are you using? Wave, freeride etc

  5. #12
    Quote Originally Posted by Wing 11 View Post
    I think he mean on downward mast foot pressure,force that mast base push on board deck..

    That indeed is our standard understanding of mast foot pressure.

    I only made that distinction because the way he describes having less sail area above the boom would hang the leverage about the boom in a sideways manner.

    But, in truth, that thinking is still misguided, as it mixes internal forces with external ones. It's like saying if you can pull hard enough on your own shoelaces, you can lift yourself off the ground.

    In practice, mast foot pressure actually comes from us sheeting in and from the proportion of our body weight acting through the mast foot as we hang off the rig.
    Now back in the UK.

  6. #13
    The difference between slalom and wave kit is how much the board rides (or flies) off the fin, as opposed to riding off the rails.


    In slalom, tuning is often about controlling fin lift and we shift the rig towards or away from the fin to achieve this.
    As fin lift can affect how high the nose rides, then tuning/positioning of the mast foot affects this. (You can also alter the rake of your chosen fin.)

    Raising or lowering the boom however, with the mast foot in one place, tends to simply affect how much the sailor loads the tail of the board and the sideways load on the fin.
    What ever mast foot or boom height your choose however, you can still affect board trim (nose height) by leaning forwards or back.
    Last edited by basher; 13th November 2017 at 09:53 PM.
    Now back in the UK.

  7. #14
    Senior Member
    Join Date
    Dec 2007
    Posts
    2,376
    Quote Originally Posted by Wing 11 View Post
    Slalom,isonic + EVO 8
    Do you find that that adjusting boom height gives the same affect they mention in the How to make your board fly video?
    I assumed by 'nose up' you meant that is the same as 'flying off the fin' more.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •