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[ksurf] Re: Kite size / weight ratio

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  • srosso@bunge.com.br
    Dave - excellent theory but you speak of windspeed at the kite - When I (and most others) speak of windspeed this is measured at the beach at ground level -
    Message 1 of 23 , Oct 1, 1999
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      Dave - excellent theory but you speak of windspeed at the kite - When I
      (and most others) speak of windspeed this is measured at the beach at
      ground level - Which is the only practical place to measure it !!

      then you go out and the wind is probably 6 knots at altitude out on the
      water but who cares ! as far as we know its still 3 knots on the beach -
      and those windsurfers will be very impressed.

      I am not saying your theory is wrong - lets not go there - I am saying that
      when we kitesurfers speak of low wind planing limit - its most probably the
      wind on the beach at head level... depending on the beach the wind "at the
      kite" (as you said) can be anywhere to up to 3 times as much ! (2 knots vs
      6 knots)
    • Mark Frasier
      ... That brings up a question I ve been meaning to ask - is the wind at 30 ft to ground wind ratio bigger in lower or higher ground winds? Or about the same?
      Message 2 of 23 , Oct 1, 1999
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        >Dave - excellent theory but you speak of windspeed at the kite - When I
        >(and most others) speak of windspeed this is measured at the beach at
        >ground level - Which is the only practical place to measure it !!
        >
        >then you go out and the wind is probably 6 knots at altitude out on the
        >water but who cares ! as far as we know its still 3 knots on the beach -
        >and those windsurfers will be very impressed.
        >
        >I am not saying your theory is wrong - lets not go there - I am saying that
        >when we kitesurfers speak of low wind planing limit - its most probably the
        >wind on the beach at head level... depending on the beach the wind "at the
        >kite" (as you said) can be anywhere to up to 3 times as much ! (2 knots vs
        >6 knots)

        That brings up a question I've been meaning to ask - is the "wind at 30 ft
        to ground wind ratio" bigger in lower or higher ground winds? Or about the
        same?

        Mark Frasier
      • Hung Vu
        ... Or not enough board volume. Why the name scalloping (edging)? ... I have not done any research nor experiment on this matter (I did try a couple boards,
        Message 3 of 23 , Oct 1, 1999
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          Mark Frasier wrote:
          >
          > >There is always more wind higher up (using 45 m lines, I felt it all the
          > >times) but I found them not very useful, especially when you have to
          > >turn the kite upward after diving it down. This will make you fall if
          > >you don't have enough wind below. One trick I always do in this
          > >situation is to turn the board windward (to add more apparent wind) when
          > >I start to turn the kite upward.
          >
          > Buggiers call that "scalloping". I can't seem to make that work ont he board
          > - it seems to sink too fast. I think a lot of the trouble might be my lack
          > of board handling skill.
          >

          Or not enough board volume.

          Why the name "scalloping" (edging)?

          > >A bigger board may help too. I have yet figured out the relationship
          > >between board size and rider weight. There's definitely a correlation
          > >between board volume and rider weight, but I am not so sure about the
          > >correlation between board length, width and rider weight?
          > >
          > >Hung.
          >
          > Hmm...so do you think I should look for a board with a higher volume instead
          > of a larger planing surface?

          I have not done any research nor experiment on this matter (I did try a
          couple boards, but not enough). You may want to do some research and
          experiment and let us know. Just on the "surface", I guess board volume
          could be proportional to rider weight. Larger planning surface could
          help but I have no idea how much for the length and how much for the
          width.

          Hung.
        • Mark Frasier
          ... The tracks that are left in the sand look like the edge of a scallop shell... sort of like a bunch of arcs end to end. Makes for slow progress but it s
          Message 4 of 23 , Oct 1, 1999
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            >Mark Frasier wrote:
            >>
            >> >There is always more wind higher up (using 45 m lines, I felt it all the
            >> >times) but I found them not very useful, especially when you have to
            >> >turn the kite upward after diving it down. This will make you fall if
            >> >you don't have enough wind below. One trick I always do in this
            >> >situation is to turn the board windward (to add more apparent wind) when
            >> >I start to turn the kite upward.
            >>
            >> Buggiers call that "scalloping". I can't seem to make that work ont he board
            >> - it seems to sink too fast. I think a lot of the trouble might be my lack
            >> of board handling skill.
            >
            >Why the name "scalloping" (edging)?

            The tracks that are left in the sand look like the edge of a scallop
            shell... sort of like a bunch of arcs end to end. Makes for slow progress
            but it's better than walking :)

            Mark Frasier
          • David Raue
            Hung s right! My kitesurfing skill is only slightly greater than 0, yet I managed to plane and get about quite nicely with an XXXL in about 8-10 mph. I weigh
            Message 5 of 23 , Oct 1, 1999
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              Hung's right! My kitesurfing skill is only slightly greater than 0, yet I
              managed to plane and get about quite nicely with an XXXL in about 8-10 mph.
              I weigh about 190 lbs. The necessary skill may be with the kite more than
              the windsurfing.
              Dave
              ----- Original Message -----
              From: Hung Vu <hungvu@...>
              To: <kitesurf@egroups.com>
              Sent: Thursday, September 30, 1999 10:11 PM
              Subject: [ksurf] Kite size / weight ratio


              > Robert Pratt wrote:
              > > These guys are experts, there is NO WAY!!! your going to be able to
              plane in these conditions for a long time (years?)
              > > when I first got my 8.5 Wipika I kept taking it out in winds <10mph, if
              I was able to get it off the water the best I could manage was way downwind.
              >
              > It's more dependent on how much a person weight than skill. My weight
              > has been "published" on this list a number of times since last year and
              > the way to calculate the kite size based on another person's experience
              > is pretty straight forward and has been also "published". Here it goes
              > again: kite size is "approximately" proportional to weight. If a 50 kg
              > person uses a 5.0 m2 kite, a 100 kg person should use 10.0 m2 kite. The
              > kite quiver that I currently have to kitesurf from 5 knots (start to go
              > upwind) to 30 knots (start to feel way overpowered). I uses lines
              > ranging from 35 - 45 m. All the kites I have are very good so far and I
              > am very happy with them; however, I am planning to sell them and change
              > to a new quiver next year (just to have new experiences with other
              > kites; so many kites, so little time!):
              >
              > Hung at 125 lb:
              >
              > XXXL 9.66 m2 foil 5-6 knots to 10 - 11 knots
              > Wipika 8.5 m2 8 knots to 16 knots
              > Wipika 5.0 m2 12 knots to 22 knots
              > Wipika 3.5 m2 19 knots to 28 knots
              >
              > The wind was too strong (especially the gusts) today for my 3.5 m2
              > Wipika. I spent a third or half of the time waiting on the beach for
              > the wind to "calm" down a bit. Someone could have made a "fortune"
              > selling me a smaller kite then.
              >
              > To achieve the same thing, someone 170 lb would need:
              >
              > 13 m2 foil
              > 11 m2 Wipika type kite
              > 6.8 m2 Wipika type kite
              > 4.76 m2 Wipika type kite
              >
              > To achieve the same thing, someone 220 lb would need:
              >
              > 17 m2 foil
              > 14.9 m2 Wipika type kite
              > 8.8 m2 Wipika type kite
              > 6.16 m2 Wipika type kite
              >
              > These numbers are pretty good given or taken a few .1 m2 or knots;
              > however, they are still just an approximation. Have a good selection and
              > have fun!
              >
              > Hung.
              >
              > ------------------------------------------------------------------------
              > To unsubscribe, send a message to kitesurf-unsubscribe@...
              >
              >
              >
            • Dave Culp
              Message 6 of 23 , Oct 1, 1999
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              • Art Clark
                ... . huge clip full of things to think about.... . Keep the faith, Dave. I for one enjoy reading your posts immensely. I may not agree with everything you
                Message 7 of 23 , Oct 1, 1999
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                  ----------
                  >From: dave@... (Dave Culp)
                  >To: kitesurf@egroups.com
                  >Subject: [ksurf] Re: Kite size / weight ratio
                  .
                  huge clip full of things to think about....
                  .
                  Keep the faith, Dave. I for one enjoy reading your posts immensely. I may
                  not agree with everything you write, but it gets me thinking & learning!

                  Art
                • speleopower@yahoo.com
                  I ve got another 8.5 Wipika for sale just came on this one. It is in good shape and is complete with everything you need. Kite, boom, 30meters line, quick
                  Message 8 of 23 , Oct 1, 1999
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                    I've got another 8.5 Wipika for sale just came on this one. It is in
                    good shape and is complete with everything you need. Kite, boom,
                    30meters line, quick release. I'm asking $550 USD + your choice of
                    shipping, insurance etc.
                    This one has been tuned and flys great.
                    Finally got to try out some longish lines on my XXXL. I used about
                    200ft in about 8mph then the wind picked up to 12-13mph. I got my
                    world rocked when it picked up. Lots of fun. The kite flys much
                    better on longer lines in my opinion. Up to today I've only used about
                    90feet-100ft(off of my XL). On launch it dragged me about 60ft across
                    the sand. Good fun. Pretty good jumps waves were about 1-3feet.
                    About twisted my ankle off during a crash.
                    I will now recommend owners of a Quadrifoil XXXL to go with a long
                    line set. I'm going to cut mine down to about 150feet because 200 is a
                    bit to long.
                    Pray for wind and pray that it does not come up while your flying your
                    big guns.
                  • George Hradil
                    Hi, Dave, I am one of those lurkers and as an engineer I enjoy your posts, however, I do not feel I have much to add on top of your long experience and sound
                    Message 9 of 23 , Oct 2, 1999
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                      Hi, Dave, I am one of those lurkers and as an engineer I enjoy your
                      posts, however, I do not feel I have much to add on top of your long
                      experience and sound analysis.

                      I also mess around with radio control sailplanes and I have an
                      appreciation of the 3-D wind picture which most sailors don't. It is
                      amazing how many lulls on the water are actually the leward side and
                      bottom of a thermal. This is significant for kite surfers, can you use
                      the upward velocity?

                      FYO there are several small telemetry devices available to measure air
                      speed on RC aircraft. Should be light and small enough to put on a kite
                      to measure on kite wind velocity. I don't know about water proof though.
                      I will e-mail you specific vendors if you are interested.

                      Regards George Hradil
                    • Dave Culp
                      ... Absolutely! Oh, kites don t have use for upward motion, per se. What we *do* have use for, just like a racing sailplane, is being able to dive the kite,
                      Message 10 of 23 , Oct 2, 1999
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                        >Hi, Dave, I am one of those lurkers and as an engineer I enjoy your
                        >posts, however, I do not feel I have much to add on top of your long
                        >experience and sound analysis.
                        >
                        >I also mess around with radio control sailplanes and I have an
                        >appreciation of the 3-D wind picture which most sailors don't. It is
                        >amazing how many lulls on the water are actually the leward side and
                        >bottom of a thermal. This is significant for kite surfers, can you use
                        >the upward velocity?

                        Absolutely! Oh, kites don't have use for upward motion, per se. What
                        we *do* have use for, just like a racing sailplane, is being able to
                        "dive" the kite, down into it's apparent wind, without actually
                        losing altitude. This is a major plus, if and when possible. I'd bet
                        most kiteflyers cannot tell the difference between a small thermal
                        and an ordinary gust. The difference is great, of course, in that
                        thermals can be predicted from visual clues (clouds), while gusts
                        normally cannot.

                        >
                        >FYO there are several small telemetry devices available to measure air
                        >speed on RC aircraft. Should be light and small enough to put on a kite
                        >to measure on kite wind velocity. I don't know about water proof though.
                        >I will e-mail you specific vendors if you are interested.

                        Please do. Perhaps off-list, if you will, so as not to offend anyone
                        wiht the extra bandwidth: dave@... Thanks!

                        Dave Culp
                      • Primoz Cerne
                        Hi Gorge , Dave and others! Sorry for this misunderstanding, I like too the group the expertise from Dave and the others. I don t wont to break down the group.
                        Message 11 of 23 , Oct 3, 1999
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                          Hi Gorge , Dave and others!
                          Sorry for this misunderstanding, I like too the group the expertise from
                          Dave and the others. I don't wont to break down the group.
                          From my past I have also many experiences to build and fly my tail less
                          gliders, so aerodynamic terms are not new for me. For example on the
                          races we was able to start with the winch the glider, using the special
                          tracking path, push the glider up to 200km/h with the max. winch speed
                          of 16-20m/s. The physic is the same, winch is the wind speed and the
                          glider on the line is kite.
                          Dave can we set up the table of relations from the weight of the kite
                          and the surface area. With other words, how much wind we need to keep
                          the kite on the top of the window position.


                          touch and go
                          Primoz

                          Web page of SEAJUMP group,
                          http://www.olimp.si/seajump
                        • David Raue
                          This kind of technical discussion is what the foildesign
                          Message 12 of 23 , Oct 3, 1999
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                            This kind of technical discussion is what the >foildesign< group is all
                            about. Why not post details there so all the technoweenies can benefit?
                            It's Foildesign@onelist.com . Seems like that group would love all this
                            stuff.
                            Dave

                            ----- Original Message -----
                            From: Dave Culp <dave@...>
                            To: <kitesurf@egroups.com>
                            Sent: Saturday, October 02, 1999 8:22 PM
                            Subject: [ksurf] Re: Kite size / weight ratio


                            > >Hi, Dave, I am one of those lurkers and as an engineer I enjoy your
                            > >posts, however, I do not feel I have much to add on top of your long
                            > >experience and sound analysis.
                            > >
                            > >I also mess around with radio control sailplanes and I have an
                            > >appreciation of the 3-D wind picture which most sailors don't. It is
                            > >amazing how many lulls on the water are actually the leward side and
                            > >bottom of a thermal. This is significant for kite surfers, can you use
                            > >the upward velocity?
                            >
                            > Absolutely! Oh, kites don't have use for upward motion, per se. What
                            > we *do* have use for, just like a racing sailplane, is being able to
                            > "dive" the kite, down into it's apparent wind, without actually
                            > losing altitude. This is a major plus, if and when possible. I'd bet
                            > most kiteflyers cannot tell the difference between a small thermal
                            > and an ordinary gust. The difference is great, of course, in that
                            > thermals can be predicted from visual clues (clouds), while gusts
                            > normally cannot.
                            >
                            > >
                            > >FYO there are several small telemetry devices available to measure air
                            > >speed on RC aircraft. Should be light and small enough to put on a kite
                            > >to measure on kite wind velocity. I don't know about water proof though.
                            > >I will e-mail you specific vendors if you are interested.
                            >
                            > Please do. Perhaps off-list, if you will, so as not to offend anyone
                            > wiht the extra bandwidth: dave@... Thanks!
                            >
                            > Dave Culp
                            >
                            >
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