porosity of seams / Flexi performance

In article <1993Feb21.212801.14375@ohm.york.ac.uk>, jkn@ohm.york.ac.uk (John Nicoll) writes:
>I ask for thoughts and comments on the above. Anyone with multiple
>flexis - how does performance compare? Might the weight and/or bend
>of the spar make all that much difference? Is there another aspect I
>haven't thought of ??

I attended a tuning seminar given by Ray Merry, one half of the
flexifoil team. Basically, there is only one way to tune a flexi, and
that is to increase or decrease the tension on the sail by changing
the the bridle points. I don't remember exactly, so the following
could be reversed...

When the sail is pulled too tight, the outside cells are closed when
the spar is curved. This reduces the lift from that section of the
kite and lowers overall speed.

I did do some experimenting, and tightening and loosening the sail did
affect the speed of the kite noticably.

The flexibility of the spar also has an effect on the kite. The taper
also changes things. I have three 4 foot flexi's. Two fly almost
identically. The third has a stiffer rod and doesn't fly as fast as
the other two. I didn't notice this until I tried to stack the three
Marty Sasaki            Harvard University           Sasaki Kite Fabrications

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