Date:	Thu, 23 Sep 1993 15:47:10 -1000
From:	moishi@uoguelph.ca (Maurice Y Oishi)
Message-Id: <27tjiu$he9@nermal.cs.uoguelph.ca>
Organization: University of Guelph
Subject: "Pulsing" - One solution


Awhile back, I wrote that I had trouble with "pulsing," rhythmic
pitching of my kite while it was flying straight. A number of you
kind souls posted or e-mailed me advice. Most of you suggested that
I adjust my bridling. Thankfully, it looks like bridling, and not
the frame, was at fault.

I've been awaiting a sufficiently windy day to test out my new
bridles. Today was the day. It flew well.

I tried two things: I lengthened all of my bridle lines and decreased the
relative length of my outrigger (this might not be the proper term - I
mean the leg that runs between the joint that connects the lower cross
spar and leading edge, and the tow point). 

Here's the effect, viewed from the base of the spine:
(Only half the kite and the two aforementioned bridle lines are
shown)

CURRENT SETTINGS:                |
                      tow point  |
                                /\
                              /     \
               outrigger    /          \
                          /               \
                        /                    \
Plain of the kite     o-----------------------o--- - - - -
                    l.e.      left          spine    right


ORIGINAL SETTINGS:
                                      |
                        tow point     |
                                     /\
                  outrigger      /      \
                             /            \
                         /                  \
Plain of the kite     o-----------------------o-- - - - - 
                    l.e.      left         spine       right


How do I rationalize this change? I guess the easiest explanation
is to look at the angle formed at the leading edge by the plain of
the kite and the outrigger. It seems to me that by increasing this
angle, the bridle lent more direct support to the lower section of
the leading edge spar in the face of a strong winds, i.e., the
outrigger became more in-line with the direction of the wind. This
effectively increased this spar's rigidity.

An alternative explanation that I haven't discounted yet is that
the new bridling altered the angle of attack (due to a shift of the
tow point). The pitching might simply have been due to the kite
cyclically stalling and recovering in strong winds. i.e. slopping
bridling.

Any comments on how I did right, despite myself? (Honestly, I'm
just glad the thing flies better than it did...although its
unpredictability really got my adrenaline going).

Again, thanks for the help,
Mo



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