Stunt Kite Bridles and bridle settings (was Re: MFEM, Help with Tuning!!!!)
Marty Sasaki
I'm constantly reminded that many people don't change the bridle
settings on their kites. I walk out on the field and see a kite that
is flying badly and I offer to help. I tweak the bridles a bit and the
kite suddenly leaps into the air, or turns better or something
similar.
The stunt kite books on the market all talk about changing bridle
settings and how that affects a kite. When I ask someone whether they
have one of these books, they often answer that they do, yet it
doesn't occur to them to change the bridle.
Anyway, here are some recommendations for tuning. I'll base a lot of
what I'm saying on my kites since I understand them the best, and talk
a bit about the MEFM, since that is what started this discussion in
the first place. I'll also talk a bit about the Turbo bridle from
Stunt Kites II.
A lot of what I will say here I first learned in a seminar at an AKA
Convention (don't remember which one) that was given by Alan Nagao,
with help from folks in the crowd.
Let me also suggest that you actually go out and do the experiments
suggested here. This will give you a better feeling for what is
actually going on.
I'm assuming that the kite has a "standard bridle", where the longer
continuous line goes from the upper spreader connector to the T
connecter (lower spreader and spine intersection). The outhaul (line
from bridle point to lower spreader connector) should also be
adjustable.
First, adjustments along the longer continuous line:
Generally, placing the bridle point lower will increase the pull and
decrease the forward speed. It will also decrease the turning radius
of a kite. Most of the "radical moves" are easier to do with lower
bridle points.
Moving the bridle point upward will increase the forward speed and
increase the turning radius of a kite.
Many people call moving the bridle point downward as "setting a kite
heavier", and moving it upward as "setting a kite lighter".
Generally, you will move the bridle point upward in light wind and
downward in high wind.
Try this experiment. Place the bridles very low. Low enough so that
the kite won't get off of the ground. Move the bridles up, a bit, a
few millimeters, and fly the kite with it set this way. Continue to
move the bridles up until the kite begins to slow down again, or the
turns become large and difficult to control.
At some point you will discover the "sweet spot". Here the kite will
turn well, but track well too. It's the best compromise for a given
kite in a given wind.
Note that the sweet spot may be different for different people. Also
note that the sweet spot may change with different wind conditions.
Now, adjustments with the outhauls:
Some kites don't respond well to changes in outhaul length. Others can
change their performance radically. Manufacturers who have fixed
outhauls on their kites have set the outhaul length at what they feel
is the optimal length. Don't be afraid to experiment though, your
flying style might be different enough that changing the outhaul
length will improve a kites performance.
In general, shorter outhauls will cause a kite to turn quicker. They
will also sometimes decrease the turning radius, or allow setting the
center bridle for a tighter turn. Shorter outhauls will also increase
the "radical-ness" of some, but not all, kites.
When you shorten the outhauls, you will have to move the bridle point
up in order to maintain forward speed. It is very kite dependant, but
a ratio of between 3 to 1 and 5 to 1 seems appropriate. For example,
with the Katana-3 Freestyle, the ratio is about 4 to 1, so when I
shorten the outhaul by 2cm, I move the bridle point upward about 5mm.
Most kites aren't as sensitive to outhaul adjustments as they are to
other adjustments, so I usually make outhaul adjustments in 25mm
increments intially. I might fine tune this after I get things
approximately right.
Again, you might want to experiment with outhaul lengths in a
systematic way. Start with the outhauls at the "factory" setting and
then shorten them. Experiment with the long line bridle setting and
then repeat.
The reason for actually doing this experiments is to see how tuning
effects the way a kite flies. After you have done the experiment a few
times, you can quickly change the settings on a bridle to change the
way the kite flies to your liking.
Here's an example:
With the outhauls at the last mark (the outhaul at it's longest
setting), and the bridle points about 25mm down from the top mark, the
Katana-3/Freestyle is moderately fast and will turn on it's wingtip at
moderate speed. It is radical enough to axel easily, but in moderate
wind is sometimes difficult to stall directly down wind. I would fly
the kite set up this way for Individual Precision, and it would
probably be a fast pairs/team kite.
With the outhauls at the shortest setting (about 10cm shorter) and the
bridle point at the top mark, the kite spins on it's lower spreader
connector, and is much faster and faster turning. Radical moves are
easy (although not as strange as a Stranger) and the kite can be
stalled directly down wind in moderate winds. Set this way it's too
fast for my reflexes for precision or team/pairs, but the speed and
turning ability make it a great ballet/fun kite.
The MEFM and the Infinity Bridle:
Here's one of those, "Why didn't I think of that?" ideas. The Infinity
Bridle combines the adjustments of the long line and the outhaul into
one package.
For those who haven't seen it, the bridle has one line going from the
top spreader connector to the T-fitting. I'll call this the vertical
line. There is another line that is attached to the vertical line and
to the lower spreader connector on the leading edge. I'll call this
the horizontal line. Finally, a loop is attached to the horizontal
line. The flying lines are attached to this loop.
When you want to shorten the outhauls (increase the radical-ness,
speed up turns) move the loop, on the horizontal line, towards the
wing tip. In order to maintain the same forward speed, you will have
to move the connection on the vertical line up a bit.
When you want to set the kite heavier, you should move the connection
on the vertical line down.
The Turbo bridle:
The Turbo Bridle is an interesting device. It is constructed by having
one line going from the upper to the lower spreader connector (the
vertical line), and another line going from the vertical line to the T
fitting (the horizontal line). The loop is on the horizontal line.
The effect of this arrangement is that pulling on a line to make a
turn also effectively lowers the bridle point. The turn will be
tighter and faster than a "normal" bridle. Straight line flight will
is smooth and precise, so in straight lines, the kite will be less
radical, with better tracking.
I've only done a little experimenting with the Turbo Bridle, but it
does work as advertised. With my kites, the suggested lengths result
in a too long bridle that makes axeling and other similar stunts
difficult. I suspect that shorter bridle lines will help, but haven't
had a chance to try it out yet.
--
Marty Sasaki Harvard University Sasaki Kite Fabrications
sas...@noc.harvard.edu Network Services Division 90 Melrose Street
617-496-4320 10 Ware Street Arlington, MA 02174
Cambridge, MA 02138-4002 phone/fax: 617-646-1925
--
Marty Sasaki Harvard University Sasaki Kite Fabrications
sas...@noc.harvard.edu Network Services Division 90 Melrose Street
617-496-4320 10 Ware Street Arlington, MA 02174
Cambridge, MA 02138-4002 phone/fax: 617-646-1925
Philippe Lepez
(Marty Sasaki) says:
Good paper Marty!
>Generally, you will move the bridle point upward in light wind and
>downward in high wind.
I've been told that if the wind still gets higher you should return
the bridle point to a higher setting to reduce stress on the kite frame.
I will add that a shorter outhaul helps in controling side slides.
>The MEFM and the Infinity Bridle:
snip ..
>The Turbo bridle:
I allways have thaugth that the MEFM had a Turbo bridle instead of an
infinity bridle, so what kites do use a turbo bridle?
And now a puzzeling case. I have a kite that I am unable to tune.
It flies slowly, its wind window is *small* (120° at most). So, move the
clip up !
But, the kite slows down when turning, its trurns are rather wide, it is
*hard* to stall. So move the clip down !
So what ?
To be fair I must say that the kite is vented (a vented raaseri and I
use a much more open mesh than Simo uses).
Good winds.
Philippe.
--
Philippe Lepez (CP 125), | | Good kite
Universite Libre de Bruxelles, | Email: ple...@ulb.ac.be |+ Good wind
50 av. Roosevelt, | Phone: 32.2.6503553 |----------------
1050 Bruxelles, Belgique. | Fax : 32.2.6503323 |= A lot of fun !
George W. Gilchrist
Thank you.
Cheers, George
--
==============================
George W. Gilchrist
gil...@zoology.washington.edu
University of Washington
Department of Zoology
Box 351800
Seattle, WA 98l95-1800
Simo Salanne
>What a great article, Marty!!! I'm running off a copy to keep in my kite bag.
>Thank you.
>
>Cheers, George
>
Agree, it made me feel like reading Marty's rec.kites articles
of vintage 1992.
Simo
--
Simo.S...@csc.fi STACK Finland
====================================================================
Are you familiar with Kite Flyers Web Site? http://www.kfs.org/kites
Frank Siegel
: Let me also suggest that you actually go out and do the experiments
: suggested here. This will give you a better feeling for what is
: actually going on.
Excellent post on bridles, Marty.
Inspired by the post, I spent 2 hours yesterday playing with the bridles
on one kite. I had previously modified the bridle to create a simpler to
adjust main line (using a loop with a double larkshead- works great), and
was very familiar with those changes.
Adjusting the outhauls was something new. The kite, a 3/4 Lotus by New
Tech, was difficult to stall downwind. Shortening the outhauls in steps,
the kite characteristics changed markedly. Pull was reduced, and I was
able to raise the mainline connection lighter so that the kite will
accelerate on a tug. The kite now stalls like a champ, slides
wonderfully, and (for the first time), I was able to axle out of a slide
and straight downwind. Spin-stall landings are now fast and accurate- but
the kite isn't twitchy. It can turn tighter (about 2 inches below the
lower spreader)- In short, a wonderful change. (note- this is a *very*
inexpensive kite- 6 ft, Carbon and Icarex)
Also, I found it to be a good source of excercise. Move the outhaul,
trot back, fly, land, trot in, change the mainline, trot back (repeat
about 50 times).
Now, I'm interested in figuring out a way to create an adjustable
outhaul that does not leave loose ends hanging- any ideas would be
appreciated.
Marty- thanks for the post, it's been a big help.
Frank (the other one, not nasty at all)