Lots of discussion about line lengths and some things mentioned that were
not really accurate.
You have to understand a few things about kite design to compare apples and
oranges and the effect of line length.
It's not just projected area that makes a difference in power on a kite when
comparing a foil to LEI and certainly comparing foils of the will also need
a comparison of aspect ratio, material used in construction
(heavy/light/stretchy/porous), angle of attack, thickness of profile and
shape of wing. I've given a 3m Firebee to a guy flying a 9m inflatable in
the winter and he was surprised by the power in a 3m foil kite - (this is a
very moderate performance kite) and then handed them one of my racing
foils(a 3m Airea Raptor) and it totally spanked his ass because the kite
develops power and lift in a different and explosive manner compared to the
other foil.
In "general" a foil generates more power than an LEI and will fly faster
(but again there are a lot of different shapes and sizes etc) and there are
a lot of characteristics that need to be de-tuned to make them more friendly
for surfing or snowboarding otherwise they surge ahead to fast and you get
power bursts which make you fight the kite instead of concentrating on your
boarding and edging.
The newer power adjustable foils are a world of difference - this winter we
used the Peter Lynn Phantoms in a huge wind range and were totally in
control because the shape of the kite takes on the shape of a LEI with the
flexing of the "C" shape absorbing gusts, the line attachment allows for
changing angle of attack unlike a crown or arch bridle on standard foils -
almost no top end on the kites as we took big kites from moderate to intense
white-out wind out on the lake and flew them all day while almost every
other kite was changed for size or grounded during the intense winds.
Going back many, many years it was a simple trick to have a variety of line
lengths as opposed to a large quiver of kites. Most kites generate apparent
wind and fly faster and pull harder allowing you to multiply actual wind
speed. This effect is more evident with a good foil shape - to a greater
degree than that you get from a LEI. You do get power from a large foil by
flying a sine because the travelling kite allows time to generate apparent
wind. You intensify this effect by pulling in on a bar for a short distance.
A lot has to do with power zone available. If you stand still and fly a kite
from left to right on medium lines the kite may take 4 seconds to cross the
power zone, with short lines that could be 2-3 seconds, with really long
lines that could be 6-7 seconds. You have a longer period to generate power
and you are at a higher level that might have more wind. The trade off is
that you need a kite that will already fly in that light wind and it needs
to be able to have enough lift to work against extra line drag. Also, when
you start moving a lot of things change, the power zone is relative and you
need to adjust the shape of the sine so that you are not moving in and out
of it - sometimes closer to a figure 8.
You can slow a kite down by putting it on longer lines if it's to squirrelly
for you, you can speed up a kite by throwing it on short lines and it will
travel at a higher angle in the wind window allowing you to travel faster,
hold an upwind line and less side drag.
When trying to get lift for a jump long lines will not give you a quick pop
because the kite takes to climb to the zenith and it's generating pull at a
position starting to pull you sideways before you get to the zenith. So you
can keep the kite higher in the wind window so that you already have power
and it's more like doing a chin up, lifting yourself or you'll get a lower
jump but a long floaty one.
Shorter lines gives a quicker response and a sudden pop but the period of
available power is shorter. If you are in a clean strong wind or want to do
a lot of quick maneuvering, short lines are the way to go. NOTE* This is all
very general as aspect ratio also has a big effect on all of this.
We would often fly our 9/10m foils on 150ft lines, our medium foils on 100ft
and smaller foils on 75ft. But some of my favorite flying sessions were with
a 9m foil on 50 ft lines - a big kite really close and flying faster.
Bottom line, try out different lengths with your kite to see what effects it
- BEWARE that if you are flying in very light winds that you may have a kite
drop out of the - especially if a LEI goes nose over, be in a safe place
with plenty of unobstructed downwind room.
Mark
WindSpeed kites & design
flying all types of kites - a bad day kiting is still better than a good day
working

PS- speaking out of launching out of tight areas reminds me that's how Lee
Sedgwick came up with flying a kite through a dog stake a long time ago. If
you've never seen it, imagine flying a stunt kite standing directly downwind
right beside your kite. The lines run upwind, through a dogstake and back
down to the kite, it's like mirror flying with the kite all around you -
very impressive in skilled hands!