Arc Tuning - Tip Twist
- Hi Arcers
Below is a copy of a post from the Foildesign group about tuning the
amount of twist in the tips of sled-foils. It refers to the internal
bridle line you can see running from the tips to the LE of the Arc.
Thought you might be interested.
"Hello Sled Enthusiasts:
A number of people have commented that their experimental
sleds didn't fly due to collapsing tips. One fix is to move the
towpoint aft along the tip until the collapsing stops but that often
results in a kite that won't fly up well overhead. Another fix is to
reverse 'wedge' the kite but this is basically the same as moving
Here is a simple fix that doesn't markedly effect the tow angle of
the center lifting section but quickly cures collapsing tips. I call
them tip twist adjusters.
1) You will need a large needle and some extra flight line or
similarly sized line.
2) Lay your sled out flat (belly up) and with a straight edge draw a
diagonal line on the inside (lower) skin from each wingtip's TE to
a point on the leading edge about 1/4 - 1/3 of the span from the
3) Secure the line at the leading edge point and very loosely sew
it along the line so that it emerges at the wingtip TE. Do this on
each side. (You only need to make a stitch at the profile seams
and center of each cell.)
4) Then adjust the length on each side to induce tip twist in your
kite. Start out with them loose and fly the kite. Then take them up
a cm or so at a time equally on both tips until the kite ceases to
You will make what seemed like a totally useless and frustrating
kite into a perfectly flying and more than likely, fast and stable
Beats starting over from scratch... Turns out one of my early
designs is also one of my best fliers with this fix.