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Problem with delta kite

Carl

There are a multitude of reasons why a delta might not fly, but 
since you bought yours we might assume that it has been 
designed correctly (that is the keel is the right shape and in the 
right position, the leading edge spars are the correct length, 
the cross spar is positioned correctly). These things are now 
outwith your control so we will ignore them. 

There are only 2 things that can then be wrong. As Marty noted 
you should make sure that the leading edge spars are pushed 
down towards the trailing edge. That allows the kite to change 
shape during flight. If you don't do this it becomes "skittish". 

Secondly, you have replaced the cross spar. Get the cross spar 
length wrong and it wont fly. If the cross spar is too long, the 
sail becomes too tight. If the sail is too tight the delta will be 
unable to "bite" into the wind (I think this is a good way to think 
of it). So the kite has no "grip". It will then be skittish (fly left, 
right, circles, you name it), and look like a stunt kite without a 
pilot. It will also tend to "over fly", gliding overhead. This is 
due to a loss of drag (yes, drag is sometimes a good thing). 

In the deltas I've made the single part that takes longest to get 
right is the cross spar. There is a rule of thumb. Hang the delta 
upside down. The gap between the cross spar and the sail 
should be between 7 and 11% of the length of the leading edge 
spar. However, I generally fly my deltas before I give them to 
their new owner. 

So, push down those leading edge spars! If that does not fix the 
problem, shorten the cross spar (remember, make only one 
change at a time, then you can work out just what the problem 
was). 

Report back on your progress.

Patrick
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