Light and Frost(L&F) was asked to assist an owner of a Sonic FR 15 Meter kite in solving persistent tip fold problems. The kite would sometimes fly normally and then begin folding up at the tip latter during the session. Once the tip fold occurred the problem would remain until flight termination.
Several kite forums had threads concerning this problem which indicated this was not an isolated incident but no real solutions were provided.
L&F did the usual mixer test, looked for superficial damage and then did a line length audit. Most of the lines had shrunk 3 to 4 cm. But as Flysurfer kites experience an approx 1 to 2 cm shrinkage on most lines per year regardless of use, the shrinkage was considered normal.
During the inspection a hand was run inside the kite from the first outboard intake station 11-12 on the line plan along and thru the leading edge internal lateral circular vents toward the tip feeling for damage. The kite was then flown for a session by the owner. The flight was normal until the kite was dropped in the water and relaunched. The kite folded slightly on the water and was immediately airborne. There was very little water intake as no liquid exited the tip drains and only a slight wet sheen on one tip was seen and no line tangles, however the kite immediately began exhibiting various amounts of tip fold which could not be corrected regardless of how the kite was flown. The kite was returned to the beach. L&F suspected the vents mentioned above were being somehow constricted so a hand again run inside the kite opening the lateral vents on both tips. The kite was immediately flown and flight characteristics were again normal and remained normal till the tips were folded during poor handling wherein unrecoverable tip fold again occurred.
L&F is unsure the mechanism for this blockage but the only solution is to land the kite and open these vents manually by running a hand inside the kite as mentioned. The kite surprisingly can still be water launched in this condition and provides enough power to return to shore.
During a latter visual inspection of some of these circular vents a fraying almost to the point of being ripped was discovered although how such internal damage could occur in unknown.