Wills Wing Sport 2 155, Owner'S Service Manual

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Also be aware that in some thermalling situations, such as when trying to maximize climb rate in a
thermal with a very strong and very small core, there may be an advantage in overall effective climb
performance to flying so slowly that some portion of the inside wing is partially stalled most of the
time. This is, however, an advanced and potentially dangerous technique - it is the beginning of a spin
entry, and if pushed just a little too far can result in a sudden loss of control and / or altitude. In
general, if the tufts are indicating flow reversal associated with the stall, you will improve both perfor-
mance and controllability by pulling in and speeding up a little.
One final caution: from time to time a tuft may tend to stick completely to the sail, and fail to properly
indicate the direction of local flow. This may result from static buildup, or from the fine threads of the
yarn becoming caught on a seam or some dirt or imperfection in the sail. The tuft may stick while
indicating normal flow, but most often it will stick after having reversed, such that the tuft will indicate
a stalled condition that does not exist. One clue in this situation is to note whether or not the tuft is
wiggling. Since flow reversal occurs during a turbulent separated flow, a reversed tuft should be
wiggling rapidly. If it is not, it is probably stuck. A tuft indicating normal flow will not usually wiggle.
An occasional application of silicone spray to the tufts, and making sure that they are positioned so
that they cannot catch on any seam will minimize the problem of sticking.