26
(while well away from any terrain or other gliders) and watch your tufts (on the inside wing,
which will be at the highest angle of attack) you will get a feel for the way your minimum sink
speed varies at varying bank angles.
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 and extreme loss of control and / or altitude. In general, if the tufts are indicating
flow reversal associated with the stall, you will improve both performance and controllability
by pulling in and speeding up a little.
One final caution: from time to time a tuft may 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 yard 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 re-
versed, 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 sili-
cone 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.
TRIMMING YOUR GLIDER IN PITCH
The fore and aft location along the keel of your hang point is commonly (if mistakenly) re-
ferred to as your “CG location.” The location of this hang point will, all other things being
equal, determine at what angle of attack and airspeed your glider will naturally tend to fly (or
trim), and therefore how much bar pressure there is to pull in from trim to a given faster
speed, or how much pressure there is to push out from trim to a given slower speed. The
farther forward your hang point is, the faster the glider will trim, the less effort will be re-
quired to fly fast, and the more effort will be required to fly slow. Since the RAMAIR has
very light pitch pressures at speeds above trim, it is usually best to trim the glider at near
minimum sink airspeed. Hang loop fore and aft position is adjusted by removing the forward
tang securing the adjusting loop to the keel, threading the adjusting loop through the forward
and rear tangs until the desired position is achieved, and re-attaching the forward tang to the
keel.
PLEASE NOTE:
We recommend that you not stow your glider bag, or any other cargo on
the glider. The practice of putting your glider bag inside the sail, for example, can drastically
alter the pitch trim and static balance of your glider, and adversely affect its flying and land-
ing characteristics. The best place to carry your glider bag or other cargo is in your harness.
In the absence of the use of tufts, it has become common for pilots to talk about bar posi-
tion, or about indicated airspeed, when trying to communicate how to trim a glider properly
or how to fly a glider at the proper speed for a given situation. The problem is that these
methods are unreliable and inconsistent from one pilot to another even on the same glider.
The angle at which your harness suspends your body in your glider has a great deal to do
Содержание RamAir 146
Страница 49: ...45 Thispageintentionallyleftblank...
