Download Alpha - June 2015

Trimming Your Glider In Pitch
The fore and aft location along the keel of your hang point is commonly (if mistakenly) referred 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 required to fly fast, and the more effort will be required to fly
slow. The ALPHA performs best at speeds relatively close to VMS, however you will have noticeably
more response lateral control when flying 2 to three mph faster than that. Consequently we recommend that you trim the glider at least 2 mph above the speed at which your tufts indicate the beginning of spanwise flow. Hang loop fore and aft position is adjusted by loosening the velcro cinch strap
on the main hang loop, re-positioning the loop as desired, and re-tightening the cinch strap. Make sure
to tighten the cinch strap very securely, or the hang loop can slip in flight.
Hang loop must
be passed
through itself.
Velcro is used
to cinch loop
tightly to keel.
Hang loop must be
centered on bottom
of keel when velcro
is fully cinched.
Move hang loop towards
nose to increase trim speed
Move hang loop towards
tail to reduce trim speed
(Back up loop not shown)
We recommend that you not stow your glider bag, or any other cargo on the glider. The
practice of attaching your glider bag to the keel, for example, can drastically alter the
pitch trim and static balance of your glider, and adversely affect its flying and landing
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 position, 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 with your perception of the bar “position” relative to your
body. Airspeed indicators vary in their indicated airspeed depending on the make of the instrument,
its calibration, any installation error, etc. The use of tufts gives you an absolute first hand indication of
the actual aerodynamic event associated with two critically important airspeeds on your glider. It is a
potentially useful tool that may improve your flying.
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