I know very few sailplane pilots who couldn't stand to get better launches, thermal
more effectively, descend from critical altitude more safely and generally benefit from
increased glide path control on final approach. With practice, a flapped wing will easily
accomplish all these tasks.
LAUNCHING -- Good launch height is an initial strategic step in setting up any thermal
flight. Without it, it's difficult to explore for lift. Of course, there are exceptions;
early morning 'bubbles' that haven't separated, etc. But that's another column and this
section intends only to address the typical launch. It's fairly common knowledge that all
gliders can be adjusted for a more vertical climb by moving the tow hook rearward or by
pulling a slight amount of up elevator. Although the tow hook should be mounted in the
correct location from the start, an increased vertical altitude can also be accomplished
by using a bit of flap. Most would obviously prefer a preset to handle this task, but I've
seen it done on the left stick. If the glider is equipped with ailerons, they can also be
drooped to increase lift and discourage any tendency to tip stall. This type of stall is
fairly frightening, usually producing a sudden snap to the left at the point the pilot
releases the model after building up line tension. Warps and unbalanced wings or a bad
toss create this unwanted reaction (ask me!), but it's almost always because the pilot
didn't 'throw' the airplane. For most, the easiest way to recover is to stay solid on the
pedal and apply opposite rudder. Don't use the ailerons! Kit manufacturers will usually
suggest the amount of control surface deflection for launching, but a good starting point
is ailerons down 3/8" and flaps down 1/2". Occasionally, a bit of up elevator
(equivalent to about 2-3 clicks of trim) will also help in the mix.
Some of the figures used in this article come from the Mako construction booklet, but
are consistent with most of the hi-tech kits currently on the market. Experimentation is
the key. Of course, if you find yourself breaking winch lines frequently, don't wait for
anyone to ask you to decrease your launch camber! Also, downwind and the 'average'
hi-start launches are best accomplished with little or no camber enhancement.
Zooms -- I only mention this because it's something that should not be attempted with
the flaps deployed. The flaps must be retracted just prior to coming over the top to
reduce the possibility of overstressing the wing and destroying the model. Although the
zoom is an important part of the launch, particularly during the contest season, it
requires a lot of practice and is seldom executed correctly. Although somewhat spectacular
looking, many less experienced pilots will actually fly past the turn-around, severely
dive the glider, and then pull 'up' elevator only to lose altitude. This defeats the
purpose. Once the bottom of the wing is visible, give a little down elevator to get off
tow and let the sticks recenter. The air speeding over the wings creates lift that
translates into altitude.
SINK -- Sometimes we'll luck out and launch into a sizeable thermal, but more often
than not, we'll encounter the 'sink hole' that almost always precedes the lift. If it
isn't obvious, the tail is usually a good indicator and will appear to be 'dragging'. The
rule is to speed up in sink and slow down in lift by reflexing the flaps (up approximately
1/16") and if you have ailerons, by the same amount. The effect is to uncamber the
wing so it reacts more like a flat-bottomed airfoil (i.e. SD3021). Then a slower
undercambered wing like the SD7037 can be made to penetrate through the sink without any
appreciable loss of altitude. From personal experience with the 7037 on both my MAKO and
Falcon 880, I can't say reflexing was truly effective and I don't have a problem keeping
up with the pack without it. Traditionally, however, an RG15 will pull away from me with
little effort. The advantage to the faster airfoil is the ability to travel through sink
to reach the next thermal. The drawback is that it doesn't signal lift as well and
generally requires the eye of an expert flyer to work it efficiently. Roger Lackey once
told me that when he first started flying the RG15, he wondered where all the lift went!
THERMALING -- The sailplane will usually appear to slow down when approaching lift. The
tail may rise up or more likely, a wing tip will go up on the lift side. A good starting
point here would be flaps down 3/16" (ailerons 1/8"). Some pilots use their
launch preset for thermaling, but I prefer to use the flexibility of the Vision radio and
find myself constantly making camber adjustments since no two thermals appear to be
identical.
THERMALS (SMALL DIAMETER) -- Flaps functioning as ailerons (flaperons) on full-house
ships can improve the model's ability to core minute bubbles. The flaps are usually set up
to move half as much as the ailerons and are angle-cut at the hinge line to allow upward
deflection.
HIGH ALTIUDE DESCENT -- Most Of us have seen old W.W. II film footage of Nazi Stuka
dive bombers hunched over and falling out of the sky with that infamous whine of some
cleverly mounted sirens. They would terrorize anyone in their path. Before spoilers on
model gliders became prominent, losing altitude by holding the rudder stick in the lower
left hand corner could be pretty terrorizing even without the siren! But in reality,
although it looks bad, it is far less stressful on the airframe than screaming down with
the spoilers out or doing a speed-run from considerable altitude. It's fun until the
turbulence introduces flutter, a loss of control surfaces, stripped servos, and usually a
wing that finally disintegrates. Descending with flaps is the 'other' alternative and very
much 'Stuka-like'. Basically, pull a small amount of flap (about 1/2") and let the
nose come up, slowing down the glider. Add full down elevator and 90' flaps at the same
time (kind of like working a car's clutch and gas pedal) and continue to hold the nose
down. Although this sounds drastic, the result is a rather graceful and almost slow motion
safe descent from high altitude.
BANK AND YANK -- If you've ever attended a slope race and wondered how a lot of these
guys are able to tuck into such tight turns after blasting along the ridge at virtual
hyperspeed, keep an eye on the flaps. Remember that while the airplane is on its side, the
elevator actually operates as a large rudder. If coupled with the flaps, it will brake and
whip the model into a snug turn basically revolving around its own ends. Steroid-induced
servos, potent wing rods, hefty hinge tape, and one of those "NO FEAR" stickers
on your wing may help, but Gentle Lady's need not apply!
LANDING -- Great landings are almost always a result of good preparation and execution
of a "standard routine" that, through practice, has proven to be consistently
effective. To the contest flyer, this means 90 or better on the tape. To the fun flyer,
every landing should be at least LSF level 1 (less than 10 feet) or better. Once beyond
the novice category, to settle for "somewhere on the field" is really
unacceptable at most flying sites and potentially dangerous to other pilots and
spectators. Like learning to fly with flaps, landing adds another dimension and challenge.
Initially, it may prove to be quite frustrating. Spoilers definitely reduce altitude, but
not always airspeed. Flaps on the other hand, will not only guarantee loss of altitude on
approach, but loss of lift. Usually, by the time you realize you're short of the landing
area and remove the flaps, you're taking a long walk to pick up your glider. For accuracy,
however, in the long run, a flapped sailplane will prove its effectiveness if only for the
substantial increase in control!
Although several articles have been written on the use of flaps for the landing, the
simplest explanation I could find was written by Ben Clerx, Master's and former Visalia
champ, and included as an 'information package' with all his Mako kits. Ben says plan
landing patterns using about half (45 ') flaps. Full (90') flaps should be used only
momentarily to adjust airspeed. Aim for a point about 5-10' in front of the 'spot'. When
you get to that point, raise the nose slightly and flare to the spot. It sounds easy but
it takes practice. The secret to a good spot landing is a good approach. When you roll out
on final (heading towards the spot) you should be lined up on glide path and speed. Make
corrections on the downwind leg and the turn to final, not ten feet from the spot.
WRAP UP -- Although I'm certainly not the sole authority on the many uses of flaps, I
know what has worked for me and most of the contest flyers I've been associated with the
past few years. Personally, I can't think of any pilot who hasn't improved their flying
since transitioning from spoilers. I do know several pilots, however, who will never
improve because they refuse to deal with the substantial learning curve commonly
associated with making the change. For the new flyer, a flap equipped sailplane will open
an entirely new realm of excitement, something comparable to driving a stick shift and
making the plane do what you want it to do rather than the other way around. For the
contest pilot, it's exactly the same and those critical landing points come a lot easier.
Either way, if you're coming up short in fun or landings, flaps just may be the key!
