Setup - Tips and tricks of the trade!
Here is a few tips and tricks on how to setup a Pike model.
They will not help you win a contest but will give you a few hints on how
others do things.
How to set up a full house sailplane
There is a lot of FAI models out there. I am sure that
there are many models out there that is not used to their full potential. This
article might help slightly to get them work that air a bit more.
There are a lot of ways to set up a model for the classes F3F, F3B and F3J. So
do not see this as a recipe on success but maybe a good guide on the way. What
functions are we after? I reckon you the pilot have got yourself a modern
computer radio and a plane with 4 servo wing. I see this as a minimum to have
fun on the flying field... These are the controls we are after: Aileron,
elevator, rudder, brake (called butterfly) and flaps (camber).
Aileron:
We wish aileron on all wing surfaces. To fly only thermal one can only use the
outer surfaces (ailerons). But as soon as we are on to F3F/F3B we want apx
half the amount aileron deflection on the inner surfaces (flaps).
Differential: To make a model turn better in a given speed we need to use a
function called differential. This function (or mix) makes the ailerons and
flaps go less down than up. Differential can even make the model yaw every
time we use the aileron stick. The result is a kind of rudder. You will most
likely want different differential at different flying speeds. As a simple
guidance for thermal flying: 1/3-1/2 down versus 1 up. Speed and acro: 1/2 or
equal down versus up. In speed acro you want the model to roll straight in the
given speed. In F3F some want the model to yaw in before the turn but mostly
this is done by rudder.
A good launch is important.
Elevator:
As a main rule you want equal amount up elevator as down. But it is so that CG
(central of gravity) and construction have something to say here. It is also
so that a more aft CG should have less elevator throw. Be aware of this as one
often changes the CG in different tasks. If the model gets very sensitive but
one still wants the throw you can: Have less down elevator or use exponential.
Exponential makes less throw around "dead-stick" but will give you full throw
with the stick in either position. Normal exponential is 20-40%. The amount of
throw on a model can me set at the following way. Fly as fast as you think you
will fly with the model in any given situation (a good speed or a super
launch). The model should turn hard without tendencies to drop a wing or not
follow the flight path. In competition most pilots wants to be able to use the
whole stick movement while turning. You then have better feeling of the model
in accordance to the stick and thereby better control. There is one more
function/mix that have to be considered together with the elevator throw.
"kick-flap" is a mix that allows all surfaces to move together with the
elevator. All surfaces down = more camber/lift and thereby same as elevator up
throw. And off course opposite. In some conditions (distance downwind turn)
one can also use the opposite to give more speed thru a difficult turn. Use
this mix wisely as not all models/profiles/hinge lines will give you a benefit
of this mix. On a new model I would always start without this mix.
Rudder:
The rudder is worth a chapter for itself. Sadly there are not many pilots that
have learned to use the rudder. The rudder is there to keep the model in the
flying direction and preventing it from yawing. The best way of understanding
the rudder function is to take a flight with a full size sailplane. In the
cockpit glass you will see a wool thread just above the pilot. This shows the
wind direction compared to flying direction. All other cases than that the
thread goes straight backwards is big loss in energy and thereby
speed/altitude.
T or X-tail rudder: Equal to each side but not more than that it actually
works. Too much and the rudder will only slow you down or make it tip-stall.
V-tail rudder: Equal up/down but also here there can be some differences in
models. If the model sets its nose down much you can reduce the down slightly.
But not too much as it will give you a wrong feeling when circling.
Combi-switch: Sadly there is a mix that is called combi-switch that many finds
on their radio. This is often miss-used. It will give you rudder movement when
you use your ailerons automatically. This is fine coming into a turn but will
have the opposite effect compensating or coming out of the turn. So turn this
mix OFF. There are two times you might want it to be on: - When flying F3F
competition and you are a good pilot you might want it but only slightly as a
help. Any compensation of flight path between the bases will result in wrong
input. - In the launch mode it can be used if you use a separate launch mode
on your radio (so that it is off in any other flying).
Equipment in good shape is important. Dont let it sit in the
garage during the winter.
Brake:
This I would like to call butterfly or crow on our sailplane models. When
flying the brake is like an motor for us. The butterfly function should be on
your throttle stick. Forward full speed and back for brake. With full brake
the following should happen: Ailerons slightly up (5-10mm), flaps as far down
as possible and elevator slightly down as compensation for the increased lift
in the wing. There is no "hocus-pocus" with butterfly but often a little work
to get the correct elevator compensation. Even full size airplanes use
butterfly. Compensation on butterfly should be dialed in at both half and full
brake. The model should put nose slightly down to maintain airspeed. Often a
model will need more compensation on half brake than full. If not possible to
set two settings then reduce the flap to 60-70 degrees. Mostly this is
sufficient to give enough brake anyhow.
Flaps:
3 kinds of flaps are wanted and also the kick-flap as mentioned in the
elevator section. When I write about flap I now mean all surfaces on the wing
not only the "flaps". Camber is a good word and means changing of airfoils
lift.
Start camber: When we start with winch/runners one needs to have a bigger
camber / more lift on the wing than the model is produced with. This because
the model will work as a kite not a flying model. Before the zoom we want to
use the energy captured in the line and turn this to "flying energy" = speed.
Dependent of model type and condition you will need 10-30 degrees launching
camber. The launching camber is also dependent on where the hook is and the
position on the elevator. We might need to set up different settings for
different type of conditions. In strong headwind you need less camber and the
hook seated so that the model will increase the tension on the way up. You
will hopefully hear the line tension and speed increases on the way up. Mostly
pilots have the same settings for normal conditions and strong wind. In poor
launching conditions (wind from the back, high altitude or more ballast) you
might need more launching camber and the hook should not be to far back. In
these conditions we mostly try to use as little line as possible and this is
done by line tension not speed. As a general rule you want equal camber on
flaps and aileron surfaces. Many use less on the ailerons but this is wrong
and can make your model "yaw" on the line or maybe tipstal. If the hinge line
on the aileron surfaces are much less then try to figure out if the degrees of
camber is the same. So aileron camber can be less if the angle is the same.
The hook is normally seated just in front of the pressure center of the wing.
The pressure center will alter much when you add camber... The CG has almost
nothing to do with hook placement. 50-100kg of tension will take away any
effect of CG. You will want the model to rotate heavy just after the throw.
With too far aft hook the model will over rotate and "pop-off" giving you a
relaunch. Too far back will also make the model be "forced forward" in the air
and your winch will "eat" valuable line length. Always start with recommended
settings from the producer or a pilot you think knows better. Add/reduce
launch camber until you are satisfied in one type of conditions and write this
down. 5mm altering of the hook can make as much as 50m launch height so use
much time on launch practice in different conditions. A good launch on a F3B
winch in calm conditions is 230-250m. In good conditions one can achieve
300-350m and the opposite in backwind one can have 180-200m or even only 150m
sometimes.
As a main rule one want just as much launch camber on ailerons as on flap. But
on some models you want slightly less as the hinge line is different. The
point is that we do not want wash out on a wing in launch as this is only
drag. We want the whole wing to fly all the time. I must take hook setting at
the same time because camber and hook works together. The hook should sit just
in front of the pressure point in the wing and this will change a lot with
different camber. Most often we set the hook just in front of the CG but as
mentioned it can vary a lot. Since the pressure point in different settings
normally is not given one should start with the recommended setting or make
contact with someone that have flown the same model for a while. Launch
camber, hook placement, etc. is a difficult issue to handle and I cant give
you a 100% correct answer as all plans are different. But a few facts must be
stated: More camber = more backwards hook. More start flap = you go slower up
the line. You want to go as steep climb as possible but with the highest speed
possible. At the same time you want to stretch the line to build up a bungee
effect for the zoom. The more stretch - the better height you will get.
Launch camber is normally set with a switch and some like to adjust it by a
lever previous to the start (to set for different launching conditions. The
switch needs to be with easy access and equal on all your models so that there
are no hesitation when you switch it off just before the zoom.
Speed flap: When flying speed and distance we often want a faster airfoil. How
much depends on the conditions you are flying in and type of model. It is done
by all surfaces on the wing goes up 1-5 degrees. Mostly on only uses one
position or neutral.
Are you ready to win this round ???
Thermal flap: When flying duration and partly distance we want to change the
airfoil so that it becomes more lifting (1-10 degrees). This is done by all
surfaces on the wing is going down. How much is depending on a lot of factors.
As a main rule we want more camber the better air you are flying in. For
moving around you want as little as possible (in most air conditions but this
might change at altitude). When you find the lift you use as much as possible
but not so much that the model becomes "low tail" or critical to fly. Most
pilots adjust thermal flap by a switch or maybe two. Some likes to also adjust
it on a lever. But mostly you want as few switches as possible. The difference
is anyhow mostly on the pilot control.
So how many switches/settings are we up in now ?
Start camber: 3 positions - launch/neutral/much wind
Duration: 3 positions - Strong thermal/neutral/small thermal
There are many solutions to setup of switches and often each radio provides
"their ultimate" solution. For the most advanced radios I can supply my own
setup that I think works fine:
Only two switches. One 3 point and one 2 point switch seated on top left of my
radio. I use these switches to control my flying modes. So many things happen
at the same time when I switch one of them.
- Switch one have the following functions: Forward - speed mode, Middle -
neutral flying, Backwards - Launch mode.
- Switch two have the following: Forward - switch one is working, back and you
are overriding switch one and are in thermal mode with positive camber.
All camber can be adjusted by my lever.
Hope all this txt gave you some new ideas. Remember one can always develop
further and all needs to find "their setup".
Jo Grini
