The speed of aileron response is
largely a matter of personal taste although it is worth bearing in mind that in turbulent
air you may need enough response to level the wings rapidly.
With regard to the all important
turns you need to strike a balance between having too little movement making you start the
turn early thereby missing out on the best lift and having so much that you can turn very
late but are creating a lot of drag.
Snapflap is the mixing of the flaps
with the elevator. Normally the mixing will involve up elevator producing an amount of
down flap and vice versa. I say normally because if certain flight characterises are
required (such as damped pitch response) there is nothing to stop you experimenting with
the direct opposite of what I will be discussing.
From the mixing we hope to gain
tighter, faster turns and better inverted performance. In the case of 4 servo wings,
whether or not the ailerons will be mixed 100% with the flaps (i.e. the whole trailing
edge droops equally) is down to the model. My experiences have been that the more cambered
the section the less outboard aileron you want acting as flap. The reason is that to have
the outboard surfaces moving fractionally less than the inboard ones mean that you are
less likely to induce a tip stall and associated flick.
Setting up planes with the optimum
amount of snapflap is simply a case of evaluating a number of different settings, although
it is complicated slightly as conditions and ballast can also have an effect. As a general
rule the more flap you have mixed with the elevator the tighter the model will turn, up to
the point that you are adding too much drag. This becomes apparent when the plane will
still turn in a small radius but will scrub off lots of speed. You are looking for the
compromise between the tightness of the turn and the speed retention throughout the turn.
The factors governing this are numerous. Wing section, wing loading, moment arms, tail
area/thickness/movement, wind direction, airspeed, flap areas, flying style, aspect ratio
etc. So go practice!
As a cheat you may want to start at
1.5 mm down flap with full up elevator on an RG15 60" model and around 3 mm on a 3 m
The up flap mix with down elevator
is far less critical. Generally for aerobatics you are only looking at a few mm to
de-camber the section and for racing many people, myself included, use none at all.
It is very tempting to use computer
TXs to show that you can waggle everything but it is worth bearing in mind that it is
probably better to have too little elevator/flap mix than too much.
One final thought is don't be
afraid to experiment. The aileron side of things is pretty straightforward the real
potential gains are when you pull in the up elevator to turn the plane so watch, think and
Some areas worth experimenting with
on the set-up front, try putting your snapflap on a curve so that all the flap comes in
at, say, 1/2 the available up elevator movement. Try different set-ups for different lift
conditions. Consider more snapflap for liftier days when ballast is on board and less when
the lift is marginal and/or the wind is not square to the hill.
If you are tinkering with the model
itself you could consider a larger than "normal" tailplane to give you a safety
margin when conditions are choppy. Alternatively you could try a thicker tail section,
maybe 10%. Turbulators on your tips to cure that flick?
One of the things I enjoy about
slope racing is the analytical side of getting the best from a plane in varied conditions
and setting a model up to do this is a skill, the same as flying the model in different
conditions is. Like all skills of any merit it takes time, experience and sometimes help
to feel confident in what you are doing.
I would welcome feedback on this
one as I don't recall reading any other views on what has all too long been regarded as a
black art. So mail me
BTW you'll have noticed I've
steered clear of the CG debate, go fly and find it yourself!