Slope Soaring Tips for Beginners
by Akkana Peck
My husband and I are learning to fly slope gliders (after already
flying electric-powered model airplanes). I didn't find much on
the web about learning to slope soar, so I'm writing this page as
something that might be helpful to new slope soarers.
between slope soaring and other types of flying
Of course the obvious attraction of slope soaring was the lack of
mechanism: no noisy motors (not that modern electric motors are very
loud), no complicated winch setup like the thermal gliders use,
relatively small and simple airframes. It has a purity, as much
as anything requiring $150+ of radio equipment can seem pure. But
the first thing we learned was that another difference is that it's
much more physical than other types of flying. First, there are
no slope sites anywhere near a road. If you live very near the
ocean, you may have ocean cliffs with parking lots nearby, but anywhere
inland, you'll probably have a pretty significant hike to get to
anywhere with lift. I knew the slope sites had a little bit of
hiking, but when I visited them I was impressed with the significance
of the climbs these people were doing carrying equipment. People
who do other types of R/C flying mostly don't seem like they're much
into physical activity.
That was part of the attraction, for me: Dave and I like to hike
anyway, and spending all our time standing in a field flying electric
planes was making it hard to get much exercise. But be aware of
it: visit your local slope sites before purchasing a glider to make
sure you're up to it.
We didn't realize until later that hiking to the slope site is only
part of the exercise. Once you're there, you'll also expend lots
of energy chasing up and down the hill to retrieve your glider when it
lands in unexpected places. Or you can try discus-launching
flat site, in which case you'll be running halfway across the field and
back every minute or so to retrieve the plane.
Rule 1 of slope soaring: If you build a glider, there will be no
wind ever again.
ordered our mini-Weasels
partly because it had been extremely windy, so
windy that most of our electric planes were having trouble
flying. We finished them in a few days, tossed them in the car
and drove up to a local site known as Windy Hill (that's the name of
the park, not just a nickname given by glider people -- it's always
windy there.) It was dead still. We spent a frustrating afternoon
tossing our Weasels down the slope, or standing atop the hill waiting
for a tiny gust.
A few days later, we went on a trip to visit friends in Arizona.
Our route took us over Pacheco pass, a known wind tunnel with a wind
power generation station, and over Tehachapi pass, which has an even
bigger fleet of windmills. We stopped at roadside rest areas with
the Weasels. They were still. The windmills were barely
turning. Same story at other roadside rest areas in usually windy
areas, like California's central valley.
After we got home, we hovered over the weather pages. There's a "live
wind map" page for the bay area which shows directional arrows
supposedly indicating the wind direction everywhere. But it turns
out that they don't have very many wind-reporting
stations, and in particular, they don't have any in the hills where
we normally hike. So the arrows are all interpolated. More
than once, we saw nice green arrows over our hiking areas, and rushed
up the hill to find dead calm along the ridgetops.
Corollary 1 to Rule 1: When you finally get wind, it will be too
After two weeks of dead calm with a new slope glider, you think that
there could be no such thing as too much wind. Until you find
yourself on a hilltop with your new carefully-built slope glider,
trying to stand up in the 20mph gale, and contemplate tossing your
precious toy into that and seeing it swept away forever.
Corollary 2: or in the wrong direction.
We drove over to the coast, where there's always an onshore wind.
Not that day -- the wind was actually blowing from the land out to
sea. I didn't think that ever happened. None of the cliffs
point that way, either; they all face the sea. Dave thought that
just having wind at all might be enough for slope soaring, but it
seem to work well unless the wind is blowing at least partially onto
so it gets forced upward.
We ended up driving up the coast about 30 miles, stopping at every
beach, until finally we found one that had a little cove with a hill
that pointed in the right direction. Then we had a great time --
really our first slope experience.
Corollary 3: or with no recovery zone.
Actually, we did find a few cliffs with the wind blowing onto them --
but note the word "cliff". Experienced glider pilots can toss a
slope glider off a cliff and expect to bring it back and land it at
their feet, but when you're learning, you want a place where you'll be
able to hike down and retrieve it.
What to do with your slope glider when there's no wind
and I discovered "Weasel hiking". We'd drive to a trail in the
hills hoping for wind, hike up to the highest hilltop, spend a little
time there tossing our gliders out into the dead air. Maybe we'd
hike around (we like hiking anyway, though it's nicer when you don't
have to carry a heavy transmitter everywhere). But the hike back
down turned out to be fun. See, even when you don't have wind,
you can fly a fair distance if you don't mind landing downhill from
you. So you toss your glider as high as you can, then fly it down
the trail as far as you can, trying to land somewhere near the trail;
hike down to it, then toss it again. You can actually get in a
reasonable amount of flying this way, and learn something about the
characteristics of your glider.
This may not work quite so well if your first slope glider is large and
Things to watch out for while glider-hiking.
our first windless outing, I got the clever idea that I'd climb up on
Eagle Rock (maybe 15' above the trail) and toss the glider off the
rock. But my launch technique was pretty inconsistent, and the
Weasel flopped nose-first in the bushes at the foot of the rock.
Unfortunately, the bushes turned out to be poison oak. I had to
carry the Weasel, by the tip of its fragile tail, all the way back down
the trail (no more flying for me that day!) and carefully wash it off
with Simple Green as soon as I got home. Be aware of the foliage
around you before you throw.
(It also helps to put some brightly colored surfaces on your plane,
especially if you fly in places will tall grass. Can you find
Weasel in this photo?)
Other things to watch out for: trail visibility (don't throw if you
can't see the trail for a good distance ahead), hikers who might get
hit (if you're new and your control isn't so good, you might hit
someone), potentially dangerous trail users (like groups of hikers with
kids who might run over and damage your glider), cliffs, poo
(especially on equestrian trails), ticks, snakes, and other denizens of
the tall grass through which you search to retrieve your plane.
When you finally find wind
Huzzah! You're at a likely ridge with the wind blowing in the
right direction, onto the ridge. Now what?
Watch the birds.
My first really successful (staying up for a while, being able to do
aerobatics) slope flight was at a launch point I picked because I saw a
whole flock of swifts playing just off the hillside. Sometimes a
ridge doesn't look that different from any other place, but if you see
a hawk circling to stay above a particular point, or a flock of swifts
playing there, you know it's a good spot. Hawks and swifts are
at finding lift than you'll ever be.
Launch into the wind.
Our Weasels, at least, launch much better if you throw them into the
wind, even if you'll be flying along the ridge line once you're in the
air. This takes some nerve at first, since you feel like you're
throwing the plane out across the lift into the zone where it'll drop
like a rock into the valley below. And sometimes it might
(remember what I said about a recovery zone?)
Follow the ridge line.
A good slope soaring hill usually has a cliff or steep area aligned
more or less facing the wind. The wind hits the cliff and gets
directed upward. You need to stay above that area -- so once
you're in the air, turn to fly crosswind along the ridge line, then
turn fairly sharply and fly back the way you came.
Turn into the wind, away from the hill
When you're flying crosswind along the slope, turning into the wind
will give you some additional lift. (This is part of the more
advanced technique called "dynamic
soaring", or DS.) So when you make your turn to fly back the
way you came, turn away from the hill, not toward it.
This can be psychologically difficult for the novice. Turning
toward the hill is safe -- if something goes wrong, the plane ends up
fairly near where the pilot is standing. Turning away from the
hill, into the wind, is unsafe -- if something goes wrong, the plane
ends up waaaay down the hill and you have a long hike to get it back.
Trust me. If you want to stay up and in the lift, work up your
nerve and turn into the wind.
Watch the plane: don't assume you know where the lift is
Slope lift seems really straightforward. The wind hits a hill, it
bounces upward, the lift is right above that, right? But it's not
so simple. Sometimes the lift will be better above a cliff,
sometimes above a gentle slope; sometimes it'll be a bit downwind of
the cliff edge, other times out from the cliff. Sometimes you'll
be getting great lift at one point along a ridge, then suddenly the
lift will die, even though the wind hasn't stopped, but fifty feet to
the left, a spot that didn't have lift before will suddenly come an
elevator. Maybe experienced slope pilots understand all this, but
I don't. Watch what your plane does, notice when it takes off and
learn how to stay near that spot, and notice when it stops climbing and
be ready to go hunting for lift somewhere else.
And watch the birds (swifts and hawks). They play in one spot for
a while, then move on. And if you fly with other glider pilots,
watch them, too. You can help each other by calling out where the
lift is good.
Trade off between speed and altitude, and use ground effect.
Airplanes (all planes, not just slope gliders) can trade speed for
altitude, and altitude for speed. (This comes from the Newtonian
physics concept of the equivalence of potential and kinetic
energy. Altitude, combined with the earth's gravitation, gives
you potential energy, mgh; speed means kinetic energy, .5*m*v2;
and they can be traded for one another. This is how a
rollercoaster operates, too.). Knowing about this can be useful:
for instance, you can dive below the edge of the cliff and not be in
any risk, as long as you have enough speed to trade that kinetic energy
for potential energy and climb back up. Play with this
(preferably when you're already fairly high) and get a feel for it: you
can use it to your advantage.
Ground effect is the phenomenon that when an airplane is flying very
close to the ground, it can fly faster and experiences more lift than
when it's high in the air. (The effect is caused by a reduction
fo turbulence from the airplane's wingtips. Some birds, such as
pelicans, use ground effect very effectively as they skim just above
the water.) One way this becomes useful in slope soaring is when
you have a gentle slope above you. Remember I said to make your
turns away from the hill? It sometimes happens that you make a
turn toward the hill instead, fly out of the lift zone, and start to
sink toward the hillside. Don't panic: if you approach the
hillside smoothly, you may be able to use ground effect to skim along
the hillside, gain speed, then climb out, turn back into the wind
(which gives you lift, remember DS?) and make it back to the lift zone.
How much elevator can you use?
I don't know if other slope planes exhibit this effect, but the mini
Weasel, when you give it too much aileron, porpoises, flying a
sawtooth pattern as it repeatedly stalls and recovers. I found
this helpful when feeling out how much elevator I could give it.
Get familiar with your trim tabs
The right trim varies depending on what the wind is doing. If
you're getting good lift, you might want to add a couple of notches of
up trim to take advantage of that (without having to hold the stick
back constantly). If the wind is blowing you back and you want
the glider to penetrate better and stay in the lift zone, you might
want a few notches of down to help with that. Adjusting up and
down as the conditions change can make flying more fun.
... as I learn it! I guess that means I'd better go out there and
do some more research!
Happy soaring ...
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