So What's So "Different"
About the Delta Vortex?
by Bruce Tharpe
Modelers have had a long love affair with delta-winged aircraft.
Deltas really came into their own during the early days
of R/C pylon racing, when there was an open class for any
type of design. Because deltas are a naturally "clean" configuration,
they enjoyed a lot of success in the speed-driven world
of pylon racing. Since then, it seems, delta wing designs
have been reserved for the simple pursuit of speed. Many
of them have been published in magazines over the years,
as well as a number of kits. The common thread with most
of them has been "Look how fast this bugger can go!"
Not that there's anything wrong with that! Speed is cool.
I enjoy watching fast models make low flybys, and I've flown
a lot of fast models. The adrenaline rush is great, but
it does wear off. Like most experienced pilots, I can handle
fast planes but ultimately return to slower, aerobatic models
that are easier to see and enjoy in a more relaxed frame
That's where the Delta Vortex comes in. I've always loved
the shape of the delta wing, but have also wondered why
it's been restricted to small, fast, speed demons. Why not
big and aerobatic? Why not make a delta that would fit into
the mainstream of the sport modeling spectrum? My basic
design goals were to create a delta with lots of wing area,
keep it very light, and make it fully aerobatic without
any concern for top speed. That's the basic difference between
the Delta Vortex and all of the other deltas available now.
You can take your Delta Vortex to the field and fly it just
like any other sport model you've flown lately. Fire up
the front-mounted engine, taxi out, fly through all of your
aerobatics, shoot a few touch-and-goes, land, and taxi back.
The neatest part is watching a big triangular-shaped object
do all those things!
Touch-and-go lovers will really love the Delta Vortex. Since
deltas, by nature, can fly at very high angles of attack
without stalling, they tend to land with the nose way up
in the air (think Space Shuttle). The main gear struts on
the Delta Vortex prototype had to lengthened after the first
flights because the rudders scraped the ground on each landing.
The main wheels are positioned so that after touchdown,
you can rollout with the nose held high until the last bit
of forward motion bleeds away.
For some reason, one feature that is typically omitted from
deltas is rudder control. Well, if you like aerobatics,
you need a rudder - and the Delta Vortex has two! They're
great for doing big, graceful stall turns. Knife edge is
trickier, but possible. Deltas don't like to stall, so snaps
and spins with a delta are different, but spectacular, in
their own way. This thing does a beautiful flat "spin" with
full throttle. It's hard to describe, because I don't believe
it's a true spin; it actually seems to be flying in tiny
circles around one wingtip. Chalk up another pleasant difference
for this delta.
One last word on speed. Even though it wasn't designed for
speed (the airfoil is four inches thick at the root, the
tricycle gear and engine hang in the breeze, and the servos
and control linkages are all exposed on the bottom side
of the wing for simplicity), the Delta Vortex still scoots
right along. With a .90 in the nose, it probably does 80
m.p.h. or so, I'd guess over 100 in a dive. That's pretty
fast for a sport model, but much slower than a Quickee racer.
And since it's so large, it doesn't disappear in the blink
of an eye.
If you've read my other articles, you know I'm not a big
fan of overpowered models. Still, some models deserve more
power than others, and this is one of them. In addition
to being clean, deltas are inherently strong, due to their
low aspect ratio and truss-shaped structure. And since it
looks something like a jet, it would be disappointing to
have anything less than jet-like performance. A good .60
two-stroke will fly it with authority, but won't give the
out-of-sight vertical performance of a .90. I've found it
easier to land with a .60 because it slows down better with
a smaller prop.
Normally, you would need at least a 1.20 four-stroke to
equal the power of a .90-size two-stroke engine, but you
may have noticed that I only recommend up to a .91 four-stroke.
There are three simple reasons for this: weight, prop clearance,
and vibration. The Delta Vortex builds nose-heavy, so it's
important to choose an engine with a good power-to-weight
ratio. Some designs are perfect for four-strokes, but the
Delta Vortex is more suited to the smooth power of a two-stroke
Besides an engine, you will need an engine mount, 16 oz.
fuel tank, fuel line, radio, three 3" wheels, and three
to four rolls of covering material to complete this kit.
Elevon mixing is required; most radios these days have this
feature. If yours doesn't, you can use a simple aftermarket
electronic mixer. Standard servos are okay for the rudders,
but heavy-duty, ball-bearing servos are strongly recommended
for the elevons. You'll need five or six servos, depending
on whether you use a single servo to drive the rudders or
duals. With dual servos and the right computer radio, you
can program the rudders to both move outward, using the
flap control on the transmitter, to serve as airbrakes.
At first, many modelers think the Delta Vortex utilizes
a foam wing, but it doesn't. It's a traditional design with
ribs and spars, sheeting and capstrips. The kit features
balsa and ply-wood parts that are machine-cut and sanded
to their final shape using templates for accuracy. There
are no die-cut (die-crunched) parts in BTE kits. The greatest
thing about this kit is that once the wing is built, you're
practically done! The fins and rudders are solid sheet balsa,
and there are separate hatches for the fuel tank and radio,
so installation, inspection, and maintenance are no problem.
Thanks to hundreds of satisfied customers, the word is spreading
fast about the quality of our kits. At BTE, our sole guiding
philosophy since the very beginning has been this: Building
a model airplane should be as enjoyable as flying it. That
means top-quality materials and hardware, parts that fit
without fudging, nicely drawn plans, and thorough instructions
that are easy to understand.
In the Greek alphabet, the capital letter D is named delta.
In the engineering world, the term "delta" is used to signify
a difference. In the model airplane world, most sport modelers
that I know enjoy bringing something "different" to the
field. Well... here's your chance!
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