Asked Questions About the Delta Vortex
Answers by Bruce Tharpe
Q: Can I install retracts in the Delta Vortex?
A: Yes, but the DV is designed with fixed landing gear,
and no instructions for retract installation are provided
with the kit. Lots of modelers have done it, both mechanicals
and pneumatics. Remember, that wing is four inches thick
at the root, so there's plenty of volume to work with. Check
under Resources for a link to more information.
Q: Right now I'm flying a Venture 60 (or a Super Sportster,
Four-Star, Tiger 60, Somethin' Extra...), do you think I
can fly the DV?
A: Yes! The DV is not as fast or "wild" as it
looks. I think any pilot that's comfortable with a 4-channel,
low-wing, aerobatic sport model will have no trouble flying
Q: Will it do a knife edge?
A: If you're good enough it will. I say that because there
is a lot of roll coupling when you slam the rudders, so
it takes a lot of aileron correction in knife edge. If you
have a computer radio, you can program some mixes help with
this. Even without a fuselage, the DV seems to maintain
altitude on edge if you can keep it there.
Q: How about snap rolls?
A: Nope. A true snap roll requires the model to stall, and
delta wings typically won't stall. Same goes for spins.
The DV won't do a true spin like a "normal" airplane,
but it will do a Delta Spin, which is something a "normal"
plane can't do. You gotta see this maneuver to believe it!
for info on the Delta Spin.
Q: Some of the reviews say the DV is prone to tipovers
on the ground because the gear is too narrow. Have you changed
anything to take care of that?
A: The first batch of DVs shipped with main gear wires with
the axle bends facing inboard. I thought these were fine
on my prototypes and sort of gave them a jet fighter look.
After numerous complaints about tippiness, I simply changed
the wires so the axles faced outboard. That spread the main
wheels a few inches and improved the ground handling tremendously.
All DV kits come with the new gear.
Q: You recommend up to a .91, both 2-stroke and 4-stroke.
How about a 1.20 4-stroke?
A: I don't recommend a 1.20 4-stroke for a couple of reasons.
First, there's an issue with prop clearance, 14" is
about as big a prop as you want to use on this model. There's
also a weight issue. No matter what engine you use, the
DV will come out nose-heavy because of the geometry of the
design. That's why I think you're better off with a lighter,
more powerful 2-stroke. I can report that many builders
have gone with OS Surpass or Saito .91 4-strokes in their
DVs and absolutely love it.
Q: How much tailweight will it take to balance?
A: As designed, the DV will come out nose-heavy and require
tailweight to balance. It could be as much as six to twelve
ounces, depending on your engine. There are two schools
of thought here: "Hey, live with it" or "I
will never, EVER put dead weight in my models!". With
this particular design, I'm in the first school. Frankly,
with all that wing area, I can't even notice the weight
Q: Is there any way I can avoid adding tailweight?
A: Yes, a good number of builders report they've done this.
First, they move two servos from the engine box (steering
and throttle) way back in the wing. That allows the engine
box to be shortened, moving the fuel tank, firewall, and
engine back a couple of inches. This modification coupled
with dual rudder servos and a large, heavy battery pack
in the tail usually results in a perfectly balanced model.
Q: My DV lands good, but not with the nose way up high
like a delta should. How do I get those nose-high, space
shuttle type landings?
A: Your DV is still probably on the nose-heavy side. I show
a one-inch wide balance range on the plans. If balanced
at the front of the range, it probably lands more like a
normal model. Add tailweight (ugh, I know, but it's worth
it!) to bring the balance point aft and your landings will
improve, as will the elevator responsiveness.
Q: Can I put an elevator in the center of the wing, between
the rudders, and just use the outboard surfaces for ailerons?
A: I tried this, with poor results. Use the elevons as designed.
That said, I've often thought about splitting that center
section and having them move in unison with the elevons.
I would use an extra servo on each of these surfaces; you
need the tailweight anyway. The benefit here would be in
hover, because now there would be some aileron and elevator
control in the prop wash. Any takers?
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