Free Flight Duration - 2009/08

THE NATIONAL FREE Flight Society’s (NFFS’s) annual
Symposium Report, better known as the Sympo, is a source for the
latest technical information and provides a historical record of the
evolution of FF. But according to editor John Lorbiecki, this year’s
edition is much less technical than in past years.
“If you are afraid of calculus, this may be the issue for you,” he
said.
Following are some of the authors and articles that are scheduled
for publication.
• Doug Joyce: Pusher canard F1C concepts
• Jim Parker: Modifying a mechanical bunter F1A to full electronic
• Jeff Hood: Cutting indoor balsa
• Rex Hinson: The other 60% (noncompetition FFers)
• Jim Gerszewski: Tracker radios—what’s new
• Nick Aikman: A brief history and tips for cutting indoor balsa
• Bucky Servaites: A high-tech engine-starter assembly
• Paul Seren: A Wiki FF Internet site
• Bill Hartill: A lost document on boundary layers
• Brian Eggleston: F1A turbulator theory
• Ron Bennet and Scott Newkirk: Modifying competition engines
• Bob Mattes: .020 engine modifications
• Bob Mattes: National Cup results
• Dan Tracy: A look at NFFS’s future
• Lee Hines: F1A development
• Ken Bauer: Using an altimeter to fine-tune an F1A
• Bernard Crowe: An F1Q and electric primer
Free Flight Hall of Fame inductees for 2009 are Art Ellis, Phil
Klintworth, Fred Pearce, Lee Campbell, Stan Buddenbohm, and the
late Paul MacCready.
This year, the Models of the Year Committee selected nine
airplanes for recognition in the 2009 Sympo.
“We decided that each model should represent advancement in
the state of the art that will likely be widely adapted in the near
future,” said Jerry Murphy, committee chairman. “The test for how
well the new technology works is the model’s competition record.”
The selected models are as follows.
• Gil Morris’s F1C folder that utilizes a
flexible carbon-fiber wing structure to
permit a thin, symmetrical airfoil under
power and an undercambered, flapped
section in the glide. (See the February
2009 Duration column for more
information about this airplane.)
• The Excelsior F1P that Cody Secor flew
to win the FF Junior World Championships
and his father, Randy, designed with input
from Dave Rounsaville.
• Tiffaney’s Coupe, designed by Blake
Jensen and built and flown by Tiffaney
O’Dell. It features a pop-up wing DT.
• Lutz Schramm’s F1D Indoor Rubber
model that employs an all-carbon structure.
• Bernie Crowe’s Noah’s Quark F1Q that
applies off-the-shelf technology to a new
high-performance design.
• Bob Mattes’ Classical Gas, which brings
a unique carbon-capped egg-crate “D-box”
construction to the Classic Gas event. The
model also features a molded wing spar
and screw-adjust stabilizer tilt.
• Two Indoor Hand-Launched Gliders:
Nifkin by Rob Romash and Pelicatoo by
Jim Buxton. Both broke the quartercentury-
old Category II record on the same
day. The two models represent major
breakthroughs in Indoor Glider
technology.
• Chris Starleaf’s scale B-47 that utilizes
multiple rocket motors. Coincidentally,
Phil Klintworth, a Hall of Fame honoree,
worked on the full-scale B-47 at Boeing in
the early 1950s.
You can order your 2009 Sympo from
NFFS Publications Services. The price is
$35 for NFFS members and $40 for
nonmembers. Postage is $5 within the US.
Postage for orders from Mexico or Canada
is $9. Check or money order only is
accepted on domestic orders.
For more information, contact NFFS
Publications Coordinator Bob Stalick.
Free Flight Forum Report: This year
marks the 25th anniversary of the Forum
series that the British Model Flying
Association’s FF members produce each
year. As its name implies, the Forum
Report is a compilation of papers that are
presented at an annual meeting.
As is this year’s Sympo, the 2009
Forum is focused more on practice than
on theory. I didn’t spot a single equation.
Chaired by Mike Evatt and edited by
Martin Dilly, the 2009 Free Flight Forum
includes 13 articles covering a wide range
of topics, from model construction to
flying-site availability. Lindsey Smith’s
paper provides a brief history of Rubber
Scale models and includes plans from
World War II-era kits.
Trevor Grey’s article about brushless
motors includes their advantages and
disadvantages, propeller efficiency (bigger
is better), and timers. He even describes a
simple mechanical brake, to assure reliable
propeller folds.
Mike Woodhouse describes his
experiences as British team manager at the
2008 European Championships. Much of
the planning process would carry over to
any type of contest.
It’s focused on British airfields, but
Chris Strachan’s article about sharing
flying sites with general aviation bears
reading by anyone who is interested in
flying site availability.
Also with a British focus, “A Brief
Look at Contest Entry Trends Over the
Last 20 Years” by Phil Ball deserves to be
read in the US. One graph shows how total
entries and entries per event have
decreased at almost exactly the same rate
as the number of classes have increased.
The British, as do the Americans, fly a
large number of model classes in addition
to the FAI events.
Radio DT is the topic of two papers.
Trevor Grey details the policy decisions
facing rules makers and contest
administrators, while Chris Edge examines
the practical aspects of installing and using
a system. Radio DT uses a brief coded
signal, similar to a garage-door remote, to
activate a model’s DT. It is especially
useful for small-field testing.
Construction articles in this year’s
Forum include Ray Monks’ article about
rolling F1C and F1J tailbooms using
carbon cloth. Phil Ball offers step-by-step
instructions for making carbon-capped
ribs.
Basically, a thick block of balsa is cut
and sanded to airfoil shape, unidirectional
carbon is added to the top and bottom, and
individual ribs are sliced off deli style. For
the undercambered aft ribs on F1A
Gliders, Phil laminates the block from
thinner, prebent sheets so that the wood
grain follows the curve of the lower
surface.
For quicker ribs, Leon Cole details the
use of laser cutting. Mark Croome shows
how he makes lightweight D-boxes from
Rohacell foam sheet. He heats the 1/16-
inch-thick material on an electric griddle
and then bends it around a form.
Roger Wilkes provided two articles;
one details his “Torqueback” system for
F1B and F1G Rubber models. Using
motor torque to control auto surfaces has
been used off and on for many years, but
has more recently been supplanted by
mechanical or electronic timers. However,
using torque rather than time has the
advantage of automatically adapting to
variations in rubber quality.
This system utilizes a chrome-plated
rear peg that rotates through 16° as the
motor unwinds. A spring attached to one
end of the peg counteracts the torque; the
other end of the peg moves a pivoted
carbon-rod lever. The other end of the
lever directly moves the wing TE up
during the motor burst. (See the sketch.)
Variations include differential wing
movement (wing wiggler) and flaps.
Roger’s other article shows a variety
of wing and stabilizer structures for F1B
and F1G models that combine balsa and
carbon rods and tubes in unusual ways.
They are not the now-familiar composite
structures with molded carbon-fiber Dbox
and carbon-capped aft ribs.
One stabilizer structure consists of a
balsa front section, carved out for
lightness, connected with carbon rod back
to a carbon-strip TE. The covering
provides the aft airfoil shape. (See the
sketch.)
An F1B wing structure uses a largediameter
carbon-tube spar for torsion and
bending strength with balsa riblets and LE,
providing the desired airfoil shape from
the spar forward.
The aft portion of the wing consists of
a bent carbon micro tube on the top
surface and a bent carbon-balsa-carbon
laminate forming the bottom surface. Both
connect to a carbon-strip TE. Warrentruss-
style diagonal bracing in between
helps preserve the aft airfoil’s shape.
The 2008 Forum Report is available
from Martin Dilly. The price, including
airmail postage to the US, is £14.00
(which is approximately $21, but the
exchange rate fluctuates daily).
Make checks out to the “BMFA F/F
Team Support Fund.” Since checks must
be in pounds sterling only and drawn on a
bank with a branch in the United
Kingdom, it’s much easier to pay by credit
card.
Back issues of Forums are available.
The 2008 edition is also available from
NFFS Publications (Bob Stalick). The
price is $25 plus $5 postage. Checks or
money orders can be used only on US
orders; international orders can be paid
for by credit card, but a service fee is
charged.
Rubber Bands: One of those little details
that can fail at the most inopportune time
are the rubber bands used to attach wings
and tails on many models. Rubber bands
are an easy, light way to attach the
surfaces to the fuselage and provide a
measure of safety in the event of a crash;
the bands break rather than the model.
For wing and stabilizer hold-down bands,
it helps to standardize on a few widely
available rubber-band sizes rather than
inventory different sizes for each model. To
be effective, rubber bands need to be tightly
stretched. Hooks should be located on the
model so that standard-size rubber bands can
be used at the optimum stretch.
However, the optimum stretch is not
necessarily maximum stretch. A new size
8 band measures roughly 3/4 inch long in
its relaxed state and will stretch to nearly
5 inches. But after a few minutes at
maximum stretch, it provides significant
tension only in the 4- to 5-inch range.
Allowing the band to completely relax
for a few minutes improves things a bit,
just as allowing a rubber motor to rest
between windings improves performance.
But that means removing and then
128 MODEL AVIATION
reinstalling wing and stabilizer bands
between flights, which is way too much
trouble.
Instead, space hooks so that the band is
stretched less than the maximum but
enough to provide the needed tension.
Something approximately 80% of
maximum, or close to 4 inches, for a size
8 band works for me.
The effects of heat, sun, and time will
cause wing and stabilizer bands to weaken
during a day of flying, which can have
serious effects. Weaker bands can allow
wings to lift or shift slightly, especially
under power, affecting trim. Weakened
rubber bands may not have sufficient
strength to pull the stabilizer up on DT,
resulting in a lost model.
Prudence suggests that you replace
bands several times during the day.
Discard used bands. It is a good idea to
use at least two bands for wing or
stabilizer hold down.
Be sure to pay attention to the hooks to
which the rubber bands attach. A wire
hook should have the exposed end round,
to prevent nicking the band (or your
finger) when installing it. Hooks should
be well anchored, to prevent their pulling
loose.
If possible, use a thin-plywood
reinforcement to anchor the hook. Then
sew it in place with Kevlar thread and
apply epoxy.
Consider using dowels instead of wire
for hooks. Thin-plywood washers can be
combined with the dowel, to maximize
gluing surface on sheet-balsa structures.
For gas-model wing mounts, use a
spruce strip set between the top of the
balsa pylon and the wing mount and
extending fore and aft. Add a piece of TE
stock on either side for reinforcement.
Make sure to slightly round the projecting
spruce strip’s edges, to avoid cutting into
the wing hold-down rubber bands. MA
Sources:
NFFS
www.freeflight.org
NFFS Publication Services:
Bob Stalick
Box 1775
Albany OR 97321
[email protected]
2008 Forum Report:
Martin Dilly
20 Links Rd.
West Wickham, Kent BR4 OQW
UK
[email protected]