130 MODEL AVIATION
THIS YEAR marks the 40th anniversary of the National Free Flight
Society (NFFS): the SIG for all types of FF, indoors and out. This
also marks the 40th Symposium report. This publication’s purpose is
to “Promote and encourage the investigation, discussion, and
documentation of the technical and theoretical side of free flight.”
In many ways the Symposium is a continuation of the Model
Aeronautic Year Book series the late Frank Zaic, one of AMA’s
founders, produced from the 1930s through the mid-1960s. One
thing is certain: the Sympos and the Year Books are invaluable tools
for all serious FF modelers.
The 2007 Symposium report, edited by David Mills of Atlanta,
Georgia, covers a wide range of topics. Following are some of the
authors and the subjects of their papers.
• Peter King and Mike Woodhouse: F1B trimming based on
computer simulation and higher-order trim-set measurements.
• Dean McGinnes: Field-tested flight-log forms and model data
sheets for Gas models.
• Rick Pangell: Structural design considerations for model aircraft,
focusing on the use of composite materials.
• Sergio Montes: Aerodynamic analysis of flat-bottomed airfoils and
their appropriate uses in FF.
• Bob Thoren: Mathematical analysis of the dynamics of discuslaunch
gliders.
• William McCombs: Wing-incidence settings.
• Stewart Meyers: Optimizing electric power systems for Scale
models.
• Don DeLoach: Selecting, building, and flying Nostalgia Wakefield
models.
• Louis Joyner: An historic perspective of Wakefield rules and
designs in the early 1950s.
The Sympo appropriately includes a look at the NFFS’s history
and future, compiled by current president Rex Hinson. In addition,
Paul MacCready, who developed the first successful man-powered
aircraft, details the role of FF in his career and the value of FF
concepts in the future of aviation.
The Sympo includes three-views
drawings and other information about the
Models of the Year, selected by Bill Booth
and his committee. The committee, chaired
by Steve Bruno this year, also selected six
modelers for induction into the NFFS Free
Flight Hall of Fame: George Batiuk Jr., Gil
Morris, Will Nakashima, Lin Reichel,
Eugene Verbitsky, and Jim O’Reilly.
You can order your copy of the Sympo
from NFFS Publication Services, Box
1775, Albany OR 97321. The price is $30
for NFFS members and $35 for
nonmembers. Postage is $5 within the US.
Postage for orders from Mexico or Canada
is $9. Only checks and money orders are
accepted on domestic orders.
Contents of the 40th NFFS Symposium
[[email protected]]
Free Flight Duration Louis Joyner
Also included in this column:
• Free Flight Forum Report 2007
• Micro E Timer
NFFS Free Flight Hall of Fame inductee George Batiuk Jr. has
been active in the US Junior program and directed the 2001
World Championships.
NFFS Hall of Fame inductee Gil Morris has designed Power models for more than 60
years. The 2007 Sympo describes other honorees and Models of the Year.
08sig5.QXD 6/22/07 9:21 AM Page 130
“The 50 Gram Open Rubber Model
(What Will They Look Like?)” by Peter
King uses computer simulations to
determine what model configuration offers
maximum performance. He looks at a range
of wing areas from 230 square inches up to
400 square inches. Airframe weights range
from 70 grams for the smallest to 112 grams
for the largest.
Peter also included what he calls the
Super 50-gram F1B: a modern composite
F1B with auto surfaces, delayed propeller
release, and variable-pitch propeller, but
loaded up with 50 grams of rubber instead
of the 30 grams used for the F1B event.
After crunching the numbers, Super 50-
gram F1B was the clear winner!
In “BMFA Rubber Models with a 50
Gram Rubber Allowance,” Phil Ball offers
his design suggestions for the class based on
his considerable experience with the Open
Rubber event. An interesting aspect of the
50-gram model is the much shorter motor
base: 25 inches down from 44 inches in the
Open version. This should help longitudinal
stability.
No matter what the rules are, selecting
the best rubber motors is vital. Mike
Woodhouse details his method in “Practical
Rubber Testing.”
It basically involves pulling the motor to
a predetermined load, measuring the
stretched length, and then measuring the
load at 10-inch intervals as it is eased off.
Data for each motor is entered into a
spreadsheet, which is used to rank the
motors for trimming, contest rounds, or
flyoff use.
Stuart Darmon explores the available
options for the Towline flier in “Combined
Glider—A Truly Inclusive Class?” In
addition to several model suggestions, he
offers a simple mechanism to decrease
stabilizer incidence during tow, thereby
increasing line tension and towing in calm
conditions.
The device consists of a hinged fitting at
the rear of the fuselage. In its forward
position it effectively shims up the stabilizer
TE a few degrees during tow. As the towFor more information contact the NFFS
publications coordinator, Bob Stalick, at
Box 1775, Albany OR 97321; via E-mail at
[email protected]; or visit the NFFS Web
site at http://freeflight.org. When you place
your order, be sure to print your name and
address clearly. Bob is still holding two
Sympo orders from last year that were
returned as undeliverable. Contact him if
you think they could be yours.
Free Flight Forum Report 2007: Extensive
rules changes for FF in the UK are a major
focus of this year’s Forum Report. The new
rules have, in essence, created new classes
of models with various handicaps to allow
classes to compete equitably in combined
contests.
The Open Rubber class (similar to our
Mulvihill event) has a maximum rubber
weight of 50 grams and is now called
BMFA (British Model Flying Association)
Rubber. Vintage Rubber (similar to our Old-
Timer Rubber event) is allowed as much as
100 grams of rubber. Classic Rubber (pre-
1960 designs) can use a maximum of 75
grams of rubber.
That allows a smaller contest to have a
combined Rubber event that includes BMFA
Rubber, Classic Rubber, Vintage Rubber,
and F1B (current FAI rules with 30 grams of
rubber). The hope is that the performance of
the various classes will be close enough that
everyone can be competitive. (The
alternative, as often happens in Britain and
in the US, is that small contests often have
too many events with only a few people
flying in each.)
Similar rules changes in Towline Glider
allow straight-tow, nonbunt models to use 75
meters of line, while circle tow and/or bunt
models use the standard 50-meter towline.
Under the new BMFA Power rules, buntequipped
models are allowed a five-second
engine run, nonbunt models with movable
surfaces such as variable incidence tailplane
(VIT) or auto rudder (A/R) are allotted a
seven-second run, and locked-up models get
10 seconds.
The paper “Rule Changes for UK Free
Flight for 2007” from the BMFA Free Flight
Technical Committee and presented by Chris
Strachan and Mike Woodhouse details the
rules changes and the rationale behind them.
ring comes off the model’s hook, a heavy
monofilament pin attached to the towline
releases a mousetrap lever, which releases a
line back to the fitting at the rear of the
model. It swings back, and the stabilizer’s
TE comes down to the glide setting.
In “Gurney Flaps on Free Flight
Models” George Seyfang explores the
history, variations, and advantages of the
simple devices mounted on the underside of
a wing at the TE. The flap’s height is
typically 0.5-2.0% of the chord width (i.e.,
1/32-1/8 inch for a 6-inch chord). The Gurney
flap can improve performance from 4.0% to
as much as 20.0%, depending on model
type.
Other papers include “An Indoor
Initiation by F1D” by Mark Benns and Nick
Aikman, “Taking the Tension out of
Winding—Or Does It?” (a half-tube
winding technique for F1B) by Mike Evatt,
“Oven Baked Propeller Construction” by
Dave Greaves, and “Rubber Motor Testing
for Indoor Duration Models” by Clive King.
Also “Outboard Horizontal Stabilizer
Configuration for Model Aircraft” by
George Seyfang, “Variable Pitch Propellers
for Indoor Models” by Bob Bailey, and
“The Effect of Stabilizer Sections on Tow-
Line Glider Handling” by Martin Gregorie.
The 2007 Forum Report is available
from Martin Dilly, 20, Links Rd., West
Wickham, Kent BR4 OQW, UK. The price,
including airmail postage to the US, is 14
pounds sterling (which is approximately
$30 in the US, but the exchange rate
fluctuates daily).
Checks should be made out to “BMFA
F/F Team Support Fund.” Since checks
must be in pounds sterling only and drawn
on a bank with a branch in the UK, it’s
much easier to pay by credit card. Contact
Martin by fax at (44)+(0)20-8777-5533 or
by E-mail at [email protected].
Back issues of Forums are also available.
The 2007 Forum is also available from
NFFS Publications (Bob Stalick) at the
address I gave previously. The price is $25
plus $5 postage. Only checks or money
orders are accepted on US orders;
international orders can be paid for by credit
card, but a service fee is charged.
Micro E Timer: The May Duration
column, which included information about
timers for small electric-powered models,
showed an early prototype of the Texas
Timers mechanical timer. The production
version of the Micro E is now available.
Based on the popular Micro I pinch-off
timer for Gas models, the Micro E is
adjustable for motor runs of up to 30
seconds. The micro switch, snubber
capacitor, and wiring are behind the
faceplate for a clean, uncluttered
installation. The micro switch is rated for 10
amps maximum.
The faceplate measures 2.16 x 0.89
inches, and the weight is 7.2 grams. The
Micro E is $45 plus shipping and handling.
Also available is a laser-cut 1/32 plywood
mount, which is available with a single- or
double-pole slide switch.
The Texas Timers Web site—www.texas
timers.com—includes additional
information about the Micro E and a typical
wiring diagram for small electric models. If
your soldering skills are a bit rusty, be sure
to look at the soldering-techniques tutorial
owner Hank Nystrom put together.
The mailing address is Texas Timers,
3317 Pine Timbers Dr., Johnson City TN
37604. The E-mail address is sales@texas
timers.com. MA