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Joshua and Hope Finn, J&H Aerospace Georgia TSA State Leadership
Conference 2020
March 12-14, 2020, Athens, GA
Introduction Importance of Aviation Competition
Event Format
Construction Advice
Successful Preparation
Flight Trimming
Online Resources
Local Resources and Competitions
Kits and Tools
Importance of Aviation Competition – Why Do We Care? Indoor free flight started by Alphonse
Penaud in 1870
Inspired Wright Brothers
Chosen hobby of Burt Rutan, Jimmy Stewart, Neil Armstrong, etc Many, if not most big names in aeronautical technology
flew free flight!
Wright Stuff/TSA was starting point for Doug Schaeffer (CERN), Brett Sanborn (Sandia), and Evan Guyett (Scaled Composites)
Parts of an indoor plane
Event Format – Middle School Bring 1 prebuild glider, documentation
with drawings and flight logs Toolbox with building tools and
templates Launch from hand held catapult
supplied at the event (can be approximated in practice with a yarstick and handle
Typically competitive airplanes are about 4g Refer to event build rules for restrictions
on dimensions of prebuilt planes
No trimming flights allowed for prebuild planes
No markings allowed on wood blanks for semifinal round
Event Format – Middle School Preliminary round, all 3 flights
count, no drops
Top 20 entries proceed to semifinal round
Build plane on site, trim, and fly
Documentation will also be checked; don’t skimp on it!
Event Format – Middle School
Event Format – High School Two airplanes, rubber band powered Launched from the ground 7g minimum weight,
~17 in. wing span, no max length (don’t go under 1.2x wingspan in if you want a reliable airplane)
Balsa fuselages, sometimes with carbon reinforcing and kevlar bracing
Balsa stick flying surfaces with curved ribs and plastic covering
Build or buy propellers
Event Format – High School
Aerodynamics – Glider Airfoils Stanfoil is
dominant for outdoor and high ceiling flying; modify with undercamber for Cat III sites
Aerodynamics - Glider Airfoils Stanfoil variants are very friendly to planing before
sanding; with a 2/3 -1/3 Sweepette style wing, you get airfoil taper as a byproduct!
Aerodynamics - Glider Airfoils Yahinskiy airfoil has become dominant for low ceilings
(extreme turbulation properties
Construction Advice Buy a kit, or two, and learn their secrets before trying
to design your own airplane – it’s harder than you could ever imagine to design a flyable airplane, let alone a competitive one
Take your time building – keep airplanes straight and light
Don’t overuse glue; make sure the entire glue joint is bonded, but no excess
Don’t use spray CA accelerator—it softens many materials and damages planes
Construction Advice Sand carefully with fine grit sandpaper; fancy airfoils
seldom help
Good balsa selection on motorsticks and wings is usually superior to carbon reinforcing on poor balsa
Poorly built airplanes trimmed well always beat beautiful airplanes trimmed poorly
Choose wisely between build time and flying time
Construction Advice – Balsa! All balsa is not created equal. It can be cut at least 3
different ways, and it ranges from 2.8 lb/ft3 to over 25 lb/ft3; we want wood in the 3.5-7 lb range for wings and tails
C grain wood is critical for tail surfaces on light gliders
Successful Preparation STORE PLANES IN A
SUITABLE BOX! Never, ever store tools
with the airplanes!
Show up with twice as many planes as you plan on using; make trim flights and select the best ones A good selection of propellers is important
NEVER fly an unproven airplane in competition
A finicky airplane, even if it puts in the best individual times, is seldom a winner
Successful Preparation – Middle School Be willing to break airplanes, and take the
time to fix them instead of starting from scratch!
Calm air is essential; get it any way you can!
Know the rules and demand that they be followed – event organizers even at nationals often get it terribly wrong Incorrect time limits
Unacceptable flying conditions
Incorrect measuring methods
Failure to record scores in timely manner
Successful Preparation – High School Fly early, fly often
If you aren’t breaking motors on 1 out of 3 flights, you aren’t winding hard enough
Practice flying under time limits
Record EVERYTHING Turns/Torque/Backoff/Turns remaining, Motor length
and thickness, number of winds on motor, climb height/endurance, total flight times, temperatures, air conditions, circle diameter, CG location, Incidence settings
Flight trimming – Middle School What do we want from our gliders?
Outdoor: right climb, right transition, left glide Alternative: left climb, left transition, left glide; somewhat risky
Nearly 0-0 incidence
Rigid airplanes, 55-60% CG
Flight trimming – Middle School
Middle School Flight trimming – CG vs Incidence Most beginners struggle to
understand whether to add nose weight or elevator trim
Watch long term behavior to see
A glider which fails to recover, ever, need s incidence A glider which simply glides too fast is
merely nose heavy
A glider which loops at high speed has too much incidence A glider which merely stalls repeatedly
in glide needs nose weight
Flight trimming – Middle School Indoor is much different! Indoor gliders are floppy!
3-4 degrees, incidence, 30-35% CG
Indoor, low ceiling: straight climb, right transition, right glide
Left wing washout, start at root
Wash out tips; DO NOT USE FOR ROLL TRIM! Right rudder
Slight washin, right stab tip
Flight Trimming – High School Planes twist significantly under the load of a fully
would motor
You need a steady, tight circle to get safe flights
Flight Trimming – High School Crooked airplanes often fly best; Newton’s Third Law
dictates many counterintuitive adjustments
Flight Trimming – High School From The Best of INAV at indoornewsandviews.com
Flight Trimming – High School No-Nonsense Trimming from Technical Library at
freeflight.org 1. Locate CG. 2. Balance model without prop and motor to locate CG. 3. Glide model. 4. Adjust stabilizer for a smooth glide 5. Check stability by launching into slight dive and climb. 6. Readjust CG for stability if necessary. 7. Mark location of the new CG (if changed in step 6). 8. Install prop/motor and rebalance to established CG. 9. Test fly under power. 10. Adjust flight pattern with thrust line.
Flight Trimming – High School Tail-Volume Coefficient for Free Flight Models from
Technical Library at freeflight.org
Flight Trimming – High School Wind off the plane using a winder and torque meter
You don’t have time to hand wind and your plane doesn’t have time for the repairs!
Online Resources indoornewsandviews.com
Sum total of all indoor free flight writings EVER Start with The Best of INAV
https://freeflight.org/library/technical-library/ jhaerospace.com/news-and-tips/ joshuawfinn channel on YouTube scioly.org/forums/ hippocketaeronatics.com
Community Resources and Competitions Contact us directly at
[email protected] Thermal Thumbers of Metro Atlanta –
thermalthumbers.com Cochran Community Center – available on weekdays West Baden Springs, IN
(March 28-29, 2020, rubber power only)
Kent, OH (April 25-26, 2020)
Eager, AZ (May 27- June 1 2020)
Kits and Tools Freedom Flight Models – freedomflightmodels.com Guru Engineering Tech – www.guruengineeringtech.com J&H Aerospace – jhaerospace.com Retro RC – retrorc.us.com Stevens AeroModel – stevensaero.com Indoor FF Supply – indoorffsupply.com Laser Cut Planes – lasercutplanes.com Volare Products – volareproducts.com Peck Polymers – peck-polymers.com Specialized Balsa – specializedbalsa.com
Tools/materials you need:
Tan Super Sport rubber Balsa stripper Catapult Single edge razor blades CA glue and accelerator Duco cement Modeling clay or plasticine Milligram scale Stopwatch
Joshua and Hope Finn 2020 GASO Summer Workshop, July 2019