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

joshuawfinn@gmail.com 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