Hi. I'm a high school Physics teacher (11th & 12th graders) and have given my classes a year-long aircraft building project: design, build and fly an aircraft. My plan is to teach my students physics theory and principles as they design and build this aircraft from scratch, no kit.

I understand how and why planes fly (I was a rocket scientist in my former professional life). I'm new to RC aircraft and need some (ok _lots_) help getting started. The info I've found says (basically) 'pick an engine/prop and design the plane around them'. Because I want to teach the _design process_ as well as the physics of it all, I'd like to start with an airfoil and go from there.

Before I continuing, is this a path I should be taking? If not, I'll start over but where?

If so:

My Starting Point:
airfoil (NACA 2415) with chord = 0.2 m and span = 1.2 m
AOA = 6 degrees at Re=3 x10^6
Cl = 0.8
Cd = 0.008
(from airfoil data tables from one of my undergraduate textbooks)
[total flight-ready mass depends on a lot of things that are TBD, see below]

I can calculate theoretical lift (with the help of a friend who is currently a practicing rocket scientist, using integrals and other stuff I barely remember). I'll put in a safety factor of 20%. So I "have" L, but that depends on thrust so ultimately, success depends on the engine/propeller combo. Weight depends on engine size, batteries, etc. ... A circular argument, but that's the beauty and challenge of iterative design!

FINALLY the questions:
where can I find the engine and prop data so I can have a starting point for the design iterations?
how do I select an electric engine and prop?

It's beginning to look like I'm in over my head, but that's never stopped me before.
Thank you for reading this through and thanks in advance for any and all assistance.

Most designers design a plane (6-view), design the construction of the plane and the fit a engine and prop to it! The engineering feat of turning that process around would take more the the average bears tallents, I sure it could be do, be fun saying I have engine X and prop Y that creat nNN# of thrust, build the largest plane it could support. I think you would keep hitting stumble point! My designs when I start are real guesstaments as to weight, I usually look at like models if there are any and get a good estimate of weight and engine needs! Not being into electric motors i could not begin to help you there, but I have seen it discussed on this site. Someone will most likely chime in on that subject!

Look at models online and determine what motor and battery are being used for airplanes the size you are talking about.
Tower Hobbies is a good place to start.
http://towerhobbies.com/
The model research will give you a good idea of motor, battery and electronics weights as well as overall aircraft weight based on building material.
Research wing loading and try to design the plane at 20 oz./sq.ft. or less.
By already determining the appropriate motor and battery you can then set a size limit and weight for the airplane so the student can concentrate solely on airframe design.

I should also add, unless you have a student that is an accomplished RC pilot you should contact local clubs to have an experienced pilot look each model over before flight for safety and have him actually fly the plane.
Also, not mentioned, Center of gravity is very important on a model. if it is too far off it will be difficult to impossible to fly.
PS: let us know how it goes, post a picture every now and then. I would be very interested to see this develop. and feel free to come back and ask questions as they come up.

I assume you want something a beginner could fly when you are done??? First thing I would look at is a flat bottom airfoil. For the rest of us that use standard measurement you indicated a wing with a 47.25 inch span and a 7.9 inch chord. Do you intend to incorporate dihedral in this wing? It would be more stable for a beginner if you did and it will be required if you do not install ailerons. I have a habit of using the TLAR (That Looks About Right) meathod and coming up with planes that fly. Assuming you base your design off of traditional high wing trainer type aircraft proportional to this wing and use light weight building materials such as balsa and/or foam, a [link=http://www.horizonhobby.com/Products/Default.aspx?ProdID=EFLM4010A]Efligt power 10[/link] brushless electric motor will fly it. Keep the [link=http://www.horizonhobby.com/Products/Default.aspx?ProdID=EFLB18003S]battery[/link] weight low and aim for 16oz/sqft of wing area or less. Your wing area is about 2.5 sqft so this gives you about 40 oz to build your plane with or 2.5 lbs(lighter would be better).

Remember that physics only explains why it flys and engineering is what makes it fly Take a traditional paper airplane and then make a copy of it with only one ply of paper (no folding over edges) and give em both a toss...

The point of that is to say take a look at some proven structural designs to ensure your students efforts don't fold up under the stresses of flight.

I just have to do this.

My math is called ARF.
He is so far over my head, I'm getting a migraine. Dennis

Welcome to the forum, Alvinlim!

Two great books for your students and you:

“Basics of R/C Model Aircraft Design� Andy Lennon
http://www.amazon.com/Basics-Model-A.../dp/0911295402

“Model Aircraft Aerodynamics� Martin Simons
http://www.amazon.com/Model-Aircraft...4966903&sr=1-1

Also:

http://www.lerc.nasa.gov/WWW/K-12/index.html

http://members.aol.com/KMyersEFO/

Regards!

Sounds like your class is going to be WAY more fun than my High School physics class. We did the mousetrap car competition. The aerodynamics forum will probably be the place to spend some time. Also, I'm sure the guys in the electrics forums will be able to help when it comes to the powerplant.
Good luck and keep us posted as you progress.[8D]

Generally speaking, the starting point for designing an airplane is deciding its purpose . Do you want it to go fast ? Go slow ? Glide ? Carry cargo ? STOL ? Be maneuverable ? Be stable ? Carve ? Skid ?

Once you know what you want your airplane to do, then you can sellect an airfoil. And once you know the function of the airplane and the size and weight of the airplane, then you can sellect your power plant.

So your first question is: what do you want the airplane to do ?

Welcome, that sounds like a great class project. Its not all about theory and classroom instruction. get yourself and the class to a local club field and learn there. become a pilot and learn to fly a r/c plane. you will learn more on common sence and other design issues. then bring it all back to the class room and put it together but keep going to the club to learn and try your designs. I wish I had been in your class back in school. good luck

Wow,

All that jargon reminds me of my college fluid dynamics class! That was not fun at all!


This may be too "low tech" for your purposes, lol, but I have written a [link=http://www.hooked-on-rc-airplanes.com/model-airplane-propellers.html]page to help explain prop selections[/link].




Hope that helps.

WOW is right!

Quite a tall bill to fill and then expect your students to learn to fly R/C as well.

IMO the physics of flight could be taught from a proven kit or plans build. The model could also be a rubber powered airplane or even a free flight glider vs. a R/C setup. There are folks who still build and fly rubber band powered airplanes you can find information through the AMA.

Best of luck with your challenge!

Hi,

It seems that you want to MOTIVATE your student to think and USE physics, not just solve textbook problems.

#1 What is your budget?
#2 Are land vehicles an option?

You have several viable options:

#1 build one gws slow stick as a class and have groups of students design modifications for the airplane
#2 get a $30 air hogs havoc heli and have your students measure lift, speed, runtime, design modifications and test them

You could save yourself a lot of trouble and assign your class a land based vehicle design project.

Purchase two 4-channel radios and a bunch of used servos off of ebay. Have your students design circuits and build rc robots/vehicles that will shoot each other with electric airsoft guns. Have your students take a trip to the local printer/scanner recycling center. There they can find belts and gears for your projects as well as motors and belts from cd rom drives. They can also learn about how electronics are recycled. Better yet, assign your students a project: design and make SOMETHING from using as much parts from old printers, scanners, stereos, etc.

The cost to each student would be as low as $50 if it is well planned and further reduced if the kids work in groups.

Design, no problem

Build, good project

Learn yo fly? Now you're asking a bit much.

Unless you design and build something along the lines of a 2-meter, polyhedral, powered glider you may find the "Flying" part difficult. It takes most people several months to learn how to fly - and that's one-on-one with their instructor, not a class of students with one instructor.

And what happens if ONE of the students crashes the plane beyond repair?

I think it might be a much better idea to contact your local club (Just ask, we can help you find it) and have one of the seasoned fliers do the "Test Flight".

Thanks everyone for the warm welcome and words of advice and encouragement. The 'fly' part of this project was meant for an experienced pilot to be in control. At first, I thought I would fly them all, but that would be about as bad as letting students pilot the craft.

There's an rc park a couple miles from my place, so I'll be there picking your brains and hopefully not become too big of a pest. Maybe I might be able to talk one or two of you into being the project's (volunteer) 'Chuck Yeager'. Sorry, my budget is not big enough for paid test pilots.

I'll be working on a 'proof of concept' model, so I'll be back with more questions.

That's exactly why I put out this challenge early. I had planned to do the project myself to see if it's even possible and do it next school year. These kids seem capable, but many seem to be lacking interest/motivation to be in school. I thought this project would spark some interest.

Great ideas, I may do that next year. I don't want to change things up on them yet again. I'm also doing it to keep me motivated and my "engineering muscles" a workout.

Yeah, fluid mechanics was the bane of my existence and was the only class I ever failed (I got an A the next time).
Thank you for the reference, (not low tech at all) it will come in handy in a few weeks(?) when we start building.

I've set up the project like the X-Prize, but with different categories.

1) move 10kg cargo a distance of 10m as quickly as possible (probably need to lower the mass)
2) race to 100m (almost) straight up (fastest time wins, not head-to-head) (probably need to lower it to 25 or 50m)
3) obstacle course IF we can figure out control issues
4) fastest combined time wins the 'all-around' competition.

Is this asking too much for one craft to do? too much to ask high school kids to do?
Some of these kids have never been challenged and held accountable for anything. I'm hoping that challenging them with something that appears impossible in their eyes and dragging them (if need be) through the process to show them they can do it. By putting them in teams where other people are helping with the work and are depending on them will help steer at least one student away from the Dark Side.

Sorry, this isn't the place for that kind of stuff, but it feels better having put it out there.

With all appreciation for what you're trying to do for these kids, I gotta say I think you're setting them up for failure.

With inexperienced designers building from scratch, the likelihood of every plane crashing on takeoff or shortly therafter is high. Give them a project that they can fail at a few times without destroying their work, so that their chances of success is high if they do the work. I'd go with rubber band free flight planes. You can do competition in landing accuracy, duration, and altitude. And they can get the setup right on them with partial motors without much chance of damage. The cost will be cheaper, and you can teach most of the same engineering principles.

Hi,
I happen to agree with Jester on this one. This reminds me of a high school experience:

Grayle (fellow RCU poster) and I went to high school together in the area and took a class called aviation/aerospace. This was about 14 years ago, we both chose to build and fly a glider, we chose the Gentle Lady. Neither of us had flown before, but we were interested in it, so why not. We spent most of the school year building it at his house and near the end of school we decied to fly it in the football field, using a surgical rubber upstart. we pulled it back a fair distance and let it go, it promptly went skyward, then back to the ground in about 6 seconds. Terribly embarrasing.

Well, I guess the good thing is that we never gave up, he is a successful machinist and I am a Mechanical Engineer. BTW, please tell me you aren't teaching them about the Reynolds number, ugh!

These students are lucky to have a teacher that wants to challenge them like you want to, but I would pick something easier, or maybe something with more iterations where they can refine their designs. Maybe the small balsa planes would be a good start. I used to build the Guillows brand planes out of balsa, and covered them with tissue and shrunk it with water mist. The kits are very inexpensive and they are die cut. These can be modified and they have a great cheap starting point, and are driven by rubber bands. Maybe your payload on these planes could be stacks of coins. Using a standard regulation rubber band and you can control the environment by flying them in your gymnasium.

Have fun,
Curtis

alvinlim34, where are you at in California?

Lake Balboa, CA
(west Van Nuys)

My highschool senior physics project/contest was to see who could design a box that would protect an egg when the box is dropped. The goal was to see who's box could drop the farthest without breaking the egg.


Something along those lines would probably be more feasible, unless you have a class room full of future astronauts. Then your project my work!

Just my opinion.

Here is how I have seen this type of project done successfully:

Spilt the class into teams of two. Have each team purchase an inexpensive kit - you can get group discounts if you contact a company like Tower Hobbies http://www.towerhobbies.com/

Here are a few good choices:

http://www3.towerhobbies.com/cgi-bin...?&I=LXDJC3&P=0

http://www3.towerhobbies.com/cgi-bin...?&I=LXJ596&P=0

http://www3.towerhobbies.com/cgi-bin...?&I=LXM399&P=0

http://www3.towerhobbies.com/cgi-bin...?&I=LXFG09&P=0

Once they are built, arrange a day with your local club when you can take them there and have the club members test them.

BTW, most clubs will be very willing to come to the classroom to help out any way they can. As you can see from this thread, we are more than anxious to share our hobby!

Wow wish I had a high school class like this! I have a Pilatus Porter airplane with the following wing dimensions Span 52.5 inches and a chord of 7 inches. Your wing size should be fine. I'd tend to think as stated earlier, a flat bottom airfoil would be a better choice. Keeping the all up weight under 3lbs would be crucial. A 10kg load is out of the question. I think a 10 once load would be a bit much in a plane of this size. An electric motor comparable to a .25 size glow motor with lipo batteries would give plenty of power and help keep the weight down. Sticking with a brushed motor and speed controller would help keep costs down.