HELP ME.....!!

I'am currently in my final year of Uni and for my final year project i have decided to base it on the BMFA heavy lift challenge or (SAE Aero Design US version)

The aircraft constraints are:

o Only fixed wing designs are allowed.

o Maximum wing span limit of 3 meters.

o Rotary lifting surfaces are not allowed.

o Gross platform must NOT exceed 900 square inches.

o No part of the aircraft maybe jettisoned.

o No gyroscopic assistance is allowed.

o Power plant used must be an Irvine Q40 glow
engine .40 (6.55cc). No internal or external
modifications are allowed.

o Fuel used must be 5% Nitro methane and 20% Castor
oil.

o A propeller spinner or rounded safety nut must be
used. Multiple props, prop shrouds, fans or reverse
pitch pusher propellers are allowed.

o Metal props and variable pitch props are not allowed.

o Fuel tank must be accessible to determine content
during inspection.

o The aircraft must take off within 61 meters and land
within 122 meters.

o No computerized transmitters are allowed.

o A cargo bay must be included in the aircraft, the bay
must be fully enclosed in flight and accessible on the
ground.

o The internal dimensions of the cargo box must not be
less than 118mm x 93mm x 245mm.

o The cargo box cannot be an integral part of the
aircrafts structure.

o Aircraft must perform a 360-degree turn in flight.

Any information regarding wing design, airfoils, extra lifting devices, configurations of aircraft, materials anything will help.........!!!!

For starters, figure the planform area:
Wing, fuselage and horizontal.
Design the smallest fuselage in width with about a 1 chord nose moment.
A skinny tail boom.
Tail area need be no more than 15% of the wing area.
So of the 900 sq.in. allowed, subtract the fuselage area.. That's 115% of your flying surface.
Compute the horizontal area.
The remainder is your wing area.
Divide that by 3 meters, that's your average chord.
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The cargo box should straddle the c.g., which will be about 30%. So 1/2 the box length positiions the c.g.
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Arrange the root chord to give an adequate opening to the cargo area... usually under the wing.
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This is where a straight trailing edge and swept back leading edge helps. Moves the m.a.c. back, which permits a larger opening for cargo access.
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Selig 1223 airfoil.
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Flying stabilizer.
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NO CF landing gear struts! They WILL snap!
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Ailerons that go UP only.
Couple the rudder to the ailerons.
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Tricycle landing gear.

I use skateboard wheels. Ball bearings make for a frictionless ground run.
(Use NEW wheels for the competition.)
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Stuff I fingered out after watching the 2000 SAE competition here in Palmdale..
http://www.angelfire.com/indie/aerostuff/sae2000n10.htm
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It is the MOST FUN an airplane nut can have, this SAE/BMFA competition (and the AIAA sparky equivalent)!

Uhmmmmmm, Tall Paul has good stuff.......... but..........

SHOULDN'T YOU BE DOING YOUR OWN HOMEWORK ???

I agree with Paul about the fun thing. When I was attending college at Purdue U. in '65 it seemed that any hint of having fun with senior projects that involved airplanes in the aero engineering course was frowned on or something. We built a lot of them in our dorm room but none for credit, actually the time spent on them seemed to take away from the study time. Of course single channel and finally reeds were not all that reliable either. It was a fun time otherwise but I wouldn't care to go back and relive those days.

Tall Paul ive undertaken some research on the Selig 1223 airfoil and found unless the trailing edge can be produced accuratety (No CNC) as it is so thin the airfoil becomes less affective also try to inclued flaps would be difficult....Could you suggest any others.......???

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The plane size is essentially a SIG Seniorita.
A flapped Clark-Y would work at the Reynolds numbers involved.*
"..less effective.." than what?
For chords less than 12 inches practically all the fancy trailing edge shapes will do equally poorly.
Flaps on a 1223 are mind boggling anyway! It's already blessed with a significant flap with that trailing edge. Deflecting it more? Adds drag more than lift.
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There's an equivalent Eppler.. 423 which works OK. I've built both types. Without CNC or CF or anything like that.
And a Wortmann 65-xxx? is popular.
If you can find the coordinates for the Ryerson 45-A.. it's probably the best. A very thick 1223 look alike, but flies WELL!
The basic problem is accelerating the mass to takeoff speed in 200 feet. For this to occur best, the drag of the airframe should be minimized. The airplane attitude at liftoff speed should be designed into the configuration.. enough incidence, thrust line, fuselage "sit".. all congealed to the least drag situation at liftoff.
It should fly off the ground with maybe a bit of elevator for the last little bit of alpha. Too much it stalls. Too little, it just runs on..
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A GOOD (properly broken in) motor with the correct prop will get the plane up.
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Then the plane has to make those dual 180's.. The first one gets the tip stallers.. the second gets the pilots that pull too hard to keep the nose up in the turn.
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In the competition, surviving is paramount. Those with lots of r/c experience do well. Planes are flyable, and easily maintained. And it has paid off to select a good weight goal, not an extreme one.. getting the predicted value up and down counts more than anything else.
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Simple with few moving parts; all easily accessible for maintainence; WELL FLOWN.. that's what describe a winner.
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*When drawing up the plane for the 2003 SAE competition... only limit this year is wing span, I placed a Kadet Senior rib outline over the same sized 1223.. the upper curve is very similar quite far back, and the lower curve until the Selig begins bending is the same!
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**
And it is YOUR project..

Everything said above is great. My team took third place last year in the SAE west competition. Here are a couple of things I learned.

1. Build a prototype as soon as possible no matter how ugly or unflyable it turns out to be.

You will learn many things. We built 2 prototypes before the competition and each one was an improvement. We were lifting 22 pounds months before the competition and were able to make many improvements. This was key to our success. The majority of the groups that showed up with a non-tested plane did not do well.

2. Keep it very simple.

I noticed that none of the complicated aircraft did well. They take more time to build and are harder to get flying. I don't think a plane with slats or flaps placed in the top 5. Our design was very simple.

3. Consider the take-off run.

A lot of groups forgot that you had to takeoff in 200 feet. Rolling resistance was the major problem. I was amazed what I saw for landing gear. We used spun aluminum wheels with ball bearings. O-rings lined the aluminum wheel and were wired to the wheel. Now imagine trying to stop that same plane on the runway. It was a challenge.

4. Build strong and keep the weight to a minimum.

If we had built our plane 1 pound lighter we would have taken first place. Composites and light plywood work well. I've seen people use aluminum, which I think would add more weight than strength with this size plane. Look at different radio components. We cut off a half pound using non-standard components.

5. We used aluminum landing gear.

We severely bent it a couple of times on landing. Our gear never broke. We were able to bend it back. Some of the planes with composistes landing gear were disqualified because it broke on landing. It also absorbs energy on those less than perfect landings.

6. Oversize the vertical stab area.

We designed our plane using an average of area ratios. Our plane turned out with sever yaw stability problems. It was hard to fly, but flyable. You can oversize it with a minimum weight penalty, yet it will add much needed stability.

7. Get a good, very experienced pilot to fly it.

When fully loaded these planes are hard to fly. It was the most difficult to fly airplane I had ever piloted, especially when fully loaded.

8. Design to reduce tip stalls.

The majority of the planes crashed due to a tip stall. That is how our first prototype crashed. On our final design we incorporated a couple degrees of washout. We tested the plane almost fully loaded and it would not tip stall. Stability in the air is very important.

9. Do a good job on the documentation.

A good part of the score comes from the report. Without a good report you have no chance. Research all design desisions so that the questions can be answered in the oral report session.

10. Run static tests with the motor and various prop configurations.

Props are usually a heavily guarded secret. I can't help you here because I'm going to assist future teams. We have our secret prop that worked very well. We were accused of cheating due to the way our plane accelerated.

Hope this helps.

Thanks peeps for all your useful comment...........

I was fooling around with the Selig 1223 in XFOIL using a 20 degree flap hinged at x/c = 0.8. Results: DRAG. Max Cl was 2.278 at 11.5 AoA with Cd = 0.06889. A normal Selig 1223: Cl = 2.209 at 12.5 AoA with Cd = 0.03887. If you use the Selig, be sure to use aileron differential.

Hey AQ, what team did you fly with? I probably saw you guys there, I was with UC Davis. We were the guys with the flood lights set up outside our rooms.

I was on the Ute Lifters. We had that ugly red plane with the 10 foot wingspan that never made a good landing, which was my fault.

I remember seeing the floodlights.

This year there was not enough interest in the project. I've talked to some of the Juniors and it looks like they will compete next year. I had so much fun I decided to help. I am considering doing the project for my masters degree. Can you believe that we can play with model planes and get college credit?

Here is a picture I found. I'm on the far left.

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The usual lift-off Cl at 200 feet is about 1.
There's insufficient power available to get much past that.
And I suggest 100% differential. NO down going aileron at ALL!
Just to be safe.
It can be done mechanically, since computer radios are ruled out.