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squishy
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squishy:
If you reread the first thread and watch the video, I am trying to try to duplicate with my F-22 foamy model the same movements of the F-22. Look above your reply and I outline what is needed to be done as stated in "problem". Now, can it be done?, that is the fun of it.


That's what I though and it's why I asked...



As Rod has stated above and it's important for all RC pilots and modelers to remember, these are not full size aircraft, you cannot duplicate the physics of a full sized aircraft, you can only duplicate it or model it but it's literally impossible to micro manage forces on surfaces like this to replicate the exact same behavior of a full size aircraft.

Lets just brain storm for a moment and leave out the math. Image two F22's sitting on the runway, both ready to take off. For this example, we don't even need to talk about control surfaces or their behavior at any point, we won't even reach that part and I can example. Both apply power and start rolling down the runway gathering speed.

F22 - 60,000lb's average working weight, 23,000 to 35,000lb's of thrust, wing area 840 ft² (78.04 m²).
F22v2 - A tiny foam model weighing how much? how much thrust? wing area? exact matching airfoil?

If your brain can visualize and "feel" the forces of each during take off, it's easy to see why things don't scale well. For one thing the full size F22 is going to accelerate that 60,000lb aircraft pretty dang fast, it's going to hit the air with a comparatively giant wing and lots of wing area (they are great for shade at the airshows), when it pulls up it's using all surfaces, controlled by a computer. With that weight, speed and force, just imagine what the pressure and forces are like on those surfaces. Like a gun it launches down the runway to get that weight up to around 300 mph (500kmh) in a very short time, it takes off like a dragster and then fights to grab the air with every piece of computing power it has to remain stable and efficient. Can it take off and do most of this without slats, flaps or a computer? Most likely yes it can, but it would be much much more inefficient and would use up precious gas which equals range, which equals tactical advantage in war. Your purpose is very very different than the full size, you wish to visually duplicate or even duplicate the physics of that extreme dynamic heavy and powerful act.

Stop here and realize that you will never match the phycis or model it to behave the same way. But you may be able to visually duplicate it, just as rc airplane designers slightly alter every scale design so they actually fly, you can also "fudge" and "cheat" in order to visually model what you see in that video. Lots of people practice scale take offs with scale model airplanes. But it's all in the pilot, not the airplane.

Now, do the same exorcize we did above with a small model. Put it in the same position, run it through your head, what happens? Now your weight is what? less than a 1lb, thrust and acceleration drop to almost nothing compared to the full sized, the forces on the control surfaces are so miniscule they are almost irrelevant, with a tiny bit of speed the model takes off in less than 8 feet. The forces are simply not there, they do not exist in the same realm of the full size aircraft. In fact there so many factors to cause this it would be impossible to list them all here, but I do find the Reynolds numbers being mentioned a lot when talking about this subject. Studying the scaling of basic airfoils will give you the background to understand what is needed to scale aerodynamic forces. The lift produced by a 6" long airfoil is not directly proportional to the lift produced by a 6' version of the same airfoil, even if they're flying at the same speed. Keep that in mind.

So in conclusion, you will never duplicate the act of a F22 taking, not unless you had a real F22. BUT, you can replicate it visually or model the act by using almost 99% trickery and pilot skill. If you approach it this way you will be successful, I fear you are going about it the wrong way around. I hope this helps...
"Education is not about filling buckets; it is lighting fires." W.B. Yeats

http://www.youtube.com/user/squishy654
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squishy
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Interesting 3 Flights!!! (36 degrees and 5-10mph wind)
Bad News-set nose gear 0 degrees,3 and 5 degrees up and tried takeoffs(no slats). Tried even aft CG and plane comes off and flips backward at high speeds. Need to install lengthen nose gear.

Good News!!!!!!--- Elevator deflection(up) overcomes leading edge slat driving the nose of the plane down. After three flights, established control of throttle-slats so I now am able to throw ,fly and land plane leaving the slat mode on at all times. High alpha's are steeper then my reg F-22 before it wing rocks and it lands like my STOL transport, steep and slow. Actually Luke Warm statement above "is right up the alley". Rudder is essential to keep this beast in line. I hope someone else will try this setup.

Getting a new battery today so you can see it perform.


I like it, trial and error is the way to go, you are in unknown territory and you gotta find out this stuff for us..
"Education is not about filling buckets; it is lighting fires." W.B. Yeats

http://www.youtube.com/user/squishy654
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rodrigo
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Rodrigo:
Understand you are playing around with VTOL. Can't wait to hear how you are approaching the problems. Very shortly, I will present my second attempt to try to get it to work.

Is really simple... Just Google vought XC-142.. the grand father of the Osprey but lot more simple (tricopter )...is VTOL and cargo. who needs more!!! I think it will work with just one gyro , 2 will be perfect but prices of the multiwii controller are cheaper than the other options and makes the way lot more easier...
Sadly actually I'm really busy with my own house plans... No time to cut a new plane (be200 suspended too)... Just sketches

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, what is your main interest...

Have fun with this little planes... Actually my only plane is the bronco (v2)with flaperon, dropping parachutes capability, fixed landing gear with steereable nose wheel and lot of power to some aerobatics ... I love this plane because is fast, maneuverable and predictable... About my airfield is a farm with a dirt road not really easy thanks to the wind direction (60% of good landing ratio)...I love take off and land, successful wheels installed on my F15, C119, F111 and bronco



Enviado desde mi GT-I9100 usando Tapatalk 2
good luck!

tx Futaba 9CAP & 8U
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whatmovesyou
Yes, looked at it. Question is, how do you handle whole elevator changing tilt, rear motor/prop as well as keeping wings horizontal and then making the transition. What happens if one motor goes dead or looses power?
I like to design and fly unique planes.
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rodrigo
Just the first idea...tilt angle coupled to elevator (same angle) and rear motor will start when the main wing start to move, this motor needs to be controlled by pitch axis of the multiwii and elevator stick.
What happens in motor fail?... Just crash and mourn the loss...

Enviado desde mi GT-I9100 usando Tapatalk 2
good luck!

tx Futaba 9CAP & 8U
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whatmovesyou
This video demos how the throttle movements change the deflection of the slot. If you punch the throttle real quickly, very little movement occurs and you can get out of trouble. By flipping a switch, it shuts off the slot. Graphing mixes are real helpful.
I like to design and fly unique planes.
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gm3
very cool, that might work.
aaaaaannnnnd there's the tree
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