Aerodynamics Discuss the physics of flight revolving around the aerodynamics and design of aircraft.

extra 260 maiden

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Old 05-20-2012, 05:02 PM
  #1
orthobird
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Default extra 260 maiden

I flew my 27% 260 extra today
and i wanted to slow plane down,
so i used receiver and plugged right wing aileron to "AIL" and the left wing was connected to Aux 2.
I was able to program FLAPERONS

and wow, did they work:


http://www.youtube.com/watch?v=uJ66FHxURFg


really helped to slow down plane for landing, it just floated in

the flaps i used were half only, and upon doing so, plane wanted to pitch up, so i had to manually give plane down elevator, to get plane to not flare up as much, once engine speed was decreased further, then it just touched down.

what i need to do next is program in some down elevator with the flaps, so it does not pitch up as much.

enjoy video, tell me what you think.
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Old 05-21-2012, 09:35 AM
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Default RE: extra 260 maiden

Watch out for any increase towards tip stalling with flaperons. Especially with such a strongly tapered wing and what appears to be constant width strip ailerons.

With strip ailerons the increase in the camber and locak angle of incidence caused by drooping the flaperons will result in a washed in wing at the tips compared to the root. Yes, you're getting more lift to work with but if you slow the model down to really use the extra lift you could easily find that the model is more prone to tip stalling.

As per usual with such things do all the practicing the classic 3.5 mistakes high to get a feel for it.

It was a great landing at the end but it's hard to say if it was faster than no flaperons or not without being there or seeing some no flap landings to compare.
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Old 05-21-2012, 09:38 AM
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Default RE: extra 260 maiden

thanks

you are right

i am certain i could lane plane without,

i will try next time to land without them.

also, i set the flaperons to be minimal, and there are two setting, 1/2 and full, and on this landing, they were on 1/2

i will reduce the movement further, but i will still try to land without them.

best regards,
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Old 05-21-2012, 04:21 PM
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Default RE: extra 260 maiden

Doesn't that plane have full span ailerons? If it does you are increasing the incidence of the entire wing and will not change the washout by adding flaperons. I do agree to practice with it at a safe altitude to get accustomed to any unforseen quirks that may arise. Unless your A/C is excessivly nose heavy, or has a high wing loading, that design can slow down well for landing without the use of flaps. They do tend to hold their energy well and you have to learn how to slow it down for landing and keep the descent shallow. Getting the idle low enough also makes a huge difference.
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Old 05-21-2012, 08:27 PM
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Default RE: extra 260 maiden

Mine lands like a trainer, predictable all the way down to a 3 pointer, but its likely 2-3 pounds lighter too.
Carefull with Flutter and rudder problems when running 50cc
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Old 05-22-2012, 03:07 AM
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Default RE: extra 260 maiden

been there already:

http://www.youtube.com/watch?v=8CqjQZ-alpQ


after servo was replaced with JR 8411, and other damage was repaired

here is next flight:

http://www.youtube.com/watch?v=uJ66FHxURFg
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Old 05-22-2012, 04:05 PM
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Default RE: extra 260 maiden

Ah, you found out why you need stiff ailerons, stiff hinges, stiff linkages, and counter balanced ailerons eh. If the previous statement were true a miniscule servo with no gear slop would be sufficient. Effectively by adding a larger servo, you are damping the system with its resistance due to its torque needed to move it off its assigned "spot".

To help eliminate flutter, do NOT place your servo linkage at the aerodynamic center of the aileron. If its a kit, most likely, they predetermined this for you already. Place it at a prime integer value of the AC. 1/3, 3/7, etc.

Enjoy your introduction into vibrations.

Cheers

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Old 05-22-2012, 05:15 PM
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Default RE: extra 260 maiden


Quote:
ORIGINAL: BFoote

Ah, you found out why you need stiff ailerons, stiff hinges, stiff linkages, and counter balanced ailerons eh. If the previous statement were true a miniscule servo with no gear slop would be sufficient. Effectively by adding a larger servo, you are damping the system with its resistance due to its torque needed to move it off its assigned "spot".

To help eliminate flutter, do NOT place your servo linkage at the aerodynamic center of the aileron. If its a kit, most likely, they predetermined this for you already. Place it at a prime integer value of the AC. 1/3, 3/7, etc.

Enjoy your introduction into vibrations.

Cheers


Can you give a more in depth explanation of this?

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Old 05-22-2012, 05:38 PM
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Default RE: extra 260 maiden

i second this motion
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Old 05-22-2012, 07:43 PM
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Default RE: extra 260 maiden

Yes , many will disagree, but this is no 50cc plane at all
Nitro OS 160. Moki 1.8, maybe 2.10, 4 stroke 1.40 - 2.20 or 30-35cc gasoline.

When going 50cc gas, things get a bit complex and tight and the added weight just makes it a fast sport model, that struggles with slower flight envelopes alot, including landing and other airframe issues.. sure it will rocket out of a hover and across the sky.

The limited 3D it was designed around, is lost with the added burden of bigger gassers.
Other actual 50cc airframes are quite a bit larger then the H9 260.

I am sure the life span is cut rather short, when using a 50cc up front.

Sure it can be beefed up to handle it, if you dont mind flying a fat..

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Old 05-23-2012, 02:30 AM
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Default RE: extra 260 maiden

that sure would explain for a lot.

Horizon hobby sold that plane with that engine as a combo.

on the 1st flight, the tach on engine read 6500 rpm swinging a 23 x 8 prop right before flight. that plane rocketed out and the aileron servos were stripped.

on my second flight,

i had made the engine rich, since it is still breaking in, which i had not done for 1st flight.

i got 5500 rpm on tach right before flight,
so that would explain why it flew better. top speed was 90 mph on 2nd flight.

i did not use the forerunner on the 1st flight, so don't know what speed it was going.

HH has discontinued the plane, either them or H9.
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Old 05-23-2012, 06:57 PM
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Default RE: extra 260 maiden

Simple answer is that structrures 1st Nodal point in a vibrating structure will be 1/2 its length.

So, your aileron is fluttering. Actually everyones ailerons and all moving structures are fluttering.

What is Flutter?

The ends of the aileron, tip/root, are moving up and down, up and down, up and down due to slack in hinges, slack in servo linkage, slack in servo gears, vortex bubble shedding due to high angle of attack, vortex shedding due to drag which increases by the velocity squared and with the difference in drag between the bottom and top of the airfoil at the trailing edge creates a pressure up/down depending on flight profile. Your tip/root of your aileron will always be flexing as they are a structure under said load. The only question is really how much.

Your servo is trying to dampen out all of these vibrations. If you place your servo linkage at the most common node point the structure at this point is actually NOT moving until a third harmonic or greater is introduced. Therefore your servo is not able to dampen the structural response and the flutter, while not noticeable under most conditions is free to either get LARGER, or SMALLER. Well, obviously you never notice when it gets smaller, but when the vibration/flutter becomes large enough, the dynamic force of structure is large enough to force the servo to move. Generally this strips the gears and your plane just lost aileron authority and probably went into a spin unless you are VERY quick on the sticks and know to apply opposite aileron throw, which may or may not help depending on how much you use.

Placement of linkage.
1) Higher pressure air under the wing is pusing aileron up
2) You do not want to tip stall
3) Pushed up aileron decreases angle of attack
4) Linkage placemtn along lenght of aileron will increase/decrease this flexing of the tip of the aileron
5) If one is trying for VERY snappy barrel rolls on a lightly wing loaded plane where stalling is not an issue, then place linkage at some prime number integer of the length of the aileron towards the tip.

FOREX: 18" Aileron. Ribs every 2" 5th rib is centered on center of aileron. Prime integers of 18/2 will be 1/9, 2/9, 4/9, 5/9, 7,9, 8/9 just to be VERY thorough. Obviously 1/9 and 8/9 are essentially useless as the flexing of the aileron will mean one end is fully functional while the other essentially sits in place. 3/9 and 6/9 are NOT good as the next most common harmonic ossilation of a structure is its length divided by 3. 2/9 and 7/9 length essentially fall under the same problem of 1/9 and 8/9. This leave 4/9 and 5/9 length. This position along the aileron will mean that any flutter of the most common harmonic 1/2, will be trying to move the servo arm back and forth as well. Servos do not like this as their "brain" told them to HOLD @ 'X'. The flutter is trying to move said servo OFF its HOLD spot. Therefore said servo PUSHES back against this flutter canceling the flutter and keeping your airplane in the air.

There is another component to this in that the servo in question has to be able to ACT quick enough to PUSH BACK. This gets into latency, torque curves. Why digital servos are superior essentially. A standard pot(resitor) servo will not Push back with its maximum current(POWER) until said resitor(position sensor) moves by a LARGE margin. So, yes, said servo will be able to bring 'y' torque to bear, it only does so when its position sensor tells it that it has a LARGE movment to under go in a simplifed explanation. A digital servo does not have this limitation as it can bring its FULL current to bear on even a minute needed change. Well, nearly its full current anyways.

Hope that is sorta clear. Others on here can probably do so in a clearer fashion. Gotta go. Questions can get to them tomorrow maybe.

Quote:
ORIGINAL: speedracerntrixie


Quote:
ORIGINAL: BFoote

Ah, you found out why you need stiff ailerons, stiff hinges, stiff linkages, and counter balanced ailerons eh. If the previous statement were true a miniscule servo with no gear slop would be sufficient. Effectively by adding a larger servo, you are damping the system with its resistance due to its torque needed to move it off its assigned ''spot''.

To help eliminate flutter, do NOT place your servo linkage at the aerodynamic center of the aileron. If its a kit, most likely, they predetermined this for you already. Place it at a prime integer value of the AC. 1/3, 3/7, etc.

Enjoy your introduction into vibrations.

Cheers


Can you give a more in depth explanation of this?

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Old 05-28-2012, 03:50 AM
  #13
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Default RE: extra 260 maiden

i just reread your post, as to understand what you are saying, now i know what you said.  i may have to clarify what happened, and more than likely, what i think happened, since it is very much possible that i am wrong.

What i believed to have seen, while plane completely lost control of ailerons, was that the wings were "flexing" or vibrating up and down, and making a terrible noise, as the ailerons were "flapping" up and down.

but now, it makes sense to me:

what happened was that when servos were stripped, the ailerons were not "attached" to a servo, so they began the up and down movement.  since they were doing this, this was then transmitted, via hinges, to wings, and then the wings were doing it as well.

this is what i referred to "flutter" of the wing, as this is what i saw, which was way strange.  but in reality, after understanding it, the ailerons had way too excessive unopposed "flutter" that was then transmitted to the wing. 

kind of like if you placed a streamer on the side mirror of your car, and at low speed, maybe the streamer would fluctuate around, but at high speed, then the mirror will begin to "shake"
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Old 05-28-2012, 05:04 AM
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Default RE: extra 260 maiden

Flutter is caused by the ailerons CG being too far aft - it should be somewhere between the hinge line and 20% of chord
Good servos and tight linkages may overcome incorrect setups byt ther is no mystery about this and no fixes other than to get the balance located correctly.
IF the balance is wrong - a resonant swing can take place- sometimes quite easily and it is destructive
This is not just an "idea " It has been tested and shown to work.
also full scale practice is to balance ailerons .,This done not to change stick pressure but to prevent flutter.
Pulling out of a dive at speed - can reduce unequal pressures on wing/stab which at some point will allow the control surface (aileron or elevator) to "hunt" -at some point this can become a resonant swing -
play with hinge gap if you want to- that is just a patch and or acts as a movement restriction.
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Old 05-28-2012, 08:42 AM
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Default RE: extra 260 maiden

Saw what you described Sat morning at a big bird event. Something happened with the left aileron, that in turn caused the wing to flutter (oscillate) perhaps 8-10 cycles before the wing ripped apart. You were more fortunate than the owner of that plane as it won't fly again.
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Old 05-28-2012, 01:26 PM
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Default RE: extra 260 maiden

when it happened to me, i immediately cut engine down as much as possible and landed plane. the damage on landing was broken landing gear, broken prop (80$), muffler broke, firewall broke. i was able to repair and upgrade servos. have flown place since then ,two more times, last time was today.
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Old 05-28-2012, 01:59 PM
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Default RE: extra 260 maiden

Yup, have 10lbs of tungsten carbide(Old broken milling cutters) as counter weights on each aileron on the COZY(4 person Long EZ) I helped build as he was a family friend. Its normal CG of said aileron was about 40%. Moved it forward to 12%. Most worthless airplane ever. Can't take off quickly, nor land quickly, can't sight see out of it as its low speed handling properties suck, can't do acrobatics with it, effectively can only take off from a paved LONG runway and can get you somewhere else to ANOTHER LONG paved runway, at which time you have to somehow procure transportation to somewhere useful. Now he is building an RV-7 so he can actually go somewhere fun and interesting. He didn't like my brother and I's design for flaps on the COZY. We proved via testing wind tunnel and RC demonstrator that we could place flaps on the rear and the front stabilizer canard improving takeoff distance by over 50% and total load lifted by 25% at the same time while maintaining canard proper stall characteristics. Couldn't add leading edge slats as the rear propeller would have smacked the ground. Actually propeller smacking the ground(FOD) is a common occurrence on COZY/Long EZ on unimproved airfields. Yet another reason NOT to build a cozy or Long EZ.

Quote:
ORIGINAL: rmh

Flutter is caused by the ailerons CG being too far aft - it should be somewhere between the hinge line and 20% of chord
Good servos and tight linkages may overcome incorrect setups byt ther is no mystery about this and no fixes other than to get the balance located correctly.
IF the balance is wrong - a resonant swing can take place- sometimes quite easily and it is destructive
This is not just an ''idea '' It has been tested and shown to work.
also full scale practice is to balance ailerons .,This done not to change stick pressure but to prevent flutter.
Pulling out of a dive at speed - can reduce unequal pressures on wing/stab which at some point will allow the control surface (aileron or elevator) to ''hunt'' -at some point this can become a resonant swing -
play with hinge gap if you want to- that is just a patch and or acts as a movement restriction.
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Old 05-28-2012, 03:25 PM
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Default RE: extra 260 maiden

That and their cross wind handling sucks. I have seen many in the grass on the sides of runways.
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Old 06-02-2012, 01:37 PM
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Default RE: extra 260 maiden

update

just flew extra again with no flaperons this time


the wind was 14 mph

landed into wind with 3 point landing

no flaperons this time.


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