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Old Jul 25, 2012, 09:42 AM
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USA, IL, Wheaton
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Colonel
Found your set-up post from June. Lots of good detail.

http://www.rcgroups.com/forums/showp...&postcount=544

Have your repairs changed the All Up Weight much? Still Circa 780 g?

Good to hear that stock gear makes a nice flyer

Joe
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Old Jul 25, 2012, 11:18 AM
So I'M meant to be in control?
Colonel Blink's Avatar
Ilkley, West Yorkshire, UK
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Originally Posted by DuPageJoe View Post
Have your repairs changed the All Up Weight much?
If you are talking about the slight...ahem...mishap of the maiden launch being made with the elevator reversed (wrong model selected on Tx) then the only repairs required were pushing the nose back together (I'm still not convinced by double sided tape) and then a 6" length of packing tape on the top of the nose. So what's that - 3g??? No, the weight is still the same!!!
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Old Jul 25, 2012, 07:01 PM
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Denmark, kbh
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Originally Posted by Colonel Blink View Post
...It might just be me - and the fact that the Moor (being a lumpy hill) always has very bumpy air close to the ground - but I think that the model likes to have the motor on at low throttle for control when descending in the circuit or on final to land. Because the setup I have 'whistles' at very low throttle I have it whistling in the circuit; open the throttle one click more and you can hear the normal motor noise and can keep s&l. The low throttle opening keeps some air over the control surfaces and gives manoevring authority at landing speeds. It wouldn't do this with ailerons of course; the prop wash only works over the empennage. But then again, with the more positive control of ailerons, a 4ch version may not need the motor running....
Col Blink,

good to hear your are getting some airborne time on your plane finally. May I propose that you get the aileron servos installed asap. The ES2 flies so much better with them (I, too, maidened mine without ailerons, but installed them immediately afterwards. Never looked back). Being a lazy bum, I mixed in 20% aileron -> rudder, which produces nice clean turns on one stick. Furthermore, I can then use my left hand for the FPV camera pan potentiometer :-)

The ailerons will either allow you to more effectively compensate for moor-bumps on final, or you can set them up as spoilerons, allowing higher approach speed, but destroying the lift, so the plane will actually come down.

PS: I also noted the "pronounced" stall, but with ailerons it's easy to correct.
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Old Jul 26, 2012, 03:22 AM
So I'M meant to be in control?
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Ilkley, West Yorkshire, UK
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Originally Posted by mike_o View Post
May I propose that you get the aileron servos installed asap. The ES2 flies so much better with them............I also noted the "pronounced" stall, but with ailerons it's easy to correct.
It won't be long - probably after I have been on my hols.

Your comment about correcting the wing drop at stall with the ailerons is interesting. At the stall, the wing drops because one wing stalls before the other (often due to not flying perfectly balanced or directly into wind). Trying to pick it back up with ailerons means that the aileron on the 'dropping' side goes down, increasing the effective angle of attack. This will put that wing deeper into the stall, and in full size flight is a well known killer when it happens low down. Pilot training drills into you that when a wing drops in a stall, you pick it up again with rudder, not aileron. Basically you accelerate the stalled wing by yawing away from the dropping wing.

Possibly, rather than you picking up the stalled wing with ailerons, what may be happening is that the stall is occurring, the wing drops, the nose goes down and the model accelerates and unstalls the wing, then the ailerons enable you to quickly correct the situation. I would think that it could probably be difficult from the ground to seperate the various actions & reactions. Hence the above is all pretty academic, and what you are doing seems to work for you!!!!!
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Old Jul 26, 2012, 03:29 AM
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Originally Posted by Colonel Blink View Post
...
Your comment about correcting the wing drop at stall with the ailerons is interesting. At the stall, the wing drops because one wing stalls before the other (often due to not flying perfectly balanced or directly into wind). Trying to pick it back up with ailerons means that the aileron on the 'dropping' side goes down, increasing the effective angle of attack. This will put that wing deeper into the stall, and in full size flight is a well known killer when it happens low down. ...
First of all: When your model always stalls to one side, you should try to fix the problem. Check for warps and/or uneven lateral weight distribution. Reduce your elevator throws. You should be able to pull "full-up" at low speeds without stalling.

In contrary to full size aircraft, our models pick up speed very quickly after a stall, hence it is fairly easy to correct a dropped wing with ailerons.

Jürgen
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Old Jul 26, 2012, 04:16 AM
So I'M meant to be in control?
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Ilkley, West Yorkshire, UK
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Originally Posted by Jurgen Heilig View Post
You should be able to pull "full-up" at low speeds without stalling.
I presume that you mean with power on?
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Old Jul 26, 2012, 06:26 AM
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Originally Posted by Colonel Blink View Post
I presume that you mean with power on?
No! Power-off of course. With power on, the increased airflow over the tail makes rudder and elevator more effective. You just want enough elevator authority, that you can't stall the model during gliding.

Jürgen
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Old Jul 26, 2012, 07:20 AM
So I'M meant to be in control?
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Ilkley, West Yorkshire, UK
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Originally Posted by Jurgen Heilig View Post
You just want enough elevator authority, that you can't stall the model during gliding.
Why?
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Old Jul 26, 2012, 11:09 AM
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Originally Posted by Colonel Blink View Post
Why?
Because this way, you are less likely to stall your model unintenionally, while retaining maximum maneuverability. It also gives you maximum precision, as you are using the full stick movement.

Jürgen
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Old Jul 26, 2012, 11:31 AM
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Originally Posted by Jurgen Heilig View Post
- -- You just want enough elevator authority, that you can't stall the model during gliding.

Jürgen

Colonel

Does your transmitter support dual rates? You might want to set the throws at low rate to give the limited elevator travel that Jürgen suggests. I should set up my 2M Riser sailplane to make easier approaches this way, I am interpreting the sentence as "You want just enough".

Joe
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Old Jul 26, 2012, 03:00 PM
So I'M meant to be in control?
Colonel Blink's Avatar
Ilkley, West Yorkshire, UK
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Originally Posted by Jurgen Heilig View Post
Reduce your elevator throws. You should be able to pull "full-up" at low speeds without stalling. Power-off of course......Because this way, you are less likely to stall your model unintenionally, while retaining maximum maneuverability. It also gives you maximum precision, as you are using the full stick movement.

Jürgen
I'm really having trouble visualising this......

If we assume the elevator is 'neutral' when the model is gliding in equilibrium (constant speed), then any amount of 'up' elevator will increase the AoA of the wing, thereby increase lift and the model will attempt a climb. But the energy has to come from somewhere, and that somewhere is the speed. The primary effect of elevator is on pitch, the secondary effect of elevator is on speed. So even a tiniest bit of up elevator will begin to bleed the speed off. The more up elevator, the quicker it bleeds off. But whatever the amount of elevator, the final result is the same - the speed drops to below the stall speed and down we go.....

So I'm still not sure what you mean by "You should be able to pull "full-up" at low speeds without stalling".........
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Old Jul 26, 2012, 03:19 PM
buyer of the farm
United States, FL, DeLand
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Originally Posted by Colonel Blink View Post
I'm really having trouble visualising this......

If we assume the elevator is 'neutral' when the model is gliding in equilibrium (constant speed), then any amount of 'up' elevator will increase the AoA of the wing, thereby increase lift and the model will attempt a climb. But the energy has to come from somewhere, and that somewhere is the speed. The primary effect of elevator is on pitch, the secondary effect of elevator is on speed. So even a tiniest bit of up elevator will begin to bleed the speed off. The more up elevator, the quicker it bleeds off. But whatever the amount of elevator, the final result is the same - the speed drops to below the stall speed and down we go.....

So I'm still not sure what you mean by "You should be able to pull "full-up" at low speeds without stalling".........
I agree Colonel, I don't think there is any trim adjustment that removes your obligation to fly the plane. That's one that seems reasonable at first blush, but when analyzed further falls apart as you demonstrated.
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Old Jul 26, 2012, 03:35 PM
So I'M meant to be in control?
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Ilkley, West Yorkshire, UK
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As Jürgen is by far a better pilot than I, I'm sure that he has a valid point to make... its just that I am not grasping it!
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Old Jul 26, 2012, 04:16 PM
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Originally Posted by Colonel Blink View Post
I'm really having trouble visualising this......

If we assume the elevator is 'neutral' when the model is gliding in equilibrium (constant speed), then any amount of 'up' elevator will increase the AoA of the wing, thereby increase lift and the model will attempt a climb. ...
The first part you have already understood. When gliding in a trimmed state, the model is already sinking at a constant rate, exchanging potential energy (i.e. height) into kinetic energy.

If you start to apply elevator, you increase the AOA and also the lift of the wing. The model will slow down. When the model slows down, your elevator becomes less effective and you need a bigger throw to keep the AOA up. The model slows further down, and so on ...

The sweet spot is reached when the model will fly at its highest AOA, with the slowest possible forward speed without stalling. While the forward speed is at minimum, the sink rate is much higher than with the elevator at neutral.

Any more up elevator in this situation and the model would stall, either by dropping the nose (good), or dropping a wing (not so good).

Jürgen
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Old Jul 26, 2012, 05:15 PM
So I'M meant to be in control?
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Ah, I understand the point you are making now, Jürgen! But I'm not sure that being able to get an aircraft (model or full size) to gently 'mush' down at minimum speed, rather than drop the nose or wing in a pronounced or even sudden stall is purely a factor elevator throw.

For instance, a PA28 will mush with the yoke pulled right back into your stomach whether flown in balance or out of balance; a Robin 2160 is always ready to drop one or other wing in a stall unless the ball is slap bang in the centre; and (from what I understand) a Bowers Fly Baby has a stall that is sudden and can take even an experienced pilot unawares.

I believe it has more to do with the overall aerodynamics rather than just elevator throw - but I'm no expert, so I could be wrong.

Personally, I won't be reducing the elevator throw to less than the recommended amount - I only put it into the stall as part of a (normal) initial flight program. Know thy enemy!
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