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Jun 19, 2006, 11:04 AM
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Quote:
Originally Posted by Jeremy Z
So when I fly down-wind and I'm losing altitude, it is an optical illusion?
If you're trying to maintain the same airspeed relative to yourself as you were when you were flying across the wind, or upwind, you could call it that. You probably don't help the situation by not taking the wind into account when you turn downwind either.

Quote:
How about when I fly into the wind, and I have to apply down elevator so it doesn't climb or stall?
If you compensate for the difference between the speed the aircraft sees and the one you see, it won't.

Quote:
When I launch my sailplane into the wind, it climbs quickly. I'm not imagining this. When I launch it WITH the wind, I'm lucky not to crash.
Again, this is simply an issue of airspeed. When you launch into the wind, your airspeed is (arm speed + wind speed). When you launch downwind, it's (arm speed - wind speed).

Quote:
So I do believe you that wind may not have anything to do with climb angle, but it sure does effect how quickly you gain or lose altitude. There may be some advanced theory that proves this wrong, but it has not been my experience.
There's nothing "advanced" about it. Your plane flies in the air, which is moving. Once you've left the ground, that frame of reference means nothing to it.

Consider swimming in a flowing river. If you're swimming downstream, to an observer on the bank, you're moving much faster than if you're swimming upstream. Are you swimming any slower going upstream? Is it any harder to swim at the same speed relative to something sitting on the water whether you are going up- or down-stream? Of course not...

Quote:
My point was that the TwinStar II with stock motors does not handle a wind all that well. Sure, you can fly it, but you'll be struggling to keep it under control, and it's not much fun.
It's turbulence that's your enemy here, not wind directly...

= Mike
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Jun 19, 2006, 11:10 AM
Registered User
Quote:
Originally Posted by Arbo
I hope with that wink your just joking. As a slope flyer, wind, or airspeed certainly affects the airframe and lift. As a general rule, you don't touch the elevator to gain altitude (other than acro), you let speed build and thus the lift of the airfoil increases (of course to a point where drag equals it, and different airfoils react differently, but the general idea is there).
You're making Jürgen's point for him; it's not "wind", it's "airspeed" (and in your case, terrain effects) that matter.

= Mike
Jun 19, 2006, 11:10 AM
Registered User
Jurgen Heilig's Avatar
Quote:
Originally Posted by Arbo
I hope with that wink your just joking. As a slope flyer, wind, or airspeed certainly affects the airframe and lift. As a general rule, you don't touch the elevator to gain altitude (other than acro), you let speed build and thus the lift of the airfoil increases (of course to a point where drag equals it, and different airfoils react differently, but the general idea is there).
I am not talking about slope flying, where the wind comes at an angle from below, providing lift (nor thermals, nor gusts, nor turbulence, nor windshear), but a mere headwind/tailwind szenario.

The was for Jeremy, as we had the same discussion inthe MiniMag thread.

Jürgen
Jun 19, 2006, 11:23 AM
Registered User
Jurgen Heilig's Avatar
Quote:
Originally Posted by Jeremy Z
So when I fly down-wind and I'm losing altitude, it is an optical illusion? How about when I fly into the wind, and I have to apply down elevator so it doesn't climb or stall?

When I launch my sailplane into the wind, it climbs quickly. I'm not imagining this. When I launch it WITH the wind, I'm lucky not to crash.

So I do believe you that wind may not have anything to do with climb angle, but it sure does effect how quickly you gain or lose altitude. There may be some advanced theory that proves this wrong, but it has not been my experience.
...
It is just simple flight dynamics - no advanced theory. Take a free flight rubber powered model, and you will see that its climb rate is not affected by the wind. It just drifts along with the wind (and will not sink flying downwind ).

Take the example of your sailplane:

Let's say the model requires 15mph to fly horizontally. Launching it into a 10mph headwind requires a launching speed of just 5mph (15mph-10mph=5mph). In order to launch it downwind, it takes 25mph (15mph+10mph=25mph). If you can't achieve this speed, the model will sink after launch. Using up elevator to prevent the sink and the model may stall.

Jürgen
Jun 21, 2006, 06:56 AM
Marc LR - France
marclr's Avatar
Hi Guys,

Do you have change the CG, or is it perfect in manual ?

Marc LR
Jun 21, 2006, 07:15 AM
Registered User
Quote:
Originally Posted by marclr
Hi Guys,

Do you have change the CG, or is it perfect in manual ?

Marc LR
The CoG as mentioned in the manual is correct.

Ron
Jun 24, 2006, 02:49 AM
Marc LR - France
marclr's Avatar
Thank you.

What about spoilerons or flaperons do you use ?

Marc LR
Jun 24, 2006, 07:24 AM
Senior User
Jeremy Z's Avatar
DrZiplok, Jürgen: I do understand that it is airflow across the wings that lets the plane climb. (airspeed, not groundspeed) However, if my plane can only fly 40 mph, and there is a 20 mph wind, I can climb faster upwind than downwind. Therefore, the wind does have an effect on climb performance. The effect is that I can either have 60 mph worth of wind across the wings or 20 mph wind, which means that flying upwind will allow me to climb 3X faster. If my plane was infinitely fast, it wouldn't matter.

Both of you know this too, so I guess it is only a matter with how it was phrased.
Jun 24, 2006, 07:27 AM
Senior User
Jeremy Z's Avatar
Quote:
Originally Posted by marclr
Thank you.

What about spoilerons or flaperons do you use ?

Marc LR
I use spoilerons, because it is easier to manually compensate. I found that my TwinStar started to dive when I used flaperons, which made it necessary to quickly compensate with down elevator. (or take the time to mix it in with the radio)

Rather than do this, I decided to use spoilerons, and if I take a second longer to compensate, it doesn't matter, as long as I don't give so much spoileron that I stall it.

Either one works fine with the appropriate elevator mixing.
Jun 24, 2006, 08:33 AM
Registered User
Bill Glover's Avatar
Quote:
Originally Posted by Jeremy Z
DrZiplok, Jürgen: I do understand that it is airflow across the wings that lets the plane climb. (airspeed, not groundspeed) However, if my plane can only fly 40 mph, and there is a 20 mph wind, I can climb faster upwind than downwind. Therefore, the wind does have an effect on climb performance. The effect is that I can either have 60 mph worth of wind across the wings or 20 mph wind, which means that flying upwind will allow me to climb 3X faster.
So you think if you are steering a boat along the river and you turn 180 degrees to go with the current instead of into it the boat is suddenly going much slower through the water than it was before? Wrong, wrong, wrong. Only the speed relative to the bank changes.
Jun 24, 2006, 09:44 AM
Registered User
Jurgen Heilig's Avatar
Quote:
Originally Posted by Jeremy Z
DrZiplok, Jürgen: I do understand that it is airflow across the wings that lets the plane climb. (airspeed, not groundspeed) However, if my plane can only fly 40 mph, and there is a 20 mph wind, I can climb faster upwind than downwind. Therefore, the wind does have an effect on climb performance. The effect is that I can either have 60 mph worth of wind across the wings or 20 mph wind, which means that flying upwind will allow me to climb 3X faster.
...
Any airplane only sees its relative speed to the surrounding air mass (true airspeed) and if your model is capable of flying 40mph and clmib at 10ft/s, it will do so - independant of whether it is flying upwind or downwind.

Seen from a fixed point on the ground, the climb angle will look a lot steeper upwind than downwind - and that's what makes it more difficult for RC pilots.

Look for the dreaded "downwind turn syndrom".

Jürgen
Jun 29, 2006, 08:41 AM
Marc LR - France
marclr's Avatar
Hello,

Have maidened the TS2 yesterday : 2 flight, no problem, cool plane.

Have maidened at the same time my new usb cam. See result here : http://slopecontestv03.free.fr/79niort.wmv , i have noticed all to do to be better next time...

Best Regards,

Marc LR
Jun 30, 2006, 03:08 AM
Registered User
PTheDevil's Avatar
Well.. I strapped on a pair of 6X3 Airscrews with prop adapters... Let you all know how it goes in the AM
Jul 01, 2006, 09:45 AM
-plancks only-
Franck's Avatar
Quote:
Originally Posted by Bill Glover
So you think if you are steering a boat along the river and you turn 180 degrees to go with the current instead of into it the boat is suddenly going much slower through the water than it was before? Wrong, wrong, wrong. Only the speed relative to the bank changes.
That puzzled me when i was I kid I know now that wind has NO effect om a planes behaviour, ONLY if you refer the planes position and speed to a fixed ground position (wich you usually do )

One of those funny things i guess
Jul 08, 2006, 06:49 AM
Registered User
Can any one tell me what props i should get? I have:
CC Thunderbird 18 ESC's
Team Orion Platinum Edition 4800 Lipo Battery (7.4 volt)
Esskay outrunner 400XT motors?

Is it even possible to get a good flight with this combo?

Thanks
Russ


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