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Old Mar 06, 2014, 05:11 PM
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Wow, very nice video! Beautifull scene, weather, models and vario. I wish that I had discovered model flying back then.
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Old Mar 06, 2014, 05:15 PM
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To show how it was done in the past.
The location is there where we did, and a lot of these pilots still do, slope gliding, in the Eifel.
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Old Mar 06, 2014, 06:02 PM
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Quote:
Originally Posted by Taurus Flyer View Post
I wrote;
The choise of a location of pitot and static tubes (but also ports and ventury's) are dependent of importancy and possibilities. I always count with the influences.

How I count with? That could have been the learning fact but you didnt ask!

TF
Hi TF,

I am sorry for asking the wrong question, you are right. It was not my intention to start an argument. It is clear that you have lots of experience and you are often willing to share it with others.

I am indeed curious about how you count with influences in this case. Can you tell us more about it?

Many thanks, GF
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Old Mar 07, 2014, 03:57 AM
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Glider Fan,

You wrote:
I am indeed curious about how you count with influences in this case. Can you tell us more about it?

I can tell you more but first let's start with, why did you launched this statement .............

: The location of the other example from your previous post is much better but the probe could be longer to stay away from the leading edge.

..............after I already answered you "The choise of a location of pitot and static tubes (but also ports and ventury's) are dependent of importancy and possibilities. I always count with the influences." ?
See the thread: http://www.rcgroups.com/forums/showp...&postcount=148

This was related to the Taurus I showed in post 146.
http://www.rcgroups.com/forums/showp...&postcount=146

I need the answer to make things clear!!

TF
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Old Mar 07, 2014, 06:12 AM
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Hi TF,

I would love to hear how you count with influences in both cases. To be more specific:
1- Mounting at the wingtip of Sagitta 800
2- Mounting at the LE of the Taurus wing

In the case of Sagitta 800... The working of the pitot-static probe is the Achilles' Heel of the Netto Variometer. Therefore, it is important to know how you did count with influences here.


Quote:
Originally Posted by Taurus Flyer View Post
I can tell you more but first let's start with, why did you launched this statement .............

: The location of the other example from your previous post is much better but the probe could be longer to stay away from the leading edge.
Well, I am in doubt about the length of the pitot-static probe, that is why I have launched this statement. Because of the perspective on the photo, I cannot see clearly how long the is and, how far below and how far ahead of the LE the static orifices are placed. I have understood that it is important to make the tube long enough to stay free of the pressure effects of the wing LE. Again, I am not saying that it is wrongly placed, I just like to know more about it.

Thanks, GF
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Old Mar 07, 2014, 08:22 AM
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Glider Fan,

The answer, you doubt about the length. It nearly couldn't have been another answer, but it was the principle I wanted your answer.
Let's make the story now.

Let us read the content of post 116 for a while, halleluja.



Quote:
Originally Posted by DEAN GRADWELL View Post
Scott,
I used the supplied Westec pitot tube.
I found the same variation with the Eagle Tree setup.
I had a helper call out the numbers and they were all over the place. Concluded it was not trustworthy.
Sounds like you had better results.

Regards Dean
Well, response in 118. let's see:


Quote:
Originally Posted by marnochs View Post
Hi Dean,
Thanks for the reply, I'm going to have to have you look over my EagleTree readout to see if I'm getting the same deviations that you were and I just didn't realise it. That would be funny if the fix is to have the static port "open in the cockpit". On the WSTec Airspeed unit (sm-modellbau.de), did you put it in the tail next to the pitot/static pickup or in the much more convient cockpit? Teflon 2mmID tubing to the cockpit or the squishy silicone stuff (if that's where it was)
I'll have both the EagleTree and WSTec Vario/Airspeed systems installed in my Ventus 2cx for the October AeroTow for testing. Should be interesting
What good is a "Speed to Fly" if you don't know what "Speed your Flying" ...Real-Time

Joe,
Thanks of all of your imput also, but it seems Mike's parallel universe thereom (PUT) may have had reflux as you were mistaken for me and my" lack of understanding" of where to put the static port. The funny part is it's just lazyness that had the static port "open in the cockpit"
My fullsize Citabria has the static port open in the cockpit so I thought "what the heck" lets try it out.....seemed to work OK

Thanks again
Scott

Will report back on the Airspeed readouts (and stability) under different configurations .
So Scott is flying around in a full size Catabria,
My fullsize Citabria has the static port open in the cockpit so I thought "what the heck" lets try it out.....seemed to work OK

And you write:
The location of the other example from your previous post is much better but the probe could be longer to stay away from the leading edge.

Do you see the "scatter"?


First my post about the static tube of "my full size Catabria" (Scott):

http://www.rcgroups.com/forums/showp...&postcount=127

So the static "open in the cockpit" was nonsense to impress!


Well a new episode but it was important to show this piece of history of the thread.

Reality!

I wrote;
The choise of a location of pitot and static tubes (but also ports and ventury's) are dependent of importancy and possibilities. I always count with the influences.

First see the picture 1

What is written are many dozens of documents about airspeed measurement, even documents long before there were airplanes flying (heavier than air!), for mining for example 1882.
A short impression I show over a period of 30 years

The second picture does show what we are talking about, the position of a pitot and static tube related to the leading edge of the wing, European information, Germany.
Can we use this? No? Well there are dozens of other sources.

Clou of the story is what do I need I which situation and were have I to count with? Vibrations, accuracy, linearity, complexity, drag, rangeability, (weather) conditions, variations of AOA, maintenance, reliability, etc.

And then, what are the consequences of a choise.

The Taurus pitot and static tube is used for measurement but main task is airspeed control so, for example the AOA is a variable. Also calibration can be interesting but is not too important to control the airspeed. Weather conditions is important see the picture in earlier post!.

The Sagitta? See the picture 3, sometimes I have to find out myself and than this can be the situation. The end of the story is, I know the influences of a choise to count with by comparison. I also can use the perfect pitot and static tube, but........ what will rest after a moment of cartwheeling?

So a photograph is a moment but background often is many hours of research and development and taking decisions.

Last picture, the TE ventury also used in the video but older, not complete, a calibrated part isn't there but in a box. It looks like a simple divice but this part did take a long time to make. Within the dimensions there was no information in the periode this part was made.

Polars and the calculation "speed to fly", the accuracy of measurements is leading for useability of polars, so squared all what is written about airspeed measurements in general.

TF
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Old Mar 07, 2014, 08:39 AM
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OK, many thanks for your time.

Best regards, GF
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Old Mar 07, 2014, 11:57 AM
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A short note about overshoot.

For full scale variometers (you know it!), sometimes the time constant is specified (called tau).

After the input is changing for example from constant in a ramp or changed as step, the indication (or output signal) has reached the new measured value or ramp of the input signal after about 5 times this time constant (=5 x Tau). The new signal has reached about 64 % of the new signal situation after 1 tau, (+/-0,2 sec for my instrument) so this can be heard!

To anwer your question in the first time I called that 5 x tau period as the time delay to make things easybecause an estimation of this ''5 x tau'' can be made on moments the direction of movement is changing.
One more remark, moving the sensor slowly as shown in your movies doesn't give any information about the reaction speed of your setting. With enough damping/smoothing every instrument can pass those tests. At the end of your video its easy to hear that the acoustic signal has significant delay. Did you measured the delay when the sensor is moved quickly up and down?



Another video, some older instrument, some faster variations. This is a glider so the TE tube will be positioned on the nose, not at a wingtip.

Sensor- and audio test of a variometer for a RC model glider airplane (1 min 18 sec)



The period of (5 x)tau doesn't change and isn't dependent of the variation of the incomming signal. No overshoot is detectable, and that has mainly to do with the principle of the measuring system.

For thermalling it's also important to observe with what altitude difference the new direction is detected, it's even in this second video most of the time within 10 cm.

One fact is important to make these video's, weather conditions outside, barometric pressure rizing falling and wind, and processing of tones pulses, which facts sometimes results in some more delay.

For full scale the fastest variometers were the most valuable and often could be damped by the pilot when needed.
Are these instruments faster? Google for that and let me know if you find one! Full scale but also for model airplanes.



TF
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Old Mar 09, 2014, 06:50 AM
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Quote:
Originally Posted by PapaHotel View Post
Hi GliderFan,

I think that you are looking for this site:
http://www.xerivision.com/index.html

Check also this interesting document:
Which CL are you really flying?

And the missing instruments are coming soon. I will start a new thread about what I am building.

Best regards,
Sinan
For Glider Fan and "who is interested".
Because It takes some time for Sinan I updated the last post to show some background information about overshoot and response time, also for faster variations of vertical speed.
When observing the position of AOA or airpeed measurement parts, see the photograph. the red circle.

Signal processing has to do the job!

Cees
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