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Old Feb 18, 2012, 09:43 PM
launch low, fly high
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Cees,

If you are not interested in discussion of opinions about the validity in using various forms of instrumentation in XC, then I would suggest that you refrain from discussions on the "off topic" subject and instead keep to the subject of instrumentation and implementation thereof that you have clearly outlined to be your intended subject.

I also might suggest that the source of differing opinion may not be bad or incomplete information, but rather, a conclusion that is based on a differing perspective, a perspective that has included over a quarter century of RC XC flying, along with the technical background to understand the details of the various forms of instrumentation.
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Old Feb 18, 2012, 10:45 PM
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Quote:
Originally Posted by Joe W View Post
Cees,

If you are not interested in discussion of opinions about the validity in using various forms of instrumentation in XC, then I would suggest that you refrain from discussions on the "off topic" subject and instead keep to the subject of instrumentation and implementation thereof that you have clearly outlined to be your intended subject.

I also might suggest that the source of differing opinion may not be bad or incomplete information, but rather, a conclusion that is based on a differing perspective, a perspective that has included over a quarter century of RC XC flying, along with the technical background to understand the details of the various forms of instrumentation.
Joe

I did start this thread to contribute in gaining some information.

Discussion about rules are made ​​based on available products.
These products are made based on commercial background.
If you want to change the rules you will observe the available products and is the key for results!.

I fly my models based on my personnal developments and experiences, so only can show my conclusions when I campare for example used systems.but also the way contests are organized.

Some time ago I did contribute in DS see this thread about measuring of airspeed.

http://www.rcgroups.com/forums/showt...1581467&page=6

Have special attention for post 77.



Cees
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Old Feb 23, 2012, 05:13 PM
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Gents.

I'm searching for data whichI I can not find in documentation of manufacturers either it is formulated a way it isn't useable.
I need this data for some calculation.
An example.
The lowest measurable speed of climbing that is acoustic indicated for an instrument can be 5 cm/sec, that's 2 inch per second.
When flight is leveling after climbing and after that the plane is falling a deadband of for example 10 cm, is 4 inches is needed to generate a acoustic falling signal, the speed of falling at least has to be again 5 cm/s or 2 inch per second to be detected and signalled.

I am interested in the deadband values.

These data can be generated by moving the fuselage "up" and "down" by hand and estimate the difference of altitude that is needed to generate the acoustic signals.

Can you give me some examples of these values of deadband of used instruments, so hysterese "around" zero to inverse the sigalling from minimum detectable/measurable speed of climb to sink and vv?
Another name for hysterese can be response sensitivity.

Cees
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Old Feb 24, 2012, 02:22 PM
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Cross Country Soaring

A forum for all things related to Cross Country Soaring - large sailplanes designed for cross country, electronics such as variometers !!




Gents,

To show my question I did make a short video of the variometer of the ASK18.
This is an analogue TE variometer with ventury and can be combined with airspeed measurement.
The ventury is shaped 30 years ago for this plane and was combined with an older variometer.

You see climbing and sinking at nearly lowest value of speed of 1 inch/sec, when reversing from climbing to sinking and vv you can onserve a deadband, of about 2inches.

In the end two short pulses of air through the ventury to show the effect of lower pressure by speed and the result for the TE compensation, a positive signal. Interrupting this airflow does show a short "fall" signal.

ASK18 glider 4.3m TE compensated variometer (1 min 13 sec)


Cees
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Old Mar 03, 2012, 09:21 AM
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Gents,

My thread isn't really a goldmine of information for me but, ther are other sources and wih success.

Characteristic of the situation of course is the fact the products that are delivered are base for know how of the users and not all kind of theoretical background issues.

The variometers used for modeling are simple and based on differentiating of altitude measurement. A known fact.

Profit? easy manufacturing and for that reason popular these years.

Adjustment seems to be established at +/-5 cm/sec as lowest value to (tone) signal of the vertical speed to prevent a bumpy signal and not a kind of a "deadband" of altitude variation of the high resolution altitude signal.

One of the reasons can be the chosen principle, differentiating, combined with a noisy signal generated by the total energy probe,

But ..... with adjusting of these 5 cm/s, is 2 inch/sec, important information will be lost. I am afraid.

It is interesing that the original basic principles still are preferred for 1:1 gliders in contests. The system I use in the Sagitta is an example of one of these principles and known as "fast" and aerodynamically also interesting for our small ships for reason of the low drag of the small Prandtl Rohr (pitot and static tube) when compared with a nearly square on flight direction positioned part of a TE tube.

So the fishing float for the contest (XC) pilot still can be an old variometer principle, a principle that was nearly forgotten.

When you have other experiences or information? let me know because that will be interesting!

Cees
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Old Mar 20, 2012, 02:58 AM
Pat Chewning
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Quote:
Originally Posted by Taurus Flyer View Post

The variometers used for modeling are simple and based on differentiating of altitude measurement. A known fact.
I think the ACE Thermal sniffer used a hot-wire anemometer (thermistor) to measure the speed of the air exiting the chamber to determine rate of climb and sink. I do not think it measured the rate of pressure (altitude) change .......

Yes, modern digital electronic rate-of-climb instruments directly measure pressure (altitude) and then differentiate to get the rate of climb.
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Old Mar 20, 2012, 09:37 AM
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pchewn, hi

For the ACE Thermal Sniffer it is more likely two (self heating) thermistors were used, but not to confuse with "hot wire".
This "thermistor principle" also was used by Moore and other brands in variometers in the 1:1 gliders.
The thermistors I did use myself in the past were much smaller than the head of a pin and connection wires as thin as a hair.

We also can write, it's a pneumatic way of differentiating, compare the new value of altitude pressure with the old pressure in the chamber, which of course is following the ambient pressure with use of a restriction.

All varios we can buy these days indeed are based on the technical possibility of measure the flight altitude with high accuracy and solution. Problem can be damping of the differentiating and I think that's why the sensitivity normaly is reduced to plus or minus 0,25 m/sec.

The chamber methodes don't need that damping, to show in my video in post 49 and that's the reason I think these methodes can be about twice as sensitive.
It can be an important fact with very weak thermals (of trees?). The "chamber" method does need more attention for calibrating and that makes it less interesting for manufacturers.

Signal processing of all "new" variometers of course is the modern way, show a lot but without telling us the important information, "speed to fly", which is of highest importancy in 1:1 contest glider.
I am kind of surprized I don't hear anything of that in XC gliding and also not in the "poll".
Still interesting to hear of experiences with variometers and airspeed measurement.

I myself do some research for measuring of low airspeed with hot wire sensors as a backup method, see the picture of one of the prototypes for the ASK18.


Cees
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Old Mar 24, 2012, 04:36 AM
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@Zenoid Very impressed!
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Old Mar 26, 2012, 06:06 AM
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Thks Gary. I've been flying this week end, two gliders were equiped. I'am analysing data now...Regards
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Old Mar 26, 2012, 01:45 PM
yyz
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I just switched to this vario and it's by far the best one I've flown with:

http://www.wstech.de/english/index_e.htm

Several hours of gps triangle flying with a 1:3 scale ship this weekend in moderate conditions. The vario tone is pleasant, response very fast and the total energy compensation was great, right out of the box. A minor bit of tweaking and it will be perfect.

It has a bunch of nice features that you can read about but the equivalent of a full-scale 30 second average is HUGE. As I was bombing around the field, I would pull up into a thermal at speed, make a turn or two, listen for that average announcement and make a quick decision whether to stay or push on. Absolutely fantastic!

The customer support so far has been nothing short of great,

Mike
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Old Mar 27, 2012, 09:39 AM
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Mike,

Thanks for the post and great that you are happy with the wstech.
With that vario you have the tool to observe the flying conditions and to make decisions during thermal flying.

But,

Question, do you understand the Netto and Relative Netto Variometer and Mc Cready? Why these can be the usefull tools to fly after you decided to "push on" for the track? So the instrument does tell you how much to push on?

See also this earlier post, press the blue button and adjust McCready is the action to have the optimal "speed to fly".

http://www.rcgroups.com/forums/showp...1&postcount=12

So, thanks Mike and summer is there so many happy flights.
Thanks.

Cees
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Old Mar 27, 2012, 10:31 AM
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Cees,

Yes, I understand netto and relative netto as I flew full-scale cross-country and racing for a number of years. My thinking is that it would take a great deal of work to accurately determine the glider's polar to take advantage of such features. You first need very accurate airspeed and lots of patience to measure the polar.

I like the idea of having a speed director (push/pull indicator) but I think setting up the gadgets to do that is too much effort for most pilots. Some of the better pilots set the MacCready setting at "1" (conservative) and then use their experience, seat-of-the-pants feel and that thing between their ears to estimate the lift strength ahead and thus how fast to fly. Optimal? No. Practical and flexible? Absolutely.

Again, my feeling after doing some research and having flown with "the other two" varios is that Wolgang Schreiner (wstech) has set the bar high for other variometer manufacturers. Total-energy compensation, for example, is a tough nut to crack and that was the most important feature for me.

Best of luck in your efforts and I truly hope you can make this kind of technology easily accessible to the average pilot,

Mike





Quote:
Originally Posted by Taurus Flyer View Post
Mike,

Thanks for the post and great that you are happy with the wstech.
With that vario you have the tool to observe the flying conditions and to make decisions during thermal flying.

But,

Question, do you understand the Netto and Relative Netto Variometer and Mc Cready? Why these can be the usefull tools to fly after you decided to "push on" for the track? So the instrument does tell you how much to push on?

See also this earlier post, press the blue button and adjust McCready is the action to have the optimal "speed to fly".

http://www.rcgroups.com/forums/showp...1&postcount=12

So, thanks Mike and summer is there so many happy flights.
Thanks.

Cees
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Old Mar 27, 2012, 11:28 AM
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Thanks for the usefull input Mike, yes these subjects will have my attention for while, and what I wrote, many happy flights.

Cees
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Old Jul 16, 2013, 07:25 PM
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A little update about development of variometers.
These days we see a lot of new vario(meter)s, all based on modern digital sensors and small of dimensions. Most of these with all kind of whistles and bells.
For me response sensitivity combined with low delay times are still the most important facts related to the high performance of gliders especially for centering of the small thermals. Also the communication with the pilot needs a lot of attention.
To meet these requirements and gain experience I have finished a new prototype. This is strict an RF transmitting audio vario, only will be expanded with TE and relative netto capabilities, still experimental assembled but compact to do measurements. All kind of tests will be finished before the next step can be done, definitive lay-out and casing.
All parts are of own design, pneumatics, electronics and rf system.

I cannot predict if this ever will be commercial interesting. The measuring data are better than these of commercial systems but construction and calibrating is time consuming and more bulky so only applicable in large models.
Some premature data,
Minimum differences in vertical speed that can be detected by the measuring system is 1 cm/sec with a hysterese vertical of 5 cm.
Supply voltage 9 V DC 40 mA.
The transmitter is crystal stabilized and transmits at a portable microphone frequency.
Cees
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Old Jul 17, 2013, 07:16 PM
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i made a video to archive with the other design documents.
With some added information it's the best way to show the functioning of the instrument.
High sensitivity and a fast response are most important and the best way the instrument can be informative beside the visual observation of my glider model. In weak thermals the instrument can be the key fact (in cross country).


RC Glider wireless audio variometer (3 min 36 sec)



Cees
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