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Wednesday, February 6, 2019

New version of the RC throwmeter App available

In this version, Yannick changed a bit the main screen, by limiting the display to one digit after the decimal point instead of two. This is more confortable for the reading as the last digit was always changing and because we don't need this level of precision.

He also added the planet-soaring article on the start page as an embeded user manual.

This new version can be downloaded here:


To answer some questions I received: There is no possibility yet to connect 2 devices to the same App as the BLE connection is point to point, unlike Wifi. A simple solution consists in using a second smartphone.

It seems the App cannot be installed on Android 4.4.4 (Kit Kat), but I don't think we will troubleshoot why as this version of Android is more than 5 years old now.

I will try to pair an iOS smarphone with the device, but the manufacturer says his device is not compatible with iOS. In case it work, which I don't think, I will update you.

Saturday, February 2, 2019

Make your own BlueTooth RC Throwmeter !

by Yannick Selles and Pierre Rondel


The purpose of this article is to propose you to "build" your own Bluetooth throw-meter for a very reasonable cost. It doesn't require any soldering or cabling. You just need to have access to a 3D printer and that is all !

The original idea came to Pierre's mind after finding by chance on aliExpress an all-in-one 6 Axis Bluetooth Digital Angle Accelerometer Module.

Initially, he bought 2 exemplars of the board, then bought a 1s lipo, a micro switch, and designed the case and the clips. Later he discovered that the same component existed with a case the battery, the switch, the charging plug, and a charging cable for 4 euros more. It saves a lots of soldering and cabling, so the final version we propose hereafter is based on this model.

The component

The component is the BWT61CL  from Wit Motion, a Six axis Bluetooth attitude angle sensor with battery incorporated. It can by bought on aliexpress or amazon US and cost around 20 Euros, free shipping.

It is based on the JY61 sensor, has Bluetooth or serial connectivity, integrates a dynamic Kalman filter algorithm, an internal voltage stabilizing circuit module, voltage 3.3v~5v. The only drawback it has is that the Bluetooth BLE is only compatible with android. The battery has  a 150mA capacity so last for a long operation time.

Where to buy


  •     Voltage: 3.3V-5V
  •     Current: <40ma li="">
  •     Size : 51.3mm x 36mm X 15mm
  •     Weight : 16gr
  •     Dimension: Accelerated speed -3d Angular speed -3d Magnetic field-3d Angle-3d
  •     Air pressure 1d
  •     Range : Accelerated speed -±16g Angular speed -±2000°/s Angle---±180°
  •     Stability: Accelerated speed -0.01g Angular speed -0.05°/s
  •     Attitude measurement stability: 0.05°
  •     Output content: Time, Accelerated speed, Angular speed, Angel.
  •     Output frequency:100Hz
  •     Date interface: Serial TTL level Bate rate--115200(default and cant be changed)
  •     Bluetooth transmission distance : >10m
  •     Support for Android
  •     Working time: 2 to 3 hours (full charge)


Building your RC Throw-meter

As I said in introduction, the work is limited to the 3D printing of the clips that allow to fix the device on the trailing edge of the glider. It has been designed on DesignSpark (original file .rsdoc), and I'm providing the .rsdoc original file in addition to the STL file.

The clips is removable so the device, its clips and the charging cable can be carried/stored in the plastic box it was received in.

Just print the part, in PLA or PETG or ABS, 100% in fill for me. The dimension is optimised for F3x plane wings and tailplanes. To protect the surface of the control surface and avoid the clips to slide/shift, I added a piece of rubber (a small piece of bicycle inner tube) on the clips surfaces, with double side tape.

Print the sticker using the .pdf provided. Prior to apply it, don't forget to remove the other sticker. Protect the printed paper with transparent tape at the top, and double side tape on the other side, and position it on the top of the case, respecting the correct orientation (Charge, On/Off). This will give you the orientation when using it, pointing where is the hinge.

The App

The Android App has been developped by Yannick. The .apk file can be downloaded from here:   Android App .apk file (new version available from the 6th of February 2019)

The App is divided in several screens, the start screen giving access to the top left menu, the "Sensor BT" screen to bind the App with the throwmeter, and finally the "Throw Meter" screen where everything happens once binded.

Using your RC Throw-meter

Charging the battery 

Connect the cable provided to the balancer Plug. The red led is ON during the charge and switch off once charged

Switching on your Throwmeter

Move the sliding switch from right to left. The blue led is blinking which indicates that the device is waiting for the binding.

Pairing your Android smartphone for the first time

On in the parameter/bluetooth menu and scan for new device. The RC throwmeter will show as HC-06. When asked, enter the code 1234. The throwmeter is now paired, you can open the App.

Binding with the App

Select the menu on the top left, then open "Sensor BT" and select HC-06 or click on SCAN if the device doesn't appear. Once selected you can return on the start page, Open the menu on the top left and select "Throw meter"

Very first calibration

If the device is providing inconsistent or weird measures, it probably needs a full calibration using the manufacturer App you can download here.  To do so, once selected the correct chipset model, click on SET (top left) and then "Acceleration calibration".

Reset Angle 

The device is supposed to do a calibration at startup. It is recommended to do it with the device installed on a horizontal surface. Once done, you can clip the device on the leading edge of control surface you want to measure. When your control surface is at its neutral position, proceed to a  new "Reset Angle" in order for the device to know its spacial position and be ready to measure the angle.

Travel setup 

Measure the chord of you control surface and click on the chord field at the top of the screen to enter the value. There is no unit so it can be mm or inches. Travel will be shown in the same unit.

Max UP and Max DOWN

This is a very useful feature that allow you to quickly measure the Max UP and DOWN travels of a control surface.

SET Max UP and Max DOWN

If your objective is to do the settings, not to measure, you can enter the Max UP and Down value separately to indicate to the App to display an alarm (Red color) when the max value is exceeded.

When the travel value exceed the max Value set, the corresponding line is going RED, but will continue to record the max value, even if it is above the limite. So you need to reset time to time to erase the max travel recorded and check your setting.

Hope you will enjoy this Bluetooth RC Throwmeter ! We will probably release new versions in the futur, but be patient.

Sunday, January 20, 2019

Finally, my first flight of 2019 !

Happy new year to all ! Best wishes for 2019 !

I finally could do my first flight of the new year:  Nice weather, very light breeze but enough to fly with the Stribog+, and good company yesterday afternoon in Quincieu. Some pictures here.

Thursday, November 1, 2018

What futur for F3F ?

Hello all,

No ... I will not talk about the drone law that is coming, this is another topic :) !

Following the F3F world championship in Rügen, I think it is the perfect time to make a step back, to learn the lessons and think about the futur of F3F:

Personnaly, the 3 main lessons learned in Rügen are:

  1. A round with 63 pilots can take between 2 hours and 3 hours depending of conditions. During this time window, flying conditions can change a lot. For exemple in the morning when the air is still wet and the drying when the wind is raising, leading to 10s time difference, if not more.
  2. Starting order draw must be carefully done, which was not especially the case in Rügen
  3. When groups scoring happens (round interruption or end of the day), scoring can become very unfair because of the third man effect.

F3F is a nice category because rules are simple, and because we are flying in very different and nice to amazing places. All this make me think that participation will increase in the futur and competition will be even more larger, especially the world championship.

We have 2 years before the next WC. Why not brainstrom in order to make the rules to evolve in order to organise fair competition with a large number of pilots, an ensure everybody enjoy and not consider that sometimes F3F is just like casino, depending too much of the stating order ... or, at the opposite, to conclude that the current rules are perfect as they are today, who knows !

On top of that, I think there are few point in the rules that should be clarified to avoid interpretation like penalties in case the round is cancelled, round interuption reset in case of flight attempt but not valid, etc ...

Personnaly, I don't want to see people who don't fly F3F to try to impose us rules that we don't share, as it has been in a recent time.

As a starting point for this brainstorming, why not first reconsider is the scoring method. France proposed a rule change in 2010. Timing with CIAM calendar was wrong so I think the proposal didn't reach the Plenary meeting. Also, at that time, community was reluctant to this sort of change. During the technical meeting at Donovaly in 2014, I re-explained this scoring method and some people thought further and I could feel some interrest in some nation. Maybe today time has past and with experience of large competition, people are now ready in their mind to look at this rule change with opened eyes.

So here is the rule proposed initially:


F3F rule change proposal

The objective of the present rule change proposal is to modify the pilot round result calculation to use the round average time instead of the best time. This make the round ranking fairer in case of group scoring. For details description, please refer to the presentation included in this document.

The result of the flight is stated as the time in seconds as hundredths of seconds obtained by each competitor. For the purpose of calculating the result of the round the competitor’s result is converted this way:

1000 * Pw/P

where Pw is the average result of all competitors and P is the competitor’s result.

Reasons behind are:

  • In case of group scoring, the final ranking is made much fairer 
  • By reducing the “third man effect” final ranking is made more consistent with real man on man ranking 


FAI current scoring formula

F3F scoring is based on a comparison between the time of the run and  the best time of the round:
FAI = 1000 * Best Time / Pilot Time (Best time is used as the reference)

The amount of points you get after your run depends on 3 parameters:

  1. Your skills (the parameter we want to measure).
  2. The flight conditions you get during your run (that induces the famous "lottery effect") 
  3. The flight conditions during the best run ( that induces what I call "the third man effect" and adds some additional "lottery effect" to your own run.

"Third Man Effect"

The number of points you get depends on your run but it also depends on what happened during the best flight:

- A "top pilot" got the "1000" with average conditions
- A top pilot got the "1000" with "the thermal of the day"
- An "average pilot" got the "1000" with a "standard" thermal

Between these 2 pilots: Who is the winner ?

You think this is Pilot 2 ?

The real answer is : we can't know !
The final ranking depends on the "third man" : the guy who wins the rounds

Because of "third man effect" today FAI scoring method may make the final ranking not coherent with the real man-on-man ranking. The "third man effect" enhances the lottery effect.

To reduce the "third man effect" it is proposed to replace the best time of the round by the average time of the round

New = 1000*Av.Time / Pilot Time

Using the average time instead of the best time makes the reference time much less sensitive to flying conditions. Lottery effect due to third man effect is quite cancelled. But lottery effect related to your own flight remains the same. It has been verified that both methods give quite the same ranking when flying conditions are stable. Differences may occur when flight conditions are very variable . They always make final ranking consistent with man on man ranking.

Group Scoring

It is well known that group scoring can be dramaticaly unfair. This is the case when a pilot get a huge thermal scaling down the scores of all other pilots in his group (but having no effect on the other group).

Exemple: first 2010 competition in France (only 3 rounds with group scoring in the third round)

Pilot “A” makes a 35s => only 2 pilots in his group are around 820pts and all the others have (much) less than 800. On the second day the air is much lighter but much more stable => in the second group more than half pilots have (much) more than 900pts. At the end of the comp all pilots in the top ten (except Pilot “A”) were from group 2.

In case of group scoring the new scoring method is much fairer because in both groups the "average pilot" will get the same number of points (around 1000) wathever the best time is. if some care has been taken to make both groups of egal value this result is very fair.


It is proposed to use the "average time" instead of the "best time"in the F3F scoring formula. This modification has two advantages :

  1.    global ranking is made consistent with man on man ranking
  2.    group scoring becomes perfectly fair

Don't be wrong ! This new method scoring will not affect the result of the pilot getting the thermal or flying very well, "killing" the group. The objective of this scoring method against the average time is to not impact the pilots compared to the other group where all pilots are flying around the same time.

Now that group scoring doesn't impact negatively the pilot scoring, why not consider group scoring to be used in every round for competition with more than xx pilots ?

We could imagine groups of pilots between 10 and 15 (or more) depending of the total number of pilot.

But to make the competition as fair as possible the composition of the group must be done carefully to avoid pilots to "meet" the same pilots several time. Such algorythm exists already in other categories like F3K or F3/5J, so could easily be adapted to F3F.

This approach would allow fair competition with large number of pilots, maximizing the number of round flown during the day as we can fly a group before the night, and resume the next day.

Of course all this must be studied carefully, with simulation, etc ...

But I really think that we should spend some time to evaluate the benefit of theses changes, and not stay on the current rules and complain.

So how to progress on all this topic ?

I was thinking that we could create a international working group with one representative of each (active in F3F) country, who could play the role of relay with the different national communities. This representative could be the official category representative of the country, or a delegate, an active and experienced F3F pilot. This working group could brainstorm, work on ideas, simulations and finally eventually propose some rule changes with a wide support, following the CIAM / FAI calendar. I know there is a wish of the FAI/CIAM to have such working group.

Ready to participate/contribute ? Stay tuned !

Thursday, October 25, 2018

Review: Judge F3B from Duffek model

Judge F3B from Duffek model

by Sylvain Coulomb

A new glider called Judge appears in May 2018. Look and design is close to most recent available toys (Pike 2, Pitbull 2). Little information available on design made by Jan Stonavsky and Duffek model:
  • Wingspan - 2980mm
  • Length - 1468mm
  • Wing area - 56,82 dm2
  • V-tail area (proj.) - 5,65 dm2
  • FAI area - 62,47 dm2
  • Weight - 1850 - 4685g
  • Wing loading - 30-75/dm2

After a first contact, I decided to make F3B version testing for next World Championship as an economic alternative to other very expensive gliders. I am helped by Julien Gourdet, our first French representative pilot for Jesenik 2019.
Data are available at http://www.duffek-model.cz/cz/index.php/kontakt-2
Duffek Model is close to Vaclav (Stinger, Sonic…) and they seems to share reasonable and fair commercial vision.
Filip Kalensky has done a great job to present F3F version, installation and setup at https://www.rcgroups.com/forums/showthread.php?3088222-Judge-f3f-f3b
Website says: This model is fabricated in diverse strength variants of the best composite materials. The model is an excellent competition machine for all types of weather conditions. Perfectly holds the selected flying line in a turbulent environment and, thanks to aerodynamic purity, has a high penetration rate in the wind. At high surface loads it retains good dexterity.
Our test is there to present F3B potential of the Judge and verify designer assertions, F3F information coming by Filip.
So I ordered the F3B Light version presented in this article. (And also a standard one not presented here). Both delivered with hook not supplied for F3F.

Parts weight :

  • Left wing : 600 g
  • Right wing : 602 g
  • Fuse : 206 g (with command)
  • conus :   34 g
  • Elevator L :   34 g
  • Elevator R:            32 g
  • Joiner : 125 g 
  • Accessories :   25 g
  • Supplied nose brass : 110 g

After installation, wiring and CG adjustment (102.8), empty flying weight is 2040g witch is very correct for F3B even if some models could be lighter. 
Model examination:
No particular remarks on manufacturing. Quality is equivalent to most high quality gliders (Baudis model, Samba…).
Some improvements have to be made and should be fixed shortly by Duffek models:
  • Servo caches are too small so I replaced them by transparent PVC  (I suppose an error easy to fix)
  • LDS system screw still delivered with MKS size and should be for KSTX10
  • Fuselage commands good for F3F replaced by me with lighter one to save back weight 
Actually the model is delivered without ballasts and wires, with wings and elevator bags. 
Prices are to be checked with manufacturer but are around 1500€ for the 3 versions.
I decided to mount available MKS servos but Judge is done for KSTX10. Both brands will fit in. LDS installation is easy but need attention before gluing servo supports.
Filip installation is on line so; I don’t develop except light changes.

I soldered LI-ION batteries with long wires to install them one by one with no change in existing holes to keep fuselage as is. No space problem to add servos, Zepsus, batteries, cables…
I hesitate to add ballast tube and forget it for this one. In distance, it could be interesting to quickly modify weight with no time to dismount wings.
So, in less than 8 hours, it was ready to fly … waiting for good weather!
Personal ballasts set:
I took an option with 4*40 g in the front 4*110g in the back in order to move CG backward if it fit after tests. Otherwise, I will reduce weight of back ones.  Front are 10*10, back are 20*12, Joiners are 8*8 … All this is adjustable depending of your habits and set up. For sure, it is possible to add more than 1800g ballast even if not so frequent for F3B.

Preliminary flight tests:
As a glider is long to set up, preliminary feeling will be confirmed in some flying sessions.
Two sessions were held on slope with poor conditions (no front wind) to verify CG and first command rates. Then we could test on field which is this version target.

Saturday October 20/ wind around 17km/h/sunny

Empty CG 102.9 2070g Distance light 103.2 /2500g Hook at 103 from leading edge.
First launch: not enough elevators (safety) ... so bad launch but Judge seems rigid and good zoom --> already average high compared to others
Second: nearly perfect, easy to drive and high altitude ... quite impressive because we have certainly better set up to test!
All day long: adjustments (differential flaps ...). Very good feeling and apparent stiffness
After adjustments: performance is there, quite easy to adjust everything to place the model where and how (attitude) you want. 
Butterfly is easy to manage with very good stability. Smooth landing with adjustable speed/distance to stop in target. 

Sunday October 21: Contest/wind around 13/15 km/h Conditions less good than Saturday on thermal standpoint.

We decided to have Julien flying the contest with Judge (and my TX) after problem on FS3 servo. He had launching difficulties all the day due to switches position on my TX ... so altitude and results could have been easily better with his own material.

Even though, he won all his durations, distances (3 To 5 laps more than others); and makes good speed (better and better time to adjust) including a 1000 in one round. 

Confirmation of Duffek model website:
  • Strongest parameter seems "facility" quite rare with an unknown new machine.
  • Second is clearly performance in distance and turning facility and precision (you really can choose your turn style depending on speed/conditions/ballast). Distance is really a pleasure and good cadence is easy to maintain. Julien liked it!  Setup to improve and maybe 102.8 better than 103.2 (little bit touchy - to be confirmed)
  • Speed to be confirmed but promising (Julien didn't ballast too much for first tests with a friend’s materiel)
Without the first 0 with FS3 servo trouble on duration, Julien would have been 2° at 5 point from the first. For a first test we couldn’t expect more!
Global balance is really positive.

Some points to check for potential improvement:
  •  Not really checked: Stiffness. Model seems quite stiff enough but has to be confirmed with more ballast. No bad feeling at this point because we made some "hard" zoom during set up and nothing bend ... To be confirmed in hard conditions.
  • Light F3B version is really much optimized and skin is really thin (60g carbon). This could be a concern close to the joiner because you need to be careful during wing mount to prevent fingers marks. High level pilots are used to and prefer to save weight. Normal pilots would probably prefer standard version for better model life. Weight increase is not really a problem with model duration capacities. Discussions are in progress with Duffek in order to add one more layer on the wings first 20 cm to definitively prevent the fingers marks risks.


Still confirmation to wait after more flight time but really a pleasant, easy (and performing) model compared to current models we have (FS3, Pike 2, Device) in the team. For sure, it will be long to confirm because high level performance is reached by best pilots after month of setup and flight hours but for normal good pilots like me, Judge is already a model better than my own flying skills limits.

Have fun and good flight, 


New version of the RC throwmeter App available

In this version, Yannick changed a bit the main screen, by limiting the display to one digit after the decimal point instead of two. This...