RetoF3X's blog - RC Groups
RetoF3X's blog View Details
Posted by RetoF3X | May 08, 2016 @ 10:48 PM | 4,024 Views

Flitzebogen F3K launch (0 min 28 sec)

Stream NXT quick turnaround:

Quick turnaround with Stream NXT F3K (0 min 26 sec)
...Continue Reading
Posted by RetoF3X | Apr 09, 2016 @ 10:57 AM | 4,027 Views
Hi Guys

I performed an experiment to compare the moment of inertia for different DLG setups.

I applied it to see if a different arrangement of the radio gear has a measurable effect.

I tried to compare the overall moment of inertia of a conventional Flitzebogen to a new setup where everything is moved closely to the CG. I have used an unbuilt fuselage and I added a finished wing and tails to it.

Then I stuffed the radiogear either in the front of the nose or at a location closer to the CG and added 100gr of Tungsten to balance it. In the normal setup, that amount of Tungsten went into the CG as we would do with conventional ballast.

Then I hanged the model on two strings from the ceiling, exactly balancing it on the model's CG.

The system is now a harmonic oscillator around the yaw axis with a weak torsional spring constant. Its resonance frequency is the square root of the spring constant, K_T, divided by the moment of inertia, I_Flitz.

Thus an oscillation period is T= sqrt(I_Flitz/K_T)

Now I measured the oscillation period over two oscillations and ensemble averaged over multiple realizations of the experiment.

I found:



T_FlitzOld is the oscillation period of the conventional setup

It is important that the mass of the system is exactly the same (else the spring constant is changed) and that the model is hanged up exactly the same in each experiment.

If we now divide T_...Continue Reading
Posted by RetoF3X | Mar 08, 2016 @ 11:29 AM | 4,477 Views
I have had a decent start into the 2016 contest season and I am happy that I can do well in F3K, F3B and F3J.

I am particularly happy that I have won my first F3b contest, it took me a while.

Posted by RetoF3X | Feb 25, 2015 @ 09:06 AM | 6,598 Views
I have developed last season a method to determine the flight time nomination for the last Poker flight. The idea was to not use the timer at all, so that he/she can mainly focus on reading air and counting flight time. The method has worked to a 100% for me and since those who have timed for me know of it, I thought I can as well share it publicly. Please cite me though if you use and share it.

It works as follows:

1) Program a timer on your radio that counts down 10 minutes.

2) Start that clock 5 seconds before the start of the window.

3) When it comes to your last flight, the moment you have the plane ready to throw, glance at the clock on the radio and simply read (yell) whatever is displayed on it and throw the plane.

As the clock is 5s ahead of the working time, you will nominate a call that can be achieved. You do not need to subtract anything. Importantly, your helper does not need to count down the remaining working time either, which proved to be a big boon.

If you fumble the catch, just look at the clock once you are ready to throw.

For a tighter nomination, the 10 min clock could also be started 3 or 2s before the start of the window, but I prefer 5s safety buffer (i.e. if the official clock is lagging, etc).

As stated above, it has worked for me to 100% reliability past season and has taken a lot of load from my timers.

This method has evolved out of my previous method that estimated the last flight time when there was 1 minute left in the second-last flight. The old method however needed the helper to read out a working time during the second last flight, which was error prone and some timers got confused. The new method has proved to be vastly more robust and easier to apply in a contest situation. Further the old method required a perfect turnaround to work, whereas the new one is fully adaptive to mishaps.
Posted by RetoF3X | Nov 02, 2014 @ 06:59 PM | 7,099 Views
A fun contest with six rounds in thermally active weather. I had a great time and a couple of good speed (14.4s) and distance rounds (30 laps).

I had the highest raw score (so without drops I would have won), but after the throwouts I ended up on place 6, it was a tight contest. But since I was not eligible for the team, I did not care too much about the final ranking, but more that I had consistent flights and a good time.

Here is a video of one of my speed flights. The turns where right on the buzzer at Base B, the first turn really looks/sounds like barely a feet over. Nice calling by Mike Lachowski.

F3B TS Friday Speed (1 min 57 sec)

Results are here:
Posted by RetoF3X | Nov 02, 2014 @ 06:22 PM | 6,725 Views

Flitzebogen launch (0 min 12 sec)


Reto 1 (0 min 13 sec)
...Continue Reading
Posted by RetoF3X | Sep 05, 2014 @ 09:08 AM | 10,261 Views
An important topic, as I see quite regularly suboptimal linkages.

I like to make all my linkages with maximum mechanical advantage, that is, using ALL available servo throw to achieve the desired surface deflections.

I got asked how to do this on a flaperon that has asymmetric deflections (i.e. more down than up).

Here is my procedure how to design a flaperon linkage that uses all servo throw:

1) On your transmitter, make sure that you unlock all available servo throw. On Futaba, that means 140% dual rate, max rate on diff and max endpoints and travel. The aileron servo should now move from around plus to minus 50 degrees. See Figure 1.

2) Mount the servo horn at neutral transmitter trim such that it points vertically down

3) Using a balsa wedge, fix the aileron in the maximum upward deflection position. Since this will be max up, be generous (i.e. if you want 15mm up, fix it at 18mm up). See Figure 2.

4) Bring the servo to the end point corresponding maximum aileron up. The arm should now point 50 degree backwards in a bottom drive system, as shown in Figure 3. For a top drive linkage, the arm has to point forward, see Figure 6.

5) Hook up the linkage to wing and servo and glue in the L wires into the carbon rod, while aileron is fixed and servo is in full deflection for aileron up.

7) Once it is well cured, move the servo on the transmitter to neutral. You will notice that the flaps are already partially deflected downwards (see Figure 4). This is as it should be,...Continue Reading
Posted by RetoF3X | May 25, 2014 @ 06:47 PM | 8,682 Views
I got some more airtime on the Tweagle

The short inertia concept seems to work, it really circles tight and effortlessly. You can really bang that plane around in a circle and keep it in a narrow thermal. Does not look pretty by times, but if that is what keeps you in the air, why not.
On the flip side it requires more active flying, a price to the augmented agility.

I compared the plane against the Snipe, Flitzebogen, Helios and a Blaster. I was outlaunching my buddies with the other planes and in weak thermals I felt quite comfortable. I could circle much tighter and it climbs very well.

To me, the Snipe feels a bit faster, but the penetration against wind of the Tweagle is not bad at all. It can slow down more easily and it is really easy to circle.

Here is a timelapse series of some quick turnarounds:
Quick turnarounds with the Tweagle DLG (1 min 33 sec)

Posted by RetoF3X | Apr 27, 2014 @ 06:12 PM | 8,928 Views
I got a Tweagle to test. I have always wanted to try a model from Alex, as they are very innovative and sometimes exploratory. The Tweagle is no different, with a high aspect ratio wing, a stubby, short fuselage, wing on a pylon, and a high aspect ratio vertical.

The parts are all very well made and the wings are quite stiff and light. The wingtip is a bit stiffer than on a Snipe. According to Alex, the tip airfoil is a bit thicker, and this apparently afforded for some more strength. The leading and trailing edge were excellent on my plane, a detail that I appreciate.

The fuselage is plenty stiff, but the big boom has reduced hoop strength. So one should better not squeeze it. But for the main loads it seems quite strong. The canopy fits quite perfectly and the seam is also very minimal.

Build notes:

I have added additional uni tow on the vertical tail, just to be save. I tried to get maximum mechanical advantage by making the horns 1.5 to 2 times larger on the surfaces than on the servos. Due to the fact that the torque-tubes on the flaperons are almost 20mm tall, the servo arms have to become proportionally large too. They still fit nicely in the fuselage. With my fuselage layout and the use of clevis, the flaperon pushrods can be removed, which simplyfies the assembly on the field.

Posted by RetoF3X | Feb 01, 2014 @ 05:10 PM | 8,130 Views
Lots of space, nice temperatures all year long and lots of wind.... Bingo, a great place to fly F3B!

We have now two hotspots in Texas, Houston and Dallas. In Houston we have about 4 F3B winches for efficient speed practice, here in Dallas only two.

Fastest speed time in Dallas stands at 13.75s, in Houston 14.10s, so we also have fast air down here.

Please join the fun if you are close to either area!
Posted by RetoF3X | Dec 23, 2013 @ 08:15 AM | 8,574 Views
Would be nice to break 80m. To do so, I will probably need the help of wind and good air, but still would be fun.

Or at least a goal to strive for.

Obviously it needs a good launching plane. I am going to try this with a Super Fr3ak, Snipe and Fr3ak NXT.

Another part is how to accurately measure launch height. I am looking for a building of 200-300ft altitude (best with balconies for multiple measurement points) to calibrate the logger for a given temp and pressure. How to measure the precise altitude of the building? Hmm, throwing down a rope or a laser range meter (which is calibrated in the horizontal). This is a bit the fun part that is holding me back.

Below a log with a Snipe in 12mph wind and 40gr ballast.
Posted by RetoF3X | May 01, 2013 @ 10:37 PM | 10,227 Views
The new season started with two great contests for me, the Gator F3B world cup in Cocoa, FL and the IHLGF.

The gator saw maybe the most amazing conditions for speed, two times a new world record (11.9s) and I got also a personal best of 13.15s. It was lots of fun with the US team, Armin and Peter from germany and pilots from Chile.

IHLGF was in beautiful weather, not too windy, but tricky thermals. I was early on off for a good start and did not commit any severe misstakes. By Saturday night I was even on 1st place on the leader board. I threw away some points in the second last flight (last 2 flights) and went into the fly off on place 3. The Fly off was with good thermals but they moved quickly downwind and if you missed the ride, it got ugly. I managed not to land out and in the 5x AULD I dropped only one second. I got the second place and I am a bit bummed that I lost small amounts of points over the 16 prelim rounds - a bit more aggressively and I could have been first. However I chose to fly conservatively and maybe more aggressivness could have ended in a land out. Thus I am happy.

I still have work to do, a short visit to Switzerland gave the possibility to go to the Vercelli Eurotour and I lost quite some points in marginal air. We only flew three rounds due to bad weather and I got 19th place. Three rounds is not that representative, but the bad result still keeps me motivated to practice hard.

Posted by RetoF3X | Nov 04, 2012 @ 06:12 PM | 10,670 Views
How time flies, it was again time for the US TS. Due to work commitments, preparation was the bare minimum, just one windy speed session with Mike. In addition I had to arrive in the morning of the contest ( Thanks for the ride Warren!).
Given the circumstances the first day went well for me, three distance wins, one 27/28 result and one medium one. Mike Lachowski did some great calling.
Sunday was quite different. While my duration flights were ok, I could not score in distance. I always went first and flew my own stuff, which three times in a row did not work out -ouch.
Speed was okay, I flew within the top 3-5 with the air I got. I pushed it hard on Base B, but no cut. However I got a safety penalty in the last run.
Monday was a good day for me, made all my duration flights full and had two good speed flights. One was second or third fastest, I think.

Getting home was a nightmare thanks to Hurricane Sandy. It sucks when rental cars are faster than planes.
Posted by RetoF3X | Oct 19, 2012 @ 08:20 PM | 10,811 Views
Delaware never disappoints Mike and me: great field, helpful crew and somehow always fast air. we were there in spring practicing for the Gator and now once in Fall for the TS and each time there was at least one 13.xs run and a couple of 14s. It surely helps that it is blowing up there.

Pictures shamelessly stolen from Gerald: Reading
Posted by RetoF3X | Jul 07, 2012 @ 10:17 AM | 11,200 Views
Still some months till the teamselections and half a year till the next Gator.

F3B Speed Run Gator (0 min 47 sec)

Posted by RetoF3X | Jul 07, 2012 @ 09:52 AM | 10,997 Views
Due to work, I coud not go to many contest. Thus I picked some of the bigger shows, Gator F3B, the IHLGF and the Bruce and I am glad I went there.

The Gator F3B was great, we flew up to 9 rounds and I was happy with my speed (I averaged around 15.xs) and distance performance. I finished third, but one week later, I was downgraded to 5th place due to a rule change in 2012.

IHLGF was very well attended, with Joe Wurts, Mike Stern, George Morris and myself 4 guys from the worlds fly off were present. I did not do well in turnaround tasks, because I arrived late Friday night and was exhausted. I was very happy with my Fly Off performance where I finished third. Within 4 hours, I was then again downgraded to 5th place due to scoring errors.

The Bruce was crazy hot and a fun contest. I finished again 5th, but this time straight and without having to return a trophy. Dave and I flew solid in the prelim rounds without major blunder and could win the team trophy (the tin cock). This was our goal and it felt good to achieve it.

Images of the Gator shamlessly copied from Gordon: Reading
Posted by RetoF3X | Oct 04, 2011 @ 09:54 AM | 13,652 Views
found this on the web, one of my throws at the launch contest at the worlds.

Launch heights from Swedish F3K 2011 (0 min 43 sec)

I actually did not know that I was jumping during the throw, I thought I keep my feet at the ground. So guys, get videos of your throws.

Note the windsock which explains launch heights of 70m++.
Posted by RetoF3X | Aug 24, 2011 @ 09:51 AM | 14,314 Views
I focused this year on flying F3K, as the world championships were coming up. Qualifying for the worlds was interesting, as I had to fly back to Switzerland to participate in the qualification process. Luckily that contest went well and did take place (weather).

I did practice sessions 3 times a week and worked on launch height and turnarounds. My contest results got better quite immediately. A second place at a contest of the german tour and a fifth place at the IHLGF were promising.

The worlds itself was an interesting experience. Each round felt very serious. I managed to stay focused through the prelims and ended on fifth place .

The fly off was a rough. It went well until round 3 where I missed the field by 10m in AULD. Somehow I lost it then from there. I tried hard, but I always reacted instead of doing my own thing.

In short, it is a good experience in aeromodelling to focus on one thing and see some improvements. My launch height PB got boosted from 50m to 70m and also my turnarounds got significantly shorter in this process....Continue Reading
Posted by RetoF3X | Dec 01, 2010 @ 07:28 PM | 15,333 Views
The trip to the TS in California was quite expensivve, but worth every penny. As I was not eligible for the team, my goal was to set some new PB. Did not fully happen, but on the first day I got a 13.6s in the first round and a 30 laps in the evening. So I was not disappointed by the thermal condition in Cal Valley.

It was also a treat to fly against Daryl Perkins, the most successful rc soaring pilot of all times. He flew some smoking fast speed runs and set the fastest time with a 13.04s run.

Mike brought a Fosa back from California and we tried to compare it against the Freestyler. We got maybe the last nice weekend this year on the east coast and had a nice practice session....Continue Reading