F3F clinic/intro/Funrace @ BR

[Pang]

Wind blowing good past few days, if you want to know more about F3F and try out, do some practice, we will hold a fun race this Sat 25 Jan at BR , pending weather conditions. Will update here on Friday if race is still on.

I will bring timer, 9am briefing, 9.30am starts, we will try to run as many rds as we can before the crowd comes, any slope models is welcomed to join in the fun.

BR F3F record is currently 56.32s held by Francis , lets see if who can beat it this sat.

[JYZoom]

Wind blowing good past few days, if you want to know more about F3F and try out, do some practice, we will hold a fun race this Sat 25 Jan at BR , pending weather conditions. Will update here on Friday if race is still on.

I will bring timer, 9am briefing, 9.30am starts, we will try to run as many rds as we can before the crowd comes, any slope models is welcomed to join in the fun.

BR F3F record is currently 56.32s held by Francis , lets see if who can beat it this sat.

Cool... i got to try to beat my record of completing a round.
you should bring some of your RTF - ready for sales on site for immediate sales.....once they are get the itch...who know they may just buy it.

Jonathan

[Pang]

Weather looking good, race is on.

Tmr 9.00 @br.

[JYZoom]

You will be lucky , Pang, post number 288.

[Pang]

8 pilots turned up, wind was marginal at times but was great fun. Hope the new guys get a taste of F3F. Congrads to Vincent for winner of today's race and best speed 59.05. Will run another race after CNY.

[Pang]

Next F3F @ BR 8 Feb Sat, pending wind conditions. Will confirm next week.

Happy holidays, best wind normally during cny period.

[Pang]

F3F tips by Fritz Kristofferson part 1

Dig up an old article, helpful for those starting f3f. We met Fritz at BR in 2009, he shared with us some tips.

F3F tips by Fritz Kristofferson

Fritz with his inverted V-tail design


We had the pleasure of meeting Fritz Kristofferson at our slope last month. Fritz is from Norway and has over 30 years of aeromodelling experiences. He was many times Norwegian F3F Champion and flies his own home blew unique inverted V-tail design. He is also active in the F3B and F3C heli scene.

He is kind enough to share with us some of his racing experiences.

Rules:
You can find the basic information and F3F rules here:

https://www.sloperacing.com

(See the videoclip under “F3F” of model “Miraj” in strong lift conditions).

However, the contest director might slightly adjust rules according to wind conditions and slope conditions.

Preparation:
Try to have a good look at each base (A and B) before the contest starts in order to understand the turning-judges signal system, and the centre loudspeaker position relative to pilots standing position during flight. This exercise also gives you a better familiarisation with the slope itself also.

The slope:
Good slopes are usually clean from threes and obstacles and have a sharp top edge. Such slopes has their best lift zone close to its top edge. This strongest lift zone is the basic “centreline” following the edge to the left and right where you can convert strong lift energy into speed. However, usually, for the turns, most people are pulling slightly up to store some of the models energy, and by doing so, have resources to spare if they should do a lousy turn (eating too much speed energy). Then, higher speed is re-gained by diving towards and aiming at the “centreline” again after each turn.

The start:
After the launch, the rules gives you a 30 seconds available flight time before you need to enter the first lap of total 10 integrated laps (enter the A-base with flight heading towards B-base). During those 30 seconds you want your model to collect as much energy as possible before entering A-base. It can be done by gaining height, and then dive, entering the course at elevated speed in approx level flight before the 30 seconds has run out. Obviously, a strongest possible hand launch is advantageous. (You are allowed a helper for the launch).

If you have no helper and need to launch yourself, and if the slope is very wide, it can be advantageous to just travel past A-base and continue following the slope Centreline at almost “Eye-level” for approx 15 seconds, then turn back and enter the Course at A-base before 30 seconds. In particular this technique might be helpful when the slope lift is clean ( not interrupted by thermal activities), the slope is wide, and you are using a lot of ballast.

The 10 laps:
There are 9 turns as follows:
A-base has Enter and Exit + 4 turns in total.
B-base has 5 turns in total.
For a beginner, the fastest time is usually obtained if you can fly “clean and smooth” without too much un-necessary deflection inputs and manouvering. Maybe you want to fly slightly wider than “tangential” and in such way not loose the turning- signal given by the “turning judges” at A base and B-base. If you fly too short and misses the signal, you need to go back and catch the signal before you can continue, and this process tends to stress the pilot alot resulting in even more bad manouvering.

Plane Setup

CG:
Forward CG makes the model sleepy, and calls for larger control surface movements adding up to more drag and slow speed. Rear CG makes the model more lively, however, too much might cause accumulated troubles of piloting.

Linkage and servos:
Precise servos and tight (no slop) linkage is always helpful.

Ballast:
Use as much ballast as you are confident with according to lift conditions. Remember, if lift conditions are extremely strong, adding ballast helps you keeping the model stable and predictable. Too little ballast slows down the model alot, and the model gets much more sensitive to gust and turbulence slowing it down further.

Flap deflection:
Your added ballast should match neutral flap setting at given lift conditions, with the following addendums:
You might like to have 2 (or 3) additional flap settings:
If after launch or during the speed course you discover the amount of ballast was too much, then flip the flap-switch to approx 2mm positive flap + positive ailerons (Flush with flap), and flip back to neutral if conditions improves or your speed gets better.

Positive flap is also your flap position during launch, helping you getting all your ballast airborne. (Some pilots might like a third position at launch (only during launch + the immediately following 2 to 5 seconds after launch) with even more positive flap according to your specific model).

Then if ballast was too little, or if your speed increases very good, you should flip your flap switch to slightly negative flap approx 1 to 2 mm (or according to models airfoil) and also negative ailerons (flush with flaps).

If your transmitter allows for it, you like to put in approx 0.5 seconds “delay” between flap positions, avoiding too quickly change of airfoil shape and airflow interruption.

Elevator:
Do not set up your model with too much elevator travel. Too hard “Up” only stops / slows the model down during the 9 turns.
Mix in “Kick-flap” with elevator, maybe approx 4mm positive (Down) for flap at full elevator “pull” and addmix the ailerons down for a flush trailing edge. It is very much needed to remember to include the Ailerons, and in such way securing a very much increased wingtip lift during the turn, making the model accelerate better. (Ignoring adequate down-aileron to, I would say, at least follow the trailing edge of kickflap is a classic reason for slow and poor performance during the 9 turns of the tight F3F course).

Rudder:
Even if you are a confident pilot using separate individual stick-controls for aileron and rudder, you want to consider as follows:
When travelling in neutral or positive flap position, use rudder admix to the ailerons, maybe 30 to 50 %.
When travelling in negative flap position (”Speed flap”), use rudder admix to the ailerons, maybe 5 to 15 %.
For both, in the case your coordination of rudder inputs are lousy, use more rudder to aileron admix.

Ailerons:
Do not set up your model with too much aileron travel. Too quick/hard banking only stops / slows the model down during the 9 turns.
Most models responds fairly good to the following set up:
Step1: Flap to follow the ailerons deflections 50% for “Up” position.
Step2: Aileron down deflection approx 50% compared to Aileron up deflection (This gives you balanced drag on both wings, because aileron “Up” is less draggy than aileron “Down”)
Step3: Flap down deflection to follow trailing edge of aileron down deflection (This gives a flush trailing edge for the down deflected wing half, and a split trailing edge for the up deflected wing half, and this split “up” trailing edge causes a balanced drag and helps the model to yaw correctly during the turn.

Finally:
Ask around at the slope and try to copy the setup and flight pattern giving the fastest times.

And better, show up at the slope a couple of days prior to the contest day and have experienced guidance from the other early pilots for flight and setup, and practice.

The above is only a guide. Different models will differ in optimum setup. You will learn as you go.

With my best regards
Fritz

[Pang]

F3F tips part II - Ballast

F3F tips part II - Ballast

Amount of ballast depends on strength of the lift.
Your local slope at the reservoir might unfortunately not show the clear advantage of ballast due to its lack of strong lift ( Your slope has no compression Zone, nor any clean top ridge).

As a rough indication, one might assume that during given site and conditions, when the best pilots obtains times in the region of 60 seconds for the F3F task, lift conditions are so bad that they have no ballast.

For better times, say around 50 seconds, maybe 1/4 to half ballast.
For times within 40 to 50 seconds, maybe 3/4 to 1/2 ballast.
For times sub 40 maybe 3/4 to full.

Above of course assumes we are speaking of clean steady slope lift, and not thermal “on / off” conditions. In case of thermal activities, the best time is more related to pure luck in catching the thermal boost within your working time, and not so much to the ballast.

For deep understanding of ballast, try this relatively straightforward site on aerodynamics:

http://www.mh-aerotools.de/airfoils

Look under the left side menu “How do I…” and in particular the sub menu, please click on the text “…read the Polar diagram”

You might want to play around inside those formulas in order to find your specific models lift coefficient. Try to input your own models vitals: Wing area, Weight, and assume various speeds to find the ballpark of actual Reynolds numbers also.

If you find the polar curve of the Miraj airfoil (MG-06), you can also find your airfoils drag coefficient… and then have some idea of expected sink rate versus flight speed. (Actually you need to know the total lift and drag coefficient of wing including rest of airplane to do exact calculations, however, looking at the airfoils polar diagram will point you in a healty direction.)

You will soon discover that a heavy model has superior glide angle (Will not need to “dive” in order to get speed), however, the weight limitations being the 9 F3F turns, calling for higher lift coefficients as the airplane might see as much as 10 to 20 G’s during the turn.

That is why many of the best pilots pulls up softly prior to the turn, then partly makes 1/2 roll, then inputs hard “pull on the elevator” through the approx 120 degrees of the “Split-S “and then progressively eases the elevator pull of the remaining 60 degrees of the “Split-S” because of the following:
During first part of the Split-S, the Earths-gravity is helping you through the Split-S.
However, during the last part of the Split-S, Earths gravity, and the weight of the plane both adds to the wings G-forces and you are at the very highest wing loading (highest lift coefficient) during this last part of the turn.

Unfortunately, Your Singapore reservoir slope might have too weak conditions for above mentioned techniques.

However, at such slope it might be helpful to not fly in a straight line between A and B base, but try and pull up slightly prior to the turn and doing not a 180degre roll and 180 degree pull type Split-S, but maybe a roll of only 100 to 130 degrees and then a balanced 180degree pull as described above, slowly recovering the roll to neutral AFTER the 180degree pull. This makes the model to continuously return to the centre of the slope.

Finding the best pilots at such a slope, they might follow a wide U-shape track between A-and B-Base, with the extremes of the U beeing the turning points at A and B base, and in addition they might “tilt” the U-shape slightly forward, with turns a bit out and high, and still keeping the bottom of the U close to Slope / Pilots position…

This shape of the flight course will correspond to moving towards the ideal lift coefficient of the airfoil versus drag, securing the best glide-ratio at highest evaluated possible ballast corresponding to wind speed and lift conditions…

In other words, the fastest F3F times is usually achieved by following a ballast + flight pattern that gives the best glide-ratio at given airspeed…

Finally, watching the fastest flight pattern at given slope will hopefully reflect optimum course to give you an idea…

In addition, for (seaside) slopes with a strong compression sone, keeping the model inside the compression sone might bee more important than the quality of the turn itself…

And for slopes with strong thermal activity, hitting the themal centercore gives a large high-speed bonus not necessearly related to piloting skill… just pure luck…

And again, alot is to be won in the 30 seconds working time before the model enters the first lap. During those 30 seconds you want to accomulate as much lift as possible in order to put energy inside your model. For an inland slope (usually not seaside) some lucky pilots might hit a thermal during those 30 seconds and if they have gambeled with adding lots of ballast to the model too, a heavy model at 100 m gained starting-height of course calls for much less piloting skills during the following 10 laps in order to make a fast time.

At some contests, the flight or Pilot might be disqualified if the pilot /plane airpeed is gained by diving towards the bottom of the slope during the 10 laps. It is more and more ususal that the 10th lap should be finished within reasonable “eye-level hight” in order to rule out speed gain due to constant dive through the task.

Luckily, for sharp seaside-slopes with a total height of only 10 to 15 metres, such slopes usually give a strong compression zone due to the strong sea-wind, and leaves no advantage for any kind of “diving technique” … For this reason, experienced pilots many times prefer the contest to be arranged at a steady blowing seaside slope, because it is more protected from possibilities of “bending” the rules, and has much less or almost no thermal activities.

For a 10 to 15 metres high seaside slope, one might use 1/4 ballast at 4m/s vindspeed. And 1/2 ballast from 5 to 6 m/s, And 3/4 ballast at 7 to 8 m/s . And then full ballast above this windspeed. And compensate with negative flap setting for windspeeds up to 15m/s. Above 15 m/s you might want to change to your faster airfoil sectioned “B” model…and stick with this one up to where the max windstrength rule ends somehat around 28 ? m/s windspeed… or according to contest directors decision. At windspeeds above 20m/s, and for a low seaside slope, most models anyway will just tend to slow down again, calling for a faster airfoil section… / more slim construction…

Best regards
FK

[tansc]

Thanks for sharing pang!

[Pang]

Tmr forecast light conditions. 9am prata breakfast , 9.30 briefing, 10 we start if there is enough wind.

[Pang]

Last race no wind. Windguru forecast good this sat, will confirm on friday if race is on this sat.

[Pang]

Windguru looking good for this sat. So race is on. 9am prata, 9.30 briefing , 10am start.

[Pang]

2nd F3F fun race.

11 pilots turned up, we flew 8 rounds, wind was blasting 5-8m/s although abit crossed. We saw some fantastic runs and good saves. Great Fun.

Final ranking. 11th place shaorong, 10th boonyang, 9th weiyao, 8th jy, 7th faheem, 6th joey, 5th vincent, 4th KP, 3rd sherwin, 2nd Pang, 1st Francis

Amazing best speed and new BR record by Vincent 40.40s.









More pro shots by YZ https://www.facebook.com/media/set/?...7635209&type=1

We have another run 2 weeks later pending wind condtions.

[sherchoo]

Special congrats to Vincent on his blistering record breaking run of 40.4s. I doubt that anyone can beat his record anytime soon. Such precision is just too rare.

P/S: I'll be happy to be wrong on this though.

[Pang]

This Sat f3f on. We start earlier. 9am briefing, 9.30 start. Bring your own breakfast n lunch.