Three Is the Magic Number
Why you need to turn off your television set and give GPS Triangle Racing a go.
My glider is launched and it is climbing at 16m/s and passing 150m. All of a sudden the plane has started to climb faster and is climbing at 20m/s. The thermal is marked by a circling bird and the lift is moving from left to right in relation to where I’m facing. At 420m it’s motor off and a left turn, that takes the glider out of the lift — the audio vario confirms this. Continuing the left turn to chase the thermal I check the altitude readout on the phone mounted on my transmitter, 408m altitude, and the GPS speed on the clock is 90km/h. Squeeze down elevator and the speed hits 105km/h and the altitude shows as 390m. In my headphones I hear “task started”.
Almost immediately the vario tone has gone up and I’ve got the glider into a thermal turn. So, do I stick with this thermal and take as much height as I can? Do I just take a couple of turns as it drifts towards the first turn point and get going on the task? A quick glance back to the third turn point confirms that I had seen a bird circling at about 100m height some 400m to my left. Okay, that makes the decision, the third turn in this thermal will take the glider to the first turn point and it looks like there will be more lift to hook into. As soon as the turn complete notification plays in the headset the glider is on course to the turn point directly in front of us.
It looks like the second pilot to enter the course is taking another turn or two to gain height. The third pilot has not taken any turns but has flown to turn one with thermal flap. As a result, even though they started after me their glider is now about the same distance around the first lap as mine but a bit lower, maybe 440m to my 480m. Both gliders get to the second turn point at about the same time. As we turn them towards the third turn point the air seems neutral but our gliders are facing more into wind. Hmmm. Mine is losing ground and I select my first speed flap setting. The two gliders are at the same sort of pace now but it looks like I am flying with less ballast. How is that going to play out? Both gliders round turn three, mine slightly behind but still higher. About 40m into the leg the vario gets all excited and we have both started circling. It’s breezy up there and we both keep our gliders circling across the start line, it’s strong lift.
“Completed one lap, twenty six minutes remaining, 530m” in the headset. Oh, that’s gone cold. The sink has been strong today, I’m taking as much as possible out of this climb. Not the same decision as the other pilot in the thermal has made though. Have they done the right thing, will they fly out the thirty minutes, have they seen another lift source that I haven’t? Here comes the third glider, much lower but they have made the thermal having flown from the third turn in the sink we can now feel on the ground.
There are another twenty five minutes to sustain the glider in flight and complete as many triangles as possible. Who has made the best decisions? Who will fly the full task? Who will get the most laps? If there is a tie for laps, who is going to have the best average speed? What is going on?
We are GPS Triangle Racing, that’s what.
So, for anyone who doesn’t know, here is a quick run down of GPS Triangle Racing and the classes. There is plenty of stuff covering the history elsewhere on the web so I’ll skip that in this article.
In essence there are three variants/classes. All use a triangular course with three GPS defined turn points. The diagram of the course (see below) shows you how the task is defined and the colour code shows you the different course parameters for each class. The 1/3rd-Scale/SLS class aircraft are scale gliders that fly on the biggest course. Sport class has a span limit of 5m and a max weight of 7kg (with wing loading limited to 75g/dm²). Light class gliders are limited to 4m span and a max loading of 35g/dm². You will need to read the rules for each class before committing because there are more details than this article can present and the 1/3rd-Scale/SLS class needs formulae to calculate allowable weights and loading.
The tasks have limits on flight time, entry height and speed (see diagram for the details). The laps are always flown in an anti-clockwise direction. Flying sites are flat fields and there should not be any slope lift. With the exception of the 1/3rd-Scale class planes every other class uses electric power to get the planes to the start height. For 1/3rd-Scale class you’ll need a tame tug pilot and a suitable tow plane. The landing strip needs to be a minimum 80m x 25m for every class other than Light class for which there is no landing task. There is a diagram that shows the key elements for all classes below:
Okay, let’s have a quick look at the tech. There are several systems available but in essence you need a glider pack that has a GPS sensor, a variometer and a method of sending the data back to a ground station.
The ground station needs to translate the data for the pilot and present some key items. As a minimum you need to know where to steer the glider to complete the course. You need altitude and speed data. If you have the vario you also get to know when you are in good, bad and ordinary air. The kit I’m using does all of this and more as well as displaying the data via an Android application. In addition to the audio vario, the turn points are announced into the pilot headset. The capabilities are immense and again need a subsequent article. Importantly the tech also records the key data for scoring the tasks. Once the data is recorded it can also be uploaded to the supporting league website which also supports competitions.
I want to talk about gliders next. As I don’t currently fly 1/3rd-Scale/SLS I’ll talk about Sport and Light class planes. Inevitably this will have a UK-biased view, and being a tiny island in the middle of lots of wet stuff, this means we’ve some slightly less favourable flying conditions that limit some planes’ potential. It is well worth looking at the GPS Triangle League (see Resources, below) to see what people are posting scores with in both competition and when submitting mega league scores, but the ‘best’ scoring plane isn’t necessarily the best plane for you. We have short lift cycles here in the UK and it is rare for lift to be on the course for more than 20 minutes and with anything more than 2m/s climb. If you fly where the lift cycle is longer, slower moving and more powerful then you can pick faster more aggressive planes.
Taking Sport class as a for instance: In the UK the Valenta Chilli (especially in ‘GPS Special’ form) is a highly competitive aircraft and it has been on the top spot in European international competitions as recently as 2018. It is a solid plane and will give you sound scores in the UK. In comparison the Baudis DNA Racer doesn’t work well in our relatively poor lift conditions and sticky air. However, in Berlin where the weather is different the better plane would be the DNA Racer. That said the reality of the Sport class is that anything over the four metre span criteria that can thermal, go in a straight line at 60km/h without losing more than 130–140m of height for 1700m of distance (so a bit better than 12.5:1 glide angle) is a good starting point. There’s a list at the end of the article of the planes we are flying here in the UK.
Light class is another case where the ‘best’ plane might not suit your location. Currently the Samba Prestige 2PK is the probably the leading choice for light class, along with any of the latest low camber thin airfoiled stuff from Vinco, Nan, Infinity and the like. However here in the UK where 12 laps is the best score we are seeing things like a Shinto J and an old Nan Shadow being flown to good scores.
In all cases what you need to do is set your glider up really well. Get it just so in thermal setting to extract the best from the lift with the lowest level of pilot input. In a straight line make sure the glider actually flies in a straight line and doesn’t feel like it is a ball bearing on a tray to control. Do a proper glide test: you want maximum efficiency from your plane, but you do not want the thing on the banzai end of super twitchy. The set up of gliders for GPS is a massive topic and that exceeds the focus of this article.
So, after all that vagueness and evasion, the things about selecting a plane to take from this article are that you need to pick:
- A glider that flies well for you in your normal soaring environment
- It needs a decent glide angle
- It needs to allow you to achieve the task duration in your local conditions
- It should be capable of flying efficiently without too much pilot interference
- You need to invest in the time required to set it up really well
Hopefully we now have enough information for a recap: for the purpose of this discussion we are flying electric powered gliders from a flat field, around a defined triangular course as many times as possible in a defined time. We are using some clever tech to tell us where to fly our glider and how to maximise the flight. In addition that tech can calculate the ‘raw score’ of each flight and in a competition upload it to the scoring website. Obviously this data can also be used by pilots to improve their results in the future, understand the flight, or provide memories of fantastic conditions and epic achievements.
What, then, makes this so engaging? Well, for a start flights are a good duration, and the ratio of flying per £/€/$ spent on toys is therefore very favourable. The flying task and decision making are properly challenging. You get to set your gliders up to fly really well, which usually means you spend lots of time flying.
Flying to a specific purpose or task really sharpens your skills, this task will really make you a better pilot. Your perception, decision making and capability to adapt to conditions will be improved; and your accuracy as a pilot will be better. As a soaring pilot you will find your understanding and use of lift will be improved, which will cross over into your other flying. One of the things that has been most enjoyable is when we get a one-on-one competition going and have eight to ten planes in the air at once. It is proper racing.
Useful links are presented with this article to lead you deep into the world of GPS Racing.
So come on in and join the fun.
About the Author
I’ve been playing with radio controlled gliders for 40 years, starting off with a Neville Mattingly Phoenix 100 and a Chris Foss Middle Phase. Along the way I’ve flown many soarers and been an active soaring flyer, competing in F3F; F3B; Open Class (F3J); Aerobatics; 60in pylon racing; open pylon racing; a few cross country events; and local club events. All great fun and they all demand different skills from pilots.
My personal view is that F3B is probably the most skilful event to fly well: because it demands a well rounded pilot; capable of accurate flying; the mastery of several tasks; a good understanding of the glider to extract good performance; good understanding of the air mass; and good decision making in the tasks. Better still two of the three tasks are flown against several pilots. Over the course of a day there is also a reasonable amount of flying to be had.
Much as I enjoyed many years of F3F the biggest negatives are the lottery of conditions (especially in large rounds) that can hugely affect the results. Also, perversely, the better you get the less time you spend flying.
In the last two decades I have mainly flown for fun and have usually found myself slope soaring. I am lucky to have slopes between 20 minutes to an hour from my house. With limited time I have still been grabbing the occasional three-to-four hours and managed at least one to two hours soaring in those sessions.
Life has moved on and my interest in competition has resurfaced. I was interested in the Scale GPS classes when they started to appear in the model flying press and on the various forums, but there are so few locations to fly that size of glider within sensible travel distance of me it seemed unlikely that this would be a possibility. In 2020 I saw reports of the relatively new GPS Sport class, and that became a hugely interesting proposition, and it has now become a bit of an obsession. The big advantage of the Sport class is that the 5 metre span limit means finding a flat field site to launch from is a lot easier than it is for big scale gliders.
My flying has been reinvigorated as a result of trying a new competition, and the new skills I am learning are stacking up alongside re-aquired skills that had become dormant.
©2021 Iain Medley-Rose
Resources
Websites
- GPS Triangle: rules and lots of additional resources
- GPS Triangle League: “next generation glider racing”
Video
- Valenta Chilli Flying GPS Triangle Six Laps (listen in stereo!)
Video Series: ‘In the Air Tonight’ GPS Triangle Racing with Greg Lewis
Video Series: GPS Triangle Racing with John Copeland
Planes List for the UK
Read the next article in this issue, return to the previous article in this issue or go to the table of contents. A PDF version of this article, or the entire issue, is available upon request.
