Inspired by a great question I received from rockyabp in the How to build a Swiss Fish thread, I wrote an article addressing the concepts of “pattern” and “flow” in the context of improvisation and choreography in slope aerobatics. Slope aerobatics involves both, and telling the two things apart is not always so easy – even for the pilot. It’s an interesting subject – check out the article here:
Archive for the ‘Aerobatic Theory & Design’ Category
I provided this VTPR Clinic on Sunday at WeaselFest 2012 in celebration of the 5th anniversary of this website (launched in March 2007). It was well attended and a lot of fun! Andrew v B was kind enough to film it and post to his Vimeo… thanks Andrew!
I hope this is helpful for those getting interested in VTPR… enjoy!
The Slopium prototype is finished and it looks fantastic! This plane use the very cool “Twincam” elevator control linkage and also appears to have some kind of sophisticated wingeron-like setup for the wings. I’m really excited to see what it flies like!!
Now this is exciting! Vincent “Prop-er” of RCPlans.nl has come up with a really innovative solution to the biggest problem facing the increasingly popular “Madstab” 180° rotation full flying elevator: resolution.
The typical Madstab uses a pushrod, pull-pull or pulley arrangement to translate 60° of servo movement into 180°+ of elevator travel. This “crazy” amount of elevator travel is absolutely mandatory for us to be able to successfully pull off tight Madflight flips in the style of Benoit Paysant-Le Roux.
The problem is that we give up a significant amount of elevator resolution for normal flight because of the mechanics of the system. It is a double edged sword and even though dual rates and exponential can help tame it, you still wind up with a fairly imprecise elevator response, making the planes very pitchy in normal flight and harder to fly smoothly.
Hopefully Vincent’s solution, incoporating elliptical pulleys, is the answer to our needs! Based on what I’m seeing above, we should be able to get the majority of exponential required from the mechanical arrangement of the pulleys. This will allow a significantly increased amount of elevator precision around “center stick”, where the vast majority of flying is done, while still giving us a huge rotation when desired.
Vincent has provided the following details:
- Servo cam: Ellipse height 20mm, ellipse width 4mm. (ellipse ratio 0.2)
- Stab cam: Ellipse height 10mm, ellipse width 3mm. (ellipse ratio 0.3)
- Both cams hinged right in the center
- The cam on the tail needs a rounded bottom, as shown in the pics.
I'm very excited by these prospects and can't wait to test them! If it works out, it will mark a very significant turning point, and make this kind of flying even more accessible.
And a third classic French VTPR glider article graces this site, courtesy once again Laurent Berlivet of Jivaro Models. The Air-100 is another famous Breton VTPR glider, right up there with the Excalibur in being synonymous with the French VTPR aerobatics tradition.
The Air-100 is unique amongst VTPR gliders in that it is a scale model of a very successful French sailplane from the late 40s and early 50s, the Arsenal Air-100. To this day, the fullscale glider holds the world sailplane flight endurance record of 56hrs 15min set in 1952 by Charles Atger near Saint-Rémy-de-Provence in France.
R/C models of the Air-100 have been flying in Brittany and the Alps in France since at least the 70s and 80s, and are definitely implicated in “proto-VTPR” flying in Brittany as evidenced below:
Here are some more Air-100 models flying this past summer at Ménez-Hom. Aren’t they beautiful to behold!!
Enjoy this presentation about Eric Poulain’s magnificent 5m Air-100. It is a true classic!
Another great set of scans from Laurent Berlivet of Jivaro Models, this time about one of my very favorite 3D / VTPR gliders, the Madslide by Benoit Paysant-Le Roux (known as BPLR for short). This article appeared in Looping back in the August/September 2000 issue and, when read, still inspires a passionate interest in the design today.
Back when our merry band of aerobatic enthusiasts on RCGroups was trying to sort out Madflight in 2008, BPLR was kind enough to share some very timely Madflight tips with us. Thanks to his timely intervention, and confirmed by our own experiments, the “secret” to Madflight is having at least 180* total rotation on the horizontal stabilizer. Then the flips come fast and furious!
Big thanks to Laurent for again sharing such a classic article with us!
Note that plans for the Madslide in both 1.5m and 2.3m size are available for free on Laurent’s website: Madslide plans
The above is a frontside 360* air performed by a surfer. Pretty sweet move, until recently mostly seen only in skateboarding and snowboarding. So what’s the relation to VTPR (Voltige Très Près du Relief) aerobatics?
Well, the question is, where do we go from here in our VTPR flying?
Last summer was tremendously exciting for the US VTPR aerobatics movement. In the span of just a few months, we saw “Swiss Peter” Richner’s revolutionary ultralightweight “Swiss Fish” building techniques combined with my Le Fish VTPR glider and Benoit Paysant Le Roux’s Madslide elevator. The resulting airframe enabled some truly new things be done in VTPR aerobatics: for the first time, we were able to start doing completely controlled Madflight at extremely low VTPR altitudes in very light lift conditions. Pierre Rondel called it alternatively “underground VTPR” (because of how low we are flying) and “ultimate VTPR”. For his part, BPLR was very pleased to see new development in this area. Super fun!!
Next Dawson Henderson showed us the way towards a reliable, repeatable means of getting Madflight flips on tap via his innovative pulley system. Paige Anderson of Future Slope Designs started working on a chain drive system that shows promise to do the same for his Axis-60 and Axis-72 VTPR gliders. John “Big Gas” Scahill and Dan McCleary have started expanding the palette beyond the Le Fish with their Mad-Extra and DoDo designs. Swiss Peter has started development of his own unique designs which he calls the Swissfish.
In the right hands, all of these nearly indestructible EPP planes can be flown to new limits, with Madflight seamlessly integrated into more traditional VTPR passes and traditional higher altitude slope aerobatics figures, all with good speed and energy management. Finally, a cool synthesis of three popular trends in slope aerobatics over the past 10 years or so!
Great, now what?
Two immediate goals: knife edge loops, and yaw flips aka “pinwheels” (see the surfer video for an example of the latter). Performed as part of a VTPR sequence that incorporated Madflight flips, this could lead to some of the craziest – and coolest – VTPR aerobatics flying ever seen on the slope.
The question is, can our current gliders perform these maneuvers, or will they require radical revision? Increases in side area generally result in increased drag regardless of how it’s implemented, and this can result in loss of energy and possibly make these figures impossible. Conversely, yaw flips may require a reduction in side area, or a change in where it is located – possibly imperiling not only knife edge loops, but traditional knife edge flight, too. As always the trick will be finding the right balance between design and technique to pull these figures off. Can we find one design which can do it all?
So what do you think, are these moves even possible with a VTPR glider? What figures would you like to see attempted? What do you dream of? Leave a comment and let’s see what happens.
Rémi Le Besque, one of the starring pilots from the famous Ménez-Hom 2005 VTPR video, has been kind enough to share with me scans of the original article, written by Eric Poulain, about the Excalibur VTPR glider that appeared years ago in the now-defunct Looping magazine from France. What a cool photoshoot they did, complete with costumes! And what an amazing glider… it still sets the standard by which all other VTPR gliders are judged. The newer Excalibur 2 or “Exca 2″ is even better!
And here is that classic video… I don’t get tired of watching these masters at work!
EDIT: March 13, 2012:
Here is a very rough translation of the most pertinent parts of the article. Enjoy!
by Eric Poulain
After many years of so-called traditional acrobatics, the addicts of Menez including myself, felt the need to practice their passion in a way somewhat unbridled. In other words: let off steam in some academic exercise that a columnist has called “voltige tres pres du relief” (VTPR).
Initially, our gliders were largely inspired by the great Quartz of Francois Cahour. We then had the desire to create machines better suited to our style of flying: thus were born the Sonic of David Luce and my Excalibur.
As you probably already noticed, performance gliders have a curious tendency to look alike: same shape, same profile, or almost. This reminds me of a certain Dolly aging faster than his shadow [Ed.??]. Every summer, I offered to try and sort out a number of models that (daring) friends entrusted me with their first contact with air; this has caused me to shake a little, to see.
Excalibur is the synthesis of these multiple tests. This is the feeling that the shapes of the time were defined: no aggressive lines, good side surface, rounded, nice look (Thierry finds himself an air of Donald. To each his references!) Anyway, this is a mutant.
Has remained define [with] the pen which as everyone knows an essential character in our activity: simple trapeze to facilitate construction, simple though effective ailerons (not full-span, not quadro, not high tech), no complicated wingtip shapes.
In terms of construction, I research the simplicity and cost reduced to its simplest expression. Look no carbon, nor kevlar, balsa at most, fiberglass, a little resin, PU glue and a few drops of plywood, the result to be light and easily repairable, to take a hit without stress.
To tell you about Excalibur, I chose to focus more particularly on the flight. This phase is the culmination of various cogitations and the inevitable construction. The area of application of this glider being large, we first discuss the flight called “traditional” (nothing to do with our bagpipes) and finally VTPR, the settings of the model being identical in both configurations.
Excalibur, as you guessed, is an aerobatics glider. Contrary to what is often observed (free advertising for others) you can make it fly in light winds. I hear the laughter already … aerobatics? Little wind? One thing is clear: to make progress in this discipline, we must fly often, so [the glider must be] for all conditions. It is useless to have a superb model of plastoc that costs over 3500 Francs (plastoc of the poor!) which stays on the ground for lack of sufficient dynamic range while the cronies are turning the crepe in the midst of handlaunch gliders [Ed.: I have no idea what this means, but the gist of it seems to be that it's better to have something that will fly in light lift rather than not fly at all]
Excalibur is piloted using three axes of control, which means that the rudder is not an accessory that can be ignored for aerobatics. Turns should be coordinated under pain of not being able to appreciate its amazing capabilities of scraper [Ed.: scraper = floater]
Despite its low wing loading (necessary for VTPR), the Excalibur is not afraid of the big time and is very penetrating. The profiles used are probably not strangers to this undeniable advantage.
With a bit of zef, aerobatics classic comes together with ease without a playful monster is absolutely necessary. May nothing prevents pushing like crazy on the handle, each has its pleasures!
Loops go straight fingers in the nose (this is only a phrase, please keep holding onto the handles!), including the most beautiful who turn parallel to the slope. Slight gain airspeed, pull, and we must not forget two things: correct a drift [with rudder] at the top depending on the wind and release the handle [elevator] so as not to tighten the loop. For what are the inverted loops, no problem either.
For barrels [rolls], a low acceleration enough to turn them without having to do too much correction. One can nevertheless execute them at the rated speed of the glider, but in this case, we must know how to play the drift [rudder] and depth [elevator] depending on the position of the device [glider].
The Excalibur restores well and its rudder is particularly effective permitting the chaining of reversals and double reversals in small spaces. Adjustments and plan, inverted flight requires little correction has depth and can even scratch in this position, remembering that in this case, the rudder is always necessary and it is reversed.
I believe I read that some think that the knife-edge of significant duration is a utopia in a glider. To have succeeded (and I’m not the only, does not it Biloune and others) with different models, I suggest you try it with the Excalibur. A tip: it is the only figure that requires a substantial speed gain. We push to the playful, is pulled slightly, it sends the ailerons to the switch to the bracket, then you put a background rudder (note: in the right direction, try, you will find) [Ed.: Yeah, the hard way! LOL :p ]. The elevator is then rudder and used according to the wind. When it goes well, it is possible to travel amazing distances.
All chained figures (vertical eight, Savoy knot, four leaf clover) are feasible without major difficulty. Despite this strong potential, the Excalibur is accessible to any pilot skilled in three axis flying. Particularly nice, the Excalibur is rarely in trouble. At large angles and no angle of attack, the stall comes late, with a moderate swing perfectly and catchability.
Its speed range is a surprising extent. Can bomber [Ed.: go fast] or be asked to bring gently in the palm of your hand (interesting if one does not scratch the paint of the fuse), without any risk.
For landing, other than in the hand, I do not use A.F. [no idea what this is] as a glider extends max light wind, better meet the ailerons (45*) like Lucien and Miametons. This parachute the Excalibur.
Before going further, it seems important to mention that the VTPR is not an exercise in kamikaze, practice fades, with no respect or space or people. The level of risk, excluding radio failure is virtually zero as long as certain rules are followed:
1) Never exceed the level of control: one must have a good mastery of classic aerobatics to try the VTPR.
2) Always announce [the glider's] passages and figures.
3) Figures are not made behind your companions
4) VTPR figures are made at the lowest possible speed
The simplest is the classic touch and go: you come in for a landing as gently, you stroke the grass (the sand or water for some …) with the belly of the time and one starts toward the hole. Attention should be able to hear the slight crunch that attests to the success of the maneuver. The trick is to appreciate the speed required for landing before the kiss off again. An alternative is to graze the grass (for example) with a wingtip or with the top of the rudder, implying in the latter case that we present on her back.
And nothing is easier to get [Excalibur] on his back, than a half-snap positive. It arrives flat and has a height compatible with the half-scale (not below 1.30 m for the Excalibur!). In the case of a half-snap to the right, send a bottom depth with pitch, and rudder and ailerons to the right (to help). The rotation is abrupt. To stop once on the back, releasing it while it grows. The accuracy of the judgment depends on the lightness of the wings. The negative half triggered a right to recover a flat, is a similar way: a bottom has bitten deep, drift to the left and ailerons to the right. Moreover, the half-triggered negative saving is a maneuver to get out of a delicate position at low altitude. Attention, it is recommended to train beforehand with water under the keel, except [for those who] love repair.
Series of half-snaps on the spot: wind speed must be greater than or equal to the rated speed of the glider, the figure tackles against the hole, a nominal height of the glider, the figure tackles against the hole, has height eye. It excecute successively triggered a half-positive and half negative snap and start again until the altitude is too low … We must note that at each full turn, the glider tends to go down and ‘taking it well, it is also a solution to land.
The reversals are, of course, part of the panoply of VTPRiste.
All combinations are possible.
- Depart back, slight altitude gain
- Small back reversal at low speed
- Touch and go rudder at the output of the reversal
- Half-snap negative
- Touch and go is flat
- And if possible, half-snaps positive …
- Landing in the hands
No, you are not dreaming and this is not pure fiction: with a little practice and sometimes a few tubes of glue, we get the desired result.
Very pleased to announce that James Hammond, designer of the Vector III and Minivec, has been kind enough to write up an article about his philosophy and approach to designing gliders for slope aerobatics. It’s a quite cool look inside a designer’s head, not to be missed! Read it here: Slope aerobatics and other aerial gyrations