Servo-Free control in cheap R/C plane 
Sunday, February 11, 2007, 07:28 PM - Flying Contraptions
In the last couple of years, a deluge of ultra-low-cost ready-to-flay R/C plane seems to have engulfed toy retailers. Because servos are the most expensive part of R/C planes, most cheap planes have multiple motors and use differential speed control to control turns.

The Air Panther, available at R/C Trading Post uses a different idea: a small propeller inside the vertical fin. I remember reading about this idea many years ago in the "Cloud 9" column in the now defunct magazine R/C MicroFlight. Now, you can buy a ready-to-fly plane for 35 bucks that uses it.


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Micro Turbines operational in 6 months? 
Sunday, February 4, 2007, 09:54 PM - Flying Contraptions
The Future of Things has a story about MIT's micro turbine project. The goal of the project is to produce turbines that are a few mm in size using the same technology used to produce integrated circuits.

Prof Alan Epstein, who has been leading this research for about 10 years, expects an energy density of 500-700 Watt.hour/kg in the near term, and 1200-1500 W.h/kg in the longer term. This includes the turbine and the fuel supply. The energy density for current Li-ion batteries is about 120-150 Watt-hours/kg.

He says commercial versions producing 10 to 50 Watts could appear in 3 to 5 years.

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Air Midi Micro: Micro RC Equipment 
Sunday, February 4, 2007, 09:54 PM - Flying Contraptions
Air Midi Micros sells Micro R/C equipment from Slovakian manufactrurer Microinvent. They have Gasparin/Potensky motors, including geared pager motors, 4g outrunner brushless motors, magnetic actuators, brushless ESC, and receivers. Not cheap, but worth a look.



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Super Cheap RTF R/C Drenalyn 
Tuesday, January 30, 2007, 06:23 PM - Flying Contraptions
The Drenalyn is a popular indoor R/C design in France (I built many such planes myself, see here, here, and here).

It was only a matter of time before a Chinese toy company would produce a low-cost ready-to-fly version. I actually approached the Air Hogs people a few years ago with the PMAV concept, but they were not interested.

Chinese R/C toy company Hongxin Toys is selling a Drenalyn-like R/C toy, which they call a "Kite Airplane". The widget is available in the US from Geeks.com at the incredibly low price of 70 bucks (complete, with transmitter, battery, and on-board LEDs for night flying!).

Most low-cost R/C toy planes are boring 1 or 2-axes types (without ailerons), but this one has elevons, and is probably fully aerobatic.



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Francis Plessier: Pioneer of Unusual Miniature Flying Contraptions 
Tuesday, January 30, 2007, 05:57 PM - Flying Contraptions
You probably figured out by now that we are fond of flying pancakes at Yann's Techno Toys. R/C plane builders have long built fun planes with low aspect ratio or circular wings. The first example I ever saw was Plessier's "Soucoupe", a circular wing built by legendary French modeler Francis Plessier in the mid 1970's. Plessier flew a Soucoupe (with a smiley face painted on the bottom side) at the annual Cirque des Cigognes in Bretigny. I built my first Soucoupe in 1975, right after seeing his. Francis Plessier always came up with crazy ideas for the "Cirque", such as a flying dog house (below), a flying iron (below), flying lawnmower, and many others. His ideas have been ripped
off (often without proper credit) by airplane kit companies in the US.

Pictures of Plessier's Soucoupe, Iron, and Dog House are available at this page.



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Electric Helicopter Beginner's Guide 
Saturday, January 20, 2007, 02:46 PM - Flying Contraptions
This UK site has an excellent tutorial on electric helicopters by Toshiyasu Morita. The tutorial is available in English and French.

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Excellent Article Series on DIY Brushless Motors 
Friday, January 19, 2007, 07:08 PM - Flying Contraptions
There is an excellent series of tutorial articles on the design and performance of brushless outrunner motors at site of the Southern Soaring Club. The articles give all kinds of details on how to morph CD-ROM and hard-drive motors into airplane motors (click on "articles from Southeasters, and look for the article series by Brian Mulder).


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Reasonnably Competent Pilot flying an SU-30 
Tuesday, January 16, 2007, 11:36 PM - Flying Contraptions
My friend Steve Crandall pointed me to this video of a Sukhoi 30 being flown by (according to Steve) a "reasonably competent pilot". I didn't realize they could put those SU-30 in reverse.



UPDATE: IraqiGeek tells us this is actually an SU-35, and points us to another nice SU-35 video http://www.youtube.com/watch?v=JY8Yv8AM-p8]here[/url].


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Rubber Toughened CA glue R0ckz 
Tuesday, January 16, 2007, 10:42 PM - Flying Contraptions
I have become very fond of a new type of high-viscosity cyanoacrylate glue that contains what the manufacturer calls rubber (not sure it is rubber). It bonds in 15-30 seconds, has ultra gap filling capabilities, and works very well with carbon fiber, and extruded polystyrene (Depron and such).

One is the Flash Black Rubber-Toughened CA made by NHP ($5.75 at BP Hobbies), another one is the IC-2000 made by BSI Adhesives. They are both foam friendly and respond to foam-friendly accelerator.



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United Hobbies: Real Cheap R/C Stuff direct from Hong-Kong 
Saturday, January 13, 2007, 02:49 PM - Flying Contraptions
United Hobbies is an on-line hobby store located in Hong-Kong that sells direct to customers around the world. They have all kinds of Chinese-made R/C stuff at unbelievably low prices. For example a complete helicopter with collective pitch is $101 (ready-to-fly, with radio). They have ultra-low price brushless outrunner motors, and LiPo batteries, e.g. a 3S 4100mAh pack for $52.



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Foldable Indoor 3D biplane 
Friday, January 12, 2007, 12:14 AM - Flying Contraptions
This nice (but expensive) biplane kit is not made of Depron or any other kind of extruded closed-cell styrofoam, it's made entirely of carbon fiber rods and plastic foil. The plane can be taken apart and folded flat.

There is no aileron: the whole wing pivots. My experience with flat pivoting wings for small gliders has been a disaster. I suppose having a propeler blowing on the wings solves the brutal stalling behavior I have observed.



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Cool VTOL concepts from WWII 
Sunday, January 7, 2007, 01:51 AM - Flying Contraptions
During WWII, German engineers came up with a bunch of interesting concepts for Vertical Takeoff and Landing aircrafts. They were never built, but they look pretty interesting.

The first one, proposed by Focke-Wulf, is another one of those flying pancakes with a circular wing and co-axial contra-rotating rotors in the middle of the wing. There is a description (in French) here, and a few pictures of 3D models here.

The second plane called the Triebflugel, was also proposed by Focke-Wulf. It's a sort of helicopter/plane hybrid, with three ¨wings¨ that rotate around the fuselage, serving as a rotor. The rotor is powered by ramjets placed at the tips. A description (in French), with pictures (worth 1000 words in any language you like) is available here.

The idea of ramjets-powered rotors was used in various helicopters, such as that one at the Seattle Museum of Flight. A similar concept (with rockets instead of ramjets) was revived in the late 90´s by the Roton corporation as a way to launch payload into space. A prototype was built and flown, but the company folded in 2001.

While those ideas have largely been abandoned for full-size airplanes, it might be possible to build R/C models of those things.



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More Flying Pancakes 
Saturday, January 6, 2007, 03:44 PM - Flying Contraptions
Speaking of flying pancakes, this reminds me of the Chance-Vought V-173 / XF5U-1 "Flying Flapjack". The plane was was proposed in the mid-30's and first flown in 1942. It featured two large contra-rotating props, which allowed to fly at very low speed and very high angle of attack, very much like our radio-controled Drenalyns. Low-aspect ratio wings are generally inefficient, because of the drag induced by the vortex at the tip, but the props turn in the opposite direction, thereby reducing the effect of the vortex.

More details and pictures are available here, here, and here.




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Flying Pancakes 
Friday, January 5, 2007, 10:59 PM - Flying Contraptions
Speaking of flying saucers and the Coanda effect, I am reminded of the Avrocar. This was a Canadian R&D project in the 50's, which was later funded by the US. The idea was to develop a VTOL flying saucer, but the prototype never managed to fly higher above 1 meter altitude (using the ground effect).


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R/C VTOL flying saucer uses Coanda Effect 
Friday, January 5, 2007, 03:23 PM - Flying Contraptions
Speaking of the Coanda effect, back in January 2006, an English inventor named Geoff Hatton built a very cool R/C flying saucer based on the Coanda effect. He apparently demonstrated a prototype to the UK defense ministry (see video here). The latest prototype is 91cm in diameter and 5.45kg. He calls it the GFS (Geoff's Flying Saucer).

French unusual flying contraption enthusiast Jean-Louis Naudin built several models inspired by the GFS. Unlike Hatton's succint GFS web site, Naudin's site has lots of pictures and videos. Naudin is a creative and skilled tinkerer, and it's too bad that his site is littered with pseudo-science, which does nothing to help his credibility.



Several years ago, my dad made an attempt to build an electric flying saucer (not using the Coanda Effect), but never managed to make it fly in a controlable fashion. The wide-body Coanda trick with slats is a good solution.



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Henri Coanda, inventor of the Thermojet 
Friday, January 5, 2007, 02:42 PM - Flying Contraptions
Henri Coanda (1886-1971) was a Romanian inventor, aerodynamicist, and father of the jet aircraft, who studied at Supaero in Paris, and lived his adult life in France. He is well known for the Coanda effect, also known as "boundary layer attachment": the tendency of fluid to follow the contour of a convex surface, rather than go in straight line. He studied this effect after the crash-and-burn failure of his 1910 Thermojet powered airplane.

The Thermojet, (or moto-reacteur in French) is a predecessor of the jet engine, which uses an air compressor (e.g. a ducted fan) powered by a conventional piston engine, followed by a combustion chamber in which fuel is injected, causing the hot gases to exit the exhaust nozzle at high speed. This is the same idea as the after-burner for electric ducted fan that we talked about before.


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