Compressed air and flight

However, today they are rarely seen outside in the flying field, although due to the efforts of Stepan Gasparin, and Bill Brown, often seen at indoor meetings.

I am certainly no expert on the history and development of CO2 engines, but what I like about them is the ease of starting. You just fill the tank and flick the propellor, and although it might be running backwards, the engine is definitely running. No fiddling with fuel, no adjusting of throttles, compression screws, tanks, fuel levels, just fill and go, remembering to oil the motor occasionally. There are, however, certain difficulties in their use that have to be accepted, for example, they don't run very well in the cold, the 'fuel' comes in relatively heavy bottles, and obvoiusly the air supply system must always be kept airtight. My experience is also limited to a few years use of these types of engines, so I don't know what it might be like trying to keep them running in ten years time. However, some of the motors I have bought are at least that old, and they look like they have a good few years left in them. Only time will tell.

What ever you do make sure you look at Stephan Gasparin's website, because he and Bill Brown are two of the greatest makers of CO2 motors the world has ever seen.

My own experiences with CO2 motrors started back in 2003 when I bought a GM300 to fit into the Warden Flyer, a Tony Draper design intended for a one-model competition at Old Warden. I did not buy another motor until 2006/7, when I heard that Stepan Gasparin had stopped making his delightful engines. So on the basis that if I did not buy them soon, there would not be any left to buy, I started to acquire a few. I now have a small selection of Gasparins, a couple of Telcos (including a 3000 and 6000), a Modela, two Mistrals and one Shark. So far I have only seen one of the smallest Browns, but the price being asked made me catch my breath, so it is unlikely that I will get to own one, despite their reputation. In addition my mate Dave bought me two of the Russian motors that are currently available on eBay for around £20, which seems very good value indeed.

Fozzle

The Fozzle is an unusual model in that it is a flying wing biplane. Rather like a Dunne Biplane without the stubby fuselage. It flies well under the power of the Telco, for which it was designed by W D Binns, but as with all biplanes glides quite steeply, once the initial burst of power declines.

This is Ok in that it will almost certainly prevent it flying away in a thermal, but it also means that the landings are a bit heavy. Most result in the model turning over in a somersault, and some result in the leading edge of the wings breaking because they hit some kind of projection. On a normal model the fuselage and undercarriage would be first to take the punishment of landing rather than the wings. The end result is that I have managed to break the leading edges of the wings on several occasions.

Fozzle flies in suprisingly tight left or right hand circles, but still manages to either maintain height or climb, depending on the quality of the air.

Cute, ain't it	Delightful Telco motor is surprisingly powerful

In the write-up that accompanies the plan in Aeromodeller, the designer says that on one occasion his copy of Fozzle, performed three consecutive loops, and at the time I first read this I was slightly sceptical. However, having built, and flown Fozzel, and spent some time adjusting the Telco I can well understand how this might happen. The throttle adjustment is very sensitive, requiring only minute adjustments to increase or reduce the power output, and it is suprisingly powerful.

I guess this is a model for Salisbury Plain during the summer when the fabbled long grass, always mentioned in the flying section for new models, is at least a foot high.

Control liner - the plane with no name!

This is a rarity for me in that it is an own design built for the March 2007 Impington indoor meeting. Control line models are fairly simple, but I was surprised just how well it flew. I kept the construction as simple and as light as I could, and put a GM 120 on the front. I arrived at Impington with it unflown and untested, so was pleasantly surprised to see it fly at all. In fact, once the centre of gravity was established, and the engine power output was adjusted, it managed a single loop on the first circuit, then about five circuits before the gas charge ran out. Whoopee!

What was required for longer flights and more aerobatics was more power, and or a bigger engine, and, with this in mind, Mike Parker (the one from Hull) has loaned me a GM 120 twin to try. I can't wait to bolt it on the front and see what it will do. However, I have no experience of running twin CO2 motors so do not know if it will run slower, but turn a bigger, coarser prop, or what. In the mean while I dream of indoor figures of eight, wing-overs, inside loops, and lots of aerial combat!

KISS is a good maxim for all aeromodellers	The lovely GM 120 single

The 120 twin will be fitted to this model soon, but until the Autumn of 2007 I will not be going to any indoor meetings, so the results will have to wait a while. What this space, as the saying goes.

The fabulous GM 160 twin just oozes power

However, the resulting flights can be improved apon, especially as the engine has not yet been adjusted from the factory settings, and it will be possible to increase the power output at the expense of duration.

During the second flight I was able to do two consecutive loops, which is an improvement on the GM120. So, if I can sort out the leak, and get myself a fresh cylinder, I could be performing those elusive eights and wing-overs. Well, perhaps.

Bantum

The original Bantum was designed by Ron Warring, and this version by David Deadman is reduced to 26.5 inches wingspan. It was featured in the February 2003 edition of R/C Model Flyer, and is still available via the publishers website. Click here to go to R/C Model Flyer.

I think this copy was actually built for and featured in the Flyer review, and I bought it from Richard Crossley who was kindly selling David Deadman's models after he died in 2006. It is a typical DD model, beautifully built, wih lots of lightening holes cut into the ribs, and finished with love and great care. It flys on a mere whiff of CO2, and in still air on only half a gas charge easily reaches 30 foot altitude. On Salisbury Plain in early June 2007 I came close to loosing the Bantum. Having put in half a gas charge it went straight into a thermal and within minutes was OOS, and only a quality pair of bins allowed me to follow it to a soft landing in long grass about half a mile away.

Delightful little model	Some of the many lightening holes in the wing ribs?

This model definitely has my name and address firmly glued on, as it is highly likely to fly away without notice! It is one of my favourite models partly because David built it, and partly because it flys so well. To appreciate it most it must be flown at the end of the day, when the still of the evening descends. Then you can hear the motor ticking over and see the flight pattern and the model itself to best advantage. Wonderful.

Wing Thing

This is one of the many published designs of Mark Bees. Over the years Mark has produced loads of designs for small to medium sized models, for co2 power, rubber, glider and even jetex. Most are easy to build and so automatically have maximum fun built into the design. This is one of the easiest, but despite this has proved one of my biggest failures.

As you can see from the second picture below the extra nose weight tells a tale of too much weight behind the centre of balance. I think it must have been the extra coat of sanding sealer and the car spray finish.

Should have flown like this	Would only just fly like this

So althought it flies it struggles to gain height and will have to be rebuilt and the weight kept down by careful finishing. I will post new pictures of the mark two version as soon as I complete it.

Baby Ace

This is a model I bought at the Aldershot Model Club Bring and Buy Sale in 2007, (actually an auction, but that is another story). I think it is a Baby Ace, but is definitely powered by a lovely GM24.

As with all indoor flying the problem is the walls, other aeroplanes, other flyers, rafters, and the fact that the ground is very hard!. The Baby copes well with the reduced airspace indoors, but although happy turning left under power, it is rather inclined to straighten out as the power declines, resulting in an unforgiving contact with the walls, or a handy modeller, or one one occasion a modellers table covered in his models! So perhaps I could try right hand circuits just to see what happens.

Could almost be full size . . .	. . . but where is the pilot?