I have a couple of Midwest Sniffer free-flight airplane kits in the storage unit. I built one of these as a teen, and it’s a great flyer.
The Sniffer has a ‘dethermaliser’. The front of the tail surfaces is held to the fuselage, which acts like a hinge, by a rubber band and may tilt upward. The trailing edge and the end of the fuselage have wire hooks. A metal tube on the fuselage holds a fuze that passes between the strands of the rubber band that holds the hooks together, and keeps the tail surfaces from tilting upward. If you’ve cut the fuze to the right length, the lit fuze will break the rubber band just after the Cox .020 engine runs out of fuel. The horizontal stab tilts up and causes the model to stall so that it doesn’t climb away in a thermal and get lost. I lived in the desert at the time, so I never lost my airplane – though I did have to ride my Enduro to retrieve it.
Nowadays r/c gear is cheap and tiny. Cox engines have ceased to be, and people use electric motors. But what about back then? What about people who want to fly gas-powered free-flight planes now? Not everyone lives in a desert or farmland. Where did, or do, people fly?
IIRC there were clubs that people would join and the club had some land that they would use. I recall one being at the edge of town where I grew up in farmville Ohio. They would do dogfights and aerobatic stunt flying with smoke trailers. Cool to watch back then.
I moved storage units at the end of June, and there were the two ‘Sniffer’ kits (plus plans for a Super Sniffer). I don’t know when – or if – I’ll build them, but I’ve received a Cox .020 Pee Wee engine, and another one is on its way. So naturally, I’m wondering again about where to fly them.
Where I live, there is a very wide mud flat when the tide is out. Not sure I’d want to risk a dunking though. And there are tall cedars near the shore. Also not ideal. There’s an R/C flyer’s club field about 20 minutes away. Looks like a good flying area, but I wonder about retrieving my plane because I’m old now and my injured knees haven’t gotten any better over the decades.
Maybe I could make one radio-controlled; only, I don’t know if Hobby Shack is still in business and I don’t know where to get the transmitter/receiver/servos.
I just sold the P40 R/C Flying Tiger Warhawk that had been hanging in my garage for 20 years. It had the the motor, servos and controls with it. Damn, it looked good tied to the rafters, but I am downsizing for a move. Never considered flying it, as I knew it would get lost or damaged.
The Lil Sniffer is designed for Free Flight so it is over stabilized with the polyhedral wing. A single channel radio can give you enough control for return to launch, but it won’t get you out of a thermal. Blipping the rudder will change the flight path and cause the model to bank a bit. The models roll recovery will determine its’ new direction. I’ve tried it and found that it kind of worked but wasn’t worth the effort.
The Free Flight model is designed to make the transition from a powered climb to a flat, gentle glide. The major control you have is the engine run time. On a small field the engine run would be from 5 to 10 seconds, A further technique used for small field flying was to decrease prop efficiency by putting the prop on backwards.
Free Flight is the queen of power modeling. Correctly trimming a model to fly on its’ own is an accomplishment. I suggest that you build the model to plan and enjoy the result. Just keep the engine run time low enough to fit your field.
Free-flight models are not radio controlled. They literally fly free; uncontrolled. They can be as simple as a rubber band-powered glider you’d buy in a convenience store, rubber band-powered built-up balsa-and-tissue models (some of which you can put .020 or .049 engines in), or larger models, like the Sniffer, that are designed only for fuel-powered flight. In each case you launch it, and it goes where it goes.
(Incidentally, I am shocked at the prices I saw while looking for examples.)
Ah, gotcha. This is a hobby with which I was previously unfamiliar.
Would a device with onboard electronics designed to control itself autonomously also be considered “free flight”? I imagine there’s some gray area, there.
There has been a lot of controversy over the years. In the 1950s competition free flight models began to use mechanical devices to adjust the transition from power climb to glide. Various devices had been employed over the years but in the fifties it became extreme. Clockwork timers were used the adjust engine rpm, wing incidence and lateral control surfaces. Also accurate devices were employed to bring the model down after the maximum allowed flight time had passed.
Recently mems devices have made possible automated stabilization. I believe they address your question. For sport and scale flying these devices will control the model and are widely used, but they are limited or not allowed in competition. The US controlling organization is AMA.
I recall 1960s era free-flight gliders where the horizontal tail had one rubber band that would pull the tail upwards at a 30 degree or so angle and an opposing stronger rubber band that would hold it faired in the normal position. You’d rig what amounted to a slow burning fuse passing through the second rubber band, light it, then launch the glider using a very long stretched-out bungee cord or surgical rubber tubing.
It’d climb steeply as the bungee / tubing relaxed, then at a couple hundred feet altitude it’d detach from the tow cord due to the changing angles as the glider overflew the ground end of the cord.
Once free, the glider would go wherever doing whatever until the fuse burned through the second rubber band. At which point the tail would snap up, the glider would nose up into a deep stall, then more or less gently mush down to the ground like a falling leaf.
Yes, as in the OP. With the Sniffer, it would climb until it ran out of fuel, and the stab would pop up to bring it back down. It’s a safe bet that the Brothers Rutan flew these when they were kids.
When the thread was revived I picked up with your post #3. Never even saw the two above. The thread showed up in my Unread queue so I must have read the first posts 5 years ago when it was fresh.
There’s one on eBay. Currently, it’s at $83 with three hours to go. Only… I still haven’t built the two Sniffer models I have, nor the many Guillow’s kits I have. I’ll let it go.
Never considered flying it, as I knew it would get lost or damaged.
With the Sniffer, it would climb until it ran out of fuel, and the stab would pop up to bring it back down. It’s a safe bet that the Brothers Rutan flew these when they were kids.