# Modern day "motorcycle of the air" aircraft class?

Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by cluttonfred, Oct 3, 2015.

1. Oct 4, 2015

### cluttonfred

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I think we have a language issue here, Starujumper7. "Trike" can mean tricycle gear but autoreply and I were referring to the three-wheeled frames with a pusher engine used with flexible delta wings as microlight aircraft. There was no landing gear restriction in the concept I was describing.

ultralajt, you are definitely in the spirit of what I had in mind when we started this thread but safety issue of crashing head first rather than feet first makes me wonder about that arrangement. If maintaining the idea that the pilot should straddle the fuselage then I would tend to go with something like the recumbent motorcycle in post #8, but perhaps just an ordinary open cockpit would be enough.

2. Oct 4, 2015

### Aesquire

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Modern Trikes are the scooters of aviation. Lots produced, one to two seat aircraft with open air cockpits and performance from 30+ mph up to around 100 mph. Motorcycle riders tend to look down on scooters. ( I don't ) Like I said, they violate pretty much every spec you want.

I'm skeptical of ANY design effort that begins with an arbitrary wing span limit. It's one thing to be stuck with legal limits on performance like pt. 103 or LSA, then you have a box to work in to achieve your goals, and just have to accept them. It's not a horrible idea to have goals like "fit in a standard shipping container" or "be road trailer sized" to transport from home garage to airport. OTOH the pre-WW2 RAF limit on wingspan to fit the old hangers resulted in a large number of casualties when British Bombers didn't have the altitude capacity to fly above medium flack.

Sometimes you are just stuck with limits. Sometimes the limits make perfect sense in context. ( Fit in this box for storage ) Sometimes they bite you.

I can think of several "clipped wing" designs that sold well, ( Piper cub ) but few that developed long wing versions. ( RB-57 ) Please correct me on that.

3. Oct 4, 2015

### Starjumper7

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I meant tricycle landing gear, yes. Here is the twin boom pusher with a larger spinner. Larger spinners always = more sexy. Does this seem like it could qualify as a good motorcycle of the air for you? It's pretty conventional and straightforward.

I envision the booms at 6 foot width and the 6 foot wing tips can fold up or unplug. With larger diameter skinnier motorcycle type tires.

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4. Oct 4, 2015

### Aesquire

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Modern "racing" inspired motorcycles have the feet behind the butt and a crouched jockey position mostly to look fast. Few street riders tuck down behind their tiny wind screens to gain the aerodynamic advantage real racers use on the track. At least not for any length of time. I'ts a painful position for young skinny guys, not fat old farts like me.

Modern "cruising" motorcycles have the feet out in front of the butt, and a laid back position made popular by movies like Easy Rider and offer the joy of doing a pull up all day long. Again, style over function, but generally more comfortable than jockey position.

Touring bikes have the feet more or less under the butt, for a balanced stance and maximum comfort on multi-hour thousands of miles journeys. Often with secondary front foot pegs ( cruiser style ) to offer a position change to reduce fatigue, and many riders also use the rear set passenger pegs as a comfort alternative position.

There's no reason not to build a relatively slow draggy airplane with the pilot straddling the fuselage instead of being inside a cage, as long as you can strap the pilot down properly, and have energy absorbing structure protecting him/her in a crash. Don't expect a cruising speed much in excess of 70 mph to be comfortable. An exposed pilot will become the draggiest thing on the aircraft as you clean up other aspects... then it's time to fair him in.... and he might as well be inside the structure then.

"To me, the idea of 'motorcycle' of the air means something that is kind of open and allows the pilot easy entry and exit, without a lot of tubes and wires all over the place, so that eliminates the pilot hanging in a cage of tubes and wires."

Contrast the fun of climbing into a Piper Cub, crawling onto a Wee Bee, and sitting down on a Maverick RT. Maverick 2 RT Ultralight Trike · North Wing

5. Oct 4, 2015

### BJC

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There are examples within the E-AB world of designs that increased wingspan, although none come to mind that match the extent of the RB-57 mods.

Longer tips were added for the Glasair series, and the W-8 Tailwind morphed into the W-10 with the extended span tips. Slower landing /stall speeds for each, as well as faster cruise at altitude. The Cassutt end up with a longer span wing too, with both tapered (by individual builders) and rectangular wings designed by Cassutt. The RV-12 prototype wing was increased in area (but not span, IIRC) to meet the LSA stall speed requirement.

I'm sure that there are other examples.

BJC

6. Oct 4, 2015

### Sockmonkey

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That's a pretty good point to make in that it shows where the compromises can be. Sacrificing speed opens up other options like using a high-lift type airfoil that wouldn't work in the 80-120 range where most small planes go.

7. Oct 4, 2015

### cluttonfred

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The span limit is intended to be aesthetic as much as anything else. There are certainly many small monoplanes of approximately that span, and the span limit would also encourage folks to look at biplanes as a realistic option. Only in very special cases can a biplane be more efficient than a monoplane if held to equal area, but if the only constraint is span then the biplane starts to look interesting.

8. Oct 4, 2015

### Starjumper7

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I assumed that a fairing was a good thing, but now I think it's not. This is more like a motorcycle, and the exposed pilot doesn't really add so much drag because much of his 'interference' is cleaned up by the fuselage and rear prop. Even I can't beat this.

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9. Oct 4, 2015

### cluttonfred

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That's great Starjumper. If we did keep the "riding on" vs. "riding in" idea to keep that motorcycle feel, I wonder how we would define it? Yours seems to do a good job, but for a tractor-engine configuration it would be harder. I would keep at least a little forward fairing (to keep the wind from blowing up your pants leg) in your design as well as aa windscreen.

10. Oct 4, 2015

### Starjumper7

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As is common in motorcycles, you can add to the basic 'naked' look with aftermarket front fairings and windscreens in a great variety of styles =) A permanent mini fairing in front of the feet is a good idea.

If you are riding on it vs. in it depends on the riding position, If a person is leaning forward/prone then they can straddle a central frame, but if they are reclining there can be no central frame, it's like sitting 'in' a low sided canoe.

With a tractor engine the riding position is possibly a little more challenging due to structure. Also, with a tractor engine you would want a boy racer/prone riding position or it would end up looking like every other nasty looking little single seat plane than has been built.

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11. Oct 4, 2015

### Aesquire

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Thanks BJC, I'd forgotten the Glasair. That, like the Lancair series grew as folk put bigger engines and more avionics in. Weight almost always goes up.

Starjumper7, sure you can have a central frame in a reclining position. Yes, it will probably look like "every other" Air Bike built. Not so much like a Cessna.

I do like that Air Cycle drawing. The important streamlining in that design will be the area behind the pilot, where modern motorcycles are completely lacking. If you taper the fuselage behind the pilot at longer than a 3 to 1 ratio, you can eliminate a LOT of drag, and still keep the open air feel you want.

I understand that a Trike isn't the desired machine, but you can learn from the best of breed, the Maverick from Northwing gets much better performance with the bags fairing in the back of the pilot. The Dragon trikes from Flylight use lightweight plastic fairings to achieve the same goal. While the Northwing Solairus uses a composite fuselage shell ( Carbon & glass as needed ).

Dragons Homepage

Solairus · Light Soaring Trike · North Wing · 509.682.4359

To design any aircraft in the 21st century without standing on the shoulders of those before you, ( stealing ) from Orville & Wilber on, is nigh impossible. That doesn't mean you shouldn't be as original as you want... as long as it works. No matter what you build someone is going to complain it's just a Model X with Model Y tail & a Model R wing. Don't listen to them.

12. Oct 4, 2015

### Starjumper7

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Actually on something like this it would feel like riding on a surfboard in a bucket seat rather than sitting in a canoe, more in keeping with the motorcycle theme. This ends up looking like every other little twin boom pusher you ever saw if you put a lid on it, nothing new here. Except the feeling. The engine compartment is wide open top and bottom, only has sides, a pretty minimalist fuselage ... ten feet long nose to prop, 18 X 18 ft OA, or 18 X 16 if you make the Vertical tails bigger and closer. Well its been fun drawing cartoons on a cabin fever rainy day in paradise, a remote part of the cloud forest near the crest of the Andes mountains, I should be writing a book. Now before I turn into a lump I'm going outside and dig or stretch or something, my rubber boots are on !!

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13. Oct 4, 2015

### Starjumper7

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Yes I guess you could if you used a big beefy tube, like a large diameter thick wall aluminum tube, annealed, curved, and then heat treated. You can also weld fitting on the tube while it's annealed, and then heat treat it all together.

14. Oct 4, 2015

### cluttonfred

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15. Oct 4, 2015

### DangerZone

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Starjumper, your drawings are pretty good and deserve some refining and a couple of suggestions...

Rise the airfoil to above the pilot's head so the leading edge is level with the top of the canopy. Get the fuselage to envelop the engine, lower the engine case to be the lowest part of the fuselage. Get the PSRU to allow higher prop axis and better clear the prop from the ground. Lose the twin booms and get a single boom from below the engine, protecting bith the engine carter and the prop from striking the ground. Draw two versions, one with the tail advanced before the prop like in BD-5 style and another with after the prop. You could draw a version with last wheels on the edges of the tail (in that case airfoil tilting will be needed just like in trikes) and a single front wheel like in some motorized gliders (Falke for example) and direct steering like in motorcycles. Reduce the prop size, such aircraft are usually light so you can achieve pretty good efficiency (and neglect the losses) even with a smaller size prop. The moment arm with an airfoil sloghtly above the prop thrust line could compensate for the shorter tail arm like in some French aircraft. In other words, you might get an aircraft with less drag but more performance and handling, see how you feel about that.

And the most important thing, have fun.

16. Oct 4, 2015

### rtfm

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Hi,
All this talk about a modern motorcycle of the air - what's wrong with this?

or this close-up of the seating position...

It seems to have everything. Sporty good looks, bike-like seating. And it looks like a lot of fun.

Duncan

Air-Bike103
Plan Set $150 Weld Package$2850

http://www.jordanlakeaero.com/ultralight.html

Complete Kit $6995 Short Kit$2950

Complete Kit with Hirth F-33 engine
and GSC Prop \$10,895

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17. Oct 4, 2015

### Sockmonkey

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I think the reason he doesn't just go for one of those is that he wants to hide or eliminate the spars and wires and stuff for a sleeker more compact look.

18. Oct 4, 2015

### rtfm

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Oh. OK then, he could always wrap the aft fuse with one of the lightweight materials? Add almost nothing to the weight. Do it in an afternoon. That's what I'd do, anyway.

But then again, there is always the challenge of designing something unique to yourself.

Duncan

19. Oct 4, 2015

### markaeric

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It may not entirely be in the spirit of the OP's proposal, but I had envisioned a 90 degree rotated H shape with a centrally located lowish pressure compressor routed through ducts that are each leg of the H. At each end of the duct is a rotatable nozzle for yaw and forwards/reverse thrust. Seating is like a motorcycle with the seat pivoting L/R to shift the CG for roll control. To minimize the size of the powerplant which drives the compressor and to give finer thrust control at each nozzle, each of the ducts has an integrated burner for thrust augmentation. Admittedly, that's not particularly fuel efficient, but it's not meant to be used for distance flying. It could be possible that each leg makes up a slight airfoil to increase efficiency somewhat when flying forwards. One of my personal concerns is the heated gasses coming out of each nozzle, so you really wouldn't want to roll it out on a grassy field or something and take off. A possible option is a fire resistant pad/blanket that can be rolled up which is used for takeoffs and landing. Such a design would be very compact and light weight - targeting the american ultralight class. This is not too far off from the various Hiller flying platform designs.

20. Oct 5, 2015

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