Flying wing as cheap and simple option for basic fun flying.
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Erkki, I think you want the pilot's butt pretty much on the airfoil neutral point otherwise the pilot's weight overwhelms everything else when it comes to weight and balance. With a very light single-seater, you don't want the engine to balance the pilot, you want the engine to balance the plane like the paperclip on the nose of a paper airplane, and the variable weight of the pilot located where it will have little impact on balance. That's a big advantage of a tractor engine vs. a pusher for this approach.
Otherwise, I agree with you that an essentially constant-chord wing without twist using a straight center panel without dihedral or controls and outer panels with dihedral and elevons is the way to go. You may, however, find that you want to minimize the span of your ailerons to keep from washing out too much of the wing right when you need it most. As a rough idea, I'd suggest wing divided in thirds (left-center-right panels) with elevons taking up only half of the outer panels, so 1/6 span. You could then use vortex generators on the outer panels and/or stall strips on the center panel to tailor your stall behavior if needed.
For a 300 kg gross weight single-seat microlight using a proven flying wing airfoil like the Fauvel 14%, assuming a real world CL of about 1.25 you'd need about 13.5 sq m of wing area so 9 m span and 1.5 m chord at an AR of 6. With a 37 hp Polini Thor engine you should be able to manage a climb of over 4 m per second, top speed about 140 kph and a stall speed under 65 kph. All microlight-legal and very doable, keep the center section to 2 m span and you can have two removable and manageable 3.75 m outer panels for storage and transport.
PS--I like Sockmonkey's high-wing solution, which could get away with no dihedral at all, but I'd put the engine on the fuselage nose for easier access and probably go with tricycle gear rather than a short-coupled taildragger.
Otherwise, I agree with you that an essentially constant-chord wing without twist using a straight center panel without dihedral or controls and outer panels with dihedral and elevons is the way to go. You may, however, find that you want to minimize the span of your ailerons to keep from washing out too much of the wing right when you need it most. As a rough idea, I'd suggest wing divided in thirds (left-center-right panels) with elevons taking up only half of the outer panels, so 1/6 span. You could then use vortex generators on the outer panels and/or stall strips on the center panel to tailor your stall behavior if needed.
For a 300 kg gross weight single-seat microlight using a proven flying wing airfoil like the Fauvel 14%, assuming a real world CL of about 1.25 you'd need about 13.5 sq m of wing area so 9 m span and 1.5 m chord at an AR of 6. With a 37 hp Polini Thor engine you should be able to manage a climb of over 4 m per second, top speed about 140 kph and a stall speed under 65 kph. All microlight-legal and very doable, keep the center section to 2 m span and you can have two removable and manageable 3.75 m outer panels for storage and transport.
PS--I like Sockmonkey's high-wing solution, which could get away with no dihedral at all, but I'd put the engine on the fuselage nose for easier access and probably go with tricycle gear rather than a short-coupled taildragger.
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erkki67
Well-Known Member
With 2,5m deep wing and 6m span this bird would become small and rugged.
With the same 2m span center panel, that would leave two 2m x 2.5m outer panels. You’d also give up quite a bit of climb and glide by dropping the aspect ratio from 6 to just 2.4.
That seems more awkward to transport and store to me than 3.5m x 1.5m panels. In fact, with the center panel reduced to 1.75m, and that length added to the outer panels, the layout I suggested should be able to fit the whole plane in a 4m long x 2m high x 2m wide box trailer, portable garage, or other small structure.
That seems more awkward to transport and store to me than 3.5m x 1.5m panels. In fact, with the center panel reduced to 1.75m, and that length added to the outer panels, the layout I suggested should be able to fit the whole plane in a 4m long x 2m high x 2m wide box trailer, portable garage, or other small structure.
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My thoughts are leaning more towards a variation on the Dobson convertiplane configuration with a fixed propeller, high-mounted delta wing and tricycle gear.
This configuration provides great visibility for landing and sight-seeing. To improve visibility in turns, install a Plexiglass window in the wing centre-section, above the pilot's seat (ala. Citabria). At a minimum, the pilot's eyes need to be a few inches/centimetres below the wings' bottom skin (ala. Cessna 172) to provide adequet lateral visibility. Hopefully the pilot's eyes will be far enough forward to keep the runway in sight as he/she turns out final approach ????????
Tricycle gear can be "fixed" at the best angle for landing and take-off (ala. Dyke and Verhees Deltas). The nose wheel should be large enough and soft enough for soft-field landings. At first guess, the nose wheel leg only has to be long enough to keep the prop out of the mud ... then increase the length to make room for the pilot. Fair the nose wheel leg into the leading edge/windshield of the cockpit. The windshield can be a simple flat wrap of plexiglass.
Re crash-worthiness, the basic cockpit structure needs to include a rigid roll-cage. Fortunately, that roll cage can also carry most of the landing gear loads. A semi-teardrop of crushable foam under the cockpit can help absorb the impact of bad landings ... hopefully preserving the pilot's spine.
Since the wing will be so thick and have such a short span, it can be made of any material the builder prefers though my bias is for CNC cut sheet aluminum because it is already so popular with kitbuilders (e.g. RV series).
The light wing-loading of a delta will help reduce landing speeds for short field operations. It might not climb very steep with a small engine, but at least the delta provides a short ground roll.
We might even install main/tail wheels in the bottom ends of the tip fins. With large enough tip fins (ala. Facetmobile) you get the same lift-to-drag benefit as a longer aspect ratio.
This configuration provides great visibility for landing and sight-seeing. To improve visibility in turns, install a Plexiglass window in the wing centre-section, above the pilot's seat (ala. Citabria). At a minimum, the pilot's eyes need to be a few inches/centimetres below the wings' bottom skin (ala. Cessna 172) to provide adequet lateral visibility. Hopefully the pilot's eyes will be far enough forward to keep the runway in sight as he/she turns out final approach ????????
Tricycle gear can be "fixed" at the best angle for landing and take-off (ala. Dyke and Verhees Deltas). The nose wheel should be large enough and soft enough for soft-field landings. At first guess, the nose wheel leg only has to be long enough to keep the prop out of the mud ... then increase the length to make room for the pilot. Fair the nose wheel leg into the leading edge/windshield of the cockpit. The windshield can be a simple flat wrap of plexiglass.
Re crash-worthiness, the basic cockpit structure needs to include a rigid roll-cage. Fortunately, that roll cage can also carry most of the landing gear loads. A semi-teardrop of crushable foam under the cockpit can help absorb the impact of bad landings ... hopefully preserving the pilot's spine.
Since the wing will be so thick and have such a short span, it can be made of any material the builder prefers though my bias is for CNC cut sheet aluminum because it is already so popular with kitbuilders (e.g. RV series).
The light wing-loading of a delta will help reduce landing speeds for short field operations. It might not climb very steep with a small engine, but at least the delta provides a short ground roll.
We might even install main/tail wheels in the bottom ends of the tip fins. With large enough tip fins (ala. Facetmobile) you get the same lift-to-drag benefit as a longer aspect ratio.
That’s a interesting idea, Rob, but the somewhat exotic aerodynamics seem to take the concept away from the idea of “cheap and simple.”
Maybe something like post # 1941 but ensure that the aircraft is trailer-able like a Fauvel AV36?
I think the rudder can fold also. The engine may need to be removable or possibly hinge up and over the wing.
But anyway was thinking the wings would be lighter possibly if they did not need to fold or be removable?
And it could be tri-gear? But I like conventional myself.
I think the rudder can fold also. The engine may need to be removable or possibly hinge up and over the wing.
But anyway was thinking the wings would be lighter possibly if they did not need to fold or be removable?
And it could be tri-gear? But I like conventional myself.
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A caveat about struts, the design looks cleaner without them but the wings may be lighter with them? Of course they are drag, but you can put things on them like ... your hands ... and maybe even a nice little arm rest might be a nice touch.
Tiger Tim
Well-Known Member
If the design is tolerant of small builder errors the only real hard work is up to the designer.
103
Well-Known Member
What do we know about the SE-XSL, Fauvel AV 222 ? 
I have reached out to Hans but no answer yet. Looks like a monowheel glider with a VW grafted on the nose.
I will ask him to join HBA and comment here.
Some detail here Fauvel AV.22 - Wikipedia woudl be great to hear of the operational profile in 1st person@
Update I keep learning more about this wonderful wing
Hans gets honorable mention as a builder Charles Fauvel and his Flying Wings
Model video
Matt
I have reached out to Hans but no answer yet. Looks like a monowheel glider with a VW grafted on the nose.
I will ask him to join HBA and comment here.
Some detail here Fauvel AV.22 - Wikipedia woudl be great to hear of the operational profile in 1st person@
Update I keep learning more about this wonderful wing
Hans gets honorable mention as a builder Charles Fauvel and his Flying Wings
Model video
Matt
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nestofdragons
Well-Known Member
This seems to be a ongoing project of a Fauvel inspired glider. Building a Fauvel AV-361 - El Paraiso
Also go see this modern evolution of a Fauvel design. The Choucas. Choucas
erkki67
Well-Known Member
Where did the simple and cheap go?
erkki67
Well-Known Member
If it has to remain a Fauvel, rather Id go with the AV44, the wingspan is just more user friendly.
Best question asked in the last several pages!
I'm still committed to getting the AV-36/361 plans back in circulation* but it really doesn't fit this category well. Something closer to the Opal or Pelican, to me, looks like a better option. As much as I'd like to build an AV-361 for myself I just can't see it being possible/practical for me for several years, partially due to the cost of wood and my current lack of building space.
*Personal situation/Covid has really taken it's toll. Today I start my search for for a 9-5 J. O. B. A return to 60 hour weeks won't leave much free time.
That means less time with the W.I.F.E.
Edit: Forgot or didn't know today was a holiday. The start of new opportunities will have to wait until tomorrow.
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Not so sad.I've got the lawyers out of my life, have marketable skills and there actually are open jobs in my county.
The new roof on my converted chicken house workshop doesn't leak. I've got basic electricity and heat installed. I started with less 40 years ago............and I've got a lot more experience.
Please remember the warning given to me by Ray Cote, at my very first race pilot briefing: "Old age and treachery will overcome youth and skill !"
I bid you great success in wreaking treachery and skill (and havoc on the young) during your job search
I bid you great success in wreaking treachery and skill (and havoc on the young) during your job search
erkki67
Well-Known Member
Ok, we are still looking for a cheap and simple layou, its not going to be much simpler than this, most difficult part are the wing tips on this bird of Sockmonke, all ribs have the same size, the wing spars are straight, the landing gear could be straight, the engine mount could be made like on the Fritz round wing.
erkki67
Well-Known Member
It would be great if Sockmonkey and Fritz would hang together, they would come up with a bunch of simple designs.
Speedboat100
Well-Known Member
I am not sure...big pleksi canopy...retractable landing gear ?
Erkki, the little high wing that you put in post #1957 will be nearly un-controllable on the ground. An aircraft of this configuration will need to be a conventional nose-gear design, not a taildragger.
Sockmonkey, would you be kind enough to move the main gear back a ways, and put a little nosewheel at the front of the pilot pod? If the world can't keep Erkki's boundless enthusiasm below nuclear fission levels, at least we can give him half a chance to keep the airplane on the runway
However, there is still a potential danger in this configuration... the thrust line is above the center of gravity, and this creates the same nose-over ("bunt") potential as they have seen in gyrocopters with a thrust line above the CG. The wing chord will have to be fairly large in proportion to the thrust line's distance above the CG.
Sockmonkey, would you be kind enough to move the main gear back a ways, and put a little nosewheel at the front of the pilot pod? If the world can't keep Erkki's boundless enthusiasm below nuclear fission levels, at least we can give him half a chance to keep the airplane on the runway
However, there is still a potential danger in this configuration... the thrust line is above the center of gravity, and this creates the same nose-over ("bunt") potential as they have seen in gyrocopters with a thrust line above the CG. The wing chord will have to be fairly large in proportion to the thrust line's distance above the CG.
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