Is there a cheapest/lightest/simplest wing structure other than aluminium tube and fabric?

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Riggerrob

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One way to reduce the weight would be to choose a compromise between rigid-wing and flex-wing techniques. The Wheeler/Skycraft Scout comes to mind, which is a two-axis (rudder/elevator only) powered ultralight with a leading edge rigid spar, flexible cable trailing edge, and cable bracing. The originals had a 12 hp engine and an empty weight of just 50 kg. Later ones were a little heavier but some even had a fuselage pod or even a full fuselage.

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Many clips at https://www.youtube.com/results?search_query=skycraft+scout

That simple wing structure reminds us of the Princeton Sail Wing that only had an aluminum leading edge spar with ribs only at root and tip. Princeton only uses a steel cable for a trailing edge.
Princeton Sail Wing had a lot of promise, but never seems to have been successful in airplanes. The latest versions are limited to wind turbines.
I have wondered if twisting the tubular spar - to twist the tip rib - would be a viable way to bank the airplane?????
Mind you, if lightness and simplicity are high priorities, you can build in too much dihedral and eliminate ailerons altogether. Pendular stability helps a lot when lacking ailerons.
 

Riggerrob

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Complexity I will grant you (two Thomas disc couplings), the "weight" is very debatable as existing airframe structure is replacing a heavy lug on the motor crankcase which is now redundant and can be removed from the crankcase offsetting the weight of the two couplings and shaft.
Furthermore, the larger prop allows for a smaller, lighter motor.

Have you any examples of boom mounted propellers losing in "the Darwinist environment"?

The latest boom-mounted propeller is an electric motor that wraps around the (aluminum tube) boom. It was discussed on another thread on www.homebuiltairplanes.com
 

Blackburn Mark

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The latest boom-mounted propeller is an electric motor that wraps around the (aluminum tube) boom.
I have seen a few of them... The Moyes tempest boom propeller springs to mind and I utterly love the simplicity but batteries are a very serious bottleneck :(
 

oriol

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I like the weld fuselaje of the Mini Fox and the sails. Perhaps a tailless version can be below 70Kgs.

Blackburn Mark have you considered adapting your trike for a hanglider? It will improve the flying characteristics of a paraglider and probably also that of Goat.

Oriol
 

Blackburn Mark

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Blackburn Mark have you considered adapting your trike for a hanglider? It will improve the flying characteristics of a paraglider and probably also that of Goat.
Yes, I did consider building a trike for the Atos or Phantom... Even a standard floppy like the Target.
But for whatever reason, I have landed myself with what I have chosen, I think a tail and aerodynamic controls would be very hard to beat.
 

Riggerrob

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-f.e, KASPERWING with carbon tubes... (2 x 2.5 m= <1.2 kg ) =circa 7 kg wing frame...

+ 20 m^2 sail=2 kg.

Look closely at the "S" curved battens in that Kasper Wing.
Any tail-less flying wing is going to need some sort of reflex (upward curve) in the trailing edge for pitch stability. The smaller the chord, the more precise the curve needs to be. Precise curves are difficult to do in simple, light-weight wing structures.
One reason that Kasper has swept wings is to increase the distance between the center of lift and the control surfaces mounted along the the trailing edge tips.
This is where a long chord delta wing (ala. Facetmobile) becomes helpful. Another advantage is the larger Reynolds numbers provided by the longer chord. The longer the chord, the less precision needed in wing ribs.

On another note: instead of installing a series of bulkheads, stringers, etc. to streamline the pilot ... may I suggest a self-inflating fairing behind the pilot? They can be as simple as the self-inflating butt bumpers worn by para-glider pilots. They only need a scoop in the front and a few knots of airspeed to inflate.
 

Blackburn Mark

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Chotia Woodhopper
Iv looked at the Woodhopper a thousand times, I think its the only example of a true self-buildable powered three axis Sub70kg aircraft I have ever come across.
Or is it two axis....?.... I might be conflating it with the Gypsy, the updated version.

It looks a bit fragile with all that wood but it worked :)
 

J.L. Frusha

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Woodhopper is 2-Axis. Gypsy plans are findable...

Without the wooden fuselage, the Gypsy looks almost identical to the Woodhopper. It just has added ailerons and pedals.
 

keithkrum

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I seem to remember years ago reading about someone who had carved an entire airplane out of a single block of foam, wrapped it in "glass" and flew it quite successfully. It was powered with a 22hp Briggs & Stratton, was incredibly light, sturdy, and fast. I have sometimes wondered if such an approach could be applied to an ultralight class aircraft. I have no idea how it could be accomplished, just a thought.
 

Blackburn Mark

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Peter Sripol's last ultralight wing was cut from blocks of Styrofoam and covered it in some sort of vinyl wrap.
Never saw him fly it after the first flight so it was either a one-off novelty stunt or he had no faith in the finished article....?
 

TFF

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The US gets lucky because our ULs are classified powered 254 lb or 115 kg and gliders 155 lb or 70kg. It’s the same class though. As someone knows here very well, 70 kg and a motor and strong enough to not fold in flight, and be a real airplane is very hard. The numbers are there for a reason, to make it almost impossible to build a regular airplane.
 

TFF

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He has built four ULs. The first was fiberglassed foam. I think no 2 was vinyl. I think the last was oratex.
 

Fiberglassworker

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Oriol,
you wrote,
"Perhaps it is hard to find Sitka Spruce in here, but I probably can find alternative aircraft wood grade on a local supplier."

In Germany the wooden sailplane manufacturers used to use a wood they called Keifer or Baltic spruce in the main spars of their sailplanes. It was actually a pine, a little heavier than spruce but also stronger so a smaller cross section could be used. Most of it came from eastern Germany or Poland.
.
 
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