Very low aspect ratio planes?

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Riggerrob

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Dear Cluttonfred,

Junkers flaps and ailerons work best at low airspeeds. They remain effective at low air speeds because they are outside the turbulent boundary layer.

All control surfaces work best when hinge lines are perpendicular to air flow. IOW controls work best when hinges parallel the span.

Next question: How do we hang Junkers ailerons under the wing tips of a rhomboidal Pana-Canova?
 

Aesquire

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I wonder if simple flat control surfaces would work for this application?
That far back on a long chord wing, the boundary layer is quite thick. Simple hinged at the trailing edge control surfaces would need to be bigger and there'd be a "soft dead band" in the controls at low deflection.

The advantage of the Junkers type surfaces, on most aircraft, is you can attach them to a rear spar or other thicker structure forward of the trailing edge, which can then be fairly simple and easy to make triangular bits.

The downside is a bit more drag, a more complex to make, and heavier elevon, slightly heavier hinge/mounts etc.

There's a reason Vought went with the external all flying horizontal stabilizer elevons on their low AR designs. It put the control surfaces in cleaner air, right in the tip vortexes, perhaps, but out of the slower boundary layer. It helped that the team at Vought didn't care anything about "purity of design" and focused on the mission requirements. Usually. ;)

If you consider the F4U & XF5U & F7U & F8U progression of designs, the '5 was cancelled by the Jet Age ( prematurely, imho ) and the '7 was crippled by underdeveloped, underpowered engines, ( a common problem in that era for military jets and a concern for homebuilders since the Wright's ) and maybe a bit too much with looking like a '56 Chevy hood ornament...


( yes I do know it's the other way around... :) )
 

rotax618

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The later Arups put a tailplane and elevator high up on the rudder out of ‘dead’ air, and didn’t suffer from blanking by the wing as at higher angles of attack there is a powerful vortex on the top surface pf the wing. You could rotate the tips for roll control like the S2 Arup. Junkers type surfaces would work but are draggier and more prone to damage under the low wing.
 

cluttonfred

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Thanks all, some interesting points. FWIW, P-C seems to have tried and then abandoned the Junkers control surfaces, here are the PC.100 and PC.650, presumably earlier and later than the PC.140 with the Junkers surfaces.

pc100.JPG pc650.png
 

rotax618

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You will need a very light engine to have much downward vision from a P-C, a straight leading edge Arup shaped wing places the pilot furthest forward. A transparent floor or transparent inboard leading edge could solve the problem, or place the pilot under the diamond wing.
 

Urquiola

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=the methode of anchanced L/D= Oscillating Wing Propulsion...
Nice document. Is this the so called 'Rogallo Wing'? Some had fatal accidents after a dive, when the air blow keeping the 'airfoil' shape and wing working reversed, and lift was no longer provided. The document deserves some work in 'Microsoft Office Picture Manager', or other image editing software, deleting unnecessary shades, changing background color into white, cropping margins,... could reduce weight of document a lot. Blessings +
 
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Urquiola

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You may like the shape of the Airship in attached image, a design, from early in 20th century, by Spanish Artillery Officer Manuel Rivera y Sempere. Handwritten original, 'Sistema de navegacion aerea', is available in CD-ROM from 'Patrimonio Nacional'Sistema de navegación aérea F R S -3 vistas.jpgSistema de navegación aérea F R S -maqueta.jpg Blessings +
 

cluttonfred

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On the visibility questions with the Piana-Canova, I think it's important to remember that even his designs were not pure diamond shapes. One obvious modification would be to compress the area forward wing area and stretch the aft wing area to make a kite shape that follows the 25% chord of the airfoil allowing a straight main spar from wingtip to wingtip. I would also "snip off the points" on all four corners leaving what is in effect something very close to the Zimmerman planform but made with straight lines. Here is a pure diamond (blue) and the 25% chord kite shape (orange) overlaid on the PC.100:

HBA concept sketches (13).jpg

Another approach to the visibility issue might be a pylon-mounted pusher engine behind the cockpit, allowing the cockpit to moved as far forward as possible for maximum visibility with clear leading edge sections if needed.
 
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cluttonfred

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I like that one a lot, but you are going to need a taller fin and rudder. I think you could also get away with simple triangular inverted-taper flaperons like so, which could help prevent tip stall at low speeds by washing out the outer sections of the wings. That has the makings of a fantastically quick and easy aluminum-tube-and-gusset, fabric-covered sport plane.

HBA concept sketches (15).jpg

ss15=super simple 15' span. I don't think visibility to much an issue.View attachment 109578View attachment 109579
 

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Urquiola

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With 3500 mm span, it's still above the upper limit on road, 2490 mm, again, a triplane Bumble Bee may perhaps meet the requirement. Blsessings +
This is my proposal for an improved Bumble Bee, a triplane, more wing area, as for having a decent landing, takeoff and stall speed, still kept wtithin the 249 cm limit to land or drive in roads. Blessings +Boxed Wing Triplane proposal.jpg
 

Riggerrob

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Single-seat version of the dyke delta I'd say. I like it.
The Delta Stingray was an 80% scale based upon the Dyke Delta.
Lowell Borchers devoted 6,000 hours to building it 70% plywood, 20% Douglas Fir with the last 10% being a mixture of fiberglass and metal. It won a designer's award at Oshkosh 1980. Wing span was 15 feet, and length 14 feet. Empty weight was 740 pounds and gross weight 1075 pounds. It was powered by a Continental O-200 engine. Even with only 100 horsepower, it had a top speed of 204 miles per hour, cruised at 180 mph and climbed at 1400 feet per minute.
 
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