Facet Opel

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Hot Wings

Grumpy Cynic
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Then I amend my idea to mean that the electric motors could be close to the trailing edge
Strictly for visualization purposes:
ducks 2.jpg

The one with the canard was used for examining how to package a hybrid and actually has the same CG location as the Briggs powered one. Though they don't look like it they both have the same thrust angle and offset. 30 inch props (x4) compared to one 54" prop. 8 foot wide center section. The long fuselage is just because I want my eye well forward - just a personal want.
 

EzyBuildWing

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Why doesn't Scotty just put an electric-motor up front on the nose, with a foldable-prop?
Batteries behind the seat.
Very simple structurally.
Alex Strojnik's laminar wing-construction for his S-2 super-smooth Sailplane as detailed in Sport Aviation March 1983 and January 1990 editions, looks very simple, elegant, inexpensive and easily accomplishable in any garage.
Main Spar is simple: Just 2024-T3 angle-flanges bonded to a plywood shear-web.
Plywood ribs are bonded to vertical aluminium-angles which are themselves bonded to the Spar's plywood shear-web.
Wing-skins are fiberglass segments about 3' wide, "pre-molded" to the exact airfoil shape (over a vertical "form"), and then glued to the ribs.
No bolts or rivets anywhere!
And no complicated leading edge. Of course, nowadays, carbon-fiber skins could be used instead of f'glass.
 

Victor Bravo

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2024-T3 angle-flanges bonded to a plywood shear-web.
Plywood ribs bonded to vertical aluminium-angles (snip) bonded to the Spar's plywood shear-web.
Yeah... we need to have a little talk about gluing aluminum to wood, Mr. Strojnik :)

The Strojnik aircraft layout, low-boom configuration, and using laminar shapes to achieve very good performance has been brought into the "present" very very well by the Janowski J-5 and J-6. I did not know Strojnik or Janowski, but I'm pretty sure Strojnik would be very proud to say the J-5 and J-6 are perfect examples of what he was trying to achieve.
 

Sockmonkey

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They don't have to but if you put them up front you'll need bigger tail fins and a more forward CG because any thrust producer acts like an empenage. Pushers increase power on stability (both in pitch and yaw), tractors decrease it.
I did not know this. It's counter intuitive as I would have assumed the opposite.
Why does it work that way?
 

Hot Wings

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Norman

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rotax618

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I was fortunate enough to be at Evans Head airfield when Scott Winton was attempting his altitude records many years ago. The first thing the Facet Opel reminded me of was my control line combat flying wing models, which could loop in their own length. When Scott took off the aircraft appeared to oscillate in pitch until he gained control, Scott was a very accomplished pilot.
I suggest if anyone is contemplating re-designing the Fact Opel that they engineer more longitudinal stability into it or possibly suffer the same consequences with over pitching at speed.
 

Sockmonkey

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If it were a pure thrust vector like the we see in Statics class...... But the real world isn't as neat. About halfway down the page is a reasonable explanation:

https://www.quora.com/Do-puller-type-propeller-aircraft-have-more-static-stability-than-pusher-type-If-so-why
Ohhh, I get it now. Thank you.
I mistakenly thought the tractor prop would prevent the yaw in the first place rather than exacerbating any yaw that happened.
This puts my view of pushers in a new light.
 

lr27

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Yeah... we need to have a little talk about gluing aluminum to wood, Mr. Strojnik :)

The Strojnik aircraft layout, low-boom configuration, and using laminar shapes to achieve very good performance has been brought into the "present" very very well by the Janowski J-5 and J-6. I did not know Strojnik or Janowski, but I'm pretty sure Strojnik would be very proud to say the J-5 and J-6 are perfect examples of what he was trying to achieve.
In his books, Strojnik makes gluing to aluminum sound pretty scary, but it's probably better to glue wood on it than another piece of aluminum. I'm not sure it's something I'd want to try. It would be nice if you could get aluminum with a thin layer of something already reliably glued to it. A quick stroll through the internet indicates a lot of work going on about bonding aluminum. So it's possible they've come up with something better since Strojnik. I wonder if a gazillion fasteners could do the job without too much of a weight penalty? Of course, there's always "black aluminum" (hides under desk). ;-)
 

Vigilant1

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Thanks, that saved me some typing. I might add though that jets also develop side forces at the intake lip. That's probably why you don't see jets with the intake on the nose anymore.
That real estate on the nose is too important to be used for jet intakes--it is needed now for the radar.
 
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Sockmonkey

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In light of what I've just learned, an electric pusher plank with the motor on a slight fuselage extension could exploit that stabilizing effect pretty well and be easier to balance by sticking the heavy battery pack in the nose so the variable pilot weight can be closer to the COL/CG.
 

EzyBuildWing

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Alex Strojnik's wing-skins construction might be applicable to the Plank. Carbon-fiber could be substituted for fiber-glass :
...put a layer of epoxy on a mirror-smooth Plexiglass surface and cover it with a first-layer of fiber glass. Just before the first-layer matrix has cured, the second and third layer follow. Before the last 2 layers have cured, all 3 layers are lifted from the Plexiglass and draped over a small, upright precisely made positive airfoil "mold" and pressed against it. After fully curing, an accurate and light "skin" with a mirror-smooth outer-surface is lifted off the mold. ....the nose-ribs are installed(are glued) inside the skins BEFORE the skins go(are glued) onto the wing.
 

rotax618

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From what I understood, Strojnik layed the glass on mylar sheets and before they cured hung the sheets up by two opposite edges, producing the airfoil shape.
 

lr27

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The sheets, with weighted edges, were placed over a male form that was airfoil shaped.

a10285617-242-StrojnikIllustration01.png
 

lr27

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I meant the fiberglass sheets, partially cured, if that wasn't clear.
 

Victor Bravo

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All that stretching and mylar and weights and clamps is antique ideas now... it has all been rendered obsolete.

Today they would hot wire the wing shape out of foam, cover it in several layers of composite, lay mylar sheets onto the outside of the composite, then pack the assembly back into the foam "beds" that the cores were cut from, put the whole thing into a large vacuum bag, weight it down with a thousand pounds of sandbags, and pull vacuum on it until it is cured.

And that's the simple "solid core" version instead of the "sandwich" version.
 

jedi

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All that stretching and mylar and weights and clamps is antique ideas now... it has all been rendered obsolete.

Today they would hot wire the wing shape out of foam, cover it in several layers of composite, lay mylar sheets onto the outside of the composite, then pack the assembly back into the foam "beds" that the cores were cut from, put the whole thing into a large vacuum bag, weight it down with a thousand pounds of sandbags, and pull vacuum on it until it is cured.

And that's the simple "solid core" version instead of the "sandwich" version.
VB. Good start but you missed the part where one more wire cut will remove much of the solid core and save a bunch of weight. Then you could slice the removed core and bond the ribs back in with or without a cap strip.

An alternative that works quite well is to lay up the foam and skin on a flat work table then bend as in post #355 for a light LE sheet of a ribbed D Tube spar. A really light weight construction would combine the two systems with a little more work.

If anyone wants more details, contact me.
 

Jay Kempf

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Been stuck in my head lately so I did a more in depth dimensional study of what it would come out like if you updated the Facet Opal and made it a practical cruiser. Came out like this. Wing almost identical, with a few inches of extra chord and 22' even for span 13.5% version of the same NACA 66-1-212 at 3° incidence and 6° reflex at .8C . Bottom pan of fuselage almost identical to the original. Upper fuselage shell sized for comfort, roll over protection and visibility as well as baggage and lots of 4 stroke engine choices like C85/0200 VW and other water cooled options. Gear much wider with real tires. This view is conventional tri gear. Another option is a tall main nose gear and short fixed panted mains on the bottom of the fins so the takeoff angle is built in. Retract the nose for easy ingress in that config. Mains are spaced at 6' track. This could be stretched about 2.5-3' and be a two place tandem with the second seat on the CG. Pod is 11' nose to spinner so very small to mold parts. Outer wings split at say 7' would be 7.5 long each and 65" chord. Probably could be folded or rigged by one human easily as an option. Bottom fuselage pan could have wheel wells molded in in one piece.
1589408827222.png
1589408936696.png
 
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