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The 'daydreamers' thread...post your craziest designs and concepts here

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Riggerrob

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Dear Topaz and Cluttonfred,
I have sketched a dozen variations of Richard Voss's asymmetric airplanes.
One of my first design criteria is separating the propeller arc from the cockpit. I insisted on installing rudder-pedals 8 to 18 inches (50 cm) aft of the propeller disc to prevent thrown propeller blades from amputating the pilot's feet. Note that FAA certification standards forbid installing crew seats in line with prop discs.
So my design concept starts with fixing the distance between the prop disc and rudder pedals, then sliding components fore and aft until they balance.
In the case of a BV 141 replica, I started by leaning the pilot's shoulders against the main spar, then positioning the propeller a bit forward of his feet (SAE 95 the percentile male), then doing preliminary balance calculations.

Secondly, single-engined pushers are always difficult to balance. By the time you position the propeller aft of the wings' trailing edge, your centre-of-gravity is a long way aft of optimal. You could regain balance by moving the pilot farther forward, but that creates a long and heavy cockpit structure.
The other problem with pushers is streamlining the aft end of the passenger cabin.
For smoothest airflow, fuselage walls are ideally parallel across the wing root, then taper at 2 or 3 to 1 until they converge at the propeller. This need for streamlining clashes with engine balance.
Seabee solved that problem with an extension shaft, but we all know that the longer the drive train, the more likely it is to suffer torsional vibration problems.
David Thruston's first light flying boat was the Grumman Tadpole with the engine (on a short pylon) raised a bit above the mid-wing. The aft fuselage was cutaway to allow the bottom propeller blade to spin close to the waterline. Note Thurston only designed one plane with that configuration. All his later flying boats (Colonial Skimmer, Lake Buccanneer, Teal and Seafire) used pylons to mount engines well above the wing, where they were easier to balance (fore and aft) because they did not have to worry about prop blades hitting the wing, or wing wake confusing airflow into the propeller. The disadvantage is that Thurston's airplanes suffer major trim changes when you change thrust.

In the short run (please pardon my pun) the simplest drive train is short.
In the long run, light-weght electric motors will be positioned anywhere it is convenient to mount propellers, with few balance problems.
 

DreamersE/AB

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Well as long as we're daydreaming.... how about a flying replica of the SA-43 Hammerhead from the mid-90's TV show "Space: Above and Beyond"? Couple of Wankel 3-rotor rotary's driving ducted fans.... with afterburners. Fun!
SA-43 Hammerhead.jpg
 

egoman

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Feb 2, 2020
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A mashup of a Cessna 150 taildragger with a widened cockpit for larger passengers and a super-cub style wing. Yamaha powered with a turbo making about 220hp. Did I mention it should all be a composite of CF and Kevlar laid out into two bolt together 1/2s? Assembly would be all line up bolts and epoxy glues so it could be assembled like a model kit. Sprint car front wheels with those hubs and brakes and wheels with composite springs at both ends. Stick controls as opposed to yokes. Thinking push pull cables for all axis controls.
NOT that I have given this much thought though!
 

rbarnes

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Something like that already exists.
well of course the DoubleEnder already exist, hence the inspiration. I dont think anything quite like what is pictured exist though.
It's a shame the DoubleEnder project has gone quiet for years now.
 
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bmcj

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To my mind, the question of putting the pilot and passenger(s) in a pod vs. putting the engine in a nacelle in an asymmetric comes down to relative mass...

...Keeping in mind that every aircraft is vertically asymmetric...
Well then, instead of putting the engine on a pylon, why not build a simple, skinny plane (maybe something that looks like the plane from ‘Flight of the Phoenix’) and then place the crew in a plexiglass pod mounted on a pylon above the wing for max visibility? 😂
 
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rbarnes

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You know this might just work. I left the tail in exact same place as the original CH750-SD has them at. Then drew booms out to it off the wing. The rear engine would weigh 220lbs and be located right over the area where Zenith currently says it is fine to load 250lbs of shtuf right now. I wonder what kind of reinforcing the wing spar would need to take the twisting motion imparted by the tail booms ?

TWINSTOL750_3.jpg
 

cluttonfred

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It certainly could work and might make for a great plane, but you have to keep in mind the scale of the undertaking. While you might be able to reuse some components, you'd essentially need to re-design the wings, fuselage , horizontal stab, and control runs as well as creat a second engine installation and, of course, the two booms. It's not a trivial change like tweaking the shape of a rudder.

You know this might just work. I left the tail in exact same place as the original CH750-SD has them at. Then drew booms out to it off the wing. The rear engine would weigh 220lbs and be located right over the area where Zenith currently says it is fine to load 250lbs of shtuf right now. I wonder what kind of reinforcing the wing spar would need to take the twisting motion imparted by the tail booms ?

View attachment 103665
 

Tiger Tim

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It certainly could work and might make for a great plane, but you have to keep in mind the scale of the undertaking. While you might be able to reuse some components, you'd essentially need to re-design the wings, fuselage , horizontal stab, and control runs as well as creat a second engine installation and, of course, the two booms. It's not a trivial change like tweaking the shape of a rudder.
Almost seems like it would be easier to start with a pusher and add an engine to the front...
 

cluttonfred

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Or a high-powered tractor single and give it two smaller engines like a Dornier Do-28. Zenith says the CH801 can take up to 220 hp and up 400 lb installed engine weight. A pair of Suzuki G13 or G15 conversions could work nicely and the view over the nose on final would be great.



Almost seems like it would be easier to start with a pusher and add an engine to the front...
 

rbarnes

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I was thinking of this guy.
Yeah, the DoubleEnder has gone dark for like 5 years now. No updates to his website and no new videos.


It certainly could work and might make for a great plane, but you have to keep in mind the scale of the undertaking. While you might be able to reuse some components, you'd essentially need to re-design the wings, fuselage , horizontal stab, and control runs as well as creat a second engine installation and, of course, the two booms. It's not a trivial change like tweaking the shape of a rudder.
We are in the day dream post..... I like the idea because yes it would take a lot of engineering, but you could reuse a LOT of the CH 750-SD parts. Wing ribs and skins, flaperons, slats, forward half the fuselage, doors, windshield, landing gear, horizontal tail ribs, and maybe use a pair of 750Cruzer vertical tails on the booms. Much of the control runs to like the flaperons wouldn't change.
 

Bill-Higdon

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Or a high-powered tractor single and give it two smaller engines like a Dornier Do-28. Zenith says the CH801 can take up to 220 hp and up 400 lb installed engine weight. A pair of Suzuki G13 or G15 conversions could work nicely and the view over the nose on final would be great.

I remember some of this birds earlier relatives operating out of a UA Army strip in S.E. Asia back in the 69-70 time frame
 

xwing

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Years ago for whatever reason, thought to myself why not make/use an elevator to get stuff up in earth orbit..
 
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