Aviation's Biggest Paradox

[rscwhite]

Hi Guys,

If we can attach a 35hp engine to an ultralight fixed wing and get off the ground, why can't we use that same 35hp engine to blow air over a wing in some fashion and take off vertically?

Scot White

 

[hillberg]

Keep the gross weight under 300 lbs and disk loading down, and try.$$$$$$$$$$

 

[rscwhite]

OK, that made no sense to me at all!

Someone else wanna try?

 

[DennisFetters]

Hi Guys,

If we can attach a 35hp engine to an ultralight fixed wing and get off the ground, why can't we use that same 35hp engine to blow air over a wing in some fashion and take off vertically?

Scot White

That has been done. The problem is always the same; Controlling the aircraft. By the time you create some complex control mechanism that will vector the air for control, it is always too heavy to fly with a pilot.

So... Add more horsepower.... but, that IS the paradox. More horsepower, more structure needed to contain the horsepower = more weight, which means larger control mechanism, so more horsepower needed, which = more weight, which means larger control mechanism, so more horsepower needed, which means larger control mechanism, so more horsepower needed, which = more weight, which means larger control mechanism, so more horsepower needed, which means larger control mechanism, so more horsepower needed, which = more weight, which means larger control mechanism, so more horsepower needed, which means larger control mechanism, so more horsepower needed, which = more weight, which means larger control mechanism, so more horsepower needed, which means larger control mechanism, so more horsepower needed, which = more weight, which means larger control mechanism, so more horsepower needed, which means larger control mechanism, so more horsepower needed, which = more weight, which means larger control mechanism, so more horsepower needed, which means larger control mechanism, so more horsepower needed, which = more weight, which means larger control mechanism, so more horsepower needed, which means larger control mechanism, so more horsepower needed, which = more weight, which means larger control mechanism, so more horsepower needed, which means larger control mechanism, so more horsepower needed, which = more weight, which means larger control mechanism, so more horsepower needed, which means larger control mechanism, so more horsepower needed, which = more weight, which means larger control mechanism, so more horsepower needed, which means larger control mechanism, so more horsepower needed, which = more weight, which means larger control mechanism, so more horsepower needed, which means larger control mechanism, so more horsepower needed, which = more weight, which means larger control mechanism, so more horsepower needed, which means larger control mechanism, so more horsepower needed, which = more weight, which means larger control mechanism, so more horsepower needed, which means larger control mechanism, so more horsepower needed, which = more weight, which means larger control mechanism, so more horsepower needed....

That's my point.

 

[rscwhite]

Haa funny Dennis but that's just not so. It's never been done.

All you get is action-reaction (Newtons 3rd) off the bottom of the wing and it will always take more HP to do that. What I'm speaking of is lift in the Prandtl lifting line sense... creating lift by moving air across the top of the wing.

Scot

 

[DennisFetters]

Haa funny Dennis but that's just not so. It's never been done.

All you get is action-reaction (Newtons 3rd) off the bottom of the wing and it will always take more HP to do that. What I'm speaking of is lift in the Prandtl lifting line sense... creating lift by moving air across the top of the wing.

Scot

I was talking about the Prandtl effect too;

http://discaircraft.greyfalcon.us/Achenbach.htm

Anyway, Same answer. If you want to hover you need control. Using a Prandtl lifting line will hardly hover on its own. You add sufficient contrail mechanisms and its too heavy in impractical.

 

[rscwhite]

Dennis,

I can think of several lightweight/simple control mechanisms. If you can get a wing to lift by blowing air over the surface with the same lift as a wing moving through the air using the equivalent HP you are a #%*@*)## genius and you should develop it.

Scot

 

[DennisFetters]

Dennis,

I can think of several lightweight/simple control mechanisms. If you can get a wing to lift by blowing air over the surface with the same lift as a wing moving through the air using the equivalent HP you are a #%*@*)## genius and you should develop it.

Scot

Maybe not a genius, but I feel that I'm experienced and smart enough to know it's not worth while for me to pursue. It's just not my cup of tee.

You may look at something and say "wow, that would sure be cool to develop", while I look at it and say "how many unforeseen problems will this be, and is it worth the money, effort and years of my life... if it could be done at all..... and how many unforeseen ways can a customer find to screw it up after I build them??!!!".

 

[JAL]

How do you propose to blow air over a wing that is 30 square feet or more that is typical of ultralight with a very light wing loading from a 35HP engine. You would need a fan the width of the wing how do you engineer that and keep it under ultralight weight. And because the prop would have such big diameter it would have to sit 10 feet off the ground and can only rotate a few hundred revolutions a minute or it will go supersonic.

They do it with very short wings where air is accelerated 100's MPH so that the small wing area can provide enough lift to carry the weight (e.g ducted fans). They usually use engine with many hundreds of horsepower or even turbines to achieve this though.

Also it is not safe system, in the event of engine failure there is no option to auto rotate or glide when descending or ascending vertically near the ground.

 

[brett s]

And now maybe you'll understand why helicopters came about.

 

[dragonflyerthom]

Ducted fans, hydrogen peroxide jets could work but you still won't hover. A lot of reay smart people have been working on this. Complex head and torque will vet you every time.

 

[WaspAir]

35hp blown at a kite on a well-chosen string length could give you a hover.

 

[flightrisk]

Hi Guys,

If we can attach a 35hp engine to an ultralight fixed wing and get off the ground, why can't we use that same 35hp engine to blow air over a wing in some fashion and take off vertically?

Scot White

Well it would require more than a 35hp engine, but something similar to what you're talking about can be done, only the air is blown over and against the wing... it's called a deflected slipstream aircraft. Essentially it is a fixed wing aircraft with huge (retractable) flaps that deflect the propeller slipstream ninety degrees, enabling a vertical take-off. Several models of this type of aircraft were built in the late 1950's - early 1960's. Certain control, stability, and other important issues were never adequately resolved. A researcher named Dr. William Bertelsen seems to be the only person (based on published information, anyway) who continued R&D on this type of design. He claims to have worked out the issues that plagued previous attempts with his Arc Wing design.

I've attached photos of the Ryan VZ-3 Vertiplane.

 

[dineshkkk]

Some good thinking behind this STOL and probably a VTOL on this new development "Fan Wing"
http://www.fanwing.com/index.htm

 

[Resasi]

That is fascinating.

Pretty it is not, and based on a very old idea, but seems to work extremely well.

 

[Rotor Rooter]

To look at it from a different perspective;

All of man's 'innovative' advancements are simply progressions on what nature has innovated earlier; by trial and error. [survival of the fittest]. Advancements can be vertical flight in a balloon by understanding nature thermal currents, to atomic bombs by understanding the Sun.

When it comes to moving within an environment, bilateral symmetry and lift that is perpendicular to the lifting body are survivors.


Here is the answer to your quest.
Rotor & Wing & Everything

 

[Walter]

Lift comes from the force generated by accelerating air downwards, even in a FW (otherwise FW could not fly inverted). So accelerating air directly downwards, like in a helicopter, is more practical. My 2 cents ...