[Turtle]

Originally Posted by Pyrotex

Well... yes.
Mississippi State University, back in the 70's I think, built such a plane.
It had two engines, one on each wing. The wings themselves came straight out of the fusilage, then curved in a semi-circle (down and then up) and ended in a second straight section at the tips.

The engines were mounted at the axis of the semi-circular wing sections, and each had a propeller that pushed all its air "through" the semi-circular wing section.

With engines revved to max, about ~90% of plane's weight was gone. The plane only needed to move forward at about ~40 mph to take off.

Can't find a picture online. And all numbers are guesstimates.

Is this it? Fly me to the Moon...
Mississippi State University XAZ-1

Mississippi State University XV-11A Marvel

Mississippi State University XV-11A Marvel

PS Found some more pictures, but they are all the single engine deal. Perhaps the twin-engine job was black-ops and that's why we can't find photos?
XV-11A Marvel

[Turtle]

Originally Posted by CraigD

Some unsolicited suggestions and ideas for folk experimenting with air flows:

• Terminology-wise, a device to assure that all of the air in a wind tunnel is moving in more-or-less the same direction is called a collimator (its use in aerodynamics is less common than in optics). “Laminar” (“layered”) refers to air moving at different speeds in the same direction remaining parallel. ...
• Square or hexagonal grids made of paper, plastic, metal, or thin wood are, I think, better for a wind collimator than packed together straws. I suspect you’re getting some pretty complicated turbulence from those straws.
• A Mythbusters episode demonstrated blowing out flames (ultimately a big gas flame) with little rubber diaphragms and loudspeakers.

Collimator it is.

The (only) other cross-sectional shape that tiles the plane regularly is the equilateral triangle. Keeping all else constant in the experiment, the collimator alone suggests dozens if not hundreds of experiments wherin the cross-sectional shape is altered, the relative size of those shapes (small vs. large), the length of the collimator, and the distance the collimator is positioned away from the fan.

The Mythbusters are chuckle-heads I wouldn't trust to light a match.

[CraigD]

Originally Posted by arkain101

I wondered, if a person was do build a design correctly to create a plante that flies itself.

Lift is created by gaining speed through the air to create motion etc, and allow the air to pass over the wing structure to create the lifting effect etc...
Now, if one was to build such a plane where the engines were located in such a posistin that they provided substantial thrust of air over the fusilage even while the plane/flying machine was at rest relative to the ground, would it, could it fly, and even maybe hover?
…
Whats the thoughts on this wild idea lol.

Though wild, this is far from a new idea – such designs appear to predate the first successful powered aircraft in the early 20th century!

There are whole classes of aircraft that direct their prop (or jet) wash over their wings to shorten their takeoff distances. To some extent, nearly all high-performance STOL aircraft use the approach, typically with unusually large wing flaps near their props (the de Havilland Twin Otter likely having logged the most passenger-miles)

For sheer wild-looking-ness, my favorite class are the “deflected slipstream” variety, some of which were so extreme that they were actually capable of vertical takeoff. This paper (1 MB PDF) has a better history than any I’ve read before, and lots of diagrams and photos.

The success of the Rolls Royce jet VTOL aircraft, culminating in the famous Harrier, pretty much put an end to serious interest in this approach, though it figures in moderation into the design of many modern light and light commercial airplanes. Later lift fan designs like the F-35 go even further away from the “driving engine as lifting engine” approach.

Originally Posted by arkain101

Now, if one was to build such a plane where the engines were located in such a posistin that they provided substantial thrust of air over the fusilage even while the plane/flying machine was at rest relative to the ground, would it, could it fly, and even maybe hover?

As a question of practical aerodynamics, I don’t think this is possible, because if you built an airplane able to generate enough airflow over its wings while standing still on the ground, the resulting forward thrust would be so great that it would be impossible to prevent it from accelerating forward once its landing gear left the ground. You could angle it upward to prevent any forward motion, but at this point you’re describing essentially a tailsitter VTOL, which doesn’t require lifting wings at all.

No mention of tailsitters would be complete without a decent reference to the almost-built-in-1945 Focke-Wulf Triebflügel, IMHO the wildest-looking seriously designed airplane ever.

[InfiniteNow]

Originally Posted by Pyrotex

It had two engines, one on each wing. The wings themselves came straight out of the fusilage, then curved in a semi-circle (down and then up) and ended in a second straight section at the tips.

The engines were mounted at the axis of the semi-circular wing sections, and each had a propeller that pushed all its air "through" the semi-circular wing section.

Sounds a bit like the condor:





If not, you could always check here:

Raspet Flight Research Laboratory

[Pyrotex]

Well, guys, I searched and searched for the twin-engine STOL that I saw in a college newsletter back when I was going to school at MSU. Can't find a trace. The single engine version graciously provided by Turtle is, I believe, a successor to the clunky version I remember. Thanks.

[Turtle]

Originally Posted by Pyrotex

Well, guys, I searched and searched for the twin-engine STOL that I saw in a college newsletter back when I was going to school at MSU. Can't find a trace. The single engine version graciously provided by Turtle is, I believe, a successor to the clunky version I remember. Thanks.

Road trip to MSU Library? In the looking I did to find the Marvel, I found that it not only used the ducted fan, but the wing tops had active suction holes that smoothed the flow over the wing at low speed for greater lift. The ol' reverse air hockey technique.

Here's one of my favorite odd ball aerodynamic designs: >> Forward-Swept Wings

Meantime, the work on my collimating duct is going fine but slow. Because I started laying up in rings from the outside in, the pattern is neither type of close packing of cylinders, but a combination. I have 3 rings done, and I am counting as I go so I can get the total at the end without the madness of all those circles. Here's the duct now from the fan side.

[Pyrotex]

Just make sure you keep all your ducts in a row.

Pyro

[Turtle]

Originally Posted by Pyrotex

Just make sure you keep all your ducts in a row.

Pyro

Roger that.

I have been saving the straws for months, and it's looking like I have too few. I have 59 in the first ring, 53 in the second, and 48 in the third: total 160. I'll use what I have and make another test run on the candle.

Here's a drawing of the water version I made. I packed the straws friction tight & without glue, and so they tended to shift around.

[Turtle]

Ring #4 complete: 42 straws: 2 monkeys

Average straw diameter is 9/32".

[Turtle]

I have run out of straws, just a few short of completing the 5th ring of collimators. No worries; I'll just hurry up & slow down until I get more.

Here's the test run of the duct on the fan blowing out the test candle. I measured the maximum distance at 6.5 feet; better than the empty duct, not as good as the fan alone. Notice the change in sound from the other runs.

YouTube - Laminar Flow Experiment - 5 Collimator...