Japanese plane - shrouded pusher w/winggrids

Hoo-yeah! I love the smell of snake oil in the morning!

Bob K.

Bob Kuykendall wrote:
Hoo-yeah! I love the smell of snake oil in the morning!

Bob K.

Nothing new here. A Sport Aviation article, in the late 80s if I
recall, breathlessly told the story of a C-150 with identical wing tips,
back during days when Jack Cox's articles were uniformly uncritical puff
pieces (not sure if this particular article was written by Cox, it was
just that SA never reported real criticism of homebuilts back then). I
remember it had a fancy stars and stripes paint job. This C-150 had
those venetian blind thingys on the tips plus VGs and fences and was
supposedly capable of impossibly low stall speeds, which to the extent
that stall was reduced would have been a function of the VGs mainly.
The tip 'blinds" just looked ridiculous and speed limiting.

The problem with fancy wingtips is this: If they do anything to extract
benefit from tip vortices, they only do so when the wing is working
hard, at max L/D. So such a device MAY improve rate of climb or sink
rate. It won't have all that much effect on stall speed. At higher
speeds with low AOA they are just drag makers. Who is willing to give
up 15kts of cruise just to get an extra hundred FPM of climb? Thus such
things never appear in the real world in any great quantity.

Note that the only wingtip devices that actually do anything useful are
winglets, which generate some thrust from tip circulation that is more
than their drag, and this only when the wing is at max LD. As a result,
they are only used on two types of a/c in general; gliders and high
altitude cruisers like airliners and bizjets. Both do their thing at
close to max LD, the glider for obvious reasons and the airliner because
at 36000 ft it is operating at cruise effectively in the same indicated
speed regime and AOA as the glider at max LD. In both cases the
winglets are only there because their benefit is available at the
aircraft's intended cruising speed range.

Same applies to any other wing tip device that proposes to use tip
vortice energy.

JohnK

Take a look at some of the papers on the site -

http://www.winggrid.ch/AIAA-2004-2120.pdf
http://www.winggrid.ch/AIAA-2004-2120.pdf

Since they aren't selling anything, and they are doing both real world
experiments and academic papers with plenty of data collection, I
wouldn't call them snake oil.

The effect is real. It may be too mechanically complex to be economic,
but it's more than vaporware.

wrote ...
Take a look at some of the papers on the site -

http://www.winggrid.ch/AIAA-2004-2120.pdf
http://www.winggrid.ch/AIAA-2004-2120.pdf

Since they aren't selling anything, and they are doing both real world
experiments and academic papers with plenty of data collection, I
wouldn't call them snake oil.

Snake oil is far too nice a term for what they're peddling. Did you read
the paper? In the first sentence they throw out a hundred years of
aerodynamics and replace it with their own. Why? Because the old stuff
doesn't give the answers they want. They don't justified it further than
that. They then go on to claim span efficiency factors of 1.5 with their
system. If you understand anything at all about wing aerodynamics you would
know that's an absurdity.

Sometimes people want to believe things so badly that they can't see that
they're leading themselves astray.

Rich

"Richard Isakson" wrote in
:

wrote ...
Take a look at some of the papers on the site -

http://www.winggrid.ch/AIAA-2004-2120.pdf
http://www.winggrid.ch/AIAA-2004-2120.pdf

Since they aren't selling anything, and they are doing both real world
experiments and academic papers with plenty of data collection, I
wouldn't call them snake oil.

Snake oil is far too nice a term for what they're peddling. Did you
read the paper? In the first sentence they throw out a hundred years of
aerodynamics and replace it with their own. Why? Because the old stuff
doesn't give the answers they want.

This Doonesbury is appropriate:

http://www.uclick.com/client/wpc/db/.../05/index.html

Brian
--
http://www.skywise711.com - Lasers, Seismology, Astronomy, Skepticism
Seismic FAQ: http://www.skywise711.com/SeismicFAQ/SeismicFAQ.html
Quake "predictions": http://www.skywise711.com/quakes/EQDB/index.html
Sed quis custodiet ipsos Custodes?

OK.

How are they getting an increase in L/D while decreasing span and
adding drag?

(And before the serious flames begin, neither I nor they are selling
anything.)

Earlier, wrote:

OK.

How are they getting an increase in L/D while decreasing span and
adding drag?

(And before the serious flames begin, neither I nor they are selling
anything.)

The short answer is, they're not. Their verbiage and treatises dance
around it by carefully comparing apples to oranges.

These guys selling snake oil too?

http://www.star-tech-inc.com/papers/aiaa/aiaa.pdf

http://tinyurl.com/g66ln

http://jeb.biologists.org/cgi/reprin...lcode=je xbio

Alsio
SPEDDING, G. R. (1992). The aerodynamics of flight. In Mechanics of
Animal Locomotion (ed. R. McN.
Alexander). Berlin: Springer-Verlag.

SPILLMAN, J. J. (1987). Wing tip sails; progress to date and future
developments. Aeronaut. J. 91,
445-453.

Or did we reach the totality of knowledge on wing tip design with
Whittman's experiment?

wrote ...
How are they getting an increase in L/D while decreasing span and
adding drag?

The only way for this system to do what they claim is they would have to add
energy to the airflow. Perhaps they just forgot to tell us about a small
embedded jet engine.

Rich

Earlier, wrote:

Take a look at some of the papers on the site...

I did. I also chatted about them with one of the aero engineers whose
work is cited in them. We agree that it's a bunch of hokum. It looks
almost like it was designed to spawn a bunch of conspiracy theories
like the ones about GM suppressing the 200 mpg carburator.

As regards the topic of winglets raised by another poster, they're
great for span-limited and bending-moment-limited situations, which is
why they're popular on sailplanes and airliners. L/D-wise it's more
effective to just make the wing longer - that is, a 2-foot span
extension usually increases the performance more than a 2-foot tall
winglet. But of course, extra span drives the wing bending moment up
more, so there are many cases where you can have a winglet but not the
equivalent span extension.