Fast glass biplanes

Dave Hyde wrote in message
The generally accepted definition of the induced drag coefficient
is:

CDi=CL^2/pi/e/AR,
where CL is the wing lift coefficient at the conditions under
consideration,
pi=3.14159...
e = Oswald's efficiency factor (typically 0.8 or so)
AR = aspect ratio

Okay, thanks for all that, I think you're missing some parentheses in
there because I'm getting a quad decker formula. I always love those
formulas with a constant that has some guys name that was alive in the
last 100 years.

The _definition_ of aspect ratio is chord/span, or span^2/aero (they're
equivalent), so as area remains the same but aspect ratio increases,
induced drag decreases by 1/span^2. That's what I call a primary
effector.
If you add wing treatments like winglets, fences, etc, you can increase
the
effective AR, but the big effects are gained by working at the tips,
not across the span, as another wing typically does.

Look at the lift side. The formula becomes messier, but for a finite
wing:

CL,finite ~= CL,infinite*(1/(1+(dCL,inf/daoa)/pi/AR))

As span increases through increased aspect ratio, the finite
wing lift coefficient gets closer to the infinite wing CL.

Can we agree that this is a good thing?

Okay I'm looking at things in the infinite wing theory where the
effects due to tip/root disturbance are very small compared to the
rest of the span. So with this theoretical wing of aspect approaching
zero, 2 non-interfering wings of half span, would be essentially the
same lift and drag as one.

Perhaps this is really a discussion of how large an effect the
root/tip distubance is for a practical wing (e.g. 30' span). You'd
pointed out that proper tip treatment can help make the shorter wing
behave as if it is part of an infinite span. Seems like a fence at
the tip would be the way to go to keep the high pressure air from
spilling over into the low pressure region.

Um...you might want to review some finite wing theory.
There can be quite a bit of spanwise flow at the root _or_
the tip. When subsonic you make a bow wake. The air is moving
before you hit it, and it's not just front-to-back.

Looks like the issue is I'm talking about this theoretical wing and
you're talking about a practical one. You know, in theory, practice
and theory are the same, but in practice, they are very different. =^)

That's not a rule of thumb, that's physics. All other things being
equal, the highger AR wing *will* have less drag.

I'm talking about 2 wings that have an aspect approaching zero, versus
a single wing with aspect approaching zero as well. So the lift and
drag per foot of wing are essentially the same.

Done and done. Your turn.

I've worked for lots of companies like Boeing...

Have you ever worked in conceptual design and/or
aerodynamics?

Not of aircraft, have you? The closest thing I've done and got payed
for was the work I did on a DARPA program called FLASH. I was working
on the ailerons of the Dryden F/A-18 they were torturing.

Most of your risk aversion comments
were way off the mark. A trip to the Air Force museum
to see the Bird of Prey or the X-36 could be illuminating.

Most if not all of those X planes were R&D payed for by the you and
me, the tax payers of America. Its extremely rare for a large company
to take a "flyer" with their own money and reach very far forward.

Dave 'misconceptual design' Hyde

On 19 Nov 2003 08:19 AM, Corky Scott posted the following:

I went to the Lionheart website to have a look. There was a section
that listed testimonials. Among those testimonials was one from none
other than Jim Campbell, he liked it...

No doubt he looped, rolled, and spun it.

----------------------------------------------------
Del Rawlins-
Remove _kills_spammers_ to reply via email.
Unofficial Bearhawk FAQ website:
http://www.rawlinsbrothers.org/bhfaq/

"Jay" wrote in message
om...

Subsonic aerodynamics was well explored by
World War II.

Ya, and we know what kind of advanced tools they had at their disposal
during that time. I think their computer was a group of ladies in a
room with adding machines.

That was at Los Alamos, NM. Not related to aerodynamics.

Jay wrote:

Okay, thanks for all that, I think you're missing some parentheses in
there because I'm getting a quad decker formula.

The formula is correct as written.

So with this theoretical wing of aspect approaching zero,
2 non-interfering wings of half span, would be essentially the
same lift and drag as one.

I think you have a fundamental misunderstanding of the basics here.
An infinte (span) wing has an aspect ratio of INFINITY, not zero.
LARGER aspect ratio is less drag.
Again, to make a successful break from the mouse-maze, you've
either got to have a sound grasp of the fundamentals or be
very lucky. Counting on luck does not instill confidence
(but sometimes produces interesting threads).

Most if not all of those X planes were R&D payed for by the you and
me, the tax payers of America. Its extremely rare for a large company
to take a "flyer" with their own money and reach very far forward.

Who pays is irrelevant. There have been and will continue to
be radical departures from the 'box' even by giants in the aerospace
industry. The simple fact that you are not aware of them does not
mean that they do not exist.

Dave 'to infinity...and beyond' Hyde

Jay wrote:

*sigh*

Instead of running numbers on Excel with formulas filled with fudge
factors from experimental data taken 70 years ago, I think I'm going
to throw some wings on my FEA computer model and let the computer take
care of the algebra at 2.4GHz.

I give up. Good luck, and please post or publish your results
when you're done. The world awaits.

Dave 'Pontius Pilot' Hyde

In article .net, Ben Sego
says...


I went to the Lionheart website to have a look. There was a section
that listed testimonials. Among those testimonials was one from none
other than Jim Campbell, he liked it...

Corky Scott

Well, I'm sold then!

He likes anything that he thinks will lead to some ad money :-) He only stops
liking them when they stop the ads. zoom likes it and jaun will probably rebuild
it .....but never fly it. LOL!!!

Chuck(believer in 70 year old data) S

Earlier, Jay wrote:

...So with this theoretical wing
of aspect approaching zero, 2 non-
interfering wings of half span,
would be essentially the same
lift and drag as one...

The same drag as one very ineffecient wing, that is. So as L/D 0, it
starts to not matter as much whether you've got a monoplane or a
venetian blind.

And please, nobody ask how you make a venetian blind. I do remember
when 16Kb was the size of a gym locker. BTDT, still got some of the
core beads.

On a slightly different topic: Jay, when I was pointing you towards
joined-wing concepts in the earlier thread and also in private email,
I really wasn't trying to be snarky. I was trying to point out a
configuration that:

* Suggests a practical application for something like a biplane
configuration

* Has been studied enough to suggest that it offers, in theory at
least, some advantages over other configurations

* Is not well explored in physical hardware (NASA canceled their
proof-of-concept aircraft and put the AD-1 it was based on in the
Hiller museum)

* Would look relatively cool and unusual

Thanks, and best regards to all

Bob K.

Dave Hyde wrote:

I think you have a fundamental misunderstanding of the basics here.
An infinte (span) wing has an aspect ratio of INFINITY, not zero.
LARGER aspect ratio is less drag.
Dave, to be fair to Jay, you did type

:The _definition_ of aspect ratio is chord/span

Of course, you immediately contradicted that by typing

r span^2/aero (they're equivalent)

which should have clued anyone in that you had inverted the first
expression.

--
Alex
Make the obvious change in the return address to reply by email.

(Jay) wrote:

"Richard Isakson" wrote in message Bull****, Jay.

You seem to have strange theory that just because something isn't done it
must be a good thing to try.

No, the theory is just because someone else hasn't been able to do it
right, doesn't mean it won't ever work. Give yourself some credit.
Its happened before.

Subsonic aerodynamics was well explored by
World War II.

Ya, and we know what kind of advanced tools they had at their disposal
during that time. I think their computer was a group of ladies in a
room with adding machines.

Much of transonic and supersonic flow was understood shortly
after. If you think that you've come up with something new that just means
you don't understand why thinks work.

When the Wright brothers came up with this idea of heavier than air
powered flight didn't mean they just didn't understand how things
worked. If they'd listened to the early 1900's version of people with
that attitude, we'd be celebrating some French guy inventing powered
flight. They had intuition that they may be something there, and
didn't give up just because lots of other people had failed.

It's funny, but I think you are both right. One beauty of experimental
aviation is the "experimental" part and the ability to break the mold.
But I'd also bet that 99 44/100% (conservative estimate) of the time
that well-established practice is forsaken, the builder finds out why
that practice was well established in the first place. And an
uninformed outsider's opinion of the engineering dome by professionals
on a project like an airliner is laughable at best. Somehow, I suspect
that Boeing knew quite a bit about composites 30 years ago, and I am
glad that the planes I fly on now that were designed at that time do
not have hot-wire cut foam wings g. Richard: I think it is good for
someone like Jay to come along and use his creativity to challenge
conventional thought. Jay: Remember that if you want to analogize what
you are doing here to the Wright Bros, they did a hell of a lot of
engineering and experimentation, not just out-of-the-box thinking.

Your current design has at least three fatal flaws.
You need to open some books and understand the theory of flight before you
start designing airplanes.

Instead of running numbers on Excel with formulas filled with fudge
factors from experimental data taken 70 years ago, I think I'm going
to throw some wings on my FEA computer model and let the computer take
care of the algebra at 2.4GHz.
Now THAT is scary. Someone who thinks a computer model is a substitute
for learning fundamentals (and is impressed by the speed if his PC's
processorVBG) is a huge danger to himself. If you do get into the
build mode, I hope you will try out your ideas on an RC model first.

--
Alex
Make the obvious change in the return address to reply by email.

Felger Carbon wrote:
That was at Los Alamos, NM. Not related to aerodynamics.

NACA and its successor, NASA, used "group[s] of ladies in a
room". The title for that job was "Computer." That work was most
definitely related to aerodynamics.

Here's a quote from the book "Engineer in Charge," subtitled "A History
of the Langley Aeronautical Laboratory, 1917-1958":

--start of quote--
As the test began, two researchers peered through small glass portals in
the side of the tank, operating a signal system that triggered different
lights as the airspeed became constant or when a problem arose. These
men called out their readings of the balance scales to a recorder who
simultaneously read aloud, from his panel of instruments, tank pressure
and temperature of the manometer liquid. For scale-effect comparisons,
the VDT staff made the tests at a constant airspeed (approximately 50
miles per hour) and at five different tank pressures (Usually 1, 2.5, 5,
10, and 20 atomospheres) and then tested airfoils of closely related
characteristics at 20 atomospheres only. Modifying a particular feature
of a model while keeping all its other characteristics constant enabled
the staff to compare the aerodynamic effects on each new shape with
those on the original. When all the necessary readings had been taken,
someone shut the drive motor off and opened a blow-off valve which
released the pressurized air. The calculation, plotting, and final
processing of data took weeks. "Computers" existed in those days--but
being human, they had to eat lunch, and wanted coffee breaks!
--end of quote--

This particular paragraph concerns work done in the Variable Density
Tunnel which began operation in 1922.

B.S.