Fast glass biplanes

On 18 Nov 2003 07:56 AM, Ben Sego posted the following:
Dave Hyde wrote:

ChuckSlusarczyk wrote:


"when did you ever see birds with their tails where
their beaks oughta be?"


When I drove through a turkey at 65 mph.

Dave 'last thing on his mind' Hyde


I got a chicken at 80 once. The weirdest part was cleaning the egg
off the hood.

B.S.

2 grouse, 1 canada goose, numerous crows, and a seagull.

----------------------------------------------------
Del Rawlins-
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Imagine that you're an air molecule; how do you know if
you're 5' or 10' along the wing? You don't, when the wing comes
along, you just move along the bottom or zip across the top.

Those molecules are smarter than you might expect. G

There can be significant spanwise flow of the air. Like most things in nature
air finds the path of least resistance and sometimes this is not where it was
headed when the wing bounced into it.

Even if you take the same 40 ft high aspect ratio wing, saw it into 2 halves
and manage to attach it to the fuselage with no increase in interference drag
it's going to be less efficient than the 1 long wing - because of the spanwise
flow. Winglets help, flow fences help, joined wing tips help, elliptical
planform helps.

Look up W. Kaspar and his work on tip vortices.

Del Rawlins wrote:
On 18 Nov 2003 07:56 AM, Ben Sego posted the following:

Dave Hyde wrote:


ChuckSlusarczyk wrote:



"when did you ever see birds with their tails where
their beaks oughta be?"


When I drove through a turkey at 65 mph.

Dave 'last thing on his mind' Hyde


I got a chicken at 80 once. The weirdest part was cleaning the egg
off the hood.

B.S.


2 grouse, 1 canada goose, numerous crows, and a seagull.

Gentlemen, I think we have a winner. Or dinner, perhaps, in the case of
the goose...

B.S.

Earlier, (Jay) wrote:

Okay, why don't you start off by
showing me how span comes into the
relationship of air moving over a
wing's airfoil.

That's generally covered in what they call "Theory of Finite Wings."
There's a chapter on it in Abbott and Doenhoff. This Desktop Aero page
is a good introduction to the topic:

http://www.desktopaero.com/appliedae...ingmodels.html

Bob K.

Jay wrote:

Okay, I think you nailed the departure of my logic from yours. I
don't believe that span is in the formula (at least not in high
order).

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

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?

In the lift case, there is *some* easily realizable benefit.
A forward surface like a canard can be used as a big vortex
generator to keep flow attached over the 'main wing' and
increase lift/delay stall. That's why you see a lot of close-coupled
canards on fighters these days.

There's also the trim drag benefit of another surface if
that surface can be configured to reduce the total downforce
required to trim. That's another reason for canards and
relaxed stability airliners. This benefit is usually
not as pronounced as the high AR benefit.

Imagine that you're an air molecule; how do you know if
you're 5' or 10' along the wing? You don't, when the wing comes
along, you just move along the bottom or zip across the top.

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.

I know that the rule of thumb is higher aspect, higher efficiency
(L/D), but this is only part of the story. That rule makes an
assumption of a single wing.

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

Okay, why don't you start off by
showing me how span comes into the relationship of air moving over a
wing's airfoil.

Done and done. Your turn.

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

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

Dave 'misconceptual design' Hyde

On 18 Nov 2003 01:13 PM, Ben Sego posted the following:

2 grouse, 1 canada goose, numerous crows, and a seagull.

Gentlemen, I think we have a winner. Or dinner, perhaps, in the case
of the goose...

Unfortunately in Alaska roadkill belongs to the state and there was
somebody behind me. Up to that point I hadn't committed a crime, but
stopping and throwing it in the back would have been and I know people
who have gotten in trouble with the state fish and game dept. for dumber
things. That goose committed suicide; it and another goose had been
sitting at the edge of the road eating gravel. It's buddy flew away
from the road, and it flew right at my truck.

A few weeks ago I came home to a goose sitting in my front lawn, it let
me take pictures and even video of it before it got up and walked away.
Unfortunately there were too many eyes around. Had he shown the poor
judgement to land in my back yard, his next stop would have been my
freezer. Since I live under the pattern at Merrill Field I could always
claim I was enhancing aviation safety:

http://www.rawlinsbrothers.org/goose.avi

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

In article et, Ben Sego
says...


I don't know if he's the winner but I know he's an "Ace" :-)

Chuck ( one deer,1 pigeon and 1 bike rider) S


When I drove through a turkey at 65 mph.

Dave 'last thing on his mind' Hyde


I got a chicken at 80 once. The weirdest part was cleaning the egg
off the hood.

B.S.


2 grouse, 1 canada goose, numerous crows, and a seagull.

Gentlemen, I think we have a winner. Or dinner, perhaps, in the case of
the goose...

B.S.

"Jay" wrote ...
There was someone that commented that if 2 lifting surfaces made
sense, you'd see the 777 with 2 wings because they're Boeing and have
lots of money and super human engineers. I've worked for lots of
companies like Boeing (but not them because they tried to low ball me)
and they're made up of regular guys like you and me. Many of them
have interests and responsibility outside of designing the best
aircraft ever, and really just want to pay their bills and go home and
have a beer. You work as one guy in a huge machine where decisions
are often made on what's politicaly the best answer rather than what's
technically best. You get one tiny componant of this huge project.
These kinds of organizations often punish risk taking in that there is
no upside pay-off if you're right. But if you're wrong, and it was
because you did something different than before, you get hammered. So
the larger the project, the more conservative the approach tends to
be. Remember, bean counters hate risk of any kind.

Bull****, Jay.

I worked for several years as an engineer in Boeing's Aero Staff.
Everything you just said is wrong. The people that design wings at Boeing
use the best technology available that's consistant with the production
materials that are available. They don't design on the basis of some
political whim. They don't design biplanes because it's easy to show
mathematically that the mutual interference between the circulation of the
two wings decreases the efficiency of both wings.

You seem to have strange theory that just because something isn't done it
must be a good thing to try. Subsonic aerodynamics was well explored by
World War II. 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. If you want do to something different
just to be different go ahead, but it will be an inferior product and
possibly dangerous. 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.

Rich

Well, the seagull was only a probable since I was driving the '59 MG at
the time and not going particularly fast (honest). It hit the headlight
and bounced down the side of the car, so I didn't actually run it over.
For all I know it may have got up and flew away.

Now one of the grouse, on the other hand, was spectacular. I was south
of Delta heading north to Fairbanks, and as I topped a hill there it was
in the middle of the road. I had just enough time to notice it before
it went under, and in my rear view mirror there was just this big
indistinguishible cloud of feathers. I'm just lucky it wasn't a caribou
or a moose. Roadkill in Alaska can be grizzly at times.

Came close to nailing a porcupine a couple summers ago, which normally
destroys the tire. Since I had a full load of fresh Copper River salmon (
read: extremely time sensitive shipment) worth more than the truck on
board at the time, I would not have been amused. His number, which was
11.00-R22 (goodyear unisteel), just wasn't up that night.

On 18 Nov 2003 06:19 PM, ChuckSlusarczyk posted the following:
In article et, Ben
Sego says...

I don't know if he's the winner but I know he's an "Ace" :-)

Chuck ( one deer,1 pigeon and 1 bike rider) S

When I drove through a turkey at 65 mph.

Dave 'last thing on his mind' Hyde


I got a chicken at 80 once. The weirdest part was cleaning the egg
off the hood.


2 grouse, 1 canada goose, numerous crows, and a seagull.

Gentlemen, I think we have a winner. Or dinner, perhaps, in the case
of
the goose...

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

"Richard Isakson" wrote:

You seem to have strange theory that just because something isn't done it
must be a good thing to try. Subsonic aerodynamics was well explored by
World War II. 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. If you want do to something different
just to be different go ahead, but it will be an inferior product and
possibly dangerous. 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.

Rich
+++++++++++++++++++++++++++++++

WoW....
Sometimes, ya just gotta love a posting.


Barnyard BOb - if it's a duck, it's a duck