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Message list:
1. RE: [COUPERS-FLYIN] Re: Flyboys (Tri-Plane Question)
2. [COUPERS-FLYIN] FLYBOYS & silk scarves
3. [COUPERS-FLYIN] Re: Digest list: Ercoupe Hangar Flying
4. Re: [COUPERS-FLYIN] FLYBOYS & silk scarves
Messages:
From: "Jeffrey R. Lewis" <[EMAIL PROTECTED]>
To: "'Ercoupe Hangar Flying'" <[email protected]>
Reply-To: "Jeffrey R. Lewis" <[EMAIL PROTECTED]>
Subject: RE: [COUPERS-FLYIN] Re: Flyboys (Tri-Plane Question)
Why did the mono-wing so quickly dominate? There must be a physical
quality in the chocolate bar wing (a la Ercoupe) that overcomes all
else.....But, what is it?
There are actually two reasons I can think of to explain why a mono-wing
is
more efficient aerodynamically than a bi-plane or a tri-plane (or any
number
of stacked wings if you're really ambitious). The primary reason has to
do
with wing tip vortices. Think about a wing this way - there's high
pressure
air on the lower surface, and low pressure air on the top surface (I'm
sure
most pilots already know this). Out at the wing tips, since there's
nothing
there to block it, that high pressure air can "leak" aroud the tip and
flow
up around to the top surface. That's what creates the wing tip vortex.
As
you can imagine, if air is leaking around the tip, it's not doing its job
of
pushing up on the wing, so the vortex reduces the efficiency of the wing.
That's why for a given wing area, high aspect ratio wings (sail planes)
are
more efficient than low aspect ratio wings (F-104) - less of the wing is
being affected by the wing tip vortex. That's also the reason why for a
given wing area, a monoplane is more efficient that a bi-plane or
tri-plane
- not as many wing tips to create vortices. This is also the reason for
different wing tip designs, such as the winglets on airliners, or the
Hoerner wing tips on general aviation aircraft. I've got a decent picture
of a wing tip vortex on my personal website, from some wind tunnel testing
I
did back in college, if anyone's interested:
http://www.jefflewis.net/graphics/aircraft/aerodesign_P0001840.html
The other reason why bi-planes are less efficient aerodynamically is less
of
a factor, and can be minimized with proper design, but it's still there.
And it's just basically that the wings interfere with each other. Wings
don't just affect the air in their immediate vicinity - they deflect the
air
for a decent ways above and below them. (Here's another picture from my
website, where we put the smoke wand a little higher above the wing, and
you
can still see the air being deflected:
http://www.jefflewis.net/graphics/aircraft/aerodesign_P0001845.html). So,
if you have wings stacked, they'll interfere with each other in that way.
So, that takes care of the aerodynamics, but everything's always a trade
off. Someone already brought up roll rate - the longer your wings, the
higher your inertia, so a bi-plane/tri-plane will give you better roll
maneuverability than a high aspect ratio monoplane of the same wing area.
Another trade-off is structural weight. A bi-plane with the struts and
braces connecting the wings can be made pretty structurally efficient, and
weigh a good deal less than a mono-plane of the same wing area. So, it
becomes a question of, is the increased aerodynamic efficiency of a
mono-plane worth the increased weight. In general, at the speeds most
aircraft fly at today, the answer is yes. At the speeds aircraft were
flying back in WWI, with the materials they had to build their aircraft
out
of, the bi-plane was probably the better option.
Disclaimer: The above discussion was regarding subsonic flow. Once you go
faster than the speed of sound and get shock waves, the aerodynamics
associated with the shock waves becomes a big consideration, and
low-aspect
ratio wings start to look more appealing.
-Jeff Lewis
----------------------------
From: "DONALD BOWEN" <[EMAIL PROTECTED]>
To: "FLYIN" <[email protected]>
Reply-To: "DONALD BOWEN" <[EMAIL PROTECTED]>
Subject: [COUPERS-FLYIN] FLYBOYS & silk scarves
There was a scene in FLYBOYS wherein the French flight instructor
described use of the long, flowing silk scarves to the new American
fighter pilot wannabes. He said "this isn't just to impress chicks, it
keeps your neck from becoming abraided/damaged by all the head turning
required in flight". The enemy force usually tried to descend on the
opposing force from above and out of the sun. Keeping your neck "on a
swivel" was mandatory. Last weekend I flew in company with a pilot in a
BONANZA. he attempted to stay in trail behind my ALON while I "pedaled as
fast as I could" @ 2475 rpm/108 mph. He was back there for more than an
hour, but I never saw him. My arthritic neck bones don't swivel so good
these days. Today I purchased a small ladies' mirror at the local Dollar
Store. it is only 2 1/2" x 3 1/2 " with a short handle. I tried it in
flight and was amazed at what I could see back there between my rudders
and off to the right and left and above and below!! From now on, I'll
never leave home without it! I'll save the silk scarf to impress the
chicks at the retirement home!
Don Bowen
----------------------------
From: [EMAIL PROTECTED]
To: [email protected]
Reply-To: [EMAIL PROTECTED]
Subject: [COUPERS-FLYIN] Re: Digest list: Ercoupe Hangar Flying
Kim,
If you want to come to Florida for a few weeks I know a GREAT CFI who
knows
a 415C very well!
Mark
N2021H
----------------------------
From: ght <[EMAIL PROTECTED]>
To: [email protected]
Reply-To: ght <[EMAIL PROTECTED]>
Subject: Re: [COUPERS-FLYIN] FLYBOYS & silk scarves
Don,
What a super an inexpensive way to solve a problem! I
always wondered if a small mirror would work.
As for the silk scarf, don't wait until you're ready
for the retirement home. Wear it at the airport for
sauntering around, leaning against your plane, and
relaxing in the pilots' lounge. I'm positive that some
of the women will want to know who the handsome guy
with the classy white silk scarf is. :-)
Spook
--- DONALD BOWEN <[EMAIL PROTECTED]> wrote:
good these days. Today I purchased a small ladies'
mirror at the local Dollar Store. it is only 2 1/2"
x 3 1/2 " with a short handle. I tried it in flight
and was amazed at what I could see back there
between my rudders and off to the right and left and
above and below!! From now on, I'll never leave home
without it! I'll save the silk scarf to impress the
chicks at the retirement home!
Don Bowen
----------------------------
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