Fast glass biplanes

Jay wrote:

You bring up a good point about sailplane wings having the best L/D
ratios. But why not take each of those sailplane wings and put one
over the top of the other?

Because a single wing of equivalent area but longer span will
be more efficient in terms of drag. Biplanes are a simple,
but inefficient, way of getting more lift from wing area
when an increase in span is not feasible. The are not, nor
in general are they intended to be, "low drag."

You mentioned the interference drag, so how far do wings
need to be vertically separated for a given airfoil
and stagger for this effect to be negligable?

*negligible?* Some *large* fraction of the span. At a minimum.
Some airplanes are able to use the interaction for benefit,
but it's usually for things like lift improvement at high
AOA. Drag reduction requires doing things at the tips to
make the wings 'think' they are longer and thus have a higher AR.
Just slapping another wing on there ain't gonna do it.

Sometimes the rat maze requires the rats (RAH) to back up and choose
another path, which in the short term means he is actually retreating
from the cheese (speed).

And knowing where to depart from the maze requires either a
foundation in basic principles or blind luck. Given the well-
known relationship between drag and aspect ratio, these principles
lead most people *away from*, not *to* biplanes for drag reduction.
How 'bout a challenge: I can show you mathematically and using physical
relationships why (without aerodynamic treatments like winglets or
conjoined
wings) two wings will produce more drag than a single wing of equivalent
area but higher aspect ratio. Your challenge: Prove the physics wrong.
Show how a second wing will result in less drag. Show me the math.

Dave 'usenet wind tunnel' Hyde

In article , Ron Wanttaja says...


Maybe with todays technology that could be achievable.But for right now
all I can do is repeat what one of my Aero teachers said " the Indians knew
which end of the arrow to put the feathers" and "when did you ever see birds
with their tails where their beaks oughta be?" Although flying wings are
achieving with computers flight efficiency that here to fore was impossible with
pilot only control systems. Northrop was farther advanced with airframes then
the electronics industry was with computers.

See ya

Chuck


I wonder what one could do with a canard if you eliminated the need to have
the main wing stall before the canard? Seems like a fly-by-wire sort of
system could sense when the wing was about to stall and limit canard
up-travel to prevent it happening. Or the plane could incorporate a system
to provide sudden downforce if the plane started to pitch up
(compressed-air jets in the nose, etc.). Seems a pity that you have to
avoid operations at the wing's highest efficiency points in an otherwise
efficient design.

In article , Dave Hyde says...

Don't bet any big money cause Dave (usenet wind tunnel) Hyde is right.
Just think, if he was wrong we'd be seeing Biplane Boeing 777's,these guys spend
millions to get a couple percent increased efficiency on their transports.
Better believe if a biplane was more efficient they'd be doing it.
No if's, ands, or buts. :-)

Chuck(Lewis 10X10 wind tunnel) S




How 'bout a challenge: I can show you mathematically and using physical
relationships why (without aerodynamic treatments like winglets or
conjoined
wings) two wings will produce more drag than a single wing of equivalent
area but higher aspect ratio. Your challenge: Prove the physics wrong.
Show how a second wing will result in less drag. Show me the math.

Dave 'usenet wind tunnel' Hyde

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

On 17 Nov 2003 10:50:07 -0800, (Jay) wrote:

But why not take each of those sailplane wings and put one
over the top of the other? You mentioned the interference drag, so
how far do wings need to be vertically separated for a given airfoil
and stagger for this effect to be negligable?



jay
I seem to recall something that tried this.
the dynamics of the thing bought it undone.
as the forward wind flexes it alters the flow over the rear wing and
induces flexing. the thing can self destruct if you get the thing
wrong.

Stealth (everything is aeroelastic to some degree) Pilot

In article , Dave Hyde says...

Yup that sure would have changed that Turkeys perspective.He no longer was
seeing where he was going but where he was.

Chuck (I turkey hunt with a shot gun) S


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

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.

"C J Campbell" wrote in message ...
"John Oliveira" wrote in message
...
| The only one I know of is the Lionheart - Semi Replica of Beech Stagger
| Wing.
|
| Fast, caries high load, round engine.

Looking at Griffon's web site lately, they seem to talk about the Lionheart
in only a historical context and customer support. It does not appear that
they are producing kits any more.

The Lionheart is (was) an exceptionally pretty airplane. It seemed
that the cabin load and volume were comparable to a Cherokee Six.

IIRC (and I don't always) Kitplane wrote a pilot report and had some
adverse comments regarding stability or handling but I sensed they
were hopeful those things could be resolved; some of the problem
perhaps being related to mis-rigging after the plane was painted.

There were built two aircraft built by folks other than the company
that were lost in accidents on the runway although (again relying on
memory) one occurred on takeoff and one on landing. Sadly, one was on
its maiden flight. I don't recall any common root or contributory
causes.

I tried to go by and see the prototype once when I was in Huntsville,
AL but I had no luck.

Take care . . .

John

"C J Campbell" wrote in message ...
"John Oliveira" wrote in message
...
| The only one I know of is the Lionheart - Semi Replica of Beech Stagger
| Wing.
|
| Fast, caries high load, round engine.

Looking at Griffon's web site lately, they seem to talk about the Lionheart
in only a historical context and customer support. It does not appear that
they are producing kits any more.

Follow-Up Message.

I looked at the NTSB site and gear design was mentioned in the
findings for both Lionheart accidents. I'm not an engineer, so I
leave it up to the rest of you to consider the information.

Sad though because I still think it was a drop-dead beautiful
airplane.

John

Dave Hyde wrote in message ...

Thanks for taking the time to make insightful comments on the
discussion.

Because a single wing of equivalent area but longer span will
be more efficient in terms of drag. Biplanes are a simple,
but inefficient, way of getting more lift from wing area
when an increase in span is not feasible. The are not, nor
in general are they intended to be, "low drag."

You must understand that when I say "biplane" I'm not talking about a
Jenny or Spad, I just mean an airplane that meets the requirement of
having 2 lifting surfaces. I understand those early designs were
optimized for the heavy powerplants and weak construction materials of
the era, and had high drag wings that developed a lot of lift at low
speeds.

*negligible?* Some *large* fraction of the span. At a minimum.
Some airplanes are able to use the interaction for benefit,
but it's usually for things like lift improvement at high
AOA. Drag reduction requires doing things at the tips to
make the wings 'think' they are longer and thus have a higher AR.
Just slapping another wing on there ain't gonna do it.

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). I think its a function of the airfoil dimensions (chord,
thinkness, shape) and stagger. I do realize that near the
fusalage/tip there is disturbance but this diminishes as you move away
on the span. 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.

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 is to say, assuming you only have a
single wing, and you need to decide how you can distribute your square
feet of area, you'd pick a long skinny wing.

And knowing where to depart from the maze requires either a
foundation in basic principles or blind luck. Given the well-
known relationship between drag and aspect ratio, these principles
lead most people *away from*, not *to* biplanes for drag reduction.

Thats the problem with rules of thumb, often the people using them
forget the assumptions that went into the rule.

How 'bout a challenge: I can show you mathematically and using physical
relationships why (without aerodynamic treatments like winglets or
conjoined
wings) two wings will produce more drag than a single wing of equivalent
area but higher aspect ratio. Your challenge: Prove the physics wrong.
Show how a second wing will result in less drag. Show me the math.

That sounds like a fun challenge. I think we're going to have to
speak in realtionships instead of mathematic expression because we're
using the usenet as our white board. Okay, why don't you start off by
showing me how span comes into the relationship of air moving over a
wing's airfoil.

Dave 'usenet wind tunnel' Hyde


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.