Fast glass biplanes

"Ed Wischmeyer" wrote in message
...
And if the engine quits, you want to be in the Long-EZ, not
the Glasair -- it glides much better.

That's a questionable statement!!

Compare the following for survivability in an accident:
* slower touchdown speed
* deformation of the structure to absorb energy
* lack of intrusions into the crew area (survivable space)

Looks to me like the Glasair would be much more survivable... not that
I'm personally interested in running the experiments

Okay Ed, I'll take the bait. I assume you're taking issue with which
airplane you'd rather be in, not which one glides better. With engine off
and prop stopped and 80kn, a Long will glide losing 5-700 fpm. Tough to
match that in a Glasair. This would give the Long alarger raidus in which
to find a suitable landing place.

Slower touchdown speed? Unless at a very low gross weight, a Long would be
hard-pressed to get under 60 kn. It's part of the design, I assume, to
assure that the main wong won't stall. The Glasair could probably do
better.

Deformation of the structure? They're both glass -- don't know how you
could say one was better than the other.

Lack of intrusions? The Long's got the nosegear crank, but the Glasair's
got the sticks ... uh ... down *there*. Which is worse? I don't know.

As I said before, the whole reason for a canard airplane is for it's stall-
and spin-limiting abilities, not because it is "more efficient."

karel adams wrote:

My PPL ground school certainly disagrees with you!
Do you have any example of such a design?

Most conventional airplanes when flown in their
approved CG range will have a down force at the tail.
If the CG is moved aft of the aerodynamic center of
the wing alone but remains ahead of the neutral
point of the airplane, the tail will (generally)
have an upward force. Pitch stability will still
be positive, but in most GA cases far less than
most of us are used to.

If it's as you've related, your 'PPL ground school'
may be correct in a statistical sense, but not in a
technical one. Big surprise, that.

Dave 'phugoid phollies' Hyde

On Sun, 16 Nov 2003 20:25:33 +0000, Fred in Florida wrote:


"Ed Wischmeyer" wrote in message
...
And if the engine quits, you want to be in the Long-EZ, not the
Glasair -- it glides much better.

That's a questionable statement!!

Compare the following for survivability in an accident: * slower
touchdown speed
* deformation of the structure to absorb energy * lack of intrusions
into the crew area (survivable space)

Okay Ed, I'll take the bait. I assume you're taking issue with which
airplane you'd rather be in, not which one glides better. With engine off
and prop stopped and 80kn, a Long will glide losing 5-700 fpm. Tough to
match that in a Glasair. This would give the Long alarger raidus in which
to find a suitable landing place.

Lack of intrusions? The Long's got the nosegear crank, but the Glasair's
got the sticks ... uh ... down *there*. Which is worse? I don't know.


If I'm going to be in a crash, and it isn't on flat ground, I would rather
have the engine ahead of me than behind me. I figure it has a bit less
chance of ending up in the cockpit that way.

--
Kevin Horton RV-8 (finishing kit)
Ottawa, Canada
http://go.phpwebhosting.com/~khorton/rv8/
e-mail: khorton02(_at_)rogers(_dot_)com

On Sun, 16 Nov 2003 18:08:58 GMT, Ron Wanttaja
wrote:

On Sun, 16 Nov 2003 15:57:45 +0800, Stealth Pilot
wrote:

I read once that a computer program exploring optimum biplane and
canard setups popped out the optimum setup as one where the forward
canard was 5 times the span of the rear one with the cg at 25% of the
chord of the forward canard.

Actually, that was contained in an article called "Canard Canard" in
AEROSPACE AMERICA magazine, back in the early '90s. I've posted about it
here in RAH several times, that's probably where you remember it from.
Used to have the article rattling around the office, somewhere.

Canard designs are just a different approach to the compromises necessary
for aircraft development. What they gain in eliminating the horizontal
stabilizer downforce, they lose in other areas.

Wanttaja Ron

see we remember what you write ron. :-)

back to the guys original question, I take it that the "lose in other
areas" is why you dont see them as racers mixing it with the less
compromised.

Stealth Pilot

On Mon, 17 Nov 2003 16:28:10 +0800, Stealth Pilot
wrote:

On Sun, 16 Nov 2003 18:08:58 GMT, Ron Wanttaja
wrote:

Canard designs are just a different approach to the compromises necessary
for aircraft development. What they gain in eliminating the horizontal
stabilizer downforce, they lose in other areas.

back to the guys original question, I take it that the "lose in other
areas" is why you dont see them as racers mixing it with the less
compromised.

Nor do you see many canard sailplanes, which place the highest demands on
aerodynamics.

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.

"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.

Earlier, Ron Wanttaja wrote:

...Nor do you see many canard sailplanes,
which place the highest demands on aerodynamics.

The way it's been explained to me, the wake of the canard surface
interacts with the wing flow field so as to make it difficult to
arrive at reasonable compromises for both low- and high-speed flight.
Also, the tip vortex from the canard does things to the wing flow
fields that are hard to compensate for at any speed.

The only canard sailplane I know of, the Rutan Solitaire, had
performance that was whelming at best. Although it won the SHA
sailplane design contest that year, only two or three were ever built.
I believe that none are regularly operated.

Getting near the bounds of this topic, (but I suspect that Jay is
gonna like this one), NASA has done analysis that suggests that there
are substantial gains to be found in joined wing designs. Basically,
the main wing sweeps back and then turns up at a winglet. The
horizontal stabilizer sweeps forward, and joins smoothly to the top of
the winglet. This type of design has potential for low drag and good
strength-to-weight ratios. However, there is relatively little in the
way of real-world validation of these theories. For more information,
see the several technical papers on the topic by Ilan Kroo.

Thanks, and best regards

Bob K.
http://www.hpaircraft.com/hp-24

Dave Hyde wrote in message
There are a lot of benefits to higher aspect ratio
wings that far outweigh the structural advantage of low AR
wings. Reduced drag is but one. Ever wonder why you
don't see any biplane sailplanes?

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? 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?

The fact that you don't see something commonly done says more about
the methods of development starting with what currently works, and
trying to make incremental improvement on it than anything else.
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).

It's generally accepted to draw circle with a diameter of the wingspan,
centered at the middle of the wing. Do this once for every wing. Where
the circles intersect, they are interacting. I know of none that interact
positively. Some less negatively than others.

Another way to look at this is the aspect ratio. Aspect ratio is span
squared divided by the total area. More aspect ratio is better than less.

Anything less than 6 is not very efficient. Decent gliders are above 20.
I've flown one powered plane that was 10. It did very well. Flew like it
had a lot more area than it really had.



In article ,
(Jay) wrote:
Dave Hyde wrote in message
There are a lot of benefits to higher aspect ratio
wings that far outweigh the structural advantage of low AR
wings. Reduced drag is but one. Ever wonder why you
don't see any biplane sailplanes?

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? 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?

The fact that you don't see something commonly done says more about
the methods of development starting with what currently works, and
trying to make incremental improvement on it than anything else.
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).

Ron Wanttaja wrote:

I wonder what one could do with a canard if you eliminated the need to have
the main wing stall before the canard?

Canards with AOA limiters (or without) were at least for a while
the 'flavor of the month' in fighters. See Eurofighter, Gripen,
Rafale, Lavi, X-31, X-29, and A buncha MiG types. You don't
necessarily need to keep the wing from stalling, you just have
to have the control power to break the stall. Look at the size of
the canard and the range of motion on these airplanes sometime.

Dave 'kcud' Hyde