Canard Pros -n- Cons
Jim Schinnerer
study. Last month was bi-planes, but this month, I am looking at the
canard configurations, like the Velocity, Cosy-IV, etc. As I understand
it, they are very efficient as you have two lifting surfaces as opposed to
one lifting and one (opposite of lifting, grounding?) surface.
I suspect that they fly a bit differently, but I have heard that they are
very stable and easy to fly. What's the story there?
If you stall the canard on final, will the nose plop onto the runway, or
will the whole plane just settle on with a thump?
Also, what kind of crash survivability would you have in a glass airplane
with the engine behind you? Seems to me that there wouldn't be much between
you and that tree or rock that your plane is going to hit, and that big,
heavy engine isn't going to stop too quickly.
Are there any canard owners out there?
---------------------------------------------------------
Jim Schinnerer - PP-ASEL-IA | Hewlett Packard
Mooney - 350X - "Buster" | Vancouver, WA
email - schi...@vcd.hp.com | (206) 944-3324
---------------------------------------------------------
Moshe Braner
canards. Any clean light small plane will go fast on little power,
i.e., be efficient. The horiz stab of a standard plane does NOT
need to generate negative lift for stability. That's a common
myth... Typically it generates negative lift at high speeds and
positive lift at low speeds. A well-designed plane will have
near zero stab lift at cruise, for negligible stab induced drag.
Now to the real canard canard (pun intended): When you design
a plane, you start with a target weight and target stall speed.
Assuming a given maximum coefficient of lift, that determines
the wing size. With a canard, one must ensure that the canard
stalls well before the main wing. That means a higher angle
of incidence for the canard. The plane MUST fly at an attitude
that leaves the canard below stall AOA, and the main wing is then
at an even lower AOA, with a max C of L that is rather low, say
around 1.0. A similar wing in a conventional configuration can
go up to, say, a C of L of 1.5. The net result is that the
canard plane needs a bigger wing, or else must land at higher
speeds. If you insist on slower landings (to allow short field
operation) you must invest extra $$$ in a larger wing, and that
larger wing will create extra drag too.
- Moshe
(Cessna 172 with STOL kit -- I'll get a Lancair IV as soon as
I win the lottery...)
Roger Enns
the following comments.
Once the aircraft is in flight, at cruise, say, the Dragonfly
feels very much like a conventional aircraft. I'm sure if a
designer of a canard-winged aircraft wanted to mimick the in
flight characteristics of a C-152, it would be possible, until
the region approaching the stall, that is. Stability, control
response, and other in-flight characteristics are dependant upon
the design, not so much on the configuration, IMHO.
At the present time, we have the Dragonfly set up to allow enough
elevator deflection to attain a full canard stall. Some people
have recommended adjusting this so that the the stall cannot be
attained, as a safetly measure. I have flown the DF with such an
adjustment made. In this case, if you fly short final too slow,
(in our case ~60knots), you will simply not have enough/any
elevator deflection to flare, or arrest the rate of descent above
the runway. The only option then is to add power. I didn't like
this lack of control. It does avoid dropping the nose into the
runway, but proper pilot technique (careful monitoring of
airspeed down short final) eliminates the problem as well. With
the elevator stops readjusted to allow the canard to stall, it is
possible to drop into the runway, (I know from experience!).
However, with the stops adjusted this way, it is possible to land
slower by keeping power on down short final, and cutting power
just before touchdown. Also, the added elevator deflection
allows for more exilerating (sp?) pull-ups, etc.
When stalling our DF, one feels a noticable shake on the elevator
as the flow separates at the trailing edge. As the elevator is
deflected more, the nose starts to bob slowly, through what a
ppears to be about 15 degrees. If the aircraft is loaded aft at
the time, a simple mush may occur. During this entire process, I
have tried various inputs, included full crossed controls, with
no surprises. Full-power stalls are similar, only the bobbing is
a bit more vigorous, and the nose is pointed at the sky instead
of the horizon.
OK, enough babbling, and back to work...
--
Roger Enns (en...@waterloo.hp.com) Panacom Automation Division, HP
C-GIIV Dragonfly, 1979 RX7 13B, 1985 Colt, 1984 Interceptor 500
Andrew Boyd
bra...@theory.TC.Cornell.EDU (Moshe Braner) writes:
>.. The horiz stab of a standard plane does NOT
>need to generate negative lift for stability. That's a common
>myth... Typically it generates negative lift at high speeds and
>positive lift at low speeds.
um, are you really sure about this? As you slow down your C-172,
you pull back on your control column, correct? That causes significant
upward deflection of the elevator, correct? Given that you are moving
forward through the air, you get a cross-sectional picture of the tail
that looks something like this:
air ----> /
/
============/
So, the horizontal stabilizer is pushing downwards at slow speeds.
Or, if you approach it theoretically, you know that your centre of
gravity is forwards of your centre of pressure, with your tail
developing negative lift - you agree that this is correct in cruise,
at least. We get another picture of the forces on the a/c that looks
roughly like this:
^
|
|
|
nose C of G C of P tail
| |
| V
|
V
You are saying that at slow speed, the tail is pushing up. This would
imply that the C of P has moved forward of the C of G. It's true that
the C of P moves forward as you increase your angle of attack, but not
that much, at least in the a/c we fly.
Remember from ground school what happens to your stability as you move
the C of G too far aft, which means it is too close to the C of P?
----
#include <std.disclaimer>
David Doshay
configuration aircraft, the same is true of canard configured aircraft.
The Cozy IV may look a little like a Velocity, but the designers had very
different goals, and hence details like landing speeds are different for
the planes. The Cozy and Rutan designs are far more a handfull than the
Velocity.
Your question about stalling the cannard while landing is a good one, but
is info that is seldom discussed. People talk about the period of the
oscillation, but never the amplitude.
The part about efficiency (both surfaces lifting) turns out to not be true in
actual practice.
David dos...@soma.arc.nasa.gov
The thought police insist I tell you:
my thoughts, not NASA's
David Doshay
|> Some articles I have read have destroyed my early enthusiasm with
|> canards. Any clean light small plane will go fast on little power,
|> i.e., be efficient. The horiz stab of a standard plane does NOT
|> need to generate negative lift for stability. That's a common
|>
|> - Moshe
All of this is true, but may still be of almost no consequence. It depends
upon what you want to use the plane for. Some like canards because they look
cool (and others are allowed to think otherwise). Some like the stall-proof
nature of a properly designed canard, mostly because if they cannot stall
then they cannot spin. I like the canard layout because I do not like sitting
right over the wing or just below the wing. The canard design allows me to
have one wing in front of my feet and the other a few feet behind my head.
There are other ways to get the wings out of my way (like the Cirrus), but
the canard configuration works just fine too.
An airplane is a huge batch of comprimises. First pick a mission profile,
then design the plane around those requirements.
David dos...@soma.arc.nasa.gov
presently sitting below the wing
Michael Corvin
but in terms of 'unconventional' layouts, the three surface layout
used by some of the later Rutan designs and, perhaps most successfully,
by the Piaggio Avanti, may offer 'canard' type advantages while
mitigating some of its drawbacks. In this configuration the tail is
typically used for pitch control and stability while the canard
contributes lift. Having the canard stall first to prevent main wing
stall is still a feature but having pitch control via the tail should
allow (I'm guessing) a higher main wing CL than in a pure canard.
The arrangement may also offer a wider CG range. It may also have
structural advantages,eg it's easier to keep the wing carry-through
out of the cabin since it is farther aft.
Anyone have any qualitative info about this? Are there any
three-surface homebuilts (Apart from biplanes... obviously)?
-----------------------------------------------------------------------------
Michael Corvin PP-ASEL, PP-G zw...@starfighter.den.mmc.com
just another spaced rocket scientist at Martin Marietta Astronautics Group
-----------------------------------------------------------------------------
=============== My views, not Martin Marietta's ========================
-----------------------------------------------------------------------------
Steven A Harlow
> Date: Fri, 11 Sep 1992 01:47:28 GMT
>
> i.e., be efficient. The horiz stab of a standard plane does NOT
> need to generate negative lift for stability. That's a common
> myth... Typically it generates negative lift at high speeds and
> positive lift at low speeds.
--
Steve Harlow, Spinneheim, Glen Ellyn, IL, USA
Lars-Henrik Eriksson
> From: bra...@theory.TC.Cornell.EDU (Moshe Braner)
>> Date: Fri, 11 Sep 1992 01:47:28 GMT
>>
>> i.e., be efficient. The horiz stab of a standard plane does NOT
>> need to generate negative lift for stability. That's a common
>> myth... Typically it generates negative lift at high speeds and
>> positive lift at low speeds.
>Explain that, please.
When the angle of attack increases, the center of lift moves forward.
This is the reason you need a stabiliser in the first place. A wing is
inherently unstable.
So, at low speed, the centre of lift is further forward than at high
speed. This means that at low speeds the stabiliser must give higher
upward (or smaller downward) lift than at high speeds.
--
Lars-Henrik Eriksson Internet: l...@sics.se
Swedish Institute of Computer Science Phone (intn'l): +46 8 752 15 09
Box 1263 Telefon (nat'l): 08 - 752 15 09
S-164 28 KISTA, SWEDEN Fax: +46 8 751 72 30
Bill Coleman
>>> myth... Typically it generates negative lift at high speeds and
>>> positive lift at low speeds.
>
> This is the reason you need a stabiliser in the first place. A wing is
> inherently unstable.
>
> So, at low speed, the centre of lift is further forward than at high
> speed. This means that at low speeds the stabiliser must give higher
> upward (or smaller downward) lift than at high speeds.
But doesn't the tail have to have some downward (negative) lift at all
times to overcome aerodynamic pitching moment? Or am I missing something?
--
Bill Coleman, AA4LR ! CIS: 76067,2327 AppleLink: D1958
Principal Software Engineer ! Packet Radio: AA4LR @ W4QO
Hayes Microcomputer Products, Inc. ! UUCP: uunet!hayes!bcoleman
POB 105203 Atlanta, GA 30348 USA ! Internet: bcoleman%ha...@uunet.uu.net
Disclaimer: "My employer doesn't pay me to have opinions."
Quote: "The same light shines on vineyards that makes deserts." -Steve Hackett.
Moshe Braner
although I am not an expert on this, and the best thing to do is to
consult a textbook on the subject. My comments are based on reading
chapter 2 in Etkin's book.
For an aircraft to fly in an unaccelerated steady-state, both the
forces and the pitching moments must balance out. The forces are
the weight of the aircraft, acting at the CG, the wing's lift, acting
close to the quarter-chord point, and the tail lift. The pitching
moments are forces that want to turn the aircraft on its pitch axis.
Choose any point you want, e.g., the CG, and each force has a moment
equal to the product of the force and its arm (distance from the
place the force acts and the chosen datum point). If we choose the
CG as the datum, the weight has no moment. The tail lift (small)
times the tail arm (large) gives one moment. The wing lift (large)
times the arm (small) is another. The CG may be either in front
of or behind the wing's center of lift, so the wing lift's moment may
be positive or negative. Finally, there is another, usually overlooked,
moment, caused by the aerodynamic forces on the wing. The wing
itself want to twist! That moment depends on the wing's camber.
In a "flying wing" aircraft the wing has negative camber. With
the CG in front of the center of lift, the lift makes a nose-down
moment, and the negative cambered wing (trailing edge up) creates
a nose-up moment, and they balance. But most conventional aircraft
have positive camber in the wing (for better lift) and that causes
a substantial nose-down moment, to be countered by the tail lift.
As the airspeed changes, lift still equals the weight, and the location
at which the lift forces act do not change much. But the wing's
inherent pitching moment changes significantly! That is one reason
why the tail lift must be changed to fit. I.e., one must change the
elevator trim to keep a different airspeed.
Can the tail lift be positive at low speeds even though the elevator
is way up? Think of the trim tab. To keep the elevator UP the trim
tab goes DOWN. The trim tab's lift is then UP, which pushes the
elevator UP, which pushes the tail DOWN! The relationship of the
elevator to the horizontal stab is similar to that of the trim tab
to the elevator, although the elevator is a larger percentage of the
stab's area that the trim tab is of the elevator's area. So it is
indeed possible that the stab as a whole, at high AOA, creates
positive lift even as the elevator itself is creating negative lift.
Is negative tail lift "bad" (inefficient)? Only in the sense that
the tail creates induced drag (whether its lift is positive or negative,
that's why zero tail lift is best), AND in the sense that the main wing
must create a bit more positive lift to compensate, and then IT also
creates some more induced drag. But at cruise speeds induced drag
is small relative to parasite drag, and the tail lift is small relative
to the wing lift, so the whole effect is not very important.
- Moshe
Mike Best
>Just as there are huge differences in the flight dynamics of conventional
>configuration aircraft, the same is true of canard configured aircraft.
>The Cozy IV may look a little like a Velocity, but the designers had very
>different goals, and hence details like landing speeds are different for
>the planes. The Cozy and Rutan designs are far more a handfull than the
>Velocity.
In what manner are they "more of a handfull"? I know they are harder to
build (:)) but my flight experience with the Long EZ and Defiant have
demonstrated to me that they are among the most forgiving and, dare I
say it, EZ planes to fly. However, they do land quite fast!
>Your question about stalling the cannard while landing is a good one, but
>is info that is seldom discussed. People talk about the period of the
>oscillation, but never the amplitude.
>The part about efficiency (both surfaces lifting) turns out to not be true in
>actual practice.
Interesting, are you saying that both surfaces do not simultaneously lift?
If so, are they always in some ocillation behavior? I have not noticed
anything like this in practice (at least I couldn't observe this).
Mike Best
Ron Wanttaja
>
> I like the canard layout because I do not like sitting
> right over the wing or just below the wing. The canard design allows me to
> have one wing in front of my feet and the other a few feet behind my head.
> There are other ways to get the wings out of my way (like the Cirrus), but
> the canard configuration works just fine too.
Not necessarily. The pilot gets a pretty good view in a Long-EZ... but all
the passenger sees is sky and strakes. Oh, OK, a little horizon thrown in.
Locally, a guy owns a plane called a Two-Easy... essentially a Long-EZ wing
on a (four-seat) Defiant fuselage. He ended up cutting some windows into
the lower front fuselage to let folks see the ground.
On the subject of canard efficiency... some aero-engineering students once
wrote a program to determine the optimum ratio of canard vs. main wing
area. The program told them that the most efficient configuration had the
canard five times *larger* than the wing.
Think about it.
My personal opinion? They make neat looking airplanes, but I dislike the
compromises. I have a good buddy (former hangar mate) with a trophy-winning
Long-EZ. A fast plane (on an O-235) but he uses an uncomfortable amount of
runway taking off and landing.
Maneuvers well at altitude... but not as good as some. Terry bounced me once
and came back with pipper burns all over his canopy. He flew around me at
150 mph while I circled inside him, keeping lined up the whole time. If only
I'd armed the Le Prieurs.... :-)
Ron Wanttaja
prang@ssc-bee
...rutgers!uw-beaver!ssc-bee!prang
pr...@ssc-bee.boeing.com
My net.status? A dozen or so articles
leak through every two weeks. 'Course, the
ssc-bee lab is being closed down, so
it hardly makes much difference, does
it? :-(
Judy Cadmus
(Cessna 206) with, among the many other extras, a Horton STOL kit and a
cowling with an optional canard. Has anyone ever seen this configuration on
a Cessna?
--
--------------------------------------------------------------------------------Judy Cadmus PP-ASEL, Instrument Student
Skylane N42202 j...@asns.tredydev.unisys.com
Dr. Daniel R. Masys
>
>Maneuvers well at altitude... but not as good as some. Terry bounced me once
>and came back with pipper burns all over his canopy. He flew around me at
>150 mph while I circled inside him, keeping lined up the whole time. If only
>I'd armed the Le Prieurs.... :-)
>
the engagement (He who Flies Fast decides whether he wants to Fight).
An attack LongEze would have simply set the Sidewinder on soot detector
mode, gotten a lock on the Fly Baby while closing a cruise speed, and
the last thing you would have seen through those goggles was a bright flash.
:-) for the phantasy-impaired
Dan Masys
ma...@nlm.nih.gov
G A Venkatesh
>compromises.
Could you or someone elaborate on what the compromises actually are? Surely
canard planes aren't designed to provide everything one wants. None of the
planes are. Consider something like the Velocity 173 designed for 172 drivers.
How would it compare in terms of design to what someone may want in a 172 or
in an improvement over the 172?
Here are are my list of pros and cons for canard designs from a practical and
aesthetic point of view:
- The restricted rear passenger view in anything other than a single-seat
version of a canard design.
- Small props. I am not entirely sure what this means for the efficiency.
- Stone hits on the prop. The singlemost disadvantage in a pusher configuration.
- Efficient use of space. Compare a 2/4-seater canard design to any other
2/4-seater design. I saw the Lancair ES four-seater in its hangar at
Redmond, OR recently and it is huge. I know it is the same airframe design
as the Lancair IV but I didn't realize how big it really is until I saw the
ES.
- Engine bay fires in flight have been observed to be shooting backwards with
very little damage to the firewall. No smoke/oil smattered windshields in
case of engine failures.
- The difficult-to-stall characteristics that might be just right for some
people and unbearable for others.
Any others that are not of purely theoretical interest?
venky
G A Venkatesh
>Speaking of canards, I saw a for sale ad the other day for a Super Skylane
>(Cessna 206) with, among the many other extras, a Horton STOL kit and a
>cowling with an optional canard. Has anyone ever seen this configuration on
>a Cessna?
Yes. I saw one at Florence, OR recently. Didn't get to see it up close but I
had assumed it was a 182 derivative rather than a 172 derivative.
venky
David Doshay
|> In article <1992Sep12.0...@news.arc.nasa.gov> dos...@ursa.arc.nasa.gov (David Doshay) writes:
|> >Just as there are huge differences in the flight dynamics of conventional
|> >configuration aircraft, the same is true of canard configured aircraft.
|> >The Cozy IV may look a little like a Velocity, but the designers had very
|> >different goals, and hence details like landing speeds are different for
|> >the planes. The Cozy and Rutan designs are far more a handfull than the
|> >Velocity.
|>
|> In what manner are they "more of a handfull"? I know they are harder to
|> build (:)) but my flight experience with the Long EZ and Defiant have
|> demonstrated to me that they are among the most forgiving and, dare I
|> say it, EZ planes to fly. However, they do land quite fast!
I was primarily refering to the landing speed.
|>
|> >Your question about stalling the cannard while landing is a good one, but
|> >is info that is seldom discussed. People talk about the period of the
|> >oscillation, but never the amplitude.
|>
|> >The part about efficiency (both surfaces lifting) turns out to not be true in
|> >actual practice.
|>
|> Interesting, are you saying that both surfaces do not simultaneously lift?
|> If so, are they always in some ocillation behavior? I have not noticed
|> anything like this in practice (at least I couldn't observe this).
|>
Both surfaces do lift, but the induced drag penalty due to the high loading
of the canard cost more than is gained by the extra lift, as compared
with the very small induced drag and the downloading from a tail on a
conventional aircraft. There is a paper by Tad McGeer and Ilan Kroo published
in AIAA Journal of Aircraft, something like '84 or '85, titled "A Fundamental
Comparison of Canard and Conventional Aircraft" that does a reasonable job of
comparing the basic designs. For small static margins the conventional
configuration is more efficient.
The oscillation occurs as the canard stalls. The nose pitches down till the
angle of attack on the canard decreases enough for the canard to generate
the lift required to make the aircraft pitch up again. If the pilot continues
to hold full back pressure, there will be a series of pitch oscillations.
Because we generally want to land slowly to be friendly with the physics
kenitic energy = 1/2 m v^2, a full stall landing is considered nice. The
previous poster was asking about the magnitude of the pitch down at full
stall. If the stall of the canard does not result in pitching down past wings
level, then a full stall landing is OK, but if the pitch down takes the plane
much futher around, the nose-gear forces may be excessive.
All this said, I will add that I like canard designs for other reasons,
and those were posted earlier.
Reid A Baldwin
|> With a canard, one must ensure that the canard
|> stalls well before the main wing. That means a higher angle
|> of incidence for the canard. The plane MUST fly at an attitude
|> that leaves the canard below stall AOA, and the main wing is then
|> at an even lower AOA, with a max C of L that is rather low, say
|> around 1.0.
Would a canard be extremely hazardous if stalled upside down? By the
above explanation, the main wing would be at a higher AOA than the canard
while flying upside down. If the two surfaces have similar aerfoils,
the main (rear) wing would stall before the canard. How would one
recover from such a situation?
Reid Baldwin
Mike Best
>>
>Not necessarily. The pilot gets a pretty good view in a Long-EZ... but all
>the passenger sees is sky and strakes. Oh, OK, a little horizon thrown in.
That's true! I spent about 40 hours in the back seat of a Long until my
Dad got the courage to let me solo and the difference was striking.
The back seat visibility is even worse on landing due to the nose high
attitude ("snobby" landing?). However, the pilot's view is, IMO, better
than that of any plane in the Long's class. With no engine up front
you feel like you are sitting on the nose.
>Locally, a guy owns a plane called a Two-Easy... essentially a Long-EZ wing
>on a (four-seat) Defiant fuselage. He ended up cutting some windows into
>the lower front fuselage to let folks see the ground.
Isn't that one of the Ellison brother's (they make the experimental throttle
body injector)? That was Bob Beard's plane until he crashed and was fatally
injured in it. I saw it in Chandler AZ at Tom McNeilly's place and at the
time he wasn't sure what he was going to do with it. Is it flying now?
By the way, several Long EZs now have the windows in the strakes. These
windows are salvaged from canabalized airliners.
>
>On the subject of canard efficiency... some aero-engineering students once
>wrote a program to determine the optimum ratio of canard vs. main wing
>area. The program told them that the most efficient configuration had the
>canard five times *larger* than the wing.
>
>Think about it.
That'd mess up the view.
>My personal opinion? They make neat looking airplanes, but I dislike the
>compromises. I have a good buddy (former hangar mate) with a trophy-winning
>Long-EZ. A fast plane (on an O-235) but he uses an uncomfortable amount of
>runway taking off and landing.
True, the Long EZ does land long and it takes off long using an O-235.
I am putting a 160 HP O-320 into mine which should, if nothing else,
make me feel better about the takeoff. The Long has a great range and
fuel economy which makes it a good cross country plane ...
just don't take any luggage!
>Maneuvers well at altitude... but not as good as some. Terry bounced me once
>and came back with pipper burns all over his canopy. He flew around me at
>150 mph while I circled inside him, keeping lined up the whole time. If only
>I'd armed the Le Prieurs.... :-)
I guess it all comes down to what kind of flying you want to do, for some
it is flying in circles :) (emphasize the humor).
Mike Best
Mike Best
>In article <55...@ssc-bee.ssc-vax.boeing.com> pr...@ssc-vax.boeing.com (Ron Wanttaja) writes:
>>
>>My personal opinion? They make neat looking airplanes, but I dislike the
>>compromises.
>
>Could you or someone elaborate on what the compromises actually are? Surely
>canard planes aren't designed to provide everything one wants. None of the
>planes are. Consider something like the Velocity 173 designed for 172 drivers.
>How would it compare in terms of design to what someone may want in a 172 or
>in an improvement over the 172?
>
>Here are are my list of pros and cons for canard designs from a practical and
>aesthetic point of view:
>
>- The restricted rear passenger view in anything other than a single-seat
>version of a canard design.
Not true of the Defiant or the CoZy variations. However, the F-16 style
canopy of the Long does provide superb visibility for the pilot (and not
too bad for the passenger IMO.
>- Small props. I am not entirely sure what this means for the efficiency.
Good question, I've seen some blades which resemble scimitars (see the
Berkut!).
>- Stone hits on the prop. The singlemost disadvantage in a pusher configuration
True, especially since we use wooden props due to CG restrictions. Further,
the S-glass landing gear is so stiff that landing on dirt would not be
advisable even if it weren't a pusher. The nose gear is just a notch up
from a shopping cart wheel too (Hey, I can poke fun at myself!).
>- Efficient use of space. Compare a 2/4-seater canard design to any other
> 2/4-seater design. I saw the Lancair ES four-seater in its hangar at
> Redmond, OR recently and it is huge. I know it is the same airframe design
> as the Lancair IV but I didn't realize how big it really is until I saw the
> ES.
Yeah, you can't take much luggage in a Long EZ but the Defiant is another
story. Unfortunately, a Defiant takes a lot more workmanship than the
modern kits - not to the Defiant's credit. In spite of this fact, the
Long does seem to show up after travelling great distances.
>- Engine bay fires in flight have been observed to be shooting backwards with
> very little damage to the firewall. No smoke/oil smattered windshields in
> case of engine failures.
But then again, you can't see what's happening to your engine if it's in
the rear. Of course, chronic irritating oil leaks always smear windsheilds
if the engine is on the front (alas the Defiant has this problem!).
>- The difficult-to-stall characteristics that might be just right for some
> people and unbearable for others.
It does seem to promote a flat landing trajectory (unless you have a constant
speed prop). Is this due to the nature of canards or just the Long EZ
design?
Mike Best
>In article <1992Sep15....@anasazi.com>, be...@anasazi.com (Mike Best) writes:
>|> In article <1992Sep12.0...@news.arc.nasa.gov> dos...@ursa.arc.nasa.gov (David Doshay) writes:
>|>
>|> In what manner are they "more of a handfull"? I know they are harder to
>|> build (:)) but my flight experience with the Long EZ and Defiant have
>|> demonstrated to me that they are among the most forgiving and, dare I
>|> say it, EZ planes to fly. However, they do land quite fast!
> ^^^^^^^^^^^^^^^^^^^^^^^
>I was primarily refering to the landing speed.
Very true, you should try landing on a hot day in Scottsdale AZ in a Long!
>|> Interesting, are you saying that both surfaces do not simultaneously lift?
>|> If so, are they always in some ocillation behavior? I have not noticed
>|> anything like this in practice (at least I couldn't observe this).
>|>
>
>Both surfaces do lift, but the induced drag penalty due to the high loading
>of the canard cost more than is gained by the extra lift, as compared
>with the very small induced drag and the downloading from a tail on a
>conventional aircraft. There is a paper by Tad McGeer and Ilan Kroo published
Again, interesting. Our Defiant has twin O-360 180HP power plants and yet
we've learned that this bird loves to cruise at 200MPH. You can pour more
coal into her but the gallons/kis becomes a limiting factor. We have long
suspected that it is the nature of the canard which has a "drag" effect of
some real kind on the maximum airspeed.
Mike Best
John Bunda
>(Cessna 206) with, among the many other extras, a Horton STOL kit and a
>cowling with an optional canard. Has anyone ever seen this configuration on
>a Cessna?
206 a Super Skylane? Hmmm, I'll bet this is a 182, I think the Super
was added by the STC holder for the STOL mods. Anyhow, I have seen a
182 with this mod - it supposedly climbs well, but it's hard to tell
which cowling feature is most responsible - the canard outside or the
265hp IO-470 inside. Regardless, the canard does draw a crowd, though
hmph, it looks kinda goofy....
--
John Bunda * bu...@cs.utexas.edu * {uunet,harvard}!cs.utexas.edu!bunda
Timothy D Aanerud
The P206 Super Skylane was very similar to the Model 206/U206 but does not
have the 42-inch double cargo doors. They were built from 1965-1970. It
has six seats and a third door on the left side. Cessna built 536 with
Continental IO-520-A @ 285 hp, and 111 with TSIO-520-C @ 285 hp.
My reference is "The Wings of Cessna" by Edward H. Phillps,
ISBN 0-911139-05-2, published by Flying Books. It's about $15 from the
mail order vendors
--
We will get you there within | Timothy Aanerud
2 NM/hr, 95% of the time... | Honeywell Commercial Flight Systems
| Makers of Laser Gyro IRU's
N45 07.9 W93 16.6 | ti...@cfsmo.honeywell.com
Ron Wanttaja
> In article <55...@ssc-bee.ssc-vax.boeing.com> pr...@ssc-vax.boeing.com (Ron Wanttaja) writes:
> >
> >My personal opinion? They make neat looking airplanes, but I dislike the
> >compromises.
>
> Could you or someone elaborate on what the compromises actually are?
Sorry, should have covered that... thought I posted my impressions on the
subject recently, but it probably was five years ago.
EZs are designed around two main goals: Be easy to build, and go fast on a
small engine. Like any designer, Rutan had to make compromises. The
results of these may or may not be acceptable, depending on what you're
looking for in an aircraft.
These have mostly to do with the Long-EZ in particular, based on my
observations of Long EZ N86TD and discussions with its builder, Terry
Dazey. Some of the details may not apply to other canard aircraft.
My opinion regarding the faults of the EZ:
1. Poor short-field performance. Terry's minimum field length is 2500
feet. On a typical day, he uses most of it. It's kind of scary to watch.
This thing goes trundling down the runway, and you sit there waiting, and
waiting, and waiting for the nose to come up.
EZs have a flat climb angle during initial climb, as well.
Because of the canard stall characteristics, he dares not get too slow on
approach. Hence he always lands long... and doesn't dare to use the brakes
very much (see #4).
2. No rough-field capability. The gear has plenty of spring, but stuff
gets knocked into the pusher prop.
3. Temperature sensitivity. You MUST hangar a moldless-composite
airplane, or risk weakening the structure.
4. Fiberglass landing gear. Unless properly handled, the gear legs can
distort. Watch the next time an EZ driver parks his plane... you'll see
him/her get out and lift each wingtip. Watch the wheel as he does that; it
slides in a couple of inches. If the owner doesn't do this, the gear legs
take a "set" and come to like the splayed position.
The gear also affects landing distance. Where does the rolling energy go
when you use brakes? The brakes heat up. What happens to the fiberglass
gear legs when they get hot? Their strength drops. Hence brakes are used
sparingly.
5. Baggage capacity. No luggage compartment in an EZ. There's some room
for flat/soft stuff in the strakes, and you can build "wing tank"-style
baggage lockers.
6. Hot on hot days. You can prop the canopy open while taxiing, but
there's no prop blast to help you get cool.
7. Poor access to rear seat; poor visibility from rear seat.
8. Restricted accomodations. Once you're in place, you can't move much...
feet in tunnels to the pedals, etc. Rear seat room is narrower than front.
Again, these "problems" depend greatly on what you *want* in an airplane.
Terry loves his EZ; the drawbacks don't affect the things HE wants to do.
If I decide to fly to the San Juan Islands, for instance, it's a major
undertaking. One fuel stop, about two hours total block-to-block. Terry
blasts off and is there in a half-hour. He flies to the San Juans just for
the heck of it... I have to plan on a whole day.
Then again, because of his short/soft field limitations, I have just as
many airports within a one-hours' flight as he does. And you find the most
interesting homebuilts/antiques on grass strips....
He has mentioned a wish to hit these places, and has talked about getting a
Kitfox on amphibious floats. While keeping his EZ, of course.
I think I bug him most on hot days. He comes taxing in covered in sweat
after a hot-and-fast landing and a slow, breezeless taxi... only to see me
shoot by in shirtsleeves and goggles, waving at him from the open
cockpit.
|"3/4 through with the annual... total
_|_/ cost so far: $7.25!"
/(_)\
-------:==^==:-------
[[| o |]]
-----------------__________\_____/__________-----------------
_ / \ _
T T/_______\T T Ron Wanttaja
| | | | prang@ssc-bee
""" """ pr...@ssc-bee.boeing.com
Roger Ritter
> _|_/ cost so far: $7.25!"
> /(_)\
> -------:==^==:-------
> [[| o |]]
> -----------------__________\_____/__________-----------------
> _ / \ _
> T T/_______\T T Ron Wanttaja
> | | | | prang@ssc-bee
> """ """ pr...@ssc-bee.boeing.com
Right, Ron, make us all jealous (again!). Rocky goes in for his
annual in a couple of weeks. I plan to help out, and he's pretty
simple, but I still don't expect to get out for less than a
couple of hundred. And it may be much worse, of course :-(.
--
Roger Ritter N1FZZ (R.Ri...@ma30.bull.com) PP-ASEL, AGI
1946 Luscombe 8A N71983 "Rocky"
Sheep do not so much fly as plummet! NH CAP: Profile 49
G A Venkatesh
>These have mostly to do with the Long-EZ in particular, based on my
>observations of Long EZ N86TD and discussions with its builder, Terry
>Dazey. Some of the details may not apply to other canard aircraft.
Yes, I think the variants have improved on some of those characteristics.
>1. Poor short-field performance. Terry's minimum field length is 2500
>feet. On a typical day, he uses most of it. It's kind of scary to watch.
>This thing goes trundling down the runway, and you sit there waiting, and
>waiting, and waiting for the nose to come up.
Do you know if Long-EZ drivers start with less than full power in the beginning
to avoid too much debris from being sucked into the propeller arc. I know that
this is a recommended procedure on the Berkut. Full power is not applied until
the plane attains about 40mph.
But you are right about the short-field performance of canard planes in
general. Even the Velocity 173 has an "advertised" minimum of 1600ft at gross.
Although this compares well with some of the 4-seater spam cans. I am convinced
that skimping on power on the canard planes is a bad idea. While you can get
away with an engine in the lower end of the recommended range for Glasairs and
Lancairs without too much of a problem, it is advisable to select an engine
at the upper end of the recommended range for a canard plane.
>Because of the canard stall characteristics, he dares not get too slow on
>approach. Hence he always lands long... and doesn't dare to use the brakes
>very much (see #4).
The speed brakes can help somewhat to control the descent rate. Although glider
like spoilers would probably have been better. The Velocity 173 people have
managed to get the landing speeds into the 65-70 mph range.
>3. Temperature sensitivity. You MUST hangar a moldless-composite
>airplane, or risk weakening the structure.
I am curious about this. How does the presence of a mold affect the response
to UV/heat? Faster delamination?
>
>The gear also affects landing distance. Where does the rolling energy go
>when you use brakes? The brakes heat up. What happens to the fiberglass
>gear legs when they get hot? Their strength drops. Hence brakes are used
>sparingly.
Wouldn't this also apply to the fixed-gear Glasair II?
>5. Baggage capacity. No luggage compartment in an EZ. There's some room
>for flat/soft stuff in the strakes, and you can build "wing tank"-style
>baggage lockers.
The strake compartments have been getting bigger and bigger on the variants.
So why not flaps on canard planes? My next post.
venky
G A Venkatesh
I am not an aeronautical engineer but I would like to bring up the possibility
of introducing flaps on canard planes with a pusher prop arrangement (EZ-like).
Is it possible at all and if so is it too complicated?
The problem as I see it is that flaps on the main wings have no benefits
since the canards stall first anyway. A speed brake/spoiler gives a better
control for providing drag.
How about a rotating canard that has a variable AOA that is tied to the flap
deployment on the main wings? Does this help? Is it too difficult to design and
too expensive to build? Are ther other advantages to a rotating canard?
I am leaving the questions rather vague and open to provoke discussion.
venky
Roger Enns
Rutan had a unique flap setup on the Catbird (the most ugly
aircraft of all time??). The canard already has flaps, used as
elevators. On landing the canard is at a high angle of attack,
approaching the stall region. I think if flaps were installed on
the main wing, a dangerous situation of having both wing and
canard stalling at the same time could occur? On some Dragonflys
and Q-2s people have installed aileron reflexors. This allow the
ailerons to be adjusted up and down together. Some people use
this as a trim method, others for getting the tail down quicker
after touchdown. This effectively gives them flap-type devices
on the main wing, although the travel is generally quite limited,
and is usually set above trail. I believe that in order to keep
the aircraft balances, if you add lift to the wing (via flaps),
you have got to add lift to the canard. If the canard is already
nearing stall, there is no more lift available.
I hear that the Beech Starship uses a canard which can be swept
back in flight, and then adjusted to zero sweep for landings.
I believe this gives them the extra lift on the canard at low
airspeeds.
--
Roger Enns (en...@waterloo.hp.com) Panacom Automation Division, HP
C-GIIV Dragonfly, 1979 RX7 13B, 1985 Colt, 1984 Interceptor 500
David Doshay
The canard is already quite loaded, and the extra pitching moment caused
by a flap on the main wing would swamp the canard. Rutan put flaps on the
Grizzly, but he put them on both the main wing and the canard. One reason
this is not done on most canard homebuilts is the complexity due to the fact
that both must deploy together.
Bill Coleman
> In article <55...@ssc-bee.ssc-vax.boeing.com> pr...@ssc-vax.boeing.com (Ron Wanttaja) writes:
>
>>Because of the canard stall characteristics, he dares not get too slow on
>>approach. Hence he always lands long... and doesn't dare to use the brakes
>>very much (see #4).
>
> The speed brakes can help somewhat to control the descent rate. Although glider
> like spoilers would probably have been better. The Velocity 173 people have
> managed to get the landing speeds into the 65-70 mph range.
Yup. By adding lots of drag via a bigger main wing. Kinda like a permanent
lifting speed brake....
>>3. Temperature sensitivity. You MUST hangar a moldless-composite
>>airplane, or risk weakening the structure.
>
> I am curious about this. How does the presence of a mold affect the response
> to UV/heat? Faster delamination?
I believe he is referring to delamination. Why a hanger is necessary is
beyond me, although it speaks volumes for why you don't find moldless-composite
planes painted black.
Depending on the type of epoxy, the glue can outgas when heated. When this
happens, the gas tends to collect between layers of glass, causing bubbles
and a weakening of the structure.
For typical moldless work, Saf-T-poxy won't outgas until it hits around
225 degrees F. I don't know where the original poster is parking his
moldless-composite plane, but I don't want to visit there.
My friend who's building a Defiant and I did an experiment at Lakeland Sun 'n
Fun a year ago. We were out on the flight line at 11:00 on a sunny day. We
did a simple test. We placed our hand over a spot on Big Orange (one of
the Velocity prototypes, painted bright orange). Then we placed our hand
on a similar spot on a nearby glasair, painted white. There was a noticable
difference.
You can have any choice of color for your moldless composite airplane, so
long as it is white. <grin>
> So why not flaps on canard planes? My next post.
Think pitching moment....
Actually, the fully deployed canard elevator during a maximum pitch
landing attitude pretty much simulates the drag of flaps, don't you
think?
Lee Devlin
posting the net a few years ago when I was inquiring about Long EZs and
Variezes.
Ron Wanttaja writes:
>David Doshay writes:
>> I like the canard layout because I do not like sitting
>> right over the wing or just below the wing. The canard design allows me to
>> have one wing in front of my feet and the other a few feet behind my head.
>> There are other ways to get the wings out of my way (like the Cirrus), but
>> the canard configuration works just fine too.
>Not necessarily. The pilot gets a pretty good view in a Long-EZ... but all
>the passenger sees is sky and strakes. Oh, OK, a little horizon thrown in.
It's true that in straight and level flight the passenger's view is not
anywhere near as good as the pilot's but it's MUCH better than the back
seat of most planes. The canopy allows excellent viewing during turns
for the passenger and... well.... if you roll it the view becomes quite
spectacular :-).
>On the subject of canard efficiency... some aero-engineering students once
>wrote a program to determine the optimum ratio of canard vs. main wing
>area. The program told them that the most efficient configuration had the
>canard five times *larger* than the wing.
>Think about it.
I assume you're trying to say it would look like a conventional plane,
no? But then how could we hang the engine on the back where it belongs?
>My personal opinion? They make neat looking airplanes, but I dislike the
>compromises. I have a good buddy (former hangar mate) with a trophy-winning
>Long-EZ. A fast plane (on an O-235) but he uses an uncomfortable amount of
>runway taking off and landing.
Well, they are quite neat IMHO too, and I've had several rides in a Long
EZ and we took off and landed in less than 1500 feet. Of course it
had a pilot at the controls with more than 700 hours in type. I know
you have to be very good to get performance like that. My friend
frequently consumed about 2500 ft of runway when he was first learning
to fly it.
Lee (another EZ fan) Devlin
Charlie Stone 4915162
>
>>>3. Temperature sensitivity. You MUST hangar a moldless-composite
>>>airplane, or risk weakening the structure.
>>
>> I am curious about this. How does the presence of a mold affect the response
>> to UV/heat? Faster delamination?
>
>I believe he is referring to delamination. Why a hanger is necessary is
>beyond me, although it speaks volumes for why you don't find moldless-composite
>planes painted black.
>
>Depending on the type of epoxy, the glue can outgas when heated. When this
>happens, the gas tends to collect between layers of glass, causing bubbles
>and a weakening of the structure.
>
I spoke to my friend Charlie Urwin of Universal Plastics WA about the
safe maximum temperature for reinforced epoxy systems in aircraft.
He does a lot of repairs on gliders, is licenced to fix power aviation
plastics, and is eminently qualified to comment after years of experience.
A good generalisation is that once the primary structure reaches a
saturated temperature of 54 degrees C (130 F), then the aircraft should not
be flown. Parked in the sun on a hot day, this temperature is easy to reach
and the darker the surface, the quicker it gets there. There are a lot
of unknowns and different resin systems will have different safe maximum
and minimum temperature ranges. Remember that not only does the epoxy
tend to soften as it heats up (changing flutter characteristics perhaps)
but it also can become very brittle at very low temperatures (like when
you have spent a couple of hours very high in wave soaring).
This is a subject that probably hasn't had the research done that it
deserves.
Charlie Stone
********************************************************************************
\--------------------------(^)--------------------------/
___|___
For my next (and possibly last) manoevre !!
C. Stone.
Perth, Australia.
********************************************************************************
G A Venkatesh
>> like spoilers would probably have been better. The Velocity 173 people have
>> managed to get the landing speeds into the 65-70 mph range.
>
>Yup. By adding lots of drag via a bigger main wing. Kinda like a permanent
>lifting speed brake....
Hmm... larger wheels, larger wing, larger canard.. not all of them to reduce
landing speed. They claim an engine-at-idle glide ratio of 1:20 and a maximum
demonstrated speed of 197mph and minimum speeds at 55-65. A very respectable
envelop without having to worry about building flaps.
>>>3. Temperature sensitivity. You MUST hangar a moldless-composite
>>>airplane, or risk weakening the structure.
>>
>> I am curious about this. How does the presence of a mold affect the response
>> to UV/heat? Faster delamination?
>
>I believe he is referring to delamination. Why a hanger is necessary is
>beyond me, although it speaks volumes for why you don't find moldless-composite
>planes painted black.
I guess my emphasis was on "moldless" rather than on composite. I was wondering
why the molded-composite has a lesser chance of delamination due to heat than
a moldless-composite.
venky
Roger Enns
>I guess my emphasis was on "moldless" rather than on composite. I was wondering
>why the molded-composite has a lesser chance of delamination due to heat than
>a moldless-composite.
>
>venky
>
I believe the molded composite structures are cured in an
autoclave at temperatures much higher than they will experience
during use (if painted a light colour). Some moldless composite
homebuilt plans instruct curing by wrapping the structure in
black plastic bags and setting in the sun for a few hours. This
gives temps of 150 deg F, I've heard. A rule of thumb I've heard
mentioned is that the composite structure will not plastically
deform until it exceeds the temperature at which it was cured. I
do not know the truth to this statement, however.
It is interesting to note that the beautiful red Lancair 320 in
the add on the back of Kitplanes last year has been re-painted a
lighter colour. I believe the red remains as a wide stripe down
the fuselage, but the wing and tail has been painted a tan
colour.
G A Venkatesh
>>
>>I guess my emphasis was on "moldless" rather than on composite. I was wondering
>>why the molded-composite has a lesser chance of delamination due to heat than
>>a moldless-composite.
>>
>
>autoclave at temperatures much higher than they will experience
>during use (if painted a light colour).
Not necessarily. There seem to be two major schools. Lancair's pre-preg method
which uses an autocalve and Glasair's wet layup method which is done at room
temperature (although the resin itself might get rather hot due to an
exothermic reaction while curing). I wonder what the Glasair builders have
experienced with heat.
It is interesting to read the debate about the two methods in the Glasair
and Lancair technical brochures.
>Some moldless composite
>homebuilt plans instruct curing by wrapping the structure in
>black plastic bags and setting in the sun for a few hours. This
>gives temps of 150 deg F
Or with a heat gun as recommended by Lancair.
, I've heard. A rule of thumb I've heard
>mentioned is that the composite structure will not plastically
>deform until it exceeds the temperature at which it was cured. I
>do not know the truth to this statement, however.
The other variable is the effect of heat on the core material used. The above
statement makes sense for at least the deformation of the core.
venky
Richard Johnson
: I am not an aeronautical engineer but I would like to bring up the possibility
Now I'm not one of those sci.aeronautics enigneers, but I have thought
about this very problem some. :=)
First, why would we WANT flaps on our canards?
Well, it would be nice to be able to, when needed, fly a nice high,
steep approach without having to turn having the approach angle turn
into speed when we flare.
But do we need _flaps_ to do this for us? Why don't speed brakes do
enough?
"Ah" you say -- it's not the angle of approach that matters, its the Angle
of attack.
I say you're absolutely right! Sometimes we'd like to be able to get
that nose so far up in the air we're looking at our feet! (Not really,
but you get the idea.) Really what we're after is a wider envelope.
We want to be able to put her down at 50 mph. Saves wear and tear on
the tires, the plane, and the pilot. Makes for shorter field
performance too.
I put this part in here to get us canard lovers to think about what
*exactly* it is we want from flaps. The above is my answer. If yours
differ, squawk.
======
On to the good stuff.
Just because flaps are traditional doesn't mean they're the best thing for
this job. There are air fences, turbulators, and leading edge slots,
too. Some of them might be a better choice for stretching the left side
of the envelope than flaps are- even if they down't work as brakes too.
The problem of putting configuration-altering devices (flaps 'n' slats) is
that we would have to change the shape of both the front and rear
airfoils. If both sets don't change *together*, wierd things can happen.
Here's my truth table:
Front Wing (small) Back wing (big) Result
-----------------------------------------------------------
clean clean normal flight
clean dirty inefficient flight (1)
dirty clean ****POSSIBLY DANGEROUS*** (3)
dirty dirty higher alpha possible (2)
(1) As Venky said, the main can't stall anyway, so why do this (unless
it's a failure of some kind)?
(2) In this configuration, both airfoils have arrived at new shapes that
(hopefully) are carefully chosen to work at higher angles of attack,
which would enable slower, steeper, flight.
(3) If the canard can reach a substantially higher angle of attack than
the main, then it would be possible for the main to stall first. This
is the much-maligned "deep stall" we've heard about for canards.
The point I'm trying to bring out is that while configuration change is an
interesting concept to explore the risk of partial failure might grossly
outweigh the advantages of slower flight.
Also, how do you make a device to extend flaps or slats on the canard,
which can rotate up/down in flight?
I personally think that a few fences, top and bottom; maybe a few
turbulators; and a bigger wing (a la Velocity 173) are a much more
practical solution to the shallow landing/long roll problem than flaps
are. They are lighter, simpler, and cheaper. But they do eat into your
cruise speed (a little) and your top speed (noticably).
=====
Nomex now on. Flame away. :=)
--
Richard Johnson (rdj%adpgat...@apple.com) (ric...@agora.rain.com)
Sic transit gloria mundi.
Ron Wanttaja
> In article <55...@ssc-bee.ssc-vax.boeing.com> pr...@ssc-vax.boeing.com (Ron Wanttaja) writes:
>
> >3. Temperature sensitivity. You MUST hangar a moldless-composite
> >airplane, or risk weakening the structure.
>
> I am curious about this. How does the presence of a mold affect the response
> to UV/heat? Faster delamination?
In this case, the term "Moldless composite" was a substitute for saying
"Room-temperature-curing composites". Composites which are cured in a
kiln (i.e., "prepregs") aren't as sensitive to the kinds of heat that can be
generated by solar exposure.
Most of the molded-composite jobs are cured at room temperature. They're
painted light colors to reduce solar heating. Lancair is an exception;
yet at last report they were still recommending their aircraft be painted
lighter colors (while, of course, parading their Ferrari-red prototype
through the magazines...).
As for the Glasair FG landing gear legs, I thought they were steel. They
probably attenuate the temperature sufficiently before it gets to the
structure. But I'll give 'em a call and ask....
Mike Best
>I believe he is referring to delamination. Why a hanger is necessary is
>beyond me, although it speaks volumes for why you don't find moldless-composite
>planes painted black.
After spending years building the dang thing I'd want to hangar it too :)
>Depending on the type of epoxy, the glue can outgas when heated. When this
>happens, the gas tends to collect between layers of glass, causing bubbles
>and a weakening of the structure.
>
>For typical moldless work, Saf-T-poxy won't outgas until it hits around
>225 degrees F. I don't know where the original poster is parking his
>moldless-composite plane, but I don't want to visit there.
Nice to know, I'm using Saf-T-Poxy II. By the way, Burt Rutan has always
emphasized the need to use white (or a variation thereof) for the paint
on the finished product. So what color did his brother paint his Long?
Sky Blue (probably OK - it's still flying).
Flying in Phoenix, the pilot delaminates before the plane does anyhow.
>My friend who's building a Defiant and I did an experiment at Lakeland Sun 'n
>Fun a year ago. We were out on the flight line at 11:00 on a sunny day. We
>did a simple test. We placed our hand over a spot on Big Orange (one of
>the Velocity prototypes, painted bright orange). Then we placed our hand
>on a similar spot on a nearby glasair, painted white. There was a noticable
>difference.
>
>You can have any choice of color for your moldless composite airplane, so
>long as it is white. <grin>
We have a white base on our Defiant... with black trim (yikes!)
Mike Best
Mike Best
>autoclave at temperatures much higher than they will experience
>during use (if painted a light colour). Some moldless composite
>homebuilt plans instruct curing by wrapping the structure in
>black plastic bags and setting in the sun for a few hours. This
>gives temps of 150 deg F, I've heard. A rule of thumb I've heard
>mentioned is that the composite structure will not plastically
>deform until it exceeds the temperature at which it was cured. I
>do not know the truth to this statement, however.
Can anyone verify this rule of thumb? I was not aware that the temperature
at which the cure happens has an effect on the maximum temperature
which the structure can withstand.
I had to repair a cowling _quick-like_ once. I glassed the cowl and
stuck it in a garbage bag in the sun in Phoenix, it cured fast! Doing
glass lay-ups in warm weather (by hand) usually results in lighter
components due to the lower viscosity of the epoxy (requires less glue).
Mike Best
Mike Best
>
>>I am not an aeronautical engineer but I would like to bring up the possibility
>>of introducing flaps on canard planes with a pusher prop arrangement (EZ-like).
>>Is it possible at all and if so is it too complicated?
>>
>Rutan had a unique flap setup on the Catbird (the most ugly
>aircraft of all time??). The canard already has flaps, used as
Ugly? Perhaps. But a marvelous performer at the CAFE 400.
I happen to believe that the Grizzly is among the ugly elite. It may be
said that Rutan's willingness to design on the basis of functionality
rather than looks is to his credit.
>elevators. On landing the canard is at a high angle of attack,
>approaching the stall region. I think if flaps were installed on
>the main wing, a dangerous situation of having both wing and
>canard stalling at the same time could occur? On some Dragonflys
>and Q-2s people have installed aileron reflexors. This allow the
>ailerons to be adjusted up and down together. Some people use
>this as a trim method, others for getting the tail down quicker
>after touchdown. This effectively gives them flap-type devices
>on the main wing, although the travel is generally quite limited,
>and is usually set above trail. I believe that in order to keep
>the aircraft balances, if you add lift to the wing (via flaps),
>you have got to add lift to the canard. If the canard is already
>nearing stall, there is no more lift available.
A main wing stall prior to a canard stall on the Long EZ has been
blamed for at least one fatality, your point is valid.
>I hear that the Beech Starship uses a canard which can be swept
>back in flight, and then adjusted to zero sweep for landings.
>I believe this gives them the extra lift on the canard at low
>airspeeds.
This concept might allow the Long to acheive higher speeds too.
However, it wasn't designed to go much faster than it's going
already. I've met some builders who have had to rebuild their
ailerons specially to avoid flutter because they are going so
fast (for a Long).
Mike Best