Hershey bar wing vs composite wing - how much drag?

Bill Daniels wrote:
Sailplanes are the key to understanding the advantages of composite
structures. Current sailplane design is several decades ahead of composite
airplane design in this area. Sailplane performance MUST come from
aerodynamics and structures since there is no other way to get it. (You
can't cover up a bad airframe design with more power)

Composites are indeed heavier than metal but if carbon fiber is used, not
that much heavier. The real payoff is in the extremely smooth surfaces that
promote natural laminar flow. The payoff is huge across the entire speed
spectrum but highest at the low speed end where the flow is less stable and
more likely to separate if the wing surfaces are rough.

The effect of weight and drag is easy to compute. Just divide the aircraft
weight by L/D ratio to get the drag. Weight has an effect but L/D has a
bigger effect. Slick, high aspect ratio wings are the future.

The trouble is that a little bit of dirt, bugs or ice and you can lose a
lot of lift in a hurry. This may not be a big deal for gliders, but for
powered planes that fly in real weather a more tolerant airfoil isn't
such a bad deal.

Matt

On Mar 28, 4:35 pm, Alphonse Le Creur wrote:
"BobR" wrote roups.com:





On Mar 28, 12:40 pm, Alphonse Le Creur wrote:
"BobR" wrote in
news:1175092590.355514.234030 @y80g2000hsf.googlegroups.com:

On Mar 28, 8:51 am, Nathan Young
wrote:
I have a Cherokee 180, with the short hershey bar wing. While I
love the plane, I always wish it could go a bit faster, or use a
bit less fuel to get to my destination.

I have followed the composite homebuilding movement for many
years, and am amazed at the sleekness of a composite wing. The
wings on
most
composites tend to be the complete opposite of a Hersey bar wing:
high aspect ratio, low thickness, no rivets, no screws for fuel
tanks,smooth curves faired into airframe, and streamlined landing
gear
structure.

So my question: How much drag does a wing on a Hersey Bar
Cherokee generate, and and hypothetically speaking, how much
faster could the plane go if it was retooled with a sleek,
composite wing?

I can't remember if it was Kitplanes or SportAviation that had a
recent article on a Piper knockoff being produced as a kitplane in
South Africa. That might be a good starting point for the
difference in performance between the different planes as well as a
discussion of the differences in design and construction. Much of
the difference has to do with better airfoil designs being used but
also weight differences.

Well, that airplane is "inspired" by the Commanche and it's really
just comparing apples and oranges since there are so many other
differences in the two airplanes, but having said that, it's better
than comparing a cherokee to a Cozy, for instance..

In any case, the Ravin Commanche is
herehttp://www.saravin.com/review.htm

ALC- Hide quoted text -

- Show quoted text -

It's about as close a comparison as can be made. I am building the
KIS Cruiser which uses a hershey bar style wing as well but the
airfoil is different. The comparison from a performance standpoint is
much faster than the Commanche for the same power (180 hp). The
difference must be attributed to several differences beyond just the
wing, weight being the most obvious.

Well, the Ravin is actually a couple hundred pounds heavier than the
original Commanche empty and has a higher gross. It also has a much
smaller fuselage cross section.
I'm certainly not saying that the Ravin is not a better airplane. It is.
I'd sure like to have one! I'm just saying that while it is probably one
of the better comparisons, no absolute conclusion may be made from it.
There's too many other things going on there. The Commanche uses what
was a then state of the art NACA 6 series laminar flow airfoil. It was
streets ahead of what was on any lightplane of the time, but it's use
was most probably not dictated by the material of which it was made. I
have no idea what the Ravin is using for an airfoil.
If Piper were to set out to make the same airplane again today using
aluminum for the wing, they could still build a more efficient wing than
they did in the fifties by simple virtue of the fact that fifty years
later there's been quite a lot of innovation in airfoils, structures and
what not. Again, I'm not saying that the Ravin isn't a better airplane,
nor am I denying that composites might be a better way to build an
airplane, just saying (at the risk of flogging the proverbial dead
horse) that the comparison , while it is as good as you're going to get,
is still flawed.

ALC- Hide quoted text -

- Show quoted text -

Agreed, you will always be dealing with differences that can skew the
comparison including differing prop combinations. Another good
comparison might be VANS RV-10 which does use a metal wing. The
performance numbers on that plane are also better than the
Commanchee. The RV-10 is probably a good comparison to the Ravin
since both would probably be about the same weight, size, and use the
same engine. The RV-10 with the O-360 combination might be a good
comparison to the commanchee.

"BobR" wrote in
ups.com:

On Mar 28, 4:35 pm, Alphonse Le Creur wrote:
"BobR" wrote
roups.com:





On Mar 28, 12:40 pm, Alphonse Le Creur wrote:
"BobR" wrote in
news:1175092590.355514.234030 @y80g2000hsf.googlegroups.com:

On Mar 28, 8:51 am, Nathan Young
wrote:
I have a Cherokee 180, with the short hershey bar wing. While
I love the plane, I always wish it could go a bit faster, or
use a bit less fuel to get to my destination.

I have followed the composite homebuilding movement for many
years, and am amazed at the sleekness of a composite wing. The
wings on
most
composites tend to be the complete opposite of a Hersey bar
wing: high aspect ratio, low thickness, no rivets, no screws
for fuel tanks,smooth curves faired into airframe, and
streamlined landing
gear
structure.

So my question: How much drag does a wing on a Hersey Bar
Cherokee generate, and and hypothetically speaking, how much
faster could the plane go if it was retooled with a sleek,
composite wing?

I can't remember if it was Kitplanes or SportAviation that had a
recent article on a Piper knockoff being produced as a kitplane
in South Africa. That might be a good starting point for the
difference in performance between the different planes as well
as a discussion of the differences in design and construction.
Much of the difference has to do with better airfoil designs
being used but also weight differences.

Well, that airplane is "inspired" by the Commanche and it's really
just comparing apples and oranges since there are so many other
differences in the two airplanes, but having said that, it's
better than comparing a cherokee to a Cozy, for instance..

In any case, the Ravin Commanche is
herehttp://www.saravin.com/review.htm

ALC- Hide quoted text -

- Show quoted text -

It's about as close a comparison as can be made. I am building the
KIS Cruiser which uses a hershey bar style wing as well but the
airfoil is different. The comparison from a performance standpoint
is much faster than the Commanche for the same power (180 hp). The
difference must be attributed to several differences beyond just
the wing, weight being the most obvious.

Well, the Ravin is actually a couple hundred pounds heavier than the
original Commanche empty and has a higher gross. It also has a much
smaller fuselage cross section.
I'm certainly not saying that the Ravin is not a better airplane. It
is. I'd sure like to have one! I'm just saying that while it is
probably one of the better comparisons, no absolute conclusion may be
made from it. There's too many other things going on there. The
Commanche uses what was a then state of the art NACA 6 series laminar
flow airfoil. It was streets ahead of what was on any lightplane of
the time, but it's use was most probably not dictated by the material
of which it was made. I have no idea what the Ravin is using for an
airfoil. If Piper were to set out to make the same airplane again
today using aluminum for the wing, they could still build a more
efficient wing than they did in the fifties by simple virtue of the
fact that fifty years later there's been quite a lot of innovation in
airfoils, structures and what not. Again, I'm not saying that the
Ravin isn't a better airplane, nor am I denying that composites might
be a better way to build an airplane, just saying (at the risk of
flogging the proverbial dead horse) that the comparison , while it is
as good as you're going to get, is still flawed.

ALC- Hide quoted text -

- Show quoted text -

Agreed, you will always be dealing with differences that can skew the
comparison including differing prop combinations. Another good
comparison might be VANS RV-10 which does use a metal wing. The
performance numbers on that plane are also better than the
Commanchee. The RV-10 is probably a good comparison to the Ravin
since both would probably be about the same weight, size, and use the
same engine. The RV-10 with the O-360 combination might be a good
comparison to the commanchee.


Well, a shopping comparison, maybe, but the Ravin has a bigger engine
(unless you mean the baby Ravin with the fixed gear) so again it's
apples and oranges. I don't know, structural engineering isn't my thing
and I've never looked into the ins and outs of tupperware airplanes
anyway. can't build 'em because I can't even stand to be in a room with
the fumes and dust and I'm more of a biplane/round engine type anyway. I
was just pointing out what I saw was kind of a dead end comparison.
Still I wouldn't turn my nose up at one of those Ravins!




ALC

In article ,
"Montblack" wrote:

("Wayne Paul" wrote)
It is much easier to build a laminar flow airfoil and complex shaped
wing to fuselage transition using composite construction. These wing have
a better lift to drag ratio. The decrease in drag aerodynamic drag of
the wing and static drag decrease associated with the wing/fuselage
transition allow faster speeds.


Can you reword this (for some of us "Huh?" lurkers) especially the wing to
fuselage transition part?

How good/efficient are Cherokee, Ercoupe, Cessna (aluminum & rivet) wing
root fairings vs. what could be achieved with complex composite shapes?

Same question with the wing shape - to hold up the same plane, ALL else
being equal?

So ballpark - how much more efficient would the use of complex composite
construction (wings and wing root transition areas) make these planes - ALL
else being equal?

Paul,
Go to airliners.com or any other site that will have "new" and "old"
airplanes. Pay particular attention to the wing-fuselage junction.
On the old airplanes, the fuselage seems to be just stuck to the wing.
On the new aiplanes, there are HUGE fillets fore and aft of the wing.
This really became a design consideration in the mid-1980's.

On Wed, 28 Mar 2007 13:51:57 GMT, Nathan Young
wrote:

I have a Cherokee 180, with the short hershey bar wing. While I love
the plane, I always wish it could go a bit faster, or use a bit less
fuel to get to my destination.

With about 375 hours in a Cherokee 180 and about 1200 in a straight
tail Beechcraft (Debonair) my take it this.

I like the 180 better than the Archer even though the Archer lookes
nicer with that taper wing and is a bit faster.

That constant cord, thick wing makes the 180 one of the most docile
airplanes you will find and it still has pretty good performance. Very
good climb and tremendous at getting into short fields with the steep
descent.

I can't see as a gallon or two over the range of the Cherokee, or
Archer is going to be worth worrying about....although we did have one
guy land ours with 1/2 gallon of fuel on board (all in one tank). He'd
flown the same trip (St Louis Mo to Midland, MI) so many times he
never paid any attention to the time and this time coming home he had
one bodatios head wind. (and a LOT OF LUCK!

Having flown Both the 180 and the Deb in torrential rain I can say I'd
much prefer a thicker windsheild to prettier wings. It was deafening!

As to fuel, we flew the 180 down to Muncie IN to pick up the Deb. My
friend took off well ahead of me, but I passed him before we reached
Ft Wayne. I was back in Midland, had the Deb put away in the hangar
and was having a cup of coffee in the terminal building when I head
him call in. When they filled the Cherokee up, I found I had used
less than one gallon more to cover the same route at close to 190 MPH.

I had to ferry the Deb up to HTL to have some work done on the gear
which meant leaving it down. Now that's using gas. The speed was
about the same as the Cherokee but burning about 14 1/2 GPH.

I have followed the composite homebuilding movement for many years,
and am amazed at the sleekness of a composite wing. The wings on most
composites tend to be the complete opposite of a Hersey bar wing:
high aspect ratio, low thickness, no rivets, no screws for fuel

I'm glad you said most. I'm building a Glasair III and a high aspect
ratio it doesn't have. Wing span is a tad over 23' with a 4' wide
fuselage in the middle so that makes each wing about 9 1/2 feet long.
It also has almost 30# per square foot of wing loading on that tiny
wing but it sure does go. Built like a tank too. If you think the 180
has a steep descent you should fly a G-III once. :-)) Normal is about
2000 fpm power off.

tanks,smooth curves faired into airframe, and streamlined landing gear
structure.

So my question: How much drag does a wing on a Hersey Bar Cherokee
generate, and and hypothetically speaking, how much faster could the
plane go if it was retooled with a sleek, composite wing?

That's a diffiuclt question to answer because there are so many
variables. You could easily end up with a wing that could travel far
faster than the rest of the structure could handle. On the Cherokee
the landing gear presents a lot of drag. To maintain at least the
handleing characteristics of the Archer you probably ould not get much
faster than an Archer. To simply replace the wing with a composit one
of the same design would most likely make little difference.

All airplanes are a group of compromises. The 180 is the only plane
I've ever flown where I could put it into a full stall, hold the
elevator full up and still use the ailerons in turns. (with careful
application) Almost any changes are going to result in a plane that
is less forgiving. It's very difficult to hold the Deb in a stall
without having it drop a wing. It's like balancing on a tight rope and
if you touch an aileron to raise a wing, that wing will instead go
down (abruptly) and you will most likely roll into a spin.

Speed comes at a price.


Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com

("john smith" wrote)
On the new aiplanes, there are HUGE fillets fore and aft of the wing. This
really became a design consideration in the mid-1980's.


Wheel pants, gap seals, ....and HUGE new fiberglass fillets (fore and aft).
Are they part of everyday speed-mod packages?

If so, what is the "anecdotal" gain, after installing (just) them?

I've read reports on wheel pants, on gap seals, and on Power Flow exhaust
systems, but not on aftermarket fillets for the GA fleet.

http://www.powerflowsystems.com/


Montblack
airliners ...net? :-)

Hi,

I don't see why a composite should be heavier:

For carbon composite, the Young's modulus is ~70GPa for a density of 1.3
g/cm3. Al has the same Young's modulus but twice the density (2.7
g/cm3). For glass the strength is about half but again the weight is
halved too -so it's not a gain over Al. I think the composites excel in
their lack of rivets and joining pieces tho...

Cheers MC


Composites are indeed heavier than metal but if carbon fiber is used, not
that much heavier. The real payoff is in the extremely smooth surfaces that
promote natural laminar flow. The payoff is huge across the entire speed
spectrum but highest at the low speed end where the flow is less stable and
more likely to separate if the wing surfaces are rough..

Bill Daniels


"Wayne Paul" wrote in message
...
I have helped rig many sailplanes, both composite and conventional aluminum
construction. In almost every case the metal wing are lighter then the
composite. (1-35 and HP-18 aluminum wings are lighter then ASW-20, ASW-27,
and LS-6 composite wings.)

It is much easier to build a laminar flow airfoil and complex shaped
wing to fuselage transition using composite construction. These wing have
a better lift to drag ratio. The decrease in drag aerodynamic drag of
the wing and static drag decrease associated with the wing/fuselage
transition allow faster speeds.

Wayne
http://www.soaridaho.com/



"cavelamb himself" wrote in message
news
At these speeds I suspect surface condition is a small part of the
overall drag.

However!

If the new wing were a couple hundred pounds lighter, then you'd
see some inprovement in speed.

It takes power to stay aloft.

The heavier the plane, the more power is required just to stay up.


Lighter is mo' betta!


Richard



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On Wed, 28 Mar 2007 23:11:29 -0500, "Montblack"
wrote:

("john smith" wrote)
On the new aiplanes, there are HUGE fillets fore and aft of the wing. This
really became a design consideration in the mid-1980's.


Wheel pants, gap seals, ....and HUGE new fiberglass fillets (fore and aft).
Are they part of everyday speed-mod packages?

If so, what is the "anecdotal" gain, after installing (just) them?

I've read reports on wheel pants, on gap seals, and on Power Flow exhaust
systems, but not on aftermarket fillets for the GA fleet.

http://www.powerflowsystems.com/

Knots2U sells a wing/fuselage fairing.

http://knots2u.com/28WR.htm

I have it on my Cherokee, but cannot discern the exact performance
gain as it was added in conjunction with a number of other mods.

On Mar 29, 2:10 am, DR wrote:
Hi,

I don't see why a composite should be heavier:

For carbon composite, the Young's modulus is ~70GPa for a density of 1.3
g/cm3. Al has the same Young's modulus but twice the density (2.7
g/cm3). For glass the strength is about half but again the weight is
halved too -so it's not a gain over Al. I think the composites excel in
their lack of rivets and joining pieces tho...

Cheers MC





Composites are indeed heavier than metal but if carbon fiber is used, not
that much heavier. The real payoff is in the extremely smooth surfaces that
promote natural laminar flow. The payoff is huge across the entire speed
spectrum but highest at the low speed end where the flow is less stable and
more likely to separate if the wing surfaces are rough..

Bill Daniels

"Wayne Paul" wrote in message
...
I have helped rig many sailplanes, both composite and conventional aluminum
construction. In almost every case the metal wing are lighter then the
composite. (1-35 and HP-18 aluminum wings are lighter then ASW-20, ASW-27,
and LS-6 composite wings.)

It is much easier to build a laminar flow airfoil and complex shaped
wing to fuselage transition using composite construction. These wing have
a better lift to drag ratio. The decrease in drag aerodynamic drag of
the wing and static drag decrease associated with the wing/fuselage
transition allow faster speeds.

Wayne
http://www.soaridaho.com/

"cavelamb himself" wrote in message
news At these speeds I suspect surface condition is a small part of the
overall drag.

However!

If the new wing were a couple hundred pounds lighter, then you'd
see some inprovement in speed.

It takes power to stay aloft.

The heavier the plane, the more power is required just to stay up.

Lighter is mo' betta!

Richard

------------ And now a word from our sponsor ---------------------
For a secure high performance FTP using SSL/TLS encryption
upgrade to SurgeFTP
---- Seehttp://netwinsite.com/sponsor/sponsor_surgeftp.htm ----- Hide quoted text -

- Show quoted text -

From wha I have read in the past, the major reason for lack of weight
reduction in composite structures results from differences in the
design standards. The design standard for metal wings is based on a
1.5 times specification. Thus, a wing rated for 3g's is designed for
4.5 g's. The standard used for composite wings has been set at 2
times specification. The composite wing rated for 3g's is designed
for 6g's and as a result any weight savings is lost to the extra
strength. The difference in the standards was ment to compensate for
perceived quality variations in composite contstruction techniques.

The composite construction makes a big difference in making
possible the use of supercritical airfoils. These airfoils need a
slick surface, so much so that flying in rain degrades their
performance to the point that they can become dangerous. You'd never
build a wing like that using sheet metal and rivets. Just the lap
joints or any waviness in the aluminum would cause trouble.
Composite looks nice, but I became allergic to some of that
stuff way back in the '70s. And in the cold winters here I've seen it
crack and delaminate. My preference is for something more resistant to
everyday life. Kinda like my old truck.

Dan