Hershey bar wing vs composite wing - how much drag? [Archive]

Dave Butler

March 28th 07, 03:07 PM

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.

As a former PA28-180 owner, I can certainly agree with that.

> 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.

I'm no aerodynamicist, but I have a usenet-opinion. I think at Cherokee
airspeeds the effect of the screw and rivet heads is probably unmeasurable.

I'm not sure whether you're using 'composite' to mean the material from
which the wing is constructed, or the blending of different airfoil shapes.

I don't think the construction material has any effect on the
aerodynamics, but 'composite' materials may make it more economic to
manufacture complex shapes, and may reduce the weight of the resulting
structure.

If you are referring to blended airfoil shapes, look at the difference
between the fat-wing Pipers and the Archer II, Arrow II, etc.

> 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'm not volunteering to do the research, but I think with a little (or a
lot) of googling you can find the NACO airfoil on which the
constant-chord fat-wing Piper wing is based, and the NACO report has a
lot of detail about the characteristics of that airfoil. I've looked it
up before, but I've lost the reference.

Not news to you I'm sure, but there is more to wing airfoil choice than
minimizing drag.

BobR

March 28th 07, 03:36 PM

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.

cavelamb himself

March 28th 07, 03:42 PM

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

Wayne Paul

March 28th 07, 04:21 PM

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
thlink.net...
> 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

Bill Daniels

March 28th 07, 04:46 PM

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.

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
> thlink.net...
>> 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
>
>

Robert M. Gary

March 28th 07, 05:25 PM

On Mar 28, 6:51 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?

A fast Cherokee is also known as a Mooney C model.

-Robert

john hawkins

March 28th 07, 06:44 PM

According to my copy of Aerodynamics, Aeronautics and Flight mechanics By
McCormick pub by Wiley 1979 page 192.
"The rectangular wing used on many light single-engine aircraft, the induced
drag is seen to be about 6% or higher than that for the elliptical wing for
aspect ratios of 6 or higher"

The elliptical wing produces the minimum induced drag.
OTOH its dam all expensive to manufacture in sheet metal

"Nathan Young" > wrote in message
...
>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?
>
>

Philippe Vessaire

March 28th 07, 07:26 PM

Nathan Young wrote:

> 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?

You may take the other side of your question.

You choose a composite plane (ie Lancair) with the same engine.
You take the 75% cruising speed of the lancair (V-lancair)
You take the Cherokee 75% cruising speed (V-cher)

If you want the same speed for your plane, you need more HP

The formula is HP=180 * (V-lancair/ V-cher)³

You may do the reverse: how many HP the lancair need for the Cherokee
speed....

You know the cost of drag....

But don't think all drag is from wing, part of drag is from fuselage and
a roomy fuselage will generate more drag.
But the comfort is in roomy fuselage

By
--
Volem rien foutre al païs!
Philippe Vessaire Ò¿Ó¬

Blanche

March 28th 07, 08:30 PM

Robert M. Gary > wrote:
>
>A fast Cherokee is also known as a Mooney C model.

Hm...I always thought "fast cherokee" was an oxymoron...

And yes, I own a cherokee 180. Would I like faster? Sure! Wouldn't
everyone?

Montblack

March 28th 07, 09:09 PM

("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?

WAG - same power, weight, fuselage, etc - what improvements would these
planes see in speed, climb, stall, or fuel burn numbers?

Thanks.

Montblack

Robert M. Gary

March 28th 07, 10:10 PM

On Mar 28, 12:30 pm, Blanche > wrote:
> Robert M. Gary > wrote:
>
>
>
> >A fast Cherokee is also known as a Mooney C model.
>
> Hm...I always thought "fast cherokee" was an oxymoron...
>
> And yes, I own a cherokee 180. Would I like faster? Sure! Wouldn't
> everyone?

I think part of my point is that the price of the 180 and the M20C are
pretty close. I'm not sure why people choose the 180 when its a good
30 knots slower on the same fuel burn.

-Robert

Gig 601XL Builder

March 28th 07, 10:19 PM

Robert M. Gary wrote:
> On Mar 28, 12:30 pm, Blanche > wrote:
>> Robert M. Gary > wrote:
>>
>>
>>
>>> A fast Cherokee is also known as a Mooney C model.
>>
>> Hm...I always thought "fast cherokee" was an oxymoron...
>>
>> And yes, I own a cherokee 180. Would I like faster? Sure! Wouldn't
>> everyone?
>
> I think part of my point is that the price of the 180 and the M20C are
> pretty close. I'm not sure why people choose the 180 when its a good
> 30 knots slower on the same fuel burn.
>
> -Robert

I agree with you but I'd bet insurance and the cost of up keep added because
of the retrac gear has a lot to do with it.

Mark Hansen

March 28th 07, 10:27 PM

On 03/28/07 14:19, Gig 601XL Builder wrote:
> Robert M. Gary wrote:
>> On Mar 28, 12:30 pm, Blanche > wrote:
>>> Robert M. Gary > wrote:
>>>
>>>
>>>
>>>> A fast Cherokee is also known as a Mooney C model.
>>>
>>> Hm...I always thought "fast cherokee" was an oxymoron...
>>>
>>> And yes, I own a cherokee 180. Would I like faster? Sure! Wouldn't
>>> everyone?
>>
>> I think part of my point is that the price of the 180 and the M20C are
>> pretty close. I'm not sure why people choose the 180 when its a good
>> 30 knots slower on the same fuel burn.
>>
>> -Robert
>
> I agree with you but I'd bet insurance and the cost of up keep added because
> of the retrac gear has a lot to do with it.
>
>

Not to mention I could fit in a 180, but not a Mooney (although that is
changing...)

Wayne Paul

March 28th 07, 10:30 PM

"Montblack" > wrote in message
...
> ("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?
>
> WAG - same power, weight, fuselage, etc - what improvements would these
> planes see in speed, climb, stall, or fuel burn numbers?
>
> Thanks.
>
>
> Montblack

Let me make this as simple as possible by simply giving you an example. My
HP-14 (http://www.soaridaho.com/Schreder/N990_Borah_Mt.JPG) has a 52 foot
wingspan. The wings were built with flush rivets and have been smoothed by
adding an epoxy/balloon mixture. This is mid 1960 construction techniques
using aluminum construction. My lift to drag ratio is around 36 to 1.
However, new modern sailplanes with composite construction and modern
airfoils that only have 15 meter (just under 50 feet) wingspan have glide
ratios of around 48 to 1.

So with both of my old HP-14 and an ASW-27 (http://tinyurl.com/8lecz) loaded
to have a gross weight of 800 lbs. At best glide speed my HP-14 would have
about 22 lbs of drag while the ASW-27 would have less then 17 lbs of drag..
So the ASW-27 is 30% more efficient then my 14. If my wings did not have
flush rivets and were not smoothed the difference would be even greater.

The same is true with power aircraft. Just compare the Flight Design CT
(http://www.flightdesignusa.com/) with a Cessna 152 or a Cirrus with any
earlier conventionally constructed aircraft of similar weight and
horsepower.

To take these in steps, the wing is the most important, the fuselage shape
is also important and the junction between the wing and fuselage. I am
familiar with a smooth wing metal sailplane that was re-winged with a modern
airfoil. The new wing, has the same area and span. The original
wing/fuselage combination produced a 38 to 1 glide ratio. The updated
combination produced a 42 to 1 glide ratio. That is a 10 percent
improvement. Going from a round riveted wing to a modern airfoil should
provide a 15+% improvement.

Wayne
HP-14 "6F"

Robert M. Gary

March 28th 07, 11:15 PM

On Mar 28, 2:27 pm, Mark Hansen > wrote:
> On 03/28/07 14:19, Gig 601XL Builder wrote:
>
>
>
>
>
> > Robert M. Gary wrote:
> >> On Mar 28, 12:30 pm, Blanche > wrote:
> >>> Robert M. Gary > wrote:
>
> >>>> A fast Cherokee is also known as a Mooney C model.
>
> >>> Hm...I always thought "fast cherokee" was an oxymoron...
>
> >>> And yes, I own a cherokee 180. Would I like faster? Sure! Wouldn't
> >>> everyone?
>
> >> I think part of my point is that the price of the 180 and the M20C are
> >> pretty close. I'm not sure why people choose the 180 when its a good
> >> 30 knots slower on the same fuel burn.
>
> >> -Robert
>
> > I agree with you but I'd bet insurance and the cost of up keep added because
> > of the retrac gear has a lot to do with it.
>
> Not to mention I could fit in a 180, but not a Mooney (although that is
> changing...)- Hide quoted text -
>
> - Show quoted text -

You do have to be a bit tall to fly a Mooney. I'm 6'4" and fit fine
but my partner is 5'10" and has a tough time reaching the rudders.

-Robert

Matt Whiting

March 28th 07, 11:33 PM

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

john smith[_2_]

March 29th 07, 12:39 AM

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.

Roger[_4_]

March 29th 07, 03:03 AM

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

Montblack

March 29th 07, 05:11 AM

("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? :-)

March 29th 07, 08:10 AM

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
>> thlink.net...
>>> 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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Nathan Young

March 29th 07, 01:31 PM

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.

BobR

March 29th 07, 03:40 PM

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
> thlink.net...
> >>> 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 ---------------------
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> - 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.

[email protected]

March 29th 07, 03:51 PM

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

cavelamb himself

March 29th 07, 04:29 PM

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
>

If strength were the only issue, you'd be right on.

But there is also the question of stiffness.

Composite structures tend to get strong enough long before they
get stiff enough.

Then there is the "margin of safety".
Metal and wood wings are designed to a 50% MS.
Composites tend to go to 100% extra.
That alone means more weight.

Richard

cavelamb himself

March 29th 07, 04:32 PM

Philippe Vessaire wrote:

> Nathan Young wrote:
>
>
>
>>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?
>
>
> You may take the other side of your question.
>
> You choose a composite plane (ie Lancair) with the same engine.
> You take the 75% cruising speed of the lancair (V-lancair)
> You take the Cherokee 75% cruising speed (V-cher)
>
> If you want the same speed for your plane, you need more HP
>
> The formula is HP=180 * (V-lancair/ V-cher)³
>
> You may do the reverse: how many HP the lancair need for the Cherokee
> speed....
>
> You know the cost of drag....
>
> But don't think all drag is from wing, part of drag is from fuselage and
> a roomy fuselage will generate more drag.
> But the comfort is in roomy fuselage
>
>
> By

And a LOT of the drag is from cooling the engine!
There is an ideal place for big gains.

Richard

Evan Carew

March 29th 07, 05:09 PM

BobR wrote:

>
>>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 main reason for the 2x standard has to do with the fiber alignment
(or rather misalignment) of the laminations in the spar. Since this is
the single heaviest, and most important component of the wing, its
construction is critical. Unfortunately, with traditional wet layup
techniques, perfect alignment of the fibers in the spar is not possible,
thus decreasing its strength. The obvious solution recommended in the
books is to increase the design over design to compensate.

Not too long ago, I saw that someone had solved this problem by using
small diameter, precured carbon-fiber rods as the core material for the
spar. This solves the disadvantages of the traditional techniques.

Wayne Paul

March 29th 07, 05:31 PM

"Evan Carew" > wrote in message
t...
> BobR wrote:
>
>>
>>>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 main reason for the 2x standard has to do with the fiber alignment
> (or rather misalignment) of the laminations in the spar. Since this is
> the single heaviest, and most important component of the wing, its
> construction is critical. Unfortunately, with traditional wet layup
> techniques, perfect alignment of the fibers in the spar is not possible,
> thus decreasing its strength. The obvious solution recommended in the
> books is to increase the design over design to compensate.
>
> Not too long ago, I saw that someone had solved this problem by using
> small diameter, precured carbon-fiber rods as the core material for the
> spar. This solves the disadvantages of the traditional techniques.

Jim Marske has been involved in sailplane construction for many years. I
believe he was one of the first to use carbon rods in the spar caps. Check
out his website for more information: http://marskeaircraft.com/

Aluminum wings can be "profiled" with performance results close to a
composite wing. (http://tinyurl.com/2r8b7d) The time involved is such a
project is normally 400+ hours.

Wayne
HP-14 N990 with profiled aluminum wings
http://www.soaridaho.com/Schreder/N990_Near_Arco.jpg

Richard Isakson

March 29th 07, 05:56 PM

"cavelamb himself" wrote ...
> 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.

Richard,

That's not really true for a light airplane. The only place weight shows up
in the drag equation, and thus the power equation, is in the induced drag
term.
But,because the wing on a light airplane is relatively large, the induced
drag at cruise is small. Cruise induced drag is lift coeffients squared
divided Pi e Aspect Ratio. Light airplanes cruise at small lift coeffients
of around 0.1 to 0.2. It can be shown that they will fly the farthest on a
pound of fuel at L/D max. Lift coeffients around 0.6 to 0.8. So, an
increase in airframe weight doesn't increase the cruise power requirements
very much.

Of course, an light airplane could be designed to fly at L/D max but the
wing would be tiny and you'd pay for it on the slow speed end. With a
single engine and relatively inexperienced pilots, it would be a handful at
slow speeds. Both the BD-5 and the Questar venture are examples of under
winged airplanes that have poor engine out safety records.

Where weight does show up is in climb performance. One of the things that
make an airplane "fun" is how well it climbs. You don't spend much time
there in a cross country flight, but a large high aspect ratio wing with
lots of power will give the pilot the feeling that the airplane is a good
flying airplane.

One of the problems I've had in the past is how much should a designer try
to protect a future user of a product? I've decided that a minimalist wing
is a bad design in the light plane market.

Rich

Dave Butler

March 29th 07, 06:29 PM

> And a LOT of the drag is from cooling the engine!
> There is an ideal place for big gains.

Yes, look at the difference in performance of the J model Mooneys vs.
the pre-J models.

Montblack

March 29th 07, 06:59 PM

("cavelamb himself" wrote)
> And a LOT of the drag is from cooling the engine!
> There is an ideal place for big gains.

Ercoupe, Cessna 172, Piper Warrior:
How much drag would be eliminated it the prop was spun from, say, a
(hypothetically capable) electric motor - of the same weight as the engine?
An electric motor that needs little of the cooling air (drag) required by
the gas engines.

WAG, is a LOT ...33%?

Whatever the guesstimated drag number settled on, what then would that
number mean in cruise speeds, or fuel burn? 10% improvement? 20%
improvement? 30%?

Montblack

Matt Whiting

March 29th 07, 11:20 PM

Kyle Boatright

March 30th 07, 01:20 AM

"Montblack" > wrote in message
...
> ("cavelamb himself" wrote)
>> And a LOT of the drag is from cooling the engine!
>> There is an ideal place for big gains.
>
>
> Ercoupe, Cessna 172, Piper Warrior:
> How much drag would be eliminated it the prop was spun from, say, a
> (hypothetically capable) electric motor - of the same weight as the
> engine? An electric motor that needs little of the cooling air (drag)
> required by the gas engines.
>
> WAG, is a LOT ...33%?
>
> Whatever the guesstimated drag number settled on, what then would that
> number mean in cruise speeds, or fuel burn? 10% improvement? 20%
> improvement? 30%?
>
>
> Montblack

You're on the right track if you can work with a semi-trailer sized battery
or a 500 mile extension cord. ;-)

KB