"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 -

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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