Somebody Terrified of Compound Curves ---- Or Just Lazy

http://members.iinet.net.au/~steele2...rs/image4.html

Check out the butt-ugly wheelpants, looking to be cobbled up by an
apprenticed carpenter who didn't make it through his apprenticeship.

On Sat, 18 Oct 2003 10:20:53 -0400, "Larry Smith"
wrote:

http://members.iinet.net.au/~steele2...rs/image4.html

Check out the butt-ugly wheelpants, looking to be cobbled up by an
apprenticed carpenter who didn't make it through his apprenticeship.

To me, it looks more like he was just trying to save a lot of time vs.
making a set of compound-curve male or female molds, or save a bit of money
vs. buying ready-made pants.

If I were to "reverse engineer" the pants from the photo, it looks like he
made a male mold from a block of foam (or a stack of plywood) cut to the
basic outline, routed the outer edges, ran the assembly vertically through
a bandsaw to add a bit of curve to the sides on the front and back, then
sanded it smooth. A heck of a lot less time than carving up a classic
teardrop shape in three dimensions.

They probably wouldn't look good scaled up, but on small, fat gyro wheels,
I think they look all right. Workmanship, judging from that low-resolution
photo, looks fine.

Ron Wanttaja

"Larry Smith" wrote in message
...
http://members.iinet.net.au/~steele2...rs/image4.html

Check out the butt-ugly wheelpants, looking to be cobbled up by an
apprenticed carpenter who didn't make it through his apprenticeship.

That woulda' been a good flame Latchless except for the fact that the
photo shows a nice looking gyro. I can see why you'd be miffed
though.... it's finished, and there's something holding the doors shut.

Wayne

"Ron Wanttaja" wrote...
On Sat, 18 Oct 2003 10:20:53 -0400, "Larry Smith"

wrote:

http://members.iinet.net.au/~steele2...rs/image4.html

Check out the butt-ugly wheelpants, looking to be cobbled up by an
apprenticed carpenter who didn't make it through his apprenticeship.

To me, it looks more like he was just trying to save a lot of time vs.
making a set of compound-curve male or female molds, or save a bit of
money
vs. buying ready-made pants.

If I were to "reverse engineer" the pants from the photo, it looks like
he
made a male mold from a block of foam (or a stack of plywood) cut to the
basic outline, routed the outer edges, ran the assembly vertically
through
a bandsaw to add a bit of curve to the sides on the front and back, then
sanded it smooth. A heck of a lot less time than carving up a classic
teardrop shape in three dimensions.

They probably wouldn't look good scaled up, but on small, fat gyro
wheels,
I think they look all right. Workmanship, judging from that
low-resolution
photo, looks fine.

The pants look fine but that gyro needs a horizontal stabilizer and the
thrust line lowered...

Check out the butt-ugly wheelpants...

-----------------------------------------------

Dear Larry,

Check out Leeon Davis' DA-9. Makes your example look pretty :-)

To me, the example you've cited looks pretty smart. Lotsa folks, perhaps a
majority, confuse streamlining with something slicker than snot on a door knob.
A more practical appraoch for the typical homebuilder is to compare the faired
vs the un-faired drag.

A simple fairing such as the one used by Leeon reduces the drag of the wheel by
about 90%, weighs only a few ounces and takes only a few minutes to make,
corners and all :-) Or you can spend lotsnlotsa $ and lots & lots of time to
turn out one of those oh-so-perfect, cream your jeans kinda curves... that
reduces the drag by 95% and weighs ten pounds.

I've noticed that the most aerodynamically efficient fairings, and those which
weigh the least, are the ones installed on all those airplanes that never get
built :-)

If it flys, I can live with butt-ugly because there's always a chance I'll find
the time & money to pretty it up.

-R.S.Hoover

(Veeduber)

Hi Veeduber,
I would like to access the info to build the
Davis fairings. Where can I find it?
Thanks,
Shelly

"Veeduber" wrote in message
...
Check out the butt-ugly wheelpants...

-----------------------------------------------

Dear Larry,

Check out Leeon Davis' DA-9. Makes your example look pretty :-)

To me, the example you've cited looks pretty smart. Lotsa folks, perhaps
a
majority, confuse streamlining with something slicker than snot on a door
knob.
A more practical appraoch for the typical homebuilder is to compare the
faired
vs the un-faired drag.

A simple fairing such as the one used by Leeon reduces the drag of the
wheel by
about 90%, weighs only a few ounces and takes only a few minutes to make,
corners and all :-) Or you can spend lotsnlotsa $ and lots & lots of
time to
turn out one of those oh-so-perfect, cream your jeans kinda curves... that
reduces the drag by 95% and weighs ten pounds.

I've noticed that the most aerodynamically efficient fairings, and those
which
weigh the least, are the ones installed on all those airplanes that never
get
built :-)

If it flys, I can live with butt-ugly because there's always a chance I'll
find
the time & money to pretty it up.

-R.S.Hoover

All well and good but I watched Mike Arnold make beautiful wheelpants for
his AR-5. The procedure was more complicated than usual but not as bad as
you would expect and verrrrrrrry light. They were absolutely the lowest in
drag because they were offset from the landing gear strut and followed the
Hoerner rules. If I were making a set, and I have already made one set
still flying and proud of their compound curves, I would follow the rules
Arnold cites and have at it. I wouldn't want to behold myself in the
mirror and admit I had made some as repulsive as those on that
pitiful-looking gyrogoose.

But then, Veeduber, gustibus est non disputandum. Taste is not a matter to
be disputed.

I would like to access the info to build the
Davis fairings. Where can I find it?

---------------------------------------------

Hi Shell,

I donno. Give Leeon a call?

I took a look at that picture of the DA-9 when it was on the cover of 'Sport
Aviation,' shouted 'Cresent City!' (which is real close to that other place),
went out to the shop and made some.

Sight of the things triggers an instant negative reaction from the Aesthetics
Committee. Leaves them muttering ungrammatical Latin whilst peering down
several yards of nose. But aerodynamically these ugly ducklings are quite
pleasing to the wind.

-------------------------------

Got a tin can? One end cut out? Okay, turn it over. Look at the BOTTOM of
the tin can. Now imagine the bottom of the can is a chubby little asymmetic
airfoil.

Bottom don't have to be flat. Viewed from the side, imagine the bottom has a
positive camber, about like a 4400 series airfoil.

Got the idea?

Make yourself a form block for the plan-form, as viewed looking down on the
thing, whack it out giving yourself enough flange to set a rivet. Flute it or
notch it, your choice.

Sides are just a single piece of flat stock, long enough to fold around the
thing, come together at the tail. (I needed a strip almost four feet long and
longer probably would have been better.) Devote some time to the supports.
(I'm looking at something under 100kts, not a lot of aerodynamic load.) Rivet
it together, make a 'liner' out of .010 or roof flashing or whatever, add a
lower skin or stiffen the nose & tail by injecting a little foam. (Won't be
much good if it collects mud on take-off :-) Outboard side, make up a dummy nut
(if you got a couple of threads), use a handful of rivenuts or whatever to
stabilize the thing. (Be a good idea to use a doubler and real nut-plates on
the inboard side.)

If it comes off, make it stronger :-) If it weighs more than a few ounces (for
an 11" diameter wheel) you're probably doing something wrong :-) ... or flying
faster than me.

In theory, the constant curve of a compound surface will have a lower Cd but in
fact, if a corner has a good 'fineness' ratio, the result is pretty close to
the theoritcal value for a faired curve. There's a couple of TR or TN's on
this in the NACA archives, the only thing is they are referring to RIBS rather
than distinct corners. So call it a rib, if you wish. Or a wing-tip... on
edge :-)

Doesn't look like a tear drop but it's one hell of a lot cleaner than a bare
wheel.

-R.S.Hoover

PS -- got some SMOOTH road near your house? Smooth STRAIGHT road? (Friendly
cops help, too :-) You can develop some pretty good low-speed drag data just
rolling down the road, assuming you can bolt stuff to the top of your vehicle
(they don't like you sticking things out to the sides). I've used the local
railroad tracks (!!) to stress-test landing gear and a stretch of I-15 as a
kind of full-scale, low-speed solid concrete wind tunnel, and there's half a
dozen dry lake beds just over the hill that have served as temporary Muroc's.
But please don't mention it to anyone. That's called 'experimenting' and the
EAA is DEFINITELY against that sorta thing :-)

Obviously, you fellas have never built a flying machine from bamboo,
polyethylene plastic, duct tape and good 'ol office staples. Bamboo butterfly,
Batso, Conduit Condor, or my own personal adaptation / experiment... The Stormy
Petrel 2A!

Harry