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

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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.

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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 :-)