Richard Johnson's Report on the Sparrowhawk

Could someone give me a synopsis of Richard Johnson's test and opinion of
the Sparrowhawk from his presentation at the 2005 SSA Convention?

skysailor wrote:
Could someone give me a synopsis of Richard Johnson's test and opinion of
the Sparrowhawk from his presentation at the 2005 SSA Convention?

Raved in particular about smoothness of wing skins (smoothest he's ever
measured, and this one was several years old). Laminar flow nearly all
the way to the trailing edge, top and bottom. Measured performance less
than expected (~29:1 LD), taped on his trademark sheet aluminum wing
fillets, performance noticeably better (~31.5:1), figures more
improvement with properly designed fillets. Very impressed overall.

Marc

On Sun, 20 Feb 2005 09:38:30 GMT, Marc Ramsey
wrote:

Raved in particular about smoothness of wing skins (smoothest he's ever
measured, and this one was several years old). Laminar flow nearly all
the way to the trailing edge, top and bottom. Measured performance less
than expected (~29:1 LD), taped on his trademark sheet aluminum wing
fillets, performance noticeably better (~31.5:1), figures more
improvement with properly designed fillets. Very impressed overall.

Did he mention possible errors in his measurement?

7 points of missing L/D compared to the manufacturer's numbers is a
universe (and looks extremely low for the Sparrowhawk's aspect ratio).


Bye
Andreas

Andreas Maurer wrote:
7 points of missing L/D compared to the manufacturer's numbers is a
universe (and looks extremely low for the Sparrowhawk's aspect ratio).

Well, any L/D claims by a first time sailplane designer probably have a
large component of optimism. On the other hand, getting 32:1 out of an
11 meter glider (with a cockpit even fairly large people can fit into)
is a pretty decent first effort...

Marc

The Sparrowhawk people seemed very adament at the convention that
Johnson was wrong.... Perhaps someone else can do another test. I
know that the rumor is it will keep up with a Libelle.... suggesting an
L/D around 36.

Earlier, Andreas Maurer wrote:

...extremely low for the Sparrowhawk's
aspect ratio).

Well, if they didn't have to hang a person-sized fuselage from that
wing, I'd have to agree. Pity people have to be so... so unscalable.

Kevin Christner wrote:
The Sparrowhawk people seemed very adament at the convention that
Johnson was wrong.... Perhaps someone else can do another test. I
know that the rumor is it will keep up with a Libelle.... suggesting an
L/D around 36.

Performance measurement by rumor, always superior to actual tests 8^)

Marc

Wingspan counts a lot regardless of the airfoil.
"Bob K." wrote in message
oups.com...
Earlier, Andreas Maurer wrote:

...extremely low for the Sparrowhawk's
aspect ratio).

Well, if they didn't have to hang a person-sized fuselage from that
wing, I'd have to agree. Pity people have to be so... so unscalable.

"Kevin Christner" wrote in message
ups.com...
The Sparrowhawk people seemed very adament at the convention that
Johnson was wrong.... Perhaps someone else can do another test. I
know that the rumor is it will keep up with a Libelle.... suggesting an
L/D around 36.


Dick Johnson isn't wrong.

Bill Daniels

At 03:30 21 February 2005, Bill Daniels wrote:

Dick Johnson isn't wrong.

Wasn't there some discrepencies in Johnson's measurements
of the LS4? Which was the re - tested. Anyway max L/D
is one of the least important measurements - what is
the polar like?