Glider Shapes

Gary Emerson wrote:
brtlmj wrote:
Standard control system layout (no parallelogram stick)

Excuse my ignorance... what is a parallelogram stick?

Bartek

The standard configuration has the stick pivoting forward and aft as
well as side to side. The parallelogram stick SLIDES forward and aft,
but pivots side to side. Some people really like it, but it's a minor
design by numbers.

Excuse any appearance of anality, but the parallelogram sticks I've seen
in Mosquitoes did not *slide* forward and aft. Rather they moved
forward and aft on a 3-sided parallelogram linkage (having beautiful
bearing movements). There were 2 always-parallel, essentially vertical
pieces connected at the top by an always-horizontal piece. (Imagine a
cereal box end-on, long sides horizontal. [Approximate] mid-pitch
position would be short sides vertical. Forward would squash the 'gram
to the left (say); aft to the right.) I can't remember if the
Mosquito's hand grip attached to a 3rd upright welded to the top
horizontal, or extended aft and up from an extension of it.

Parallelogram geometry is such that vertical acceleration forces exerted
by one's hand in turbulence are muted due to near 90-degree interior
angles of the parallelogram in normal flight regimes. I thought it
quite elegant; it's certainly more 'turbulence benign' than a sharply
aft-pointed stick or S-curved stick, where positive G induces aft stick.
(Tangentially, George Moffat attributes at least one fatality to an
owner-added S-curved stick; apparently a strong negative gust at low
altitude and high speed resulted in an inadvertent pitch-down.)

My Zuni's side stick (and the sole HP-18 example I've seen) had sliding
pitch implementations rather than pivoting. Every sliding pitch
implementation I've played with (think Cessna/Piper power plane) has had
MUCH more pitch friction than that in Mosquito parallelograms.
Completely different concepts...

Regards,
Bob W.