wrote:
On Jan 3, 7:36 pm, Eric Greenwell wrote:
You can get the ASW 27 B curve from Schleicher's site and draw your own
line. It's guess, because the curve only goes to 210 kph, but the curve
I drew "looks right", using the 55.6 kg/m2 line as the starting point.
I'm sure it's not 10:1, but certainly between than 15:1 and 20:1.

Based on a look at some actual flight logs I'd guess that at redline
(151 kts) the ASW-27 would get something like 16:1. A quadratic curve
fit to the factory polar shows 20:1. If you extrapolate out to the
aforementioned 160kts (above redline for the -27) the quadratic curve
off the factory polar yields 18:1, My guess at reality would be more
like 14:1 at that speed (and 11.5 lbs/sqft). We'll see, but I doubt
the Duckhawk will have the same performance as the -27 at equivalent
wing loadings and I also doubt it'll be able to get to much above 10
lbs/sq ft wing loading because it starts out 230 lbs lighter empty and
the wing is too small to carry enough water ballast to get above 10
lbs. Soooo, if I had to bet I'd guess an L/D below 15:1 rather than
above 15:1 at max gross and 160 kts.

Even 20:1 is enough to cruise in strong lift without gaining altitude,
so I think the main point has been established - that you probably
don't gain much by trying to optimize a design for wave XC in the 15
meter class.

9B


But a 200 knot redline would sure make for an impressive flyby!