World Contest - Open Class

On Thursday, November 24, 2016 at 10:07:51 AM UTC+1, Bruce Hoult wrote:
On Wednesday, November 23, 2016 at 11:25:53 PM UTC+3, Jonathan St. Cloud wrote:
Was looking over the entry sheet for WGC 2017. The open class seem dominated by 21 meter ships. Only two 23 meters (new generation open class) and four EB29. Nary a Nimbus 4 or ASW-22. Shame these beautifully ladies of the sky are not competitive with even the 21 meter birds. There is nothing like flying a 26.5 meter bird, they will stay in the sky on a breath of hot air. Their shape I find so much more alluring than the stubby wings of 21 meters or less.

As you allude, it depends on the conditions. The 25+ meter ships win easily if the lift is weaker than 1 knot. If you've got 2+ knots then 19m is superior, purely on polar, let alone manoeuvrability. And in stonking ridge or wave conditions 15m or less lets you have a higher Vne...

Not just Vne, the 15m polar at high speed is much better than the Open ships.

The evening session at the OSTIV Congress in Benalla on 11 January is
titled "Future of the Open Class" with Loek Boermans, Tilo Holighaus,
Attie Jonker, Axel Lange, Gerhard Waibel...

Not just Vne, the 15m polar at high speed is much better than the Open ships.

Are you shure about that? The modern Open class ships has the same wing load or even a little higher than most of the competitive 15m gliders. If you then add up that a high (Open) aspect ratio of the wing climbs better than a lower (15m) at the same wing load give us that an Open class ship will climb better and glide equally.

I would say that the extra wetted surface becomes a handicap at higher velocities. The influence of induced drag decreases with increasing velocity,and that's where the aspect ratio is a factor.

See: https://en.wikipedia.org/wiki/Lift-i...f_induced_drag

Read L as m*g. It is constant.