Why is there nothing better than a Discus 2a?

Chip Bearden wrote, On 1/4/2014 10:07 PM:
In addition to claimed incrementally higher performance, what the
later designs offered were optional 18m wingtips (although I'm not
sure how many owners opted for these), more crashworthy cockpits (in
the case of the D2 and LS 8; the ASW 24's already outstanding design
was the basis for the ASW 27, ASW 28, and ASG 29 fuselages) and
perhaps a bit easier, though not necessarily better, thermaling.

The ASH 26 also used the ASW 24 cockpit design concepts, as have all
succeeding Schleicher gliders (with improvements along the way, of
course). I don't think the ASH 25 incorporated the 24's concepts, as
it's design seems to pre-date the 24, and it flew first, about a year
earlier.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)

I'm not so sure there has been all that much recent aerodynamic improvements in glider design. Nothing as drastic as the transition between "classic" and laminar profiles.

Every new generation of laminar profiles has marginally improved the performance, but we seem to have reached a plateau where Boermans, the profile guru from Delft University, is looking towards boundary layer aspiration for a new leap forward. If successful, this will be costly.

It is much easier to improve the performance by 1) increasing the wingspan (within limits imposed by structural problems and maneuverability); 2) increasing the aspect ratio of the wing (within limits imposed by Reynolds number effects within a fixed wingspan).

The new "small open class" seems to correspond to an optimal compromise for the current generation of laminar profiles.

15 meter sailplanes seem to fall on the wrong side of the optimum. They are also less apt to be equipped with an engine due to the impact on their minimum wing loading. Their only reason of existence now seems to be their lower price. But you never know what the future will bring…

On Tuesday, January 7, 2014 3:22:15 PM UTC-5, wrote:
I'm not so sure there has been all that much recent aerodynamic improvements in glider design. Nothing as drastic as the transition between "classic" and laminar profiles. Every new generation of laminar profiles has marginally improved the performance, but we seem to have reached a plateau where Boermans, the profile guru from Delft University, is looking towards boundary layer aspiration for a new leap forward. If successful, this will be costly. It is much easier to improve the performance by 1) increasing the wingspan (within limits imposed by structural problems and maneuverability); 2) increasing the aspect ratio of the wing (within limits imposed by Reynolds number effects within a fixed wingspan). The new "small open class" seems to correspond to an optimal compromise for the current generation of laminar profiles. 15 meter sailplanes seem to fall on the wrong side of the optimum. They are also less apt to be equipped with an engine due to the impact on their minimum wing loading. Their only reason of existence now seems to be their lower price. But you never know what the future will bring…

That would depend on the definition of "optimum".
If the definition of "optimum" were to include reasonable weight single piece wings, glide angles in the high 40's, and wonderful handling, I'd say that there are many gliders in the fleet that would meet the definition and justify their "existance".
If the definition includes ability to add an engine and retain a reasonable minimum wing loading, then it would seem to move toward 18 meters with the associated increase in cost and complexity.
Either option uses airfoils that get 95% laminar flow on the bottom and somewhat beyond 60% on the top.
And price is a factor for some buyers.
FWIW
UH