Exactly! And yet, despite an aspect ratio of 36 (21 M) vs 29 (18 M), the 21 M performance is
almost identical, according to the chart. How can that be?

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorg...ad-the-guide-1[/quote]

Hi - The polar graph on the JS website starts at a higher airspeed than most others - the major performance difference between spans occurs around the thermalling speed region which is missing in the graph. I can attest from flying JS1's in both spans against others that there is very little noticable performance difference at similar wingloadings at cruise speeds.
That said I believe the ballasted 21m JS1 is an underrated weapon and the JS2 will be even better. The JS5 will be in a class of its own.