kinsell wrote on 3/16/2021 11:39 AM:
On 3/16/21 12:05 PM, Eric Greenwell wrote:
Craig Reinholt wrote on 3/16/2021 7:57 AM:
One issue not discussed is the duration / altitude of the launch. At Ely, and other sites
(Williams is one), the launch may run well over 20 minutes and altitude gain over 3000 feet
hunting for lift. The numbers supplied by the manufacturers are for a 1500' gain under 10
minutes. That difference will put a severe dent on the retrieve distances.
Craig
That hasn't been my experience at Ely, where a 2000' launch has almost always done the job,
but maybe I'm just lucky :^)* Williams is a special case, and some FES will undoubtedly have
to take tows just to get to the soaring. It shouldn't be a problem for electrics with 50+
mile range. Note that "the numbers" vary greatly between electric gliders, with some older
FES gliders having very limited climbs, and the newer mast-mounted motor systems by
Schleicher, Jonkers, and others offering 9,000'-13,000' climbs.
Well the Antares was supposed to have 10K feet climb capability, but in reality it was a whole
lot less.* That shows the danger of* comparing real life performance of existing products with
spec sheets of future products.* Don't suppose you went to Poland to verify the performance
numbers?
A whole lot of experience and development has been gained since the Antares debut 18 years ago,
so I'm willing to accept the current claims by Schleicher, Schmepp-Hirth, and Jonkers. We don't
have flight reports for production GP15 gliders, but the power performance numbers on the spec
sheets are conservative when compared to other manufacturers' claims, so I am also willing to
accept GP's numbers as being close to reality.
I did not go to Poland, but dealer (Tom Holloran) did go to Poland and fly a GP15. Apparently,
he thought it was a very good glider, as he became the dealer, and one of the first few will be
his glider.
--
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