$1 billion BMS Ooops...

Hank Nixon wrote on 3/4/2021 8:56 AM:
On Wednesday, March 3, 2021 at 11:53:15 PM UTC-5, wrote:
For the moment the big limitation seems to me to be weight. I looked hard at the AS33 electric. You get one launch to 2000' and then 9000' of climb to get home. For that, it's really hard to get off the ground at less than 10 lbs/ft2 empty, and 10.5 in 15 m mode. Gas has a wonderful energy density.. I'm surprised some sort of hybrid doesn't make sense, gas to recharge a smaller battery, then eliminate the drive elements with an electric motor. But I presume they worked the numbers on this.

John Cochrane BB
Hybrid, at best, would provide no benefit in weight and the complexity of both solutions added together.
The problem the manufacturer's have is that they know the users expect to launch at max weight and have acceptable safety margins at launch.
This requires powerful motors having high consumption. Oh- and we want long range for retrieves.
All this adds up to big batteries.
Now insert this into an airframe designed for high wing loading and IGC specified maximum mass.
You end up with a glider not suitable for eastern US, nor most of Europe.
Waiting for new batteries that will solve this problem is a fools errand.
Maybe manufacturers should consider 2 options on batteries. 1/2 the battery in the '33 would save somewhere around 65 lb by my estimate. On a 107 sq ft glider, that is a big deal.
I'm looking now at electric 29E possibility. With the system I have in the '24E(L) I would expect a launch and around 3000 feet of additional retrieve climb from a system that would add about 40 lb to the weight of the 29E. With 25kw available at launch I see as a dry self launch only ship.
FWIW
UH

The JS3 RES batteries are set up like an FES glider, even though it's a mast mounted motor
system: two batteries can be carried in the motor bay, but only one is required for operation.
They are about 50 lbs each. Being able to remove and charge them elsewhere should be a great
convenience.

--
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