Front-Electric Sustainer Gliders

Is the power sufficient for independent take off? Or alternatively, how long can this run at constant altitude in a typical glider?

Also see

- https://en.m.wikipedia.org/wiki/Front_electric_sustainer

- about LAK-17c https://m.youtube.com/watch?v=T-a3hya3ywQ

I can't find it now, but I seem to remember reading about a company that was adding solar cells to the wings of their self-launching electric sustainer glider. The solar panels didn't generate anywhere near enough power to sustain cruising power, but the idea was that they could replenish the energy consumed by self-launching in the duration of a typical flight.