FES underpowered for 18m ship?

A real problem is putting the word "KISS" and "FES" is the same
sentence or indeed "KISS" and "electric propulsion".
There is nothing simple about electric motors powered by LiPo batteries.

On Tuesday, September 15, 2020 at 11:45:05 AM UTC+2, Dave Walsh wrote:
A real problem is putting the word "KISS" and "FES" is the same
sentence or indeed "KISS" and "electric propulsion".
There is nothing simple about electric motors powered by LiPo batteries.

The technology of the motor is very mature and much simpler than of a jet or a combustion engine, which has a direct impact on maintenance needs and on reliability. I agree that the batteries do add cost, complexity and fire hazard (until we find a better technology than LiPo).

The FES has way few moving parts than a pylon. If it doesn’t work, you just keep flying the same glider. See Dave’s talk on motor-gliders for a good overview of all that can go wrong with pylons http://www.nadler.com/papers/2018_So...pdated_2 .pdf.

Mana,

I would never think about a FES for flying in Fayence.
I you want to escape the "cuvette", just take a higher tow. With a FES, you will eat up all capacity with nothing left for a retrieve (think about needing to motor over the Col d'Etache...).
Internal combustion engines nowadays all rely on the Solo 2350 engine, which is remarably reliable, and with 15 liters of fuel, you will have way more capacity to climb than a FES.

I don't think that a FES is a good choice for the Alpine terrain.

Bert
Ventus cM "TW"

Le mardi 15 septembre 2020 Ã* 12:20:34 UTC+2, Mana a écritÂ*:
On Tuesday, September 15, 2020 at 11:45:05 AM UTC+2, Dave Walsh wrote:
A real problem is putting the word "KISS" and "FES" is the same
sentence or indeed "KISS" and "electric propulsion".
There is nothing simple about electric motors powered by LiPo batteries..
The technology of the motor is very mature and much simpler than of a jet or a combustion engine, which has a direct impact on maintenance needs and on reliability. I agree that the batteries do add cost, complexity and fire hazard (until we find a better technology than LiPo).

The FES has way few moving parts than a pylon. If it doesn’t work, you just keep flying the same glider. See Dave’s talk on motor-gliders for a good overview of all that can go wrong with pylons http://www.nadler.com/papers/2018_So...pdated_2 .pdf.

As always, there is no absolute solution.
For a couple of flight missions, FES is unbeatable.
Depending on the pilot and how he want to fly you have a wide range of offers on the market.
Not only in propulsion systems but also in glider performances.

On Monday, September 14, 2020 at 9:32:04 PM UTC-4, kinsell wrote:
From the mini-Lak brochure on lak.it:
"The FES propulsion system has no known reports of in-flight failures,
allowing you to stay confident in areas of no-lift."

That's just Nonsense. I know of an instance where the controller failed while
FES was under power and the engine quit. I hardly hear about all problems,
surely there have been others...

On Tuesday, September 15, 2020 at 6:20:34 AM UTC-4, Mana wrote:
The technology of the motor is very mature and much simpler than of
a jet or a combustion engine, which has a direct impact on maintenance
needs and on reliability.

But you're asking the wrong question. Whilst the TECHNOLOGY is mature,
the SPECIFIC UNITS we are using in gliders are engineered and built by small
firms in tiny quantities, and not subjected to the kind of testing
and reliability validation we take for granted in our cars, appliances, etc.

On Tuesday, 15 September 2020 at 10:45:05 UTC+1, Dave Walsh wrote:
A real problem is putting the word "KISS" and "FES" is the same
sentence or indeed "KISS" and "electric propulsion".
There is nothing simple about electric motors powered by LiPo batteries.

The discussion seems fairly simple on here - some people know what they are talking about, some are pontificating or speculating, some have actually flown one and read the manual

On Tuesday, September 15, 2020 at 6:20:34 AM UTC-4, Mana wrote:
See Dave’s talk on motor-gliders for a good overview of all that
can go wrong with pylons
http://www.nadler.com/papers/2018_So...pdated_2 .pdf.

I'm flattered but perhaps more relevant is the OSTIV talk I did in February:
https://www.youtube.com/watch?v=mOKpyXtO-3k

On Tuesday, September 15, 2020 at 4:00:32 AM UTC-4, Matthew Scutter wrote:
How does a jet help?

Obviously, a jet makes you look much cooler when you land out.

On Tuesday, September 15, 2020 at 5:45:05 AM UTC-4, Dave Walsh wrote:
A real problem is putting the word "KISS" and "FES" is the same
sentence or indeed "KISS" and "electric propulsion".
There is nothing simple about electric motors powered by LiPo batteries.

I couldn't disagree more. Electric motors are amazingly simple and reliable, and LiPo batteries-- in general-- are extremely safe. The issue arises when you start pushing the technology to its maturity limits. At the power/weight/energy limits we want for the gliders we start making compromises which push into research territory. However, that is a far cry from assuming there is anything complex about the system. We just don't know how to use industrial-grade COTS parts to make the glider's system as light as we desire, so we wind up having to have some bespoke parts. The bespoke parts aren't as well tested because the fleet is small, and this is where problems creep in.

The motors themselves have 0 problems and a 20-30kW motor is tiny in the scheme of industrial COTS motors.