Hello everyone, I’m new – and this thread made me join this forum
It’s Reiner Stemme’s new design – or rather, the old one, basically the next generation of the venerable S10. Main differences are a 20m wingspan with a similar 50:1 glide ratio, a new propulsion system and a fuselage made of prepreg cfrp. It also features a BRS parachute, which increases the WAF tremendously by the way.
For now there are two options, a pure battery powered version, the 20.e with a ~15kWh Battery Pack. That is basically a self launch glider which can get, if not back, at least somewhere comfortabe instead of doing an outlanding.
The one that interests me is the 20.ex which features a 10kWh Battery and a range extender consisting of a Geiger A 1-37 rotary engine and an Emrax 208 used as a generator. All that powers Emrax 228 in the nose.
The range extender will use about 11l/h Super 95ROZ (+1/200th of two stroke oil) @100kts IAS. They’re advertising 16l/h to err on the side of caution.
There is enough weight margin to carry two people, luggage and enough fuel for a long distance flight – and to me, the best thing is, it’s a full fledged high performance glider at the same time.
There are some caveats, such as that you can’t start the rotary engine on the ground as it needs enough airflow for cooling or that you can’t fly faster even if you’re willing to burn some more gas, because the rotary engine is generating power at an optimal setting and that’s it – so if you need to expedite your approach, that extra power must come from the battery. But these aren’t showstoppers.
To me, it all looks too perfect – I’m still wondering what I am missing. Any opinions?
This sounds like really obvious marketing.
Yes, I can see that it may sound like marketing. I usually pride myself in being level headed and objective, and I sound like a fanboy.
But I’m just standing in the queue and I wonder if that was the right decision. Delivery is expected in summer 2023.
As to me – I’m just a glider pilot and I’m somehow wrong in this forum, as you do mainly talk about long range travels – but since that is what I aspire to do and since I cross read all your travel reports for months now, I thought I’ll join here. Especially as the conduct here is a lot more mature than some of the other forums, especially the german language ones.
It doesn’t sound like marketing to me. Lots of information. That Geiger rotary engine for instance. I didn’t know it existed.
That’s ok, Inkognito. Please just understand that we have had loads of companies doing advertising, and the usual clue is a first post which is a straight advert, together with no other participation in other topics – because they don’t want to put in even the absolute minimum effort. Those traders who have put in a bit of effort to contribute to EuroGA have got a lot of business out of it.
I am seriously only a customer. I have some more knowledge than is published, because I asked a lot of questions. They weren’t quite prepared to put all the answers into the contract, though and there are also many things which aren’t final yet. But since there is an opt out after flying with the prototype, I felt safe enough signing it, because untill then almost all of the variables should be finalized.
@Inkognito posts moved to a dedicated thread in this aircraft.
Not sure about the name. May not sell well in Spain. El Fin is “the end” in Spanish 
I always liked the Stemme approach of having a glider that can also behave like a SEP. But its complexity makes it expensive and also ground handling is certainly a challenge at smaller (non glider) airfields. The S12 has the wingspan of an ATR42! While not much can be done about the wingspan, evolving the design into a hybrid or pure electric totally makes sense because it replaces the long drive shaft by a number of cables. But then the range extender probably should be used as such, otherwise a traditional powerplant should give a better fuel consumption.
Clipperstorch wrote:
But then the range extender probably should be used as such, otherwise a traditional powerplant should give a better fuel consumption.
I don’t think so – this is a replacement for the rotax engine and you are meant to travel with it, it’s not just a way to limp back to your home airfield. All that complexity also added serious inefficiency – you need only about 13,3kW at the prop to keep a 850kg plane with a sink of 1,6m/s flying level. (Ok, probably untrue, the flaps to cool and aspirate the engine also add drag, but you get the gist)
Yes, I’m also scared of using normal GA airfields, but there is no helping it. The elfin has only 20m wingspan by the way. As far as I know it’s still under discussion if they will offer longer outer wings or not, but frankly, I’m undecided if I want that. Reducing the wingspan increases the roll rate tremendously and the S10, while not glacial, isn’t really fast, so I probably stick with the 20m.
