Best option for electric self starting glider

And nobody has mentioned the Diana 3.

Lou

On Thursday, April 9, 2020 at 3:42:55 PM UTC-4, wrote:
On Thursday, April 9, 2020 at 7:04:25 AM UTC-7, wrote:
On Thursday, April 9, 2020 at 2:57:10 AM UTC-4, kinsell wrote:
On 4/9/20 12:05 AM, wrote:

To quote Dave Nadler, "How hard could it be?"

Love the quote. Actually, this would be right up my alley. I've developed a few aircraft from scratch and people pay me a lot of money to modify special mission airplanes. A multi-motor self-launcher would be pretty easy to do as a modification to an existing self-launcher; probably a 3 month project. Perhaps I'll get around to this eventually, but first I have some more pressing items on my wish list!


Wow. The GP folks are about four years late in delivering product and
you can do all this in three months!! Go for it!!!

Actually the Alice electric plane has much of the redundancy that you're
asking for. Three motors with dual inverters on each of them, a highly
segmented battery configuration that can be reconfigured almost
infinitely. At least on paper it has those things, they burned up their
prototype before getting to taxi tests.

Clearly you are a brilliant developer.
I'll describe my experience with this task.
Start with existing self launch sailplane having a fuel to noise converter. ASW-24E
Procure a group of components from existing supplier that was/is being used by a developer of self launch sailplanes. 10 week delivery.
Engineer and implement modifications to incorporate "proven" components.. 10 weeks part time.
Test
Component failure (drive).
Return for warranty repair 4 weeks.
Test
Component failure (drive).
Return for warranty repair 4 weeks.
Test
Component failure (drive).
Return for warranty repair. Manufacturer say they can't repair due to my modifications. There were none. 3 weeks.
Source alternative controller used in another proven glider. 3 weeks.
Integrate, develop control and instrumentation to replace items obsoleted by controller change and get running. 6 weeks.
Test fly. Multiple sessions.
Now flying but more work to do to get full power and functionality.
So far this has taken a bit over 2 years, admittedly not full time.
If there was am identified and proven set of compatible components it might be possible for a very skilled person or group to do fast track. Given that I have seen no such group, I seriously doubt the projection is even close to realistic.
Given time this will be made to work well, but it won't be fast, or cheap.
Been there- Doing that
UH

Great job. I'd be interested to hear which components you ended up using. I've had my eye on some of the Pipistrel stuff, but I haven't had a chance to play with them yet. What kind of performance are you getting out of your ASW-24E conversion?

I actually make a living doing these types of projects FAST. I'm fortunate to live above a 4,000ft^2 workshop with in-house machining, CNC routing, CAD, vacuum forming, welding, autoclave, paint booth etc. I reckon it would take me about 3 months of full time work (Note: I tend to spend at least 80 hours per week on such projects), but I completely understand that 1-3 years is probably more reasonable for a typical homebuilt project.

Contact me privately for more conversation.
UH

but this would be very easy to do with electric.

I love it when armchair aircraft designers tell us something is "very easy."

On Thursday, April 9, 2020 at 4:46:57 PM UTC-7, wrote:
but this would be very easy to do with electric.

I love it when armchair aircraft designers tell us something is "very easy."

"armchair aircraft designers"... lol. I'll have to show you some of my more challenging, and very much finished, aerospace projects someday

I'm currently installing a Rotax on my ship. Electric is interesting, and I can certainly understand why it appeals to many. I personally favor the increased range of gasoline over the cleanliness and convenience of electric. Others will have different preferences. Either option can eliminate tows and retrieves, which is all well and good. However, a motor glider that "will start" can do a lot of things that a motor glider that "will probably start" cannot.

It would be a game changer if I could "safely" fly deep into unlandable terrain, or ridge soar the lip of the grand canyon. I'd love to plan some epic soaring safaris to rugged areas of Alaska, or make first flights in magnificent places. It would also be a whole new ballgame if I could reduce my restart altitude to something like 200ft. That sounds crazy until you figure out that's about 90 seconds at typical sink rates. If it takes only 10 seconds to transition to a powered climb, then 90 seconds provides plenty of margin.

The first electric motor gliders borrowed the retractable mast from their gasoline counterparts. Later, folks figured out that the smaller electric motor could fit in the nose. I think it's only a matter of time before people discover that we can use more than one motor, as is the trend for VTOL. Perhaps I'll get around to this at some point but I currently have a couple of more pressing crazy projects on my plate.

No disrespect intended, but RAS seems to have a large number of unicorn herders who are somewhat unclear on the laws of physics and engineering.

On Thursday, April 9, 2020 at 10:32:35 PM UTC-4, wrote:
The first electric motor gliders borrowed the retractable mast
from their gasoline counterparts.

No, real-world designers understood that a pylon system:
- makes possible much larger hence more efficient prop,
and efficiency is critical given battery low energy
- avoids prop strikes
- doesn't reduce performance
- makes cooling easier
Real-world examples include:
- original electric Silent circa 1997
- Antares (2m prop)
- AS-34 (and AS-32E sustainer)
- GP series (Real Soon Now)
- Hank's ASW-24E ;-)
etc.

On Thursday, April 9, 2020 at 8:21:00 PM UTC+2, Eric Greenwell wrote:
Magnus wrote on 4/8/2020 7:11 AM:
Hi experienced glider pilots,

I am a newly retired ex glider pilot that is updating my license and want to do some serious soaring and distance flights in Europe now that I have plenty of time. I live in Lausanne (member of Montricher gliding club) and as well member in Landskrona gliding club in Sweden as well where I spend most of my summers.
I have come down to the following alternatives for a private purchase:

- LAK 17C Front Electric Self starter, 18m, 22kW, 10.32 m2 wing surface, MTOW 600kg and CS-22 certification

- GP-15 Jetta, retractable motor, 15m, 25kW, 7.78 m2 wing surface, MTOW 470kg, UL/EcoLight certification

Both ships are flapped, take water ballast, Vne= 275km/h, wing loading between 37 - 57kg/m2, L/D around 50 and has a base price of apps. 100kEuro

GP15 seems to be a more modern glider with safety cockpit, ballistic rescue system and steerable tail wheel but LAK seems to be a more stable company with longer experience.

This is a nice problem to have but I would very much like your input as I have a one time opportunity to get my dream machine and I want to get it right.

Where do you find the information about the LAK 17C? I can not find any, not even
on the LAK site.

My dream is for a smaller, lighter, simpler self-launcher, but with the same
performance as my ASH26E. I considered the miniLak, AS34, and the GP15. The
miniLak did not have enough wing loading, L/D, and powered range for the
Nevada/Utah area I often fly in, and the AS34 was just as big and heavy as the
ASH26E. So, I have ordered a GP15 for delivery next year, as it promises the best
compromise. It will be a few months, maybe longer, before we know if it begins to
fulfill it's promise.

--
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

Hi Eric,
Thanks very much for your Guide to Self-Launching...
Your dream is the same as mine and I am curious how you came to the decision with all your experience behind you. Have you tested it? GP15 looks really good on paper but is unproven so far. I also met Sebastian Kawa last year after his almost crash landing with his GP14 when the electrical motor did not start. He has written an article about it in Soaring International December issue. I would really need some pilot feedback from testing it before I would dare to order one.
The LAK17FES was first officially shown at the Aero Show last year but the information is limited as LAK is waiting for the CS-22 certification. I will send you a data sheet separately by mail. It is heavier (but also 18m) and the motor is not as strong as for GP15 so it needs 350m on asphalt and 400-500m on grass to get airborne (without water ballast), which is a handicap. he battery is also smaller compared to GP15 if you choose the Jettas 8.1 kW alternative. The front vs the pylon mounted propeller can be discussed but the front mounted seems simpler with less risk for failure (less moving parts).
I really wish you all the best with the GP15 choice and look forward to your experiences.

On Wednesday, April 8, 2020 at 5:14:54 PM UTC+2, wrote:
Hello Magnus,

I can't respond to flight characteristics of the two self-launchers you mentioned (LAK-17C and GP-Gliders JETA). But, I can say that I sat in a JETA and also have JETA serial number 5 on order.

The JETA MTOG, per the provisional flight manual, is 525KG (1157 lbs). Below are the advertised self-launch numbers with the larger battery:

a) 5 x takeoff and climb to 800 m (2,600 feet) altitude, or
b) 1 x takeoff and climb to 800 m altitude + 150 km (80 nm) autonomy, or
c) 1 x takeoff and total climb to 4 500 m (14,700 feet)
d) my number: aero tow and 185 km (100nm) autonomy based on 20 nm/launch.

Climb rate: 3,7 m/s (728 fpm or 7.2 knots)

takeoff distance: 180 m (590 feet)

I visited the GP-Glider factory near Krosno, Poland (jokingly to make sure that they weren't operating out of a tent). I was happy that they were doing things correctly. A visit to the LAK factory would have given me a balanced experience, but I was not able to do that.

Raul Boerner
LS-6BWL

Hi Raul,
When is your delivery of the Jeta? I am really interested in your experiences. Where are you flying?
According to the max wing loading of 60/37 kg/m2 the MTOM is below 475/285kg UL with a wing area of 7.77m2 - this also is indicated on the website. I suppose the take-off distance is without ballast but it is still good. How/where do you register it as UL?

On Thursday, April 9, 2020 at 1:41:58 AM UTC+2, wrote:
I'm hoping that someone creates an electric self-launch glider with complete propulsion redundancy: two 20kW motors, two propellors, two batterey packs, two speed controls. Any single failure would leave you with at least sustainer performance.

A traditional motorglider must be flown like an unpowered sailplane; you must keep safe landing options within glide. With sufficient redundancy, it would not be unreasonable to enjoy soaring in some entirely new and inhospitable places.


There is a the Euroglider under design and testing in France with 2 electric motors with folding propellers on the wings - see Soaring International February 2020 issue.

On Friday, April 10, 2020 at 4:46:52 PM UTC+1, Magnus wrote:
On Wednesday, April 8, 2020 at 5:14:54 PM UTC+2, wrote:
Hello Magnus,

I can't respond to flight characteristics of the two self-launchers you mentioned (LAK-17C and GP-Gliders JETA). But, I can say that I sat in a JETA and also have JETA serial number 5 on order.

The JETA MTOG, per the provisional flight manual, is 525KG (1157 lbs). Below are the advertised self-launch numbers with the larger battery:

a) 5 x takeoff and climb to 800 m (2,600 feet) altitude, or
b) 1 x takeoff and climb to 800 m altitude + 150 km (80 nm) autonomy, or
c) 1 x takeoff and total climb to 4 500 m (14,700 feet)
d) my number: aero tow and 185 km (100nm) autonomy based on 20 nm/launch.

Climb rate: 3,7 m/s (728 fpm or 7.2 knots)

takeoff distance: 180 m (590 feet)

I visited the GP-Glider factory near Krosno, Poland (jokingly to make sure that they weren't operating out of a tent). I was happy that they were doing things correctly. A visit to the LAK factory would have given me a balanced experience, but I was not able to do that.

Raul Boerner
LS-6BWL

Hi Raul,
When is your delivery of the Jeta? I am really interested in your experiences. Where are you flying?
According to the max wing loading of 60/37 kg/m2 the MTOM is below 475/285kg UL with a wing area of 7.77m2 - this also is indicated on the website. I suppose the take-off distance is without ballast but it is still good. How/where do you register it as UL?

Absent from those endurance/climb figures is the weight at which these are achieved, which is going to have a huge impact on the figures. Does anyone know the weight?
And are they are calculated or experimentally tested?