Best option for electric self starting glider

On Thursday, April 9, 2020 at 9:00:24 AM UTC-8, Soartech wrote:
On Thursday, April 9, 2020 at 2:12:46 AM UTC-4, wrote:
Out of curiousity, does anyone know how electric motorgliders handle prop strikes? I know that it can be very expensive to rebuild a conventional aircraft engine after a prop strike, but what are electric manufacturers recommending?

I am buying the Jeta because I have seen a Silent Electro prop strike on a grass field. The prop is just too close to the ground for reliable self-launching in an FES (my opinion). In the situation I saw the prop exploded but running the motor afterward showed no evidence of a bent shaft or other damage to the system. However they still recommend you send it back to the factory for inspection!

I have lifted the tail of a Silent 2 Electro three feet before the prop contacts a level surface. It has flaps and does a nice two point lift off. I think a mini Lax might be similar. The prop strike might of been to much foward stick.

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

On 4/9/20 12:20 PM, 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.


Typing "lak 17c" into Google brings up multiple results, including an
Oct 2018 test flight in FB. Also been discussed on R.A.S.

kinsell wrote on 4/9/2020 1:38 PM:
On 4/9/20 12:20 PM, Eric Greenwell wrote:
Magnus wrote on 4/8/2020 7:11 AM:

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.


Typing "lak 17c" into Google brings up multiple results, including an Oct 2018
test flight in FB.* Also been discussed on R.A.S.

I did that, and didn't find very much information. If it's not on the factory
site, it does not seem like a good choice to consider by a pilot that wants a
glider for next year's season. But, given it's an 18 m glider, it is unlikely to
meet my "smaller, lighter, easier) criteria.
--
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

On 4/10/20 11:55 AM, Eric Greenwell wrote:
kinsell wrote on 4/9/2020 1:38 PM:
On 4/9/20 12:20 PM, Eric Greenwell wrote:
Magnus wrote on 4/8/2020 7:11 AM:

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.


Typing "lak 17c" into Google brings up multiple results, including an
Oct 2018 test flight in FB.Â* Also been discussed on R.A.S.

I did that, and didn't find very much information. If it's not on the
factory site, it does not seem like a good choice to consider by a pilot
that wants a glider for next year's season. But, given it's an 18 m
glider, it is unlikely to meet my "smaller, lighter, easier) criteria.


It's on the Blanik America website with base price of 99.500 euros.
Nice list of accessories. I saw a claim it was just a 17B-FES with a
new wing profile, if that's true then you would have the weight info.

http://home.nwi.net/~blanikam/ba/lak_prices.htm

Given GP's record in delivering gliders, I would take their promised
delivery dates with a huge grain of salt.

-Dave

GP are getting their act together and increasing their manufacturing footprint.
We should finally see GP's coming out of the factory door.

Even if there is a little bit more complexity with a pylon mounted motor, there are clear advantages over the FES solution.
- more powerful motor
- better cooling
- better prop efficiency
- no prop strike risk
Another advantage of GP with large batteries is that, beside the larger energy capacity, the cells are discharged at lower amps rating and therefore run cooler.

The climb performance seems to be in line with flight test results.
As discussed before the published climb perf are without WB. Therefore TOM 320-330 kg. Even when flying empty, the typical WL will be ~42 kg/m2 which is already nice.
GP has made some good choices:
- light weight to allow very good electric climb performance (climb rate and altitude gain)
- high aspect ratio/low wing surface to achieve high L/D and higher WL. Maybe Max L/D will be a little bit less than 18m like ASH26 or DG800, but the L/D above 150 km/h should be better.

BTW, you need to add fixed ballast to get to 525 kg MTOM.

Regards,
JL

kinsell wrote on 4/10/2020 1:18 PM:
On 4/10/20 11:55 AM, Eric Greenwell wrote:
kinsell wrote on 4/9/2020 1:38 PM:
On 4/9/20 12:20 PM, Eric Greenwell wrote:
Magnus wrote on 4/8/2020 7:11 AM:

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.


Typing "lak 17c" into Google brings up multiple results, including an Oct 2018
test flight in FB.* Also been discussed on R.A.S.

I did that, and didn't find very much information. If it's not on the factory
site, it does not seem like a good choice to consider by a pilot that wants a
glider for next year's season. But, given it's an 18 m glider, it is unlikely to
meet my "smaller, lighter, easier) criteria.


It's on the Blanik America website with base price of 99.500 euros. Nice list of
accessories.* I saw a claim it was just a 17B-FES with a new wing profile, if
that's true then you would have the weight info.

http://home.nwi.net/~blanikam/ba/lak_prices.htm

Given GP's record in delivering gliders, I would take their promised delivery
dates with a huge grain of salt.

It would take major changes beyond a new wing profile to transform the 17B FES
into a self-launcher; regardless, I contacted the dealer in Nov 2019 about
electric self-launchers. He offered only the miniLAK (it ended up being my second
choice, after the GP15), and did not mention the 17C. It is odd that the dealer
lists the prices for the 17C, but no technical information.

--
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

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.

Note that at LAK17C max power is 30kW. With such power climb performance are very good as there is no pylon drag.

The propulsion efficiency has much more direct effect than pylon drag.
In fact, for Takeoff and climb performance, the overall glider drag has secondary effect compared to aircraft weight and available thrust.
Without fuselage interference and opportunities for larger props, the pylon mounted motor provides a significant efficiency advantage. This has a direct effect on climb performance in terms of climb rate and altitude gain.
Running large battery packs, beside running cooler, also provides better energy efficiency and installing large batteries in the wing reduces overall structure weight and provides better flying handling characteristics due to CG.

FES is a nice solution, especially for retrofit of existing gliders.
For a brand new design, there are opportunities for better optimizations.
Is GP at the optimum, probably not (yet:-), but they have certainly made good design decisions for both teh glider and the propulsion.