What is involved regulation wise adding an electric motor to a glider?

On Tuesday, February 2, 2021 at 1:26:10 PM UTC-8, David Scott wrote:
I DON'T mean to stir up trouble on this forum with this question, especially being new, but have been wondering about this for some time. I am wondering how feasible it would be to do this with either a homebuilt or experimental glider here in the US?

I figure this has been asked but didn't find any threads on it.

Thanks to all for your responses. What I am hearing certainly doesn't scare me away from the idea, which is all it is at the moment but I have been "thinking" about this and possible solutions for years. My biggest take is to talk to those who would be signing it off to find out what they think of it.

On Wednesday, February 3, 2021 at 2:24:37 PM UTC-8, David Scott wrote:
On Tuesday, February 2, 2021 at 1:26:10 PM UTC-8, David Scott wrote:
I DON'T mean to stir up trouble on this forum with this question, especially being new, but have been wondering about this for some time. I am wondering how feasible it would be to do this with either a homebuilt or experimental glider here in the US?

I figure this has been asked but didn't find any threads on it.
Thanks to all for your responses. What I am hearing certainly doesn't scare me away from the idea, which is all it is at the moment but I have been "thinking" about this and possible solutions for years. My biggest take is to talk to those who would be signing it off to find out what they think of it.

I have been very involved in high-performance composites for many years, have been machining for 33 years now, and doing product development longer. I have my own CNC machine shop where I mostly make my own products so I am well equipped to do the design and manufacturing. I have done enough projects that took over 2000 hours to get into production that I do understand there is always way more work than expected, but this really isn't that big of a job, comparatively.

I really like the FES idea for modifying a stock glider for its simplicity. The only structural change to the glider would be to cut off the nose but the firewall would certainly reinforce it, depending on how the batteries are stored. The biggest downside is that the propeller has to be too small for efficiency.

You would also have to cut an access port in the fuselage to install & remove the batteries. This will substantially weaken the fuselage, so it will have to be reinforced in an engineered manner.

Tom

On Wednesday, February 3, 2021 at 3:54:59 PM UTC-8, 2G wrote:
On Wednesday, February 3, 2021 at 2:24:37 PM UTC-8, David Scott wrote:
On Tuesday, February 2, 2021 at 1:26:10 PM UTC-8, David Scott wrote:
I DON'T mean to stir up trouble on this forum with this question, especially being new, but have been wondering about this for some time. I am wondering how feasible it would be to do this with either a homebuilt or experimental glider here in the US?

I figure this has been asked but didn't find any threads on it.
Thanks to all for your responses. What I am hearing certainly doesn't scare me away from the idea, which is all it is at the moment but I have been "thinking" about this and possible solutions for years. My biggest take is to talk to those who would be signing it off to find out what they think of it.

I have been very involved in high-performance composites for many years, have been machining for 33 years now, and doing product development longer. I have my own CNC machine shop where I mostly make my own products so I am well equipped to do the design and manufacturing. I have done enough projects that took over 2000 hours to get into production that I do understand there is always way more work than expected, but this really isn't that big of a job, comparatively.

I really like the FES idea for modifying a stock glider for its simplicity. The only structural change to the glider would be to cut off the nose but the firewall would certainly reinforce it, depending on how the batteries are stored. The biggest downside is that the propeller has to be too small for efficiency.

You would also have to cut an access port in the fuselage to install & remove the batteries. This will substantially weaken the fuselage, so it will have to be reinforced in an engineered manner.

Tom

That is something I would avoid doing if at all possible. But I do understand that is where the batteries would have to be to maintain CG. If there is no way around it then a pylon mounted motor begins to look much, much better. The fun of design, there is no perfect answer, just the best set of compromises.

David Scott wrote on 2/3/2021 2:24 PM:
On Tuesday, February 2, 2021 at 1:26:10 PM UTC-8, David Scott wrote:
I DON'T mean to stir up trouble on this forum with this question, especially being new, but have been wondering about this for some time. I am wondering how feasible it would be to do this with either a homebuilt or experimental glider here in the US?

I figure this has been asked but didn't find any threads on it.

Thanks to all for your responses. What I am hearing certainly doesn't scare me away from the idea, which is all it is at the moment but I have been "thinking" about this and possible solutions for years. My biggest take is to talk to those who would be signing it off to find out what they think of it.

I have been very involved in high-performance composites for many years, have been machining for 33 years now, and doing product development longer. I have my own CNC machine shop where I mostly make my own products so I am well equipped to do the design and manufacturing. I have done enough projects that took over 2000 hours to get into production that I do understand there is always way more work than expected, but this really isn't that big of a job, comparatively.

I really like the FES idea for modifying a stock glider for its simplicity. The only structural change to the glider would be to cut off the nose but the firewall would certainly reinforce it, depending on how the batteries are stored. The biggest downside is that the propeller has to be too small for efficiency.

Are you familiar with 4 kwh lithium battery packs and BMS units? How about 20-25 kw DC motors
and the electronic controllers for them? The mechanical part of an electric propulsion system
might be harder (perhaps much harder) than the electrical part.

I think you can buy a complete FES system (includes drawings for the installation) for many of
the popular gliders. That would save you an immense mount of design and testing time. Visit the
FES developer's site at

http://www.front-electric-sustainer.com/index.php

--
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 Wednesday, February 3, 2021 at 4:02:37 PM UTC-8, Eric Greenwell wrote:
David Scott wrote on 2/3/2021 2:24 PM:
On Tuesday, February 2, 2021 at 1:26:10 PM UTC-8, David Scott wrote:
I DON'T mean to stir up trouble on this forum with this question, especially being new, but have been wondering about this for some time. I am wondering how feasible it would be to do this with either a homebuilt or experimental glider here in the US?

I figure this has been asked but didn't find any threads on it.

Thanks to all for your responses. What I am hearing certainly doesn't scare me away from the idea, which is all it is at the moment but I have been "thinking" about this and possible solutions for years. My biggest take is to talk to those who would be signing it off to find out what they think of it.

I have been very involved in high-performance composites for many years, have been machining for 33 years now, and doing product development longer. I have my own CNC machine shop where I mostly make my own products so I am well equipped to do the design and manufacturing. I have done enough projects that took over 2000 hours to get into production that I do understand there is always way more work than expected, but this really isn't that big of a job, comparatively.

I really like the FES idea for modifying a stock glider for its simplicity. The only structural change to the glider would be to cut off the nose but the firewall would certainly reinforce it, depending on how the batteries are stored. The biggest downside is that the propeller has to be too small for efficiency.

Are you familiar with 4 kwh lithium battery packs and BMS units? How about 20-25 kw DC motors
and the electronic controllers for them? The mechanical part of an electric propulsion system
might be harder (perhaps much harder) than the electrical part.

I think you can buy a complete FES system (includes drawings for the installation) for many of
the popular gliders. That would save you an immense mount of design and testing time. Visit the
FES developer's site at

http://www.front-electric-sustainer.com/index.php

--
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

When I checked a year-ish ago you had to go through their distributor in the US and they had to install it. I never checked but figured it would be in the $40k neighborhood. At least their distributor is close by here in Washington. I'm just outside of Hood River.

David Scott wrote on 2/3/2021 4:24 PM:
On Wednesday, February 3, 2021 at 4:02:37 PM UTC-8, Eric Greenwell wrote:
David Scott wrote on 2/3/2021 2:24 PM:
On Tuesday, February 2, 2021 at 1:26:10 PM UTC-8, David Scott wrote:
I DON'T mean to stir up trouble on this forum with this question, especially being new, but have been wondering about this for some time. I am wondering how feasible it would be to do this with either a homebuilt or experimental glider here in the US?

I figure this has been asked but didn't find any threads on it.

Thanks to all for your responses. What I am hearing certainly doesn't scare me away from the idea, which is all it is at the moment but I have been "thinking" about this and possible solutions for years. My biggest take is to talk to those who would be signing it off to find out what they think of it.

I have been very involved in high-performance composites for many years, have been machining for 33 years now, and doing product development longer. I have my own CNC machine shop where I mostly make my own products so I am well equipped to do the design and manufacturing. I have done enough projects that took over 2000 hours to get into production that I do understand there is always way more work than expected, but this really isn't that big of a job, comparatively.

I really like the FES idea for modifying a stock glider for its simplicity. The only structural change to the glider would be to cut off the nose but the firewall would certainly reinforce it, depending on how the batteries are stored. The biggest downside is that the propeller has to be too small for efficiency.

Are you familiar with 4 kwh lithium battery packs and BMS units? How about 20-25 kw DC motors
and the electronic controllers for them? The mechanical part of an electric propulsion system
might be harder (perhaps much harder) than the electrical part.

I think you can buy a complete FES system (includes drawings for the installation) for many of
the popular gliders. That would save you an immense mount of design and testing time. Visit the
FES developer's site at

http://www.front-electric-sustainer.com/index.php

--
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

When I checked a year-ish ago you had to go through their distributor in the US and they had to install it. I never checked but figured it would be in the $40k neighborhood. At least their distributor is close by here in Washington. I'm just outside of Hood River.

You can see why some choose to install jet engines: simpler, lighter, more compact (no
propeller), and the fuel is pumped in, avoiding the need for a door in fuselage.

--
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

When I checked a year or so ago you had to go through their distributor in the US and they had to install it. I never checked but figured it would be in the $40k neighborhood. At least their distributor is close by here in Washington. I'm just outside of Hood River.


Who would this distributor be?
When I last communicated with Luka he made it clear that he was not going to be supplying conversion kits but did indicate the cost would be on the order of 30k euros. He has better things to do working with the established factories that have resident expertise and future demand.
UH

On Tuesday, February 2, 2021 at 4:26:10 PM UTC-5, David Scott wrote:
I DON'T mean to stir up trouble on this forum with this question, especially being new, but have been wondering about this for some time. I am wondering how feasible it would be to do this with either a homebuilt or experimental glider here in the US?

I figure this has been asked but didn't find any threads on it.

It's "easy" for a qualified definition of "easy" meaning "straightforward". Several of us are already well down this route, if you're interested reach out to me and I'll send you an invite to our Slack group.

The FAA's regulations are no big deal. Others have pointed out the steps that you have to go through, and Bob Kuykendall pretty much nails it. Don't do bad work, don't do work which will manifestly endanger you or-- worse-- the public, don't just wing it. Aside from that, if the system works and you are happy to be the test pilot, the FAA is more than willing to give you the rope you need to hang yourself with.

Practically, it's not easy to find the right combination of propeller and motor and battery and layout which works. Every glider has its own peculiarities, and those need to be negotiated at some cost of time and money.

I would caution you against considering anything but the lightest of gliders. There's nothing wrong or unsafe about larger self-launching gliders, but when you're pulling this together in your shop it's a world of different if you're working with a 15kW motor, a 3kW-hr battery, and a 1.3m prop vs. a 40kW motor a 6kW-hr pack, and a 2m prop. Good candidates are the AC-5M and the Carbon Dragon. The former because all you have to do is swap out the existing engine, and the latter because it's so very, very light.

Kenn Sebesta wrote on 2/5/2021 7:02 AM:
On Tuesday, February 2, 2021 at 4:26:10 PM UTC-5, David Scott wrote:
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Practically, it's not easy to find the right combination of propeller and motor and battery and layout which works. Every glider has its own peculiarities, and those need to be negotiated at some cost of time and money.

I would caution you against considering anything but the lightest of gliders. There's nothing wrong or unsafe about larger self-launching gliders, but when you're pulling this together in your shop it's a world of different if you're working with a 15kW motor, a 3kW-hr battery, and a 1.3m prop vs. a 40kW motor a 6kW-hr pack, and a 2m prop. Good candidates are the AC-5M and the Carbon Dragon. The former because all you have to do is swap out the existing engine, and the latter because it's so very, very light.

I've been comparing electric self-launching gliders, including the JS3 RES (15M), GP15,
miniLak, and Silent Electro. It became obvious the dramatic difference low weight can make in
powered performance. For example, when both have the "big batteries": the JS3 RES 15M is 250
pounds heavier than the GP15, and for that reason it's max altitude gain is about 9000',
compared to 13,000' for the GP15.

--
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

Pipistrel is working on a hydrogen fuel cell powered aircraft. This might be an interesting idea to consider.
I have heard of another company working on a larger 6 person aircraft that recently took flight.

https://www.compositesworld.com/news...t-takes-flight

Darren