Oops, should have read the entire thread before posting. JJ answered my
question perfectly.

Kenn's post was extremely informative.

Dan
5J

On 2/8/21 6:36 AM, Dan Marotta wrote:
Can the glider chosen for this modification support an extra 100 lb in
the fuselage?Â* If the batteries are carried in the wings, what's the
remaining weight of the non-lifting parts?Â* Can the wings sustain the
extra bending load?

Dan
5J

On 2/7/21 1:30 PM, Hank Nixon wrote:
On Sunday, February 7, 2021 at 2:46:31 PM UTC-5, David Scott wrote:
On Friday, February 5, 2021 at 9:52:57 AM UTC-8, kinsell wrote:
On 2/2/21 6:09 PM, 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.

Thank you for your responses. To be clear I don't have a sailplane
but would like to get into the sport and the answers to this
question would possibly affect what glider I would get. I am smart
enough to get all my ducks in a row before doing anything, and this
is the first I have talked about it. From an engineering
standpoint, it doesn't look too difficult, navigating the
regulations is where I expect the most trouble.


Putting together a motorglider is a strange path towards getting
involved with the sport. Might be better to take lessons, get the
rating, and have some time under your belt before taking on a project
like this.

In my local club, I see people going solo and maybe getting their
rating, and immediately thinking about buying a glider. This is with a
reasonable selection of under utilized club ships sitting around. I
encourage them to wait a couple years first.

If you're all set on owning an electric motorglider, there's a
reasonable selection of Silent 2 Electro's on W&W. Do yourself and the
owners a big favor and pick up one of those.

-Dave
In response to the first paragraph, I am more curious as to what my
options would be IF my local club dissolves and tows are no longer
available. I absolutely will get flying before doing anything else!
The single place club gliders are 2 1-26s and a LET L-33, @$40hr. It
sounds like none let you reach much of the areas soaring because of
their low performance from club YouTube videos. Since my whole
interest would be cross country, or the wave window south of Mt Hood,
I will need to get access to a better glider than the club offers.

The Grasshopper has some very interesting aspects. It is the first
articulated pylon I have seen, a design I have thought about quite a
lot to get it tucked into the fuselage with the smallest opening
possible. Designing it to be as compact as possible to fit as many
gliders would be an obvious design criteria.

I do not want to reinvent the wheel, just make as few modifications
as necessary for a different application. With this in mind electric
paramotors are quite interesting. 110-120 lbs of thrust with 4ah
batteries would be a good starting point, perhaps. I am not saying
the cheapest versions are acceptable but the higher volume will bring
the prices down. It looks like $5-$6k would buy the parts needed for
a glider, plus the pylon assembly. A complete paramotor weighs around
65lbs so I figure this is close to what it would add to a glider, if
done right. The biggest problem to an electric propulsion system is
the batteries, and those are going to get vast improvements in the
near future.


This is all just food for thought. To add more food I have a few
questions. Let us use a 500lb 15 meter glider as the reference.

Any idea on how much thrust is need to sustain altitude?
How much thrust is needed to climb at 200 fpm? 300 fpm?

Some data from first hand experience:
ASW-24E converted to electric from 2 cycle Rotax gas.
Power system including all items is right at 100 lb added to pure
sailplane airframe weight.
This is a pylon mounted retractable system.
Battery is 120 volt,4.9 kwh lithium ion weighing 60 lb.
Climb rate at 160 amps is 300 ft/minute. Actual power delivered is
about 16kw.
Climb rate at 230 ampsÂ* is 500 ft/minute. Actual power delivered is
about 23kw at this time
Your cost estimate is a bit less than1/2 what it would require for
parts, not including items required to do the airframe conversion and
assuming the person doing this can fabricate required items, engineer
and wire theÂ* system, design and construct the prop, etc.
This assumes perfect efficiency and nothing destroyed or scrapped
going through the learning process. Of those I am aware of that have
done ,or are doing this, nobody has had that good fortune.
FWIW
UH