Bernard,
Precisely.
As for the rest, the choice isn't between the FES
and a petrol engine motor. It is between the FES
and the GP Gliders system or one like it. FES
like operational simplicity and no performance penalty.
For FES you need to cut off the nose, mount the
engine, cut a hole in the turtle deck area, mount
the 31 Kg of batteries on some reinforced area to take the loads.
For the GP system cut a hole for the engine/prop
assembly (could be in a bathtub like assembly)
and mount the batteries in the wings or maybe
behind the pilot under the wing and above/alongside the wheel box.
If the wing root rib of the glider is designed to
allow access to the volume in front of the spar,
putting the batteries there is likely viable and
better structurally. If better battery tech comes
along the only thing you need worry about is form
factor and you might need a new battery charger.
I doubt you'll be faced with much improvement in
electric motors and control electronics, nor in
propellers. The motors are already 95% or so efficient.
The real problem with keeping motor gliders going
is certification. There aren't many gliders
anyway and adding a certification process that
costs a lot of money and an unknown amount of
time (which is also money) means developing and
marketing a substitute system to support older
motorgliders and selling a few a year as the
older systems gradually die, isn't generally a
viable business model although Walter Binder is
doing this for the Nimbus 3DM etc to substitute a
Solo engine for the original rotax. In Walter's
case he already makes the power package which is certified.
Treating gliders like certified aircraft which
may be used to carry paying passengers always was
a silly idea. No problem with the documents like
CS22, CAR3, FAR 23 etc. Gives you something to
aim for in the structural design but you should
be able to build and test and then sell as long
as you advertise the test results.
I am always amused at the ability of the soaring
movement to glom onto bad ideas.
The history of total energy is another one.
First there was the old Irving TE probe. The
venturi with the penny washer. This was around 1952. Worked great.
Then in the late 1950's someone decided that the
drag of the thing was too high (a small fraction
of one % of total drag on the gliders of the day
with the cruise speeds of the day) and the same
effect could be achieved by the diaphragm
compensator which worked from pitot and static.
Sort of. At one altitude (it used IAS to
compensate kinetic energy which is in TAS). So
for the next ten years ago the literature of the
1960s is filled with "how to make your TE system
work" articles along with "I didn't win/break a
record etc because my TE system never worked properly".
Finally around 1969-1970 Dr Althaus went back to
the venturi type probe by essentially removing
the penny washer. This made the thing more
sensitive to yaw and pitch but TE started working
again and it was regarded as an acceptable
compromise between drag and TE performance.
Mike
At 08:04 AM 9/22/2016, you wrote:
Hi Mike
Please allow me to add to your concluding sentence.
While in Germany I spoke to an employee of a
manufacturer who offers FES variants of his gliders.
He said that customers complain about decals and
rego letters not sanded absolutely flash but
seriously considering an FES drive unit. Then he
shook his head, turned around and walked away.
How any performance chasing glider pilot can
willingly accept a turbulent airflow over the entire
length of the fuselage will ever remain a
mystery to me. Obviously some buyers are convinced by
such comments as "the performance degradation is not noticeableâ.
It can be a truely strange world sometimes!
Kind regards to all
Bernard
On 22 Sep 2016, at 6:44 AM, Mike Borgelt
<<mailto:[email protected]>[email protected]>
wrote:
I guess you missed the bit below the video "
Prototypeneinbau  die Rumpfspalten verschwinden in der Serie natürlich"
Means "single prototype, the gaps will
naturally disappear in series production."
Google translate would have told you that too
but you have to know you need to use it, I guess.
In any case on the contracting part of the
fuselage like that the flow is turbulent and
the boundary layer is fairly thick.
The boundary layer is defined as the distance
from the surface where the flow attains 99% of
the free stream velocity. The velocity profile
isn't linear but about 40% of the thickness
from the surface the flow will be at around
2/3rds the free stream velocity n turbulent flow.
A reference I found said the boundary layer
grows about 16mm per meter from the leading
edge assuming all turbulent flow so aft of
around half way along the canopy the flow is
turbulent and a couple of meters aft of that
will be about 32 mm thick. Any small
discontinuities there are buried deep in the
boundary layer and don't see anything like free
stream velocity. Drag depends on velocity squared so very little drag.
Now the FES is on the nose and there might be a
little laminar flow on the spinner in front of
the prop so the boundary layer is very thin
there when it encounters the folded prop which
will cause it to turbulate and the folded prop
will see most of the free stream velocity.
FES will certainly cause loss of significant
amounts of the laminar flow that is otherwise
present on the front of the fuselage.
Mike
At 10:53 PM 9/21/2016, you wrote:
Content-Type: multipart/alternative;
boundary="----=_NextPart_000_011B_01D2145A.FCB61810"
Content-Language: en-au
YouÂre worried about the increased drag from a FES?
Looking at that video, IÂd be more concerned
about the increased drag from that appalling
panel fit, never mind the huge gaps and the
numerous screw heads. Look at the rear, where
the pylon extends: that panel is sticking about 5mm above the fuse.
It looks like a dodgy home-built botch job.
Btw why not make the thing extend towards the
fuse? I canÂt recall if the motor was too
wide, and life is too short to wait for it to load againÂ
From: Aus-soaring [
mailto:[email protected]] On Behalf Of Mike Borgelt
Sent: Tuesday, 20 September 2016 7:26 PM
To: Discussion of issues relating to Soaring in Australia.
Subject: Re: [Aus-soaring] electric self launch
At 07:04 PM 9/20/2016, you wrote:
Any à good links?
I found a schematic diagram which indicates
that the motor has a pusher folding
prop.Ã Not sure how it retracts and fits in
the fuselage with the blades sticking up?
Here you go:
<http://www.gpgliders.info/technik/>http://www.gpgliders.info/technik/
Scroll down to the videos. They took quite a
while to load here. The link seems slow.
Sheer bloody genius I think.
Mike
Borgelt Instruments - design & manufacture of
quality soaring instrumentation since 1978
<http://www.borgeltinstruments.com/>www.borgeltinstruments.com
tel: 07 4635 5784 overseas: int+61-7-4635 5784
mob: 042835 5784 : int+61-42835 5784
P O Box 4607, Toowoomba East, QLD 4350, Australia
_______________________________________________
Aus-soaring mailing list
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Borgelt Instruments - design & manufacture of
quality soaring instrumentation since 1978
www.borgeltinstruments.com
tel: 07 4635 5784 overseas: int+61-7-4635 5784
mob: 042835 5784 : int+61-42835 5784
P O Box 4607, Toowoomba East, QLD 4350, Australia
_______________________________________________
Aus-soaring mailing list
<mailto:[email protected]>[email protected]
http://lists.base64.com.au/listinfo/aus-soaring
_______________________________________________
Aus-soaring mailing list
[email protected]
http://lists.base64.com.au/listinfo/aus-soaring
Borgelt Instruments - design & manufacture of
quality soaring instrumentation since 1978
www.borgeltinstruments.com
tel: 07 4635 5784 overseas: int+61-7-4635 5784
mob: 042835 5784 : int+61-42835 5784
P O Box 4607, Toowoomba East, QLD 4350, Australia
_______________________________________________
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