Front Electric Sustainer

[LimaZulu]

First flight of Front Electric Sustainer - FES

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

http://www.youtube.com/watch?v=TNOKq6PKIvM

Regards,

Luka Znidarsic

[Andy[_10_]]

On Nov 1, 1:49*am, LimaZulu > wrote:
> First flight of Front Electric Sustainer - FES
>
> http://www.front-electric-sustainer.com
>
> http://www.youtube.com/watch?v=TNOKq6PKIvM
>
> Regards,
>
> Luka Znidarsic

If I read the specs right you can operate at full power for 14.4
minutes over which time you can climb a bit over 4,300 feet. How's
that compare to other sustainers? This seems simpler than most other
configurations which is nice.

9B

[JJ Sinclair]

I was wondering when someone would use the motor and folding prop used
on the Radian RC sailplane on a full scale ship. Nice, motor weight in
nose is balanced with battery weight aft and only 77 pounds total. I
figure 75 miles at low power or 5700 foot climb at full power. Heat
from running motor could warm your feet on a cold winter day! Any idea
on retrofit price and availability?
JJ

[Darryl Ramm]

On Nov 1, 4:29*am, Andy > wrote:
> On Nov 1, 1:49*am, LimaZulu > wrote:
>
> > First flight of Front Electric Sustainer - FES
>
> >http://www.front-electric-sustainer.com
>
> >http://www.youtube.com/watch?v=TNOKq6PKIvM
>
> > Regards,
>
> > Luka Znidarsic
>
> If I read the specs right you can operate at full power for 14.4
> minutes over which time you can climb a bit over 4,300 feet. *How's
> that compare to other sustainers? *This seems simpler than most other
> configurations which is nice.
>
> 9B

It would be interestingly they claim level flight for 120km which is
greater distance than a 4,300' climb will normally allow you to glide.
Just plucking numbers out of thin air of 50 knots for optimal climb
and cruise speeds (I expect climb would be slower) and an L/D of 50:1.
You would travel 22 km in the climb and glide 65km for a total of
87km. It would require a L/D > 74 to match the straight cruise. The
exact optimal speeds and the profile of the climb as battery power
diminishes likely affects all this.

Looks like nice packaging. I am curious as well what happens to the
forward air cockpit air vent, nose pitot tube, nose tow hook, and
where cooling air for the engine comes from (presumably the nose
hole). At 95% efficiency the 15kW motor will generate 750W.

Darryl

[Uncle Fuzzy]

On Nov 1, 7:07*am, Darryl Ramm > wrote:
> On Nov 1, 4:29*am, Andy > wrote:
>
>
>
>
>
> > On Nov 1, 1:49*am, LimaZulu > wrote:
>
> > > First flight of Front Electric Sustainer - FES
>
> > >http://www.front-electric-sustainer.com
>
> > >http://www.youtube.com/watch?v=TNOKq6PKIvM
>
> > > Regards,
>
> > > Luka Znidarsic
>
> > If I read the specs right you can operate at full power for 14.4
> > minutes over which time you can climb a bit over 4,300 feet. *How's
> > that compare to other sustainers? *This seems simpler than most other
> > configurations which is nice.
>
> > 9B
>
> It would be interestingly they claim level flight for 120km which is
> greater distance than a 4,300' climb will normally allow you to glide.
> Just plucking numbers out of thin air of 50 knots for optimal climb
> and cruise speeds (I expect climb would be slower) and an L/D of 50:1.
> You would travel 22 km in the climb and glide 65km for a total of
> 87km. It would require a L/D > 74 to match the straight cruise. The
> exact optimal speeds and the profile of the climb as battery power
> diminishes likely affects all this.
>
> Looks like nice packaging. I am curious as well what happens to the
> forward air cockpit air vent, nose pitot tube, nose tow hook, and
> where cooling air for the engine comes from (presumably the nose
> hole). At 95% efficiency the 15kW motor will generate 750W.
>
> Darryl- Hide quoted text -
>
> - Show quoted text -
JJ, I've wondered the same thing too. Seems too simple NOT to do.
What I want to know is this: When is China going to start cranking
out cheap brushless motors in the 15 - 50 Kw range (5Kw increments
will do nicely, thank you)? It's inevitable, but I'm impatient. I'd
like my electric motorcycle, 'round town car, and self launcher sooner
rather than later.

[AndersP]

Uncle Fuzzy wrote:
> On Nov 1, 7:07 am, Darryl Ramm > wrote:
>> On Nov 1, 4:29 am, Andy > wrote:

>> It would be interestingly they claim level flight for 120km which is
>> greater distance than a 4,300' climb will normally allow you to glide.
>> Just plucking numbers out of thin air of 50 knots for optimal climb
>> and cruise speeds (I expect climb would be slower) and an L/D of 50:1.
>> You would travel 22 km in the climb and glide 65km for a total of
>> 87km. It would require a L/D > 74 to match the straight cruise. The
>> exact optimal speeds and the profile of the climb as battery power
>> diminishes likely affects all this.

A nice side effect, running on electric power, is that you probably
won't have to use the common "saw tooth" technique that you adopt on
combustion engine SSG:s running full throttle.

An electrical engine with engine control can easily be used to run on
half power, making saw toothing unnecessary. That said, the engine
control system must not have excessive loss running partial throttle.

This used to be a problem in electrical model aircraft control circuits.
With todays speed controls this is usually no longer a problem.

I would like to have the batteries in my wings though. The idea of
having a solid block of metal/lithium/what not behind my back in a crash
is a bit scary. But I guess at these weights its not worse than having
your average Solo behind you.

But if I would wish, that would be my option.

Having flown electric model aircrafts since about 1983-1984, I give a
standing ovation to this and other electrical SSG/SLG solutions coming
out of various manufacturers.

Look at model aircrafts, today most starts to fly with electric power.
Back in 1980'ies others laughed at you, claiming it was never going to
be big. If we look 10-20 years ahead I think no-one will choose a
combustion engine over an electrical in a new glider.

We will now also be able to benefit from all money being plowed down on
battery technology in the car industry.

I have high hopes for the future going electric, it fits so nice with
our beloved sport.

Go-go,
Anders P

[Brad[_2_]]

On Nov 1, 1:49*am, LimaZulu > wrote:
> First flight of Front Electric Sustainer - FES
>
> http://www.front-electric-sustainer.com
>
> http://www.youtube.com/watch?v=TNOKq6PKIvM
>
> Regards,
>
> Luka Znidarsic

I've got an empty engine bay in my Apis, always thought an electric
motor would be a nice thing to put in there. The doors for the prop
can handle a 46" dia. blade.

Brad

[Eric Greenwell]

AndersP wrote:
> I would like to have the batteries in my wings though. The idea of
> having a solid block of metal/lithium/what not behind my back in a
> crash is a bit scary. But I guess at these weights its not worse than
> having your average Solo behind you.
>
> But if I would wish, that would be my option.
A self-launcher, like my ASH 26 E or a DG 800, has about 130 pounds of
metal behind you, plus another 30 pounds of fuel. It doesn't seem to be
a problem.

I think it is probably better to have the 50 pounds of batteries in the
fuselage than in the wings, where it is easier to remove them, and they
don't have to be connected each time the glider is rigged. The design
problem for retrofitting will be the loss of allowed cockpit weight.
Newer gliders, that are already designed for two stroke sustainers, will
have enough "non-lifting parts" weight allowance so that adding the
electric system will not diminish their allowed cockpit weight.

Judging by the information on the website, it looks like a very well
done solution for a sustainer equipped glider.

--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly

* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org

[kirk.stant]

This looks like a natural for a single blade prop, folding flush into
a contoured recess in the bottom of the nose.

I like it!

Kirk

[LimaZulu]

On 1 nov., 17:07, Darryl Ramm > wrote:
> On Nov 1, 4:29*am, Andy > wrote:
>
>
>
> > On Nov 1, 1:49*am, LimaZulu > wrote:
>
> > > First flight of Front Electric Sustainer - FES
>
> > >http://www.front-electric-sustainer.com
>
> > >http://www.youtube.com/watch?v=TNOKq6PKIvM
>
> > > Regards,
>
> > > Luka Znidarsic
>
> > If I read the specs right you can operate at full power for 14.4
> > minutes over which time you can climb a bit over 4,300 feet. *How's
> > that compare to other sustainers? *This seems simpler than most other
> > configurations which is nice.
>
> > 9B
>
> It would be interestingly they claim level flight for 120km which is
> greater distance than a 4,300' climb will normally allow you to glide.
> Just plucking numbers out of thin air of 50 knots for optimal climb
> and cruise speeds (I expect climb would be slower) and an L/D of 50:1.
> You would travel 22 km in the climb and glide 65km for a total of
> 87km. It would require a L/D > 74 to match the straight cruise. The
> exact optimal speeds and the profile of the climb as battery power
> diminishes likely affects all this.
>
> Looks like nice packaging. I am curious as well what happens to the
> forward air cockpit air vent, nose pitot tube, nose tow hook, and
> where cooling air for the engine comes from (presumably the nose
> hole). At 95% efficiency the 15kW motor will generate 750W.
>
> Darryl

Dear Darryl,

Data published are pesimistic version of calculated values. For real
data we must do more flights in calm conditions.
-Forward cockpit air vent is still used, air just goes also trought
the motor to cool the engine. And will be possible to close it during
gliding, but must be opened when engine is running
-Nose pitot tube is replaced with fin tube otherwise used for TE (TE
compensation tube was replaced with electronic compensation, and same
hole used as pitot). Flight test shows that this works just fine, as
airspeed is correct.
-LAK17a has front tow hook placed bellow instrument panel
-95% is efficiency of motor+controler. Motor have good cooling, and it
not looks that heating will be a problem. It is just warm and
controler is rated for much higher power and is not even warm.

regards,

Luka

[Martin Gregorie[_5_]]

On Sun, 01 Nov 2009 09:51:45 -0800, kirk.stant wrote:

> This looks like a natural for a single blade prop, folding flush into a
> contoured recess in the bottom of the nose.
>
That would be nice to see from a propeller efficiency point of view too,
because the prop could be bigger while absorbing the same power. The
bigger the prop the more efficient it is. Propeller ground clearance
would be irrelevant for a sustainer system.

I remember seeing an Antares 20E and an ASW-22ble launch within 10
minutes of each other, so the ground and air conditions were very
similar. The ASW-22 has 49hp (36 kW) and (I think) a 0.9m diameter prop
while the Antares swings a 2m prop with a 47 kW motor. The Antares was
off the ground in about 1/3 the run the '22 needed and climbed out at
least twice as fast. I don't know how the takeoff weights would compare,
but if they're not too different the additional 30% power output in the
Antares wouldn't account for the takeoff and climb out difference I saw,
but the different props could easily do it. A two blade prop is rather
more efficient than a 5 or 6 blade unit and the almost 5:1 difference in
swept area would make a big difference to drive efficiency, especially at
low speeds.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

[Martin Gregorie[_5_]]

On Sun, 01 Nov 2009 11:51:45 -0800, LimaZulu wrote:

> -LAK17a has front tow hook placed bellow instrument panel -95% is
> efficiency of motor+controler. Motor have good cooling, and it not looks
> that heating will be a problem. It is just warm and controler is rated
> for much higher power and is not even warm.
>
I noticed your web site comments about eliminating the drag from the
pylon and engine, but didn't mention the effect that the pylon would have
on propeller efficiency. Since your prop is a similar size to a
conventional sustainer prop, have you calculated effect on prop
efficiency of moving it from the pylon to the nose?


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

[AndersP]

kirk.stant wrote:
> This looks like a natural for a single blade prop, folding flush into
> a contoured recess in the bottom of the nose.
>
> I like it!
>
> Kirk

Another good idea from the model world :-). Needs a hefty counterweight
at those dimensions of spinner (small) and prop (large) though.

/AndersP

[Andy[_10_]]

On Nov 1, 7:07*am, Darryl Ramm > wrote:
> On Nov 1, 4:29*am, Andy > wrote:
>
>
>
>
>
> > On Nov 1, 1:49*am, LimaZulu > wrote:
>
> > > First flight of Front Electric Sustainer - FES
>
> > >http://www.front-electric-sustainer.com
>
> > >http://www.youtube.com/watch?v=TNOKq6PKIvM
>
> > > Regards,
>
> > > Luka Znidarsic
>
> > If I read the specs right you can operate at full power for 14.4
> > minutes over which time you can climb a bit over 4,300 feet. *How's
> > that compare to other sustainers? *This seems simpler than most other
> > configurations which is nice.
>
> > 9B
>
> It would be interestingly they claim level flight for 120km which is
> greater distance than a 4,300' climb will normally allow you to glide.
> Just plucking numbers out of thin air of 50 knots for optimal climb
> and cruise speeds (I expect climb would be slower) and an L/D of 50:1.
> You would travel 22 km in the climb and glide 65km for a total of
> 87km. It would require a L/D > 74 to match the straight cruise. The
> exact optimal speeds and the profile of the climb as battery power
> diminishes likely affects all this.
>
> Looks like nice packaging. I am curious as well what happens to the
> forward air cockpit air vent, nose pitot tube, nose tow hook, and
> where cooling air for the engine comes from (presumably the nose
> hole). At 95% efficiency the 15kW motor will generate 750W.
>
> Darryl

I mis-read the projected climb as 1.5 m/s instead of 1.6. This still
leaves total climb capability a bit over 4,500 feet so the straight
cruise must get more out of the motor than a sawtooth, though I am not
clear why this would be true.

9B

[vaughn[_2_]]

"Andy" > wrote in message
...
> This still
>leaves total climb capability a bit over 4,500 feet so the straight
>cruise must get more out of the motor than a sawtooth, though I am not
>clear why this would be true.

One good reason is because the whole electrical system, especially the
battery itself, is more efficient when operated at lower currents. At
higher power outputs, a greater percentage of the battery's precious stored
energy turns into waste heat, so less of the battery's stored energy is
available to actually propel your aircraft..

Vaughn

[Andy[_10_]]

On Nov 1, 2:49*pm, "vaughn" >
wrote:
> "Andy" > wrote in message
>
> ...
>
> > *This still
> >leaves total climb capability a bit over 4,500 feet so the straight
> >cruise must get more out of the motor than a sawtooth, though I am not
> >clear why this would be true.
>
> One good reason is because the whole electrical system, especially the
> battery itself, is more efficient when operated at lower currents. *At
> higher power outputs, a greater percentage of the battery's precious stored
> energy turns into waste heat, so less of the battery's stored energy is
> available to actually propel your aircraft..
>
> Vaughn

True - though I was under the impression that a sawtooth profile is
more efficient for the overall glider-motor system. I'm at a loss as
to why the cruise mode for this system would produce nearly twice the
range of the sawtooth - at least according to math on the various
specs quoted.. The electric motor would have to REALLY hate being run
full out.

9B

[Greg Arnold]

Andy wrote:
> On Nov 1, 2:49 pm, "vaughn" >
> wrote:
>> "Andy" > wrote in message
>>
>> ...
>>
>>> This still
>>> leaves total climb capability a bit over 4,500 feet so the straight
>>> cruise must get more out of the motor than a sawtooth, though I am not
>>> clear why this would be true.
>> One good reason is because the whole electrical system, especially the
>> battery itself, is more efficient when operated at lower currents. At
>> higher power outputs, a greater percentage of the battery's precious stored
>> energy turns into waste heat, so less of the battery's stored energy is
>> available to actually propel your aircraft..
>>
>> Vaughn
>
> True - though I was under the impression that a sawtooth profile is
> more efficient for the overall glider-motor system. I'm at a loss as
> to why the cruise mode for this system would produce nearly twice the
> range of the sawtooth - at least according to math on the various
> specs quoted.. The electric motor would have to REALLY hate being run
> full out.
>
> 9B


If I go bike-riding, it is a lot easier to go around the hills than to
go over them. If I am driving a car, my gas mileage is better when I go
around hills rather than over them.

What is it about sustainer gliders that causes them to be different? Of
course, the sustainers that we have now have engines that run too fast
for sustained cruising, have a pylon creating a lot of drag, etc. But
eliminate those problems, and isn't it more efficient to cruise at a
constant altitude?

[Darryl Ramm]

On Nov 1, 6:56*pm, Greg Arnold > wrote:
> Andy wrote:
> > On Nov 1, 2:49 pm, "vaughn" >
> > wrote:
> >> "Andy" > wrote in message
>
> ....
>
> >>> *This still
> >>> leaves total climb capability a bit over 4,500 feet so the straight
> >>> cruise must get more out of the motor than a sawtooth, though I am not
> >>> clear why this would be true.
> >> One good reason is because the whole electrical system, especially the
> >> battery itself, is more efficient when operated at lower currents. *At
> >> higher power outputs, a greater percentage of the battery's precious stored
> >> energy turns into waste heat, so less of the battery's stored energy is
> >> available to actually propel your aircraft..
>
> >> Vaughn
>
> > True - though I was under the impression that a sawtooth profile is
> > more efficient for the overall glider-motor system. I'm at a loss as
> > to why the cruise mode for this system would produce nearly twice the
> > range of the sawtooth - at least according to math on the various
> > specs quoted.. The electric motor would have to REALLY hate being run
> > full out.
>
> > 9B
>
> If I go bike-riding, it is a lot easier to go around the hills than to
> go over them. *If I am driving a car, my gas mileage is better when I go
> around hills rather than over them.
>
> What is it about sustainer gliders that causes them to be different? *Of
> course, the sustainers that we have now have engines that run too fast
> for sustained cruising, have a pylon creating a lot of drag, etc. *But
> eliminate those problems, and isn't it more efficient to cruise at a
> constant altitude?

There will always be drag/inefficiency from the prop itself. But how
significant that is needs a back of the bigger envelope than I have
handy.

In addition to what you already mentioned, most sustainers and some
self launchers run two stroke engines. They have a noticeable
powerband, so you run them in that band and climb (if you are
lucky..). They often just wont run reliably at lower RPM, will oil up
plugs etc.

The electrics are a whole different kettle of fish. The sustainer here
has the advantages of electrics (being able to run at reduced power)
and prop optimization for sustainer use only (the prop does not need
to handle self launch).

The electrics have the benefit of not having to worry about mixture
settings at altitude, somethign many self launchers or sustainers
cannot deal with except by adjustment on the ground. I hope the people
making this produce some performance data for high density altitudes
(~10,000'). Around mountains 'out-west' most sustainers are next to
useless.

Darryl

[Martin Gregorie[_5_]]

On Sun, 01 Nov 2009 19:14:52 -0800, Darryl Ramm wrote:

> The electrics have the benefit of not having to worry about mixture
> settings at altitude, somethign many self launchers or sustainers
> cannot deal with except by adjustment on the ground. I hope the people
> making this produce some performance data for high density altitudes
> (~10,000'). Around mountains 'out-west' most sustainers are next to
> useless.
>
Judging from the performance of free flight models at Denver vs the same
models at Sacramento, the FES should be better than an IC sustainer. Its
noticable that power models lose performance big-time at Denver while
rubber powered models are much less affected. Now doubt this is due to
the way an IC engine loses power with altitude while electric or rubber
motors are unaffected.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

[Andy[_10_]]

On Nov 2, 2:36*pm, Martin Gregorie >
wrote:
> On Sun, 01 Nov 2009 19:14:52 -0800, Darryl Ramm wrote:
> > The electrics have the benefit of not having to worry about mixture
> > settings at altitude, somethign many self launchers or sustainers
> > cannot deal with except by adjustment on the ground. I hope the people
> > making this produce some performance data for high density altitudes
> > (~10,000'). Around mountains 'out-west' most sustainers are next to
> > useless.
>
> Judging from the performance of free flight models at Denver vs the same
> models at Sacramento, the FES should be better than an IC sustainer. Its
> noticable that power models lose performance big-time at Denver while
> rubber powered models are much less affected. Now doubt this is due to
> the way an IC engine loses power with altitude while electric or rubber
> motors are unaffected.
>
> --
> martin@ * | Martin Gregorie
> gregorie. | Essex, UK
> org * * * |

Really good point - I believe it's true that most of the power loss
with altitude is from loss of power produced by the engine, not prop
efficiency. Electric motors don't have this power loss because they
don't depend on combustion.

9B

[Mike the Strike]

So how does rubber (or modern synthetic varieties thereof) compare on
an energy storage per mass basis with lithium/ion batteries? We use
them for bungee launches - how about powering a sustainer?

I have this vision of a large coil of rubber between my legs powering
a slow-turning single-bladed prop!

Mike

[Martin Gregorie[_5_]]

On Mon, 02 Nov 2009 15:47:40 -0800, Mike the Strike wrote:

> So how does rubber (or modern synthetic varieties thereof) compare on an
> energy storage per mass basis with lithium/ion batteries? We use them
> for bungee launches - how about powering a sustainer?
>
Good quality rubber strip stores around 3000 ft/lb per pound of rubber.
Sad to say, I've completely forgotten how to convert that to something we
could compare with a battery, say to kW/kg.

> I have this vision of a large coil of rubber between my legs powering a
> slow-turning single-bladed prop!
>
That sounds potentially as dangerous to valued objects as snapping the
drive shaft of a P.39 Airacobra.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

[Craig[_2_]]

On Nov 2, 4:37*pm, Martin Gregorie >
wrote:
> On Mon, 02 Nov 2009 15:47:40 -0800, Mike the Strike wrote:
> > So how does rubber (or modern synthetic varieties thereof) compare on an
> > energy storage per mass basis with lithium/ion batteries? *We use them
> > for bungee launches - how about powering a sustainer?
>
> Good quality rubber strip stores around 3000 *ft/lb per pound of rubber..
> Sad to say, I've completely forgotten how to convert that to something we
> could compare with a battery, say to kW/kg.
>
> > I have this vision of a large coil of rubber between my legs powering a
> > slow-turning single-bladed prop!
>
> That sounds potentially as dangerous to valued objects as snapping the
> drive shaft of a P.39 Airacobra.
>
> --
> martin@ * | Martin Gregorie
> gregorie. | Essex, UK
> org * * * |

If I've calculated correctly (and I may not have) 3000 ft-lb/lb of
rubber = 8,965 joules/kg of rubber. So a 100 kg rubber band would
store 896.5 kilo joules of energy which expended over 60 seconds
provides a stunning power output of (drum roll please) 15 kw. It
would be damn exciting on a FF model, but probably not practical as a
sustainer.

Craig

[Uncle Fuzzy]

Would that be 1987 Pirelli?? I've heard that sometimes FAI Tan is
comperable. I seem to recall a man-carrying rubber powered plane
making an attemp in the late 1980's or early '1990's.
>
> Good quality rubber strip stores around 3000 *ft/lb per pound of rubber..
> Sad to say, I've completely forgotten how to convert that to something we
> could compare with a battery, say to kW/kg.
>

[Martin Gregorie[_5_]]

On Mon, 02 Nov 2009 17:25:56 -0800, Craig wrote:

> On Nov 2, 4:37Â*pm, Martin Gregorie >
> wrote:
>> On Mon, 02 Nov 2009 15:47:40 -0800, Mike the Strike wrote:
>> > So how does rubber (or modern synthetic varieties thereof) compare on
>> > an energy storage per mass basis with lithium/ion batteries? Â*We use
>> > them for bungee launches - how about powering a sustainer?
>>
>> Good quality rubber strip stores around 3000 Â*ft/lb per pound of
>> rubber. Sad to say, I've completely forgotten how to convert that to
>> something we could compare with a battery, say to kW/kg.
>>
>> > I have this vision of a large coil of rubber between my legs powering
>> > a slow-turning single-bladed prop!
>>
>> That sounds potentially as dangerous to valued objects as snapping the
>> drive shaft of a P.39 Airacobra.
>>
>> --
>> martin@ Â* | Martin Gregorie
>> gregorie. | Essex, UK
>> org Â* Â* Â* |
>
> If I've calculated correctly (and I may not have) 3000 ft-lb/lb of
> rubber = 8,965 joules/kg of rubber. So a 100 kg rubber band would store
> 896.5 kilo joules of energy which expended over 60 seconds provides a
> stunning power output of (drum roll please) 15 kw. It would be damn
> exciting on a FF model, but probably not practical as a sustainer.
>
So that's 0.25 kWh by my reckoning. By contrast the LAK FES installation
carries two 3.6 kWh batteries.

I make that rubber 0, electric 1


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

[Martin Gregorie[_5_]]

On Mon, 02 Nov 2009 17:59:21 -0800, Uncle Fuzzy wrote:

> Would that be 1987 Pirelli?? I've heard that sometimes FAI Tan is
> comperable. I seem to recall a man-carrying rubber powered plane making
> an attemp in the late 1980's or early '1990's.

That value was from a 2008 NFFS Sympo paper for Tan 2. I don't fly
rubber, preferring 50m of towline or a screaming Cyclon 06, but IIRC Tan
2 is now about as good as the best Pirelli and the Tan SuperSport is
coming pretty close too.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |