Nenadovitch sounds like Russian. It is. But he lived in France.
I found very little about this man. But he is definitely worth
mentioning in the tandemwing pages. He inspired a few true
tandemwing designers.
I need to thank Paul Deweer, Pierre Mignet and Christophe
Meunier for the info I have.
First a short overview of the history to better understand the
reason why Nenadovitch invented his "tandemwing".:
- The idea of tandemwings was already invented by Langley in
1903. But his full-scale design didn't fly. It broke in the air
just after being launched by a catapult. But his flying model
proved that heavier-than-air powered machines were possible. Later
Curtiss and Bell rebuilt a Langley airplane and flew it
succesfully. (Thanks to Kenneth Ketner for these new facts)
- Before World War 1 there were a lot of experiments with
tandemwings. For instance, Bleriot, Anthony Fokker make a
experiment. But again ... no success.
- The first breakthrough came in France. Louis Peyret made a
tandemwinged glider which won a international contest.
- In the 1930's there were a lot of transportation proposals by
Albessard. He made a similar tandemwinged airplane in 1913 (I was
unable to find any info about that one). Anyway, ... none of the
proposals was built. You can find the patent using patent number
1,627,004 .
But, all designs had the same problem. The first wing affected
the rear wing. This came to view when the airplane changed its
angle of attack. In other words, when the pilot raised or lowered
the airplanes nose. Flight behavior went from good to VERY bad. The
prototypes were very dangerous airplanes to fly due to that
problem. [Note: later I got a mail from Eric Cousin, who flew a
large Peyret model. He wrote that he didn't encounter that
problem]
Nenadovitch searched and found a solution to this problem. He
raised the position of the front wing. It made that the
interference of the front wing towards the rear wing changed.
Instead of a bad interference it became a good interference.
"Huh?", you think. To better understand I translated a part of the
book of Henri Mignet "Le sport de l' Air".
°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°
PART OF BOOK "Le Sport de l' Air" by Henri Mignet.
(with permission of Pierre Mignet. I made it a bit my own
version of the original)
Slotted wing
Normally the air sticks to the upper surface of the wing. Stall
is that moment where the condition of the wing is such (low speed,
high angle of attack and so) that the air cannot longer stick onto
the upper surface of the wing. Normally a wing start to fall like a
brick at this point. Not so healthy!
Question: What will happen if you place a wing near the
end of the stalling wing? (Condition is that the second wing has
not reached stall)
Answer: The second wing has a area of low pressure on
its back. Place a area of high pressure nearby and the air will be
sucked towards the low pressure area. (This happens too at the
wingtips and there they create the "vortex")
Here you see two wings.
The front one is having troubles.It is in stall. The air no longer
follows the upper side of the wing, it is in turbulence..The second
wing is in a normal condition.Under the wing there is a area of
high pressure, above it is a area of low pressure.
Ever opened a door inside a house when there is a door open at
the front and the back? Well, what do you get? DRAFT! A strong air
current. It is created by differences in air pressure. Yep, there
can be a difference in air pressure between the frontdoor and the
backdoor. Henri Mignet tells here a bit the same about wings. The
air runs from high pressure to low pressure.Now look at the drawing
above. Each wing has a high pressure area and low pressure area.
High pressure below, low pressure above. Watch closely. The area of
the lower side of the front wing and the upper side of the rear
wing are close to each other. What do you expect? Right ... draft!
The air from the lower side of the front wing runs quickly towards
the upper side of the rear wing.
"OK, but what now about that stall thing?", you ask. Just look at
the drawing above. See the draft between both wings? Now, the
current takes also part of the air from the upper side of the front
wing with it. "Hey, was that air not in turbulence?", you ask. Yes,
but now no longer. It starts to flow towards the rear of the second
wing. To do this ... it has to follow the upper side of the front
wing. TATAAAA. Stall delayed!
Stability by shape
The air over the rear wing is ... secondhand. Already used. It has
run over and under the front wing and has slowed down a bit and
changed a bit in direction (a bit more downwards). Due to these
changes the rear wing is less effective. To increase efficiently,
you need to put the wings further apart.
You have two ways of making those wings further apart:
Henri Mignet made use of both ways. His moving front wing made
the voluntary way possible. Nenadovitch only used the automatic
way. Let's look at it more closely. Look the drawing below.
Both drawings have the same fixed wing combination. But the first
one is pointing a bit downwards (small negative angle of attack)
and the second one has a large positive angle of attack (=angle
between wing and wind direction).
The first condition has a gap (gray area) which is smaller than
when the airplane would be flying straight forward. The gap is
smaller, so the efficiency of the rear wing is less. The tail of
the airplane sinks. The airplane returns to its normal
position.
The second condition has a larger gap (gray area) and a
resulting more effective rear wing. It has more lift than normal
and it pushes the tail of the airplane upwards.The airplane returns
to its normal position.
Spoken permission to use parts of "Le sport de l' Air" by
Pierre Mignet granted at the meeting in Montpezat in 2002.
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I hope you now better understand the good stuff about this kind
of tandemwing. Nenadovitch used his tandemwing with a classic
horizontal tail. Maurice Delanne and Henri Mignet drove the idea
further into a pure tandemwing. No more classic horizontal
tail!
On this page I can show a few more airplanes, which flew, and
who use the Nenadovitch concept with a horizontal tail like
Nenadovitch did.
Christophe Meunier mailed me a quote of a article about later
designs with a Nenadovitch wing configuration. Pity, it was not
noted from which source it came. Anyway, I translate:
"Eliminating the risk of loss of speed, longitudinal
autostability, easy steering and low costs. These advantages are
part of a four-seater design by Jacques Lagarde. It was built by
the atelier Bordeau. The designers inspiration came from the work
of "Institut Aéronautique de Saint-Cyr" (Institute of aerodynamics
of Saint-Cyr) about the brevet (=patent?) of Nenadovitch. The
prototype (F-WEPK) [webmaster: probably the Milet-Lagarde ML10] was
followed by the S.C.A.M. C50 "Milane" II (F-WEAI). Flight tests
were done by Gérard Henry in Cormeilles-en-Vexin."
It is not clear in the text which airplane was tested by this
pilot.
Millet - Lagarde ML. 10 (probably F-WEPK)
- Span 10 m
- Speed (maximum) 235 km/h
- Length 8 m
- Speed (cruise) 210 km/h
- Height 2,70 m
- Ceiling 6000 m
- Wing area 30 m2
- Range 2000 km
- PT (Weight total??) 1600 kg
I received these three pictures from Jaap Zwart. He gave me
permission to use them. Thanks, man. :)