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Old Mar 29, 2013, 02:28 PM
Cheese eating monkey.
France, Bretagne, Rennes
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BBCC4 - A 1/12 Pou du ciel (Flying flea) - Panoramix

I am going to have a try at the BBCC2 and this is the thread to document my build.

Since being fascinated by one as a kid, I always liked the "pou du ciel". This is my first attempt at building a plane out of Balsa and I've only built one foamy. So I am right at the deep end!

I found this plans : http://outerzone.co.uk/plan_details.asp?ID=431 which I can nearly understand.

Controls
The incidence of the front wing needs to be controlled for pitch, at the moment I am thinking of a bellcrank as below, the rudder is traditional.

Covering
Not being experienced, I want to go the easy way, and the moment Aerolite / so-lite seems to be the easy way.

I need to be doing more thinking, the polyhedral and the structure of the body of the plane is still not clear to me...

I also need to find info about the COG which isn't on the drawings.

Expect a lot of questions...
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Old Mar 30, 2013, 07:04 AM
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Norfolk, England
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Be wary of that tilting forward wing control. They banned the original because of accidents caused by it. What was happening was that the control could be used to put the aircraft into a dive, but not get enough incidence to get out of the dive again. IIRC, and no doubt someone will comment if I'm wrong, they moved the control to the rear wing to solve the problem.

Pete
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Old Mar 30, 2013, 08:10 AM
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Definitely a cool design to convert. With the tiny motors available today, I bet you could figure out how to make a nice slow indoor flier. I would think that relocating control to rear would still be in the spirit of the contest. JMO
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Old Mar 30, 2013, 08:29 AM
UMs & parkflyers... for now.
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There is a "Crossley Flea" at the USA's Smithsonian Air and Space Museum Udvar-Hazy Center, located at Dulles Airport near Washington DC. I am pleased to live about 3 miles from Udvar-Hazy and have been known to visit at the drop of a hat... any hat.

Here are some pictures I took of the Crossley Flea. It appears to use the bellcrank attachment to the forward wing's trailing edge. If more photos will help, I will be happy to take them...
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Old Mar 30, 2013, 06:07 PM
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Hundreds of "Fleas" of all types - those designed by Mignet over his long career, and those designed by others - have been flying safely with the front wing as the moveable surface. The moveable rear wing was a temporary fix until they understood the real problems, which had to do with the spacing and gap between the wings, incidence angles, and CG.

I've designed and flown several "Fleas", and here are the basics:

Incidence - When rigging the front wing, ensure that it can't go beyond 0 deg. negative when the stick is pushed forward. On this design, I wouldn't go more that 8-10 deg. positive when the stick is pulled back.

CG - Measure the total distance from the leading edge of the front wing to the trailing edge of the rear wing. The CG should be 25% of this distance back from the leading edge of the front wing.

Wing Gap & Spacing - The usual rule of thumb is 1/2 the wing chord between the trailing edge of the front wing and the leading edge of the rear wing. On this design, that's not practical if you still want to retain a scale like look. The vertical spacing should also be about half the wing chord as well. On this design I'd raise the front wing another 25% at least, preferably 50%.

Check out these Stevens Aero designs - http://www.stevensaero.com/StevensAe...4-p-20354.html

http://www.stevensaero.com/StevensAe...t-p-20593.html

I designed both of them, and they fly great. Study the downloadable build manuals to see how I approached setting up the controls for the front wing.

Good Luck!!

Mark
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Old Mar 30, 2013, 07:34 PM
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I knew someone would come up with all the gen. Just thought it best to warn a novice builder of a potential problem. Especially since to remain scale it can't embody the points Mark has raised. It is the layout it is, not necessarily the ideal layout. I also can't help feeling that a total rework isn't really in the spirit of the comp. It would no longer be the same model.

Pete
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Old Mar 30, 2013, 08:46 PM
Visitor from Reality
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This is going to be fascinating. Though I've got quite a few reference books on Fleas various - the best is an English language paperback of Mignet's book on how to build one - the only models I've had were two from the same 049 powered free flight plan.

My European kit of a small RC Flea, I prefer not to think about... The Stevens kits appear to work fine, should be a good starting point.

Idle thoughts. Mignet never addressed the diving thing because he never thought to dive a Flea - he just took power off and down it came. The first pilot killed by the diving syndrome was a RAF fighter pilot, who would have known a thing or two about flying...

What happens is that the dive entry is done by raising the TE of the leading wing - no sweat. What caused the problem was when the pilot pulled back on the stick to exit the dive, the forward wing TE came down and caused increased air pressure over the rear wing, thus increasing its lift and tipping the nose down even more. Next big snag - pulling harder became physically impossible at some point, but the harder the pilot pulled, the steeper the dive got. At which point, whichever way the pilot moved the pitch control, he was in a real bad place.

The 'fix' was to couple the two wings, so that as the front wing TE dropped, so did the LE of the rear wing, thus keeping the two wings airflows seperate enough to avoid that pitch down causing lock-up.

Which has probably nothing to do with model Fleas...

Fitting elevators to the back wing would make it a conventional model with a real big tailplane If you made the rear wing smaller, you'd end up with something like a Lazy Bee!

Wish I'd had the time to finish up the quarter scale one I half-built back in England many years ago, but life got in the way of that one. It was the English built 'Carden Baynes' variant with the longer span front wing and a much nicer cowled in engine than the usual fully air-conditioned flat twin routine.

There is a lot of online info - start with : http://en.wikipedia.org/wiki/Mignet_Pou-du-Ciel then cut Google loose on the type.

My favourite cute story, with a little bragging Way back in England, one of my Royal Air Force aeromodelling clubmates was Andy Sephton. Andy gave up RC flying as too easy and then introduced UK aeromodelling to 'Pistachio scale' - 9" span rubber powered scale models. His day job was as a RAF, then Rolls-Royce, test pilot for the Harrier VTOL aircraft, but in his remaining spare time, he was chief pilot at the Shuttleworth Collection air museum at Old Warden, just north of London. He had licenses to fly about any aircraft they had and every single engined WW2 fighter airworthy in England on the side.

Shuttleworth had a HM-14 Pou that mostly hung out in a hangar for people to shake their heads at, but I was at a full sized airshow there once when they hauled it out, fired it up and Andy taxied it around the airfield for a while to show it off to the spectators. Later, I ran into him and asked him why they didn't fly it - it was technically airworthy, like most of the Shuttleworth Collection's aircraft.

His response - 'None of us are stupid enough".

Model Fleas are much more easy going.

Your plan - no idea what it flies like, but it is quite scale and it is the longer front span Carden Baynes variant. The wing section is actually pretty accurate in FF scale terms, but the spars are not made as per the originals - Mignet water soaked the spar ends, then bent them up in a curve. That model plan's dihedral looks to have been moved to include more of the span and perhaps increased some too.

The pitch control rods on the front wing are missing the control arms too. Pitch control mechanism was basically a tube welded to the bottom of the control stick, with single horns on its ends operating pushrods to the wing rear spar on either side of the fuselage.

If you want to get really technical, the rudder bar actually is hooked up to the tailwheel spindle, which also has the rudder on it.

If you really want documentation: http://www.amazon.com/Henri-Mignet-F.../dp/0854297650 (mine's not for sale!)

And the real word:
http://www.amazon.com/s?ie=UTF8&fiel...Henri%20Mignet (am starting to think about EBay'ing mine!)

Google'ing the Flea is much cheaper

Good luck with your project, will be following with interest.

Dereck
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Old Mar 31, 2013, 12:37 PM
Cheese eating monkey.
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Wow, I am away and on my phone so can't reply in detail but this place is amazing. The info especially on incidence and cog is invaluable.
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Old Mar 31, 2013, 04:42 PM
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Interesting history surrounds this truly bizzare looking little airplane!
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Old Mar 31, 2013, 05:53 PM
Visitor from Reality
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Quote:
Originally Posted by conrad907 View Post
Interesting history surrounds this truly bizzare looking little airplane!
Very true - and it's not over. Their are still Fleas flying and folk keep on building new ones. Not too long ago, someone in the US who sold plans of their full sized Flea also sold a package suitable for scale modeling from. It was based on Mignet's HM16 'ultralight' Flea. I have that package in my Flea file. The first drawing in it defines the 25% total chord CG just as Fleaz describes above.

My free flight Flea (Flea Flight?) had close to 'scale' wing separation in both vertical and horizontal planes. Both flew fine and were stable, though all they did was go round in circles. Which is all about what any Flea should do, really.

D
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Old Apr 01, 2013, 06:09 AM
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I think, though my opinion means little, that each entrant has selected his model for any of several reasons. If for instance a guy wants to build. Flea as a very maneuverable, indoor slow flyer. And after adding several ounces of power and control electronics he needs more wing area to lift it at low speed or wants to slave the main wing to an elevator servo for added control, and in the end gets a model that performs the way he wants, I believe he has remained within the spirit of the competition.
If the point is to build a scale model and live with its quirks, well that's another story.
Good luck Panoramix however you decide to proceed.
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Old Apr 01, 2013, 05:12 PM
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Quote:
Originally Posted by Dereck View Post
If you really want documentation: http://www.amazon.com/Henri-Mignet-F.../dp/0854297650 (mine's not for sale!)

And the real word:
http://www.amazon.com/s?ie=UTF8&fiel...Henri%20Mignet (am starting to think about EBay'ing mine!)
Both of these books pop up on Ebay from time to time. Original copies of the Mignet's "Flying Flea and How to Build It" book in english come up occasionally, and the Other one pops up from time to time at around $35.00 - much less than the $106 advertised on Amazon. In fact -


Mark

(My copies are not for sale either!)
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Old Apr 01, 2013, 05:13 PM
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http://www.ebay.com/itm/Henri-Mignet...item20d0e769fb Messed up the link.....
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Old Apr 01, 2013, 05:27 PM
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Another plan worth considering... http://www.atomicworkshop.co.uk/cata...roducts_id=272
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Old Apr 01, 2013, 07:31 PM
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Ken,
I agree totally, as long as it still looks like the original model. Afterall, this is a conversion contest, not a design your own contest. Once, however, you start messing with wing positions and the like it alters the very nature of the model. To me that just sounds more like a redesign than a mere conversion. It actually becomes a purpose designed model.
It's just how I see it, but changing structural features slightly to suit the new purpose is acceptable. Changing the geometery of the model is another matter entirely. It does, of course, all depend on the individual's interpretation of 'conversion'.
I'm not suggesting that a converted control-line model should only fly in left hand circles, but I do feel the model, of whatever type, should fly in a similar manner to the original model.

As I say, that's just my take on it. No doubt David could be persuaded to define it more precisely.

Pete
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