Fauvel musings

Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by cluttonfred, May 13, 2017.

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  1. May 17, 2017 #41

    Victor Bravo

    Victor Bravo

    Victor Bravo

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    I have to stick to my guns on this one. Admittedly there's far more brain cells floating around here than I have, but I'm invoking a wise old concept that "if it looks right..." The AV-36/Pelican configuration looks right, and it is known to fly right. An aluminum Pelican was, and is, on my short list of airplanes to create. So all of the ideas and concepts in this discussion have already been banging around and weighed against each other in my aching head.

    Using a tractor configuration will just make the airplane larger and more complex than it needs to be in this case. There are plenty of times where the pusher configuration creates more problems than the tractor, but for this exercise I think not:

    1) A tractor engine, mounted low enough to not ruin half of your visibility, will require a longer landing gear.

    2) A full VW will use a little larger propeller , raising the height of the landing gear even more.

    3) A pusher propeller can be mounted slightly higher, in this case pilot's eye level, because the forward visibility is not affected. The thrust line has to be angled a few degrees (through the CG), but this is a very very small loss of thrust at these angles. So this makes it easier to use a mono-wheel and simple outriggers or "training wheels" under the Fauvel fins to allow takeoff without a sailplane "wing runner".

    4) A pusher engine can have the exhaust and other components mounted in the wing or in the fairing above the trailing edge.

    5) A tractor engine will move the pilot rearward, in order to balance the aircraft, and also because the engine is taking up the space where the pilot's feet would have been. Even if for balance alone, this makes the aircraft larger (longer) in order to balance itself out.

    6) Moving the pilot rearward results in either the spar not being straight anymore, or the pilot sitting on top of the spar. If you crank the spar and sweep the wing forward (as with many flying wings) then the whole mess becomes more complex to engineer and build. If the pilot sits on top, this increases the aircraft's fuselage volume (drag, intersection drag, etc.). It also results in a low wing airplane, which results in an even longer, heavier, draggier landing gear.

    7) The Pelican configuration allows the pilot seat to be hung right from the main spar. No long load paths, no cantilevered beam to mount the seat on, etc.

    As for the discussion of the U-2, it is also a neat airplane. But it is not fair to constrain the Pelican to a one piece wing and the U-2 to a three piece wing. Either airplane could be built either way. You could build a Pelican with tip panels the same as a U-2. You could also build a Pelican where the center section span was just under the maximum trailer width... 7 feet or whatever. You could leave the center section at 8 feet and just bank the airplane 30 or 40 degrees on the roll axis, keeping it within the trailer width limits. There was a famous photo of a Formula One Cassutt racer that went to the race on a trailer like that. (Raceair, do you remember this? I saw the photo years ago in one of the old race annual books.)

    In my version of this, the original Pelican design would be skewed just a little to address the big difference between Debreyer's original mission (sustained flight on minimum power) and my mission (easy to build, fuel efficient, inexpensive, but still able to operate like a "normal" airplane in real-world conditions). This is easy enough, because Debreyer started out with a very thick wing section to save weight and make lift. For my mission, the airplane doesn't need to be as light, and it doesn't need as much lift. So I can move away from the 17% thick section and go back to a slightly thinner one. Maybe 13-14%, I would have to ask one of our HBA high brain function types for the right number. It is also possible that one of Dr. Hepperle's airfoil sections would offer some advantages over the original Fauvel/Debreyer sections. Again, that is something I would have to research (translate: ask someone more educated than me).

    (NO, there is no need for a truly high performance airfoil on this aircraft, no Wortmann helicopter blade airfoil, it will not be built in a way that justifies that. Pop rivets, oil-canning wing skins, and probably overlap seams.)

    Using a slightly thinner airfoil will yield some modest improvement in cruise speed, but the flight characteristics and pitch behavior are far more important. If this is a 70 MPH airplane on 35HP, that is plenty good enough.

    Anyway, rant switch off, those are the reasons that I would favor the Pelican layout over the others for this particular mission.
     
    Last edited: May 17, 2017
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  2. May 17, 2017 #42

    Hot Wings

    Hot Wings

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    I share that same head banging affliction....:gig:
    An aluminum Pelican/Vampyre using similar construction to the other Pelican/Lazair/Superfloater seems to me to be a natural fit.

    Agreed that either could be built either way. But if you are going to use folding or removable tips then something with higher aspect ratio then the Pelican seems to start making sense. There could be very little difference in weight for a moderate increase in aspect ratio. As Norman noted most U-2's end up well over the 254 103 weight limit, but they need not be so heavy. The prototype weighed much less and there is a lot of weight that could be removed from a plans built U-2. But I don't want to derail this thread with much more U-2 talk.

    A flying wing, of either the Fauvel or U-2 formula, can be folded to not much more than half of it's span - close to a third if you are willing to have extended hinge points on one wing and overlap more. Making the decision between folding wings and trailering span-wise, or removable wings and trailering longitudinally, isn't an easy or simple one.

    A removable nose cone sacrifices some crash protection. Folding the engine/prop up to shorten the length to legal numbers, while at first glance seems kind of absurd, just might be another option.

    As for Junkers style stabilators, there is no reason they couldn't be adapted to the Pelican.

    ........back to U-2 CAD work.
     
  3. May 17, 2017 #43

    plncraze

    plncraze

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    I wish there were some AV222 plans floating around....
     
  4. May 18, 2017 #44

    Riggerrob

    Riggerrob

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    .......

    A removable nose cone sacrifices some crash protection. Folding the engine/prop up to shorten the length to legal numbers, while at first glance seems kind of absurd, just might be another option.
    ....[/QUOTE]
    ---------------------------------------------------

    If you carve the nose fairing from the correct grade of styrofoam, it can help gradually decelerate the cockpit, reducing injuries during a during botched landings.

    During the ISO 20 challenge, I sketched an ultralight with foam-filled nose fairing that HINGED to the size to reduce (crew) pod length to the 7-ish feet maximum width that can fit inside an ISO 20 shipping container. I much prefer hinged components because they are more difficult to lose and quicker to unfold to flying configuration.
    If you plan to fold wings, then fold them 3.5 feet (1 metre-ish) from the centre-line. This will make the wing root 7-ish feet wide but still narrow enough to trailer. Because spar loads decrease logarithmically the farther outboard, 1/3 span hinges can be built for a fraction of the weight of wing root hinges.
    In the interests of safety, all control linkages should be permanently attached and only need a quick visual inspection before take-off. Hint: install Plexiglas inspection panels near all control linkages, bell ranks, fold lock pins, etc.

    Yes, I know that I sound opinionated on wing-fold mechanisms, but my opinions are based on 6 years experience folding and unfolding Sikorsky Sea King helicopters, sometimes from flight decks narrower than the rotor disc.

    Also consider mounting all control surfaces outboard of the propeller disc. Wide-spread control surfaces will help reduce the worst disadvantage of pusher deltas. A few pusher deltas have crashed when throttled back and turbulent prop-wash blanketed trailing edge control surfaces.
     
    Last edited: May 18, 2017
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  5. May 18, 2017 #45

    cluttonfred

    cluttonfred

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  6. Oct 2, 2019 #46

    Hot Wings

    Hot Wings

    Hot Wings

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    This has apparently changed. From one of my e-mail contacts regarding the AV-36:

    Do you know Alpaero in Gap Tallard,France, Mr Noins? He

    markets his "Choucas" a lightend AV 222 as an UL motorglider about 15 (kits) are sold, 3 should fly,one of these 3 in Quebec.

    I'll leave it to those interested to follow up as they desire.
     
  7. Oct 2, 2019 #47

    plncraze

    plncraze

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    The Choucas has been out there awhile. Unfortunately it is a kit with all the associated costs.
     
  8. Oct 4, 2019 #48

    Blackshire

    Blackshire

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    Indeed. The Fauvel AV.22 (another variant of it is called the AV-22S; here is a 2-meter wingspan R/C model plan of it: https://www.sarikhobbies.com/product/rm210-fauvel-av-22s/ ), and here (see: http://www.nurflugel.com/Nurflugel/Fauvel/e_AV22.htm ) are pictures of, and information on, the full-scale ones, and:

    I have long thought of the AV.22's potential as a *safe* Haig Minibat-like (see: https://en.wikipedia.org/wiki/Haig_Minibat ) tailless glider with the capability of having--like the Minibat--an optional sustainer engine (or electric motor, today; sustainer power plants, of course, are much easier to install--"regulation-wise"--than power plants capable of self-powered takeoffs), whose small, non-folding two-bladed propeller would also rotate in a narrow space between the vertical stabilizer and the rudder. The prop could be stopped (or "kicked over") so that it would lie in the narrow gap, to greatly minimize its drag during gliding and soaring flight. Also:

    With all of the simple, tiny, and relatively inexpensive turbojets that available today (see: https://minijets.org/en/home ), Fauvel fans who are so inclined could fit their gliders with jet engines. In fact, even the larger turbojets that are made for R/C model jets could suffice as sustainer engines for Fauvels. (An AV.45, in fact, was powered by a tiny Microturbo Eclair turbojet [see: http://www.nurflugel.com/Nurflugel/Fauvel/e_AV45.htm ], which enabled self-powered takeoffs [the AV.46 http://www.nurflugel.com/Nurflugel/Fauvel/e_AV46.htm was a tandem two-seater that closely resembled the AV.45 and the "progenitor" AV.36 http://www.nurflugel.com/Nurflugel/Fauvel/e_AV36.htm ].) In addition:

    Another interesting "trick," which--I think, in the U.S.--gets around the sustainer vs. self-takeoff-enabling power plant matter (the principle could also be applied to propeller-driven motor gliders), was pioneered by the British ProAirsport GloWfly (see: https://minijets.org/fr/0-100/amt-titan/proairsport-glowfly and http://www.proairsport.com/project-glow.php ). It has a very small turbojet engine (with a faired, inside-fuselage installation), and its dual-wheeled, retractable main landing gear "truck" is powered by a brushless electric motor. This enables the GloWfly to taxi by itself on the ground, and (with the turbojet and the powered wheels working in concert) to take off under its own power; in the air, the turbojet suffices to maintain altitude and to climb, when desired. And regarding obtaining construction plans for the Fauvel tailless gliders:

    This Wikipedia article about the AV.36 (see: https://en.wikipedia.org/wiki/Fauvel_AV.36 ) says that "Plans for the AV.36 have not been available in France since Fauvel's death in 1979, but as of 2012 they are still available from Canadian supplier Falconar Avia of Edmonton, Alberta." (Here https://en.wikipedia.org/wiki/Falconar_Avia is a Wikipedia article on Falconar Avia [their website is: http://falconaravia.com/ ].) They recently closed due to the death of Chris Falconar, the owner, last year--*but* Leon McAtee of Excogitare LLC (e-mail: bd5er@aol.com ) bought the rights to Falconar Avia's Fauvel plans (they had the plans for the AV.36 and AV.361; they also built at least one AV.362). The Falconar Avia website lists the firms (including their contact information) that bought the rights to their various aircraft series' plans.

    I hope this information will be helpful.


    Sincerely Yours,


    James *Jason* Wentworth
    Fairbanks, Alaska
     
    Last edited: Oct 4, 2019
  9. Oct 5, 2019 #49

    daniel leclere

    daniel leclere

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    GOOD! SOMEONE ELSE LOOKING FOR A JDC 03 PELICAN BUILT OF WOOD. THE NEWER KIT DESIGN ELIMINATED MOST OF THE ADVANTAGES OF THE ORIGINAL. IT IS ALSO NOTEWORTHY IN THAT THE PELICAN WOULD BE A GOOD CANDIDATE FOR ELECTRIC POWER ONCE THE NEW BATTERIES HIT THE MARKET. THE BATTERIES: LIFEPO4 FROM CHINA ARE SUFFICIENT TO DO THE JOB NOW. LARGE DRONE MOTORS ARE EFFICIENT. BUT USING LAWN MOWER ENGINES AT THIS TIME ALLOWS US TO BECOME FAMILIAR WITH THE DESIGN AND TRANSITION TO ELECTRIC AT A LATER DATE. THE BRIGGS 12 HP FLAT HEAD IS A GOOD CANDIDATE FOR THE PELICAN. DEPENDABLE WHERE THE ROTAX IS NOT. MY ROTAX TREATED ME TO A COLD SWIM ASHORE IN THE SALT CHUCK. WHILE THINKING HOW MUCH MORE DEPENDABLE WAS OUR SNAPPER 12 HP LAWNMOWER ENGINE THE PELICAN SHOULD WORK WELL WITH THAT BRIGGS. THE PELICAN HAS LOOKED SAFER THAN THE HIMAX WIT THE 503 IN IT. ALSO NOTICE THE TOUCH DOWN SPEED OF THE PELICAN IS WELL BELOW FATAL.
     
  10. Oct 5, 2019 #50

    Aerowerx

    Aerowerx

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    No need to shout, Daniel. Check your caps lock;).
     
  11. Oct 6, 2019 #51

    daniel leclere

    daniel leclere

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    not shouting... only one operational hand. lazy so i just play it as it lays... there seems to be a lot of people thinking things trough on this site. well here is another very strange thought; has anyone used one of those plastic radiator fans from a large pickup truck ( stranger still they come in left or right rotation) and bolt it to a flange on a briggs and stratton engine and see what kind of thrust it delivers. they are impressive looking ,cheap, durable( think a splash of water into the fan at full speed and the blades are still there) yes a longshot but infinitely better than the lotto. and just how much thrust is required for a jdc 02? along with the speed range required?
    all wood jdc is the plans i seek,, wood is good! and plastic resin glue( weldwood) could be used as the composite resin of choice along with microballoon and fiberglass shorts for re-enforcement and filler working on wooden boats gives one strange thoughts on using wood in an aircraft. safety of the wood "scantlings" is assured by testing before use is easily . before a thins wood strip is used bend it by hand in each direction. if there is a flaw: crack, off grain or say rot pocket it will kink or break at the flaw. flaws can't hide from this. feel free to apply this test to any wood that is cheap and available i realy like wood for aircraft and be sure to familiarize yourself with DAP plastic resin glue( weldwood to us old timers. hellL i bet it would work on fiberglass cloth in place of epoxy it is much harder.( this must be taken into ac count though. my father a wooden boat builder all his life was using wedged seams between planks and :weldwood glue. one day when planing the wedge stips down and fairing them in found the glue run-out drops actually chipped his hand plane blade. many boats using weldwood can be found to survive many years for inspection having been tested in the harshest of conditions( oil, water. fuel, salt water and various finishes. yes! i have confidence in wood and weldwood glue growing up in a shipyard where wooden boats are constructed allows one to observe wooden construction subjected to the harshest conditions ( fishing fleet in the pacific ocean) wood! by all means get wood! they say; it will be fun. a fellow i know built a hatz biplane used epoxy for glue. one day when i visited him he said come here and look at this! he had a picture puzzle someone finnished it had left over epoxy poured over it and the epoxy had drawn itself out of the edges of each piece and made a very nice glossy surface on each piece of the puzzle. he with his hands proceeded to tumble all the pieces as they were loos and not stuck together in any way. disturbing he exclaimed! never expected that!
     
  12. Oct 6, 2019 #52

    Aerowerx

    Aerowerx

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    This is urea formaldehyde wood glue , and is sold by Aircraft Spruce for aircraft construction.

    It has been used for a long, long time, but there is a reason why most wood aircraft builders now use epoxy.

    A quick glance at the datasheet shows that it requires more clamping pressure than epoxy. With most epoxies you just need to be sure that the two surfaces are in contact, and epoxy can be used over a wider temperature range (down to 60 degrees for T88, for example, IIRC.)
     

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