Penrose Gremlin

Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by plncraze, Jul 23, 2013.

  1. Jul 23, 2013 #1

    plncraze

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    1952 | 0415 | Flight Archive Give this link a few moments to load. It has a picture of Harold Penrose's "Gremlin." I know at least one person here will be excited by this so enjoy!
     
  2. Jul 24, 2013 #2

    cluttonfred

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    That person might be me, the tandem-wing freak! I have posted about the Penrose Gremlin in numerous discussion groups and tried for years, without success, to learn anything more than what is contained in that brief article. I did manage to track down a brief RAE report on the Delanne-style Westland Lysander P.12 which inspired the Gremlin, but that's it. Someday...

    gremlin.jpg + p12.jpg = ?
     
  3. Jul 24, 2013 #3

    Head in the clouds

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  4. Jul 24, 2013 #4

    Aircar

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    Penroses's biography includes some of his test flying experiences with the tandem Lysander and talks about his ideal personal plane (he also authored a book about the Henson and Stringfellow aircraft "An ancient air" well worth reading.

    Matthew - I just got my local paper (Maroondah Leader ) with the advert stating that the new Basywater Officeworks has just opened for business --google if you like --I will do my best to get there and double side copy the Lysander tandem report and get it to you.
     
  5. Jul 24, 2013 #5

    Autodidact

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    Someone should make a movie of Airymouse. The Henson and Stringfellow book was a very good read.
     
  6. Jul 24, 2013 #6

    cluttonfred

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    Neat stuff, though perhaps an example of how you can patent almost anything if you have a good lawyer. I dont' see any fundamentally unique features of this design that weren't already covered by numerous previous tandem wing aircraft, including several by Delanne. There is also the Sunny Boxwing ultralight (great site, by the way, especially using Google Chrome for translation on the fly), developed in the 1980s but with its origins in experimentation going back to at least 1979, developed independently of the Delouise designs as far as I know.

    Aircar, thanks for remembering, no worries.
     
    Last edited: Jul 24, 2013
  7. Jul 24, 2013 #7

    cluttonfred

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    What book is that?
     
  8. Jul 24, 2013 #8

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  9. Jul 24, 2013 #9

    plncraze

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    Matthew, I thought you would enjoy that picture. I think the Gremlin would be a neat design except that the prop is located in the middle of the aft wing. According to Franklin Kurt who wrote an article on pusher props in Sport Aviation years ago, if you have the propwash anywhere but at the back of the wing it will slow the flow down over that wing with any reduction in power. What caught my eye in the article was that not only had the stress and performance work been done on the design but that Penrose was looking for a good light engine. Where did he donate his papers to when he died? There might be some plans floating around.
     
  10. Jul 24, 2013 #10

    cluttonfred

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    I have tried without success to locate the Penrose papors--Westland archive, RAeE Yeovil, National Archives, no luck. If anyone has a lead, I'd be grateful.
     
  11. Sep 12, 2013 #11

    cluttonfred

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    Thanks to Aircar, I now have the original Westland flight test report on the Lysander P.12 to add to my earlier find of the brief RAE handling report from the UK National Archives. So, once again, I have visions of Delanne-type light planes on the brain....

    I am thinking tractor engine , so a bit like a cross between the Penrose Gremlin and the Westland P.12 but with tricycle gear. The configuration lends itself well to small subassemblies for working in a modest workshop, and a small complete aircraft. Going with constant-chord wings of slightly lower aspect ratio, I come up with about 24' span for the front wing and 16' span for the rear wing not counting the vertical fins, which would be all-moving and differential for low-speed authority. Pilot-first tandem seating is possible due to the wide CG range with the resulting high-wing tandem looking a bit like a Cub with the "Delanne treatment." Side-by-side seating lends itself to a bubble canopy with a parasol front wing and a definite Mignet/Croses look about it.

    Any thoughts on what might work well and look good in such a set-up? I am having trouble coming up with an attractive rear fuselage design. Maybe I'll need a gun turret after all. ;-)
     
  12. Sep 12, 2013 #12

    plncraze

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    In Darrol Stinton's book "Design of the Aeroplane" he said tht Delanne style aircraft seemed to have a higher low speed to high speed ratio than other configurations. Does the Westlands' report say anything about this or have any other interesting pieces of info?
     
  13. Sep 12, 2013 #13

    cluttonfred

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    I just got it today, will let you know when I've had some time to really look through it. ;-)
     
  14. Sep 13, 2013 #14

    Aircar

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    Enjoy the read Matthew:nervous: Hope it was worth the wait . I built a model tandem wing with a parasol front wing (very much Mignet formula) and flew it as a glider satisfactorily --the fuselage was the front of a 1/5 scale of my Opal with a horizontal knife edge to the pod (with the spinner on the centreline ) --the trailing edge of the rear wing was a continuation of the fuselage TE . It looked quite nice . I wire braced the tips of the front wing to the tips of the rear wing fins so that the wires were nearly horizontal and hence no drag . (that stiffened the front wing in the yawing plane greatly - and allowed for pitching the whole front wing easily in a second iteration . I did a later VTOL version that is hard to describe but had the wings connected by two booms with the engines and props at the front and which 'morphed' into VTO mode by the rear wings sweeping forward as the front ones angled up resulting in the booms vertical and the rear wing trailing edge being parallel to the ground and forming a forward facing V in planform (a wide stability base but I worried that the downwash being 'coralled' by the rear wing might also result in sudden pitch down near the ground --the Zimmerman flapjack suffered from that and needed a big flip up elevator to counter it.

    Roadable times includes the tandem wing design shown a few posts back also.
     
  15. Sep 13, 2013 #15

    cluttonfred

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    According to Harald Penrose in his autobiography, while the conceptual inspiration for the Westland P.12 was actually the Mignet Pou-du-Ciel, the practical model was the Delanne DL-20T. Penrose and Westland Chief Designer Teddy Petter visited Maurice Delanne in Paris just months before the German invasion, discussed the design with him and flew the DL-20T. And yes, the DL-20T did have a remarkable 37-162 mph speed range, though it also had automatic leading edge slats on the main wing and a variable pitch prop. Still, that's a fantastic range for 2273 lb gross weight and 180 hp with a strut-braced wing. For comparison, a 180 hp 2200 lb Aviat A1C Husky with a constant speed prop has a speed range of 53-145 mph.
     

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  16. Sep 13, 2013 #16

    plncraze

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    What is striking about this design is how it would allow the designer to use the firewall as a major structural point for the wings with a little adjustment and the rear passenger would end up sitting on the spar ala Bonanza. Why is the speed range so much greater for the Delanne?
     
  17. Sep 16, 2013 #17

    cluttonfred

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    Random thought--I can see a lightplane of the general configuration of the Westland P.12 (single tractor-engine Delanne tandem) making an excellent little bush plane, cargo plane or air ambulance, from a tandem two-seater for camping and fishing on up to a turboprop utility single like a Cessna Caravan. By using a swept rear wing you could shorten the fuselage to the point that the hinged tailcone could serve as the rear loading door and out-of-limit loading would be pretty much impossible. Think "Westland P.12 meets Miles M.57 Aerovan" to get an idea of what I mean.
     

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  18. Sep 17, 2013 #18

    Aircar

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    I did wonder about the use of slats on the front wing in terms of the stall behaviour (the rear wing basically 'droops' as the speed slows and thereby increases it's lift in the Pou De Ciel formula but with a fixed front wing and radical changes to the front airfoil and it's zero lift angle that simple balance thing cannot occur -- I must re read that report I guess ;)

    Julain Wolkovitch designed a stepped tandem for Vought (as a carrier ASW aircraft) and as good as admitted (to me in 1990) that that was the origin of his joined wing design --the poorly supported rear wing (virtually a huge T tail ) was stabilized by connecting it to the front in effect . The Cdi figure (`"e") was quoted as .6 which is the same as a Prandtl plane which it actually is -- that is, 60% of the induced drag of an 'equivalent' monoplane.

    When my neighbour gets back from Italy (his kid can post photos unlike me --and no internet as yet ) I will post some pictures of my "Airbike" flying motorcycle design -and full size mock up from 1987 --using a Delanne like config with swept rear wing with tip fins as you described but with a pusher prop and the rider crouched as normal with elbows within the swelled wing root of the foreplane . needed a hub centre front suspension and towed it's wings on the road .
     
  19. Sep 17, 2013 #19

    cluttonfred

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    Thanks, Ross. Yes, the slats are puzzling but the Lysander already had them and Delanne's own designs also used them. I suspect that the slotted-flap effect of the two wings keeps the flow smooth over the rear wing as long as the front wing keeps flying, and the slats allow the front wing to keep flying at a higher angle of attack. For a lightplane the slats do seem a needless complication.

    There is definitely some experimenting to be done on the optimum control surface arrangement for a Delanne type. Some, like elevons on the front wing, seem like an obviously bad idea in terms of likely stall behavior but there are still many, many possibilities, especially when you add in flaps and the possibilty of both wings working together as ailerons or flaps or contrary to each other as elevators. The combination that appeals to me for simplicity's sake is full-span flaps on the front wing and full-span elevons on the rear wing, with trim tabs or spring trim to compensate for any pitch change when flaps are deployed. But that remains to be tested--I should start playing with X-Plane.

    I have looked at joined wings, too, but like the Delanne for it's potentially simpler construction, especially at lower aspect ratios. I wonder if the Wolkovitch design you had in mind was in fact this one from Grumman?

    Cheers,

    Matthew
     
  20. Sep 18, 2013 #20

    Aircar

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    Matthew, I could only open one of the linked papers on that site --the grumman tilt Nacelle is NOT the one done by Wolkovitch -it (the Grumman one) is a conventional aft tail --I did a model with a canard and props at the gull wing break of that general configuration (with a buried lift fan for hover balance in the nose ) The Vought design was essentially an "unjoined" joined wing of Wolkovitch type -simply unsweep both wings and there you have it --the rear "T tail" looks very floppy given that the pylon/fin is supporting an equal sized and same span wing as the low nose end one. It was in a Journal of aircraft paper that I can relocate if it was important.
     

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