Napkin sketches

Discussion in 'Hangar Flying' started by Autodidact, Mar 28, 2017.

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  1. Oct 4, 2017 #201

    cluttonfred

    cluttonfred

    cluttonfred

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    Here you go: Between-the-war aircraft replicas I agree that some of those Japanese designs are gorgeous. Not quite as racy but with that perfect Tintin cartoon look to my eye is the Tachikawa Ki-36/Ki-55, love the narrow rear fuselage and big wheel pants.

    Unmarked_Tachikawa_Ki_55_(7880769176).jpg



     
  2. Oct 5, 2017 #202

    Aesquire

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    Thank you. I agree the aesthetic of the late pre-war/early war Japanese designs are nice. Fineness ratios and shapes.
     
  3. Oct 5, 2017 #203

    ScaleBirdsScott

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    Doodled this on the flight home from Geneva

    6cd598f4-734b-43fe-90e4-9a7416ae5a39.jpg
     
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  4. Oct 6, 2017 #204

    mcrae0104

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    Trojan Starlet?
     
  5. Oct 6, 2017 #205

    cluttonfred

    cluttonfred

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    Neat, Scott, very pretty, but the tail looks more modern than the rest to my eye, maybe it needs more curves.
     
  6. Oct 6, 2017 #206

    Autodidact

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    I like the classic-mixed-with-modern look of this thing, Verner powered (?) aerobatic plane, with old school Gee Bee style scallops with some hot rod flame vibe mixed in - very European/Russian at the same time...pretty cool looking idea! Deserves to be made real IMO.
     
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  7. Oct 6, 2017 #207

    Bill-Higdon

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    Looks more like a Ducted fan Starlet
     
  8. Oct 6, 2017 #208

    ScaleBirdsScott

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    Yeah, I was just going for something not obviously just a P40 type round tail, and go for the hybrid look; but, rounded would probably look better. It almost definitely would need more rudder area anyway.


    And yes, my concept was take the sort of aluminum frame and wing I've designed to do the P36, sporterize it with the better modern geometries, use fabric wherever possible while keeping aluminum cantilever construction to minimize weight and build difficulty, and run it on a Verner 5VW or O-100 type powerplant.
     
  9. Oct 6, 2017 #209

    cluttonfred

    cluttonfred

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    I like it a lot and wouldn't want it to become too generic, maybe just rounding out the existing design into more of a leaf shape, still with the little point, would work, something like the Blériot-SPAD S.510 rudder shape?

    Gs510.jpg Cs510.jpg

    http://www.avionslegendaires.net/avion-militaire/bleriot-spad-s-510/ (more pics)

     
  10. Oct 7, 2017 #210

    ScaleBirdsScott

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    Something like this maybe?

    6cd598f4-734b-43fe-90e4-9a7416ae5a39.jpg
     
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  11. Oct 7, 2017 #211

    cluttonfred

    cluttonfred

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    Yes, I like that a lot better, though this feels a bit like hanging pictures with my wife. "A little to left, no, back a little, now up some...." ;-)
     
  12. Nov 12, 2017 #212

    Autodidact

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    More elaborate than a 2D sketch, but it is Sketchup, and more interesting than a simple line drawing. I was going to wait until it was all done but there are so many little details and they seem to take the most time and effort.

    This is the Gere Sport, and I've tried to make it as per the Flying & Glider manual drawings where they are explicit and winged it where they said wing it (such as control bell-crank ratios), but there are some things there that just don't work - much less are bad design - so I've also used the R. Parks drawing that was made in 1969 (I think...). I did not draw the engine, but took it from a car model available in the Sketchup 3D warehouse drawn by PAV:

    inprogGere.jpg taildetail.jpg headertank.jpg cablepulley.jpg rudderpedalspring.jpg
     
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  13. Nov 13, 2017 #213

    Autodidact

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    Interesting detail of the fin and the rudder hinges; the fin adjusts for yaw trim and the rear fin tube fits inside the tail post and rotates in it with the adjustment. The upper two rudder hinges (there are three) are welded to the fin and the bottom hinge is attached tp the tail post...and if it is welded, then when the fin is adjusted the upper two hinges rotate out of plane from the bottom one, so I (figuratively speaking, of course) decided to clamp the bottom hinge to the rudder post instead of weld it. I know that most modern (post war) homebuilts just use a rudder tab and a fixed fin:

    findetail.jpg hingedetail1.jpg hingedetail2.jpg
     
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  14. Nov 13, 2017 #214

    Joe Fisher

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    That should be a fun airplane. It looks like it is intended to have folding wings with the vertical bolts in the wing fittings.I would expect the fuel tank to need straps all of the way around the spars. The tabs you have will break real fast. Are you thinking heal brakes,I like heal brakes better than toe brakes in tail dragers.
     
  15. Nov 13, 2017 #215

    Autodidact

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    I've just been trying to draw it as per the drawings that I can find. I know that the few modern built examples have had different wing attach fittings (I think these are prone to binding when the wires stretch under load). As is, there are no brakes, just a tail skid and presumably a big field... If I were going to build one, I think I would borrow the wing attach fittings from the EAA Biplane. According to the plans, that's actually a water header tank (although the F&G Manual recommends putting both fuel and water tanks in the center section) and I agree with you that it is not good enough with just those tabs - there are lots of things that I think need a little revision on what is basically an OK design. Here's a link to a modern Australian built example - if you enlarge some of the photos, you can see some differences from the old plans, like the lower wing fittings: http://www.rotecradialengines.com/customers/DavidShaw.htm
     
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  16. Nov 16, 2017 #216

    Autodidact

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    Airdrome-Baslee type cantilever spar.

    Talk of the Airdrome-Baslee pop riveted structure got me thinking about this; Airdrome is already making a similar type spar for some of their biplane designs and claims thay are lighter and stronger than single tube spars. Theirs is a simply supported beam and has tubes for the caps and shear webs riveted to the sides like the one I have here - all I did was taper it and add a nested tube. It may need 3 or 4 internal stiffeners to keep the tubes from "rolling" under some conditions. Tubes make good spar caps and have very good buckling strength and I think this spar would be light and strong, although Scalebirds may have looked into this and have more knowledge about the strength/weight of it. I just eyeballed this, it's just a concept:

    A-Bcantspar.jpg A-Bcantspar1.jpg A-Bcantspar2.jpg A-Bcantspar3.jpg
     
  17. Nov 16, 2017 #217

    Topaz

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    More common is stock aluminum angles instead of tubes. Taper them over their length to reduce weight, and rivet to the (single) shear web, making a "C" or "I" beam, depending.
     
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  18. Nov 16, 2017 #218

    ScaleBirdsScott

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    We looked at using square tube with pull rivets, see if there was anything there. But decided that for a cantilever wing it was definitely a more secure option to use driven rivets over pulled rivets, and that precluded some kind of tube like that. While a box spar is GREAT in overall geometry, the realities of fastening is why we ended up going with a more straightforward laminated spar because that makes it really easy to stack and taper as you go outboard, and it is straightforward to drive the rivets.

    But we did look into all that. Using tubes is nice, and baslee does use that on his stuff (though his planes are wire braced) we just decided to look towards the RV, the Sonex, the Thatcher, the Mustang II, and other similar examples to develop spars from since that takes a bit of the uncertainty out of the game.

    I would be curious to know more about examples of cantilever wings with pull rivets though.
     
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  19. Nov 17, 2017 #219

    mcrae0104

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    But it's no fun not to reinvent the wheel!

    (BTW, I am a dyed-in-the-wool wheel reinventer. No offense, Autodidact.)
     
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  20. Nov 17, 2017 #220

    Jay Kempf

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