P-51C at ~70% scale as ultralight?

Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by J.L. Frusha, Apr 30, 2019.

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  1. May 2, 2019 #21

    J.L. Frusha

    J.L. Frusha

    J.L. Frusha

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    Not such on the original airfoil. Could narrow the aft fuselage like the FlyBike(?), or some of the really old-school attempts, before FAR 103.

    Obviously, I am open to doing it a LOT different than a strict copy. Stand-Off scale, cartoon scale, etc. I would prefer as light an airframe as possible and have several ideas to explore...

    This is NOT an aerobatic aircraft. Simply a for-fun flyer.

    I can think of several ways to attempt this without all this hoopla. Mind you, I asked about ply-skinned foam, right off the bat.

    I WOULD like help, if it's available. I freely admit I have a very limited knowledge of airframes and my powerplant school was in '81/'82.
     
  2. May 2, 2019 #22

    mcrae0104

    mcrae0104

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    If you build a Mustang like that, your plane and my avatar should do some formation flying.

    Also, check out Blackheart Art.

    [​IMG]
     
  3. May 2, 2019 #23

    Saville

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    Perhaps to save weight you could design a simple battery cart and start up from there. Precludes in -flight starts, but it would save weight.
     
  4. May 2, 2019 #24

    pictsidhe

    pictsidhe

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    Hand propping is even lighter. I'd prefer electric, but it's on my luxuries list. The one I won't be too upset to skip items from if I have weight issues...
     
  5. May 2, 2019 #25

    pictsidhe

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    As far as design goes, I've already got some structural engineering under my belt, but it wasn't with planes.

    I'm designing mine to FAR 23, pre 2017. I have a few reasons for doing that.

    1, It's a sensible set of design rules. It covers a lot of things that I either haven't thought of, or don't want to design from scratch. I may well bend a few rules a little bit (10%) if exact compliance would be a large weight penalty.

    2, I'd like to design other, bigger planes down the line. It is good to get into the FAA groove.

    3, I grabbed a copy of FAR AMT 2015 for $5 delivered from Amazon. I like paper reference books!

    The are other sets of design rules you could use.

    Propastie is using the The FAA basic glider criteria.

    The European CS-22 glider rules looks excellent for 103 design.
     
  6. May 2, 2019 #26

    J.L. Frusha

    J.L. Frusha

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    With the slightly elongated chord and belly line of the fuselage, the GAW-1 airfoil is an excellent candidate and a beautiful fit, as well.

    Granted the following is a STOLCH/Storch like aircraft,with the high wing, but doing the math makes it look more feasible. Inboard slotted flaps and fixed LE slats?... I'm more committed to getting it within concept and Part 103, with some structural margin of safety, than fighting a list of who's-who and nay-sayers.

    Weight in the pdf is more than double the 254 lbs of an ultralight, so loadings would be much lower.

    The Hovey Whing Ding II had 4 - 2"x2" (nom) Spruce spars per side and meets FAR 103 w/o having webbing between vertically places spars, so, reimagining it with wings similar to ordinary Balsa-model style rib/multiple spars w/sheeting over construction CAN be a viable possibility. So did the South American variant Pamperito, but with foam ribs.

    Can we focus on what CAN be done, stop deciding how many ways it can fail?

    https://ojs.cvut.cz/ojs/index.php/ap/article/download/744/576


    Seems I'm going to be quite busy with another project, all of a sudden, but I'm determined that this can happen and move forward, design wise, in the meantime.
     
  7. May 2, 2019 #27

    pictsidhe

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    I'm using 4 digit thickness profiles with combined 6 series camber lines. I could send you a pair of airfoils to use once you know taper ratio and thicknesses. the GAW-1 has a very high moment, you'll need a much larger tail. It's Cl also drops as Re falls, so having a tip and root foils both GAW-1 is going to invite tip stalls on a P-51 taper. Despite using a fairly smooth hard skin,
    I'm not optimistic about getting laminar flow from mine. I wouldn't get a temendous benefit anyway.
    I'll be using scale split flaps and 114sqft of wing area. I think it will make the stall requirement. If not, my last click of flaps can activate flaperons.
     
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  8. May 4, 2019 #28

    J.L. Frusha

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    How did your Watson Windwagon/Hummel Bird turn out? I would like a set of both plans to go over as part of the research process.
     
  9. May 4, 2019 #29

    12notes

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    My suggestions is to build a Hummel Ultracruiser, use a much lighter engine so you can stretch the nose, taper the rudder at the top without changing the area, and add a removable "baggage pod" on the bottom for the "air scoop". If you use something like the Simonini Mini 3, you'll save 40 lbs over the half VW, letting you stretch the nose about a foot and a half. The baggage pod can be removable to save weight, but probably should be jettisonable on first flight in case it causes too much drag on the bottom of the plane.

    Other than the horizontal stabilizer being in the wrong place, the side view will be pretty close.

    [​IMG]
    [​IMG]
     
  10. May 4, 2019 #30

    radfordc

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    If you squint hard that might work.
     

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  11. May 4, 2019 #31

    J.L. Frusha

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    Not too long ago, I was emailing with an artist about Republic of Texas Markings he had suggested. Not sure who had requested them, but he had several with some of his ideas, so I came up with my own and even made a carricature that would scale shorted than the Hummel. It might actually work with the series electric hybrid as I mentioned ealier.[​IMG]

    The Yahoo Group for the Watson Windwagon actually has a lot of info and plans for it. Since Jeanie's Teenie, Teenie Two and the Hummel Ultracruiser are all variants of the Windwagon, that might be the place to start. Use some of the old Balsa models of the P-51 to get the bulkhead shapes, go from there?
     
  12. May 4, 2019 #32

    pictsidhe

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    I am considering a baggage pod for my hurricane. It will be jetisonable in case i need to make a water landing. Lakes will be the only available flat surface in many parts of the smokies. As a removeable baggage pod that isn't required fir flight, it won't count towards the 254lb either.
     
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  13. May 4, 2019 #33

    12notes

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    Any ultralight P-51 replica will likely require a bit of squinting.
     
  14. May 4, 2019 #34

    12notes

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    Actually, the Teenie Two was first, the Watson Windwagon was based on it, and the Hummelbird (not the Ultracruiser) was a modification of the Windwagon. The Ultracruiser was based on the Hummelbird, the fuselage is similar but the wing design is different.

    I'd just use the Ultracruiser/Windwagon bulkhead shapes unless you want to redo the structural calculations. They're both oval shape, it's close enough as is, I don't think it would be worth the effort.

     
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  15. May 4, 2019 #35

    radfordc

    radfordc

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    This was my P-51-ish plane. Tons of fun.

    Joesie 4.jpg
     
  16. May 5, 2019 #36

    Tiger Tim

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    I know a Sindlinger Hurricane that went for a swim, stayed upright on touch down, and was subsequently restored to fly again. All this with a fake radiator scoop on the belly. You may not have to deal with the weight and complexity of making yours jettisonable.
     
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  17. May 5, 2019 #37

    J.L. Frusha

    J.L. Frusha

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    Easy to get confused with all the older articles having different supposed 'facts'...

    Still, I HAVE plans for the Windwagon, so modifying those would be far easier and cheaper than buying the various other sets of plans and picking through all of the changes, though going taildragger is a MUST.

    I've got thicker a/c grade Aluminum, anyway, and will need to add stringers, to help with the tailwheel change.

    As for recalculating, everything, I don't see much point. For one, I am planning to use thicker Aluminum.
     
    Last edited: May 5, 2019
  18. May 5, 2019 #38

    pictsidhe

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    As a baggage pod, I will want to access it. the simplest way to do that is to make it removeable. Simple hooks at the back, some kind of catch at the front. On the ground, the catch is released from within a wheel well. It won't be too tricky to have a 2nd release in the cockpit. Being somewhat behind the cg, it won't be good for much weight so it won't need much strength. Bulky things like sleeping bags seem the best use for it.
     
  19. May 5, 2019 #39

    pictsidhe

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    Why are you using thicker aluminium?
     
  20. May 6, 2019 #40

    J.L. Frusha

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    Because I'm crazy, not stupid...

    Bulkheads will be larger and differently shaped, not small, pretty round things. They'll concentrate stress differently and I don't want them deforming. Additional structural members will have to be added to support the load as a tail-dragger, as well.

    Haven't studied the wing, yet, so I'm not sure how the original LG is mounted, or what changes to that design will be necessary, but I see no reason to go from fixed LG to retractable. Wasted effort and unnecessary increase in complexity and weight, IMHO. Probably use something more like the mini-mustang style LG w/wheel pants, though not the full cover modern style. More likely the aft style from the '20s-'40s...[​IMG]
     
    Last edited: May 6, 2019

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