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. Apr 30, 2019 #1

    J.L. Frusha

    J.L. Frusha

    J.L. Frusha

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    I know I don't know enough, so I'm asking. There are plenty of folks in here that can give an educated opinion and I'd like to know...

    I like the P-51C Mustang III with the Malcolm Hood as used by both the RAF and the US AAC (Mighty Eighth did, for certain).

    Using foam-core plywood sandwich and plywood over foam skin, could a P-51 C be built at ~70% scale and be an ultralight?

    Rather than a larger engine, I was thinking a "series-elecrtic hybrid" could provide sufficient power at a significant weight savings, using one of the newer free-piston linear generators.That would allow the generator to be placed in the aft fuselage, to help with weight and balance, as well. I was also thinking, maybe stretch the root wing cord a bit, too, as shown below.

    I've copied and adapted P-51B Mustang III images, as well as a P-51D Cockpit from a DIY simulator, all scaled together.

    Excuse my crappy MS-Paint adaptation. It's what I know how to use.

    LOA 25 ft 3 in
    Span 26 ft 5 in

    [​IMG]
     
  2. May 1, 2019 #2

    don january

    don january

    don january

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    With a LOA of 25.3 and Span of 26.5 I don't thing you can stay under the 254 lb rule.
     
  3. May 1, 2019 #3

    J.L. Frusha

    J.L. Frusha

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    For comparison...

    Home Depot Ultralight: aka "Motor Glider 101"



    Specifications:
      • Wing Span: 28' 6"
      • Wing Chord: 5' 0"
      • Gross Wing Area: 142 1/2 sq. ft.
      • Dihedral: 3" from Fuselage to Wing Tip.
      • Tail Span: 6' 6"
      • LOA: 15' 8"
      • Height: 6' 0"
      • Wheel Track: 4' 10" - Center to Center
      • Empty Weight: 254 lbs
      • Gross Weight: Not established, however pilot flew prototype with 5 gallons fuel, pilot weight 225 lbs.
      • Maximum HP: Not Established
      • Prototype Power: (2) Tecumseh 10hp 4 Stroke Engines or (2) 227 Rotax.
      • Fuel Capacity: 5 US Gallons.
      • Endurance: (2) Techunesh engines consume approx. 1 gph.
      • Cruise Speed: 55 mph @ 2600 rpm.
      • Landing Speed: 35 mph.
      • Landing Rollout: 100'
      • Stall Speed: 30 mph
    • Rate of Climb: Slow but steady with (2) 10 hp motors. Will maintain level flight on one engine.
     
  4. May 1, 2019 #4

    Kyle Boatright

    Kyle Boatright

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    The Lohle 5151 was a ~70% Mustang and came in at 500+ pounds. Not that you couldn't do better, but cutting the weight in half would be a real challenge, to say the least. Ultralights are just that - ultralight. There isn't enough room in the 254 pound limit to allow for anything but a bare bones flying machine.
     
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  5. May 1, 2019 #5

    pictsidhe

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    I'm working on the design for a 2/3 scale Hawker Hurricane Mk103. It is challenging. I am bucking convention not to mention common sense and attempting to do it in monocoque Coroplast.
    I would highly recommend that that to save yourself a lot stupendous amount of work, you pick a more conventional 103 type structure, and make it P-51 shaped. I looked into ply, composites etc etc and all the conventional 'hard skin' methods just don't work for one reason or another at 103 wing loadings. Mostly too fragile when made light enough. For a cantilever wing, you are going to be swearing at the thin P-51 airfoil. I found an aerodynamic excuse to thicken my root from a true scale 19% to 21%. I could do it at 19. but 21 saves a few more vital lbs.

    You will need to do some structural engineering. You might want to follow my demented ramblings here and steal seek inspiration from my research.

    I'd really like SOMEONE to build a nasty axis aircraft, so I could dogfight it! Once I get this thing done, I may do a Zero, but do not hold your breath!
     
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  6. May 1, 2019 #6

    Doggzilla

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    There is actually a very light P-51 that uses a rotax. Maybe not ultralight, but definitely LSA.

    So it can be done.
     
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  7. May 1, 2019 #7

    BBerson

    BBerson

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    Increased chord is a good idea. Need a bigger tail with that.
    Less wing taper would be safer, to prevent the legendary tip stall. So add more chord at tip.
    A light cantilever ultralight is rare and difficult. Good luck.
     
    Last edited: May 1, 2019
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  8. May 1, 2019 #8

    J.L. Frusha

    J.L. Frusha

    J.L. Frusha

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    Thinking of using a wingtip endplate with half-round on the outside to appear as the Cavalier tip tanks, or faux tip-tanks with tip turbines, to increase effective span and reduce vortices, which could solve several issues all at once. Matter of try 'em and see...
     
  9. May 1, 2019 #9

    J.L. Frusha

    J.L. Frusha

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    UltraCruiser
    Still the only all metal UL today!


    Airfoil GA30-618
    HP (Range) 28-45
    Wing Span 7.62 m 22.5 ft
    Wing Area 10.4 m2 101 ft2
    Wing Loading 22.65 kg/m2 5.4 lbs/ft2
    Length 4.87 m 16 ft
    Empty Weight 114-123 kg 252-270 lbs
    Gross Weight 227 kg 575 lbs
    VNE Speed 152 km/h 95 mph
    Cruise 97-137 km/h 60-85 mph
    Stall 46-52 km/h 28-32 mph
    Take Off Distance 46 m 150 ft
    Take Off Over 50ā€² Obstacle 92 m 300 ft
    Rate Of Climb 152-305 m/min 500-1000 ft/min
    Landing Distance 92 m 300 ft
    Fuel Capacity 18.9-30 L 5-8 Gal
    Fuel Consumption 5.6-7.6 L/Hr 1.5-2.0 Gal/Hr
    ā€œGā€ Rating 4 4
     
  10. May 1, 2019 #10

    henryk

    henryk

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  11. May 1, 2019 #11

    J.L. Frusha

    J.L. Frusha

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    FK-51 is 401 not found.

    Going into their website...

    Their SW-51 'Ultralight' seats 2 and has an MTO weight of 600 kg.

    Nice find, but it's a carbon fiber aerobatic LSA.


    Of course, I cound shorten it considerably ahead and aft of the cockpit sort of 'cartoon scale' carricature style, maybe take another 1/3 off the length. Then reduce the span ?

    Maybe call it the P-51 Shetland Pony...? :p

    [​IMG]
     
  12. May 1, 2019 #12

    BoKu

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    If you want to simultaneously develop an airframe and a powerplant, well, knock yourself out. However, be aware that if you do that the odds are stacked pretty steeply against you ever flying it. Each alone is something like a 5,000 work hour proposition, and doing both together makes it very likely that by the time you're done they're obsolete. So my advice would be to concentrate on one or the other.

    And, yeah, an ultralight WWII fighter replica of any scale would be a real challenge. My guess is that you could do it, but you'd have to get exotic. We're talking carbon fiber semi-monocoque with pultruded reinforcements and skins so thin they'd buckle if you looked at them wrong. The gear legs would probably have to be titanium, with molded carbon wheels.
     
  13. May 1, 2019 #13

    Norm Langlois

    Norm Langlois

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    This is more of a question . Such a design would not qualify as an UL more for its flight character . A war planes airfoil would not have the proper minimum air speed and stall to meet the 103.
    If you would need to opt for a thicker wider root, whats the point of all that fuselage for appearance. Most UL's can not even enclose the cockpit because that would exceed the weight limit.
    If one could be built It is going to be as BoKu says fragile.

    Not knowing what the many attempts to build light weight 26 ft plus wing span,weighed. I have a new mono spar design I may build this year.With a 5 ft root and 4 ft tip but thinner wing a DAE31 .Yes my wings can be cantilevered with a 3G maybe 4G .
    Each half span would weigh 38 lbs without covering. I still cannot see my way to a replica design and qualify as an UL, without using the 103-7 seaplane, additional weight exemptions.
    I used an all aluminum air frame for my first plane stripped to the bone it was to heavy for wheels.
    The electric option,is it going to be less than 80 lbs with batteries?
    After all is said and done An ultra light must meet stall and max speed requirements.
    The Ultracruiser could be still a questionable claim to ultralight.
     
    Last edited: May 2, 2019
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  14. May 1, 2019 #14

    PiperCruisin

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    Having helped a guy design a legal ultralight, it is hard. This configuration would be very difficult. With basic med available, why all the effort to create a marginal airplane?
     
  15. May 2, 2019 #15

    litemite

    litemite

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    While I do agree with all posts before, woe unto me to stifle innovation or a new way to answer a problem. Migh I suggest you check out on You Tube and search for a young man named Peter Sripol. He did an ultralight powered by two RC model electric motors. If you dig deep enough on his channel you will find about a ten installment video series showing how he did it. He did have the plane at Air Venture last year.
     
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  16. May 2, 2019 #16

    pictsidhe

    pictsidhe

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    For me, training costs is a large part of wanting to start with 103s.

    I also want to design my own plane. Yeah, yeah, I'm weird!
     
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  17. May 2, 2019 #17

    pictsidhe

    pictsidhe

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    Peter Sripol posts here sometimes as FoamandTape. Sadly, I think some of us (me and others) get annoying by telling him to do some structural calcs on anything carrying him...
     
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  18. May 2, 2019 #18

    bifft

    bifft

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    I keep sketching out a 75% Ki-84 (my shoulders don't fit in a 70% one). Don't think I'm up for the challenge of getting it down to 103 weights.
     
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  19. May 2, 2019 #19

    pictsidhe

    pictsidhe

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    My shoulders don't really fit in a 2/3 hurricane, but a little massaging of proportions will be done.
     
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  20. May 2, 2019 #20

    J.L. Frusha

    J.L. Frusha

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    Not looking for a big battery. Gasoline, or jet fuel diesel Genny with electric motor that is already in use. Only battery is for starting.
     

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