Scale ME-262

Discussion in 'Warbirds / Warbird Replicas' started by Saville, Oct 5, 2019.

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  1. Oct 5, 2019 #1

    Saville

    Saville

    Saville

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    So the latest issue of Kit Planes had a Paul Dye article on his SubSonex. Interesting article. He makes it pretty clear that building and owning a SubSonex is pretty much of a vanity thing - it's not a good XC machine, for instance.

    But that got me to thinking:

    These little jet engines are coming down in price and increasing in performance and reliability.

    Is a scale ME-262 with two of the SubSonex engines (PBS TJ-100 turbojet) at all feasible?

    Can you arrive at a scale and weight where:

    1) A sea level standard sized pilot can fit comfortably and

    2) Can you increase the fuel capacity to make it a good XC machine

    3) Can you make it a 6+/4- G aerobatic airplane without increasing weight
    and what are the engine inlet issues with regard to aerobatics?



    The very first crude calculation is thrust to weight:

    Stock ME-262

    thrust * 2 = 1,848
    gross weight = 14,271

    Thrust to weight = 0.26 - 0.28

    Thrust taken from 109-004B
    Production-series engines with reduced weight and strategic
    materials.


    SubSonex:

    Thrust * 1 = 258.53 lb
    gross weight = 1000lbs

    Thrust to weight = 0.25852


    Scale-262:

    Thrust * 2 = 517.06
    gross weight = 2000 lbs

    Thrust to weight = 0.25853 (Obviously the same as the SubSonex since I doubled
    both Values)

    Similar thrust to weight. I wonder if one could get the weight down substantially? I think 2000 lbs is a conservative overestimate but I don't know that for sure. Certainly composites would
    help with that.
     
  2. Oct 5, 2019 #2

    pictsidhe

    pictsidhe

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    The 262 has the pilot fairly near the cg. What a scale one would need is something heavy in the nose to balance the tail. The genuine 262 had some pretty fearsome weaponry up there. If you can work out how to get the cg in the right spot, it is quite a feasible project, though not simple. The 262 flew excellently when the engines weren't eating themselves. There have been full size 262s made with modern engines.
    What scale are considering?
     
  3. Oct 5, 2019 #3

    Saville

    Saville

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    To be honest I hadn't gotten that far on scale because the weight used in my weight for T/W was a WAG.

    Original length is 34 feet 9 inches
    span is 41 ft 4 in
    wing area 234 sq ft.

    now my RV-8 has a span of 24 feet and a length of 21 feet. It's a two seater. So I'm thinking the Scale-262 size might be in the RV-8 ballpark but a single seater. So that is roughly 2/3's scale. The 262 was a big airplane but I don't know it's width at the pilot seat so I don't know if a 2/3's scale will allow a human to fit. As I say these are just some starting thoughts.

    Also the CG of the engines, pilot and gas could be fairly close together - they seem to be on the original, if you look at the side view.

    As for nose weight I recoil at the prospect of useless lead. Though it certainly can be a baggage compartment; will hold the nosewheel gear; and could also have another gas tank up there. Though the CG shift as you use the gas would have to be carefully worked out. Once could mount all avionics boxes up front - nice easy access through the gun servicing doors. Somehow it works out on light twins though the weight of the engines on light twins may be more forward than on a scale 262.

    SubSonex Wing area is 60 sq ft
    Me-262 wing area is 234 sq ft
    RV-8 wing area is 116 sq ft

    So comparative wing loadings:

    ME-262 = 61 lbs/sq ft
    SubSonex = 16.67 lbs/sq ft
    RV-8 = 15.5 lbs/sq ft

    As I say I've just started thinking about this, this morning so I won't be able to answer a lot of questions with calculation results.
     
  4. Oct 5, 2019 #4

    plncraze

    plncraze

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    For the new full size 262 replicas newer lighter engines were installed in a case weighted to bring the cg into the right place.
     
  5. Oct 5, 2019 #5

    Saville

    Saville

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    It would seem to me that to look right the Scale 262 engines are too short. So I wondered what the performance hit would be to install them in a nacelle that was longer then the engines.
     
  6. Oct 5, 2019 #6

    Speedboat100

    Speedboat100

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    You could make afterburners to it.
     
  7. Oct 5, 2019 #7

    pictsidhe

    pictsidhe

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    Scale nacelles and put a long jet pipe on the engines. You'll lose a bit of thrust, but it moves some badly needed weight forward. Without knowing specific details about the engines, hard to guess at the loss. A straight extension pipe with the nozzle at the end would be the lowest loss and fairly simple to make.
     
  8. Oct 5, 2019 #8

    Speedboat100

    Speedboat100

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    8% thick wing and afterburners and you are supersonic...well not without some serious re-engineering.
     
  9. Oct 5, 2019 #9

    pictsidhe

    pictsidhe

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    If you are serious about this, you need a set of A.L. Bentley drawings. He has Me262 sets. I am using a set to design my Hurricane. I can confirm that they also look great on the wall! At 1:24 real scale, they are 1:16 at my 2/3 scale. More detailed drawings are useless unless you are building a full size replica. With a scale and much lighter aircraft, you will need to drastically alter the structure, so you can look forward to engineering the stresses yourself.
     
  10. Oct 5, 2019 #10

    Saville

    Saville

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    ;)

    Actually one could also place the battery/batteries up front. Decent chunk of weight there. Plus the heavy cabling that then runs back.

    Not sure how useful the drawings would be as, at first glance, I don't see any dimensions. I'd have to make hand measurements, convert to full size then back down to 2/3's. Seems ripe for human error (knowing me).

    As for stress engineering I figured I'd have to do it anyways as the weights of the components (e.g. engines) are vastly different, plus, as I mentioned in the OP I would give some thoughts (much further down the road) to composites. There are a lot of curves on this thing. Bending sheet aluminum to obtain them for a one-off plane seems overwhelming.
     
  11. Oct 5, 2019 #11

    Speedboat100

    Speedboat100

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    You could easily scale that to ½ size.


    https://www.albentley-drawings.com/...t-me262a-series/messerschmitt-me262a-series/#

    Possibly even 38% sized.

    https://en.wikipedia.org/wiki/Messerschmitt_Me_262

    50% scale would look absolutely scale...from distance.
     

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  12. Oct 5, 2019 #12

    mm4440

    mm4440

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    Scaled warbirds are difficult projects, jets more so. the engines you propose are over $60k each and burn about 40 gal/ hr each for TO thrust. There is a higher thrust version that you would probably want for more performance and higher cost. How much time and money do you have. Buy an L-29, full size.

    1968 AERO L-29
    Turbine Military Aircraft
    L-29 Recon model. Low Total Time Hangared 343 Gallons G Limits +8 / -4 Experimental / R&D Category Selling for Major University in Ohio Call Brad Willette at Lane Aviation Corporation in Columbus, Ohio. U.S.A. for more information: 614-237-3747, ext. 159 ...
    For Sale Price: USD $39,000

    Lane Aviation
    Columbus, Ohio
    Seller Information
    VISIT OUR WEBSITE
    Phone: (614) 681-7931
    [​IMG]

    Add To Watchlist View My Watchlist
     
  13. Oct 5, 2019 #13

    Saville

    Saville

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    Nobody at the outset promised, least of all me, that these thoughts would lead to a flying article. But I'm intrigued by the possibilities, and maybe others are too. Success and progress always begins with an idea.

    An idea may not lead to anything practical; but instant rejection of an idea always leads to failure of one sort or another.

    Also note that I paraphrased Paul Dye's opinion that the SubSonex - and probably my idea - is a vanity plane with little practicality to the average pilot/owner. But who knows? Plus I never said this was a marketing idea which would make me zillions.

    Instant negativity always causes me to instantly dismiss the negativist.

    Instantly.

    What's it to you how I or others, spend my time and/or money?

    To squash an idea at the outset is really quite destructive to progress. At the very least I, and possibly others, may learn something. Something about design....something about structures...something about jets.

    But I suppose there are always people like that. I've certainly run into them often in my life.

    I learned to laugh at them and then ignore them.
     
    Aerowerx likes this.
  14. Oct 5, 2019 #14

    Speedboat100

    Speedboat100

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    I only counted 20 gallon / hr: http://modelaircraftcompany.com/newshop/en/home/89-jetcat-p400-pro-turbine.html

    -----

    This would yield authentic thrust: http://modelaircraftcompany.com/newshop/en/home/90-jetcat-p550-pro-turbine.html
     
    Last edited: Oct 5, 2019
  15. Oct 5, 2019 #15

    Steve C

    Steve C

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    I got to see the one Sanders worked on shortly after it arrived at their shop. One of the plans was to move the engines forward so they could remove some of the balast in the nose.

    I'm sure you'd face a similar cg issue on a scale model. You might be able to move things around a bit without making it look obvious. Cockpit forward a couple inches, wing back a couple... Then carbon fiber on everything in back.
     
  16. Oct 5, 2019 #16

    Speedboat100

    Speedboat100

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    Everything has to be calculated.
    [​IMG]
     
  17. Oct 5, 2019 #17

    Saville

    Saville

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    If the pilot truly is right at the CG then a lot of the wing is aft of the CG. And some of the engine is forward of the CG. But I don't yet have the info necessary to check that.
     
  18. Oct 5, 2019 #18

    Saville

    Saville

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    Yes. Everything.

    I would like to avoid a cartoon canopy if possible.
     
  19. Oct 5, 2019 #19

    Speedboat100

    Speedboat100

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    ½ scale would not give much forward down visibility..3 degs max.
     
  20. Oct 5, 2019 #20

    ScaleBirdsScott

    ScaleBirdsScott

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    The only options when scaling down much beyond 80% in most planes is exaggerate cockpit and canopy, or deal with very minimalist "space helmet" sort of canopy experience, complete which is a good case for using in-ear headset and a low profile flight helmet if any.
     

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