2009-02-23

Why my way of doing things is different ?

Someone from aviation business might find my almost primitive way of calculating drag and then finding how that drag is fought by the engine hp and prop size and pitch as absurd.

I find this very exhilarating and practical to be honest and very avantgarde too. Just the way a true artist would do it. You should try it sometimes.

Recently I calculated the minimum force to keep Max airborne at 80 km/h and the power minimum needed for take off at 89 km/h.

I assumed that the rolling force ( force needed to roll the wheels due fraction ) goes to zero at take of by the speed increase and lift..and no friction is thus counted in to equation. The air resistance or drag of the wheels at this speed is same as the drag of the airframe ( ie 50% )..flaps at 15 degrees increase the AC drag by 60-65% at this stage of the flight. Wheels of a regular Cri Cri create 25% drag and highly modified wheel collars on small wheels some 9% as in AR-5.



I have tried these low power take offs also with Lear Jet in FS simulator and technique I have developed is as follows:

You throttle that 33-35% power and let the plane accelerate almost to the end of the runway and there you deploy the 15 deg flaps just for a brief monent to get off the ground..and when higher speed is obtained after gear retraction you take the flaps in..pretty soon. ( I would not recomend that technique to be used by "Sully" in LaGuardia or any other pilot..it is just one of my energy saving "weapons", that might come handy in some emergency situation ( like when taking off with RATO in the Antarctica with a fully laden C-130 etc ). This is also very essential aspect in MAX III cause it has to take off with a prop that has a huge pitch and is quite ineffective at low speeds..therefore knowing that 6.5 hp with the right prop for take off is minimum. That leaves a window open for a take off with a prop that has only 30% efficiency at take off with maximum power ( I am going to calculate that next ).

Seems that 22 hp is a good engine choice..and take off with 35% power looks very feasable with a prop optimal for take off. Higher pithed prop ( that enables the 165 mph cruise ) indeed needs 92% power to be able to take off with 22 hp engine.

I am very open to suggestions for the right foil for MAX by experts ( Wortmann, NLF, NACA, SD ? )..it could be laminar, but not necessarily to avoid too narrow window of use.

I have kept my design simple and used all the experience ( knowledge ) of aerodynamics I know of and also all the design skills how to squeeze the functional aspects of the design into smallest yet most aerodynamical shape without compromising any of it.

I do read stuff like this to recheck and double check if I am on the right track, but haunch of the things is more important to me: http://www.adac.aero/

8 comments:

  1. It's much easier to just decide what you want the values to be. You can save the time consuming calculations.

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  2. Thanks for the very first comment on this site !

    I agree that the undecided foil causes trouble in doing calculations on much other basis than the drag related coefficients ( when estimated weight, power and wingarea are known ).

    I used "normal" C lift force numbers. I don't see any reason fool anyone here...everyone can see into what size I was able to squeeze a small pusher..advantages of this design start there !

    But like said earlier on TKK will do the calculations to tune and verify my data.

    rgds,

    Juke

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  3. This comment has been removed by the author.

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  4. I tried to say.

    I got e-mail from a TKK graduate ( Helsinki Technical University ) who wished me luck and said she does not want to be in any doings with a 2-stroke AC and gave me these to study ( they are free ):

    http://www.aoe.vt.edu/~mason/Mason_f/CAtxtChap1.pdf
    http://www.aoe.vt.edu/~mason/Mason_f/CAtxtChap2.pdf
    http://www.aoe.vt.edu/~mason/Mason_f/CAtxtChap3.pdf
    http://www.aoe.vt.edu/~mason/Mason_f/CAtxtChap4.pdf
    http://www.aoe.vt.edu/~mason/Mason_f/CAtxtChap5.pdf
    http://www.aoe.vt.edu/~mason/Mason_f/CAtxtChap6.pdf

    Apparently something very important and new stuff.

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  5. I also discussed with fellow who has in fact built and designed several AC:s of his own design and let an engineer do the calculations here in Finland ( liver near here ). I see this very smart way to go forward...just like Howard Hughes said to his engineer to do H-1 racer for him with specs he knew it was going to fullfil.

    What was the name of Hughes's aviation engineer by the name ?

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  6. I thinkit was Odekirk, but I see no comment of him here:

    http://en.wikipedia.org/wiki/Howard_Hughes

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  7. Here is footnote:

    Glenn Odekirk

    http://en.wikipedia.org/wiki/Glenn_Odekirk

    BTW: Architect with same last name was one of the pioneers of modern architecture in Europe.

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  8. No it was J.P.P.Oud

    http://www.greatbuildings.com/buildings/Weissenhof_Row_Houses.html

    Sorry !

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