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  • October 20, 2018, 12:14:15 PM

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Author Topic: A poser for math guys  (Read 548 times)

Offline peabody

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A poser for math guys
« on: October 08, 2018, 07:31:27 AM »
Thanks
Bill is currently "grounded" because his back MD says he shouldn't lift more that 20 pounds. What does a full size Randy plane pull?

Online Tim Wescott

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Re: A poser for math guys
« Reply #1 on: October 08, 2018, 08:53:09 AM »
A stunt plane turning 5 1/4-ish second laps on 70-foot lines pulls 3g.  So if you're not an engineer or a pendant, multiply the airplane's weight by 3. 

If you ARE an engineer or a pendant, then multiply the airplane's mass in kg by 29.6m/s2 (to get an answer in Newtons), or it's mass in slugs by 187ft/s2 (to get an answer in pound-force).  Be sure to work out the dimensional analysis to make sure it's right.  But then, if you can do that, you don't need me to run the numbers.

12lb for a 4lb plane.  Less than 20 pounds, but with all the twisting and turning, and the possibility needing to do fancy footwork if it goes slack on the lines, I'd suggest judging for a few weeks while doing the back exercises recommended by his doc (they really help me, when I hurt my back).
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The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Online Tim Wescott

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Re: A poser for math guys
« Reply #2 on: October 08, 2018, 08:54:18 AM »
And if he DOES insist on flying, suggest that he dry-flies some wingovers and overhead 8's.  Having your back bind up so bad that you fall down is bad; doing it when you're stunting is way worse.
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The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Online john e. holliday

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Re: A poser for math guys
« Reply #3 on: October 08, 2018, 10:37:24 AM »
Start out with the plane he wants to fly if he really wants to do it with a needle setting that will get the plane air borne for the first tanks of fuel.  In fact put only enough fuel in to get him air borne.   Forget the safety thong and have some one in the circle to take the handle if he says it is too much.   I know I going to get slapped for this but I don't use a safety thong with new students until they have flown a plane with out help.   Really tell him not to push it as it take longer to get the back working.   Don't ask me how I know. D>K
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Online Brett Buck

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Re: A poser for math guys
« Reply #4 on: October 08, 2018, 10:56:20 AM »
It's about 10 lbs or for a full-size stunt plane. But I would note that lifting 10 lbs and pulling 10 lbs sideways while spinning around and leaning backwards are entirely different things - maybe better, maybe worse, depends on the problem.  '

    I would think this would be very ill-advised when you are supposed to be taking it easy.

    Brett

Offline Ken Culbertson

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Re: A poser for math guys
« Reply #5 on: October 08, 2018, 08:42:16 PM »
You can do a RWO without bending your back too much but you might consider skipping the OH8 unless you are going to compete.  I had a bad back when I was in my 40's and the worst part was getting up from a kneeling position so if you can get past starting the engine you may be OK.  On the bright side, nothing makes you focus on your posture like a bad back.

Good Luck - Ken
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Online Motorman

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Re: A poser for math guys
« Reply #6 on: October 08, 2018, 09:44:33 PM »
Must want to fly pretty bad.
There will be a sunny day and we will fly our airplanes.

Online Tim Wescott

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Re: A poser for math guys
« Reply #7 on: October 09, 2018, 08:24:03 AM »
Must want to fly pretty bad.

I can sympathize with that!  I've flown against the advice of my bones & tendons.  Sometimes I've come out hurting and still been glad I flew!
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The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.


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