Re: Aircraft Scaling Problem / Question


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On Jan 29, 8:22?pm, "David T. Ashley" <d...@xxxxxxxx> wrote:
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On Jan 29, 7:38 pm, "David T. Ashley" <d...@xxxxxxxx> wrote:
I was sitting in a little airport the other day holding a die-cast
model
of
an airplane with about a 10-inch wingspan. The model was quite heavy
(maybe
a pound).

At the same time, I was looking outside at a little Cessna with about a
35-foot wingspan, and I know it weighs about 1,500 lbs. empty.

Then I thought ... if the little model was built comparatively the same
as
the actual airplane, what would it weigh? (And out came the pad of
paper.)

I figured that the ratio of wingspans was about 40, so I did the math
as:

(1/40)(1/40)(1/40)(1,500 lbs.) = 0.3 ounces.

Did I do the math right? Are little airplanes so light that one with a
10-inch wingspan should weigh less than half an ounce?

Am I missing something?

How much do you think the Cessna would weigh if it were die-cast?

That is interesting, but not my original question. I'm just curious if I'm
thinking in the wrong way, i.e. if my method of scaling down was valid.

I've been flying in the little things for a while. Fortunately, I
completed
my flight training before I got a look inside a wing (not a lot there),
otherwise I wouldn't have had the courage to fly more.

I just can't believe they are so light that a comparable model with a
10-inch wingspan would weigh less than half an ounce. Seems
counterintuitive.

My question first, then yours ... : )

But you're also assuming that EVERYTHING is reduced by
a scale of 40. That's not likely if you tried making a model.
You have to sacrifice true scale where it can be hidden, such
as the thickness of the materials otherwise your half ounce
model would be more ephemeral than tissue paper.

He's only asking about it in theory. These sorts of theoretical analysis are
done all the time to get a good idea about the inner workings. Essentially
he's asking math problem and not an engineering one.


.

Relevant Pages

  • Re: Aircraft Scaling Problem / Question
    ... an airplane with about a 10-inch wingspan. ... 35-foot wingspan, and I know it weighs about 1,500 lbs. empty. ... 10-inch wingspan should weigh less than half an ounce? ... 10-inch wingspan would weigh less than half an ounce. ...
    (sci.math)
  • Re: Aircraft Scaling Problem / Question
    ... an airplane with about a 10-inch wingspan. ... 35-foot wingspan, and I know it weighs about 1,500 lbs. empty. ... 10-inch wingspan should weigh less than half an ounce? ... You have to sacrifice true scale where it can be hidden, ...
    (sci.math)
  • Re: Aircraft Scaling Problem / Question
    ... an airplane with about a 10-inch wingspan. ... 35-foot wingspan, and I know it weighs about 1,500 lbs. empty. ... 10-inch wingspan should weigh less than half an ounce? ... but not my original question. ...
    (sci.math)
  • Re: Aircraft Scaling Problem / Question
    ... an airplane with about a 10-inch wingspan. ... 35-foot wingspan, and I know it weighs about 1,500 lbs. empty. ... 10-inch wingspan should weigh less than half an ounce? ... half an ounce seems a reasonable approximation for something with a 10 ...
    (sci.math)
  • Re: Aircraft Scaling Problem / Question
    ... an airplane with about a 10-inch wingspan. ... 35-foot wingspan, and I know it weighs about 1,500 lbs. empty. ... 10-inch wingspan should weigh less than half an ounce? ... Or at least when I was a kid :-)? ...
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