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Building Tips and technical articles. => Building techniques => Topic started by: Motorman on October 14, 2015, 09:07:02 PM
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I've got full sized plans for a plane with 660 sq. in. wing. I want to scale down the whole plane so the wing area is 550 sq. in. What's the best way to go about this?
I guess one way is to take the plans to a printer and have them make a reduced copy but how do you figure how much to tell them to reduce it? Big sheets cost money, might take a few trys.
Another way is to figure a percent to reduce each dimension as you measure it off the big plans, allot of work.
What do you do when you want to make a different size of an existing plane?
Thanks,
MM
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sqrt(550/660) = sqrt(5/6) = 91%, give or take. You could round it off to an even 90% for 535 squares.
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Do you have the plans in question on paper, or in electronic format? If you have an electronic copy of them, I should be able to help you out.
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You could just tell them the wingspan you're looking for and they will do the math.
If the sheet comes out incorrect, they will do it again without charge. Till they get it correct.
All you need to bring is a tape to measure and the plans.
Good luck.
Charles
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Tim, thanks for the formula.
MM
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You could just tell them the wingspan you're looking for and they will do the math.
Charles
Not the best approach if one is trying to come up with a specific wing area. For those who understand the square root of the ratio of the two wing areas, the 91% solution by Tim Wescott above is the accurate way to go.
Just saying.
Keith
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23 sq.in. hidden by the fuselage so I want 573
Square root of (573 divided by 660) x 100 = 93%
I did some math and for a 573 sq.in. wing I came up with subtracting 6.75% from any linear measurement to make the smaller plane. So, now I can tell them to reduce the plans by 93% and quickly be able to check the wing span and chord ect.
old span 60" - 6.75% = new span 56"
Hey, just noticed 93 - 100 = 7 darn close to 6.75 hmmm...
MM
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sqrt(550/660) = sqrt(5/6) = 91%, give or take. You could round it off to an even 90% for 535 squares.
Someone just asked me how to do this in general, so here's the general formula to use if you know the old wing area and you have a new area that you want to achieve:
linear scaling ratio = sqrt(new area / old area), where "sqrt" is just short for "square root".
For another example, say you've got plans for a 500 square inch plane that you want to scale up to 700 squares. You get
linear scaling ratio = sqrt(700/500) = sqrt(1.4) = 1.18 = 118%
So if you're doing this on a copier (a honkin' big copier) just set the enlargement ratio to 118%. If you're generating your own build plans on paper, multiply the dimensions by 1.18.
You can work this backwards, too:
new area = (old area) * (linear scaling ratio)2
I might use this if I do the forward method and get an inconvenient number (like 118%) -- then I can pick something easier (like 120%) and do the backwards method to find out my new area. In this case it's
new area = (500) * (1.2)2 = (500) * (1.44) = 720
This may not sound too bad to me, and so I might run with it.
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I've got full sized plans for a plane with 660 sq. in. wing. I want to scale down the whole plane so the wing area is 550 sq. in. What's the best way to go about this?
I guess one way is to take the plans to a printer and have them make a reduced copy but how do you figure how much to tell them to reduce it? Big sheets cost money, might take a few trys.
Another way is to figure a percent to reduce each dimension as you measure it off the big plans, allot of work.
What do you do when you want to make a different size of an existing plane?
Tell Kinko's to run off a copy at the required percentage of the linear dimensions.
Brett
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I've taken plans to Kinkos for enlargement. First, I draw a scale on the plans, already reduced by the desired amount. I tell them to make the drawn scale equal 10" (or whatever you want).
That way, they only have to look at the scale for the correct plan size. Works for reduction or enlargement.
Floyd