stunthanger.com
Design => Stunt design => Topic started by: James Mills on March 26, 2007, 09:26:47 PM
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What is the process for say taking a 600sq design around a 36/40/46 muffled and enlarging for a 40/60 piped setup. I spoke with Allen Brickhaus and he said he thought that there may be some formula for this (or is it simply a matter of enlarging the plans at Kinkos a certain percentage)?
Thanks,
James
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Or do it yourself with Tileprint! See my posts in this thread:
http://stunthanger.com/smf/index.php?topic=4483.0
Robert
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What is the process for say taking a 600sq design around a 36/40/46 muffled and enlarging for a 40/60 piped setup. I spoke with Allen Brickhaus and he said he thought that there may be some formula for this (or is it simply a matter of enlarging the plans at Kinkos a certain percentage)?
Thanks,
James
James,
Go to my website and I have a spreadsheet program that I published in Stunt News that'll do everything you need. It is located just under the picture on the main page. The instructions are a pdf file while the spreadsheet is for an Excel spreadsheet.
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Argh: Scaleimg ; wing area per displacement does the trick .
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While enlarging the whole plan will give you a decent starting point, everything does not need to go up *in scale*. The fuselage top view does not always need to be enlarged, etc.. But the areas, moments, and such should be good.
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James,
With the thoughts already up in this thread, you have a good start...
As for how much to scale up or down, try this:
You know the area of the model you want to scale...
You have a good idea of the area that suits the engine you will use, from checking successful designs for those engines...
Wing area is figured by multiplying span by average chord. Don't worry too much about that, all you want is the scaling factor. Think of it this way.
Call your inspiration model's area 100%. IOW, scaling factor is 1.
Its wing Area = (1 x Span) x (1 x av Chord)
For 40% more area, you need a new scaling factor - call it 'k'.
So, 1.4 x Area = (k x Span) x (k x Av Chord) which can be written as: 1.4 x Area = K^2 x (Span x av Chord) (k^2 means k squared.)
Original's Area still equals the original's Span x av Chord, so you can cancel those terms out, leaving: 1.4 = k^2. Find the square root of 1.4 (the value of k^2...)
k = 1.183.
Multiply the original's span and all other dimensions by that 1.183 and you've enlarged the entire design by 40%. This scaling factor example is pretty inconvenient, though.
There's usually a range of wing areas that do well with the engine you'll use, so you can round up or down and still be in the zone. For example, if you used k=1.1 instead, area scales up to 1.21 times the original. If you round up to k=1.2, the model scales up to 1.44 times the area (and all else) of the original.
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By the way, the approach in my Reply #5 also works another way...
If you have to limit the size of the re-scaled model, you can find 'k' directly from the change in span or length.
If you need to scale a 60" wing down to 45", k is 45 / 60 or 0.75.
Wing area changes by k^2.
0.75^2 = 0.5625. The new wing area is 0.5625 x the original area, that's 9/16, just over half of the original area.
And, if you want to enlarge a model to a certain span, say, k comes out larger than 1.
A 50" span, enlarged to 60", has a k = 60 / 50 = 1.2. The re-scaled wing will have 1.44 times the original's area.
Of course, you can't do this in OTS or Classic. They both require models that have the same dimensions as the originals. But, for fun, or for the Skill Classes, you're free to whup it around any way you want.