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- Thread starter tktmsa
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I do it in AutoCAD. But that's what I have to work with. Easy peasy.

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Rex

I have heard of OpenRocket's scale feature, but I've never remembered to use it.

If you generate your nosecone, any body tube/couplers will be scaled to its diameter. Same for tubes after a transition. When you choose your motor mount size, centering rings will automatically conform to the space between airframe and motor tube. That just leaves the fins.

Scale Factor is needed to determine material and part size differences. It's no more then a simple math problem.

If you have a model based on say BT-20 (.736"OD) and you want to Up-scale it to BT-60 (1.637" OD) divide the Up-scale diameter by the base model diameter to get the Scale Factor in this case 1.637 - .736 = 2.224 scale factor. You can now Up-Scale all the remaining dimensions of the model (except Angles which remain the same) to build you larger creation. example: Base model Fin Root edge @ 1.5" x 2.224 = Upscale fin Root @ 3.336"

To Down-Scale the same BT-20 (.736") model to say T3 (.375") body, you'll use the same process to find the scale factor .736 - .375 = 1.963 Scale factor. but you'll reverse the process to find the multiplier .375 div by .736 = .5095108. Base model fin root 1.5" x .5095108 = .7643" Down-Scale Fin Root.

Computers are great but we should also know how to work the problems manually. Helps to keep the grey matter a little sharper

If you have a model based on say BT-20 (.736"OD) and you want to Up-scale it to BT-60 (1.637" OD) divide the Up-scale diameter by the base model diameter to get the Scale Factor in this case 1.637 - .736 = 2.224 scale factor. You can now Up-Scale all the remaining dimensions of the model (except Angles which remain the same) to build you larger creation. example: Base model Fin Root edge @ 1.5" x 2.224 = Upscale fin Root @ 3.336"

To Down-Scale the same BT-20 (.736") model to say T3 (.375") body, you'll use the same process to find the scale factor .736 - .375 = 1.963 Scale factor. but you'll reverse the process to find the multiplier .375 div by .736 = .5095108. Base model fin root 1.5" x .5095108 = .7643" Down-Scale Fin Root.

Computers are great but we should also know how to work the problems manually. Helps to keep the grey matter a little sharper

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https://modelrocketbuilding.blogspot.com/2014/10/estes-teros-upscale-part-7-fin-cutting.html

https://modelrocketbuilding.blogspot.com/search/label/E Teros

It turns out the Teros fins were pretty big on the original BT-50 model. When they are upscaled

they look even larger.

Here's the upscale I did:

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