4x Thing a Ma Jig Upscale?

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mcderek

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After taking a break from rocketry I'm looking at building a HP rocket out of material I already have. Checking the tube rack I have plenty of LOC 4" and 54mm motor mount. I have a nice 4" nosecone as well.

One of my favorite lp rockets is the Flis Kits Thing A Ma Jig https://www.fliskits.com/products/rocketkits/product_images/thingamajig.jpg
I think the interlocking fins are cool and it flies great. And I have the plywood on hand as well. Therefore, how about a 4x upscale? Length would be right around 8 feet or so with big fins (about 24"). Some type of fairing to fill in the fin/tube gaps would look cool as well.

A question: How would one model the canted fins on open rocket? Or approximate them?
 

ScrapDaddy

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My first idea would be to use the distance from where the fins intersect as the fin height and then to model the addition drag using a transition piece that shows the increased surface area from the interlocking fins. I'll whip up something real quick and update this post.View attachment thingamajig 4 in.ork

I don't think the offset position of the fins matters in regards to stability since they are still functionally 120 degrees apart and so the only other weird thing to account for would be the increased drag, which I believe you could do with a transition piece equal to the thickness of the interlocking fin jig (.5 inches?)
 

mcderek

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Thanks for the input and the file ScrapDaddy. I'll take a look at it when i get home.
 

rharshberger

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Dont know how your shop is set up Derek but if you need access to a bandsaw, scroll saw, belt sanders, etc let me know as I only live about 5 miles from you now in Pasco.
 

mcderek

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Thanks for the offer Rich! I don't think I need anything I don't have at the moment but if i do I'll let you know.
 
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