Tube Fin Question

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PunkRocketScience

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I'm in the process of building a mid/high power tube finned superroc. Is there a recommended size for tube fins? That is, is there a length to diameter ratio that is more/less effective? The tubes I'm using are ~2" with the overall airframe length close to 10' and visually I have decided that 1' tubes look pleasing. I have yet to jam this into Rocksim to see if it will be stable or not.
 

lalligood

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teflonrocketry is "da man" when it comes to RockSim & he's written an article on how to simulate tube fins within RockSim. The short version is that if you took the tubes, cut them lengthwise & laid them out flat, that would be your fin surface area. Calculate your fin area like that & RockSim will give you an accurate representation of your design's stability.

As far as your original question, you left out diameter. It's easiest to use tube fins that are the same diameter as the airframe tube because 6 will match up nicely. You'll have gaps or require additional work/testing to see if larger/smaller tubes will work for you.

Tube fin rockets generally are very stable because they tend to be on the draggy side, which means they tend to fly straight & true. Check out my scratchbuild, Tube-a-licious over on EMRR for more information. Do a search for tube fin rockets on EMRR too. There are quite a few others.

HTH,
 

tnrocketman

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I did a nice custom tube fin rocket in Loc 2.1 inch tubing. I angled the rear of the tubes so the bottom is tapered, witg a launch lug running between two tubes.
I would have to go measure but I think there is about 3 straight inches before the angled part, but my BT was more like 36 inches total. I called it my Patriotic, since it has a white unfinished NC, red BT and blue tube fins.

I lost the rocksim file in a computer conversion. It was an old version anyway.

That rocket could fly in a hurricane-- it is the most stable rocket I have besides my overweight Ptero, Jr.. Loves G64s and the now defunct G35...;)
 

PunkRocketScience

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Sorry if I didn't make it clear in the first post. Both the airframe and tube fins are approx. 2" diameter. What my question was, is there an accepted "ideal" length to diameter ratio for tube fins?

Lalli- Thanks for the referal to the tube fin article. I'm looking for an extremely draggy rocket for a G spot landing event....low and slow....
 
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