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  #11  
Old 05-28-2019, 12:13 AM
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I expect he means Centuri ST-20 tubing (which is/was available from eRockets/Semroc). It’s 2.0 inches ID with a .021 wall thickness.
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  #12  
Old 05-28-2019, 08:42 AM
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Quote:
Originally Posted by teflonrocketry1
The pictures in your post are named Cubix. I have created simulations from pictures hundreds of times, one of the reasons my avatar is the #1 certified RockSim user. The drawing you posted doesn't seem to be accurate; what is meant by #20 tubing? I used BT-70 for the main body. I based the measurements I made on the fact the picture shows a C11-3 motor installed (with igniter!). What is the distance of the upper fins from one end of the body tube? If you remove the upper box fins, (should be an easy fix) you get a cool looking tractor design that will fly stable see attached files.


BEC is correct, it's a Centuri #20 from eRockets, 2.042" OD | 2.0" ID | 0.21" thickness. Motor tube is a #9 (basically a 24mm) 0.998" OD | 0.950" ID | 0.024" thickness. Centering ring: Semroc CR-9-20, nose cone: Semroc BC-2025. IIRC the front of the body tube was 2.5" from the leading edge of the upper "fins". The end of the tube was about 0.5" below the trailing edge and the motor protruded another 0.5" beyond that (the pic wasn't to scale, just my initial sketch, which is why I put dimension callouts to remind myself).

Quote:
Originally Posted by teflonrocketry1
A box kite does not fly with its box panels at the angle of attack you used in your design, it fly's with the wind hitting the panels close to a right angle and from their corners.


I just wanted it to look like a box kite and launch straight and safely. In reality it almost DID fly like a kite when it would get sideways, which was never the intention of course.

Can I get a copy of your Rocksim file? (Just started learning how to use OpenRocket and I believe it can read Rocksim files). It would really help me end up with a stable, flyable design.
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  #13  
Old 05-28-2019, 02:50 PM
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Quote:
Originally Posted by Rktman
BEC is correct, it's a Centuri #20 from eRockets, 2.042" OD | 2.0" ID | 0.21" thickness. Motor tube is a #9 (basically a 24mm) 0.998" OD | 0.950" ID | 0.024" thickness. Centering ring: Semroc CR-9-20, nose cone: Semroc BC-2025. IIRC the front of the body tube was 2.5" from the leading edge of the upper "fins". The end of the tube was about 0.5" below the trailing edge and the motor protruded another 0.5" beyond that (the pic wasn't to scale, just my initial sketch, which is why I put dimension callouts to remind myself).



I just wanted it to look like a box kite and launch straight and safely. In reality it almost DID fly like a kite when it would get sideways, which was never the intention of course.

Can I get a copy of your Rocksim file? (Just started learning how to use OpenRocket and I believe it can read Rocksim files). It would really help me end up with a stable, flyable design.


I have attached a RockSim file (Cubix-plans .rkt) based on the dimensions and other information you posted. Unfortunately this simulation uses pods which are not compatible with Open Rocket software. Open Rocket is currently unable to simulate this type of complex design. RockSim can handle the geometry but doesn't take into account the interference from the upper set of box fins on the lower set. Removing the upper set of box fins will give a stable design. I don't know if there is a trial version of RockSim available. I suggest you ask Apogee Rockets, they used to give a 30 day free trial. The software now costs $123.60.
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File Type: rkt Cubix-plans.rkt (89.0 KB, 10 views)
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  #14  
Old 05-28-2019, 05:29 PM
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Much thanks Bruce!
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