Okay Open Rocket Ninjas...

Why can't I attach these fins to the inner tube?

View attachment 25 v2.ork

The centering rings are in the way. Add fin tabs to fit between the centering rings.


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I tried that. It didn't work.

They are currently set as part of the body tube, do you mean it wont let you move them down to the inner tube? I'm not sure if OR lets you put fins on inner tubes so you may have to make it a smaller diameter body tube, with a coupler if it needs to extend inside another tube?

You cannot attach fins to inner tubes. Period.

You can attach them to body tubes only. So, your options are to attach them to the outer body tube and use fin tabs to extend "down" to the inner tube, OR you can use a body tube that is the diameter of the inner tube and attached at the end of the exposed outer body tube. What I'd do if it were me, would be to use the inner tube for only the length of the portion that is inside the larger body tube, and then use a body tube that is the same diameter and length of the exposed section to attach the fins.

Guaranteed you will get body tube diameter error messages.

K'Tesh said:

What I'd do if it were me, would be to use the inner tube for only the length of the portion that is inside the larger body tube, and then use a body tube that is the same diameter and length of the exposed section to attach the fins.

Guaranteed you will get body tube diameter error messages.

Click to expand...

Yep.

Try a massless transition with 0-length. That should nix the body discontinuity error, and I'm interested in what itll do to the CP.

Here, I worked up a fix for you. A couple things to note: centering rings should be attached to the body tube and not the inner tube. Then you can take advantage of automatic sizing. The other thing is that in this file, in order to attach fins the way you want, as others have mentioned, the aft tube has been split into a 5" 'inner tube' and a 12" 'body tube' to make up the total 17" tube.

A "length-less" transition will make the CP go bonkers. I added one to the second file with a length of 0.1mm to avoid all that. CP for both files is within ~5mm of the original file.


View attachment 25 v2-1.ork

View attachment 25 v2-1b.ork
(with discontinuity fix)