I am in need of some Open Rocket help,..

This is about 98% complete. I am having 2 issues and appreciate your time helping me out with them,...

1. Rear end has a transition that goes from 5.5" to 4.5" and I need the fins to follow that linear decline. Not a show stopper,... as I can live w/ it.

2. No matter what setting I try w/ my drogue, the flight simulation seems determined to give me a very high velocity apogee deployment speed.

Thanks again.


View attachment Test_Vehicle_close.ork

it is not the apogee(drogue) event that is prompting the warning, its the main chute deploy that is causing concern.
Rex

Unfortunately, OR doesn't support the fins following a transition.

You can sort of cheat it by splitting your transition in half, and putting in a very tiny tube sliver with no thickness at the split to which you anchor your fin. It's only good enough for an approximation though.

kj

Thanks to both of you for your help. I now have a better understanding. It seems that I was not increasing the drogue diameter large enough to see a change. I also had the mind set of single deploy, where my ejection timing directly affected the apogee deployment speed. I was expecting that by setting the drogue to deploy at apogee I would see <=30 ft/sec there. Thanks again.

Hi Parry,

I'd like to let you know a little secret... You CAN get OR to follow the curve of the boat tail... Kinda.

In my Velociraptor downscale, I discovered that if the fins are attached to a body tube that is smaller than the diameter of the rocket (say the same diameter of the motor tube), you can "position" then relative to the top of the tube (or bottom) and you have automatic (full length) fin tabs. the complexity of the fins' shape wrapping around boat tales requires a little more brute force method, but I think I got it to look good.






The body tube I use lately is the outer diameter of the motor tube, and is .000001" long, and 0.0" thick. I often label mine as "Phantom Body Tube for ..." where the "..." is why I'm putting it in (e.g.: Engine Hooks, Fins, or other details). You see, OR doesn't take physics completely seriously. In OR, two objects can exist in the same space at the same time. I use this to create fin "decals", or add "tape" to hold parts together (my CinerocDV sim for example).

You'll get some odd error messages ("discontinuity in body diameter") but I ignore them. If the rocket was stable enough for someone to sell it, then what's to worry about getting its physical shape correct for the sim.

Oh, and you might wan to check out my OR files.

All The Best!
Jim (aka K'Tesh)

Morning...

I checked this thread again, and spotted that you included the .ork file... View attachment Test_Vehicle_close (MOD).ork

So I tweeked the fins (better check my numbers) to put them on the same level as the rear of the boat tail... Oh, and please do something about those colors. The Black Brandt II deserves something better than pastel yellow and green :wink:

Thanks Jim. Phantom body tubes do this very nicely. Something I would not have thought of myself. Lol on colors, as my son and I were goofing around. I am still undecided on a final pattern. I seem to favor flat black colored nose cones and fins. Thanks for your help.