Need a Rocksim Check On A F21 24mm

[JasonF]

I'm building a scratch 29mm with 24mm engine mount, to learn a few things but need a check. I don't know if you will be able to open my demo rocksim file, but here it is. It crashes when I try and reopen it in the demo version. What I need is the predicted flight values on the F21 econojet with the different delays. I need max velocity, altitude, optimal delay, and velocity at deployment. I'm trying to pick which engines to try it first on, and am looking for the lowest deployment speeds.

Parts list follows

PML Body Tube PT1.1 36"
PML Nose Cone 1.145 Urethane
Fins Simple Elliptical with TTL Birch 2.5mm plywood
root cord 65mm
tip cord 33mm
sweep length 24mm
semi span 65mm
sweep angle 20 deg
tab 4mm
MMT LOC 0.95 136mm
Thrust Ring 8mm
2 Apogee center rings 24-29mm
Parachute PAR-18 PML 18"
Shock cord 100# tubular Kevlar 5' x2 (braided together)
LOC .25" LL 2x2"

Just thought I would add what I've come up with.
Best choice RMS E18-7 altitude 1674 deployment speed 33.68
Best choice SU E15-7 altitude 1624 deployment speed 31.47
E50-10 altitude 1802 deployment speed 33.19
F32-10 altitude 3377 deployment speed 25.03

 

[cls]

Jason, something's very wrong with the rocksim file you posted. my v7 rocksim won't open it and looking at the raw file it looks messed up. anyways how did you get the demo version to save it? I thought the demo wouldn't save anything.

by the way I think your rocket will go almost outta-sight with the F21.

 

[JasonF]

Originally posted by cls
Jason, something's very wrong with the rocksim file you posted. my v7 rocksim won't open it and looking at the raw file it looks messed up. anyways how did you get the demo version to save it? I thought the demo wouldn't save anything.

by the way I think your rocket will go almost outta-sight with the F21.

If you try and close the program, it asks if you want to save it. Thats the only way I've ever gotten it to save anything. One of these days I'll spring for the full version. I'll agree, the thing will go out of sight on a F21, but they're cheap.

 

[teflonrocketry1]

Jason,

See attached; I tried to reconstruct your file in RockSim version 5. There were several issues I am not clear on: How many fins and are they eliptical since you gave all the measurements for a simple Trapezoidal design. where are the particular components such as centering rings and launch lugs located? Finally, what engine overhang did you use under what flight conditons? If you supply these details I will construct an even better file for you to use with the demo version of RockSim.

Bruce S. Levison, NAR #69055

 

[JasonF]

Don't worry about it. I'll probably never launch it on that big of an engine anyway. I'm taking pictures of the construction, but they are 35mm since I am digitaless at the moment. I suspect the 8 second delay would be closest, but would be a little short. An F21 would send this thing to 3000'. I hadn't quite intended that it be a disposable rocket . On the fins, it's three and simple trapezoidal. I just used the dimensions rocsim suggested and drew a template out with a protractor and ruler. Centering rings were at the ends of the motor mount. Launch lugs were just above the fins, and at the CG.

 

[teflonrocketry1]

I guess I was pretty close after all! Attached is a screen capture showing the design and flight simulation results with the four different motors. You want and 8 second delay for the E's and a 10 second delay for the F's.

Please post the pictures when you can. This design should give a nice flight on the motors you have selected.

Bruce S. Levison, NAR #69055

 

[JasonF]

Looks good, although I had the parachute forward. I'm still debating my shock cord attachment options. Using the Kevlar, but that small diameter tube makes attachment interesting.