Estes #1969 Saturn V: A cautionary tale

[ebruce1361]

I managed to sim it in Openrocket decently well, but the design didn't include the fairings around the fins which increased drag in the tail because I couldn't figure out how to get the shape right. On top of that, I would run a flight simulation on a set of motors and get 850ft or more for predicted altitude, and then run the same configuration again and get less than 200ft. Half the time I had the CG showing up right on top of the motors and it wouldn't move even if I added a pound of weight to the nose.

Ultimately, I did do the old reliable swing test and the rocket held up just fine. On top of that, it flew beautifully until the motor mixup caused the early deployment. So, even with it coming up to be heavier than my travel thermos full of six cups of coffee, (I know, a cup weighs about 8 ounces, but it definitely FEELS heavier) it was over stable and flew amazingly.

 

[DuaneW]

Maybe that's why I opted for the D12-0 design to begin with. I can't remember.

Robert DeHate at AMW had a run of D11-Ps awhile ago. You might check there.

 

[Blast it Tom!]

850 ft I could believe - straight up without drag I estimated 1950 ft - drag can really get you down! Does Open Rocket spit out the CdA or just the coefficent of drag? Even without fairings I'll bet it's pretty close.

 

[William Dieckmann]

Thanks for the "like" ebruce1361. I have to get on to stuff like that. Now on the cluster ignition thread, I just realized that my spiffy single neutral cluster setup is fine for 3 motors, but sure isn't possible here. Did you take any pictures of your ignition setup? After all, you lit all 5 and that really is saying something!

Off subject
Tom where in the burg

 

[Blast it Tom!]

Right across the river from Ambridge. You?

 

[William Dieckmann]

The only dumb question is the question not asked, I always say. As for sanctioned approval, I used this rig at the December launch for Tripoli Tampa, so I doubt it would be an issue anywhere else. It's just a five-way clip whip with switches.

The launch system for the club was built by someone else, so I can't say exactly how it works, but when continuity is present, an LED for that pad comes on in the box. If I were to build a similar setup, I'd just send one and a half volts through the line with an LED in series in continuity check mode, and then switch to the full 12 volts for ignition power. Anyway, I just flipped through each switch one by one and made sure I had my light each time, then I switched all five to "ARMED" and hoped for the best.

Hi
i built one where i use 12 volts for all
put a 1K resistor in series with LED for continuity test then by pass this for blast off . one battery for all
works great have launch key to kill all, arm switches which shows continuity, fire switch for launch

 

[William Dieckmann]

Right across the river from Ambridge. You?

Right across the river from Ambridge. You?

i live in bentwood i fly at trax farms on first Sunday of the month should be starting up in April or May LOW power
South Hills Area Rocketry Klub (SHARK) #809
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