Wednesday, June 17, 2015

Rebuilding the '4F Club' as the '3Fs and 2Ds'

If you read my last launch report, you will know that the 4F Club didn't work exactly as planned. The sims said it would be up to speed off one of MDRA's long rails, but in merely lobbed off the pad and augered in under power. The fins, nose cone, recovery stuff and two motors survived to fly again.

A quick review came up with several possible causes:

  1. You can't trust software. Possibly, but I've never seen a sim that far off.
  2. You can't trust RASP motor files. Also possible, but it seems OK based on my other F15-powered rockets and their associated sims.
  3. Poopy clay. You have to be on the rocketry forums to appreciate this term. The nozzle on the booster looked fine so scratch this one off.
  4. Cruddy rail. It was a bit rough, but it's hard to believe it was THAT bad.
  5. The rack bowed under thrust, causing the buttons of bind. And a cruddy rail might contribute to this one too. No real way to tell.
I have rebuilt the rocket with the following changes:
  1. I ditched the 4th F and the need for an uber long launch rail.
  2. In the interest of using a 4' 1/4" rod, I needed more thrust...thus the '2Ds' part of the name. I'm going to bond two D12's to the first booster.
  3. These boosters required that two of the rack supports be moved upward.
Here is the rocket with dry fit and used motors just to show what it will look like:


And, here is a close up of the butt end:


I really put some blood, sweat and tears into this rocket. Well, at least the blood part..


(I really need a better name for this one.)