L1 cert attempt, part 2

[MattieShoes]

After my first (ballistic) attempt at L1, I scratch built a new rocket. She's about 2 pounds without the engine, 2.5 inches in diameter, and dual deploy capable, though I'm just using apogee deployment for my cert flight. I'm hoping to have the altimeter in there for the flight though.

Hoping to fly her this weekend on an H123. Fingers crossed!

[dixontj93060]

Nice! Wishing you the best on the L1!

[Handeman]

Good luck on the L1 attempt.

Cool paint BTW. Reminds me of that snake you found in the garage. Inspiration?

Any lessons learned on the 5.5" Thumper Jr? What happened on that one?

[rockie]

I like the paintjob, well done
Best of luck with the L1 !

[Pantherjon]

Cool paint job!

Good luck on the L1! I am sure you will get it! My first L1 attempt was a lawn dart as well!

[MattieShoes]

Good luck on the L1 attempt.

Cool paint BTW. Reminds me of that snake you found in the garage. Inspiration?

Not conscious inspiration anyway... Just sat down with some tape. :-)

Any lessons learned on the 5.5" Thumper Jr? What happened on that one?

Ejection charge failed to ignite and it came in ballistic. When I pulled the white cap off the ejection charge well, unburned black powder sprinkled out. Best guess is it was pointed down when the delay burned through and all the black powder had drained back into the well. Lesson learned is the well volume is much larger than the black powder volume, so fill the excess with wadding or something.



Also, I was a bit surprised at how much the Thumper Jr. weighed... Larger rockets means larger nosecones, thicker tubes,fins and centering rings, heavier duty shock cords, more glue, larger parachutes, etc. I think it was around 6 pounds. I went with a fairly narrow rocket this time to keep weight lower and costs down, so I can get better performance with cheaper motors. Though if I were to do it again, I think I'd go with the 3" tube rather than 2.5". 2.5" makes for a pretty crowded electronics bay. This one should go significantly higher on an H123 than the Thumper Jr. went on an I357. :-)

[DM1975]

Good luck on the cert flight. My first L2 attempt ended in a crash but luckily I had another rocket on hand to cert on. Hope all goes well for you.

[MattieShoes]

My dry weight was a bit low -- I added the parachute (duh), battery for the altimeter, a couple quicklinks... I didn't weigh it without the motor, but with the motor it's at 45 ounces. I'm guessing it'll go right around 2000 feet.

[MattieShoes]

Success :-)

The altimeter reported a peak altitude of 2339 feet, but I call BS. I downloaded the data and there's a pretty enormous spike in both directions at the moment of ejection... Is this normal? Is there a way to prevent it?

The real peak altitude was more like 2150 feet AGL, which is what Rocksim predicted after I corrected the weight.

Perfect recovery, about 17 fps on the descent.

[cjl]

Congratulations

Looks like a picture perfect flight. The H123 is one of my favorite H motors, and the one I got my L1 on.

As for the spike at ejection, it's caused by the ejection charge. It means that the e-bay isn't perfectly sealed from your chute bay. It's nothing to worry about, but it does mean that the reported altitude won't always be accurate without looking at the downloaded graph.

[RobD]

Congratulations.

[MattieShoes]

Hmm, I'll have to see if maybe I can find some thin rubber foam to line where the bottom bulkhead goes.

Incidentally, I launched Jack Skelerom for fun once the cert flight was out of the way. Another perfect flight :-)

[qquake2k]

Awesome! Congrats on the L1!

[cbrarick]

I have an ebay like that so I put some tape over the end, trim the edges with an exacto knife and double check to make sure it still comes apart without needing excessive force. Just gotta be careful about that, don't tape your altimeter so it sticks to fincan....

[brianc]

Let me add my congrats as well!

As for the spike at ejection, it's caused by the ejection charge. It means that the e-bay isn't perfectly sealed from your chute bay. It's nothing to worry about, but it does mean that the reported altitude won't always be accurate without looking at the downloaded graph.

I'm not so sure about the av-bay sealing being the cause. It looks like the
rocket was still heading up when the deployment occurred. As seen, that
can result in some violent G forces and baro spikes. The way to correct
this is to use the DD capabilities you built in, and not rely the motor ejection...

If you choose to use the motor delay, go with a slightly longer delay next
time. Did you drill it down for this flight?

[terryg]

Congratulations, great flight! This was a great day for flying, almost no wind and a large turn out for July launch in the desert.

[OverLord]

Congrats! Nice looking bird also!

Mike