geof
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L2 Success!
Wasn't perfect (a small chute entanglement) but good enough.
My 16yo daughter came to the launch with me and ran through the (lengthy) checklist I had prepared. She caught several small glitches, made me stick to my list religiously, and saved my butt several times. I started to put the ebay tube in backwards (though the sled was right)...she caught it before I did (although I would have, too). But during the recovery from that mistake, I forgot to fully secure the aft ebay bulkhead. That would have been a fatal mistake if not for her. We got to the pad and heard only 2 beeps, which meant one failed continuity (drogue). We took it back from the pad and she spotted the loose wire...despite being screwed down tightly, it had been pulled out during fussing with the rest of the ebay.
Two years ago, my last L2 attempt was with a rocket I aptly named "Cratermaker". I suspect that I may not have shaken the black powder into the delay element gap sufficiently, or maybe there was a bit of lubricant there, because the motor never ejected the chute and the rocket lawn darted. The rocket name was fitting because the top 2.5 feet of the rocket was buried and we had to get shovels to dig it out. Since that rocket was not fully successful, my daughter decided to name my new rocket "Green Feather That Lands Softly".
Fixing all issues, we got 3 beeps, a laser-straight launch (J350), and perfect drogue deployment. The altimeter charge and the motor charge both fired within about 0.5 seconds of each other. I had set the main for 1000ft and the rocket kept falling and falling. I knew this was probably the most likely possible failure point, so I was really nervous as the rocket seemed to plunge way too low. Surely it was just nerves, however, and the main chute ejected nicely when it was supposed to. Then there was this slight tangle. A club member had it in binoculars and he reassured me several times: "Don't worry, it looks good, just wait, it's going to go", and by plain eye it also looked fine--but slow. However it never quite fully deployed, but the grassland was soft after recent snow and the landing was harmless. The only damage was a couple paint chips presumably from pieces striking each other during descent. When I recovered the rocket, I looked at the chute. You've seen how big the chute is. There was about a 3" loop of cord tangled around one corner of the chute. If I showed it to you, you would think "no way that could possibly stay tangled".
I certainly would have loved a flawless recovery, but bottom line is that this was good enough. The altitude was a modest 1721 feet, allowing us to see all the action up close. The openrocket simulation projected 2566, a pretty astounding difference. The OR model was perfect in terms of shape and mass, except for a few ounces discrepancy in the main chute mass. I attribute the altitude difference to the chute weight difference and to a poor OR estimate of drag due to the split fins. Plus it seems like OR projections are always too high, period.
I think my daughter deserves a "junior L2" for all her help
After my launch, she had a "first", too: her first built RMS motor, an F24-7. She put it in her childhood "Bumblebee" rocket. Unfortunately, the delay was too long (we had switched from an E28-4 at the last moment and I forgot to have her shorten the delay of the new motor), and the rocket was destroyed. Her next project is the Mega Mosquito.
I love building much more than flying (and would rather dedicate my $ to kits/parts instead of propellant), but I do plan to fly my rocket again soon on a big J motor.
My next projects are a scratch 6" stubby rocket with aft chute deployment (so the rocket lands on its nose to protect the big fragile swept fins), and a Madcow Tomach which will be my first experience with HP minimum diameter (54mm). The only problem is that if I use an I motor or bigger with the Tomach, I'll probably lose the rocket. So I'm also making a 54/38 converter. I would love to find tracking gear for $100-200, but it seems like the cost for new gear would be very expensive. So I'll probably stick with small motors for the Tomach.
That's all for now.
PS. I'm not sure if I showed my pvc motor retainer (with tin ring) above, but it worked absolutely fine, even on this J motor. I've never had a failure/melting and the whole contraption costs $5.
Wasn't perfect (a small chute entanglement) but good enough.
My 16yo daughter came to the launch with me and ran through the (lengthy) checklist I had prepared. She caught several small glitches, made me stick to my list religiously, and saved my butt several times. I started to put the ebay tube in backwards (though the sled was right)...she caught it before I did (although I would have, too). But during the recovery from that mistake, I forgot to fully secure the aft ebay bulkhead. That would have been a fatal mistake if not for her. We got to the pad and heard only 2 beeps, which meant one failed continuity (drogue). We took it back from the pad and she spotted the loose wire...despite being screwed down tightly, it had been pulled out during fussing with the rest of the ebay.
Two years ago, my last L2 attempt was with a rocket I aptly named "Cratermaker". I suspect that I may not have shaken the black powder into the delay element gap sufficiently, or maybe there was a bit of lubricant there, because the motor never ejected the chute and the rocket lawn darted. The rocket name was fitting because the top 2.5 feet of the rocket was buried and we had to get shovels to dig it out. Since that rocket was not fully successful, my daughter decided to name my new rocket "Green Feather That Lands Softly".
Fixing all issues, we got 3 beeps, a laser-straight launch (J350), and perfect drogue deployment. The altimeter charge and the motor charge both fired within about 0.5 seconds of each other. I had set the main for 1000ft and the rocket kept falling and falling. I knew this was probably the most likely possible failure point, so I was really nervous as the rocket seemed to plunge way too low. Surely it was just nerves, however, and the main chute ejected nicely when it was supposed to. Then there was this slight tangle. A club member had it in binoculars and he reassured me several times: "Don't worry, it looks good, just wait, it's going to go", and by plain eye it also looked fine--but slow. However it never quite fully deployed, but the grassland was soft after recent snow and the landing was harmless. The only damage was a couple paint chips presumably from pieces striking each other during descent. When I recovered the rocket, I looked at the chute. You've seen how big the chute is. There was about a 3" loop of cord tangled around one corner of the chute. If I showed it to you, you would think "no way that could possibly stay tangled".
I certainly would have loved a flawless recovery, but bottom line is that this was good enough. The altitude was a modest 1721 feet, allowing us to see all the action up close. The openrocket simulation projected 2566, a pretty astounding difference. The OR model was perfect in terms of shape and mass, except for a few ounces discrepancy in the main chute mass. I attribute the altitude difference to the chute weight difference and to a poor OR estimate of drag due to the split fins. Plus it seems like OR projections are always too high, period.
I think my daughter deserves a "junior L2" for all her help
After my launch, she had a "first", too: her first built RMS motor, an F24-7. She put it in her childhood "Bumblebee" rocket. Unfortunately, the delay was too long (we had switched from an E28-4 at the last moment and I forgot to have her shorten the delay of the new motor), and the rocket was destroyed. Her next project is the Mega Mosquito.I love building much more than flying (and would rather dedicate my $ to kits/parts instead of propellant), but I do plan to fly my rocket again soon on a big J motor.
My next projects are a scratch 6" stubby rocket with aft chute deployment (so the rocket lands on its nose to protect the big fragile swept fins), and a Madcow Tomach which will be my first experience with HP minimum diameter (54mm). The only problem is that if I use an I motor or bigger with the Tomach, I'll probably lose the rocket. So I'm also making a 54/38 converter. I would love to find tracking gear for $100-200, but it seems like the cost for new gear would be very expensive. So I'll probably stick with small motors for the Tomach.
That's all for now.
PS. I'm not sure if I showed my pvc motor retainer (with tin ring) above, but it worked absolutely fine, even on this J motor. I've never had a failure/melting and the whole contraption costs $5.
