Ballast and a Minimum Diameter Rocket

This should be an easy peasy rocket to certify with. Thought one couldn't use a fin can for cert but looks like that is only for L3.

I just had the first flight on my Transonic II today on a I245G in the MDR configuration with a Eggtimer Mini up in the nose. It was perfect to something like 1850ft. Mine came in pretty heavy at 6lb 5oz loaded and going back to my open rock sim and updating my final weights and I was within something like 25ft of predicted. My J500 and J350 numbers are 4500ft and 4400ft respectively. This isn't THAT high for a L2 flight with decent trackers.

Even though this is sort of minimum diameter, with the fin can and motor retainer and the fin geometry it isn't super high performance. If you want a low and slow bird build a low and slow bird though.

Jarrett,

This may be "confirmation bias" at work--but my experience mirrors your own. I roll chutes really tight with the JLCR ready to pop open. A quick ground test tells me if I'm on the right track--then I roll the real one even tighter--usually just a few minutes before flight. It works great.

If you contrast that technology with dual-deploy, it seems like an easy decision to me. I purchased a Stratologger CF, and want to begin experimenting with DD--so I watch the Apogee Rockets video on YouTube, "Dual Deploy for High Power Rockets." Have you really watched this video?

[video=youtube;KFbQ17y98hU]https://www.youtube.com/watch?v=KFbQ17y98hU[/video]

I mean, come on. Really? You're going to tell me that this system is more reliable than the Jolly Logic Chute Release? No way--even two experienced flyers struggle to describe the process without contradicting each other.

I wrap my chute right, put the JLCR right in the middle, then wrap the whole in the nomex burrito. So far, no muss-no fuss. Super reliable.

Plan to learn and fly DD for the experience, but I'm sure the vast majority of my flights will be on JLCR.

grouch said:

Did you have your chute wrapped up in the nomex with the JLCR holding the nomex closed?

Click to expand...

Yes. Good point. What is the recommended way to do it? If the JLCR rubber band were only holding the chute and not also around the Nomex chute protector, then that would give the chute protector a lot longer to unwrap, instead of just the last 500 ft.

I am not sure there is a recommended way. When these things came out it seemed to be “what is working for you guys” kind of thing. I put the chute release inside the nomex and fold the ends of the blanket towards the center then roll the nomex up, very similar to an actual burrito. My thinking is that the shock cord helps pull the blanket open. My guess is the blanket opens up fairly quickly after it is ejected from the body tube. Then the chute and release just flop around in the airstream waiting on the desired altitude. I normally go for 700’ just because I like to see the rocket under chute a little bit. I can honestly say that of the chute deployments I have been in range to see, they all opened with a vengeance.

If my Yorkie allows me tomorrow, I’ll try to take a pic of what I do. I’m not proclaiming to be a JLCR savant, it’s just what works for me.


Sent from my iPhone using Rocketry Forum

lowga said:

Jarrett,

I mean, come on. Really? You're going to tell me that this system is more reliable than the Jolly Logic Chute Release? No way--even two experienced flyers struggle to describe the process without contradicting each other.

Click to expand...

Dual-Deploy is like computers , garbage in....garbage out.
Success depends upon skill level....no matter how you do it.

Obviously you have more skill with Jolly L..I would take a gamble & bet someday you will find both methods are equally reliable & find both have their place.

I would also be willing to bet, the majority of all failures are due to user error, not the electronics. :wink:

lowga said:

so I watch the Apogee Rockets video on YouTube, "Dual Deploy for High Power Rockets." Have you really watched this video?

Click to expand...

Yeah, it is pretty bad. I am surprised Tim published it. I like how the 2nd guy doesn't know if he should stay in the scene or step aside at the end!

Yes, the JLCR is reliable at what it does, and if you have a good chute wrapping method, then you will be successful with it. The JLCR performs just one function, and as others have said, you may outgrow its capability and need a multi-function DD setup someday. As L2, you are bound to come across a scenario where motor ejection is too short, and thus you need another means of apogee deployment.

You mentioned carrying an A3 in the rocket. How is that mounted?

The video was very informative, especially for a newcomer like myself. I wasn't trying to be critical--only to point out that dual-deploy is complex, and not always reliable either. As Jim pointed out, either JLCR or DD can be foiled by human error. Reading through back issues of Extreme Rocketry, High Power Rocketry, etc. it's clear that dual-deploy went through a lot of growing pains, as technology and techniques improved.

Some people seem to expect or even demand that JLCR be foolproof from the start--with no such learning curve. That's unrealistic. Even with this rocket, I'm seeing that the longest delay possible with motor ejection is barely enough. Some motors simply cannot be flown it in without DD because I would need a longer delay. So I want and need to learn DD--but I don't see the logic behind using it in a certification flight when a technique that I already have experience with will work.

The JL Altimeter 3 is mounted on a fiberglass sled inside the nose cone payload bay, along with the tracker.

Really am grateful for the advice. Asking questions, and hearing from more experienced people is how I learn best.