Ahhhhhh, I'd recommend something other than a GD 38 for an L2 attempt unless one is very willing to work in a confined space, may have to use a magnetic switch, or acquire an EggTimer Quantum deployment device, have to deal with minimum diameter
motor retention and figure out a nose mounted tracker. The room is very tight. My Tele-GPS fits in the NC but it's a tight fit. I threaded the hole in the coupler but may have to do PEM nuts in the near future. Some cram in an EggFinder but crunching up the antenna is going to effect the range unless the antenna is facing aft.
Yeah, one could say I don't care about the base drag and use an Aeropack retainer and not worry about having to use threaded rod/bulkhead for internal retention. That would be fine and help keep the ceiling down.
I did a 4" LOC tubed, plastic NC, motor deploy that probably got close to 2500' and worked with the stock J350M motor right off the bat. I don't recommend the GD 38 for L2 unless one has done a lot with MD H and I rockets.
If one wants to pick one up on sale and squirrel away for later build that's smart.
You have to find the rocket to get a successful certification. I agree with Tom that T2T is not needed for J's. Just use 40 grit to rough up the surfaces and use generous pro4500 epoxy and fillets. If going to 38mm K's well, then go to T2T with something. Also don't use my sled suggestion seen early in this thread. Use Jim Hendricksen's suggestion for the sled and not mine:
https://www.rocketryforum.com/showt...-community-build-thread&p=1462327#post1462327 His is way.....much......better than mine. I wanted to see if I could pull it off with one piece of all-thread but it effectively cuts down on the useful space. Don't do it! The hardware isn't available anymore anyways.
I think 9000' on a J350 is way too high an estimate for a rocket that has all the hardware needed for a flight with a tracker. It's still going high but the weight will hold it down.
I second the motion: Use a six grain motor, no tracker = no rocket recovery, lost rocket, Did Not Finish and failed L2 attempt.
I did a cardboard LOC tubed MD 38mm rocket with T2T on the 4 fins with a large payload bay for the EggTimer TRS. Used an Archetype cutter on the main so it was single deploy at apogee with the main held by the cutter.
The Mayhem railguide bound on the rail and was destroyed by the rocket. Rocket went 950mph and 8767 feet on a J500. The railguide was destroyed with just a few paint chips on two fins. It probably would have
done 500 feet higher. The rocket is lighter than the GD38 but has 4 fins that have larger surface area. If it weren't for the TRS GPS, rocket would have been lost. Completely sight unseen, landed 1.66 miles away and the GPStracker got me to it with no muss or fuss.
Unless one has some tracking experience under their belt, I strongly recommend against doing this kind of flying for an L2 attempt. If they've been flying ultra light L1 rockets to similar altitudes using tracking successfully well,
they're already used to working in tight spaces and by all means go for it. If been flying L1 rockets previously without tracking and expect to learn the art on their first L2 attempt with a screamer of a rocket, you'll need
guardian angels to control your flight attempt. Chances of a successful outcome are very low.
My attitude is keep it simple and once certified gradually advance yourself. I learn something new every time I GPS track as I'm always trying to tweak something to make things work better. Kurt
I flew this to 8500' with a ~1.2 mi recovery distance and a great lock on the EF until it was just about on the ground, navigated right to it. This sled has a bracket between the battery and bulkhead that could hold a magnetic switch, but haven't decided whether I'm going to take advantage of that or not, this bay is easy to access before & after flight since there's a single set screw to lock the nose onto the bulkhead.
