Mrkoldkuts
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- Joined
- Jul 22, 2017
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Has anyone build the Jart and are you happy with it ? Thanks !
I have the original 5 inch jart, 4 inch hole, 2 grain 98"s I use an ultrafast propellant, after all, what could go wrong there?
With scale recovery? [emoji3]WTH? Those aren't Jarts! These are Jarts. https://www.ebluejay.com/item/6731904
Show me a 54 mm version of one of these babies and I'll be impressed.
WTH? Those aren't Jarts! These are Jarts. https://www.ebluejay.com/item/6731904
Show me a 54 mm version of one of these babies and I'll be impressed.
With scale recovery? [emoji3]
I built a 5" Jart in the spring of 2014. Modified it with a donut avbay so it could fly on 4 grain 75mm motors...
...
In four years it made 17 flights. Now I'm cannibalizing it's avionics for other rockets and have removed the recovery parts. I kinda researched rebuilding the fincan into something that would hold my 76/10,000 research motor, which is 56" long, but that won't happen any time soon, and I would definitely use a more robust fin that didn't stick down like the Jart fins did.
I built a 5" Jart in the spring of 2014. Modified it with a donut avbay so it could fly on 4 grain 75mm motors.
You must have had a rough landing that Par 96 should have got the job done.
The avbay sled slid in next to the MM extension in the coupler, and added a 16" payload tube.
The N/C was modified with a removable coupler that allowed me to add an Eggfinder with no metal parts near it.
The first couple of flights were on 54mm motors, but it was apparent that my guess of a Cd at .7 was a bit high. First flight on a 75mm L995 to 10,123 ft. made me adjust the Cd down to .4. Another thing that became apparent was that all those modifications made it way too heavy for the fins, with a fillet cracking on the first flight and cracked fins on flights 5, 6 and 7. So I did a tip to tip fiberglass layup and added more weight, making it a real beast at over 18 lbs. Had several good flights after that, then on flight #9 I broke the drogue shock cord and had the fincan land under a 15" drogue in soft dirt with no damage.
Flight #10 was on an L1115 to 11,457 ft. and #11 was on an M1101 to 12,709 ft.
In the fall of 2017, we started casting 75mm research motors, so "Jughead" was fed a steady diet of 4 grain 75's, which usually flew to 11,500 ft. On flight #15 it cracked another fin, despite the 96" Top Flight chute I was using at the time. Flight #17 it suffered another drogue shock cord failure and cracked two fins and damaged the fincan body tube. No soft dirt landing on that flight.
In four years it made 17 flights. Now I'm cannibalizing it's avionics for other rockets and have removed the recovery parts. I kinda researched rebuilding the fincan into something that would hold my 76/10,000 research motor, which is 56" long, but that won't happen any time soon, and I would definitely use a more robust fin that didn't stick down like the Jart fins did.
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