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A Little Practice

posted Mar 9, 2016, 9:54 PM by James Cramton   [ updated Mar 9, 2016, 9:57 PM ]
John Grove's Initiator on a G64
Ken, John, and I headed out to the launch site this morning for some quiet flying without the din of a weekend club launch. The weather was great--blue skies, moderate temperatures, and almost no wind. John was interested in getting familiar with his new Jolly Logic Chute Release in his Initiator, and I was working on some NARAM58 models--getting my G Streamer Duration design into the air, and seeing if I can adapt an Apogee Stratus Gale (a B rocket glider model) for use in the D rocket glider event.  

John's Chute Release worked perfectly twice; Chute Release is a new Jolly Logic electronic altimeter gizmo that has quickly revolutionized recovery for any rocket with a parachute bay 38mm or larger.  It is an electronic tether that holds the parachute bundled up until a pre-set altitude.  So it is a way of reefing a parachute between Apogee and a lower altitude.  Although not technically "Dual Deploy," it is a great way to reduce how far your rocket drifts without resorting to pyrotechnic ejection charges--all the Chute Release does is release a cam at a preset altitude, and this releases a rubber band holding your parachute closed.  It's an ingeniously simple device to use that works very nicely.  And by the way--John Beans at Jolly Logic was generous enough to donate a Chute Release (and an Altimeter 3) to SARA's Desert Heat raffle this year.  So dig around between the couch cushions for loose change to get ready to buy your raffle tickets--$1 per ticket, or $5 for 6 tickets.  That's just two of the awesome donations up for grabs in the Desert Heat raffle!

G SD F59 Launch
My work preparing for NARAM 58 events has me strangely obsessed with the G Streamer Duration event. I should have learned from my E Egg Lofting experience at my first competition rocketry event, NARAM 57 in 2015, that the more challenging approach with a more preposterous solution is probably not the way to go. But I needed to chase that white whale, so I flew my prototype G Streamer Duration model on an F29 and again on an F59 to try to collect some descent rate data, and to determine if it is possible to reliably eject a 2 foot wide by 20 foot long 2 mil thick mylar streamer. Now, this is a large, heavy model; it's around 3 feet long, mostly BT 70 tubing and a 29mm motor. The streamer weighs 180 grams of the 370 gram weight of the model (without motor), and while this design is interesting, it is not likely to be a good performer in competition. Testing today showed mixed results; the first flight tangled the
Successful recovery of the Streamer Duration model, give or take a torn streamer
streamer around the rocket body a little past apogee, and while the resulting snarl of streamer recovered safely, the streamer was torn, and I collected no meaningful data on descent rate of the streamer/model combination.  I decided to tape the streamer together and try again, to see if the snarl was a fluke of poor shock cord packing (this is my conclusion), or if it is just nuts to try to fly such a large streamer. As it turns out, the second flight deployed the streamer successfully, and the although the top half of the streamer tore , it stayed together, and showed some of the twisting motion you look for in streamer duration flights.  but alas, with the mass of the model/streamer, and the torn streamer, the total flight to 1,100 feet and back was a short 47 seconds. I'll need to improve that if I'm to show well in competition.  My next step on this model is to go with a much lighter model, using the intact portions of this streamer as a starting point.

The final model to fly today was a test of a reinforced Apogee Stratus Gale--normally a B powered rocket glider--in an effort to determine if this is a reasonable approach to the NARAM 58 D Rocket Glider event.  The big question is whether or not the glider wing and other parts of the glider can withstand the speed generated by a D10 motor.  I've flown the model successfully on a B6-2 motor, but hearing tragic reports of similar attempts by other competitors, I reinforced the joints, hoping the bulky sliding wing design can withstand the aerodynamic strain of the speed a D10 motor can deliver.  Alas, as the video shows, it nearly succeeded.  As the velocity increased toward the end of the boost phase, the wing sheared off the model (26 seconds, in slow motion). While possible that I could reinforce the model better, or figure out a way to use a slower motor, I'm now looking to a swing wing design that will keep the wings out of harm's way until apogee. Also note the slow ignition is due to poor ignighter placement, but it worked well enough to gather the information I needed.

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