Elapid
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- May 2, 2009
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first i'd like to invite any additions of successes and failures when using flashpan ignition for clusters.
I love clusters.
it is awesome when all the motors are spewing hot flaming fire and choking clouds of smoke!
after my return to rocketry, advanced topics became quite interesting to me; clusters, staged flights, odd designs, and scale models became a big focus. I built my TriAgain as a sub-minimum diameter, 3-E motor clustered rocket. Even with only 3 motors, it wasn't uncommon for one to fail to ignite.
I did a little research and came across a technique called flashpan ignition. I went to the local gun shop and picked up a small can of 4F gunpowder and decided on a slightly different version of the method for several reasons.
My method is quite simple and almost foolproof.
almost.
I load the rocket with motors normally, then i take the lid off the 4F and pour some into the cap, then i pour it from the cap into the motor nozzles, filling them and mounding it above the edge of the motor casing. once each of the nozzles is full, i take a piece of 2" wide masking tape and tape it across the bp/motors and fold it around the bottom of the airframe to secure it. another layer of 4F may be added after the motors are taped, and another layer of masking tape over that. now make a small slit in the tape, or poke a hole with the launch rod if you forgot to bring something with you and insert an estes igniter, or igniter of your choice. load the rocket normally, and you're set!
i love the way it goes *poof* pause *whoosh*!
I've had 3 failures using flashpan.
1. MMT was constructed in a shoddy manner, with gaps at the forward end of the MMT tubes and the aft end left unsealed (the gaps between the MMT tubes). the force of the flash ejected one or two of the motors, which were also ignited from the proper end. this could have been dangerous with larger (than C6) motors.
2. similar to the first failure, a 3-motor cluster was launched with flash ignition, it had flown many times before, but i think i used standard electrical means. there was a gap in the center of the 3-motor cluster which was not plugged. on ignition, the force of the blast blew the nosecone and recovery system out the front, all 3 motors ignited and the rocket did cartwheels just above the launch rod due to lack of nose(weight).
3. one cluster (4 x A3PT & 3 x A3-4T) failed to ignite even though all the 4F burned. i used *extra* and it went fine the next time around.
My biggest cluster? i did a 14-motor cluster of A3-4T motors in a Mosquito upscale with a 2.6" airframe. it was an awesome boost, all the motors lit, but the chute got wedged on deployment and the rocket came down hard (but flat) on the range.
so... it seems most of the failure modes involve not properly sealing the MMT area and making certain that the force of the flash is not transmitted into the airframe.
i like my method because when using an aluminum pan the wind could move it around maybe even spilling the powder...the tape also protects the rocket from getting scorched so badly.
i did just think of another protective measure make a ring of aluminum foil that slides over the aft end of the rocket, like a pie plate with a hole in the center... it would sit up against the fins to protect them from the blast and just fall away on launch.
flashpan ignition is hard on rockets.
I love clusters.
it is awesome when all the motors are spewing hot flaming fire and choking clouds of smoke!
after my return to rocketry, advanced topics became quite interesting to me; clusters, staged flights, odd designs, and scale models became a big focus. I built my TriAgain as a sub-minimum diameter, 3-E motor clustered rocket. Even with only 3 motors, it wasn't uncommon for one to fail to ignite.
I did a little research and came across a technique called flashpan ignition. I went to the local gun shop and picked up a small can of 4F gunpowder and decided on a slightly different version of the method for several reasons.
My method is quite simple and almost foolproof.
almost.
I load the rocket with motors normally, then i take the lid off the 4F and pour some into the cap, then i pour it from the cap into the motor nozzles, filling them and mounding it above the edge of the motor casing. once each of the nozzles is full, i take a piece of 2" wide masking tape and tape it across the bp/motors and fold it around the bottom of the airframe to secure it. another layer of 4F may be added after the motors are taped, and another layer of masking tape over that. now make a small slit in the tape, or poke a hole with the launch rod if you forgot to bring something with you and insert an estes igniter, or igniter of your choice. load the rocket normally, and you're set!
i love the way it goes *poof* pause *whoosh*!
I've had 3 failures using flashpan.
1. MMT was constructed in a shoddy manner, with gaps at the forward end of the MMT tubes and the aft end left unsealed (the gaps between the MMT tubes). the force of the flash ejected one or two of the motors, which were also ignited from the proper end. this could have been dangerous with larger (than C6) motors.
2. similar to the first failure, a 3-motor cluster was launched with flash ignition, it had flown many times before, but i think i used standard electrical means. there was a gap in the center of the 3-motor cluster which was not plugged. on ignition, the force of the blast blew the nosecone and recovery system out the front, all 3 motors ignited and the rocket did cartwheels just above the launch rod due to lack of nose(weight).
3. one cluster (4 x A3PT & 3 x A3-4T) failed to ignite even though all the 4F burned. i used *extra* and it went fine the next time around.
My biggest cluster? i did a 14-motor cluster of A3-4T motors in a Mosquito upscale with a 2.6" airframe. it was an awesome boost, all the motors lit, but the chute got wedged on deployment and the rocket came down hard (but flat) on the range.
so... it seems most of the failure modes involve not properly sealing the MMT area and making certain that the force of the flash is not transmitted into the airframe.
i like my method because when using an aluminum pan the wind could move it around maybe even spilling the powder...the tape also protects the rocket from getting scorched so badly.
i did just think of another protective measure make a ring of aluminum foil that slides over the aft end of the rocket, like a pie plate with a hole in the center... it would sit up against the fins to protect them from the blast and just fall away on launch.
flashpan ignition is hard on rockets.
