[RocketsNW] Mixed Black Powder and AP Cluster

[Marty2]

Tim,

Sounds like an interesting project.  I would include some form of electronics in case you don't light the central AP motor (and also make sure you light all 4 C6s and they have enough to get it off the pad).  I like the PerfectFlite electronics for a combination of ease of use and cost - the MAWD is a great dual deployment rig and the MT3G is a very good launch activated timer.  You might also think of installing a larger central motor if there is room since that opens up 29 and even 32 mm motors (the G12 is 32 mm and designed for radio controlled gliders, but is even better than the F12 or E6).  This will even give you room for a custom igniter that may increase the probability of lighting the central AP motor before it leaves the pad.

Marty

PS Relying on the ignition of even a central D12 or E9 BP motor as part of a 5 motor cluster as the only deployment mode is foolish in my opinion.  I fly 7 motor BP clusters where 3 of the motors can deploy the chute (all 7 is too much) and normally have a timer back up for the apogee on dual deployment flights.

-----Original Message-----
From: rockets-bounces at rocketsnw.com [mailto:rockets-bounces at rocketsnw.com] On Behalf Of t.j.doll at att.net
Sent: Monday, May 04, 2009 7:33 PM
To: Rocket Lost
Subject: [RocketsNW] Mixed Black Powder and AP Cluster

Hi All

I'm starting work on a new project - an Estes 1/100 Saturn V powered by a five engine cluster.  As currently envisioned, it will retain the center 24mm engine, with four 18mm engines around the outside.  I'm thinking it would be pretty cool to put four C6 motors around the outside to get it going with a center AP motor - perhaps a long burner such as an F12 or  maybe a real long burning Apogee E6 in the middle mount (I'm thinking a seven second burn on a Saturn V would be pretty cool <g>).  However, I worry about getting an AP center motor ignited - as currently envisioned only the center engine would pop the chutes (the outboard motors would vent the ejection overboard), so if the AP doesn't ignite it'll be a lawn dart.  I suppose I could change the design so that the outboard ejection charges could also blow the chute, but that be messy (and limit my engine choices).  I suppose I could use an on-board electronic ejection (set up to trigger at liftoff), but I'd rather not, and it still wouldn't help if the igniter failed to light the motor.  I've had real good luck using Quickburst "Twiggy" igniters in my AP motors, but it'll be hard to find a Twiggy that will fit in a 24mm motor nozzle and Copperheads have always been crap shoot.

So, what does every one think?  Am I tempting fate to mix AP and black powered, with the AP motor being critical?  Any other suggestions?

Thanks

Tim