A high current output relay box with very low internal resistance is extremely helpful when launching clusters.
More info on mine here:
https://bpasa.com/Cluster-box.htm
So is using Rocketflite's igniters, because of high-quality, high-heat, and long leads - eliminating the need for whip clips.
Many of the smaller CTI motors actually come up to pressure before most BP motors do.
Most Estes motor thrust curves have an initial spike that peaks at 0.2 to 0.3 second after ignition.
As the motor starts its burn, it creates a growing cavity just above the nozzle.
The thrust peak corresponds to the maximum burning surface area.
When the cavity burns out to the motor walls, the motor then functions as an end-burner.
This later part of the burn is the lower thrusting tail of the burn.
With highly engineered AP motors like CTI's, the motor starts off with the optimum burn cavity and surface already present before ignition.
Then the BP plug most CTI motors use brings the motor up to pressure VERY quickly.
Both CTI's reported thrust curves and the very modest tests I have done (counting video frames during motor ignitions) show that many (24mm-38mm) CTI motors have a thrust spike at 0.1 seconds or less.
To fire clusters very reliably:
> Firing all igniters within 0.1 seconds assures motor ignitions before the rocket has a chance to start moving up the rod/rail.
(see Thunderbird first pic above)
> Motors coming up to pressure - or better yet hitting peak thrust - in the 0.1 to 0.3 second window assures that all motors are pushing hard before the rocket leaves the rod/rail.
(see Thunderbird second pic above)
My experience with AT is mostly RMS 29mm F and G engines.
What I do with these in clusters to help accelerate ignition is:
> Put a dab (about twice as much as a typical igniter) of Rocketflite ML pyrogen inside the top of the
propellant grain
> If White Lightning propellant - sand inside of propellant grain