Ejection vent hole size?

[SolarYellow]

Is there a rule of thumb (or better) for sizing ejection charge vent holes? I've seen it suggested by TVM that a vent area equal to the cross section of the charge well in the motor should be adequate. Any other practices or theories people follow? Adjustments if using multiple smaller holes?

For protecting the inside of the chamber to be vented, I've seen a replaceable chunk of coupler, a coil of aluminum soda can, foil tape, and high-temp paint. Maybe nowadays high-temp polymer tape such as Kapton. Any other recommendations?

 

[Titan II]

Are you talking about this?

https://www.apogeerockets.com/education/downloads/Newsletter68.pdf

 

[mh9162013]

I speak from LPR applications, but yes, I have also heard that the vent area should be at least as large as the cross section of the charge well. But I imagine that a greater area shouldn't hurt (within reason).

As for protecting the interior, I've found that white glue works just fine to protect cardboard. After a few ejections, I've found that the risk from burning is minimal as the soot builds up and protects the cardboard.

 

[SolarYellow]

Are you talking about this?

https://www.apogeerockets.com/education/downloads/Newsletter68.pdf

No, this.

https://www.apogeerockets.com/education/downloads/Newsletter520.pdf