Thanks, Mike — it is a smaller diameter – 2.5″,, and not a lot of volume either if, as planned, I use a 6XL motor, so I'm a little concerned about residual hot gasses expanding up into that space. I do have two 1/4″ vent holes. Just wondering if that's enough.
I'm just finishing up a scratch-build, 38 mm, dual-deploy (my first DD). Not an elegant design, but it's nearly finished so I don't want to get into any massive re-designs or modifications. Problem is that the forward end of the fin can section is closed (except for a couple of vent holes), since the AVbay is located centrally and blows aft for the drogue and forward for the main. I have, up until now, exclusively used CTI for my HP projects. There are only a couple of CTI 38mm loads that come plugged. What is the safest method for removing the motor ejection provided in most CTI 38 mm loads? Open the top end and empty the black power charge and then leave the delay grain in place? Should I put something (inert) in place of the black powder and re-seal? Or is there a plug of some kind that I can use in place of the delay grain/motor ejection charge?
Like Mike, I have only removed the cardboard plug and emptied the powder. I haven't had any issue with pressure. My outboard airstart motors have only a few cubic inches of airspace in front of them (sealed, no venting) and only retained by a single #8 screw each. Never had any movement of the motors. With the vent holes, you'll be fine.