Does a chute release require a vent? I know an AV bay does. Thinking about putting an altimeter in the AV bay as well. Had considered the Jolly Logic Altimeter 3 but that needs a vent in the booster tube where the chute goes as it connects to the parachute
I'd add two remarks to this. It's certainly true that the Chute Release doesn't care about vent holes, by the time it needs its altimeter you should already be descending, and had better be separated by that time or the CR won't help anyway. But there are still two reasons to consider venting, in my opinion:
1) Avoiding pressure separation. Depending on how tight of a fit your AVBay is to your airframe and the volume of the parachute section, you can end up with a significant pressure difference between the at-altitude air surrounding the rocket and the ground-level-pressure air "trapped" inside the rocket. So you could end up with an early separation caused by this pressure difference, which can be mitigated by venting the parachute section (to give the air another path out of the airframe), or shear-pinning the parts together, or perhaps something like friction-fitting (but you need to ensure things can still separate when the charge fires without just blowing your airframe apart). I typically vent airframes for this reason even when there is no altimeter/CR to worry about.
2) A much more minor concern but one that I think tripped me up once, if, once you arm the CR and seal-up the parachute section, you need to re-open the bay, it seems that you can generate enough of a pressure drop in the airframe to make the CR think it exceeded and then passed below its programmed altitude, causing it to release in the airframe. So if you don't re-check the CR before flying, you might find that it's already released and have your main deploy at apogee. So at least you're going to land under chute, but it might drift a lot farther than you intended. I had one time where my CR released early (well, twice, but the other time was clearly a band that broke during separation, this time the band was intact), and the only thing that was different about this flight vs. the many successful flights on the same rocket/CR was that the RSO asked me to demonstrate that the NC could separate as it was a very tight fit on the rocket (always has been). I do have a small vent hole in this airframe, but you can hear it "breathe" whenever I insert or remove the NC, and I suspect I still get a good pressure dip since it's hard enough to remove that once it breaks free it moves quickly.
It's also worth noting that the AltimeterThree doesn't
have to go in the booster tube, I fly it in my avionics bays whenever I can (whenever I have the space), to shield it from the ejection charges.
