Static Pressure Port Holes

The Rocketry Forum

Help Support The Rocketry Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

amiliv

Well-Known Member
Joined
Jul 2, 2018
Messages
124
Reaction score
49
I know. "Static Pressure Port Holes" gets asked *all* the time. But fear not, I'm not going to ask how many, how big, or how far from the nose cone to put 'em :)

I've AV bay with switch band, and I'll be drilling a couple of static port holes around it. So far so good. However, due to the design of the sled, the switch for the altimeter will end up few inches below the switch band. If I were to drill access hole for the switch few inches below the static port holes, will this additional hole cause airflow and/or odd pressure changes during (likely supersonic) flight and interfere with the dual deploy altimeter functioning correctly?
 
I know. "Static Pressure Port Holes" gets asked *all* the time. But fear not, I'm not going to ask how many, how big, or how far from the nose cone to put 'em :)

I've AV bay with switch band, and I'll be drilling a couple of static port holes around it. So far so good. However, due to the design of the sled, the switch for the altimeter will end up few inches below the switch band. If I were to drill access hole for the switch few inches below the static port holes, will this additional hole cause airflow and/or odd pressure changes during (likely supersonic) flight and interfere with the dual deploy altimeter functioning correctly?
A hole some distance below the static vent will not effect airflow at the static vent.
 
I have several av-bays with various size holes. Some have three calculated size holes and then a huge hole for the screw switch. I have several others that have the vent holes in the switch band and large holes in the lower shoulder for screw switches. Those are not uncovered until apogee, but they have never been an issue.

A baro altimeter needs accurate reading at three points and none of them are during high speed flight. The first is on the pad to get the zero point. At apogee for the drogue charge, and while falling from apogee to deploy the main. I figure how accurate the baro readings are during high speed flight are not really that important. As long as the altimeter knows it's still gaining altitude. Once near apogee, you're moving slow so turbulence is not much of an issue and that's when the altimeter needs more accuracy to sense apogee correctly. During the fall from apogee, you never hit high speeds, so again, the porting doesn't make a whole lot of difference as long as it isn't too small.

Don't over think it. The placement and size of the vent holes are very forgiving and as long as they aren't too small, you have a lot of latitude on size and placement.
 
Back
Top