EBay Vent Hole

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Crazyrocket

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I know there is a lot of information in the forum on this (as I search and read through most of them), but I have a slightly different twist.

I am converting my AMRAAM 2.1 to DD (already did my AMRAAM 3), but due to the small BT size and other reasons, I am not going to put a power switch in the Ebay. I was planning on just going with the twisted wire method to arm the rocket. Due to the way the ebay is configured (to minimize the added length of BT), I am going to only put in one vent hole for my ARTS altimeter.

My questions is this - will it be a problem if I drill another hole for the wires to come out so I can arm it? I've heard you do not want two hole in the ebay, either 1 or 3 or more. I did not want to put the wire through the vent hole in the event that it might plug/cover the vent during flight. What's everyones opinion out there? Thanks.
 
You most likely already know this ... but. One vent hole is not the best idea. The reason is wind. When a wind blows into the single hole or across it, there is a good chance the pressure will change inside the e-bay and set your charge off. Three holes would be the best bet. Space them 120 degrees apart.


If you can not accomidate three holes then use two, space them 90 degrees apart. If you want to run the switch leads out the airframe, make one of the holes larger. I have done this several times and never had any trouble at all.
 
The ARTS uses an accelerometer to trigger the apogee event and the pressure sensor to trigger the main. Since pressure is not changing rapidly during descent (hopefully!) venting is not critical.

In most of my rockets that are setup for an AltAcc (including a PML Mini-BBX which is 2.1" diameter) the only vent holes are the two access holes for the altimeter arming screw and status LED. Which are by no means in the locations or sizes normally recommended for barometric altimeters.
 
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