Static Port Question

I'm building a very conventional Altimeter bay. The ID of the tube is 3.9" and it's 6" long and I want to use 4 holes. The Altimeter is a Stratologger CF. Using the formula in the CF book, the ports are .073" each. But using some other programs it's as much as .110" I'm gonna use the CF figure, but wondered what others do. Just curious as to any variations and why. Thanks!!

You didn't indicate the length of the tenon (aka, shoulder) of the av bay caps, so let's assume they have a depth of 0.25".

On the calculation program that I use, the diameter for 4 holes should be 0.101".

So that's another data point for you.

Greg

It isn't that critical. I would use a 1/8" drill but.

Thank to both!. The shoulder is indeed .250".

Wayco said:

I use the "Rocket Calculator" app on my IPhone.
For a 3.9" diameter tube 6" long, it calls for a .110 inch hole or 1/8" drill bit for four static ports. I usually round up to the next largest fraction. It really isn't that critical.

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Not to change the subject or hijack thread but what do you think of the "Rocket calculator" app?

timbucktoo said:

Not to change the subject or hijack thread but what do you think of the "Rocket calculator" app?

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I like it because it's handy. I only use the static port and ejection charge functions, it does a good job on those.

Wayco said:

I like it because it's handy. I only use the static port and ejection charge functions, it does a good job on those.

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Thanks. Been considering it but wasn't sure how useful it'd be.

So funny. This is identical to a thread I posted about a week ago. More details there.

More is better. "Over-venting" a payload isn't something to worry about, within practical limits. The guides should say "at least this diameter."
A reasonable size if you don't want to worry is to use 3/16" drill. (Not too big to be ugly, easy to see if they are clear.)
Three holes that size is good for over a foot long at 3.9", and about 8" long of 5" tube.

John Beans said:

More is better. "Over-venting" a payload isn't something to worry about, within practical limits. The guides should say "at least this diameter."

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In practice, I have seen this many times with my builds; good to hear it from an expert--thanks John.