Pressure relief hole

[Steven88]

Is there any reason to put a pressure relief hole in either the drogue or main section of a dual deploy rocket? Since both are pinned with 2-56 sheer pins surely there is no reason no matter the altitude

 

[G_T]

Yes. I recommend doing so if your rocket isn't small. Don't over-do it.

The bottom part of the hole should be beveled so it can't become a ram air scoop under oscillations.

Gerald

 

[Steven88]

Ok. It’s 4” diameter Loc paper tube

 

[mbeels]

I hadn't considered this, are there any rules of thumb for pressure relief holes? Size and quantity per volume of rocket?

 

[OverTheTop]

I have one in each compartment of my 4" Velociraptor. 5/32" IIRC.

 

[dr wogz]

A vent hole also helps when you're putting the parts together.. No need to pre-stress your pins & such.. yes, the inner & outer will eventually equalize, but it'll take time for the inner air pressure to vent thru the various openings & gaps between the components..

 

[Bat-mite]

A vent hole also helps when you're putting the parts together.. No need to pre-stress your pins & such.. yes, the inner & outer will eventually equalize, but it'll take time for the inner air pressure to vent thru the various openings & gaps between the components..

Yes! Moreso than anything, it is helpful to have a way for air to escape when you are sliding couplers into airframes. You'll hear that nice "psssssss" sound as the coupler goes in.

 

[Bat-mite]

BTW, I put mine in the back inline with the rail buttons so that they aren't visible while the rocket is on the pad.

 

[Steven88]

So much good advice on this forum. Thanks everybody. Is a 5/32” hole pretty standard, and it really doesn’t matter where along the tube up or down the hole is placed, just whatever looks the best?

 

[Andrew_ASC]

You can look into sizing them for high altitudes but your rocket isn’t going high I assume so no need just a standard sized vent hole anywhere along the airframe where recovery gear won’t block it. A blocked vent hole is useless.

 

[Nytrunner]

So much good advice on this forum. Thanks everybody. Is a 5/32” hole pretty standard, and it really doesn’t matter where along the tube up or down the hole is placed, just whatever looks the best?

Doesn't really matter as you said. I like to put them towards the aft end since air will settle there during acceleration. Not critical, more of a 'for the heck of it'

 

[tim cubbedge]

Up to 4” diameter, I use 1/8” hole. Just make sure it’s below the shoulder of the nose cone. I might go 1-2” below the shoulder. Same on booster section, below the coupler by the same amount.

 

[Steven88]

You can look into sizing them for high altitudes but your rocket isn’t going high I assume so no need just a standard sized vent hole anywhere along the airframe where recovery gear won’t block it. A blocked vent hole is useless.[/QUOTE.


Not sure what is considered “high altitude” in the high powered rocket world but I’m assuming mine hasn’t reached that criteria yet as it weighs 5 3/4 lbs and flies on 38mm motors. I might get 4,000 max out of it. Haven’t simulated it yet.

 

[Steven88]

*4,000 ft

 

[Banzai88]

Make sure you put the hole where the recovery gear or ANYTHING that might block it isn't going to be.

 

[SammyD]

I use vent holes down to 2" rockets as it helps equalize pressures inside the airframes and nosecones. In the past, I'd noticed that dark colored nosecones would bulge substantially when exposed to the sun outside, changing the fit. This was due to air inside expanding from the heat generated by black paint. Solution: vent the bulkhead plate where my shock cord attaches, then vent the payload bay as well.

Consider this too: When a rocket is accelerating skyward rapidly, the pressure inside the airframe equalized on the ground. When it goes to lower pressure quite quickly, it creates high pressure inside the airframe versus the outside pressure which can lead to (or assist) early or premature separation of parts that might be sensitive to that pressure (friction fit nosecones come to mind). What worked on the ground might not at differing pressures.

Vent holes also ease assembly of components and add a little extra barometric sampling for the on-board altimeters...

 

[Chad]

As SammyD alluded to above, I've read plenty of stories about barometric altimeters getting confused without a vent hole nearby. I have a 4" Dx3 and used 1/8" vent. I have no real reason for 1/8" I think it was just the closest drill bit at the time

 

[Bat-mite]

Please don't confuse AV bay static ports (absolutely necessary for barometric altimeters) and airframe vent holes (options if using shear pins).