Competitor4 vent holes question

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Well-Known Member
Apr 3, 2009
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Anyone have an opinion on how large and how many vent holes (to prevent separation) for a Competitor4 aft and payload section?
On both sections? And while we are at it, did you use shear pins, and what size BP charges? Thanks
Last edited:
Yes on both sections.

For the booster section I used two 2-56 inch nylon screws for shear pins. For the nose cone I use three 4-40 inch nylon screws for shear pins.

For the drogue charge I used 2 grams of black power and the back up was 2 grams. For the main charge I used 1.75 grams and set to fire at 900' and the back up of 2 grams set to fire at 700'.
I use 1 vent hole.... [5/32]... the payload and 1 in the fin can to relieve internal pressure.

3 .....5/32 vents in the altimeter bay.

3.. 2-256 shear pins in the nc to payload.

3grams bp in drogue....when flying small motors like j'& k's... they don't take up much volume, leaving more space to be pressurized.

1.5 to 2grams when flying L's and M's...with large motors there is sometimes virtually no space left inside. I have had to tuck my shock cord around the motor and the alt bay was just touching the top of motor.
Many fliers forget to take the difference of internal volume change, due to motor size into consideration when sizing bp charges.

2gr in the payload main, deploy.

nothing [shear pins] between airframe sections.

This rocket has flown from 2500ft to 16,000ft on J's to M's in this configuration.