Altimiter in a pyramid?

[Scrapmaster87]

20 years ago I built a foam board pyramid with an 18" or 16" square base that was awesome to fly on 29mm motors. The problem with that pyramid was that I used "featherweight" recovery, it started to fall apart after its 4th or so flight.

I'm in the mood to build a new pyramid, and this time my goal is to be able to work up to the Aerotech "I" dark matter motors (I280 and I327). Naturally I can't do anything easy so I want to be able to have parachutes and be able to take the sides off so it fits in the car.

These 6 pieces are what I have sketched up so far to 3D print, I think a 38/240 or 360 case will sit flush with the aft plate with larger motors sticking into the open base. What's shown will be about 16" square, but the sides should extend down to a 30" square. I'll roll some 38mm fiberglass tubes for the motor mount and the parachute tubes. The skeleton base shown here I'm figuring on epoxying and screwing onto a piece of fiberglassed luan.

The big question I need help answering is that can I just stick a barometric altimeter in the "nose" and just have holes in the sides? Or will I have to make up tubes sticking out into clean air? My preferred altimeter would be an eggtimer, I have a bunch of quarks waiting to be assigned.

 

[jmmome]

Been there- did that successfully. Sampling ports in a side panel. Worked perfectly. Mine weighed about 45 pounds. The second photo shows the side panel, with a rotary switch for the altimeter, and one for a timer. If I ever flew this again (I won't- too hard on the back), I'd ditch the timer and use a second altimeter.

 

[cbrarick]

I use a timer in mine. It's fairly straight forward and doesn't require a sample port.

 

[DAllen]

I use a timer in mine. It's fairly straight forward and doesn't require a sample port.

This is the right answer IMHO. I was stuck with a similar issue for my flying basket. There's just no good spot for a sampling port that is going to get smooth airflow over it so a timer seemed to be the right choice. You could however spend the extra $$ and use a Featherweight which I think can control deployment based on acceleration.