External AltimeterOne mount?

I've got an Altimeter One. I've used it a few times in my Magician, (to 1834ft!) and put a hole in the clear payload bay. While most of my other rockets are showing their age, I'm still not big on poking holes in the BT's for venting.

Long story short, can I just tape it on the outside of the rocket?

In 'testing' the altimeter, I found blowing does not affect it, where as vacuum does. So, if taped to the outside, would it ignore the air rush of the launch, and then measure at apogee?

Maybe I could tape it opposite my keychain cam...?

I'm sitting here trying to figure out what orientation you could put it in that would neither have a ram-air effect into where the sensor is or have a low pressure area. The opening is under the circuit board tab that has the tethering hole. If you mounted it with that end down then there would be a low-pressure area behind it which would get worse as it accelerated, leading to falsely high altitude readings. (think base drag)

If were mounted the other way pressure would be increased by ram air....but as the rocket coasted to a stop at apogee it would see static pressure only. That might work depending on how the filtering in the software would interpret what happens. Of course it would be awkward (and draggier) to mount it "sideways".

Sounds like an interesting thing to do experiments on.....

Just make a small housing for it out of a piece of body tube and attach that to the side of your rocket.

-Kevin

With a little careful trimming of the shoulders I put my AltimeterOne, and drilled vent holes, in the nose cones. Obviously, this doesn't work on rockets with balsa cones, but I like it. It moves the little bit of extra weight forward, protects it more from ejection gases, and with a little bit of tape over the hole, provides an extra layer of protection from loss if there is clip trouble. And I'm a lot more comfortable with vent holes in the plastic nose than the paper body tube.

I'm not entirely confident of what would happen with it mounted externally. I'll try one soon and let you know.
So, my thoughts (educated guesses) at this point:
1. Err on the side of ram pressure versus venturi/Bournoulli effect-induced suction.
2. Point the "nose" of the altimeter up. The nose has the vent under it.
3. Because it's curved, I wouldn't try sideways. Might get venturi suction. Hard to mount that way, anyway.
4. Don't mount facing down. Likely to get low pressure in the wake of the altimeter.
Mounted nose-up, the AltimeterOne will accurately capture the ground reference (at rest). Then it will sense that the rocket is "dropping" as the ram air pressure increases the pressure, but it will ignore this, and it will not false trigger or lock the apogee if its perceived apogee goes up then down. As the rocket slows the pressure it senses will rapidly drop closer and closer to ambient. It will capture the lowest value it sees during the flight as the apogee.
*However*, if you have a strong arc-over situation (like into a wind with an over-stable rocket), you can hit apogee at some pretty good speeds. That means you'll have ram pressure and under-report apogee at that moment. If you can eject then, you'll slow down and catch a more accurate apogee. If you arc down a hundred feet, you won't be able to.
*And*, I'd be more sure of all of this if I was confident that turbulence and the air flowing over the rocket+altimeter didn't cause transient low pressures or "ringing" in the sensor. Dunno about that.
All in all, I'd say there's a pretty good chance it'll work, but I wouldn't bet on it until I had some side-by-sides done that verified it.
--John Beans, Jolly Logic