Altimeter Bay Design Calculator

Volume follows pi x radius-squared x length: diameter enters as a squared radius term while length enters linearly, so a given percentage increase in diameter compounds through the square and moves total volume more than the same percentage increase in length, at this calculator's default dimensions.

Yes -- total vent area is each hole's area (from its diameter) multiplied by how many holes you specify, so adding holes at a fixed diameter increases total open area in direct proportion. Drilling a fourth hole the same size as your first three adds another equal share of open area, exactly like adding a fourth equal-sized window to a wall.

The remaining-length output only budgets the altimeter board, battery, black-powder canisters, and a fixed wiring clearance -- it does not account for sled rail thickness, bulkhead hardware, or U-bolt clearance, all of which consume real length inside the bay. Treat a small positive remaining length as tight, not comfortable, and aim for at least 10-20mm of additional margin beyond what this calculator reports before you commit to a coupler length.

Avionics boards mount on a sled that slides in along the tube's length, so the board's LENGTH runs parallel to the tube axis and is already accounted for in the bay's total length budget -- only the board's WIDTH crosses the circular bore and needs to clear the inner diameter. Checking the board's diagonal would incorrectly assume it is mounted crosswise, which would reject boards that actually fit fine on a standard sled.

It estimates how quickly air pressure inside the bay equalizes with the outside through the vent holes, based on bay volume divided by vent area and the speed of sound. A larger bay volume slows equalization while larger vent holes speed it up, and at this calculator's default dimensions those two competing effects are close enough in size that neither one moves the result decisively more than the other.