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Calcimator

Altimeter Bay Design Calculator

Design your rocket's avionics bay. Calculate internal volume, verify component fit, and size vent holes for accurate barometric altitude readings.

Inputs

Results

Bay volume (cc)

304

Inner diameter (mm)50.8
Total vent area (mm²)95
Pressure time constant (ms)9.33
Component stack length (mm)180
Remaining length (mm)-30
Recommended vent holes3
Altimeter FitsNo
Battery FitsYes
Components FitNo
Vent Area AdequateYes
How to Use This Calculator
  1. Enter Body tube OD (mm), Wall thickness (mm), and Bay length (mm).
  2. Set Altimeter board length (mm), Altimeter board width (mm), and Battery length (mm).
  3. Adjust Battery diameter (mm), Number of vent holes as needed.
  4. Review the Bay volume (cc) result.
  5. Use Inner diameter (mm) and Total vent area (mm²) to inform your decision.

How the result changes with Body tube OD (mm)

Body tube OD (mm)Bay volume (cc)
38142.7
83750.2
1372,109.1
1823,766.3

What each input means

Body tube OD (mm)
Outside diameter of the avionics bay tube.
Wall thickness (mm)
Tube wall thickness. Typical: 1.5-2mm for phenolic, 0.8-1.2mm for fiberglass.
Bay length (mm)
Internal length available for electronics between bulkheads.
Altimeter board length (mm)
Length of your altimeter PCB. StratoLoggerCF: 50mm, Featherweight Raven3: 65mm.
Altimeter board width (mm)
Width of your altimeter PCB.
Battery length (mm)
Length of the flight battery (typically 9V or LiPo).
Battery diameter (mm)
Diameter or width of the flight battery.
Number of vent holes
Number of vent holes in the bay coupler. Minimum 3 recommended, evenly spaced.
Vent hole diameter (mm)
Diameter of each vent hole. 1/4 inch (6.35mm) is a common minimum.

What each result means

Bay volume (cc)
Internal volume of the avionics bay.
Inner diameter (mm)
Usable inner diameter after accounting for wall thickness.
Total vent area (mm²)
Combined open area of all vent holes.
Pressure time constant (ms)
How quickly internal pressure equalizes. Should be well under 100ms.
Component stack length (mm)
Estimated total length of altimeter + battery + BP canisters + wiring.
Remaining length (mm)
Spare room in the bay after components. Positive = fits.
Recommended vent holes
Minimum recommended number of vent holes for this bay volume.

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Body tube OD (mm) = 54, Wall thickness (mm) = 1.6, Bay length (mm) = 150, Altimeter board length (mm) = 65 = 9 input(s) provided
  2. Calculate Bay volume
    Bay volume = π * (innerRadiusMm / 10) ^ 2 * (bayLengthMm / 10)
    304 = 304
  3. Calculate Inner diameter
    Inner diameter = bodyDiameterMm - 2 * wallThicknessMm
    50.8 = 50.8
  4. Calculate Total vent area
    Total vent area = numVentHoles * singleHoleAreaMm2
    95 = 95

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