CALCULATORS / MARINE AND UNDERWATER DEVICES

Marine thruster screening calculator

Static thruster coefficient model using supplied measured thrust coefficient.

marine-thruster.napkin / editable

SCENARIO COMPARISON

Compare the numbers.

This source describes an analytical model. Its quantities and checks are the view.

Scenario	periods	thrustN
	0.02	51.25
	0.02	41

All calculated quantities are listed with the inputs. Switch to Source to inspect the equations.

SCENARIOS / CALCULATED VALUESSAME SOURCE

Change an input to see the consequences.

static thrust target51.25 N✓ passes

BASELINE INPUTS

density1025 kg/m^3diameter0.1 mspeed3000 rpmcoefficient0.2

CALCULATED

period0.02 s

thrust51.25 N

Edits change the baseline source.

THE SOURCE

Edits below update the same model.

# Marine thruster screening
# Scope: Static thruster coefficient model using supplied measured thrust coefficient.
# Status: illustrative worked example; engineering review pending.
# Inputs are example values. Checks are editable example requirements, not standards.

density = 1025 kg/m^3
diameter = 0.1 m
speed = 3000 rpm
coefficient = 0.2

period := 2*pi/speed [s]
thrust := coefficient*density*diameter^4/period^2 [N]

check static thrust target: thrust >= 40 N

scenario alternative: density = 820 kg/m^3

Calculated from your source · not saved

Baseline · Baseline

static thrust target51.25 N ✓ passes

alternative · alternative

static thrust target41.00 N ✓ passes

Illustrative first-order example. Checks are editable requirements, not design standards. The broader topic may require additional equations, data, and validation.

Formula and units

This example uses the following equations. Input names and units match the editable source above.

period: period = 2*pi/speed [s]
thrust: thrust = coefficient*density*diameter^4/period^2 [N]

Original worked example

These are the baseline values in the downloadable source. Edits above let you test your own values.

Given

density: 1025 kg/m^3
diameter: 0.1 m
speed: 3000 rpm
coefficient: 0.2

Calculated

period: 0.02 s
thrust: 51.25 N

Assumptions and limits

Static thruster coefficient model using supplied measured thrust coefficient.

The requirement checks use the limits written in this example. Passing a check does not establish that the model covers every load, material behavior, or operating condition in a real design.

Download this .napkin example ↓

Take it further with your agent

Napkin keeps the inputs, equations, checks and assumptions together in one study. Your agent sets it up; you change the numbers.

Try with Claude ↗

codex 'Use Napkin (https://napkin.engineering/mcp, or the local Napkin plugin) to build a study: Marine thruster screening. Inputs: diameter; speed; density; calibrated coefficients. Outputs: conditional thrust and shaft power. Model scope: Hydrostatics and calibrated hydrodynamic coefficients. Read napkin_capabilities and the current snapshot. Ask me for the values that matter, label assumptions with units, author .napkin source, validate it and apply it with napkin_source using the current revision, then open the study. Add checks for the limits I supply. Keep unsupported analyses explicit.'

Claude needs the Napkin connector; Codex needs the Napkin plugin. Set up your agent ↗

The broader study

The topic brief below describes the broader scope. The worked example above states the particular calculation it implements.

Inputs: diameter, speed, density, calibrated coefficients
Outputs: conditional thrust and shaft power
Modes: calculate, compare, sweep
Drawing: Hull and underwater load diagram

EXECUTABLE WORKED EXAMPLE · FIRST-ORDER MODEL · CHECK THE SCOPE & ASSUMPTIONS