Presets
Playback
Hull and crew
The rowers supply a fixed power; the faster the boat goes, the less thrust that power makes, until it equals the drag.
Model checks
The science
What is modelled
Mean oar thrust is crew power divided by speed (capped by what the oars can pull). It arrives as a half-sine pulse each stroke, so the hull speeds up and slows down. Drag is skin friction plus a wave-making term that rises with the Froude number.
Equations
- Friction
R_f = 1/2 rho v^2 S Cf,Cf = 0.075 / (log10 Re - 2)^2, wetted areaS = 1.7 L T + V / T. - Wave making (illustrative)
W (1.5 Fn^4 + 40 max(0, Fn - 0.38)^2),Fn = v / sqrt(g L). - Hull speed: wave length
2 pi v^2 / g = Lgivesv = sqrt(g L / 2 pi), about 2.43 sqrt(L) knots. - Surge
(1.1 M) dv/dt = T(t) - R(v).
Checks run in the page
- Steady speed by bisection against the pulsed time-stepped hull.
- Energy balance over 60 s.
- Hull speed solved numerically.
- ITTC line against an independent power-law fit.
- Stroke pulse mean and peak.
Honest simplifications
Wave resistance is a Froude-scaled illustration, not tank data for a chaika; oar slip, crew fatigue, wind, sail and shallow-water effects are left out, and the 150 N mean force cap and 10 % added mass are assumed.
What to try
- Press Heavily laden and compare the speed with the standard crew.
- Press Racing crew, long thin hull: a longer waterline raises the hull speed.
- Add rowers and watch the gain shrink as wave drag rises.