Sailors repeat 'it's like towing a bucket' because it's true. Published drag testing puts a fixed 3-blade propeller at roughly twenty times the drag of a low-drag alternative. Here's what that means in sailing terms.
Where the drag comes from
A stationary blade square to the flow sheds turbulent vortices — pure resistance. Locked or freewheeling barely changes it (and freewheeling adds gearbox wear; see vibration and noise). The only fixes are geometric: turn the blades edge-on (feathering) or fold them away entirely.
What it's worth
- Up to a knot of boatspeed in light air on typical cruisers — the difference between sailing home and motoring home.
- Feathered blades: roughly 5–10% of fixed-prop drag.
- Folded blades: lower again — effectively a streamlined cone.
- Over a 20-mile coastal day at 5 vs 6 knots: nearly an hour.
Why light air is the whole story
Drag rises with the square of speed, but sail power collapses faster in light air — so the drag penalty hurts most exactly when you have least to spend. Australia's east-coast summers are a light-air catalogue; ask any club racer what a knot is worth in February. See it visualised in the drag comparison, then decide between folding and feathering honestly.
Apply it to your boat
Theory is free; the recommendation is too. Verified by an engineer within one business day.
See the drag comparison