Folding vs feathering vs fixed: choosing a low-drag propeller

This is the question every sailing-boat owner eventually asks, and most answers come from companies that only make one of the options. We manufacture folding (Varifold), self-pitching feathering (Autoprop) and fixed propellers — so here's the whole trade, honestly.

What a fixed prop costs you

Under sail, a fixed 3-blade is a water brake — roughly twenty times the drag of a folded prop in published testing, worth up to a knot in light air. Under power it's correct at one operating point and compromised everywhere else. Its virtues are real though: simplicity, cost, and total indifference to fouling.

Folding: the racer's answer

Blades pivot aft and fold flat behind the hub — as close to no propeller as physics allows. If you race, or genuinely sail 80–90% of your hours, nothing else comes close. The historic weakness was reverse; a modern Varifold opens its blades astern by design, using hydrodynamic force as well as inertia, and backs down properly. The remaining trade: powered efficiency is that of a well-designed fixed prop, no better.

Feathering: the cruiser's answer

Feathering blades rotate edge-on to the flow under sail (5–10% of fixed-prop drag) and flip their faces for reverse. Conventional feathering props use near-flat blades — the price of working in both directions — and a pitch set by hand at installation. The Autoprop goes further: true cambered blades that set their own pitch continuously, which is where the 300–400 rpm cruise reduction and up-to-20% fuel savings come from. Its trade: it wants clean water flow and a clean bottom.

The honest matrix

• Race or sail nearly always → folding Varifold. Lowest drag, full stop.
• Cruise, motor-sail, count fuel → Autoprop. The efficiency case is documented and large.
• Tight classic aperture, long keel → conventional feathering may fit where others can't; turbulent flow behind heavy deadwood needs review regardless.
• Motor 95% at one speed → a correctly sized fixed prop is honest engineering, and we'll say so.

Still torn? The comparison page has the full table, and the Builder scores your actual usage rather than your aspirations.