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BRUNTONSAustralia

The decision page

Fixed, folding, feathering or Autoprop — honestly.

We manufacture feathering, folding AND fixed propellers, so unlike single-product brands we don't need one answer to win. Here's the whole trade, including the parts that don't favour us.

Fixed 3-bladeFolding (Varifold)Conventional featheringAutoprop self-pitching
Sailing dragHigh — like towing a bucket (~20× a low-drag prop)Lowest — blades fold to a dartLow — blades edge-on to flowLow — blades feather edge-on
Powered efficiencyGood at its one design pointGood; fixed design pitchFair — flat blade sections cost efficiencyExcellent across the range — pitch follows load
ReverseWorks, with prop walkVarifold: opens astern by design, genuinely usableGood — blades flip to reverse faceExcellent — same blade face astern as ahead
Crash stop from 6 kn9.5 s — measured10 s — measured13 s — measured (conventional feathering)7 s — the shortest measured
Motor-sailingPitch becomes wrong as the wind helpsPitch fixed — same limitationPitch fixed (some adjustable at haul-out)Re-pitches continuously — its signature strength
Adjustment & upkeepNone — and no drag saving eitherGrease pivots; check bump stopsGrease; some brands need pitch set at haul-outAnnual grease; anodes; no pitch setting ever
Best forMotorboats & moorings where drag is irrelevantRacers & performance cruisers sailing 80%+Restricted apertures on classics & long keelsCruisers, motor-sailers, cats & electric drives

Drag figures from published independent testing (feathered ≈ 5–10% of fixed-prop drag; folded lower again). Powered/reverse characterisations reflect the documented behaviour of each architecture, not one brand's marketing — sources in the evidence library.

Handle the metal

Each architecture, in live 3D

Same bronze, three completely different machines. Switch between them and work the mechanisms — this is the comparison table with the words removed.

Drag to inspect · live 3D

Blades pivot on their own bearings and weathervane to the load. Cycle Ahead, Astern, Sailing and Hydro to watch the blades swing between working positions — astern presents the same face the other way round.

See it

Three identical hulls at five knots

Same boat, same breeze — only the propeller changes.

Relative drag at sailing speed, fixed 3-blade = 100%. Feathered ≈ 5–10% and folded lower again, per published independent testing — worth up to a knot under sail depending on the boat and conditions. What that means over a 20 nm day: arriving while the fixed-prop boat is still an hour out.
Relative propeller drag under sail
Propeller typeRelative dragTypical speed effect
Fixed 3-blade100%baseline
Feathering (Autoprop)8%up to +0.8 kn
Folding (Varifold)2%up to +1 kn

Questions owners ask

Is the drag difference really worth a knot?

In light air, often yes. Published testing puts a fixed 3-blade at roughly 20 times the drag of a folded prop; a feathered Autoprop cuts drag by up to 85% (one independent test measured up to 95%). On a typical cruiser that's up to a knot of boatspeed in the conditions where you feel it most — attribute it to your boat via the drag tool and Builder.

Why would anyone keep a fixed prop?

Simplicity, cost, and the fact that if you motor 95% of the time at one speed, a correctly sized fixed prop at that operating point is honest engineering. We'll tell you if that's you — we sell those too.

Where do conventional feathering props fall short of Autoprop?

Two places: blade sections (feathering blades are near-flat so they work in both directions, costing powered efficiency) and pitch (set once, sometimes adjustable at haul-out — but never adapting underway). Autoprop's blades carry true aerofoil camber and re-pitch continuously. The trade: Autoprop needs clean water flow and slightly more care about fouling.

I have a catamaran — does the answer change?

Twin drivetrains double every gain and every mistake, and saildrive cats want clean, symmetric prop behaviour for close-quarters handling. Over 1,600 of our documented fitments are multihulls — see the catamaran collection for what the fleet actually fits.

Still weighing it? Let the Builder score it.

Answer the usage questions honestly and the Builder ranks the types for your boat — with the runner-up and its trade shown, not hidden.