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BRUNTONSAustralia

Visual

You might be towing a bucket.

Under sail, a fixed propeller is pure drag — owners who switch describe it as cutting away something they'd been towing. Here's the comparison at five knots.

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

What a knot buys

Over a 20-mile coastal day, up to a knot is nearly an hour

Six knots home instead of five means anchoring in daylight, catching the tide gate, or simply sailing when the fixed-prop boats give up and motor. Light air is where races are won and cruises are enjoyed — and it's exactly where prop drag hurts most.

What drag costs on a 20 nm day

Modelled

Up to a knot of drag on a 20-mile coastal day is roughly 48 minutes — the difference between anchoring in daylight and not.

Published framing: up to ~1 kn lost to fixed-prop drag → up to an hour on a 20 nm day

Feathering or folding for your boat?

The Builder scores both against how you actually sail — with the trade-offs stated, because we build both.

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