Ducted vs open props

Look at a whoop from above: each spinning propeller sits inside its own little ring, like a fan with a cage. Those rings are called ducts.

Ducts are bumpers. When the drone taps a wall, a chair, or (eventually) your ceiling, it boings off and keeps flying instead of breaking a propeller — and the spinning blades can't nick fingers, pets, or furniture.

Ducted means a full ring surrounds each prop in the horizontal plane — that ring by itself is the duct. It doesn't need a cap, dome, or strut above or below the blades; a plain ring around the prop circle is enough to count. We verify it from real product photos, because listings sometimes say "whoop" about drones with exposed props.

The trade

• Ducted: crash-proof-ish, finger-safe, indoor-friendly, and gates/obstacles become things you bounce off rather than things that end the flight. Costs a little weight and speed.
• Open props: lighter and faster, with less drag — but every touch risks a broken prop, and they're strictly fly-away-from-people machines. Best outdoors.
• Partial guards (side bumpers, rails): protect against wall taps but not from above or below — an in-between choice.

Starting out? Pick ducted. Every crash you shrug off is another flight you get to take.

Duct choice is a lap-time and consistency decision.

• Crash economics: in whoop racing, clipping a gate with a ducted frame usually costs a wobble; with open props it costs the heat. Consistency wins spec racing, and ducts are consistency insurance.
• Thrust behavior: ducts add a little static thrust at hover but cost drag at speed — one reason open-prop builds feel faster in a straight line and ducted whoops corner more predictably in dirty air.
• Spec classes race ducted: the 65/75mm race scenes standardize on ducted frames — parity, safety around spectators, and gate contact tolerance.
• Prop wash: ducted frames tend to recover from their own wash a touch more gracefully at whoop speeds; open 2S pushers punch through it instead.

A whoop duct is a shroud around the rotor. The physics:

• Static thrust augmentation: a well-fitted shroud reduces tip losses and can add lift at low airspeed (the duct's leading edge generates its own suction lift). At forward speed the duct's drag and mass overtake the benefit — which is why nothing fast wears full ducts.
• Tip clearance is the whole game: the thrust benefit collapses as prop-to-duct gap grows; molded frames hold ~fraction-of-a-mm clearances, and a bent shaft that lets a blade kiss the duct announces itself instantly.
• Structure: injection-molded PP/PC unibody frames put the duct ring, motor mounts, and battery bay in one flexible part — flex is the crash-survival feature, and it also sets the frame's resonance signature (soft frames want softer filtering in the tune).
• Acoustics: ducts shift blade noise up in frequency — the whoop "angry bee" sound is partly duct resonance.