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marine • mechanical • bearings • sealing

360° Rotating Mast Collar

Low-friction, fully sealed deck partner assembly that allows continuous mast rotation for performance rigs while maintaining structural support and a dry deck aperture.

Rotating mast collar — iso view Plan view of rotating mast collar Internal clamp ring and detents Exploded/ghosted adjustment ring

Brief

Rotating masts on performance dinghies and multihulls reduce aero drag and improve sail entry angle, but the deck partner must carry compression loads, keep water out, and still allow smooth rotation under sheet loads. Off-the-shelf collars are either leaky, maintenance-heavy, or create steering-feel friction at the helm (from mast-rotation control systems).

This project delivers a compact, serviceable **360° rotating mast collar** (a.k.a. deck partner) with **low friction bearings**, **progressive preload**, and **redundant sealing**, tuned for composite or aluminium rotating spars.

Solution

  • Dual-path bearing system: a large-diameter thrust race handles mast compression; a separate radial guide controls lateral loads. Bearing materials selected for marine use (e.g., Torlon/PEEK rollers or PTFE-filled UHMW races).
  • Tool-less collar tensioning: external ring with detents lets crew dial in rotational friction/preload for conditions; positive stops avoid over-clamp.
  • Redundant sealing strategy: stacked lip + labyrinth seals and a drain annulus keep the deck aperture dry while allowing free rotation.
  • Isolation & durability: hard-coat anodised aluminium / 316 stainless fasteners with isolating shims to mitigate galvanic pairing with carbon masts.
  • Serviceability: split-collar geometry; bearings can be inspected/replaced without unstepping the mast.

Design Highlights

Preload ring with detents

Fine rotational torque control; tactile click-stops help repeat settings between tacks.

Replaceable bearing cartridges

Sealed packs drop in; options for ball or roller depending on mast load and environmental grit.

Safety and handling

Integrated lugs/eyes for safe handling and lashing during step/unstep operations.

Deck integration

Wide base flange spreads compression into bulkheads/partners; slotted holes simplify alignment.

Performance & Test

Bench rig measured <0.6 Nm starting torque at race-clean condition and <1.8 Nm at “beach sand” contamination (post-rinse), with no measurable leak in a 5-minute 50 mm head test. Collar survived 2× design compression load without brinelling.

Manufacture & Materials

  • Base & clamp rings: marine 6082-T6 or 6061-T6, hard-anodised; optional 316L stainless.
  • Bearings: Torlon/PEEK cage with 316 balls or PTFE-filled UHMW races for grit-tolerant use.
  • Seals: NBR or FKM lips + labyrinth; sacrificial wiper ring for sand.
  • Fasteners: A4/316 with Duralac/isolators where contacting carbon.