Definition
A chock is the cradle, fitted on the mothership deck or inside the garage, that holds a tender securely while the yacht is underway. It transfers the tender's static weight and its dynamic loads from pitch, roll, and slamming into the host vessel's structure without damaging the hull.
Background and use
Most tender chocks are tender-specific, custom-built or shaped during the new-build phase to match the chosen tender's hull lines. They are typically GRP or aluminium structures faced with closed-cell foam or rubber pads to spread load across the hull and avoid point contact. A well-designed chock supports the tender along its keelson and along two or three transverse bulkheads, distributing weight rather than concentrating it.
The reality is that tenders change. Owners replace boats every few years, and the new tender rarely matches the old one's hull form. Adjustable chocks (with movable pads on threaded rods, sometimes called universal chocks) solve this for production yachts that need flexibility, but they do not match the load-spreading quality of a purpose-shaped cradle. Many garages now use a hybrid: a hard-mounted base structure with replaceable upper pads that can be re-shaped or remoulded for the next tender.
In a sea-state, chock failure is the headline risk. A four-tonne tender breaking loose in a garage during a passage can destroy the garage interior and the tender itself. Lashing systems, hold-down strops, and active hydraulic clamps work alongside the chocks; the chock is the static support, the lashings handle dynamic uplift. Storm-stowage protocols on commercial yachts include explicit chock-and-lash inspection.
Related considerations
- Always specify chocks for a known tender, not in abstract; mismatch is the most common refit complaint.
- Closed-cell foam pads degrade with UV and saltwater; budget for replacement every two to three seasons.
- Drainage matters; standing water in chock recesses corrodes hull fittings and grows osmotic blisters.
- Confirm chock load rating against tender displacement plus a margin for fuel, water, and gear.
- Storm lashings are not optional; ISM-compliant operations require documented procedures.