Ronstan Blocks & Taljes

Base your selection on the expected system load (e.g., mainsheet/traveler significantly higher than Cunningham), the rope diameter, and the installation location (deck, boom, mast, cockpit). The safe working load (SWL) is the decisive factor as the practical value; the breaking load provides the safety margin. For cruising boats, a conservative safety margin is advisable; for dinghies, low friction and weight are also important factors. If you specify the boat type, sail area/boat length, and intended use (inland/coastal/ocean), the appropriate size can usually be narrowed down very quickly.

The rope should run freely without being pinched. As a rule of thumb: the rope diameter must fall within the range specified by the manufacturer; with very small pulleys, bending stress and friction increase. For trim lines (e.g., Cunningham), smaller systems are often sufficient; for mainsheets/travellers, larger pulleys and suitable bearings are significantly more comfortable—less effort, less wear.

Composite is lightweight, corrosion-resistant, and very popular on dinghies and sport boats. Stainless steel (e.g., AISI 316) is extremely robust and suitable for high-load fittings—especially on cruising yachts. Aluminum scores points for weight and stability, but requires special attention in saltwater: galvanic corrosion can occur when combined with stainless steel. Therefore, use suitable separators/insulators and ensure clean installation.

Soft attachments save weight, rattle less, and are very common on dinghies and performance yachts. Classic shackles are universal, quick to change, and often the first choice for cruising. It is always important to ensure the correct direction of force, sufficient breaking strength of the soft shackle, and abrasion-protected contact surfaces (no sharp edges).

Avoid hard stops: Use clean stoppers/anchor points, appropriate shackles/tabs, and route the rope so that it does not run sideways on the sheave. For taljes, correctly aligned blocks and sufficient spacing help prevent “shearing.” Soft attachments further reduce rattling. Regular rinsing with fresh water after saltwater use reduces salt buildup and friction.

The load path and mounting structure are important: forces must be transferred to a stable structure (backing plate, sufficient material thickness). Use appropriate screws/nuts (corrosion-resistant), protect drill holes, and seal them properly (suitable sealant). Ensure that blocks can move freely and do not rub against edges.

Inspect bolts/split pins, shackles/soft shackles, swivels, bearing races, and sheaves for cracks, nicks, or play. Rinse blocks with fresh water after exposure to saltwater and remove sand/dirt. Replace parts early if visible wear is present (rough-running bearings, worn sheaves, bent fittings)—this improves safety and ease of use.