The Harken 2638 40mm Carbo Air® Double Block with Swivel is a compact, low-friction sailing block engineered for high-load control line applications aboard dinghies, keelboats, and performance sailboats. Part of Harken's award-winning Carbo Air® series, this double block delivers a superior strength-to-weight ratio that racers and cruisers alike can depend on.
Compared to traditional Classic blocks, the Carbo Air® design is 30% lighter while offering a 60% higher working load — making it an exceptional upgrade for weight-conscious sailors who refuse to sacrifice strength. Torlon ball bearings run friction-free within a high-strength glass-filled nylon frame, ensuring smooth, effortless line handling under load.
The patented Harken U-Lock swivel system allows the shackle to lock in a front or side position for fixed applications, or release to spin freely to prevent line twist — a versatile feature for complex rigging setups. UV-stabilized carbon black materials protect the sheave, ball bearings, and sideplates from sun degradation for long-term reliability in harsh marine environments.
Key Features:
- Sheave diameter: 1-9/16" (40 mm)
- Overall length: 3-11/16" (94 mm)
- Weight with shackle: 3.2 oz (86 g)
- Maximum line diameter: 3/8" (10 mm)
- Maximum working load: 970 lb (440 kg)
- Breaking load: 2,380 lb (1,080 kg)
- Shackle pin diameter: 3/16" (5 mm)
- Torlon ball bearings for low-friction performance
- Glass-filled nylon sideplates with load-carrying curved bearing races
- Patented U-Lock swivel — locks front/side or spins freely
- UV-stabilized with carbon black for maximum sun protection
Common Applications: Main and jib sheets, mainsheet fine-tune, outhauls, cunninghams, vangs, and general control lines. Frequently used as a mainsheet boom block on Etchells class sailboats.
The Harken 2638 is a companion to the Harken Black Magic block line and is ideal for high-performance dinghies and small keelboats where every gram matters. Backed by Harken's reputation for precision marine hardware, this block is built to perform race after race.
