Harken 40 mm Fly Block

Harken 40 mm Fly Block

The Harken 40 mm Fly Block is a soft-attach block built to provide sailors with remarkable strength and efficiency in an ultra-lightweight, aerodynamically clean package. Engineered specifically for high-tech line, this block delivers an incredible working load relative to its compact size, making it an outstanding choice for performance-oriented applications where every gram matters.

The 40 mm Fly Block features a one-piece titanium outer race and sheave, stainless steel ball bearings and inner race, and composite fiber-reinforced sideplates — a combination that ensures durability, smooth operation, and corrosion resistance under demanding sailing conditions. The soft-attach lashing design eliminates the need for traditional metal attachment hardware, reducing both weight and windage for a cleaner, faster rig.

This block is perfectly suited for use on foiling dinghies and high-performance sportboats, as well as vang cascades and backstay systems on Grand-Prix racing yachts. Its efficiency and strength-to-weight ratio make it a go-to choice for sailors seeking peak performance without compromise.

Harken equipment is designed for minimal maintenance; however, some upkeep is required to give the best service and comply with the Harken limited warranty. Keep equipment clean and free-running by frequently flushing with fresh water. Periodically clean with a mild detergent and water solution, spinning the sheave to distribute the solution evenly, then flush with fresh water. Note: Exposure to some teak cleaners and other caustic solutions can result in discoloration and is not covered under the Harken warranty. Lashing line is not included — compatible brands include Samson Amsteel Blue, FSE Ocean 3000, FSE Dinghy Control, and Marlow Excel Racing line.

Key Features

• Soft-attach design provides strength without mass in a low-aero profile
• One-piece titanium outer race and sheave for lightweight strength
• Stainless steel ball bearings and inner race for smooth, efficient operation
• Composite fiber-reinforced sideplates for rigidity and low weight
• Breaking load of 2,870 lbs (1,300 kg); max working load of 1,435 lbs (650 kg)
• Accepts up to 11/32" (9 mm) line diameter
• Ideal for foiling dinghies, sportboats, vang cascades, and backstay systems
• Lashing line not included