Ronstan Series 55 Auto/Manual Ratchet Orbit Block

The Ronstan Series 55 Auto/Manual Ratchet Orbit Block gives the trimmer a choice between load-sensing ratchet assistance and manually selected ratchet operation. That flexibility is useful on mainsheets and other heavily handled lines where extra holding power is welcome in a breeze but free running is preferred during quick maneuvers. The machined ratchet sheave is shaped to grip loaded rope without making controlled easing difficult. Because the block can be switched between operating modes, it can be tuned to the crew and conditions instead of forcing one behavior all day.

Ronstan builds the ratchet sheave from hard-anodized aluminum and supports it with a low-friction bearing system suited to repeated trimming. Fiber-reinforced cheeks keep the body light, while corrosion-resistant load hardware is intended for regular marine exposure. The Series 55 format is large enough for substantial sheet loads but still compact enough for dinghy, sportsboat, and small-keelboat control systems. Its swivel attachment also helps the block follow the working angle of the sheet instead of holding the rope against one cheek.

• Selectable automatic or manual ratchet operation
• Machined gripping sheave for added holding assistance
• Swivel attachment for changing sheet angles
• Lightweight composite and corrosion-resistant construction

Ronstan specifies line up to 10mm, a 550 lb maximum working load, and a 1,430 lb breaking load for this version. The block weighs about 2.9 oz, so it delivers ratchet assistance without adding much moving weight to the tackle. Set the operating mode before heavy trimming and keep the sheave clean so the gripping surface and ratchet mechanism remain predictable. For more ratchet blocks and mainsheet hardware, browse more Sailing Hardware.