Choose a Harken ratchet block by matching sheave size to your line load, then deciding between a switchable ratchet (you turn the grip on and off) and a Ratchamatic (auto-engages under load, free-runs when eased). A 180-degree wrap roughly doubles the load but also delivers the most holding power, so size and lead geometry matter as much as the ratchet type.
Harken ratchet blocks at a glance
| Type | How it engages | Best for |
|---|---|---|
| Switchable ratchet | Sailor flips a center switch on/off | Full control across light-to-heavy air |
| Ratchamatic | Auto-engages under load, free-runs when eased | Hands-off trimming, dinghies and sportboats |
| Ratchamatic HTE | 20% stiffer spring, later engagement | Stays free-running longer for fast tacking |
| T2 Ratchamatic (soft-attach) | Auto-engage, lightweight lashable head | Weight-critical, adjustable lead height |
What is a ratchet block and how does it work?
A ratchet block lets you hold a heavy load with little effort and manage loaded sheets with good control. Resistance in the direction of the load comes from two elements: the grip of the sheave on the line and a pawl that stops the sheave from turning backward. The result is that you can hold a line loaded far longer, reducing hand fatigue, easing constant trimming, and letting you feed line with more precision.
How do I choose the right size?
Match the sheave diameter to the loads the block will see, and remember that a 180-degree turn on a block doubles the load. A larger-diameter sheave produces more contact area with the line, which provides more holding power. That is exactly why ratchet blocks are most effective on a 180-degree wrap: the line stays in contact with as much of the sheave as possible.
Switchable or automatic (Ratchamatic)?
Many sailors prefer to turn the ratchet function on and off themselves. A switchable ratchet gives you a free-running block in light air, when there is not enough pressure to pull the rope through, then an engaged block once the breeze builds. The switch sits in the center of the block so it cannot be flipped by accident.
The alternative is the Ratchamatic. Its mechanism only engages when the block is loaded: under load it helps you hold, and when the load is removed the ratchet disengages and the block runs free. You can tune the spring engagement pressure with the included hex key to suit your strength and system - turn anti-clockwise for heavier settings. Harken's HTE (high-threshold engagement) option uses a 20% stiffer spring at the engagement point, so the block stays free-running for longer before it grips.
Shackle or soft-attach?
If you want a lightweight ratchet block, the 40mm and 57mm T2 Ratchamatic blocks are an excellent choice. A soft-attach head lets you lash the block at alternating heights to keep a perfect lead, and the T2 Ratchamatics use 50% fewer components, which keeps them light and reliable.
Frequently asked questions
Does a 180-degree wrap really matter?
Yes. A 180-degree turn on the sheave roughly doubles the load but also maximizes line-to-sheave contact, giving the ratchet its most holding power. Ratchet blocks are most effective on that full wrap.
What is the difference between switchable and Ratchamatic?
A switchable ratchet is turned on or off manually with a center switch. A Ratchamatic engages automatically under load and runs free when the load is eased, so there is nothing to flip.
What does HTE mean on a Harken ratchet block?
HTE stands for high-threshold engagement. It uses a 20% stiffer spring at the engagement point so the block stays free-running longer before the ratchet grips.
Can I adjust when a Ratchamatic engages?
Yes. Each Ratchamatic includes a hex key to change the spring engagement pressure - turn anti-clockwise for a heavier setting to match your strength and system.
Why choose a T2 soft-attach ratchet block?
The T2 Ratchamatic saves weight with 50% fewer components and a lashable soft head, letting you set the block at alternating heights for a perfect lead.
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