Form, Function, and Uses of Lashing Blocks

When a pulley block relies on soft goods (rope or straps) to secure it between its load and an anchor point, rather than hard fasteners, it is a lashing block.  Lashing blocks provide a versatile setup that can be used for single pulleys or whole block and tackle pulley systems to lighten the rigging and give more generous flexibility to the load. 

However, the different forms and functions of lashing blocks can make picking one out a bit confusing.  If you’re wondering whether a lashing block is right for your purposes or don’t know which kind of lashing block you need, then Ronstan is here to help. Here are a few tips to help you find the ideal block for the job:

Standard Bearing vs. Ball Bearing

Traditional pulleys set a sheave (the wheel) on a bearing (the axle), where it spins as it feeds the rope around its diameter. For static loads, this approach works out fine. However, in situations where you need to reduce friction—perhaps due to extreme loads or frequent use—you should be using “ball bearing” blocks.  Ball-bearing blocks aim to spread the load across rollers or balls (instead of one axle) that roll between the sheave and the center of the block.

 

For example, Ronstan Industrial offers a Lashing Orbit Block™ that’s tuned for high breaking loads.  The Torlon® needle rollers help the block perform at strengths up to ten times that of steel, but it’s lighter, more compact, and produces far less friction. Acetal ball bearings guide the load and protect it from sideloaded forces that would contact the cheeks, while the heavy-duty Torlon® needles manage the load on the block itself.

Straphead vs. Loop Blocks

Lashing blocks usually attach to soft goods in one of two ways: either through the center of the sheave or through the head of the block, above the sheave.

  • Strapheads: A webbing attachment fixed to the head of these blocks holds the lashing rope in place away from the sheave.  Unlike traditional pulley heads—which feature metal fasteners to hook, screw, or bolt the pulley to an anchor point—a straphead lashing block can mount easily anywhere you can tie or run a rope.  It also makes for lighter, softer, more flexible rigging, as there are fewer metal parts and the pulley has a full range of motion to align with the load.
  • Loop Blocks: The lashing rope runs right through the open center of the sheave in a loop block.  These are even lighter than strapheads because they don’t require so much load-bearing structure in the head since the sheave is reinforced to be the sole load-bearing element in the block.

It’s crucial to remember, however, that lashing blocks are NOT interchangeable.  A rope that’s run through the head of a loop block risks failure of the block, as the head is not designed to withstand the same high load that the sheave can support.  Likewise, a rope run through the sheave of a straphead block could also risk damage to the sheave or the rope. Cutting or chafing could compromise the rope since the edges of the sheave were not designed for contact with soft goods.

Uses For Lashing Blocks

Ronstan lashing blocks were designed for the rigors of professional sailboat racing, where they ensure that soft, light rigging doesn’t ding the deck or bang against the boom. But they also see use in many industries with similar needs for durable, high-performance blocks attached to soft goods, such as:

 

Shade Systems: Fabric structures, shade sail hardware, and other tension-based shade systems reap tremendous benefits from the lightweight, free-moving rigging offered by lashing blocks.  They can be mounted anywhere (poles, ropes, hooks, trees) and won’t bang or rattle against supports like pulleys that use metal attachment hardware.

The Arbor Industry: Lashing blocks don’t require any specific attachment—which makes them adaptable and versatile to the needs of tree removal and lumber hoisting equipment that must adjust based upon the size and shape of the load.  It also helps that they’re self-aligning with the ideal lead.

 

Lashing blocks are the perfect choice for any task that requires minimal weight and the freedom to flex with wind or dynamic movement in the system.  

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Ronstan’s end-to-end design, manufacture and distribution operation delivers high specification products for all serious hardware applications.

Our state-of-the-art design facilities and manufacturing plant handles more than 4.9 million units each year.

As one of the top three sailboat hardware brands globally we know what it is like to deliver great equipment that can handle challenging conditions.