Blocks: How to find the right block for your yacht

Blocks: How to find the right block for your yacht

In this guide we tell you everything there is to know about which block to buy, what they are used for and the types of bearing available. We also have valuable tips to make sure you get the most life out of your blocks on board.


„Blocks then and now"

Blocks have been and still are an essential part of boating equipment. In the past, just as their name suggests, they were simply a block of wood, or to get technical, they were wooden blocks with a hole. They were used on board not only to run sheets and line, but also to facilitate carrying loads. Today, little has changed in principle. However, modern blocks feature an integrated bearing and are less prone to wear and tear, and above all, they are much easier to use.

Blocks then and now

What are the various block manufacturers and what is important when replacing them?

Blocks come in a wide variety of designs and sizes. This is hardly surprising, as most rig manufacturers, such as Lewmar or Seldén, produce their own blocks. They usually come with clear instructions as to exactly where and how they should be used. If a block needs to be replaced and it is a fixed part of the rig at a particular location, for example the mast base or masthead, it's worth looking at the rig manufacturer's specifications. This way, you can make sure it will work perfectly and you shouldn’t have any issues using it.

When replacing blocks, warranty claims can sometimes also be affected. It's important to comply with manufacturer specifications, for example on back stays. If a block fails due to it being the wrong type, not only do you risk damaging the rig, you could also have a problem with your yacht insurance.

This shouldn’t be the case if you are planning to set up a new rig, such as a self-tacking jib conversion or lazy jack system, and you can go ahead and buy whatever blocks you wish to use. Nevertheless, care should be taken when selecting the size of the block. You can use so-called mini blocks for lazy jacks, while self-tacking jibs require blocks that can carry much heavier loads.
Sometimes, original parts are no longer available for older yachts and new blocks are needed. To meet the demand for this equipment, various manufacturers offer a broad range of blocks, and a number of specialist manufacturers can satisfy the needs of any sailor with their own niche products:

Made in Germany

Made in Germany: Pfeiffer and Sprenger blocks, for dinghies and cruising sailboats

The German manufacturers Pfeiffer and Sprenger focus on cruising sailors with their tough blocks designed for durability. Both have a wide range of blocks, and they also supply all kinds of special fairlead blocks and so-called mini-blocks, e.g. for pennants or Lazyjackslazy jacks as mentioned above.

Blocks from Sprenger Blocks from Pfeiffer

Wood-look blocks from Hye

Wood-look blocks from Hye

Hye’s blocks have been favourites with veteran sailors for a long time, as their blocks look great on classic yachts. With their distinctive red-brown synthetic resin fabric made of Tufnol, Hye has created a classic block. They look similar to a classic wooden block, but are much lighter and more robust.

Blocks from HYE

The specialists: Blocks by Barton, Ronstan and Antal

The specialists: Blocks by Barton, Ronstan and Antal

Also using Tufnol, but not coloured, is Barton. Barton blocks are designed for more sporty sailors and yawl boats, where the low weight of Tufnol is a special feature of its products. A further manufacturer in the sports sector, the Australian manufacturer Ronstan, has made a name for itself with its Orbit blocks. Similar to Antal blocks, Dyneema loops replace the classic metal eyes for mounting on the fitting. The loops do not feature any bearings, but they have the advantage of being extremely lightweight and easy to handle, without requiring any maintenance. Both manufacturers make blocks with a technical performance and stylish appearance to match.

Blocks from Barton Blocks from Ronstan Blocks from Antal

Harken: The Rolls Royce of yacht blocks!

Harken: The Rolls Royce of yacht blocks!

The American manufacturer Harken offers a wide range of different blocks and sheet systems. They have sailboat blocks with high-tech bearings in wooden casings, as well as carbo blocks for the highest regatta demands. Harken dominates at high-profile sailing events, such as the Americas Cup, Volvo Ocean Race and the Olympics. But high quality comes at a price and some blocks may be excessive to all requirements.

Blocks from Harken

Our conclusion

The choice is indeed large, so for those who do not want to limit their search to one manufacturer, you should first determine what kind of block you need and where you intend to use it, then compare the different manufacturers.

What types of blocks are there for boats and what makes them different?

Sheave block - The most common design

Sheave blocks are usually mounted on the deck or boom with a shackle and run a line over a sheave. They are used wherever direction of tension has to be changed (mast base, foresheet, reef lines, etc.) Depending on the number of sheaves built into the block, they are referred to as single sheave blocks or multiple sheave blocks. The number of sheaves, whether one, two or three, depends largely on the mechanical advantage desired for the respective sheet. In addition to single blocks, double blocks are the most commonly used blocks. Double or multi-sheave blocks are used, for example, in the construction of a mainsheet jib

Fiddle block – perfect as a boom vang

A fiddle block. is another type of multi-sheave block. Here, the individual sheaves are not mounted side by side on a common axis, but one below the other, creating a shape similar to that of a violin or fiddle. This block is often found on smaller vessels and dinghies as a boom vang or mainsheet foot block. A cleat on the block can also help adjust and quickly release rope directly.

Snatch blocks - for quick line reeving

In special cases where a block is only needed temporarily, a special type of block can be useful i.e. a snatch block. Snatch blocks can be opened on one side, allowing them to be attached to a line under tension and removed again, even when the line is still taut. Snatch blocks are therefore often used as barber haulers on spinnakers. However, they are also suitable wherever lines need to be reeved quickly, as line does not need to be passed through individual blocks one after the other.

Ratchet blocks – perfect for reducing pressure on a sheet

Sheets are often pulled by hand on smaller boats. A ratchet block reduces the tug on a line, or sheet. Here, an inner sheave grips the rope, and a pawl prevents the sheave from turning in the direction of the load, producing the familiar ratchet sound. When the sheet is furled, the line, which then runs over the bearing roller, is also held. Because the sheave can rotate and grip, this allows for controlled easing of the line. On larger yachts where sheets are operated using winches, the reverse direction of the winch does this. Ratchet blocks are therefore mainly found in the sheet system of dinghies. They're often used with spinnaker sheets or in the mainsheet block. Many high-quality ratchet blocks also have a small lever to adjust the amount of hold.

Dynablock – a light-weight all-round wonder

Less weight is not only an advantage in regattas. Ultra-light Antal Dyna blocks can be used as a snatch block or mounted where fixed eyes and fittings are missing. Instead of a metal shackle, simply attach the Dynablock with a Dyneema eyelet. A popular choice on cruising yachts, not only because of the lighter weight, but more because they eliminate sources of squeaking and rattling on deck. On top of that, Dynablocks are extremely easy to install and can therefore also be added to a spinnaker or jib sheet as a barber hauler.

Deck organisers - lead / divert lines easily across the deck

Organisers and deflection blocks are designed to lead / divert lines across the deck. They come in many shapes and sizes and can consist of one or more sheaves. However, where a normal sheave block adapts to the direction of pull, blocks like this are designed to be fixed to a surface. Cheek blocks guide lines as low as possible to the surface they are attached to. Examples can almost always be found between the cockpit and the mastbase, to lead / deflect lines in a tidy fashion and avoid running them over a deck hatch. Cheek blocks are often used as deck oganiser blocks for this reason. Blocks that are designed to stand in a vertical position are called stand-up blocks. They are usually found at the mastbase, as a sheet block on a genoa car, or other applications where you don't want the block to hit the deck. Stand-up blocks, cheek blocks and organisers could be summarised as deck blocks. Also included here are deflection blocks that are mounted on a stanchion for leading furling lines aft, for example.

Summary of block types

  • Sheave block: Usually mounted on the deck or boom with a shackle. Use: Mastbase, foresheet, reef lines etc. Find them as single blocks or blocks with more than one sheave.
  • Fiddle block: Often found on smaller vessels and dinghies as a boom vang or main sheet foot block.
  • Snatch block: Often used to rig barber haulers on spinnakers.
  • Ratchet block: Reduces the pull on a line, or sheet. Mostly used on dinghies.
  • Dynablock: Dynablocks are extremely light, do not squeak or rattle and are easy to mount. Perfect for barber haulers.
  • Organisers: Organisers are fixed in place and immovable. Footblocks and are used, for example, to reduce the pressure on the mainsheet.

Which block is the right one for my boat?

Boat size

What role does the size of the boat play?

The choice of block is usually determined by the halyards and sheets used, not by the boat size. Larger rigs are often subjected to greater forces and lines have larger diameters. The crucial factors in determining which blocks to use here are the expected forces and the resulting breaking loads. If the block chosen is too small, it will not be able to withstand sudden tensile forces, for example caused by rough seas, and the block could break or bearings become damaged. Damage caused by this kind of excessive stress is not visible on the outside of the block. It only becomes apparent when the block is placed under load again, and the bearing jams due to uneven rolling surfaces. Manufacturers specify the maximum tensile force a block can withstand without damage.

SVB tip: It's best to keep the normal stress you place on your block to about half the breaking load of the line you are using. This should be the so-called working load, which allows for sufficient reserves in case of sudden, brief forces. Matching blocks directly to the line is not necessary for all installations. The angle of a diversion also plays a role in determining the size of the block to be used.

Example: When a jib pulls on a sheet, half of the force is distributed between the knot on the clew and half on the winch. In the case of a self-tacking jib, the line is fed through about 180 degrees to the bow via the fitting on the track and then diverted again through 180 degrees to the winch. 50 per cent of the force pulls on the respective ends of the line, but 100 per cent on the track and 100 per cent on the bow. Changing the direction by only 90 degrees instead of 180 degrees reduces the pull on the block fitting by about half. A change of only 45 degrees reduces the pull to a quarter. The lower the angle of diversion, the lower the expected load.

What role does rope diameter and rope type play in choosing a block?

In general, rope material doesn't really matter when it comes to blocks. As long as the line is used within the limits of its respective breaking load, choose a block with a slightly higher load-bearing capacity. A much more important factor than rope material is its diameter. The cross-section of the rope must match the width of the block sheave to avoid material wear. On the other hand, of course, the line must not be too thin, otherwise it will not grip the bearing and slip through. Wire rope blocks are an exception here. Their sheaves are subjected to particularly high demands. For this reason, especially suitable blocks should always be used for wire ropes.

Zweck des Blockes

What are different blocks used for and where?

Various blocks are used on yachts for different purposes. Multi-sheave blocks are used to reduce force and, for example, in jib sheet rigging. Where the block is located also often determines the type of block: on the barber hauler on the spinnaker, for example, light weight is a key factor. The block must not pull the sheet down in light wind conditions and thus cause the spinnaker to collapse. Conversely, for multi-sheave blocks, the mounting point on deck must take the combined force of the lines in the block. If direction of pull cannot be determined exactly, it is worthwhile to install a block with a swivel. This protects the deck fitting from excessive stress due to shear forces.

Summary of choosing the right block

  • Size of the boat: Not important when choosing the type, but relevant for halyards and sheets used.
  • Rope diameter: More important than rope material is rope diameter. The rope cross-section must match the width of the sheave in the block.

Which boat block bearing is suitable for which purpose?

Sheave, bearing, fitting. At first glance, all blocks look very similar. However, the differences are in the details and we need to take a look inside. Where a block is used determines not only its design, but also the recommended bearing. Yacht blocks are really tested at the mast base: during the course of a season, control blocks here are constantly subjected to halyard tension, especially after a roller furling system has been installed in the spring, for example. It will still be in place even when in the harbour, provided the genoa remains furled on the forestay. Therefore, the sheet block at the mast base must be particularly stable.

Plain bearings - run lines and halyards in one direction.

A halyard block at the mast base, and possibly also the masthead, must not only run smoothly to provide adequate halyard tension when setting the sails, it must also be able to withstand forces and loads acting on one point. This stress is exacerbated when a rig is working in swell. Water is by no means a rigid element, so the boat moves almost continuously. The bearings in a halyard block are therefore prone to uneven wear and must be manufactured to a particularly high standard. In such places, plain bearing blocks are the best choice.
In such places, plain bearing blocks are the best choice. They have many advantages compared to roller bearings: starting with low space requirements, resulting in a more compact design of the entire block. This is due to the running surfaces of the plain bearing block moving directly on top of each other. Only a thin film of lubricant reduces resistance.

Within a plain bearing block, the constant force of the halyard tension is distributed over a contiguous area. This significantly reduces wear and tear and increases service life. Moreover, plain bearings are usually manufactured to be maintenance-free and will not become dirty even if the bearing is not moved for a while. However, if tensile forces are not applied in exactly the right direction, they can be more sensitive, and due to the way they are designed, faults can occur in this case. Both running surfaces must be perfectly smooth, with exactly the right amount of force, so that there is no resistance. Plain bearing blocks are therefore always used where halyards can follow a clearly defined path and are mounted in exactly the same direction of pull.

Rolling bearings - when forces can act in all directions

One of the earliest types of roller bearing was discovered in the early days of shipbuilding. In order to launch entire ships into the water, logs were used to roll the finished hull down the beach and into the water. This principle can still be seen today in so-called rolling bearings. Instead of heavy tree trunks, cylindrical rolling elements and ball bearings are used. Ball bearing blocks are also a kind of roller bearing, since the balls roll between an inner and an outer ring, which reduces frictional resistance.

As load capacity is distributed over the contact surface of the bearings, in ball bearings, it is more specific. However, in roller bearing blocks, load capacity is distributed more evenly, since they have more surface area contact. The more rollers in the bearing, the smaller they are and more surface areas carry the load. Blocks with very small rollers are referred to as needle roller bearing blocks. Roller bearing blocks are not as sensitive as plain bearing blocks. They can also absorb lateral fluctuating loads well. With needle bearings, however, the pull should come from the same direction of installation. They should therefore only be used in places where direction of pull is fixed, as with deck blocks.

Ball bearings - the first choice for barber haulers, movable block fixtures and sheets

Classic ball bearings, on the other hand, are designed to rotate freely and can handle both radial and thrust loads. Ball bearing blocks are therefore always the first choice for all movable blocks on sheets, barbers and similar places. Their minimal resistance to movement. is achieved by the balls lying in a groove inside the bearing. These deep groove ball bearings can absorb lateral loads well without increasing rolling resistance.

Summary of choosing the right bearing

  • Plain bearing: Plain bearings are maintenance-free and seldom get dirty, but lines must run precisely for this.
  • Roller bearings: Can carry higher loads than plain bearing blocks.
  • Ball bearings: Ideal where loads are more moderate and dynamic. For spinnaker sheets and barber haulers.

Can I use a thinner line diameter than is recommended for a block?

In principle, blocks should be matched to the lines used. If line diameter is too large, you’ll usually be able to tell because the line won’t run freely through a block without shearing. But too small a rope diameter can also be problematic. This is because the guide groove of the roller in the block is matched to lines with the corresponding diameter. About half of them are carried and deflected by this groove over their entire surface. Thinner lines, on the other hand, take up a proportionally smaller part of the surface. Under tension, a line that is too thin line is then no longer run evenly around the sheave, but pulled down at the apex and squeezed into the groove. The result is a loss of breaking load of the line, as well as higher wear in the rope.

Blöcke warten

How often do I have to carry out repairs and replacements on the blocks on my ship?

Most blocks in sailing are maintenance-free. The housings are also usually riveted. A riveted block can therefore only be inspected from the outside. Open ball bearings or roller bearing blocks should be rinsed with clear water from time to time, especially when used in salt water. This will prevent salt deposits and the consequent formation of grooves. Lubrication is not necessary with these bearings and is even counterproductive, as grease in particular tends to slow down the rollers and prevent them from rolling freely. Moreover, plain bearings are usually enclosed systems, which makes maintenance unnecessary. However, blocks are also among the most stressed parts on board. Maintenance-free therefore does not mean that you don’t need to pay attention to them. A brief check from time to time can help prevent serious damage caused by block failure. Ideally, the roller should always move a little, even under tension. If it does not run smoothly, makes noticeable noises or you can see mechanical defects such as cracks, the complete block should be replaced immediately. - Therefore, always make sure you have a set of spare blocks on your ship.

Author Hinnerk Weiler

Author Hinnerk Weiler

Hinnerk Weiler is a sailing journalist, long-distance sailor and real "old salt". An experienced sailor and expert in boat technology, when it comes to the world of blocks on board, he knows what he's talking about.

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