Please select your home edition
2024 fill-in (top)

Fiddle Blocks for a low-profile purchase system

by Calanach Finlayson 16 Mar 2023 09:00 GMT
Looking at fiddle blocks © Calanach Finlayson

A fiddle or violin block is a twin-sheave block with a difference. Typically cheaper than a standard double block of equivalent size, its low profile makes it ideal for on-deck purchase systems. In this article we explore the pros and cons of fiddle blocks and where they can be put to use.

What is a Fiddle Block?

So called because of its visual resemblance to the musical instrument, a fiddle block (aka violin block) features a secondary smaller sheave in plane with the primary sheave. This is in contrast to a standard double block where two equally sized sheaves are mounted in parallel about a single axis.

Looking at fiddle blocks - photo © Calanach Finlayson

Beyond that, the variants are as diverse as any block: aluminium, stainless, composite; ball bearing, roller bearing, plain bearing; fixed becket, soft becket; swivel head, lash head; cam cleat, V-cleat etc.

Looking at fiddle blocks - photo © Calanach Finlayson

Fiddle Block vs Double Block?

A 4:1 purchase can be achieved with a pair of standard double blocks. One of the blocks must additionally feature a becket to terminate the line. The same system can be configured from a pair of fiddle blocks (again, one must have a becket). So what's the difference?

Looking at fiddle blocks - photo © Calanach Finlayson

Let's first consider the load case. Ignoring friction and losses, each line in this system carries an equal force which is a quarter of the output force. The mechanical advantage of the system is 4:1. Therefore it appears to make sense that all sheaves should have the same size and bearing style.

However, the other effect of a mechanical advantage is the reduction of line speed throughout the system as you progress away from the input control line. Fiddle blocks take advantage of this by utilising smaller secondary sheaves, often with lower cost bearings. The result is that fiddle blocks are typically cheaper than their twin-sheave equivalents.

The following table shows a snapshot of fiddle blocks and their double block counterparts, selected at random from six different manufacturers. Note that this is not a comparison between manufacturers, but a comparison within a block range from each manufacturer.

ModelSWL (kg)RRP
Harken 40mm Carbo Air ‑ Double440€ 78.55
Harken 40mm Carbo Air ‑ Fiddle220€ 57.00
Ronstan 40mm BB Orbit ‑ Double500€ 80.19
Ronstan 40mm BB Orbit ‑ Fiddle325€ 51.71
Ubi Maior 50mm YC ‑ Double750€ 152.92
Ubi Maior 50mm YC ‑ Fiddle750€ 152.92
Antal 34mm SS ‑ Double400€ 73.11
Antal 34mm SS ‑ Fiddle400€ 59.38
Lewmar HTX 50mm ‑ Double800€ 161.26
Lewmar HTX 50mm ‑ Fiddle800€ 123.47
Wichard 45mm BB ‑ Double480€ 82.00
Wichard 45mm BB ‑ Fiddle560€ 63.00

On average, a fiddle block is 20% cheaper than its double block equivalent. The catch of course is to check if the working load is not also reduced due to the smaller secondary sheave which may be a limiting factor.

But if line diameter is the key selection criteria rather than SWL, a fiddle block can be a great option. The additional benefit of fiddle blocks over double blocks is their low profile which means they present less windage, particularly if used flat on the deck.

There are of course drawbacks: Reduction in SWL is a common one. You can also expect added friction compared to a double block with two equally sized ball or roller bearing sheaves.

Looking at fiddle blocks - photo © Calanach Finlayson

Applications and Summary

As we have seen, fiddle blocks are typically cheaper than their double block counterparts, sometimes for the same SWL. This makes them an attractive option for most applications where a standard double block would otherwise be used. The additional benefit of reduced windage makes fiddle blocks even more favourable for a racing boat.

Uses include:

  • Vang purchase systems - either as a finished 4:1 system or in addition to cascades
  • Jib inhauler or up/down control
  • Running backstay or mainsheet fine tune

If you have any questions please feel free to email us at , or click the link below to see our full range:

See the range

Related Articles

Soft shackles are a win-win solution
Upffront look at their use across multiple applications Soft shackles have surely penetrated the mainstream sailing in recent years. They are a popular alternative to traditional metal shackles. Made from single braid Dyneema® soft shackles offer several advantages over their metal counterparts. Posted on 8 Feb
Vakaros Atlas 2 - sailing with ultimate precision
A careful review by the experts at Recently have introduced the latest Vakaros Atlas 2 sailing instrument to the shop and compared it in a review of other top sailing instruments. Posted on 25 Jan
Sailing instruments from Velocitek/Sailmon/Vakaros
An introduction and comparison from The term 'sailing instrument' is broadly applicable to just about any onboard system with a sensor and a readout. While wired instrument systems are common, in this blog we discuss portable GPS sailing instruments from Velocitek, Sailmon and Vakaros. Posted on 11 Jan
Standing Rigging
Why your standing rigging will benefit from replacing steel wire with composite fibre Why will your standing rigging benefit greatly from replacing the steel wire with composite fibre stays? I have been thinking of the advantages of composite rigging while following the different races and yachts challenges circumnavigating the world. Posted on 14 Dec 2023
Block and tackle
Understanding mechanical advantage on sailing boats A rough guide to mainsheet purchase systems by A block and tackle or 'purchase' system is a form of mechanical advantage, where the input force is multiplied through a series of pulleys or blocks to create a much larger output force. Posted on 23 Nov 2023
Winterising a boat - useful tips from
Dave Proctor explains how to avoid some unpleasant surprises next spring Winterising the boat is a common task for many boat owners, regardless of where your boat is located. For some, in milder conditions, it means keeping everything dry and tidy, but for many the need for packing up the boat for winter is a necessity. Posted on 1 Nov 2023
Winning deck hardware of a Star World Champion
Max Kohlhoff Today we are speaking about deck hardware and rig setup with Max Kohlhoff, the winning helmsman of the 2023 Star Worlds. With Ole Burzinski from Flensburg Yacht Club, onboard Playmate, they recently scored two bullets out of six races in Scarlino. Posted on 26 Oct 2023
Polyform AS and Polyform US fenders
Exporting quality and performance from Norway to the U.S One of latest additions to the sailing hardware line-up are the Polyform fenders from the original Norwegian manufacturer - Polyform AS. Established over 60 years ago, Polyform AS is renowned for inventing the modern plastic buoy. Posted on 18 Oct 2023
Electric Furler from Facnor
Latching on the trend of boat electrification The sailing world is undergoing a sea change, embracing the power of electrification for unparalleled ease and convenience, especially for older crews and solo sailors. Electric systems are revolutionising boats. Posted on 11 Oct 2023
Best bottom up furlers
Top five as rated by In this article we round up five of the best bottom up furlers on the market. Choosing the right furler is a question of boat size and SWL (safe working load), sail area, performance level and budget. Posted on 5 Oct 2023