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What's The Right Sheet For My Boat?

by Naomi Copperweight 6 May 09:00 BST
What's the right sheet for my boat? © Robline

Picking out the perfect sheet can be difficult, but we're here to help! Check out the information below for some tips on what you should consider when buying.

Diameter and Length

The diameter of a sheet is typically determined by two factors:

  • Strength of the material in relation to the loads on the boat
  • Handling characteristics (eg, by hand or on a winch)

For most gear on a boat, the size is determined by what the Safe Working Load is specified by the manufacturer. Sometimes it takes empirical relations, and rules of thumb to determine the expected loads so that deck gear can be properly matched.

The same method can be applied to sheets and other running rigging to find the 'optimum' diameter line for each application. However, with the improved strength properties of modern materials, selecting based on SWL alone will often lead to a line diameter which is less practical for handling purposes. For example, a 6mm performance gennaker sheet may have the required strength for a 30ft boat but an 8mm line will be preferable for handling.

The table below gives a rough guide to sheet diameter for a range of boat sizes:

 Under 24ft25-30ft31-37ft38-46ft47-55ft
Main Sheet6-8mm8mm8-10mm10-12mm12-14mm
Genoa/Jib Sheet8mm8-10mm10mm10-12mm12-14mm
Spinnaker/Gennaker Sheet8mm8mm8-10mm10mm10-12mm
Afterguy  10mm12mm14mm

Lengths of foresail sheets can be estimated based on boat length (LOA) as follows:

  • Jib sheet = 1 x LOA
  • Spinnaker / gennaker sheet or after guy = 2 x LOA

Material Selection and Splicing

The right materials for a boat can make all the difference. For cruisers and weekend regatta racers, there are plenty of versatile materials that will do just fine. Sports boats and other high-performance yachts should look for a range of specialised sheet materials.

Core material

For a cruising sailor, the basic starting point for all running rigging is polyester. A sheet with a polyester core can be soft, spliceable and cost effective. However, there is a downside of it's stiffness which does not live up to scrutiny when compared with UHMPE core materials like Dyneema®. This is not really a problem on smaller cruising boats and where budget is tight, polyester sheets will do the job.

For larger boats (40ft+) and more demanding cruising, it is worth thinking about upgrading. Low stretch options include blended cores of Dyneema® and Polypropylene. There are also pure Dyneema® or other UHMPE cores which should not break the bank. These lines offer better performance and a longer lifespan.

If you are sailing a performance cruiser or regatta then UHMPE fibres like Dyneema® and Stirotex are recommended. The question then is which product to go for. Cost effective options like Dyneema® SK78 and Stirotex are suitable for performance cruisers and most regatta sailors. If you are sailing a grand prix racing boat, we recommend the Dyneema® SK99 due to its high working load and negligible stretch.

Cover material

For a cruiser, the most popular choices is a polyester cover. Polyester is a cost effective choice and while it starts off slippery, with use it becomes grippy.

The requirements of a cover material are different for each sheet when it comes to performance. On sports boats, where a mainsheet is trimmed by hand, the material should be grippy and hold well in a cleat. On larger boats where the mainsheet is on a winch and being regularly trimmed, the cover should be durable to deal with the extra abrasion on the winch. A mix of Kevlar or Technora with polyester should be looked for.

On spinnaker sheets, the cover should provide heat and abrasion resistance for those big eases. Polyester mixed with Technora or Dyneema should be taken as a minimum spec. A jib / genoa sheet should also have good grip but the abrasion is typically less extreme. A polyester cover is acceptable as a basic option.

Splicing options

Adding splicing work to a headsail sheet on a cruising sailing boat is pretty much a no-brainer. A spliced line maintains its specified strength unlike a knotted line where the break load might be reduced by as much as 50%. A simple eye splice with cover offers a clean, neat connection to a shackle. At the cockpit end, a reeving eye or a whipping makes for a nice finish. The look of the splices varies by material and workshop but the fundamental principal remains the same.

Many performance boats will opt for stripped ends on spinnaker sheets to reduce weight. This means a section of the original cover is removed from the rope, exposing the core which can then easily be spliced into an eye. A jib sheet should also have an eye splice for a shackle. At the cockpit end, a reeving eye or a whipping makes for a nice finish.

Mainsheet splicing is very system dependent and can be anything from whippings on both ends for a German mainsheet to an endless splice for a continuous system.

Hardware options

A cruising sailing boat sheet needs a simple, cost effective shackle. Soft shackles are a cheap, lightweight, durable solution. At you can add hardware to the cart at time of purchase for splicing into running rigging.

Performance boats look for hardware that is lightweight and quick. A soft shackle is the lightest option by far, but can be a little fiddly to take on and off a sail. For performance cruisers this may not be an issue. Also on regatta boats, soft shackles may be fine on the jib sheets but for spinnaker gennaker sheets a quicker option is needed. Most racing boats will opt for quick release trigger shackles which can also be opened under load.


  • Step 1 - Choose the correct diameter
  • Step 2 - Calculate the length required from basic, easily available boat data but also take into consideration strength properties of modern materials
  • Step 3 - Core material choice is driven by boat size, performance parameters and budget!
  • Step 4 - Cover choice - Polyester is the most popular option when it comes to cruisers, but the requirements of a cover material are different for each sheet when it comes to performance.
  • Step 5 - Select your hardware

If you'd prefer to speak to one of our specialists, who can guide you through the process, contact us at and tell us what you need, or visit our website:

Running Rigging Help

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