Sailboat Sheets and Guys are ropes or lines that are used to trim a sail.
Sheets are attached directly to the clew of most sails, the exception being the mainsail. Unless they are loose footed, main sheets are attached to a boom which is then attached to the clew.
Guys are commonly used in conjunction with spinnaker poles and are attached to the tack of the sail.
The demands on sailboat sheets and guys vary a great deal for different applications and types of sailing.
Increased loads on bigger sails mean that diameter, construction and the fibre content all need to be considered when optimising for performance and cost.
The filters on each category page will help you determine the size of line you require. There are filters for racing specification and cruising specification. Once you have chosen the size and type of your sheet, you can apply the rule of thumb below to calculate an approximate length required.
This is a general guide for selecting a suitable line: Running Rigging Rope Fibres and Construction Explained
Estimating Sheet Lengths
Mainsheet, simple purchase that ends in a jammer on the block
Calculation for a boom that can go out the full 90 degrees
Measure the distance from the gooseneck to the mainsheet attachment on the boom. Use Pythagoras Theorem to calculate the Hypotenuse. You can assume that the other two sides of the triangle are equal. Multiply the hypotenuse by the number of lines (purchase) add a bit for good measure, and add a tail.
Mainsheets are commonly 4:1, but can be 6:1, 8:1 or even more.
e.g. a mainsheet attached to the end of a boom 3 metres long with a 4:1 purchase would be approximately √ (3m2 + 3m2) = approximately 4.25 x 4 = 17 metres plus a precautionary extra bit, plus a tail.
Calculation for a boom that will only go out to a 60 degree angle
The swept back angle of the mast spreaders may severely limit the distance the boom can go out and therefore reduce the length of the mainsheet. For a 60degree angle, all three sides of the triangle will be equal, so multiply the measurement from gooseneck to attachment point by the purchase, add a bit for good measure, and add a tail.
Interpretation is required where a boom goes out 70-80 degrees
However, the boom is likely to go out somewhere between 60 degrees and 90 degrees, so you will need to interpolate between the two calculations.
Don't forget to allow for a tail.
Mainsheet with dedicated winches - draw a plan of the arrangement for a rough guide.
Genoa Sheet - 1.5 x boat length An inner forestay will increase the length required. The lazy sheet will need to go around this as well as the mast
Jib Sheet - 1.25 x boat length
Spinnaker Sheet or Guy - 2 x boat length. Code Zero or Gennaker Sheet - 2 x boat length
There is no better way to gauge the correct length than to measure the existing line and add an extra metre or two if necessary N.B. make sure that it is long enough for all points of sailing.
If you don't have a working line to replicate, and subsequently need to estimate the length from a sketch/diagram of the rigging set-up, don't forget to allow for a tail from the winch. It is also advisable to add on a metre or two to make sure the line isn't too short.
Guidance on selecting the best rope for a new or replacement Sheet or Guy
Low Stretch is still important but not so critical for as it is for a halyard unless you are looking for Regatta Performance or considering extended offshore cruising (or Racing).
Comfort in the hand and performance around a sheet winch should be prominent factors in the decision-making process.
Sheets and Guys which are effectively Control Lines are categorised into:
Cruising Sheets and Guys
100% Polyester Lines which have approximately 4% - 5% stretch
LIROS Braid on Braid EVO is the new generation, lower stretch, high-load version of LIROS Braid on Braid and by far the most popular rope for all running rigging applications.
LIROS Matt Plait polyester is a popular line where comfort in the hand is one of the main considerations.
LIROS Herkules is the LIROS recommended polyester upgrade.
Marlowbraid is the Marlow equivalent to Braid on Braid, mainly for avid Marlow supporters but it tends to flatten around winches so is not the most common selection.
Cruising Dyneema = Dyneema Core with Polyester Outer Jacket featuring approximately 2% - 3% stretch
LIROS Dynamic Plus is by far the most popular line for upgraded control lines featuring a Dyneema SK78 core, extra inner plait construction for maintaining a stable form under load around winches and 32plait close weave abrasion resistant polyester cover with several colour coded and full colour options. Available with the enhanced Steel Blue colour polyester Jacket.
Marlow D2 Club (Cruising Dyneema) Cover: Durable 16plait polyester Core: Reduced content 12 strand Dyneema SK75 (lower specification than SK78) blended with lower grade fibre for shape retention delivers approximately 2.5-3% stretch
Performance Sheets and Guys
Racing Dyneema = Dyneema Core with Polyester Outer Jacket delivering approximately 1%-1.5% stretch
LIROS Racer 2001 is the premium racing performance solution recommended for sheets and guys by the manufacturers, LIROS Yacht Ropes - Dyneema SK78 core with tough 32plait close weave polyester jacket.
Marlow D2 Racing is the comparable Marlow alternative to LIROS Racer 2001.
Extreme Performance Dyneema = Dyneema Core with Polyester Outer Jacket with approximately 1%
LIROS Control XTR is the ultimate line for extreme (XTR) conditions where the rigging will be pushed to the limit – SK99 Dyneema core for the lowest possible stretch and highest break load, Technora blended cover for the optimum heat and abrasion resistance.
Marlow D2 Grand Prix is the upgraded version of D2 Racing with a super prestretched Dyneema 78 core and Technora blended cover.
Dinghy Sheets
Choose your Dinghy Sheets based on desired performance in terms of stretch, weight (low water absorption) comfort in the hand and abrasion resistance.
Continuous Sheets and Lines
Ropes that are spliced into an endless loop for e.g. a furling gear control line.
Tapered Sheets
Lines that are full size where they will be handled and tapered down to the core for the section near to the clew of the sail to save weight.
The RUNNING RIGGING RESOURCE in the Jimmy Green Knowledge Centre provides more in-depth information on making the best choice for your sailing requirements.
If you need any further assistance, The Jimmy Green Rigging Team are always on hand to help. We have a wide choice of ropes but it doesn't take long to get a quote.
You can simply buy the rope cut to length or choose the appropriate Jimmy Green Professional finish so that the line is delivered to you ready to use.
We offer soft eye splice, hard eye splice, whippings and cover stripped eyes amongst many other options for use with a wide range of fittings.
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