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Rope Diameter

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Suggested diameter for mooring lines

The table below shows the guidelines for the diameters of mooring lines. Mooring ropes made of polypropylene are weaker and need therefore be thicker than the polyester or polyamide ropes. If you have a boat that is significantly heavier than average, make sure to chose a thicker diameter mooring line as well. 

Boat Length

Rope material 

Polyester and Polyamide

Polypropylene

8 m ; 26ft

10 mm

14 mm

10 m  ;  33ft

12 mm

16 mm

12 m  ;  39ft

14 mm

18 mm

14 m  ;  46ft

16mm

20 mm

16 m  ;  53ft

18 mm

22 mm

19 m  ;  62ft

20 mm

24 mm

Mooring lines 8-20 mm are delivered from stock.

 

Suggested diameter for sheets and halyards 

The guidelines for the diameter of sheets and halyards with a polyester core are shown in the table below. Yachting ropes with high-performance fibers, such as Dyneema® fibers, Vectran or Stirotex® core allow for approximately 2 mm smaller diameters. Make sure to splice your rope, because a knot reduces the strenght with approximately 50% and your rope may not have the required breaking strength in that case.

Typically the diameter of sheets and halyards has to fit in with the clutches, cleats and blocks on board. It's best to chose a rope that is 1-2 mm thinner than the maximum diameter of a block.

Check out our selection of sheets and halyards

Yacht

Length

Sheets diameter in mm

Halyards diameter in mm

Main

Genoa

Spinnaker

Main

Genoa

Spinnaker

6-8 m  ; 20-26 ft

10 mm

10 mm

10 mm

8 mm

8 mm

8 mm

9 m ; 30 ft

10 mm

12 mm

10 mm

10 mm

10 mm

8 mm

10 m ; 33 ft

12 mm

14 mm

10 mm

10 mm

10 mm

10 mm

11 m  ; 36 ft

12 mm

14 mm

12 mm

10 mm

12 mm

10 mm

12 m  ; 40 ft

12 mm

14 mm

12 mm

12 mm

12 mm

12 mm

14 m ; 46 ft

14 mm

14 mm

12 mm

12 mm

12 mm

12 mm

16 m ; 53 ft

14 mm

14 mm

14 mm

12 mm

14 mm

12 mm

18 m  ;  59 ft

14 mm

14 mm

14 mm

14 mm

14 mm

14 mm


For competitive sailors it is important to optimize the breaking load with weight savings of a rope. We are happy to work with you on that challenge!

 

Calculating breaking loads for sheets and halyards

Calculating the required breaking load is a more precise approach for determining the diameter of sheets. For most sailing yachts, the Roger Marshall's formula can be used for this purpose. Loads can vary slightly for e.g. catamarans. 

Genoasheet and halyard breaking load

The following factors are needed to use the formula and will result in a sheet load in kilogrammes: 

(A) = surface area of the sail in m2

(V) = wind speed in knots

Genoasheet load = (A) x (V)2 x 0.021 

Multiply the sheet load by 4 (safety factor ) in order to calculate the required breaking load of a rope.

For halyards the same formula can be used. Depending on the rigging of your boat, the forces can vary around 20%. This is negligible when you use a safety factor of four.

Mainsheet breaking load 

For a the main sail, two other factors need to be taken into account: at what point of the boom is the mainsheet attached and what is the purchase of the sheet. Jan-Willem Polman (author of 'Splicing Modern Ropes') has therefore enhanced the formula for the mainsheet as follows:

(X) = the distance (meters) from the boom end to the point where the mainsheet is attached

(E) = boom length (meters)

Mainsheet load = (A) x (V)2 x 0.021 x (E)/(E-X)

If the purchase on the mainsheet is four, the load on the mainsheet is divided by four. But note that the forces applied on the mainsheet travellers will stay the same!

 

Order your halyard or sheet in our webshop. Are you a regatta sailor, cruiser or dinghy sailor?

ROPE SELECTION GUIDE

Helps you select the right rope for your needs: