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What line should I use for the mainsheet?

2018 April 1

Dear Boat Doctor,

I recently bought a Passport 47, and it’s in really good shape but a bit of the running rigging is tired. I need to replace the mainsheet and I have questions on the running backstays. First off, what type of line should I use for the mainsheet? It is just regular double braid now and the guy at the chandlery suggested Dyneema, so I am not sure what to use. Second, the boat has running backstays, do I need to use those all the time? They are made of wire and hard to handle, they tend to rub on my nice new mainsail too. Can you shed some light on this?

John Peterson

Beaufort, North Carolina

Dear John,

Running rigging is the transmission mechanism for energy from the sails to your boat. You want that energy to transfer to the boat, not be absorbed and spent stretching the rigging. On the other hand, it has to handle well and be affordable. With line, basically the more you spend, the less elasticity you get, and in running rigging elasticity is almost always bad. But the level of inelasticity required is a direct function of the loaded length of the rigging. A halyard, being long, needs to be very inelastic, a mainsheet, being relatively short, can handle a bit of elasticity.

With all that said, I’d recommend a Dacron single braid like New England Ropes Regatta Braid (www.neropes.com) for your mainsheet. It is inelastic enough for the application and is very nice to handle.

On your boat the running backs are only used to stabilize the mast when you are flying the staysail. You will setup the weather running back to oppose the force that the staysail is imparting on the mast, the staysail wants to pull the mast forward and to leeward, the runner pulls the mast aft and to weather. You certainly can set the running anytime you like, but it is only required when you fly your staysail.

I totally agree with your assessment of wire runners, they are heavy, hard to stow and the lazy one chafes the main. There is a better way! We need to revisit that elasticity discussion above, we have long loaded length and we need very low elasticity, meaning we need a high-tech line that is going to cost a little bit. I think heat-treated Dyneema is a great material for runners, Dyneema itself is very low stretch and the heat treating makes it even better. The material is very light and won’t chafe the main, a big win. Take a look at Hampidjan’s Dynex Dux or New England Ropes STS-HSR; either would work well.