We’ve seen both turnbuckles and lashing, on matching boats nearly side by side. Why the difference in approach, since both designers are obviously comfortable with synthetic standing rigging?
Because a lashing cannot be tensioned efficiently by simply pulling on the end, turnbuckles are better for any rigging that requires substantial pretension, and where accuracy is important to rig tuning.
Lashings can be used to adjust the length or apply moderate pretension, but final tightening is better accomplished using screws of a turnbuckle. To achieve maximum shroud pretension with a lashing requires using some creative measures.
Tighten the leeward shrouds while sailing in a moderate breeze while the windward shroud is loaded up.
Attach the lashing tail to a halyard and winch it tight.
Use a temporary shroud in parallel to create the tension while you tighten the lashing.
Tie a line to the lashing tail, lead it through a turning block and back to a winch that can be used for tensioning. Then apply a string of tight half hitches to lock the lashing. This is similar to the method used on square riggers.
Another tensioning trick involves shroud tensioners. Instead of fully tightening a shroud with a turnbuckle, the shrouds are only lightly snugged. For final tensioning, the shroud is pulled aft using a block and tackle (4:1 to 8:1 purchase) with one end fixed on deck about 4-8 feet aft of the chain plate and the other end attached to the shroud about 3-4 feet off the deck. This method is common for tensioning the shrouds on folding catamarans, which need tension relieved when they are not sailing.
