[JohnRPollard]

Jim,

Re: Running backstays

Once you get beyond the dinghy/daysailer size range, most fractional rigs will have a conventional backstay. On performance oriented-designs that are more aggressively fractional (say 3/4 or 4/5), the backstay will usually be very lightweight and is used primarily for adding or reducing mast-bend. In these cases, the primary support for the mast will come from running backstays (sometimes called check-stays and by other names).

The runners are attached on both sides of the mast (port and starboard) at the same height where the fractional forestay attaches to the mast. The runners counteract the force applied by the forestay, just as a conventional backstay would counteract the force applied to the mast head by a conventional headstay. If the forestay was not balanced by the runners, it would bend and pump the mast as it became loaded up in strong winds.

Since the runners are attached on both sides of the mast, and lead from there to the stern of the boat, you can see how they could interfere with the mainsail. So only one can be used at a time -- the windward one. The leeward one, the "lazy runner", is eased to slack so it won't interfere with the mainsail. When tacking or jibing the runners must be switched by easing the working runner and taking up on the lazy runner until their roles are reversed -- in much the same way as we swap jib/genoa sheets.

Like I said, most cruising oriented fractional rigs, and even many performance oriented rigs, dispense with running backstays by using a less fractional rig with a swept spreader and shroud geometry that adequately counters the forestay. Also, fractional boats aren't the only ones that use runner/check stays. Many mast-head, cutter-rigged cruising boats use runners when flying their staysails in heavy going. Hope this helps some.