erbster wrote:Interesting idea! I’ll have to try it some time, though I would not want to test the strength of the lazy jacks/main sheet as backstay in string winds; if the wind is that strong, the staysail is usually enough.
The use of topping lift/peak halyard as a backstay when running without the mainsail, probably provides more support for the mast head than the peak halyard does when the mainsail is in use
The gaff will be hard against one of the shrouds when running with the mainsail, therefore the peak halyard will also be aligned with a shroud. In this position it is providing no support for the masthead. Indeed, if you do the calculations of the horizontal components of the forces acting at the masthead (force diagram using the triangle of forces method) you will find that use of the mainsail ( with the gaff touching a shroud ) increases the resultant horizontal force at the masthead and also changes the direction of the resultant force.
If you are really concerned about forces at the masthead you could have two detachable running backstays rigged from the masthead which could be attached the the aft cleats, port or starboard as necessary.
The highest forces at the masthead will occur when on a beam to broad reach with the gaff against a shroud and lots of wind on the mainsail and the genoa full.