Automatic Mainsail Foot Tensioning

[Craic]

This super-simple mod automatically adjusts the mainsail foot tension in accordance with the mainsheet tension. I.e. the foot gets tighter when the wind is strong and you tack to upwind. Just the thing.

Why this works at all is the huge purchase you get from hooking the mainsheet not to the boom but on the horizontal foot tensioning rope.

The effect can be further improved by using Dyneema for the tensioner, and through honing the through-hole in the boom or even putting a rope wheel in there.

[Matt Newland]

Hello Claus,
This looks like a really great idea! I am racking my brains to try to figure out why it hasnt been done before... Or has it?
Does the snap shackle sheet attachment not slide up and down the outhaul rope a bit unpredictably?
Looking forward to trying it myself.

Best wishes,
Matt

[Craic]

... I am racking my brains to try to figure out why it hasnt been done before...

So do I. But I am sure it has been done before, it is so very simple and works so well. I will put it to the usual experts on the WoodenBoat forum, if they remember having seen it somewhere else before.

Does the snap shackle sheet attachment not slide up and down the outhaul rope a bit unpredictably?

Nope, it slides up and down the rope totally predictable, it automatically seeks the best point. The load onto the boom is better spread too, and if one does the harbourfurl, the mainsheet attachment slides automatically to the boom end and swivels as you turn the sail into itself.

The thing is adjustable too, through different lengths of outhaul rope you can control the foot tension.
Only thing that is really important is that you reduce the friction in the boom end through-bore by shaping it as bended as possible and filing off hard edges around the boring into a smooth radius. I myself will insert a wheel there before long.

Enjoy.

[Tony]

Hi, Clause.
This tensioner looks great idea.  I dont think it will work so well on my balanced lug, perhaps. Unlike your sprit main, it isnt self vanging.  I think its well worth a bit of experimentation, though.