Another search term came in – mainsheet length, mirror dinghy centre main.
There are two ways of setting up a main sheet in a dinghy. Most modern boats have a central mainsheet:
This arrangement requires four pulleys because one loses the leverage of a boom-end mainsheet. The Mirror mainsheet is very simple. It is tied to one side of the boat’s transom, runs through a single pulley at the end of the boom and through a pulley on the other side of the transom. It is simple and sensitive, and I much prefer boom-end mainsheets. I developed this preference sailing the Laser dinghy and compared the leverage and control I had with the rope-burn and heaving you have with centre sheeting.
In my boat, after the pulley on the transom, I then run the sheet through a centre pulley just aft of the centreboard. This avoids the mainsheet interfering with the tiller when tacking and gybing. The other advantage of pulling the mainsheet upwards is that when I am hiking for close hauling, I have both the tiller stick and the mainsheet to hold on to, so as not to put all the effort into my tummy muscles. The disadvantage is that the rope running from the transom to the centre block can cause rope burn to the feet and shins, and they take a long time to heal. I have to get my legs over the rope so as not to touch it as it runs.
The length of my mainsheet is 7 metres or 23 feet.
Here are two boom-end mainsheet rigs. Both are sensitive and comfortable. The first is the traditional Mirror rig.
This one is inspired by that of the Laser. It has an independent traveller rope. Using the traveller enables you to get the mainsail into interesting shapes for better efficiency. On bigger boats, the traveller pulley can be locked in any position. In this photo, the Laser influence goes much further, in the possibility of tightening the traveller rope with a pulley system and a cleat. It is a neat setup.