I started learning about mast ram during my years of racing fireball. We call it the strut but its function is the same. It controls how much bend you want to put on the mast.
On a previous article about the mainsail I talked about the backstay which puts tension on the jibstay and bends the mast. This results in flattening the mainsail and opening the leach. Also the vang or kicker also contributes in bending the mast. Well, the mast ram is particularly effective in controlling how much the mast bends so that the kicker only effects the leach tension.
In a few words the mast ram puts more depth to the sail by straightening the mast and so bringing the draft of the main forward. That is when the horizontal lines on the main are useful as they will help you to visualise where the draft is on the sail.In my time as a federal sailing instructor in France I used to use a table tennis ball on the sail as a visual aid to the group to locate the max draft. I was doing it during a calm day with no wind by rigging a boat and pulling it to its side, resting the mast at 90 degrees on a support. I then throw the ball on the sail and let it settle where the max draft would be. And then I played with each control lines at a time to show the group how the ball and draft moves.
With the 1 meter I am still learning the “ropes”. Having sailed pretty much each weekend I have improved on “helming” and on tuning them too. I found them to be very visual. By that I mean that the boat reacts to any small change in the setup and the fact that they are relatively small you get a good overall view of the sail shape. I’ve also improved in “feeling” the boat (ie feeling how the boat reacts to a change in the setup).
So far I believe that few controls impact hugely on the boat performance. These controls are backstay, mast-ram, kicker and sheeting positions (incl. Jib slot). I think that the other control lines are more secondary for the optimum boat tuning.