24 January 2021 : History of winch

The major tool used by oceanographers is the rosette, which allows water to be sampled at all depths. It is a crown of PVC bottles that we send empty (and open so that they do not implode under pressure!) and we order them to be closed at the desired depths. This control is possible thanks to the cable that connects the rosette to the ship, which is “electrocarrier”. This cable is wound on a winch which is used to lower and raise the rosette. All this seems quite simple a priori. 

However, this is where the blues of “level wind” begins.

It refers to the winding of the cable on the winch drum. The idea is to unwind and rewind up to 6 km of cable on the reel more than 100 times per campaign, so that the turns line up next to each other, and above all do not cross each other (we say “do not overwind”).

This is what happens to us: every time the coil comes into contact with the walls of the reel, the cable overpatters. We then have to slow down the winch, or even stop it and go back down, then start again very slowly, which wastes a lot of time in the operations.

Today, we unwound 6 km of cable because the depth allowed it…and Martin and François worked hard, in intense contact with the manufacturer, to identify the origin of the “very small defect” (count in mm) that is the source of our problem. Climbing into the winch, crawling underneath (in the rust dust), checking it from all angles was their daily menu. After 8 hours of hard work, big progress tonight, even if we are waiting for the next stations to see more clearly… job of patience and perseverance.