Slightly larger boat but hopefully still relevant. I also single hand most of the time and had my jack lines on the side decks until a couple years ago when I began to doubt whether I would actually be able to get back onto the deck from a position dangling over the side on a tether.
My new centerline configuration runs from a pad eye just forward of the cabintop traveler to the mast where it wraps the mast once, then up to the foredeck spinnaker ring (Flying a spinnaker solo is not for me, so it’s otherwise unused.) and then off to the starboard bow cleat. It’s a standard 30 foot jack line previously used on the side deck and I just coil and sto the excess line in the adjacent anchor locker.
The pad eye is through-bolted to the sea hood over the companionway slider with a ¼" G10 high density fiberglass backer plate. The hood was originally held down by eight wood screws which I would absolutely not trust alone for this use. The bigger modification here is that the hood is also through bolted to my traveler track with about six bolts and the ends of the traveler track are through bolted to the cabintop. So the sea hood is quite secure.
I’m at my most vulnerable moving from cockpit to side deck or cabintop where I can’t be clipped in without the side deck jack lines. For that move, my dodger has hand rails on each side so I can clip on to the jack line with one hand while holding on to the dodger hand rail with the other.
My primary use of the center jack line is when I’m up on the cabintop handling the main sail halyard, sail ties, flaking the main in the lazy jacks, reefing, etc. It was getting tossed from the cabintop to the side deck three years ago by a powerboat wake I didn’t see coming that finally convinced me a centerline jack line is the way to keep myself on the boat rather than hanging off the side.
With a furling genoa, I’ve never made use of the jack line on the foredeck, but could if I needed to. The jack line is tight to the front of the foreword hatch and forward end of the cabintop up there, so a tether clip will cause some marks, but I’m not concerned about that in a blow when safety is more important.
Attached are a few photos. None were specifically taken of the center jack line, so they’re a bit incomplete, but better than nothing and hopefully will clarify if some of my American terminology doesn’t make sense in the UK.
