At some point Michael Jefferson will chime in with his idea about Aiders, which are essentially nylon webbing ladders used by climbers.
To save him the trouble, I have pasted his post from the LongPac 2015 "Jacklines and tethers" thread below.
I have adapted his idea slightly for myself... rather than clip a bundle to my harness I have 4 that I install at the base of my 2 farthest aft stanchions port and starboard.
this places them, on Domino, just forward of the cockpit and slightly aft of midships.
I use double sided velcro to bundle them at the base of the stanchions which seems to hold them securely but is still easy to tug the aider free.
DH
OK, here is Michael's OP:
There is a practical approach to getting back aboard after a tethered fall. I have carried for years a nylon stepladder, made by sewing steps in a long loop of thin 1" nylon webbing, folded up and secured with a few rubber bands. It is attached to my clip in point on my harness by a stainless offset carabiner, and has a short tail to pull to unpack it. When unpacked, it is about 5 feet long and has 5 steps. If one were dangling from the tether, hopefully one might get a hand on the toerail. If not, your tether is too long! If one were to clip the (offset Eye "genius" ) carabiner over the toerail, and then pull the tail, one would have a fighting chance to get back aboard. By getting a foot into the highest loop that is practical, one could stand up, with ones weight on the ladder, and grab the lifelines. This way, the legs are being used to lift, not the arms. Climbers have used similar ladders, called "aiders" for many, many years to help in climbing things which are too difficult or steep for ascent by grabbing holds and pulling. A company called "Mountain Tools" has a selection of aiders. REI has them. Search in "climbing/webbing and cords/etriers. Item # 889775
For bundling into a compact assembly suitable for clipping to the harness, I recommend the "alpine" versions of the aiders. Yates, Black Diamond, and others make good versions. They are also known as etriers.
Here are some links. Some of the pictures do not show the full length of the aider. 5 step aiders are about right. Price is about $22.
http://www.mtntools.com/cat/rclimb/a...lpineaider.htm
http://www.rei.com/product/889775/bl...cm_mmc:cse_PLA
West Marine sells three versions of the "genius" carabiner. The 3 1/8" version is part number 317057. The 4" version is part number 317065.
Here is a link:
http://www.westmarine.com/buy/west-m...02_060_002_003 Price is $30 to $40. Make sure it is big enough to get over your toerail.
The last thing to do is to seize the loop on the aider to the carabiner with some light line or heavy whipping line. This is so that there is no chance that the aider will shift around. You want the aider carabiner loop in the bottom (narrow) part of the carabiner. Also tie a short piece of parachute cord to the last step, and consider a small line stopper ball, such as west marine # 9201328 to allow a something to grab.
There are no guarantees, of course. If you go overboard singlehanded on a tether, it will be a heroic fight to get back aboard, but as others have discussed above, the odds using only your arms are small. If you can get a foot in an aider attached to the toerail, they improve dramatically.
Best wishes,
Michael