Bob Shirley posted a harrowing story on a sailing anarchy forum:
You have to go through a pile of posts, this one is dated June 13, 2020. The short of it is this: while sailing rather far offshore at Ventura, on a fast downwind ride he moved out to the “back porch”, the stern end of the vaka (main hull) right next to the rudder. Unfortunately, he fell off the back end. He had his tether on, or he’d have been dead, several miles offshore alone in the water represents very poor odds indeed; the Weta would have just kept going without him. He could reach the aft crossbar but was unable to pull himself back into the boat or cause it to do anything but keep blasting downwind. He was dragged at least an hour, the GPS estimated 5 miles of misery before coming to the beach.
The standard tether padeye is placed roughly halfway astern in the bottom of the vaka, it works just fine for putting your rear end out on the ama, although you may need to fine tune your tether length to get what you want. As Bob’s experience points out, it is very poorly placed if you go out on the back end. The solution to this was pioneered by Jonathan Weston (aka Donuts) to my knowledge, others may have also done this. He placed a padeye just behind the daggerboard trunk. This post details how I did this procedure. In honor of Bob’s mishap, I am calling it the “Anti-Bobsledding fixture,” you can call it whatever you like.
· Haas Stainless Steel One Way Folding Pad Eye, Part No.: 51637006, available from E-rigging for less than $6.
· Stainless bolts: I chose flathead socket screws, ¼-20, 1 in long. Torx heads would be better if you can find them, I don’t prefer Phillips, they strip too easily.
· I used 3M 4200 sealant. It’s expensive, and has a strong tendency to sure in the tube, but it works really well. Use bathtub caulk if you want, but I don’t use that stuff for jobs like this, the risk of water incursion into the foam core is unattractive.
· I used canvas phenolic sheet (aka Micarta, gets used in knife handles among other things) as a backing plate. I had some lying around and didn’t want to fiddle with individual nuts and washers in a place that’s a blind, difficult reach. The backing plate also spreads the load over a wider area, it’s safer for the hull. It’s available from multiple suppliers online. It won’t corrode, and the screws won’t seize to in, it’s quite strong, cuts, drills, taps and files easily. You can use washers and nuts if you like, that’s what Donuts did. I wouldn’t recommend carbon fiber composite, it’s not likely to tap as well, it’s more expensive, the weight issue is minimal, and the Micarta is more than strong enough. I used 3/8” thick sheet, approximately 2 x 2.5 in. The thicker material means more screw threads and a better hold.
· Harness and tether if you don’t have one. I use the West Marine harness, it’s better than the original one supplied by Weta, some like the Spinlock, it’s more expensive. You can make a tether, having an elastic core (bungee cord) is really helpful.
1. Locate the target location on your boat. My hull is #374, an old boat. Your may be somewhat different. With the inspection hatch open, feel the territory around the daggerboard trunk. It’s foam core construction, which stops about 3 inches aft of the daggerboard trunk. There’s a bulkhead just aft of that, I never knew it was there, but it is. These factors mean placement is quite important, the foam core section is stronger than single layer, so I wanted to place on that, and not at the very edge. The foam core region is approximately outlined on the picture at right by the pink box. The padeye is shown in place, just below the rear or the daggerboard trunk (the trunk walls are also foam core, you have to allow for that). It’s a long reach, not a huge strain, but I’m tall. If you want to get a good look at things, place a bright light inside the inspection hole at night, the hull is translucent enough to show you the big picture.
2. The Micarta was cut to size and the padeye placed on it with double stick tape to get a good transfer of the hole positions. A drill press is not absolutely essential, but it does help. I used a very shallow cut with the ¼ inch drill to spot the holes, then drilled with a small diameter drill, followed by a #7 drill, the proper size for a ¼-20 tap.
3. Tapping the holes nice and straight helps things to play nice; an old machinist trick is to start the tap chucked into the drill press, turning the chuck by hand (NOT with the motor!). Once it’s well started, finish tapping the holes with a normal tap wrench.
4. Transfer the hole pattern to the place you have spotted on the hull, photo Mr. Double Stick Tape can help out here too. I used a 3/16” drill, slightly smaller than the #7, followed by 17/64”; the final holes must be a bit wider than ¼” if you are going to seat three screws (depending on how accurately you drilled, you may need larger holes).
You can see the foam core a bit here:
5. Test placing the screws. I had to file my backing plate considerably to get it to fit around the daggerboard trunk
Once you are confident it will all fit, add sealant to the parts as shown, including the screw threads close to the head before final assembly. Don’t forget the padeye ring!
6. The final placement with tether attached is shown below. You may need a slight extension on your tether. The length of blue dyneema has eyes spliced at both ends, and is set up so that the tether length can be fine adjusted. This is not the stock tether, I replaced it some years back when the original bungee wore out, using 3/8” bungee cord, 1” tubular nylon webbing, re-used the original snap swivel and hand-stitched the booger together. I haven’t taken it out yet to adjust the length.
Bruce Fleming advised I fill in the screw sockets once installed with some caulking, otherwise water will forever pool in those little cavities and bring on rust, I’ve done so but it’s not shown. I did not use the 3M sealant for that; now is the time for the bathtub caulk, easily removable. BTW, I’m hoping I tangle my feet less in the tether now that it’s not directly underfoot.
After you finish a job, ever get that sudden flash, "Dang, I could have made that so much simpler!" Here's how to do this without all that heavy duty geek stuff.
Instead of Micarta, use plexiglass (aka acrylic or polymethylmethacrylate) or Lexan (polycarbonate) in 1/16 to 1/8" thickness (1.5-3 mm). You can find that at your local building supply. I still think the backing plate is a good idea for spreading the load wider than washers will.
Use smaller diameter screws than 1/4" (6mm) with either nylon lock nuts or thread locking compound such as Locktite so they don't wiggle loose in use. This allows wiggle room with the padeye. Keep it stainless, and 1" long. Drill oversized clear holes so that assembly isn't so fussy. You can stick washers on the back of the plastic with doublestick tape if you don't want to snug the nuts down on the plastic directly. Trying to place washers, then nuts in a blind location where they will fall off is not much fun. Use a socket wrench or place some masking tape across the backside of a box end wrench to prevent the nut from falling while you're wiggling around trying to start the screw into the nut.
I'd still recommend some sort of sealant.