In my last post about slip preparation at South Shore Yacht Club, I discussed weather challenges, dockline basics, and how to minimize the effects of changing water levels. This post discusses how I assemble my custom made docklines, keep them secure, and prevent chafe. I’m working on a few more posts in my series on docklines at SSYC, too, including:
- Fender Boards and Bow Line Hooks
- Shorthanded Docking Equipment
When I first started boating and keeping my boat in a slip at SSYC, I used docklines left over from the previous owner. They were really just sets of double braid lines intended for transient use. They were worn, difficult to splice, and a little slippery. I was eager to spend my free time actually sailing my new-to-me boat, though, so I didn’t take the time get my dock lines just right… and bad things happened, as discussed in my last post.
Having a set of custom docklines specific to my slip and boat have helped simplify docking at home. I feel my boat is more consistently secure, even early and late in the season, since I’ve spent a bunch of time improving upon my mistakes and other members’ mistakes.
When I bought my current boat I didn’t want to repeat my mistakes of the past, so I spent a solid three days setting up a custom set of dock lines as early in the season as possible. Since I’ve kept my current slip for years, subsequent dockline replacement is really only needed every few seasons. I’ve been able to do most of the replacement work at home in the winter after carefully noting which lines needed work in the fall.
Three Strand Nylon Dock Lines
Though double braid nylon dock line sold in stores looks clean, is soft on the hand, and seems to work better when making a cleat hitch, I only use it for transient docking while cruising. Three strand nylon line is much easier to splice, is generally cheaper, and stretches more when under load.
Splicing rope to a permanent length is generally better than using a knot. Using knots to secure the length of most kinds of rope actually weakens the rope, sometimes as much as 50%! Splicing results in a strength loss of far less, something like only 10%. It also looks neater, too.
Splicing three strand nylon rope is pretty easy. I learned by taking a winter class at the Milwaukee Community Sailing Center. There are also plenty of excellent YouTube videos online. I’ve used Samson rope for a lot of things, and their splicing instructions are very good. I can make an eye splice, either around a thimble or large enough to be used around a cleat, in only about 40 minutes… and I’m NOT a pro. You can also hire this out if you don’t have the time or willpower.
Some stretch in a dock line, just like in an anchor line, is generally good. Stretch allows the boat to stop and switch directions in each wave gradually over a slightly longer period of time, resulting in slightly lower peak loads (or “snap” loads) on both the dock line and the boat’s deck hardware. Imagine my 20,000 boat moving on a small wave in its slip and decelerating to a stop in four inches with stretchy rope. Now imagine my boat snapping to a stop in a fraction of an inch with something not stretchy like chain. While the amount of total “work” is the same… the boat’s motion is eventually stopped… if we stop the boat more gently with stretch we have less of a shock, or peak, load.
Stretch is not only related to the type of rope material but also its size. Stretch is usually expressed as a percentage of breaking strength. Since thicker line generally has a higher breaking strength with everything else being equal, a thick line will stretch less given the same load (or will stretch less with the same boat). So we need to find the proper size line… too thin and it’s not strong enough, too thick and it’s not stretchy enough. A good rule of thumb I’ve seen is ⅛” of line diameter per 9 feet of boat length… so my 40 foot boat uses ⅝” three strand nylon line.
Longer line also stretches more inches than shorter line, since stretch is directly proportional to length. According to its manufacturer, a short, 3 foot long, ⅝” diameter Samson three strand line theoretically stretches 2 inches when stressed to 1000 lbs., whereas a 20 foot length of the same line will stretch 13 inches at the same tension. This is partly where “spring” lines get their name… there actually is a lot of springiness to them simply because they are longer.
While stretch is generally good, it does mean getting lengths right when splicing your own lines is a little tricky. When splicing, I’ve learned to make my lines a little shorter than my measurements.
Additionally, most rope, especially three strand nylon, stretches even more when wet. So if it’s raining in a storm, or waves are splashing on your lines, they can elongate. Conversely, if docklines have been dry for a while, they may shrink and be hard to install or remove. This is especially difficult when returning to my slip after cruising for a few days or weeks… dipping the lines in the water before putting on the cleats can help with this issue.
Securing Lines to the Boat
I’ve been fortunate to have owned boats with large, solid cleats near the toerail. Owners of other boats, especially older boats, may not be so lucky. I would strongly recommend against tying to lifeline stanchions or pulpits on any but the lightest of boats, since they usually aren’t stressed for any abuse. Tying to the chainplates at the base of the shrouds might work, but this requires a knot, and chafe can be a problem. I would avoid using a windlass or rope capstan as an attachment point, since it probably isn’t as solidly mounted as it may appear. Looping an eye over a winch is a pretty solid place to attach a line, but I would hesitate to wrap a dockline in a winch using the self tailing feature due to the constant wear it will inflict on the winch.
When I first started boating, I used cleat hitches on the boat end of my dock lines. Crew would have a hard time figuring out how tight to make everything, and it was difficult to be consistent. I would spend quite a bit of time adjusting each line every time I came back from sailing, only to find it seem looser when I returned a few days later.
Then, while leaving a slip in Grand Haven, MI, I forgot to uncleat a dock line (not the only time I’ve ever done this!)… and the line slipped completely off the cleat as I backed away! After that incident I wanted a more secure way to attach a dock line, so I now use eye splices on the boat ends of my dock lines. I’ve never had issues with the eye falling off the cleat when slack, and it can’t slip out when under heavy load. Many pre-made dock lines have an eye on one end, and I’ve used these pre-made lines a few times to save time when making my dock lines.
There have been a few times I’ve used a bowline instead of an eye splice, but knots, including bowlines, generally weaken rope more than splices. Bowlines are also subject to internal chafe. I remember desperately tying my boat to a dock in a powerful storm in Frankfort, MI with a bowline around a winch. 36 hours later, after the storm had passed, the line had melted together inside the bowline, and was completely unusable.
Securing Lines to the Dock
I don’t know of any SSYC slips, other than the horseshoe or pier ends, that have any traditional cleats on the dock. Most seem to have some form of large shackle or ring to attach to. Be sure whatever you’re tying to is very solid… tying to wooden railing posts will not last long.
Merely tying a rope to a rusty dock ring (or even a shackle) can introduce chafe, especially with bigger boats during storm conditions. To prevent chafe here, I make a tight eye splice around a thimble, and pass a shackle through this thimble.
When splicing three strand line it’s sorta difficult to get the length exactly right, especially for an amateur like me. The splice tends to shorten the line at first because of how the rope is weaved into itself. Time, however, seems to lengthen the line as it is repeatedly stressed. Also, water levels change during the season and from year to year, requiring a slight adjustment to the length of many of my docklines. For these reasons, I try to make nearly all of my home docklines somewhat adjustable at the dockside attachment point.
I use a short length of mooring chain at the dock end so the line’s length can be adjusted. I use mooring chain rather than anchor chain because mooring chain has longer links, allowing an appropriately sized shackle to be attached anywhere mid chain. With anchor chain, it’s difficult to attach an appropriately sized shackle to anywhere other than the last links of the chain, making adjusting the length of each dock line a big pain.
I size my chain and shackles to be slightly stronger than the rope they will attach to. The shackles CAN unscrew themselves over time (I’m speaking from experience!), so I also lock the shackles in place with stainless steel seizing wire… plastic cable ties will work, too. (Do this with your ground tackle, as well!)
Preventing Chafe
Chafe can occur when rope rubs against anything… including other rope, shackles, pilings, cleats, fairleads, and toerails. I try to lead dock lines in a way that minimizes this contact, but this is easier said than done sometimes.
Use thimbles when connecting to a shackle to prevent chafe where the rope meets the shackle. I just switched to plastic thimbles because they are so smooth… I hope they last in UV light. Some of my metal thimbles would chew into the rope when they loosened and rotated.
For the cleat end of the boat, I use leather chafe guards on cleats that are prone to cause wear, which is nearly all of them. Despite getting some scraps of leather with the intention of making my own, I found it easier to use SeaDog Line Leather Mooring Line Chafe Kits, sold by Defender, for this application. West Marine sells a firehose version that looks really good, too. I’ve not had issues with the chafe material wearing through except in one problem location, but worn chafe kits can be replaced without replacing the entire line if problems are caught early enough.
It’s Worth It
Sure, building my own dock lines is initially a time consuming process. Once my slip is set up, though, having custom lines set up saves time when putting the boat away after a nice sail. Inexperienced crew can easily figure out how to loop an eye over a cleat… and the boat is secure, even when bad weather approaches.
However, it does mean that switching slips or getting a different boat may require redoing many or all of my lines. Transients also should never use dock lines that were intended for a different boat since the chafe points will be different… especially without the owner’s permission!
Questions for me? Go to my Contact Me page.
As I write this I have about 9 years experience as a boat owner and SSYC slip holder. I’ve learned a lot about boat ownership through the internet, and putting much of what I’ve learned back into internet content once again is one of my goals of writing My Sailing Fix. That being said, I’m not a marine professional, don’t have any marine certifications, nor am I serving in any official capacity at the yacht club, so take my advice with a grain of salt (or, perhaps, a “drop of freshwater lake?”). There are many ways to safely secure a boat in a slip. I’m just an amateur…
In my first post of this series, I talked about weather challenges, dockline basics, and minimizing the effects of changing water levels. In my next post in this series I’ll discuss fender boards and bow hooks.
Links to all posts in this series:
- Weather Challenges, Dockline Basics, and Minimizing the Effects of Changing Water Levels
- Making Custom Docklines (this post)
- Fender Boards and Bow Hooks
- Shorthanded Docking Equipment