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Last Updated on August 27, 2020 by Amy
While at The Boat Works, David and I had a long list of projects to tackle. One of my big ones was replacing our lifelines with fancy new Dyneema lifelines.
What is a lifeline?
Lifelines are wires or lines that run around the edges of your deck. These are designed to prevent you from falling overboard off your boat. The metal posts that the lifelines are threaded through are called stanchions.
What is Dyneema?
Dyneema is the brand name for UHMWPE (Ultra High Molecular Weight PolyEthylene fiber) made by DSM. Dyneema is incredibly valuable to have on your boat. The line can be used for a variety of purposes and is very high quality. We carry spare Dyneema in several sizes. One project I do frequently with Dyneema is making my own soft shackles.
Stainless Steel Wire v Plastic Coated SS v Dyneema Lifelines
Our Fountaine Pajot Helia 44 came with plastic coasted SS wires from the factory. There are several problems with this:
- Over time the plastic coating develops a sticky residue on it. Not detrimental to our safety, but gross nonetheless.
- The plastic coating breaks.
- UV damage shortens the life of your lifeline due to damage to the plastic.
- The plastic coating hides damage to the stainless steel wires.
Benefits to Dyneema lifelines:
- Stronger than stainless steel (15x stronger).
- Lighter than stainless steel (7x lighter).
- Easier to install.
- Chafe resistant compared to other fibers.
- Easier to cut in an emergency MOB situation.
We met a new Outremer last year that came from the factory with Dyneema lifelines.
Not sold on Dyneema? The Boat Galley has a post on new stainless steel wire lifeline installation.
Supplies to Replace Your Lifelines
This is what I used on our 44′ catamaran to make our Dyneema lifelines. You may need different sizes or quantities depending on your boat.
- Thick 12 strand single braid Dyneema for your main lifelines (I used 6 mm thick and approximately 65 meters long)*
- Thin Dyneema for your lashings (I used 3 mm thick and 9 meters long)
- M8 Stainless Steel 316 Eye Bolts, Marine Grade, 4 each
- M8 Stainless Steel 316 Eye Nuts, Marine Grade, 4 each
- swivel snap shackle 70 mm, 4 each
- Fid set
- electricians tape
- measuring tape (I use a seamstress measuring tape because of how flexible it is)
- box cutter
Dyneema is available from your local chandlery. We recommend going with the silver, natural colored Dyneema because we have used some dyed Dyneema in the past, but find that the color leeches off.
Cost for Making Your Own Dyneema Lifelines
The first 5 items on the above list totaled to $486.35 USD.
Splicing Your Lifelines
I created my Dyneema lifelines using a Brummel splice. When you have two loose ends, the splice is fairly easy. However, when one end is occupied (as it will be when you make your lifelines) you need a modified or Mobius Brummel to get the job done. Once you figure the splice out, it’s fairly easy.
There’s a Modified Brummel Splice video on YouTube, but I found it not as easy to follow as the above link is. What tripped me up is that the person in the video switches sides partway through. When you put the loop through the hole, it needs to follow through the hole in the same direction that the tail went in the previous move. This is the “modified” part that allows you to make the Brummel with a secured end. Pushing the loop through should untwist the loop instead of putting a double twist in the line.
Do one end of the lifeline, and then thread the tail end through the stanchions. Connect the 1st, already sliced end properly to the railing, and then work out your measurements for the 2nd end. Disconnect the first end to give yourself some additional room to bury the tail of your 2nd splice.
Measuring the big Dyneema to splice the exact right length is really hard. Don’t worry, it’s better to be too short than too long. The distance will be made up with the lashings.
*Depending on the size of your shorter sections, you may need to drop down to a smaller size. The gates on the stern of our boat are so small that the long tail bury would overlap. Since the long tail is 72x the diameter, you have to either drop the diameter down or drop the tail (Evan Starzinger recommends at least 63x the diameter).
While Dyneema has negligible stretch, it will have some twist in the line since it has been coiled. Monitor your new Dyneema lifelines. As they adjust over the next few days they will work out the twist, but your eye bolts and nuts will need to be screwed back in and your lashings re-tensioned.
DO NOT use a hot knife. You don’t want the ends of the Dyneema melted, as it makes sharp edges in the long tail bury. I wrapped the Dyneema in the tape and cut through the tape using the box cutter.
Our chandlery only had eye bolts that were too long, so David cut them down using our Dremel.
Inspect the eyes of your stanchions. Our stanchion eyes are a smooth tube with rounded, gentle edges. Older or damaged stanchions might cause chafe problems on the Dyneema, so replace your stanchions or use a plastic protective covering at the stanchions. See the second post link from Rigging Doctor below.
Finished Dyneema Lifelines
Evan Starzinger has a very technical article out about the benefits of Dyneema lifelines.
Ronstan asks Is Synthetic Rope Really 15 Times Stronger Than Steel Cables?
Dyneema’s abrasion resistance explained.
WHY CHOOSE DYNEEMA ROPE VS STEEL WIRE ROPE FOR HEAVY-DUTY RIGGING? from USA Rope & Recovery