I modified a wood lathe to provide a torture test that produces results similar to what you might see on a dock line over 2-4 years. No melting or cutting, just fine fraying.
- Oscillating motion, 3/4-inch in amplitude and 7 cycles per second. Peak speed about 1.4 feet/second, average speed about 0.9 ft/second. A little faster than docklines, but slower than other on-boat flutters.
- Variable pressure and angle. These must be moderated to control heating; we don't want to measure melting point.
- Variable surfaces. Pine end grain seems like a good choice at this time, though I will try other things. I do know, for example, that the pivot end of the rig (polished steel) causes almost zero chafe, since some of the samples ran for hours, while testing different sections.
- Today's tests are on very lightly used 1/4-inch polyester double braid (it was a fuzzy-finish line to start with). I'll be testing other things as well. I will probably focus on new 1/4-inch Sta-set and new 1/4-inch Amsteel.
There are several rope-specific coatings on the market (Spinlock's RP25 and Yales Maxijacket) claiming, among other things, to reduce line abrasion. RP25 is solvent based and soaks in, while Maxijacket is water borne and leave more surface coating, though it too soaks in deeply. Both dry over night and both stiffen the line to some extent, though Maxijacket is more severe. Thus, RP25 would be a better choice for running sections (jammers, blocks, winches), while Maxijacket is very suitable for protecting sections that won't need to flex much (splices, docklines and standing parts).
Maxijacket top, RP25 bottom. Both are far stiffer untreated line. The assertion these coatings don't interfere with splicing seems off-base. I would dunk them after splicing, which is what the riggers do.
Wear testing confirms what they claim; that these coating reduce wear by 25-50%, depending on surfaces and pressure. I need a lot more testing before I would say which I like better; each has its pluses and minuses. It is interesting that both quickly wear off the surface but yet somehow still reduce wear at deeper levels.
Top to bottom: No treatment, Spinlock RP25, Yale Maxijacket. Normal fraying on the untreated sample, and significant protection on the treated samples. 10 minutes of torture over a wooden edge, at 30 degree bend with a few ounces of pressure.
Same thing, side view. material is not so much worn away as the lines are flattened out.
I have only looked at 2 things at this point: tubular nylon webbing and PE airline tubing.
Covering moving over the wood. Same conditions, same 10 minutes.
- The nylon webbing wore about the same as the rope. The rope inside was perfect.
- The PE tubing was unaffected. The rope inside was perfect.
- The nylon webbing gets a slight crease but no wear, and the line is very slightly pollished.
- The PE tubing signifigantly frays the line, with bits of dust collecting at the ends. Not as worn as unprotected rope (about 20%).
The webbing is unchanged, while the tubing takes a toll on the line.
It seems clear that in cases where the dockline will slide back-and-forth on the dock, hose makes sense and it must be fixed to the line. The hose should be long enough that there is no bend or pressure at the tubing end. On the other hand, at the chock end where the dockline will move in-and-out, webbing that floats and is attached to the chock is a better choice. In my experience, it will last 10 years in this application, until it sun-rots and the whole line is done.
As for the coatings, there are places my docklines rub where a covering won't work; I'll be trying a coating. I'm also testing Maxijacket on my bridle apex splice (it lies on the bottom sometimes) and some sewn splices. Defender uses Maxijacket on chain-to-ropes splices, though only the first few inches (stiffening the taper would be bad). Coatings can shine places where a covering won't fit. Does the same pattern apply to Dyneema? I doubt it, so I'll be testing.
One size does not fit all. Lots to think about.