Polypropylene rope - floats or nope?

Jul 2, 2019
102
Hunter 310 Pine Beach, NJ
Want to buy a coil in case I need tow rope. Chose PP because all accounts say it floats. Shopping around and more than one company is selling this stuff as anchor rode. Floating anchor rode??? What gives? Do people want anchor rope that floats or are these companies clueless? Or... is there a type of PP that actually sinks? I just want to go sailing and this is giving me a headache.
 
Apr 8, 2010
1,942
Ericson Yachts Olson 34 28400 Portland OR
For decades I have noticed recreational (smaller) fishing boats using poly line for everything, including anchoring.
:)

They seem to like it because it's sooooo inexpensive. While it does have its uses, just store it away from exposure to UV, which can degrade it.
For anchoring, best stick to 3 strand nylon.
 
Oct 22, 2014
20,989
CAL 35 Cruiser #21 moored EVERETT WA
I just want to go sailing and this is giving me a headache.
It is a decent tow rope. It will float keeping it above your prop when the thing being towed comes rushing up to the stern.

It will deteriorate in the sunshine as it is vulnerable to UV light.

The headache is just boat fever.
 
Feb 21, 2013
4,638
Hunter 46 Point Richmond, CA
Propylene rope floats and repels water because of three reasons:

1. Lower surface tension vs. water causes it to be water repellent or hydroscopic.

- polypropylene: 29 dynes / cm2
- fresh water: 72 dynes / cm2
- salt water: 60-65 dynes / cm2

2. Lower specific gravity vs. fresh and salt water means that polypropylene is lighter and will float.

- polypropylene: specific gravity of 0.9
- water: specific gravity of 1
- sea water: specific gravity of > 1

3. The amount of air between the fibers allows air to be trapped between the fibers results in buoyancy. The fiber packing is so dense that the surface energy of the sorbent will not allow water to replace the air that naturally exists between the fibers, thus the sorbent will not become water-logged. The net result is that an oil sorbent will float indefinitely.

The only thing that may cause polypropylene to float lower than the water line is the presence of a contaminant such as a surfactant or emulsifier in the water. Such contaminants might include soap, detergent, alcohol or chemical dispersant. The presence of these surfactant materials would cause the oil to be at least partially soluble in the surrounding water and would change the surface energy enough to allow water to penetrate between the fibers. The polypropylene will not sink (as to the bottom) but it can hold some water in the presence of the surfactants.

That is why it is the rope of choice for water skiing, wake boarding and tubing. Like jssailem said "the headache is just boat fever." Buy a coil of HIGH BREAKING STRENGTH polypropylene tow rope, stow it and go sailing!!
 
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Jan 19, 2010
12,362
Hobie 16 & Rhodes 22 Skeeter Charleston
2. Lower specific gravity vs. fresh and salt water means that polypropylene is lighter and will float.
What weighs more... a pound of feathers or a pound of lead?:biggrin:
(snip) The only thing that may cause polypropylene to float lower than the water line is the presence of a contaminant such as a surfactant or emulsifier in the water.
Or a big-ass anchor attached to the end...:biggrin:
 
Feb 8, 2014
1,300
Columbia 36 Muskegon
You can get black poly. Still degrades in the sun but much slower. White poly is the worst, the sun shines right through it so it degrades all the way through all at once. The lines on life rings are usually black poly.
 
Jul 27, 2011
4,988
Bavaria 38E Alamitos Bay
One of desirable features of nylon anchor rode is its stretchability, so I don’t see how polypropylene rode of low stretch could be more suitable. Poly is hard on the hands compared to nylon and it does not stow as well, not being soft. Also does not hold a horn cleat as tightly as nylon. I note, however, that poly is used in mooring ball pennants extensively, likely because it does not absorb and hold water as does nylon, so it’s not so messy-wet or water heavy as the nylon would be.

Yes it floats, so makes for a good tow rope for the dink. Largely because it won’t get under the boat and foul the prop if you forget to take in the tow line when needing to back down with a dink in tow. I don’t know the frequency of the maneuver generally, but being able to back with the dinghy astern in tow is a regular one for us. Also, if the dink is drifting around the yacht at night the tow line also cannot sag and find its way around the rudder a couple of times, etc.
 
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