Which rope to choose: 10 or 12mm (3/8" or 1/2")?
Double braided polyester 3/8'' (10 mm) rope has a break strength of about 4850 lb (2200 kg). It should be enough in theory to pull the maximum output from our strongest winch (PCW5000) who offers 2200 lb (1000 kg) of pulling power but let’s consider the following:
- The knot in the end of the rope will reduce the rope strength by 30% in the best conditions. This leaves the rope with a low safety margin (4850 lb – 30% = 3395 lb) or (2200 kg – 30% = 1540 kg).
- More important is rope stretch. Polyester rope will stretch 12% at breakpoint. This means if you are using a 3/8'' (10 mm) rope at maximum winch capacity, you are about at 65% of rope capacity. This means that you will also be stretching about 60% of 15%, 9%. This means that if you have 100 feet (30 m) of rope and are trying to move a 2200 lb (1000 kg) load, you will stretch about 9 feet (2.7 m) of rope before the load starts moving. If you have 300 feet (91.5 m), that would be 27 feet (8 m)! So you end up with a great elastic band stretched up with nothing moving. If the winch stalls, you must release this tension, which can lead to dangerous situations. But it also less effective because the energy used to stretch the rope is not applied at the end of the rope for moving the load.
Why offer the 10 mm (3/8'') rope? Because some applications such as pulling a big game or a small cable don't require the full power of the winch. Since, in these applications, a long rope might be handy, the weight factor is also important! This is why we only recommend using 10 mm (3/8'') rope for small loads. 12 mm (1/2'') will also have a longer useful life because it can withstand more damage and wear before breaking.