Hot Knives

The Jimmy Green Rigging Team has assembled a selection of options for cutting and heat sealing all your Polyester, Nylon (Polyamide), Polypropylene, and Polyethylene ropes.

These rope fibres have relatively low melting points and have distinctive reactions to the application of a hot knife cutter or hot flame:

• Polyester melts in a controlled, workable manner and gives off a relatively sweet aroma (approximate melting point 260 °C)
• Nylon tends to go black when it burns and emits an unpleasant ammoniacal odour that will get up your nose (approximate melting point 215 °C)
• Polypropylene melts at a lower temperature than nylon or polyester (approximate melting point 170 °C). Burning creates a smoky acrid stench, and the strands will frizzle away to nothing if you are not careful. 

Please note it isn't possible to cut or melt the ends of some ropes successfully.

This list is not exhaustive, but indicative of ropes that you may encounter in yacht rigging that will not heat-seal:

• Natural fibre ropes, e.g. Hemp, Sisal, Manilla, and Coir
• Synthetic fibre ropes which contain Ultra-high-molecular-weight polyethylene = UHMWPE (trade name Dyneema), Aramid (trade names Kevlar and Technora), or Vectran = Liquid-Crystal Polymer

Any attempt at using a hot knife to cut these ropes will likely result in you making a mess.

Why use a Hot Knife Rope Cutter?

You can cut most ropes with a sharp knife or scissors, but it is advisable to secure the strands or plaits first with tightly wound tape, e.g. self-amalgamating, insulation, or sellotape.

The advantage of using heat is that the blade melts and fuses the strands as it passes through the rope to make two separate, temporarily sealed ends. This will keep the integrity of the different strands or plaits intact long enough for you to apply a whipping, heat-shrink, more secure heat sealing, or any other more permanent binding option of your choice, e.g. tape. 

Once the end is secured by the melting or taping method, you can apply more heat to melt and mould it into a neat, heat-sealed finish. This can be achieved with the flat surface of the hot knife or with a flame and cautious fingers and thumbs. A good tip is to lick the skin you will expose to the molten rope, but this won't be enough to prevent a burn if you are too hasty. The trick is to time it so that the rope is still malleable but cool enough not to burn you.

The Different Tools you can select for Heat Sealing Rope.

The options are:

Electric Hot Knife - HSGM is the original German-made model used by professionals - Bainbridge provides a copy at a more realistic cost for occasional DIY use - Marlow supply a cordless option with a rechargeable battery

Gas Hot Knife or Solder Set - the Meridian Zero range offers rope cutting, sealing, and soldering options powered by butane (lighter fluid)

Turbo Lighter Flames - these are butane-fuelled lighters with super-enhanced hot flames

Cigarette Lighters - a humble disposable or refillable butane lighter can deliver a reasonable heat-sealing finish with the flame turned up. It is best to find a sheltered location because even a gentle breeze can make the job very frustrating - Lighters are ideal for melting the ends of whipping twines or other small-diameter cords.