If you really cannot wait for calmer weather or even until moored safely alongside, this is how to climb the mast while sailing.

Of all the things I have encountered over my sailing career, climbing a mast at sea is one of the top five to get my heart racing. Any motion felt on deck is amplified the higher you go, leaving the climber not only to contend with the height but being flung around like a rag doll with every roll of the boat.

If there is any option not to climb the mast while at sea then take it – get to a port of refuge or at least some sheltered waters to anchor before going aloft. If the problem must be solved while at sea then ask yourself whether you could wait until conditions are light. The rougher the seas the greater the risk when going aloft.

When planning for long offshore or ocean passages, put together a dedicated mast climbing kit, then practise your procedure on the dock and in sheltered waters to make the live exercise a lot less daunting. Invest in a good quality climbing harness, big enough to fit over layers of foul weather gear, and a lightweight helmet – it is a good idea to remove helmet ear flaps for better communication.

Wear plenty of clothing to avoid bruising from harness straps and knocks against the mast and rigging or wear body armour as seen in our buyers guide below.

Before climbing a mast at sea think about the job you need to perform and gather together the tools you will need in a bag that can be closed while you are climbing but opened with one hand while aloft. I use a small drybag with a Velcro mouth but there are alternatives.

Having duplicate halyards is wise for any offshore yacht, and ideally use a spare main halyard to make this climb. If your boat uses a topping lift, then check that the breaking load is suitable for it to be used in this way.

If you have a double sheave box at the top of the mast but do not want a permanently rigged second halyard then rig a mousing line instead and carry a spare halyard. If this is not possible, then masthead spinnaker or jib halyards can be flipped over the shrouds and used in the same way.

Fractional halyards are less suitable for this type of climb.

Using a safety halyard is advisable but not always practical or possible. If it is vital you climb and a safety line is not available, then it is essential the person winching is experienced and has practiced with you a controlled decent from the mast under sail.

The primary danger is losing hold of the rig and swinging freely, which can lead to injury from high speed collisions with the mast.

My preferred method for preventing that is to climb abaft the mast with the boat heeled moderately. This reduces rolling and the mainsail offers a solid surface for a climber to lean against. I set the boat up with mainsail alone sailing at around 60° TWA, adjusting the traveller and sheet to ensure the boat does not round up.

Climbing harness and kit bag.

Prussik climbing knot.

Even for those adept at mast climbing in port, it can take a great deal of strength to climb a mast at sea just to stay connected to the mast. Generally the crew will resort to winching while the climber uses their arms and legs to keep aft of the mast, leaning into the mainsail, pushing up off the top of windward mast steps or even batten cars.

Swap grinders regularly if you are able and always ensure the person tailing the winch is looking up. Once in position to work the climber should use short strops to tether themselves next to the mast to reduce the risk of swinging around while working.

The descent can actually be a lot scarier for the climber than the ascent: handholds are beneath your line of sight and as the halyard lengthens the potential to swing is greater.

A good descent is smooth and at just the right speed. The cockpit crew should stand as far back from the winch as possible looking up; spare crew should ensure the halyard is free to run out and also stand by the jammer in case of problems.

Beware of spreaders, running backstays or radar brackets where the climber may need a bit more time to manoeuvre their legs and arms over an obstacle, and communicate constantly about the speed of the decent.

Climbing a mast at sea : the essential gear

Harnesses and Bosun’s Chairs

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DMM Vixen Women’s Climbing Harness


DMM vixen womens harness - climbing a mast

This is the harness I used in the video. It is designed for women. I’ve used it for about 8 years and it is still in great condition. It comes in sizes XS to L. I bought the L to fit over my foulies or larger clothes, but it is a little big when wearing just light form fitting clothes. Ideally I would get a smaller sized harness for that purpose.

  • 5 gear loops
  • breathable
  • 345g (xs) – 410g (large)


Buy DMM Vixen from GoOutdoors.co.uk

Petzl Aquila Men’s Climbing Harness


Petzl Aquila mens harness - climbing a mast


Maximum comfort for long suspensions and for larger body types.  The wide, comfortable waistbelt is ideal for all body types and adjustable leg loops adapt to clothing for climbing in any season.

  • 2 slots for caritool holder
  • 4 gear loops
  • 320g (xs) – 425g (xl)

£95.65  /  $134.95

Buy Petzl Aquila harness from AlpineTrek.co.uk

Buy Petzl Aquila harness from Amazon.com


Petzl Ascension Ascender

petzl ascension ascender left and right hand models best mast climbing gear

This is the ascender I use on my own climbing gear. I use a left handed version because I am right hand dominant and it’s easier for me to slide the ascender up with my left hand while pulling up on the lazy line with my right hand.

  • line size: 8mm – 13mm
  • 165g
  • left or right handed versions

petzl ascension ascender detail of jaw

£46.76  /  $87.07

Buy Petzl Ascension left handed from GoOutdoors.co.uk

Buy Petzl Ascension left or right from AlpineTrek.co.uk

Buy Petzl Ascension from Amazon.com

Belay Devices

Petzl Gri Gri +

Petzl Gri Gri + climbing a mast best mast climbing gear

This belay device can be used with all single ropes (optimised for 8.9 to 10.5 mm diameter ropes) and is equipped with an assisted breaking function. Suitable for beginner mast climbers to expert riggers.

  • line size: 8.9mm – 10.5mm
  • 200g
  • auto-locking

£90.86 /  $129.95

Buy GriGriplus from Decathlon

Buy GriGriplus from AlpineTrek

Buy GriGriplus from Amazon.com


Grivel Mega K6N Screw Lock Snap Hook

Grivel Mega K6N Screw Lock Snap Hook climbing a mast

For belaying and rappelling. It is designed for use with both single and double ropes.

I use two of these in my solo mast climb gear. One is used from the bottom of the ascender to hold the footloop and personal lanyard and the other is used on the top of the ascender to work as a reduction turning point for the belay lazy line.

  • 7000-series aluminum
  • Screwgate
  • 78g


Buy Grivel K4n Carabiner from Trek Inn

Black Diamond Gridlock Screwgate Carabiner

Black Diamond Gridlock Screwgate Carabiner climbing a mast

Designed specifically for belaying, the GridLock isolates the belay loop behind its uniquely shaped gate, thereby keeping the carabiner in its proper orientation.

I use two of these carabiners, both from my harness. The anti-crossloading design is reassuring as the repeated loading and unloading of both the belay and ascender has a tendency to make standard carabiners rotate and there’s a high risk of crossloading when solo rappelling.

  • Anti cross load design
  • 76g


Buy Black Diamond Gridlock from GoOutdoors.co.uk

DMM – Rhino Quicklock – Locking carabiner

DMM - Rhino Quicklock - Locking carabiner climbing a mast best mast climbing gear

For regular users of pulleys or GriGri like belay devices.

I use this carabiner on my prusik line. The horn stops the hitched on line sliding around the carabiner as it is repeatedly adjusted.

  • Anti cross load horn
  • Quicklock gate
  • 81g


Buy DMM Rhino from Alpine Trek.co.uk

Slings and quickdraws

DMM Dyneema sling

DMM Dyneema sling best mast climbing gear

Dyneema has several advantages over traditional nylon webbing – it’s incredibly light and strong, less susceptible to UV degradation and is more abrasion resistant.
I use this sling as my personal lanyard between harness carabiner and the ascender. You need to find a sling that can be adjusted to your own personal reach length. I double this one over to give me the correct length.

  • 11mm Dyneema tape
  • 120cm
  • Strength: 22kN


Buy DMM Dyneema sling from GOOutdoors.co.uk

Helmets and Body armour

Edelrid climbing helmet

Edelrid climbing helmet

Wing-Fit system and rear adjustment dial fits all sizes. The cradle folds into the helmet to reduce stowage size.

  • 359g
  • headlamp mount
  • 54cm – 62cm head size


Buy Edelrid climbing helmet from Decathlon

Eclipse women’s climbing helmet

Eclipse women's climbing helmet

Ventilated and lightweight for smaller heads, this has a washable padded liner too. Handy headlamp clips could be useful for climbing in the dark.

  • 280g
  • headlamp mount
  • quick adjust dial


Buy Eclipse Women’s climbing helmet from AlpineTrek.co.uk

Pro Tec BMX helmet


Pro Tec BMX helmet

You don’t have to have tons of dedicated single purpose kit on your boat, a BMX or other hardshell cycling helmet will do just as well. If you’re carrying a hardshell helmet to use with your own bike then use that for climbing a mast! (just beware of standard polystyrene cycling helmets and their fragility, one headlong smash into your mast and you should consider a regular polystyrene cycling helmet dead and must be replaced. Use a hardshell helmet that is designed for light knocks and bumps. I know some friends who sail with ski helmets because their boom is so low. A ski helmet would also be a good alternative.

  • Polycarbonate Shell
  • 5 sizes: xsmall – xlarge


Buy Pro Tec BMX helmet from Source BMX

Forcefield Ex-K Harness Flite Plus Body Armour

Forcefield Ex-K Harness Flite Plus Body Armour

A premium brand motorcycle armour designed to be worn over a baselayer and under a jacket, this armour is robust and easy to don. Whilst I haven’t tested this particular body armour model, I have used Forcefield body armour integrated within my motorbike kit and it is really good stuff, comfortable and relatively easy to move in. This would suit the larger body clanging about up a mast at sea.

  • designed to be flexible
  • breathable
  • CE Level 2 back and chest protection

from £277

Buy Forcefield Body Armour from Amazon.co.uk

O’Neal Underdog protector jacket

O'Neal Underdog protector jacket

A mesh jacket with strategically placed foam padding and moulded plastic cups to protect your fragile bits. IPX foam cushioning.
If you’re climbing a mast in anything other than benign conditions, you’ll be thankful you invested in body armour.

  • injection moulded plastic to shoulders and elbows
  • comes in wide range of sizes from small to xxl

from £123.96

Buy O’Neal Underdog protector from Alpinetrek.co.uk
Buy O’Neal Underdog protector from Amazon.co.uk
Buy O’Neal Underdog from Amazon.com

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