Kayarchy - the sea kayaker's online handbook and reference

Beaufort Scale for kayakers

This is the international measure of wind at sea. At sea, distances and speeds are usually measured by the nautical mile. One nautical mile per hour is called a knot. One knot is 1.85 kilometres per hour or 1.15 land miles per hour.

	Force 0. Calm. No wind. Sea like a mirror. Force 1. Light air. Wind speed 1-3 knots. Ripples on water. Novice kayakers are happy.
	Force 2. Light breeze. Wind speed 4-6 knots. Small glassy wavelets.
	Force 3. Gentle breeze. Wind speed 7-10 knots. Large wavelets, white crests begin to form. If you are going to windward, the wind will slow you down a little but intermediate kayakers are still happy.
	Force 4. Moderate breeze. Wind speed 11-16 knots. At sea there are waves 1 metre high, some with the breaking crests called whitecaps or white horses. Experienced dinghy sailors have a great time. Short sea trips are possible for intermediate kayakers but they may feel anxious unless they're near the beach or with a strong group. When crossing exposed waters with the wind coming from the side, a kayak without a skeg or rudder is likely to weathercock. Probably there is good surf, but if the wind is blowing onshore it will be getting mushy.
A strong group enjoying Force 4 conditions on a sunny day
	Force 5. Fresh breeze. Wind speed 17-21 knots. Ashore, on exposed sites such as headlands this is a noticeably windy day. Small trees in leaf begin to sway. On sheltered waters, experienced dinghy sailors are going at top speed, hiking out to the max or using the trapeze to keep the boat upright. On the open sea, there are few yachts or small powerboats to be seen. Waves may be 2 metres high and there are many white horses. Intermediate kayakers stay in sheltered waters. On exposed waters, experienced kayakers will be in a high state of alertness, knowing that there may be the occasional heavier breaking crest and that it would be difficult to carry out a deep-water rescue. They will find it wet and hard work to go upwind. Some kayaks will weathercock badly unless fitted with a skeg or rudder, making it difficult or impossible to keep it on course for more than 30 minutes. If you stop and rest for a few minutes you will drift hundreds of metres downwind. Surf may be blown out and unusable. Unattended paddles roll off up the beach.
	Force 6. Wind speed 22-27 knots. The Beaufort Scale was written for square-rigged sailing ships which considered winds of this strength to be a "strong breeze" but they are enough to flatten a small yacht. Ashore, large branches are in motion and it is difficult to use an umbrella. At sea there are large waves everywhere, with continuous white horses. A yachtsman's gale. Any remaining yachts and small powerboats head home. Surf probably blown out. Unattended kayaks roll off up the beach. Short sea trips are possible for experts, who will find that three miles directly into wind and waves is more than enough. Going downwind is an entertaining sleigh-ride. Even for experts, deep-water rescues are now difficult so if you can't roll your kayak every time maybe you should not be out. Towing a casualty is also difficult even for experts.
	Force 7. Near gale. Wind speed 28-33 knots. Large waves at sea, but surf is blown out. Empty kayaks blow up the beach faster than you can run after them. Whole trees are in motion. When you walk upwind, the strength of the wind is an inconvenience. Some ferry services are cancelled. A sea kayaker on exposed waters in Force 7 or above is likely to be in real trouble. Even top experts are approaching the limit.
	Force 8. Gale. Wind speed 34-40 knots. Ashore, the wind breaks twigs off trees and makes life difficult for pedestrians. Some damage to property is likely. On exposed campsites some tents are blown down. At sea, visibility is obscured by flying spray. Except in the most sheltered water there are large breaking waves. On sheltered water, a kayak going upwind will come to a halt between each paddle stroke and the next. Newspapers are likely to report dramatic lifeboat rescues. Much commercial shipping is at anchor in sheltered waters.
	Force 9. Severe gale. Force 10. Storm. Force 11. Violent storm. Force 12. Hurricane.

The waves described above are those which would develop on the open sea when the wind has been blowing consistently for some time. In sheltered waters there may be no significant waves until Force 5 or even Force 6.

 

Leeway

The word leeway usually refers to a boat drifting sideways, blown by a side wind, so that its actual course is (say) 10 degrees from its heading. Any ship or boat will drift downwind. A kayak drifts fast because it is very light and has little to grip the water. A Force 4 wind can blow a stationary kayak sideways at 1 to 1.5 knots. The practical solution is to keep an eye on your destination using transits and ferry glide straight there.

For a serious kayak navigator who can't see his/her destination, if (s)he knew exactly how a kayak was affected by wind (s)he could recalculate to make allowance for it. Any allowance is going to be very rough. Gordon Brown in Sea Kayak (Pesda Press, 2006) tells how he and a friend were hit by a powerful squall between Islay and Jura, and they could only put their heads down and wait. They started almost alongside but when the first gust subsided it left them more than 500 metres apart.

The leeway of any particular combination of kayak, kayaker and paddle depends on:
• the amount above the surface to catch the wind
• the amount beneath the surface to resist sideways motion
• the total weight of the laden kayak
• the hull shape (does a hard chine hull resist leeway better than a round underwater shape?)
• the sea state
• how much your own personal autopilot corrects your course for wind and waves by unconsciously paddling harder on the downwind side. That could be the biggest factor.

The Weather Station of the University of Sussex has kindly put online a table showing the wind pressure which exists on a flat vertical surface in winds of different forces on the Beaufort Scale. Click here to view. The kayaker in this diagram is overlaid with a 10 cm grid. Count the squares. We make it 115, so 1.15 square metres. The table indicates that a Force 5 wind blowing from the side would exert a constant force of at least 8 kg. That is a lot, and it must mean a fairly rapid sideways drift.

Note that the force exerted by the wind increases proportionate to the square of wind speed. So if the wind speed increases threefold from 10 knots to 30 knots, the force it exerts on a kayaker will increase about ninefold.

Wind resistance is not just about two-dimensional surface area or there would be no point making cars streamlined. A strong wind can really grasp an object such as a paddle held up in the air. Apparently a six-metre long rod the thickness of a finger creates so much turbulence in airflow that it has the same air resistance as a six-metre long aircraft wing.

Some kayaks will drift sideways at walking pace in a Force 5 side wind. Compare 8 kg with the forces involved in normal forward paddling. A kayaker can apply a force of 16 kg or more with his /her paddle but doesn't generally apply a force of more than 6 kg.

Another factor to consider is wind-induced current. A wind which blows continuously for several days over open water will create a surface current of up to 2% the speed of the wind. So a Force 5 wind may create a surface current of up to 0.42 knots.

If your kayak has high volume; or there is clutter on the deck such as a deck bag, fishing equipment and a helmet you are not using; or your paddle is longer than necessary, you will find the wind is more of a problem than if you are in a low volume kayak and have a streamlined profile.

 

 

 

 

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