8/13/2019 Beaufort Scale for Kayakers

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Beaufort Scale for kayakers

The Beaufort Scale is is the international measure of wind at sea, where distances and speeds areusually measured by the nautical mile . One nautical mile per hour is called a knot . One knot is 1.85kilometres per hour or 1.15 land miles per hour.

The force of the wind increases as the square of its elocity, so each new step up on the BeaufortScale is a whole new e!perience at sea. The pressure of the wind on you and your kayak increases

proportionate to the square of wind speed so a wind of 1" knots is no bi# deal, but a wind of $"knots will test the quality of your paddle and spraydeck and could e en kill a kayaker whoseambitions #o beyond his e!perience. %owe er $" knot winds &Beaufort 'orce (, a near #ale) areunusual e en in winter. The best answer if your partner wants to #o kayakin# in a 'orce 8 is

probably * Great, I'll try to take some pictures. Leave me the car keys. *

Force 0 . +alm. o wind. Sea like a mirror. o ice kayakers are ery happy with thise!citin# new e!perience.

Force 1 . -i#ht air. ind speed 1/$ knots.0ipples on water. Sailin# bboats don t ha eenou#h wind to mo e.

o ice kayakers are still happy.

Force 2 . -i#ht bree2e. ind speed 3/4 knots.Small #lassy wa elets.

achts sail alon# ery #ently.

Some ine!perienced kayakers may start to #et alittle an!ious.

Force 3 . 6entle bree2e. ind speed (/1" knots.

-ar#e wa elets, white crests be#in to form.

Sailin# yachts make slow but steady pro#ress,water #ur#lin# alon# the side.

7f you are #oin# to windward, the wind will slowyou down a little but intermediate kayakers arestill happy.

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Force 4 . oderate bree2e. ind speed 11/14knots. 9t sea there are wa es 1 metre hi#h, somewith the breakin# crests called whitecaps orwhite horses . :!perienced din#hy sailors ha e a#reat time. achtsmen start to #et a bu22 out of

bein# at sea.

Short sea trips are possible for intermediatekayakers but they may feel an!ious unlessthey re near the beach or with a stron# #roup.

hen crossin# e!posed waters with the windcomin# from the side, a kayak without a ske# orrudder i s likely to weathercock .

;robably there is #ood surf, but if the wind is blowin# onshore it will be #ettin# mushy .

9stron##roup

en<oyin# 'orce 3 conditions on a sunny day

Force 5 . 'resh bree2e. ind speed 1(/=1 knots.9shore, small trees in leaf be#in to sway, and one!posed sites such as headlands and lon#

beaches this is a noticeably windy day.

On sheltered waters, e!perienced din#hy sailorsare #oin# at top speed, hikin# out to the ma! orusin# the trape2e to keep the boat upri#ht. On theopen sea, there are few small powerboats to beseen. Sailin# yachts find it wet #oin# towindward. They start takin# precautions and

most of them head home. a es may be =metres hi#h and there are many white horses .

7ntermediate kayakers stay in sheltered waters.On e!posed waters, e!perienced kayakers will bein a hi#h state of alertness, knowin# that theremay be the occasional hea ier breakin# crest andthat it would be difficult to carry out a deep/water rescue . They will find it wet and hardwork to #o upwind. Some kayaks willweathercock badly unless fitted with a ske# or

rudder , makin# it difficult or impossible to keepit on course for more than $" minutes.

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7f you stop and rest for a few minutes you willdrift hundreds of yards downwind.

Surf may be #ood, but it may be blown out and awaste of time. >nattended paddles roll off up the

beach.

Force 6 . ind speed ==/=( knots. 7n thecountryside, lar#e tree branches are in motion. 7nthe city, it is difficult to use an umbrella. 9t the

beach, surf is probably blown out and unusable,and empty kayaks may roll away if leftunattended on the firm sand down by the water.

9t sea there are lar#e wa es e erywhere, withcontinuous white horses. The Beaufort Scale waswritten for square/ri##ed sailin# ships whichconsidered winds of this stren#th to be a *stron#

bree2e* but this is a yachtsman s #ale. Theoccasional stron#er #ust will be enou#h to flattena small yacht. 9ny remainin# yachts and small

powerboats head for home.

Short sea trips are possible for e!pert seakayakers, who will find that three miles directlyinto wind and wa es is more than enou#h. 6oin#downwind is a fun slei#h/ride for e!perts. ?eep/water rescue s are now difficult, so if you can t

roll your kayak e ery time maybe you should not be out. Towin# a casualty is also difficult e enfor e!perts. 7f you #et into difficulty and call thelifeboat, flyin# spray and rou#h conditions maymake it difficult for the lifeboat to see you .

Force 7 . ear #ale. ind speed =8/$$ knots. Onland, whole trees are in motion. hen you walkupwind, the stren#th of the wind is anincon enience. On the open sea there are lar#ewa es, but surf is blown out. :mpty kayaks can

roll up a hard sand beach as fast as you can run.

Some ferry ser ices are cancelled. 9nyyachtsmen still at sea are thinkin# seriouslyabout their options. They ha e two reefs in,they e secured all loose ob<ects and sealed theentilators. The person at the helm probablye!pects to be replaced e ery thirty minutes.

9 sea kayaker on e!posed waters in 'orce ( orabo e is likely to be in real trouble. : en top

e!perts are approachin# the limit.

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Force 8 . 6ale. ind speed $3/3" knots. 9shore,the wind breaks twi#s off trees and makes lifedifficult for people on foot. Some dama#e to

property is likely. On e!posed campsites sometents are blown down.

9t sea, isibility is obscured by flyin# spray.:!cept in the most sheltered water there arelar#e breakin# wa es. On sheltered water, akayak #oin# upwind will come to a halt betweeneach paddle stroke and the ne!t.

achtsmen hea e to rather than try to sailupwind. 7f they re near a lee shore they #et on the@%' radio to the +oast#uard. ewspapers reportdramatic lifeboat rescues. uch commercialshippin# is at anchor in sheltered waters.

Force 9 . Se ere #ale. Some dama#e to buildin#s.Slates blow off roofs.Force 10 . Storm. ind this stron# is seldome!perienced on land. Some trees are broken oruprooted. There is considerable dama#e to

buildin#s.Force 11 . @iolent storm.Force 12 . %urricane.

The wa es described abo e are those which would de elop on the open sea when the wind has been blowin# consistently for some time. 7n sheltered waters there may be no si#nificant wa es until'orce 5 or e en 'orce 4.

Leeway

The word leeway usually refers to a boat driftin# sideways, blown by a side wind, so that its actualcourse is &say) 1" de#rees from its headin#. 9ny boat or e en ship will make leeway when there swind from the side. 9 kayak drifts fast because it is ery li#ht and doesn t ha e much to #rip thewater. 9 'orce 3 wind can blow a stationary kayak sideways at 1 to 1.5 knots. The practicalsolution if you re na i#atin# in open water is to keep an eye on your destination usin# transits , andferry #lide strai#ht there.

7f you re a serious kayak na i#ator and you can t see your destination, you could recalculate to makeallowance for it / if you knew how much leeway you were actually makin#. >nless you ha e 6;S,any estimate of leeway is #oin# to be ery appro!imate. 6ordon Brown in his book Sea Kayak &;esda ;ress , =""4) tells how he and a friend were hit by a powerful squall between 7slay and Aura,and they could only put their heads down and wait. They started almost alon#side but when the first#ust subsided it left them more than 5"" metres apart. ?ifferent kayaks, different drift.

The leeway of any particular combination of kayak, kayaker and paddle depends onC the amount abo e the surface to catch the windC the amount beneath the surface to resist sideways motion

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C the total wei#ht of the laden kayak C the hull shape &does a hard chine hull resist leeway better than a round underwater shapeD)C the sea stateC how much your own personal autopilot corrects your course for wind and wa es by unconsciously

paddlin# harder on the downwind side. That s likely to be the bi##est factor.

e can make some attempt at calculatin# the amount of force that the wind e!erts on a kayaker.The eather Station of the >ni ersity of Susse! has an online a table showin# the wind pressure

which e!ists on a flat ertical surface in winds of different forces on the Beaufort Scale. +lick hereto iew . The kayaker in this dia#ram is o erlaid with a 1" cm #rid. +ount the squares. e make it115, so 1.15 square metres. The table indicates that a 'orce 5 wind blowin# from the side woulde!ert a constant force of at least 8 k#. That is a lot, and it must mean a fairly rapid sideways drift.

9 kayaker can apply a force of 14 k# or more with his Eher paddle but you don t normally apply aforce of more than 4 k# to paddle forwards. aybe now you e #ot a force of 8 k# that s tryin# to

push you somewhere you don t want to #o.

Of course, the only reason the kayaker in the dia#ram is a flat ertical surface is that he s not real.%e s <ust a two/dimensional profile, but wind resistance is really about three dimensional shapeswhich are more or less streamlined. 9 lar#e but streamlined ob<ect such as a 4/metre lon# aircraftwin# can ha e the same wind resistance as a 4/metre lon# rod which is only the thickness of afin#er. The shape of the rod creates a lot of turbulence. +ompare these hypnotic ouTube ideos of

hi#h and low 0eynolds number flow o er a win# and a rod . 9 kayak is a streamlined shape, butwhen you add a kayaker and a paddle the complete packa#e is not streamlined at all.

Try holdin# your paddle up in the air the ne!t time you re in a 'orce 5 or 4. ou can really feel thewind #rab hold of it. 7n a 'orce 5 side wind some kayak F kayaker F paddle packa#es will driftsideways at walkin# pace. 7f your kayak has hi#h olume G or there is clutter on the deck such as adeck ba# , fishin# equipment and a helmet you are not usin#G or your paddle is lon#er thannecessary , you will find the wind is more of a problem than if you are in a low olume kayak andha e a streamlined profile.

ost sea kayaks weathercock in hi#h winds. They constantly turn to windward. 9 lot of sea kayaksare fitted with a ske# or rudder to pre ent this. ou e also #ot wind/#enerated wa es to thinkabout. : en if you re in a well/desi#ned sea kayak, control starts to become an issue in hi#h winds,so you re not likely to be doin# any fancy na i#ation, but it s still worth thinkin# about leeway.

9nother factor in na i#ation is wind/induced current. 9 wind which blows continuously for se eraldays o er open water will create a surface current of up to =H the speed of the wind. So a 'orce 5wind may create a surface current of up to ".3= knots.

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