GP14 Technical - Sail Setting

From: Subject: GP14 Technical - Sail Setting Date: Fri, 22 Jun 2007 08:46:18 +0100 MIME-Version: 1.0 Content-Type: multipart/related; boundary="----=_NextPart_000_0010_01C7B4A9.CD099B20"; type="text/html" X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1896 This is a multi-part message in MIME format. ------=_NextPart_000_0010_01C7B4A9.CD099B20 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Content-Location: http://www.gp14class.org.uk/technical/sail_setting.asp GP14 Technical - Sail Setting

GP14 Technical - Sail Setting

Thank you to Mike McNamara for allowing us to = reproduce his=20 definitive guide to wind flow and sail setting.=20

The Foresail

When the wind is flowing over the sail properly the windward = windtufts=20 will angle upwards and the leeward windtufts will be = horizontal.

In order to point as high as possible the sail must work as a = complete=20 unit throughout its length. So, make sure that all three windward=20 windtufts collapse at the same time when you luff up. If the top = windtuft=20 collapses first, the leech is too slack and so, the fairlead must = be moved=20 slightly forward and/or the sheet tensioned. If the bottom = windtuft goes=20 first, then slacken the leech by easing the fairlead aft, and/or = easing=20 the sheet

Keep down to a minimum the amount of jib luff sag (which gives = unwanted=20 fullness at the front) by adjusting rig tension so that the = leeward shroud=20 does not go slack.

If there is an eye at the tack, the luff of the sail can be = tensioned=20 to suit the weather conditions. This usually means tightening the = luff in=20 a breeze or when the sail gets older. If horizontal creases appear = along=20 the luff then tension it slightly until they disappear but do not = over=20 tension as this drags the flow forward and ruins pointing.

The Mainsail

The sail is designed to give optimum performance when the last = 6" of=20 the top batten and the last 2=920" of the boom are parallel. Use = kicking=20 strap and mainsheet to achieve this, i.e. if the top batten is = more open=20 than the boom, tension both, while if it is tighter, ease them = both.

Set the luff tension of the sail so that when running in light = winds=20 the sail is smooth without ridging. If a vertical ridge occurs = ease the=20 luff tension until it disappears. If this is hard to remove then = check=20 that the mast is not bending backwards in the middle and forward = at the=20 top. This will prove disastrous on the run. Angle the spreaders = aft and/or=20 let the mast move forward at the mast gate until it is straight or = bent=20 forward slightly in the middle (pre-bend).

As the kicker is used to bring the top batten into line with = the boom,=20 the mast will start to bend forward causing horizontal ripples in = the=20 luff. Tension the cunningham just enough to remove these. Under no = circumstances use more tension than this as this will cause a = vertical=20 ridge.

The fullness along the foot can be varied considerably = according to=20 wind strength and point of sailing. As a general rule, set the = foot so=20 that the sail is quite full and the sail is backwinding. Then, and = this is=20 especially true when beating, flatten progressively until the = backwinding=20 is reduced to a minimum. Do not over tension as this will flatten = the sail=20 too much and power will be lost. You will find that in both light = and=20 windy weather the foot will need to be tight, while in middle = conditions=20 it can be eased, say 1" - 2".

The Spinnaker

The aim of the design is to give a good reaching performance, = but which=20 will also give good speed on a run. If the pole height is correct = the=20 leading edge of the sail should fold in when under-sheeted at = about half=20 height.

Remember also to keep the leeward sheet eased as much as = possible to=20 keep the slot open. Under-sheeted rather than over-sheeted is the=20 important rule.

Finally, I recommend that before you race new sails, you spend = some=20 time afloat getting used to how the various controls affect = them.

Our environment varies all the time. On most days the wind = constantly=20 changes in both velocity and direction. Those sailors who can = adjust their=20 sails quickly to suit these changes are the ones likely to be in = the lead.=20 So:

When the Wind is Increasing.

The effect this has on the sails is to open out the leeches, = helping=20 air escape and encouraging extra speed.

However, if the leech twists away too much then the front of = the sail=20 backwinds at the head, the sail becomes unstable and may even = flog,=20 wrecking both speed and pointing.

The solution is to load the kicking strap until the whole = leading edge=20 of the mainsail collapses at the same time. The jib sheet should = also be=20 tensioned enough to stop the top windtuft collapsing before the = bottom=20 one. At the same time, moving the fairlead aft one or two holes = will open=20 the slot allowing more air to get through the gap. Don't forget to = ease=20 the mainsheet too!

When the Wind is Dropping.

This tightens the leeches; closes the slot and at its most = extreme the=20 main is so loaded that the sail becomes board flat and all speed = is gone=20

The solution is to ease the kicker and ease the jib sheet after = moving=20 the fairleads forwards slightly. But only do it enough just to get = the=20 whole leading edge to collapse at the same time.

Remember the Golden Rule - the later you leave it the = further=20 behind you will be. So, don't delay. Adjust the sails and adjust = them=20 NOW.

Good sailing.

Mike McNamara

Sail and Rig Settings Guide

Conditions	Light = Winds Flat=20 Water	Light=20 Winds Chop	Medium = Winds Flat=20 Water	Medium=20 Winds Chop	Breezy = Winds Flat=20 Water	Breezy=20 Winds Choppy, Rough
Crew = Sitting In	Crew = on the=20 Rail	Spilling Wind Over=20 Powered
Rig Tension	Medium	Medium Slack	Medium Tight	Medium	Very, Very Tight	Very Tight
Jib Sheet Tension	Fairlead forward, sheet = eased	Fairlead well forward, sheet = medium=20 eased	Fairlead middle, sheet = medium	Fairlead middle, sheet = medium	Fairlead aft, sheet medium	Fairlead middle, sheet = middle
Mainsheet Tension, i.e. boom = end=20 position	Boom eased, leech eased	Boom eased, leech eased	Boom inboard, leech medium	Boom slightly eased, leech = medium=20 tight	Boom out, leech very tight	Boom out, leech = tighter
Cunningham	Nil	Nil	Nil to minute	Nil to minute	Medium	Medium
Kicker	Very light tension	Light tension	Light to medium tension	Medium tension	Tight to very tight	Very tight
Main Foot Tension	Very tight	Slightly eased	Slightly eased	Well eased	Tight	Tight
Mast bend	No chocks, mast bent	Slightly chocked, mast = straight	Very chocked, mast = straight	Very chocked, mast = straight	Chocked, mast bent	Medium chocked, mast = bent
Sailing trim	Minute heel, weight = forward	Minute heel, weight = forward	Upright, weight central	Very upright, weight = central	Upright, weight central	Upright, weight = aft

| Contact<= SPAN> | Back = to=20 Top |=20 =

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