Monday, November 07, 2005

The First Leg | Mainsail Controls

The main sail (in most instances) has the most possibilities of adjustment when it comes to trim. The controls include halyard tension, mainsheet, outhaul, cunnigham, boom vang and backstay tension and traveller. The J is particularly sensitive to minor adjustments to the main. A little traveller, or mainsheet, or a little boom vang makes a noticeable difference.

Positioning and depth the draft of the sail is the key power in the main sail and ultimately speed. The key to speed is lift and creating the surface area to provide lift. The controls are all designed to move and position the draft to ultimately balance between boatspeed and weatherhelm. Too much heel is slow. Generally each boat has an optimum heel angle which should be maintained.

Here are a number of resources for mainsail trim and controls. The first couple are from Sailnet. The first is a good look at the mainsail and explains each control and its general purpose for overall sail shape. It comes in 2 parts. Part 1 of "Mainsail Controls for Performance" can be found here.. It covers halyard, cunningham and outhaul adjustments. The second half of the article covers backstay and boom vang.

The second article from Sailnet, "Basic Mainsail Trim for Racers" Part 1 and Part 2 are more specific to racing and deal more with the angle of attack and twist of the sail, and explores the concept of shape and power more. The article, by Pete Colby, deals with chord length and surface area and other advanced concepts. Very good read.

Performance Racing - Mainsail Trim & Controls by Bill Gladstone deals with some of the same details as the above articles and offers some good visual cues to demonstrate the closed and open leech and twist as well as a good visual that shows how backstay tension affects the main. Also deals with balancing the boat between speed, pointing and weatherhelm.

This article by North Sails is goes over the basic controls as well. If you have read the top few it may not offer much more info

Some J specific links to mainsail trim. First from JWorld Articles, secondly from the J24 class site written by Geoff Moore. If you are a J24 sailor you probably have checked them out already. If not there are a few good tips and vantage points that might help. The Geoff Moore article has some insights into mast pre-bend and the importance of tuning. Will be reading this one again when stepping the mast next season.

Bill Holcomb has written an article (primarily for a Catalina) regarding weatherhelm, indicators and ways to adjust for it. One of the ways is adjusting the main and or controls. Worth a peak, deals with some other factors such as weight distribution etc.

I know this one is a repeat from the a previous post on trim but here it is again. North Sails mainsail trim. Has animated visuals and is broken down into sections for easy reference.

Another article by Geoff Moore written for Shore Sails. Not J24 specific and deals with more general concepts of mast bend. Has some good analogies and ways to look at sail shape. Some interesting insights into reading the mainsail control positions to determine keel and mast position and rake and whether they are in balance with the boat. Will give this one another read before stepping the mast as well.


Blogger Aaron said...

1st 2 links in article are broken,

11:05 PM  
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