Resistance and Reduced Purchasing Power

The “old” way to rig a Laser put a premium on strength and was tough on older and smaller sailors and really a pain for everyone in a brisk breeze. The new vang, cunningham and outhaul are much easier, but the rules allow more leverage than you may need or want. More leverage or purchase isn’t all good; it means you have to pull extra line through the system and will end up with more tail resting in the cockpit. For instance, with 8:1 purchase you have to pull eight inches of control line through the system to move the sail one inch.

Pulling line is a two way process, you pull the line in (trim) and the sail has to pull it out (ease.) This is most obvious at the mainsheet. When a sail is catching a light breeze and you round down wind at the leeward mark, you are asking the negligible power available to pull the sheet all the way out to a running setting against the now reversed leverage. What was purchase now becomes reversed purchase or friction; every inch of sail motion has to pull eight inches of control line through the system.

This same effect happens with the vang, cunningham and outhaul. Picture the wind coming up and overwhelming your ability to keep the boat flat. You pull the cunningham to stretch the luff and twist off the upper part of the sail – the 8:1 purchase makes it easy. Now the wind eases and you want the power of a fuller upper sail and you release the cunningham. The stretch in the sail material and a bit of pull from the light air have to work against the reversed purchase, friction, to draw eight inches of line through the blocks in order to ease the sail one inch.

Moving more line through the system also just plain takes more time. Increased lengths mean any adjustments take longer, you spend more time being at least slightly distracted by the trim and ease process and less time with your attention fully out of the boat.

Additionally, cutting down on purchase cuts down on the length of the line tails that hang into the cockpit and that can potentially tangle in the mainsheet block (see “Keeping an Eye on Loose Ends”),  and get jammed between the centerboard and the centerboard well. And of course, extra line in the cockpit will loop around your feet and create a rolling surface that can throw you off balance in a tack.

We were setting up a couple of members’ boats at the club a few days ago. (I know I keep talking about rigging Lasers at the club and I want to assure you we were also sailing.) In the interest of keeping things simple I was suggesting that the owners consider taking a piece or two of purchase out of their cunninghams and outhauls.

I’ve listed some of the reasons to reduce line, but the legitimate question from these sailors was, “How much purchase will I need?” Here’s what I’ve found in the last five years of sailing a Laser in everything from wafting breezes of 4 or 5 knots to overwhelming conditions, for my weight and age, with winds in the high twenties and gusts into the thirties. It is also worth noting that I use both Radial and Standard rigs with the same control line setup.

·         I have never felt I was working very hard at trimming my cunningham with three secondary falls and a single line through the grommet for a 6:1 purchase. Even those of us who are lighter and use small line can get adequate tension on the sail luff. (Note: Some sailors will call this setup 3:1.) It isn’t perfectly easy, but is certainly possible.

·         The outhaul works great with 6:1. A primary line from the fairlead to the sail back through the fairlead and to a block alongside the boom (3 falls). The line you pull goes from the mast to the block on the boom and back to the mast block (x2) down to the turning block and then to the cleat.

·         Leave the vang with its full purchase until you’re sure and then if you decide to take something out try to keep the overall purchase above 9 or 10:1 until you’ve convinced yourself that you can get by with less. I’ve tried it with one less line in the primary from the boom to the vang cleat and it worked fine, but I like it better with the full 15:1.

·         Mainsheet purchase can’t be changed, but you can get a bit of extra leverage by using a larger size mainsheet ratchet block. I don’t find that it is necessary. I have the smaller Harkin automatic ratchet block.

It is worth mentioning that smaller size lines seem to create a lot less resistance on the ease (See “New Line”).