Jordan Spencer discusses the effects of three main control lines.
In the last couple of months we have been talking about boat trim and sail trim as the primary methods for steering a dinghy. After a recent conversation with a national coach, I want to extend the discussion to some of the major control lines and how they affect a boat.
The three major control lines we use on a dinghy for small gear changes, are the vang, outhaul and cunningham. Each affects sail shape, responsiveness and yes, steering. So if we can increase our understanding of these controls, we can sail the boat more easily.
A boom vang works by putting pressure on a boom. Pulling on your vang will force the boom down, and it also causes the mast to bend, because the boom will apply a forward force. So generally, pulling on boom vang will tighten the leech of your mainsail, but it will also bend the bottom of your mast, which will flatten the mainsail. It is a fantastic control when you are starting to be overpowered! In this situation, you are trying to transition your sails from a high lift, high drag setup to a flatter, lower drag shape. You are also dumping a bit of main to remove power, so having the vang on will hold your leech up and prevent you losing too much height as you ease your mainsheet.
From a steering perspective, once you have transferred to vang sheeting, it is your vang more than your mainsheet that can overpower your boat as you try to bear away at a top mark. The correct process is to ease vang just before the top mark, then ease sheet as you round the mark and steer down. If you try to bear away in any pressure with too much vang on you will struggle.
Of course every boat is different, but in most boats the vang is the primary control line. It should be a fluid tool, controlling twist downwind and upwind and a major part of the controls for mid and lower main depth. If you use your vang as a set and forget tool, you are probably going slow.
The Cunningham also affects your mainsail leech and your mast bend, but its effects are felt at the top of the mast. The cunningham works by compressing the mast. As you pull on Cunningham, it pulls down on the mast and the most pressure is felt at the top of the mast, so it bends the mast at the top. Bending the mast will flatten a sail and will reduce the tension on the leech. So pulling on Cunningham will depower the upper part of your mainsail and open your leech. If you don’t adjust any other control, the effect of more cunningham is to produce a lower drag shape with better gust response. It is also harder to stall than a rounder sail, so works well in heavy seas.
Of course if you are underpowered or lacking some height, easing some cunningham can assist. The cunningham’s effect on steering is secondary. It’s use can often mean less work is required on the mainsheet or the helm to keep the boat tracking. Having it on won’t prevent you bearing away, (in fact it will probably assist in a minor way). Its effects are felt when travelling in a straight line.
The final control for this month is the outhaul. The outhaul sets the depth at the bottom of the main, but it also controls the amount of leech return a sail can have. Leech return is the round or curve a sailmaker puts into the back of the sail. Leech return is great for height and power, but it also causes drag. Pulling on your outhaul will reduce the leech return, reducing drag and power, which is exactly what you want once you become overpowered.
Remember though, its not a control where you just give a good tug and think… that’ll do. As you pull on outhaul, you are reducing drag and power, but you are also reducing your ability to hold your height. So if you are two boating and you have tried everything, but are still struggling for height, or if your are racing and you need to climb off someone’s hip, or lee bow someone, try easing a little outhaul, because the height will then come easier. This also means you need to use less helm, so less drag from the rudder and more speed.
It’s time to take control.
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