Sailing the Drifter
What do you do when the wind drops?
By Kim Miller from her page
You are on the way to the lake and as you drive you watch the trees blowing in the breeze. "Not a lot of action there" you say to nobody in particular. When you get to the lake you look at the breeze ruffling the water. Not a lot of action there either. However, Hobie sailors are the eternal optimists, and you rig the boat.
Not a scrap of wind at any point of the compass.
As you sail away from the beach you notice that the breeze is fading as you go. You look behind, and the water all the way back to the beach is glassy. Slight breezes hit the water in broad patches, then they drift off. So where did the wind go?
The drifting wind is one of life's mysteries. It's probably related to the other great mystery of life, "how come my socks disappear in the wash only to return as wire coat-hangers in the wardrobe?" The drifter can be the greatest frustration of sailing, unless you know how your boat handles this kind of wind.
If you are racing then the frustration is worse. The drifter will level out the performance of one boat against another, and your normally fast Hobie might find itself beaten to every mark by a 14 foot monohull. The shame of it!!
Rig For The Conditions
You need a fuller sail in light air. This normally means putting extra push into your battens when rigging. But you also need the sail to fill easily when you go to the opposite tack. This means having lightly fitted battens which will swap sides easily. So you already have to compromise. The drifter will not be strong enough to flex the battens and push the sail to the other side when you tack and you will have to do it by hand. If you have light battens, use them in light air. If you have heavy stock battens make sure that you can push the sail to the opposite side easily when you tack.
Reduce Water Resistance
The next thing to remember about sailing the drifter is to cut down your boat's resistance to movement. You have a reduced power source, so reduce friction accordingly. You can do this in lots of ways.
Clean your hulls before sailing.
Road grime will slow your boat if the winds are light. If might not feel like much, but any projections will add to resistance, even the small stuff of road grit. Wash it off.
Get the transoms out of the water.
The "flat bit" at the back where the rudders attach acts as a brake on your boat. The turbulence it causes slows you down, and the further into the water it is the worse it is. You need to keep the water flowing past the boat without it having to kick up into the space created by the lower edge of the transom. Sit as far forward as possible in all directions of sail to keep the rear end out of the water. Sit close to centre to keep both hulls evenly matched.
Raise the windward rudder.
In light air having both rudders in the water is unnecessary. The extra resistance caused by using two rudders can be readily seen if you are racing. Some people are "compulsive" rudder raisers, others say it does little good. However, in a drifter, get that rudder out of the water to cut down your resistance. There is one situation in a drifter where you need both rudders down. Read on until you find out what it is.
Don't Move Around the Boat
Every time you move you upset the balance of the boat. This causes problems with the mast and the hulls. When you move across the tramp the mast swings. Therefore the sail has a different airflow over it and you can lose power. Any advantage you get by swinging the mast forward into the wind will soon be lost as you swing back to normal. The boat will gain from a stable air flow in light air. If the sail swings about it upsets the air around it and it takes several seconds before that air flow becomes smooth again.
Secondly, moving about causes the hulls to move vertically in the water. This also upsets the flow of water past the boat. You can count on at least one boat length before things get back to normal after the boat has stopped rocking under your movement. If you must move to adjust something, move slowly and lightly.
Teaching an old sea dog new tricks. "Flash" the Irish Setter looking for the nearest wind. Notice the glassy water in the background. That's the drifter.
Other Aspects of Sailing the Drifter.
Other Aspects of Sailing the Drifter.
Use Your Body to Advantage
When sailing to windward, keep a low profile. There is nothing to be gained from sitting up and allowing the wind to blow you back where you came from. Lie along the tramp or sit close to the mast.
When sailing downwind, sit/stand in the sail facing backwards. This keeps the boom standing out against the rake of the mast, keeps the sail full, and still allows you to see forward around the mast as well as aft.
The Drifter's Magic Wand.
Imagine that you are sailing to windward in a slight puff, you get some momentum (can't call it speed here) and then the puff dies. You sail forward over almost glassy water from the built up momentum. Up ahead you can see the next puff coming across the water. Your windward rudder is up, you are sitting very low, the boat is very stable and seems to be going ahead almost by magic. As the puff hits you slide to a stop and that Laser floats past you. What has happened? You've just been hit by the drifter's magic wand. Drifters love doing this to catamarans. Ready for a bit of theory? Here goes.
When you are sailing the drifter the sail is working in the normal fashion. The air flows over it, and you go forward. However, there is a “secret” force on the boat which comes into its own in a drifter. This is the pivoting force which will make your boat turn into the wind and stop in irons. Here's how it happens.
The forward thrust of the sail does not push directly forward, it pushes out from the sail at an angle, say between 30 and 60 degrees, to leeward. This angular force is directed forward by the shape of the boat, the set-up of the rudders, etc. However, imagine the mast as a fixed post around which the sail pivots. As you push the sail outwards, it tries to pivot around the post. In a drifter that pivoting action is significant.
When you sail across a “blank spot" and into the next gust, the boat does not have enough resistance under the waterline to counteract that pivoting action and the effect is to turn the boat towards the wind. Then you find yourself pointing so high that you get in irons and the boat stops. If the wind was stronger you might go backwards.
Catamarans can be especially prone to this because many of them don't have centreboards. The centreboard/rudder combination gives more steerage control. Without that control it is much easier for the boat to head to wind and stop.
You can stop the drifter’s magic wand from getting to you by bearing off downwind a little before you reach the gust. This will mean that the gust will give you some boat speed, and therefore resistance against the pivot action, then you can point up again to your proper heading.
When Both Rudders Are Needed
So here's the situation. You are drifting across that "blank spot" again. You see the slight gust up ahead. You turn downwind a little. The gust hits, and you stop in irons again. What has happened this time? Simple, the pivoting force is resisted by underwater resistance, and you don't have enough of it. The drifter has beaten you this time. Put both rudders down to increase your fight power.
When you are going very slowly the boat does not have much lateral resistance. Here's how to check it out. Put the boat in waste deep water. Stand to one side and push gently against the tramp frame to move the boat sideways. If you push gently you can get the boat to move slowly. Now push harder and see how fast you can push the boat. You will soon hit the limit as the resistance builds up very quickly.
When you sail into that puff the slow boat speed means that even a gentle force can bring the boat around head to wind. To fight against it you need as much lateral resistance as you can find, so you need both rudders in the water. If you are not going very fast the rudders will not work very much. This is what is called "steerage way". It means that the rudders don't do anything until there is enough boat speed.
You can sail the drifter to windward with a rudder up, but when you enter the next puff you might need both rudders down to give you enough steering effort to prevent the boat going into irons. The pivoting action has the maximum effect with minimum boat speed, so prepare ahead to counteract it.
Tacking Past Head To Wind
Here we go again. You tack around the windward mark and come to a standstill, while too many others pass you by. Into irons again, how did it happen this time? Probably because you thought you could tack at the same angles as you normally do with better wind. But the drifter will try to use its magic wand against you and you must turn differently.
Before you tack make sure you have the speed needed to get you past head to wind. You might have to bear downwind a little to build up speed. When you tack, don't try to head too close to the wind until you have got some speed back. Steer down further than necessary, build up speed, then head up to your proper course. You might be a little frustrated at having to steer so far downwind, but it is quicker than getting out of irons.
Sail Management When Tacking
The wind will not be strong enough to always push the sail over in a drifter, you will have to do it by hand. If you have set the battens lightly this will be easy. Stiffer battens means that you might have to stand on the tramp and push as high up the sail as possible to get all the battens to flex across.
Develop speed in doing this but keep your movements gentle rather than bustling. Practise tacking without adjusting the traveller or main sheet. Just steer around, flick the tiller across, go under the boom, push the sail/battens across, and adjust the mast rotation. As you are going under the boom pull the jib-sheet to the new position. It is important that the sail is not left billowing to the wrong side.
Getting Out of Irons
The secret? There isn't one. There are only the normal methods. If the wind is strong enough to move you backwards you can reverse the rudders and allow the wind to push you back to a better heading. If the wind is not enough to push you backwards push/pull the boom as far towards the side as you can. This will change the angle of attack on the sail and you will start to move forward. When you have steerage way adjust the boat back on course.
The best view of a drifter is always from a distance.
You can see the glassy water covering too much of Lake Albert in the background. In the foreground is a Manly Graduate, a spinnaker rigged 14 foot design from Sydney, Australia. The author's Hobie is the one with the red sail panel. The other cats are Paper Tigers.
Kim Miller