A stroke that will make the kayak glide straight, for example, when you have a wind behind you, and it's picking up some waves, and you essentially want to surf those waves, is called the rudder stroke. The position looks like this. Both hands over the water and the paddle shaft should be equal distance from the kayak. The rear blade is straight up and down and immersed in the water. So the finished stroke looks like this.
The rudder stroke is used to give us directional control of the kayak. It's particularly useful when you want the kayak to glide in a straight line, or to stop the kayak from turning. We use it to glide all the time when we're on waves. These don't have to be big ocean waves, they can be small waves, or just picked up by the wind. The wind is going to be blowing at your back and having small waves behind you. If you can use the rudder stroke, you can control the kayak so that it goes straight and glides straight with those waves which will give you an additional boost to your speed which you can use to go faster with less energy.
The way to accomplish the stroke most efficiently is to rotate your torso to the side that you're ruddering on. The rear blade wants to be straight up and down, not bent in or bent out, straight up and down. The paddle shaft would be parallel with the kayak. Both hands, both blades, over the water, rear blade in the water, straight up and down, and you're looking straight ahead, but torso rotated. We don't usually use the rudder stroke as a turning stroke. You could, we don't generally do that because it tends to slow the kayak down. Learn to use your rudder and you'll learn to make the wind your friend when you're paddling with it.
This has been Mike Aronoff with Canoe Kayak and Paddle Company (CKAPCO). I hope we'll be seeing you on the water!