Sheeting Your Kite - What Does it Do and How Does it Work?
Sheeting – to put it simply – is changing the angle of the kite relative to the wind. Angling the kite more into the wind is called 'sheeting in' and angling it less into the wind is 'sheeting out'. To do this, you move the kite bar towards and away from yourself.
If your kite is set up properly, you will be able to vary its power by sheeting in and out. If you want more power, you pull the bar towards yourself (sheet in). If you want less, push the bar away from you (sheet out).
Those are the basics for sheeting, so let’s get into my favorite part – the science of why.
How Does Sheeting Work?
All that sheeting does is varies the length of the kites back lines relative to the front ones. The difference between the lengths of the lines changes the shape of the kite relative to the wind, and that is what results in the change of power.
When looking at the shape of the kite, remember that it has the shape of a wing. When air flows over the surface of the kite, it creates lift – it’s this lift that makes the kite pull away from you. By changing the angle of the wing in the wind, you can change the amount of lift that the kite produces.
In this picture, the air over the top surface of the wing travels a longer distance than the air passing underneath. This is what creates the lift.
Here, the distance the air flows over the top of the wing is longer than in the previous picture, so the wing produces even more lift.
In this picture, the distance the air flows over the top of the wing is longer than the previous two pictures, so this wing has the most lift.
When we sheet the kite, we do this exact same thing. Here’s why.
When we sheet the kite out, the kite looses power. We let out some of the back lines, which lets the trailing edge of the kite move further away from us. (Remember, with a properly set up and trimmed kite in constant winds, the length of the front lines does not change). When the trailing edge moves further away from us, the kite produces less lift (i.e. it has less power).
When we sheet in, the kites power increases. We pull the trailing edge of the kite closer to us, which creates more lift.
Can the Kite Create No Lift?
Yes. For what we are concerned with, some kites can create no lift. This is what is called depower in kiteboarding. The closer a kite can get to zero lift, the more it can be depowered.
This happens because the distance the air flows over the top surface of the kite is the same (or close to) as the distance on the bottom. Because both distances are the same there is no lift.
Note – If you’re wondering how the kite keeps flying in this case, it’s a combination of wind deflection and lift. The reality is that most kites don’t depower 100% - it’s more like 90% or 95%. In this case, there is still some lift left to help keep the kite in the air.
The full explanation is a little out of scope for this page, but it’s a combo of these two things that keeps the kite in the air.
Can the Kite Create Too Much Lift?
Yes again. It’s not that the kite creates too much lift; it’s that it can be tilted too far into the wind. In this case, the air flowing over the surface of the kite becomes turbulent and the kite can’t produce any lift - this is called over-sheeting.
If the kite is flying when this happens, you’ll notice that it stops moving forward and falls backwards and deeper into the wind window. This is called backstalling.
How Do You Tell When a Kite is Oversheeted?
There are a few ways to tell when a kite is oversheeted - the shape of the kite changes, and the way the kite flies changes.
What Does an Oversheeted Kite Look Like?
You can tell just by looking when a kite is oversheeted. The back corners of the kite pull inwards and give the kite a pigeon-toed look, which looks like this:
How Does an Oversheeted Kite Fly?
An over sheeted kite doesn’t fly very well. If the kite is not parked and is moving through the wind window, you’ll notice it slow down. If it continues to slow, it could stop or even start to fly backwards. If this continues, it will crash.
If the kite is parked in the wind window when it gets over sheeted, you will notice it start to move backwards deeper into the window
That’s sheeting, but it’s not the entire story. This only works well when the kite is properly set up and trimmed. Without having a properly set up and trimmed kite, you’re not going to have a kite that flies well or sheets properly. In this case, you probably won’t notice the depowering (or powering) effects of sheeting.
Learn about tuning your kite and why it’s important to get it right. If you have it wrong, your kite will fly poorly and you won’t be able to maximize your power or depower.