Size Matters… But Technique Comes First
My Big Air Kite Size Guide
By Wavers Social Club Member Jakob
Picture by Andrew Lythe
A few weeks ago, one of my friends, who had just started jumping and is a good bit heavier than me (me ≈ 75kg), excitedly told me about his plans to buy a 7m kite for going massive on those strong-wind days. As an experienced kitesurfer, alarm bells immediately started ringing in my head. This conversation, which I’ve already had countless times with other riders, inspired me to write this little guide about how I would approach kite size selection — because choosing the small kite for the rare strong wind days might be a potentially dangerous cognitive shortcut that can make the likelihood of accidents increase and here is why.
Quick disclaimer before we dive in. What follows reflects my personal understanding and experiences. If you see things differently, I’d love to hear your thoughts and learn from them. This guide is for BIGAIR kiting only and does not apply to other disciplines.
The Physics Behind the Power
Have you ever noticed how your kite suddenly feels drastically more powerful when the wind picks up? Imagine you are out there cruising along in 25 knots, and all of a sudden, the wind picks up to at least 50 knots. You immediately head to the beach and land this monster that’s towing you. Afterwards, you check the wind readings and see the crazy peak. The readings show maximum gusts of 35 knots. There’s a fascinating reason why this felt like so much more wind. To explain this, we need to look at the relationship between the wind speed and the kites’ power. We felt on the water that a 10-knot difference seemed like a lot more power in the kite. The power we notice is the lift force generated by the wind flowing over the aerofoil. According to aerodynamic theory, the lift force can be calculated by:
L = ½ × ρ × v² × A × CL
Where:
L is the lift force
ρ (rho) is air density
v is wind velocity
A is the kite surface area
CL is the lift coefficient
This equation reveals two crucial insights about kite behaviour. First, the lift force increases with the square of wind velocity (v²). When wind speed doubles, the lift quadruples. Second, lift is directly proportional to the kite’s surface area (A).
Let’s explore what this means for our session if we take a 7m² or a 9m² kite. A 7m² kite has approximately 22% less surface area (A) than a 9m² kite. Now intuitively, one would assume, “If it’s 22% more windy, I’ll just take the 7m² kite and can handle 22% higher wind speeds than with the 9m²”. Let us look at an example of this:
If the maximum wind you like to ride with the 9m² kite is 30 knots, reducing the canopy to 7m² would give us the same power in 37 knots (22% higher). This is wrong!
Plugging the values into the lift equation, we can see that at 30 knots, the 9m² kite is pulling with a force of 161 kg (values aren’t accurate, but the proportions are), which is the end of the comfort zone. The 7m² kite at 37 knots however is generating 190 kg of lift. Which is 18% more than the end of the comfort zone before.
The math shows why the intuitive “22% smaller kite = 22% more wind” thinking is incorrect. Due to the quadratic relationship between wind speed and lift force (v²), the increase in wind speed has a much more dramatic effect than the reduction in kite size. According to the formula, the 7m² kite already generates the same power at 34 knots as the 9m² kite at 30 knots. This is approximately 13% higher wind speed. The following plot gives us a visual impression of the little difference between the two kites and the huge difference that the wind speed makes.
Theoretical Maximum Lift Force Comparison:
Make it stand out
Whatever it is, the way you tell your story online can make all the difference.
This leads us to a crucial insight: even though the smaller kite always has proportionally less power, both kites become dramatically more powerful and harder to control as wind speed increases. The key is that at high wind speeds, both kites may already generate much more power than you’re comfortable with, making the “smaller kite for control” argument less relevant and the slower movement speed of the bigger kite more relevant (We’ll get to that in a bit).
The Influence of Rider Weight
The Parachute Effect: Now on to explain why two riders at different weights should take different-sized kites at the same wind speed. Besides obvious factors like the pull of the kite that needs to stay manageable, there are other variables to consider. Imagine two objects attached to identical parachutes: a car and a bike. Which one drops faster? The car, of course — its greater weight pulls much more on the parachute, leading to quicker descent. This same principle applies to kitesurfing. A heavier rider acts like the car on the parachute, causing a much quicker drop compared to the light rider.
The Anchor Effect: Besides the dropping speed, there is also another crucial aspect of how rider weight influences kite behaviour. The weight of the rider acts as anchorage for the kite. It influences the speed of the kite in the form of flying and turning speed. Have you ever wondered why riders like Giel can pull off double loops with a 9m kite and single loops with a 15m?! Besides obviously a lot of skill, he offers a lot of resistance against the kite as he is a more heavy rider (pretty sure the extra weight is mostly cojones lol). The extra body weight provides more anchoring force, allowing for quicker kite movements and faster loops. This leads us to the assumption that a heavier rider moves and turns the kite quicker than a lighter rider with the same steering input on the bar.
The Perfect Storm
Let’s look back at the initial situation. My heavy friend wanted to use a small kite for the strong wind days. This leaves us with a potentially dangerous combination of:
A fast-moving kite (due to its small size)
High wind speeds (creating exponentially more power)
Greater anchor weight (causing even faster kite and a quick drop)
An unknown kite (different riding characteristics)
In my book, these four parts combined increase the risk of accidents extremely. During jumps or (accidental) rotations, even a slight steering mistake that does not matter much for the 50kg rider on the 7m makes a huge difference for the 80kg rider. The kites’ twitchy movements and intense power make it much harder to maintain control. This only gets worse if you are not used to the storm kite size and speed.
Finding the Sweet Spot
Now, we all like to push our limits occasionally, and this is part of what makes this sport so exciting. However, getting injured and not being able to enjoy kiting at all should be avoided as much as possible. My general rule for a balanced approach is, therefore, for a 75kg beginner to intermediate rider, stick to a slow 8m² or faster 9m² until you are super duper comfortable in storms and high rotations. For different weights, I built a tool that suggests suitable big air kite sizes appropriate to the conditions. It takes the rider's experience and weight into account.
Disclaimer: kited too much and didn’t find the time to fine tune and make it handle edge cases yet
The recommendations provide a balance of:
Manageable power delivery and steering response
Adequate time to react or correct during accidental rotations
Sufficient lift for controlled jumps
The goal here isn’t to eliminate all challenges from kiting — it is to ensure you can progress safely while having fun. For advanced and professional riders, there should not be a need for a tool anymore, but the options are also available in the tool. You might notice it gets very liberal as most kites can be used in a huge wind range with enough skill. Adjusting the kite position and riding speed can compensate for having little or a lot of wind if you know how to use it.
Going Big in Strong Winds
At some point in my kiting journey, I wanted the same. A small kite that I can take out and boost to the moon in super strong wind. I was teaching on Ameland (100% worth a visit btw.) and got the same advice I give you now. Take the bigger size and learn how to use it in strong winds. For this, you’ll want to gradually build up your strong wind riding. As a quick starter, here some tips:
Putting the kite low at 10 am or 2 pm while riding, going slow and engaging your edge by pointing up the toes makes it easy to hold anything. Putting the kite high (at 11:30 or 1:30), will make it very hard to stay in control if the wind is strong. When it comes to jumping, aggressive kite movement is not your friend. By moving the kite slowly and deliberately, you can achieve much higher, more controlled jumps that go vertically up instead of downwind. The kites’ power in strong winds means you don’t need aggressive movements to go big. It will just pull you more downwind. Start in moderate conditions and slowly build up your experience and understanding of how your kite behaves as the wind increases. While it might be tempting to follow the “smaller kite, stronger winds” approach, the physics and practical realities of kitesurfing tell us otherwise. The next time someone suggests going smaller with their kite size, share this article with them. Sometimes, bigger is better — especially when it comes to staying safe while pushing your limits. Just keep in mind that in case conditions actually push beyond what’s comfortable, the best decision is often to call it a day and get some Biertjes with your mates.