GEAR: PROPER INFLATION PRESSURES FOR WINGS

Inflating your wing to the appropriate pressure means putting aside the references inherited from kitesurfing.

While the construction of a wing and a kite is similar in principle, assuming that they should be inflated to the same pressure is a mistake that could ruin your session with a loud noise. We explain why in this article.

A wing does not have the dimensions of a kite

Certainly, kites and wings share a common inflatable structure made of bladders wrapped in a very resistant fabric such as Dacron or even more robust materials like UPE Aramid, covered by a lightweight canopy, which in the case of GONG wings, is further reinforced with a triple ripstop fabric. However, the pressure required to stiffen the inflatable structure can vary significantly due to differences in bladder diameters, which are no longer comparable to those of a kite, as shown in the table below:

What is the relationship between pressure and the diameter of your bladder?

The relationship is crucial because the circumference of a bladder directly determines the pressure needed to achieve the desired surface tension.

Explanations: To understand the forces acting on an inflatable structure, one must become familiar with surface tension. For both wings and kites, surface tension corresponds to the force exerted on the fabric of the leading edge and the central strut once they are inflated. This force is directly related to both the pressure and the diameter of your inflatable structure. This relationship is studied on the widest section of the inflatable structure, at the center of the leading edge, where the fabric is under the greatest tension. The relationship is as follows:

For a given pressure, the diameter determines the surface tension (F) on a section (L) of your wing. The significant differences in diameters illustrated in the table above imply substantial variations in surface tension.

As observed in this table, a 5m² wing has a diameter at the center of its leading edge that is 171% of that of a 9m² kite and 212% of a 4m² kite. This represents a difference from one to two times the size. Thus, for a diameter that doubles, the surface tensions are multiplied by 2, requiring half the pressure to achieve an equivalent tension in the leading edge.

Two Examples:

Example 1:

At equal pressure, a 5m² wing with a diameter of 263mm should withstand 1.71 times (i.e., 263/154) more surface tension than a 9m² kite with a 154mm diameter leading edge. This results in a dangerously high increase in surface tension on the widest section of your inflatable structure.

Example 2:

The difference increases even more when comparing a 7.5m² wing to a 9m² kite. With the same pressure, the surface tension difference does more than double: 2.07 = 319/154. If a 9m² kite must be inflated to 8 PSI, maintaining an identical surface tension for a 7.5m² wing, and therefore comparable stiffness of its structure, would require a pressure of only 4 PSI (since Force / Length = Pressure x diameter x Pi = 4 * 319 * Pi = 8 * 154 * Pi).

Wing foiler: Jules, GONG staff, on a Superpower DP 5.5m2 and a HIPE Perf.

A central point of attention

This purely physical reasoning is unavoidable, regardless of the model or brand of your wing. The relationship between tension, pressure, and diameter also explains why a bladder rupture due to overpressure always occurs at the widest section (which is the leading edge of your kite/wing in an open one-pump system). This is why specific reinforcements and assemblies are used on this section of your wing.

Moreover, unlike a kite where forces are distributed across multiple bridle points, the widest section is also the most stressed in a wing (pumping, jumping, etc.). A wing also endures more contact with water and waves. Its construction is therefore significantly reinforced at key points.

Thanks to the specific seams, assemblies, and reinforcements in a wing, you are effectively protected from rupture, even during intense use, such as that by our team riders with extended sessions, massive tricks on each reach, and sometimes violent crashes. However, inflating a wing to the pressure recommended for a kite in a structure that is twice as wide is abusive and offers no rigidity advantage. Imagine inflating a mountain bike tire to 5 bars instead of the required 2.5. The first tree root on your path could cause an ear-splitting burst. This is all the more regrettable given that 2.5 bars provide the best operating range for your tire.

Wing foiler : Malo, team rider GONG, en Droid UPE Aramid, Stunt FSP Pro, mât HM, Ypra Surf-Freestyle et stab Freestyle.

“That’s how I always inflate my wing”

Yes, it is possible to inflate a wing to the pressure that’s actually recommended for a kite without it bursting. GONG wings, for example, are designed to withstand pressures higher than their theoretical operating pressure. However, as highlighted in one of the detailed examples above, a kitesurfer who inflates a 7.5m² wing with the same care as they usually inflate their 9m² kite is actually applying 2.07 times more load to the central section of the leading edge of the wing. Such a practice is unsustainable. The fatigue caused by repeated over-inflation will eventually lead to an "inexplicable" tear because "it was always inflated that way." Not to mention the person buying a second-hand wing that has been regularly over-inflated...

A wing’s tolerance to overpressure allows you to sail for some time without realizing that the pressure is unnecessarily excessive. When the limit is exceeded, it’s always a surprise. Despite usual precautions, a rupture occurs at the worst moment. To avoid ruining your session and keep your equipment in perfect condition, simply follow the small tips in the video below that are specific to inflating a wing.

What is the ideal pressure for a wing?

As explained earlier, the ideal pressure will differ between a 2m² wing and a 7.5m² wing. To avoid confusion, we recommend the method illustrated in the video above, which works regardless of the size of your wing and in the absence of a gauge on your pump.

While inflating, take pauses to press on the leading edge at the height of the central strut with your hand:

If your wing bends significantly, it is not sufficiently inflated.
If your wing bends slightly, it is adequately inflated. A flick on the leading edge should make it resonate.
If your wing does not bend at all, it is likely over-inflated.

As shown in this video, check the creases created under the pressure of your hand. On a perfectly inflated wing, creases should only appear at the central strut when pressed with your hand. If you see creases elsewhere, the wing is not sufficiently inflated. If there are no creases, gradually release the pressure by opening one of the two valves.

Wing foiler: Julien, GONG team rider, with a Plus Perf Series and a Mint FSP 2X.

Using a Gauge

Recommended pressures are listed for our wings. However, we do not recommend using a gauge to inflate your wing for several reasons:

The reliability of the gauge is inconsistent on most pumps available on the market.
The reliability of the gauge is not guaranteed on a quality pump, as the airtightness of the hose can quickly deteriorate when its tip is sanded down.
The inflation valve has a check valve that does not allow pressure reading without further inflating the wing. Additionally, the gauge needle moves rapidly, making it difficult to read the pressure accurately.
How you connect your pump to your wing also influences the reading. For example, if the bayonet of the hose is not correctly connected (not locked with a quarter turn), there can be a pressure difference of 3 PSI compared to a properly locked bayonet.

Take several pumps with gauges to the beach and have a test; you may be surprised by the variations from one pump to another. And note that a 2 PSI difference is already significant for your wing’s pressure. The same goes for electric pumps, which often display 2 PSI more than the gauges on manual pumps. Unlike you, the electric pump will not stop when the wing is clearly visibly inflated enough.

Furthermore, as explained earlier, the ideal pressure is specific to each wing. Referring to a PSI measurement on a gauge could cause confusion during a session, such as inflating your 6m² wing to the usual pressure of your 4m² wing.

On a kite, things are different because the surface tensions are much lower at the same pressure, which implies greater margins. Also, diameter variations are less significant from one size to another. That’s why our pumps’ gauges do not indicate a pressure range for wings.

Wing foiler: Malo, GONG team rider, on Droid UPE Aramid X, Stunt FSP Pro, HM mast, Ypra Surf-Freestyle and Freestyle stab.

Remember that a wing is not a kite, and that one wing is not the other!

We can observe a simple to double evolution for the recommended pressures on identical models of wings, but of different sizes.

Caution and Experience

The greater sensitivity to pressure of a large-diameter inflatable structure like a wing calls for caution when starting out. It is better to be slightly below the ideal pressure than to suffer an unpleasant surprise. At worst, if your wing is under-inflated, so much so that you feel a lack of stiffness, you can always return to shore for a few more pumps. The ideal pressure is sometimes just a few pumps away, so again, proceed step-by-step. With experience, you will gain a good sense of pressure by using the method mentioned above.

Wing foiler: Melissa, GONG staff, in Plus Perf Series with a HIPE Perf.