Test of the ACCWing, a flexible wing for 20

We mentioned in October 2020 the start of the ACCWing project . After a period of fine-tuning, the project teams invited us to come and discover and test their flexible collapsible wing on their small 10-meter catamaran.

It was the end of July 2023, and the conditions were perfect, with a steady wind. The wind angle permitting, it was decided to leave the pontoon under sail, or rather wing... On the catamaran used to support the first ACCWing, the wing is very easy to set. Like any other sail, a simple halyard at the top of the carbon mast allows the 54 m2 to be hoisted, without having to worry about any luff ropes or lazy jacks.

The wing is made of a classic double skin of membrane sailcloth, with a low boom and 3 intermediate rigid carbon ribs. Even when shocked, the wing quickly acquires a little lift, and it doesn't take long to cast off.

As its name suggests, ACCWing stands for Automated Camber Control Wing, and the patent filed for the invention includes the ability to adjust the camber of the profile. Once we're out of the channel, at a speed that's already quite high compared to the surrounding boats, we can take a look at the wing's adjustment options. At first glance, the operation is fairly classic, with a sheet on each side, shifted with hoists. While the test catamaran was designed for traditional rigging, future ACCWing-designed boats will have circular rails to hold the trailing and leading edges.

For our start, the profile was kept symmetrical, and was already working well. To improve performance, we're testing the possibility of cambering the profile. To achieve this, the system uses flexible joints, called muscles, similar to those in the human body. Working in pairs and fixed crosswise between one side of the mast and the trailing edge of the opposite skin, they retract by blowing compressed air into them. As the diameter increases, their length reduces and the two edges come closer together, the wing naturally arches.

A remote control dedicated to each rib allows the valve to be opened with a simple scuba tank. In this way, the profile can be set separately at each of the four heights.

During our test drive, we can easily see the benefit of the device and the additional power. On the other hand, it can be an easy way to slow down by erasing the camber at the touch of a button on the remote control.

Now that we've got the hang of it, all we have to do is take advantage of the day's weather to test the boat's performance. The 10-meter catamaran is fairly light, and today's weather, with over 15 knots of steady wind, gusts to over 20 knots and a flat stretch of water, is conducive to speed.

Upwind, the wing's ability to climb is quite impressive. We reach upwind speeds of a dozen knots at almost 10° to the apparent wind, and the boat continues to climb at even lower angles. On the beam and at steeper angles, the speedometer climbs and we reach a top speed of 20.2 knots. Back in port after just over an hour and a half's sailing, with no permanent optimization, the boat's average speed exceeds 10 knots.

But beyond pure speed, it's also the tolerance of the profile that stands out. The wind was strong, but even though the boat accelerated quickly, we never felt on the edge. Once the optimal trim had been determined, the boat was healthy at the helm, and the wing's profile was compensated for in relation to the mast, limiting the strain on the sheet. As the icing on the cake, the wing doesn't flap, so the boat is silent, even in a gust of wind.

There's no doubt that this innovation will find its way onto pleasure boats, as well as commercial vessels, in automatic mode. We can't wait to see what ACCWing can do for a pleasure cruiser.