Earlier in the year, [rctestflight] created an active hydrofoil RC craft, but found the actual performance to be very flawed. Lucky for him and for us he kept tweaking it and one tweak suddenly turned it from a nightmare to a dream.
That tweak was adding ArduPilot’s aircraft model. The design had three servos, each of which controlled the angle of a foil under one of the three pontoons. The ship propelled itself through some screws mounted on top. If you know a lot about ArduPilot, you will notice that active hydrofoil is not on the list of supported platforms, and you are right. [rctestflight] points out that the three servos actually function like a plane underwater. The front two are ailerons and the rear is an elevator, all things ArduPilot manages to tackle with a tightly controlled loop, except for one thing; there are no elevation data.
So he stole a trick he’d previously developed for his ground effect plane and used a distance sensor to tell ArduPilot how to adjust things. He used a sonar sensor instead of lidar as it works better with water and he was pleasantly surprised when he took it on the lake and it worked just great. The original goal with the active stabilization was to make the efoil immune to choppy waters, and we’re sorry to say it didn’t quite achieve that lofty goal. The single sonar sensor tracks the wave in front of it beautifully, but can’t handle the complex waves thrown at it. Perhaps some sort of sensor fusion algorithm could provide the necessary data to be truly resilient. But we love watching the foil glide over the water and it’s hard to remember that it’s actively flying rather than just floating that way.
Others have tried to 3D print a hydrofoil but have failed, while others have succeeded. We love that [rctestflight] came back to finish the fight and came away as champion. Video after the break.
This post Hydrofoils love this one simple trick
was original published at “https://hackaday.com/2022/03/04/hydrofoils-love-this-one-simple-trick/”
