You know those old cliche that the younger generations have begun to cynically despise: \u201cfollow your dreams!\u201d \u201cYou can be anything you put your mind to!\u201d \u2014 well, perhaps they are true on occasion. For instance when [rctestflight] had PCBs that dreamed of becoming a hydrofoil<\/a>, he found a way to make that dream come true.<\/p>\n It\u2019s kind of obvious in retrospect: printed circuit boards are made of FR4, which is a form of fiberglass, and you know what else is commonly made of fiberglass? Boats<\/em>. So yes, the material is suited for this task. The fact that solder joints hold up to use in a little remote-control hydrofoil is less obvious, but good to know. It certainly makes for easier assembly for those of us who have developed an allergy to epoxy.<\/p>\n Ease of assembly wasn\u2019t really the point here: the point was that by making the \u201cmast\u201d of the hydrofoil out of PCB\u2013 that\u2019s the part that holds the underwater wing\u2013 [rctestflight] figured he could (shock!) print a circuit onto it. Specifically, a liquid-level sensor, and because microcontrollers are so cheap these days he went the \u201ctotal overkill\u201d route of embedding an ESP32 on each mast. He started with a resistive sensor, but since those self-corrode too quickly, the team switched to a capacitive sensor that doesn\u2019t need to form a galvanic cell in salt water. Come to think of it, that might still be a problem with the solder joint between the PCBs. Good thing nobody will be riding this one.<\/a><\/p>\n Having such a sensor and brain close-coupled allows for a faster control loop than the sonar [rctestflight] had previously been using to control his hydrofoil\u2019s altitude.. Pivoting each mast with its own servo made for a smooth flight over the water\u2014 well, once they got the PID tuning set, anyway. Check it out in the video embedded below.<\/p>\n We\u2019ve seen PCB\u00a0used for enclosures before,<\/a> and even the chassis of a rover<\/a>, but using it for a hydrofoil is a new hack.<\/p>\n