Guide to Sandwich and Cored Hulls
Ultrasonic transducers must make direct contact with the outer skin of the hull. For hulls constructed with a foam sandwich or other core, a small area of this material must be removed to expose the outer skin.
A 150mm (6″) diameter cut out (approx) is recommended as this will allow room to prepare a flat and smooth surface before bonding the transducer ring. The cut edge should be sealed with a gel wash coat or epoxy based filler to prevent water ingress.
It is recommended that this type of installation is carried out when the boat is out of the water.