If the duct tape is fairly fresh, simply strip it off by hand, and then remove the remaining adhesive with a suitable solvent. I like to use laquer thinner, as it has a half dozen solvents in it that will dissolve just about anything. Dont spill it anywhere you don't need it. Wax the hull after the removal, as the solvent removes the wax, too. Old duct tape works the same way, except tht almost all the adhesive is left behind and has to be dissolved. Joe.