All the copper pipe flutes have stoppers inside. Not necessarily all cork though but that would work too. With pipe it was easier to turn a plug out of wood and glue thin sheet cork to it for an airtight fit (Like clarinet tenons). You could sand down wine corks, but that would be a lot of sanding on the smaller diameter pipes
did u put a cork screw in the copper pipe?
All the copper pipe flutes have stoppers inside. Not necessarily all cork though but that would work too. With pipe it was easier to turn a plug out of wood and glue thin sheet cork to it for an airtight fit (Like clarinet tenons). You could sand down wine corks, but that would be a lot of sanding on the smaller diameter pipes