In 1674, he rose to the rank of admiral, becoming a Convoykapitän. This title was given to those captains of warships who escorted merchant ships along the traderoutes of the Hanseatic League. Karpfanger first took command of the ship Leopoldus Primus, later to be called Leopold I, and later on the Wapen von Hamburg, which launched in 1669. Commissioned in 1668 to protect the merchant ships from the Barbary corsairs, the Wapen was a long warship with a total of 54 cannons, ranging from four to 18 pounds. Karpfanger took command of this ship in 1683, when Leopold I was being repaired.