Wild Oats X, the 20m canting keel yacht built to defend the Admirals Cup, was sailing from Sydney to Hamilton Island and was 90 miles south of Coffs Harbour when, about 3am, there was a loud bang.
Skipper Troy Tindall said the whale hit the yacht's forward rudder, bending the hydraulic steering arm.
A few seconds later the flukes of the whale rose from the water and slapped the stern of the boat.
The stainless steel stern posts and stanchions were bent and the boat's lifelines were ripped from the stern.
Large numbers of humpbacks migrate north to calve in the tropical Whitsunday waters at this time of year.
It's a popular time of the year in the Whitsundays, with the dual Australian Tourism Award-winning Hahn Premium Hamilton Island Race Week being held from August 19 through to August 26.
No long term damage was done to the whale, boat, or crew and Wild Oats X will be racing at the Hahn Premium Race Week while the Oatley supermaxi will race at the Maxi World Championships the week after Hamilton Island's regatta.