[5] Bethwaite started sailing 18ft skiffs in 1974 crewing on KB, before moving on to the boats 9Sports, Singapore Airline, and Mutual Acceptance.
Internationally, his partnership with Alex Gad developed media driven sailing events throughout Europe, the U.S., and Mexico that resulted in three Sport-Tel awards.
[citation needed] In 1980 based on a stretched Tasar Dinghy hull, he designed the first of the trilogy of Prime Computer 18 ft skiffs.
[12] The 29er has been given International Class status[13] In 2004, he worked with Martin Billoch and Chris Mitchell to design the SKUD 18, a ballasted skiff for disabled sailors.
These incremental improvements resulted in what Frank called “the end of the big boat era.” In 1997 this simpler, faster design was made the standard for all 18 ft skiffs.