Of 300 boats which set off, only 85 limped home.
John O’Donnell told the story of the race as part of the Hardiman Summer Series.
The sudden storm, known as the ‘Fastnet Low’ had brewed in the US where it had already wreaked havoc.
The storm swept across the Atlantic, building momentum, but forecasting abilities were limited in 1979 without internet or satellite technology.
The weather service predicted only a force eight gale though the on-board barometer dropped dramatically.
He describes the crew’s preparations as ‘amateurish’. They had no proper provisions and the cooking fuel gas canister had been left behind in the harbour in Cowes.
Sundowner had nine crew members but life raft spaces were for only eight.
John O’Donnell said that as inexperienced family sailors, they had never experienced the wind which rapidly got up to force 12, with waves as high as a two-storey house.
Other crews made the mistake of abandoning ship much too readily.
“When you are going from your own boat into a life raft, you don’t step down into a life raft.
“In other words, your boat should be sunken so far down under the waves that you step up into a life raft.
“That was a serious mistake that a number of people made,” said John O’Donnell.
On the Sundowner, the crew strapped themselves in with two ropes.
They survived, despite being washed over the side, though the force of the water had opened safety harnesses.
The largest air-sea mission in peacetime, comprising 4,000 people, was rushed into action to rescue the sailors.
But rescues were technically difficult, because a boat’s mast could get tangled in the helicopter.
The crew had to get into the water to be winched back up to safety.
“It was a pretty terrifying experience,” recalls John O’Donnell.
As the storm abated, the Sundowner drifted in open seas, its signal and radio destroyed by high winds.
Eventually the crew picked up the beam from Tuskar lighthouse and found their way into Rosslare harbour.
A wary hotel night porter was unwilling to admit the bedraggled crew, believing them to be part of the Carnsore Point anti-nuclear protest festival, taking place at the same time, John O’Donnell recalls.
His full account of the Fastnet Race can be watched online, as part of the Hardiman Summer Series.