The community of Brims in Longhope in Orkney lost a third of its population on the night of 17 March 1969 after the TGB answered a mayday call from the Liberian vessel Irene.
Leading the commemorations is Kevin Kirkpatrick, coxswain of the current Longhope lifeboat, who lost his father, uncle and grandfather.
His wife Karen also lost her father, uncle and grandfather.
The couple’s children, Jack and Stella, now serve on the RNLI crew.
The crew who died were coxswain Daniel Kirkpatrick, 2nd coxswain James Johnston, bowman Ray Kirkpatrick, mechanic Robert Johnston, assistant mechanic James Swanson, crew Jack Kirkpatrick, crew Robert Johnston and crew Eric McFadyen.
At 9:35pm on the night of the disaster, the principal keeper at the Pentland Skerries Lighthouse reported seeing the lifeboat’s stern light heading east on its mission.
This was the last contact with the lifeboat as she failed to respond to a radio message at 10pm.
All of the Irene’s crew were brought safely ashore by Coastguard teams.
It is believed the crew of the TGB faced 60-foot waves as they advanced in near-zero visibility. The vessel failed to respond to messages and was found upturned the following day by Thurso’s lifeboat.
Speaking ahead of the commemorations, Mr Kirkpatrick spoke of the resilience of the local community.
He said: “This will be an emotional day for us all.
“The tragic loss of our eight lifeboat men and the ultimate sacrifice they made will never be forgotten here, but it is due to the strength and resilience of our local community that our lifeboat station continues and still operates from Longhope today.”
Despite the tragic loss of life, volunteers came forward almost immediately to form a new crew.
The 50th anniversary will be marked by a day of commemoration organised by RNLI Longhope and the Longhope Lifeboat Museum Trust.
Events will take place in Brims, South Walls and surrounding waters.
Commemorations include a flotilla of boats, including RNLI lifeboats from Thurso, South Walls and Wick.
The current Longhope lifeboat, the Coastguard tug MV Levoli Black, a harbour tug, pilot boat and vintage lifeboat from Ireland will congregate in Aith Hope to dip their flags as a mark of respect.
The Coastguard will also be represented by one of their rescue helicopters.
A service will be held at memorial in Osmundwall Cemetery on Hoy.
Flags will also be lowered at lifeboat stations across Scotland to mark the tragedy, which was one of the worst disasters in British lifeboat history.
The TGB is housed in the Scottish Maritime Museum in Ayr Museum.
Staff will mark the anniversary by holding a minute’s silence and laying a wreath by the lifeboat’s side.
Jacob Davies, lifesaving manager for the RNLI in Scotland, said: “This is an incredibly poignant time for our Longhope lifeboat crew, their families, the Hoy community and, of course, the RNLI as a whole. We thank our existing crew and their families for the efforts they are making to ensure the anniversary commemorations are so fitting.”