The vessel was built in 1978 by Kerikeri boatbuilder John Clode and is owned by Antonio Pasquale of Russell, a staunch supporter of the trust.
Mr Pera said the boat had been idle for the past five years and Mr Pasquale wanted to see it put to good use.
"He said, 'Go nuts, do something cool with it'."
They plan to leave in July for about four months. AFG is working with established charity OceansWatch, which runs annual "cruises with a cause" to the Solomons and Vanuatu.
The crew of six on Caliph, including one medical professional, will head for Temotu, the Solomon Islands' least developed and most isolated province.
It is believed to have suffered badly in the last cyclone season although information remains sketchy.
The boat will be loaded with medical and building supplies to repair and re-equip the province's health clinics.
Mr Pera said just getting to Temotu would be an adventure. Once there they would have no support so they would need to be completely self-sufficient.
They would return with as much virgin coconut oil as they could carry. The oil is produced by the islanders, who have no other source of income, in a project set up by OceansWatch.
In future AFG plans to run eco-tourism and boat building courses, marketed at international students aged 18-25, to pay for its charity work.
Courses will include a traditional klinker-style boat building school, due to start in January, and a marine adventure school, due to start in September 2016.
