Mr Strang can usually be found in a quiet little workshop tucked away behind storage containers off Ballantyne Rd, turning out children's puzzles by hand.
He has completed more than 3500 individual puzzles so far.
"It is a hobby. I could build this until I was busy 24-7 but I have got to tell myself, 'Hang on David, you are retired.' So it has basically become a retirement hobby," he said.
He discovered he enjoyed working with wood after building a sailing boat, Apres Vous, which he completed in 1985. He then made a puzzle for his young grandson Finn Fairbairn, who is now 15.
"Finn took it to kindy in Dunedin and the teacher said, 'Wow, what a fantastic fish puzzle. Who made that for you?' and Finn said, 'Grandad.' And they said 'You tell Grandad to bring his puzzles to us'," Mr Strang recalled.
Mr Strang now takes orders for puzzles from child-care centres all over the South Island, except Nelson, which he has yet to visit.
Last week, he finished the first cuts of a puzzle depicting the critically endangered Otago skink (mokomoko), of which about 2000 are left. They live in a Department of Conservation reserve at Macraes Flat, East Otago.
The Otago skink is the 22nd in his current catalogue, which features many "real dinkum" New Zealand scenes and flora and fauna.
"Pam Chapman, the author of Skimpy the Skink [and head teacher at Alexandra Child Care Centre], said to me one day, 'David, you keep coming here with the same old. Do something different.' And I said, 'What?' She said, 'The skink'," Mr Strang said.
So he enlisted the help of Wanaka skink gardeners Jan and Errol Kelly, who gave Mr Strang some photographs. He chose the Otago skink, which is being returned to the Alexandra basin by the Central Otago Ecological Trust.
Mr Strang cuts his puzzles into 10 to 15 pieces because there is a higher demand for simpler puzzles. He uses medium-density fibreboard but would love to use plywood if he could.
"The good-quality ply some of those Scandinavian puzzles are made with - shucks, they are beautiful, but to buy it these days costs an arm and a leg," Mr Strang said.
He uses non-toxic oil-based paints to create the pictures, which are completed after the pieces have been cut.
Each puzzle is unique.
Mr Strang found many puzzle-makers liked to keep their methods secret, so he learned by trial and error, reading books and relying on his previous work experience. His tools include a scroll saw, vacuum cleaner, tracing paper, double-sided sticky paper and paints.
He enjoys helping children to think using colours and shapes as cues.
"Doing puzzles is good for brains. It challenges them to think logically. It helps them to analyse," he said.
Mr Strang has lived in Wanaka for about 25 years and is also a part-time piano and keyboard teacher. Before retiring, he worked mainly in engineering and factory workshop supervision.
