His daughter finished with a 54kg result in the clean, just under the 55kg national record, but that was still enough for a 99kg total score - beating the former national record for totals by 2kg.
"That's alright, we'll beat [the clean] eventually," said Matthew Rayner.
"We planned it from the secondary schools."
Amorangai Rayner had to face more intimidating competition at the senior nationals compared to the schools event in Petone.
"The junior and senior weightlifters are at the same time, so there was some Under 15's there," said Matthew Rayner.
His daughter was most star-struck to be lifting alongside "her idol" in Pip Patterson, nee Hale, a Commonwealth Games veteran and one of the top women's competitors in the country at 53kg.
As a proud father, Matthew Rayner said his daughter's efforts at her debut senior national event definitely turned some heads.
"Stoked. I think we were happier than she was.
"Because she's so young too, everyone was looking at her weights.
"She got high-fives from the NZ High Performance coaches."
One of the big names to congratulate her was Richie Patterson, the Commonwealth Games gold medallist at 85kg.
Amorangai Rayner will have some club level weightlifting for the rest of the year, before she begins build up to next year's secondary school and senior national championships.
Matthew Rayner said she will also try to earn selection in the NZ Youth team for 2018.
To do so would set a clear pathway for making future Commonwealth and Olympic Games squads.