Shaun Clark and Aled Summerhill were first on the mark for the North who led 14-0 at the interval. The pair crossed in the 14th and 21st minutes respectively with Sam Withers converting both. Thereafter, it was a straightforward afternoon for the hosts with centre Sam Edwards and Matthew Jeczalik touching down before the hour and replacement wing Grant Davies and back rower Jamie Allen completing the rout. Withers added two further conversions while Sam Hutchinson and Jarrod Evans adding one apiece.
RGC 1404 had their moments after the interval and were deserving of their two tries - the first from Emyr Gwynedd and the second from captain Rhys Williams. Osian Jones converted both.
Blues North team manager Nigel Way said; "We had a decent win up at Leicester last week, but we were certainly not getting carried away with that. However, the boys came into the game with some confidence and to their credit, I think they did okay. "
Up the road at Merthyr, the Blues were 36-0 to the good at half time with Cory Allen crossing for three tries and Rhys Patchell adding the extras. Lewis Young scored the first of his two after 24 minutes and Lloyd Chalke added a fifth as last season's champions pressed home their authority.
Rhys Evans added a sixth, Bradley Thyer a seventh, straight after the interval, and as the North struggled to contain, Young added his second and Ellis Jenkins, Ben Roach and Owen Jenkins numbers nine, 10 and 11.
Patchell converted two more for good measure with Garin Thomas adding two of his own. Like their under 16s, RGC 1404 never once dropped their heads and against a heavier Blues pack, they scored three tries of their own through Lewis Barker, Andrew Oakden and Mike Jones. Barker converted two and kicked a penalty and Alex Schwarz kicked a late conversion.