ISAF Youth World champions Lucas Rual and Emile Amoros of France moved into the lead with two bullets for the day. Isaac McHardie with Micah Wilkinson (NZL) sit in second followed by brothers Quinn and Dane Wilson (USA) in third.
Overnight leaders Charlie Wyatt and Tom Siganto of Australia fell to fourth in the lighter winds. Ragna and Maia Agerup of Norway remain the top female team.
Twenty-five nations are representing all continents with 213 entries in this highly competitive fleet.
Qualifying finishes on Tuesday 30 July followed by three days of the final series.
The prizegiving will be held on Friday 2 August.