Fourth-placed Sienna Wright of Howth Yacht Club is in a four-way battle for a Youth World Sailing medal in the ILCA 6 class in Brazil.
Just four points separate the top four sailors overall going into Friday's final race.
Roos Wind (NED) took victory in both ILCA 6 female races to lead the competition heading into the final race on Friday.
Wind followed on from a bullet in the final race on Wednesday to make it three on the spin and give herself a small two-point cushion with one race remaining.
The Dutch sailor edged Petra Marendic (CRO) and Wright in the first race of the day before also beating Adriana Castro Nuñez (ESP) and Annalise Balasubramanian (CAN) in the second.
“It was really fun,” said Wind. “It started with 14-15 knots and then building to 20 and for me it was just about having a good start and pushing as hard as I could.
“I ended up winning by a lot so it was really fun racing today.”
It sets up an enthralling prospect heading into the final race, with just four points separating the top four sailors.
Wind sits two points ahead of previous overnight leader Emma Mattivi (ITA), with Marendic a point behind in third and Wright a further point back in fourth.
Four Irish boats and six sailors are competing in Armação dos Buzios in four different classes.
ILCA 6 Male
Ireland's Fiachra McDonnell of the Royal St. George YC competing in the male ILCA 6 class at the Youth Sailing World Championships in Brazil Photo: Heusiaction
Mattia Cesana (ITA) maintained his grip on the ILCA 6 male class ahead of the final race of the competition on Friday.
Cesana extended his lead to 14 points despite an 11th-place finish in the opening race, which was won by Luka Zabukovec (SLO) ahead of Anton Messeritsch (AUT) and Boris Hirtsch (SUI).
The Italian responded with a third-place finish in the second and final race, with Felipe Mallmann Fraquelli (BRA) clinching victory and João Pontes (POR) in second.
That result sees Pontes third overall, six points behind Zabukovec, and tied on points with Hidde Schraffordt (NED).
Ireland's Fiachra McDonnell of the Royal St. George YC regained 19th place from 48 in the male ILCA 6 fleet after eight races sailed.
29er Female
Sarah Jannin and Fleur Babin (FRA) won both races in the 29er female class to close the gap at the top of the standings.
The French pair sealed bullets on both outings to move 10 points behind leaders Ewa Lewandowska and Julia Maria Żmudzińska (POL), who have sat in first place overall for the entire competition so far.
Jannin and Babin sealed victory in the opening race of the day ahead of Malika Bellomi and Beatrice Conti (ITA) and Lucy Leith and Chloe Turner (NZL), before backing that up with another victory, finishing in front of Bellomi and Conti and Marleen Huisman and Anne de Kort (NED).
“It was wonderful on the water,” said Babin. “I had a really nice day. Tomorrow, we hope we can do the same as today.
“We are going to do everything to win and find the last energy in us to win.”
Ireland's Lucia Cullen and Alana Twomey (Royal St. George YC and Royal Cork YC) lie 19th after UFD and BFD penalties scored in races ten and 11 in the 25-boat Female Skiff 29er class.
29er Male
Official results have not been updated since December 13th in the male 29er class. Ireland's 29er European Champions Ben O’Shaughnessy and Ethan Spain of Royal Cork YC and the National Yacht Club were in fifth place after nine races sailed in their 30-boat fleet.
Racing concludes on Friday. Results are here
