According to the MTA:
F Coney Island-bound trains run via the from Roosevelt Av to 47-50 StsWe had the past 5 weekends in a row of Roosevelt Island F Train service to and from Manhattan.
Weekend, 9:45 PM Fri to 5 AM Mon, Aug 28 - 31
No Coney Island-bound service at 21 St-Queensbridge, Roosevelt Island, Lexington Av/63 St and 57 St.
F Trains run local in Queens
According to the Roosevelt Island Operating Corp (RIOC):
Please be advised that the MTA has issued a weekend service advisory for the F train, which may affect travel plans. The Tram will run on a rush hour schedule from 7:00 AM until 10:00 PM to accommodate any increase in traffic. Please plan your travel accordingly and visit mta.info/weekender or call 511 for more information.
For electronic updates on F Train service, sign up for MTA Alerts at mymtaalerts.com.