The Norwell Public Library will be open on most Sunday afternoons from January through April on an experimental basis, according to Jeanne Ivas, a library trustee. “It is a trial period,’’ she said. “We’ve had many residents who have requested the hours. Opening on Sunday is not funded as part of our annual operating budget, so we’re trying an experiment to see how it flies. If it is quite popular and lots of people are using the library on that day then we’ll have to look into funding it on a more regular basis.” The library will be open three Sunday afternoons per month and hours are likely to be between 1 and 5 p.m., said Ivas.