The knarr or knorr ranged in size from 6 meters long, with a crew of three or four, to 20 meters long. A 16 meter boat would have a beam of 5 meters, and a draft of 1 meter; freeboard was about a meter. It might make 8 to 10 knots under sail.
Here's a website with much information on a 16.5 meter knarr, much like the one owned by Thorfinn the Merchant.
A drakken or drakkar is a warboat -- an average one is 28 meters long, and the largest known was 70 meters long. A 23.5 meter vessel would have a beam of 5 meters, and have 24 pairs of oars; a 30 meter vessel would have 30 pairs of oars.
Lots of pictures at Vikingship.com