A longship is little more than a barge with a primative sail. Raider versions had up to 20 oarsmen on a side and top speeds of 7 knots for an hour.

Size: 70 ft length, 20ft beam, 8ft draft
Propulsion: 100 yards of sail or 2 oarsmen
Speed: 2.2 knots, 25 miles per 10h day.
Crew: 3.
Cargo: 3 tons or 50 passengers.
Hull: 3 inches of oak.
Deck: 4 inches of oak.
Mast: 40 feet from the water line.
Weapons: None.
Ship Qualities: Inland, Merchant
Flag: N/A
Cost and Construction Time: 5,000gp; 3 weeks.