I just received my
Quarterly copy of
"Sea History" (Winter 2016-17). Great article on the
Draken, with pictures.
The Sailing Part: Apparently the
Longship is capable of well over 14 knots.....and getting Scary. The crew was uncomfortable with the way the ship handled at that speed and generally took measures to slow her down. ... Take a reef.

NB
My Take: I wonder if the "StearBoard"-- (Rudder)-- was starting to :
Stall:..Cavitate.. Like the wing of an airplane when it looses lift...effectiveness...Stalls.
When the rudder stalls, the ship will
"Round Up" into the wind with MUCH shaking of the sails and rig..until the helmsman can get the ship back on course...and then if the sails are not trimmed differently..it will happen again.