Ormen Friske's catastrophe clarified after 54 years: improper keel design and construction was a death sentence even under moderate seas
A technical investigation by Martin Braun
The Swedish Viking ship Ormen Friske, a replica of the famous Gokstad ship from the 9th century, was underway on June 22 1950 from the Elbe estuary in Germany to Rotterdam in the Netherlands, when it was caught in a storm on the North Sea and broke apart. All 15 crew members lost their lives.
See also: ship and crew two days before the disaster when passing through the Kiel canal: Dok 1 and Dok 2.
to the descendents of the builders and the victims, both of whom have a right to know
to all present and future Viking sailors
|Viking ships of the Gokstad type
are low longships, which were made to fit both the open sea and shallow
inland waters. The Viking, the first Gokstad replica, sailed from
Norway to Chicago and New Orleans as early as 1893. The modern Norwegian
Gokstad replica Gaia launched in 1989 crossed the Atlantic several
times and even survived a hurricane (winds over 70 knots).
The Ormen Friske disaster has been considered unexplained until today. Her loss first became known, when the two main wreckage pieces were found near the North Frisian Isles, the stern section off Pellworm (photo above on the right) and the foreward section between Amrum and Sylt.
Three possible causes of the accident have been discussed:
Concerning hypothesis (2) there was no evidence on the wreckage pieces, such as paint remnants or twisted timber at the break points. Hypothesis (3) is solely based on a fisherman's testimony, which appears unreliable for a number of reasons and which must be rejected simply on the grounds of technical evidence. Hypothesis (1) was widely discussed in the press directly after the accident; however, it has remained an open one, because the Swedish authorities declined to investigate the accident.
Newly available photos, which had been taken of the wreckage pieces just a few days after the accident, prove that hypothesis (1) had been the correct one. They show at which points the ship broke apart, and they also show the directions of the breaking forces that were at work. They further demonstrate that the cause was an extremely weak point in the keel, which was situated at a particularly sensitive place: the sternward edge of the keelson (mast foundation). This artificial break point was evidently built in by unprofessional craftsmanship during the boat's construction.
|Ormen Friske was built in the spring of 1949 in Stensund (25 miles southwest of Stockholm) within the extremely short period of six weeks. For the massive timber pieces the builders did not use strong naturally grown oak, as in the original, but laminated planks of much weaker knotty pine that had been glued together in layers using adhesives available at that time. The 21 meter long keel (photos on the left and below) was made of eight such layers of planks, which moreover were of insufficient length and thus were pieced together end-to-end.|
|Photo above: The foreward section a few days after the accident, docked up in the port of Hörnum on the North Frisian Isle of Sylt. The sideboards had broken off, and the loose deck planks all had disappeared. But the lower parts of the ribs, and the beams above them, have remained intact. Aft of the mast hole, the following ribs are missing: #1 and #3 on the port side, and #2 on the starboard side. The large piece that is lying loosely on top of the wreck is the starboard side of the mast fish. It was originally above the keelson, which is the massive middle piece containing the mast hole. The keelson is situated directly above the keel, and below the after end of the keelson one can see the break edge of the uppermost of the eight glued planks that formed the keel.|
|Photo above: as previous one. The
loose starboard side of the mast fish is here repositioned above the keelson,
roughly in its original position. The photo shows at which points the hull
a) bottom boards outer starboard side: break edge at rib #1 astern of mast hole,
b) bottom boards, inner starboard side: break edge at (missing) rib #2 astern of mast hole,
c) bottom boards, port side: break edge at (missing) rib #3 astern of mast hole,
d) keel: break edge at after end of keelson.
Because all bottom boards broke evenly at the aft edge of the ribs, there appears to have been a bending motion of the hull around these ribs. Such movements occur routinely, when the ship has turned away from the wind (as with a sea anchor) and the sea lifts bow and stern in sequence.
One can conclude that the keel broke first, because of its localized weakness at this point (see discussion below). After that, the ship no longer had a "back bone" in the region of ribs #1 to #3 (astern of mast hole). Subsequent lifting motions by the sea were thus bound to break the bottom boards at these ribs.
|Photo above: as previous one. Top right: the loose mast-fish piece. Left of it: after end of keelson. Further to the left: rib #2 (aft of mast hole) on the port side. Beneath, at picture's lower margin: break edge of bottom boards at the position of (missing) rib #3. Below the keelson, one can see seven of the eight stacked and glued keel planks. The lowest plank is only visible in the next photo. The top plank, which lies adjacent to the keelson and which is a bit broader than the others, has been ripped apart precisely below the keelson's after edge. Plank #3 (second from the bottom in this view) reveals a clean, cylindrical void as would appear from the complete removal of a large knot in the plank. (Right and left of the keel there are poles lying on the ground in the port of Hörnum, which have no relation to the wreck.)|
|Photo above: as previous one. Detailed
picture of the keel break, taken from astern on the starboard side. First,
it should be noted that low quality timber was used, as shown by the number
of knots. When counting bottom up, planks #2, #3, #4, and #8 are ripped
off at the same point on the keel's length.
Planks #2, #3 and #4 have not only broken at this same point but also have split lengthwise foreward, causing plank #4 to partly separate from its abutting neighbor. Significantly, planks #1, #4, #5, #6, and #7 have joints at nearly the same point on the keel's length. This means that structurally only three planks, #2, #3, and #8, held together the keel at this point.
The immediate vicinity of these joints below the after end of the keelson (see previous photo) determines that the keel assembly would be particularly stressed here by the mast:
a) by the mast's vertical force upon the keelson and keel through the weight of the mast and the tension of the rigging, and
b) by bending motions of the keel and the hull around the keelson's after edge due to the mast's forward pull on the stern rigging, as long as the ship was under sail.
The inevitable consequence of these conditions was that the keel was doomed to rip apart even in moderate waves, perhaps when they reached a height of 2 meters. The photo indeed shows no signs of a fracture by impact or twisting forces, as might have occurred in case of a collision or ground contact. Instead these photos reveal a clean pulling apart, caused by tension in the direction of the keel's length, which occurs with every wave, and which is illustrated in the following moveable pictures.
|Lifting of bow or stern causes tension in the keel. If there is an extremely weak point amidships in the keel, as in the case of Ormen Friske, it will be ripped apart by the pulling forces that arise even with moderate waves. Forces of the mast put further stress on this weak point via the keelson (KS), increasing the likelihood that the keel will be broken here.|
|Testimony of one of the six shipbuilders (German)||Thanks to|
|Testimony on alleged effects of bombs on Helgoland (German)|
|Questions concerning liability|
|Interesting websites on Viking ships|