An investigation of the tidal conditions at the loss of the world's most impressive sailing ship

12 Pages·2009·0.51 MB·English

Small Publications in Historical Ceophysies

No.9

An Investigation of the Tidal Conditions at the Loss
of the World's Most Impressive Sailing Ship

‘Martin Ekman

Summor Institute lor Historical Geophysics
Aland Islands

2002
Small Publications in Historical Geophysics

No.9

An Investigation of the Tidal Conditions at the Loss
of the World's Most Impressive Sailing Ship

Mautin Ekman

Contents

1. Alma sailing shipping and the Llerzogin Cecilie
2. ‘Lhe loss of the Lerzogin Cecilie
3, Character of the tides at the place of loss
4. ‘The tides at the event of the loss
5. Conetusion
References

Summer Institute for | istorical Geophysics
Aland Islands

2002
1, Aland sailing shipping and the Ilerzogin Cecilie

Scafaring has Inng traditions on the Mand Idands, the autonomous
grap of islands in the central Baltic Sea. This tradition extends not only within
the Tallic, bul also internationally. Since 1865 Alundic merchant ships have
crossed the workl's oceuns. During the first hulf of the 20th century Gustaf
Lirikson at Matieharan, the capital of Aland, built up a lect of greal deep-sca
saiEng ships, mainly for the wheat trade between Europe and Australia, This
put Aland in the remarkable position of having, Ihe world’s largest fleet of
inerchanl sailing ships; see furthec KShre (1948), Cireenbill & blackman (1986)
and Kahre & Kéhre (1988), ‘this was, according to Geeenbill & Jackman,
“made possible by the nature and history uf the pecaliar community in which
they were owned, « Sweuish-spealsing archipelago society which averaged
23,000 Inhabitants spreacl over some fitty islands, a distinctive minority group
[inside Finland}!

The sailing vessely not only brought money into the Aland economy but
also were a part of the Alandic culture. In audition, these ships attracteat a lat
of international attention because of their impressive beauty. ‘The most
inypressive and hewutitul of them all was the Llerzogin Cecilie (‘Duchess
Cecilie", the flagship of the Aland sailing fleet

The Llerzogin Cecilie was bought by Gustaf Eriksen in 1921 from the
Krench state, France had, after the ond of the frst world war, ablained the
vessel ay a war Teperalions payment [om Germany. Germany had originally
built the vessel in 1902 as an imperial ship, named afler the empress-in-be, the
Duchess Cecilic of Mocklenbng, Tt-was a fomr-mastad barque, 102 m long and
60 m high, sith 35 salle; sce Figure 4. The totsl area of the sails amounted to
4050 m?. Gusla? Frikeon had this magnificent ship repaired and put itin on the
‘wheat trade lo Australia; see Dethy (1937) and Greenbill & Hackman (1991) for
details.

‘The ship usually travelled, as the other vawsels om the wheat trace, from.
Aland across the Atlantic Ocean and the Indian Ocean lo Australia, Tacre
wheat was loaded. Than the ship croseed the Pacific Ocean and the AHantic
Ocean to go to England for discharge, The different routes were chosen to
make use of the dominating winds aul wea currents as z1uubt as pussibie.
After that there was often a possibility for a brief visit home to Aland, until it
‘was time for the ext freight. The whole voyage around the globe normally
took clase to ome year
Figure 2, Herogin Cecilie (Irom Villiers, 1972)
2, The loss of the Herzogin Cecilie

In 1986 the Herzogin Cecilie was lost by stranding itt the English
Channel. Lhe vessel had almost completed that year's voyage tv and from
Australia, ‘Lhe load consisted of nearly 5000 tons of bagzed wheat Mester an
board was sea captain Sven Frilesson, and officer on watch was chiaf male Flis,
Karlsson. The crew consisted of 0 man. The lass haa been exlensively reported
and discussed by Derby (1937) and Greenhill é Hackman (1994), 2n the latter
book with maritime inquities included. The captain's wife, 20 was ont board
during the whole voyage, as well as the mate have written books about the
voyage (Lriksson, 1958: Karlsson, 1964),

The ship, arrivirg from Australia, had first reached Falmouth at. the
sonth coast af Fngland. These arders were given to go ta Tpswich op the cast
coast. Cansoquentiy one continued castwarels in the English Channel, now in
Joggy weather. “finr some eight hours, at (8 $5 on Saturday night the 25th of
Aptil, the shig went ashore int thick fog. ‘Lhis huppetted at the cock of Hausa
Stone west Gf the peninoula of Bolt Lend, neur Scleombe southeast of
Plymouth; see Ligure 2. Lalf an hour later the ship yeas taken afloat by the
rising tide and Urifted further towards fara, going ashore un the souks there
instend, Distresy rockets were fired, and che crew was taken ashore by a
fifebvat. ‘The vessel was gradually filled by water, and later on, in spite of
attempts to bring aboutsulving, it was broken in a storm:

The event caused considerable excitement, especially of course on Aiand
and in Fngland. Fngiish people came in enormous crowds to see the famous
sailing ship im ils Gragic position. Trom che ship one suceeded in salving,
among other things, Ihe captain's saloon including furniture, which was
fransparied to Marichamn and nowadays form a part of she Aland Masitime
‘Musoum. The captain and the mate ceased sailing afer fe accident and later
con elt Aland to settle in Attica,

Lhe cause of the loss has not been fully understood. ‘lowever, it can be
said to he a combination of overoptimistic passage planning, some unknown
navigational error, and thick fog. Cme relied in this case entiraly on dead
reckoning, wilhou: con(gol possibilities. a method containing risks for
unfavourable osror propagation in the positianing, This bad the consequence
‘that the ship, instead of going far enough out in the Linglish Channel, went ov
war the coast. While the ship actuafly should have passed far south of the
Peninsula of Bolt Head, il wenl ashore approximately 1/2 raulical mile north
‘west of the southern lip of the peninsula. Tic crew dic not know Fron where
they were.
%

{gure 2, The place oF ase in the Taiglish Channel (at the arrow)
Loose speculations on the tides having contributed to the loss were put
forware. alteady at the maritime inquiries in Plymouth a few weckes
afterwarus, buth by the caplain and the mate. 4 vessel that gocs close to land
in a tidal region like the Fingl'sh Channel tates the risk of being influenced by
coastal tidal streams differing from the general lidal streame further out.
‘Computations that may shed Light on the role af tho coastal tides at the loss of
he ship never scem io have been made, We will here try to perform such
computations.

3 Character of the tides at the place of loss

the tides in the Fnglish Channel are, as in dhe North Sea region in
general, pronounced semi-diurnal. This means that the tides are dominated by
the Lumar prinicipal tide Mz with the period 12.4 hours and the selae principal
(ide $2 with the period 12.0 huss; in addition the Junar elliptic tide Ne is
impartan|. The dinrnal main components, Ki, Ovand (1, are vey sina,

To the Ling Channel, as partly also in the Irish Sea, there occurs a
well-known resonance phenomenon in the tides, producing considerable
eigenosuillations of the water mass (see e.g. Pugh, 1987). ‘The resonance period
is dependent cm the length and the depth of the water basin; in the Channel
these quantities yield a resonance peried close to the periods of the somi-
diurnal tides, ‘hws there ere large semi-diurnal tidal variations al lhe onds of
the Channel. At Plymouth near the weslern end, close fo the place of the loss,
the spring tidal renge may amount ta 6 meters.

‘The tides ave mathematically characterized by their harmonic constants,
i.e. by the amplitudes ar and phase lags af the tidal components. The bay of
toss is, in this kespoct, probably best represented by an average of Plymusth
(Pevonport) and River Yealnn Intrance, the principal harmonic constants of
which then became:

Mz c=165m, g= 135°

& 0.60.1m,

XN

Ki 123°
a Qorm, ge 2

PL @4003m,

Llamnenic constanls for Saleambe, en the alher side of Boll Head, have been,
ued for check calculations,
Ih shallow waters nvar the coast of Ghe Boglish Channel - where the
Doight of the Lidal wave is nv longer negligible jn refation in the depth of the
‘water -a spacial tidal effect ucurs, Ht pruduces quarter-diternal ticles, the saint
ones of which ate Knewr: as My, MSi and MIN, ‘these have periods uf a little
more thatt 6 hours, half of thet of the semi-tiurnal pexiod, Lhe ¢pearterdiemmat
tides are nott-linear "overtides’, which are more ditfica‘t to deal with than the
ordinary tidal componenis. They were closely investigated by haber!
dHitres & Le Provost (1970, 197%), using a scaled Aydrauite madel of the
Frglish Channel; this is aowadays replaced by numerical modelling, their
amplitides and phase lage may be given as (frum the POI. data bank)

Ma n= 018m, g- 14
MS 6=009m, y= 197°
MING ar andm, = 112°

Their norclineat character makes them sumetimes nore important then &
quick glance at the amplitudes may reveal; at spring tides the cjuatterdimmal
tidal variation in the vicinily of the place of loss may amount to half a meter.
Linis group of tidal components lurns out to play @ noticeable role in our
computations

4, The tides at the event of the loss

In comection with the tidal oscillations of the water mass in the Fingtish
Channel there occurs @ horizonlal transport of water. ‘Lhis results in the welle
known tidal stream going allernalely westwards and castwards, wilh some
modifications depending on the shape af the coast. The specd of the lidel
stream is in general a few knots. Already Derby (1937) has shown tha this
lidat stream could not to any considerable dogee have contributed to the sbip
Teaving ils planned caurse, even if some driit towards land must Rave taken
place, Greenhill & Haclattan (1991) do not add anything new in that respect, ln
any case, on boar the éhip one should have had knuwledge enoagh fo correct
for such a tidal deviation of the course,

When the ship for various reasons nevertheless had approached Bolt
Head, the tidal si(astion becomes different, In the vicinity of Une coast the tidal
stream lends lo follow the direution of the coast: we will rete to that later,
using a numerical model, Still closer to the coast the tidal stream tends tu be
directed move towards land when the tile is rising, and away from land when
the tule is falling, expecially 4 the coastal area is shallows and irregular. We will
treal this coastal lide now.
There is no detailed information on coastat tidal stream in the area of
the Juss, In utder tv obtain some knovrledge of the veriations of the tel
streains there we will have to resort to a ascful simplification: With good
approximation the speed of the tidal stream #s proporlional lo the rate of Ihe
rise of the Ede, Thus we compute the rain af rise of the lide and use this as a
Kid of moasure of the sirength all the tia’ stream,

The computation has been performed in the following way. ‘Ihe height
UE the tide has been calctfated for a series of times duzing the 24 howrs from.
Apel 2th, 16 00, to April 25th, 16 00, in the year 1986. This time span is
symmetric with respect io the haur af Cae loss, April 25th 04 00. The tidal
computations have been posformed using harmonic constants as described
abore, although mare constants than those listed there have heen applied,

Tor every time interval between the times mentioned the rate of rise uf
the tide has then beer calotlated. ‘The vesult is presented in Ligure 3, in the
form of a continuous curve showing the rate of rise, in cm per minute, as a
function of time, Positive rates imply a vising tide and an in-going tidal stream,
negative rates imply a falling tide and an out-going tidal stream, [t can be
mentivned tht in the entrances to Plymouth and Selcombe: a rate of rise of 1
em per minute corresponds lo a slam speed of abou: 1 kn.

We immediately nola that the carve is somewhat asymmetric: il has a
pointed maximum which also is shifted to the left. The reason for this is the
group of quarler-diurnat overlides descrihed in Section 3. The maximum rate
8 rise amounis io 2.2. em per minute, which oreurs al around D410,

Toro interesting questions now present themselves: How lagge la the
variation during, this day compared to normally? (Where on the curve does the
oss occur?

The first question can he answered by comparing the con:imous cmve
in the figure with the dashed one, showing the cakulaled raie of rise in the
normal case (mean variation). As can be seen, the variation during, the day af
the loss is considerably larger than normal. This is parlly due lo the tide being,
feiiJy close to spring (Combination of Mz and §), but alse lo the moon being
very close tir the perigee of its orbit (combination uf Me atte No), he snercionian
is extra large, because of the influence of the quenter-diumal overtides
(combination of Me MSs and MING).

Tae loss occurred, as earlier mentioned, in twa steps, a ferat steonding at
08 85 and a second ane at about 04 28, "Chey ace matked with arrows in the
figuee. The second queésion whove can, thereby, be answered: ‘The loss
26

ane

ie 3, The vale of vise of the lide, fm re per minuke, during the day of fas
(continuous curve) aad ia the normal cose (dashed curve). The arraws show
when the strandings uccurrel