DISTANCES AND DURATION
OF VOYAGES
Distances:
Sunda Strait to Southern Maldives: Approx. 1600 n.m.
Maldives to Northern Madagascar: Approx. 1300 n.m.
Assuming that the voyaging route to Madagascar was via
the Maldives, a reasonably swift vessel could expect to
make each leg of the voyage in approximately two
weeks in the southern winter months when good
southeasterly winds can be expected. However, a period
of calm can be experienced at any time of year and
provisioning for three-four weeks would be prudent. The
Maldives would provide limited opportunity for
re-provisioning. It can be assumed that rice sufficient
for protracted voyaging would be carried from Java.
| Component |
Calculation
basis |
Amount |
Weight |
Volume |
| Water
for drinking and cooking |
Thirty
persons, twenty-five days, not less than 2
litres per person/day |
1500
litres |
<2
tonnes
including containers, |
approx
33m
|
| Ships'
compliment |
Average
50kg per person
Sleeping space 1.6m x 0.45m for 25 persons |
|
1.5
tonnes |
182m |
| Rice |
Thirty
persons, sixty days, 0.5kg per day |
|
900kg |
approx
1.53m |
| Firewood
for cooking |
A
fire would be kept smoldering at all times
when a stronger fire was not required |
|
~1
tonne |
23m |
| Other
foodstuffs etc. |
Salt
fish, plantains, tubers, tamarind, |
|
~0,5
tonne |
0.53m |
| Cargo |
Approx
2 tonnes of spices and other high-value
commodities |
|
~2
tonnes |
43m |
| Other |
Personal
belongings, e.g. sleeping mats, tools; spare
ship's gear; |
|
~0.5
tonnes |
23m |
The total stowage space indicated by these
approximations is 13cubic metres. The weight calculated
is approx 8.5 tonnes. Depending on design, the vessel
might also need to carry a tonne or two of ballast.
Approximately 18square metres of sheltered space would
be required for most of the ship’s company to sleep. It
is assumed that some persons would be on watch at all
times.
MAXIMUM SIZE OF OUTRIGGER SAILING VESSELS
There are vessels without outriggers depicted at
Borobudur but the five large vessels depicted in detail
all have outriggers. The Borobudur ships appear to be
fairly large. Sizes up to 25m have been posited for the
largest example: Erp 6. Heide (1929) offers a more sober
estimate of 12-15m based on the number of oar ports.
This allows about 1m for each oarsman.
In recent decades some very large outrigger vessels have
been built in Indonesia and the Philippines.
However, these are not sailing vessels — they are
motorised and use multiple stays to hold up the
outriggers. Sailing vessels impose much more load on
their outriggers and outrigger booms. The largest
sailing outriggers of recent decades have been the perahu
sande and perahu pangkur of the Mandar people
from the west coast of Sulawesi, and some very large jerangkat
built on the western coast of the Gulf of Bone and used
as FADs (Fish Aggregating Devices) anchored in very deep
water to the south of the Gulf. These vessels have been
up to about 10-11m length and the largest pangkur
have been able to load more than 5 tonnes.
In the first half of the 20th century, outrigger perahu
paduwang from Madura were probably slightly larger
than the vessels mentioned above. However they seem to
have regularly employed human ballast on the weather
outrigger to enhance stability.
|
Perahu pangkur
|
The largest pangkur, sande and
jerangkat had very large and long bamboo
outriggers. Pangkur and sande usually
have outriggers more than 150% the length of the
hull. They normally depended entirely on
outriggers for stability and sometimes made fairly
long, open-sea voyages.
The maximum size of pangkur, sande and jerankat is
probably determined by the maximum size of bamboos
available. Since the sail area that imposes
heeling loads increases as the second power of the
length of the vessel, the volume (buoyancy) of the
outriggers, needs to increase at the same rate. |
| In other words the
diameter of the outriggers must increase in
proportion to an increase in hull length. This
leads to engineering problems as size increases:
if the length of the outriggers increases in
proportion to the hull length, the long projection
of the outriggers forward of the forward outrigger
boom is increasingly susceptible to breaking off
when pitching into a headsea. |
A Selat Badung jukung with a 6m
long hull has outriggers 9m long, mean diameter at least
125mm and buoyancy of about 100kg. (0.0625 x 0.0625 x p
x 9m = 0.1103m) Using these proportions and assuming
that the largest bamboos would have diameter about
200mm, the largest possible outrigger canoe is about 10m
long. Extrapolating from that calculation, outriggers of
about 300mm diameter with buoyancy of about length of
the hull. They normally depended entirely 1.3 tonnes
would be required by an outrigger vessel on outriggers
for stability and sometimes made a little more than14m
long. Such a vessel, designed with a long narrow hull
would scarcely have the capacity to carry the proposed
passengers, provisions and cargo. Therefore it can be
concluded that it is not possible that an outrigger
vessel, designed to derive all its stability from
outriggers could be built of a size large enough carry
the proposed passengers, provisions and cargo.
The outriggers shown on the Borobudur ships are not
like the long outriggers of the large outrigger vessels
of the 20th century. They appear short and small
relative to the size of the ships.
THE DESIGN AND PURPOSE OF THE BOROBUDUR
OUTRIGGERS
The relatively small outriggers of the Borobudur ships,
with their short projections forward and aft of the
booms would be relatively robust but they would provide
little buoyancy and stability relative to the size of
the ships and their sail area.
Single or double outriggers?
In four of the five Borobudur ship depictions only the
windward side of the vessel is shown. Whether the
vessels are double outriggers with another outrigger on
the leeward side or single outriggers carrying a flying
outrigger on the windward side only cannot be
determined with certainty. However, Erp 10, which has
its sail partly furled, has that sail on the side of the
viewer which suggests that we are looking at the leeward
side. Four of the five depictions show the port side of
the vessel but Erp 9 shows the starboard side so
outriggers are seen on both sides of the hull though not
simultaneously.
|
19th century perahu paduwang
|
Most single outrigger vessels are
designed to tack by “shunting” in order that
the outrigger remains on the windward side when
they change tack. When a vessels tacks by shunting
it reverses direction and reverses ends — the
bow becomes the stern and vice versa — the
steering gear must be shifted from one end to the
other and reconfigured to drive in the opposite
end. Such vessels are necessarily longitudinally
symmetrical — the ends are very similar — and
they have a simple rig usually with the mast
positioned midships.
The Borobudur ships do not exhibit longitudinal
symmetry and do not have rigs that could be easily
reversed. |
| There was a type of a
large single outrigger vessel from Sri Lanka, the yatra
dhoni, which did not shunt. Unfortunately the
last of these fell into disuse early in the 20th
century and it is not known how the yatra dhoni
was operated. The hull form of the yatra dhoni had
enough beam and stability if ballasted to sail
without an outrigger (Vosmer 1993). It seems
possible that the outrigger could be shifted from
one side to the other (with some difficulty) and
that the yatra dhoni was used mainly for
long monsoonal voyages to and from India when wind
direction might be consistent for the entire
duration of the voyage. The name yatra dhoni
means “pilgrimage boat”. |
Single outrigger canoes are used on some parts of the
north coast of Central and West Java. They have a single
outrigger boom and they shift the outrigger from one
side to the other when changing tack. The arrangement is
simple, loose, and temporary in appearance. It is
not suitable for larger sea-going vessels. The Borobudur
ships have three or four outrigger booms of complicated
construction: it does not look like an arrangement that
could be shifted when changing tack.
Large single outrigger, non-shunting, canoes were built
at Macassar, South Sulawesi. These vessels where built
exclusively for racing outrigger version of the double
outrigger jerangkat. They had one very large outrigger
and employed a lot of movable human ballast when racing
(Collins 1936).
It seems unlikely that the Borobudur ships were
single-outrigger craft.
Double outrigger canoes are not widely used on the
coasts of Java but they are more common on neighbouring
islands including Madura and Bali where sophisticated
designs exist.
The Borobudur outriggers have a number of
characteristics that make them significantly different
from the outriggers of sailing canoes of the rig more
recent times.
Length of the outriggers
The outriggers of Indonesian vessels, including those
first depicted by Europeans in the late 16th century,
have generally been similar in length to the hulls of
the canoes they were fitted to. In many cases they are
longer than the hulls.
The Borobudur ships all have outriggers shorter than the
waterline length of their hulls Erp 6 (which appears to
be the largest vessel) has an outrigger only 0.54 the
length of the hull. Erp 8 has the longest outrigger at
0.79 the hull length, it has four outrigger booms while
the other vessels have three outrigger booms.
|
Erp
No. |
Outrigger
length as decimal fraction of hull waterline
length |
|
|
Erp
6 |
0.545 |
|
| Erp
7 |
0.585 |
| Erp
8 |
0.790 |
| Erp
9 |
0.640 |
|
Erp 10 |
0.750 |
On all but one of the Borobudur ships the outriggers
are doubled — there are two outrigger components which
I presume are bamboos, one on the inboard side of the
outrigger boom/connective, one on the outboard side.
Some of the Indonesian vessels recorded by Captain
Paris in the 19th century (Paris 1841, Reith 1992) had
outriggers of relative lengths that fell within the
range illustrated in the Borobudur ships. They were
mostly from the Moluccas and neighbouring regions
of Eastern Indonesia where outriggers have remained
relatively short in more recent times. Light weight
timber rather than bamboo is often used for outriggers
in Eastern Indonesia (in some areas suitable bamboo is unavailable)
and outrigger craft depend on movable human ballast for
stability.
By contrast, in areas closer to Java (e.g. Bali, Madura)
outriggers are usually significantly longer than the
canoe they are fixed to. Typically relatively large and
fast sailing canoes have a crew of only one or two
persons and depend on the buoyancy and hydrodynamic
lift of the lee outrigger for stability.
The shortest outriggers (0.525 relative to hull length)
in a survey of sailing vessels illustrated in the
literature were on a large kora kora from Dorey
off the western end of New Guinea (Paris 1841).
The kora kora had a fairly capacious planked hull
and a length beam ratio of less than 4:1 which could
sail without outriggers if properly ballasted. Most
outrigger craft have a quite different type of hull,
built up from an unexpanded dugout canoe and
therefore of very narrow beam and not suitable for
sailing without outriggers.
Attachment of Outriggers to Outrigger Booms
There are several different ways of attaching outriggers
to the outrigger booms used in Indonesia. In some cases
there are curved timbers connecting the outriggers to
the booms (these are termed “outrigger connectives”
by Haddon and Hornell). Whether there are connectives or
the outriggers are secured directly to the booms, the
outrigger usually lies under the boom or connective.
Alternatively the boom or connective penetrates the
outrigger. On all the Borobudur ships there is an
outrigger attached on the outboard side of the
boom/connective.
| On all except Erp 8 there is another
outrigger on the inboard-underside of the
boom. The booms or connectives (it is not clear
which they are) project below the outriggers. |
Detail from Erp 6 shows outrigger
connectives that project well below the outrigger
|
Volume of the Outriggers
The Borobudur outriggers do not appear large in
diameter. They are shown with diameter about the same as
that of the outrigger booms or less than that of the
booms. This relative proportion probably reflects the
large size of the ships and the upper limit to the
size of bamboo available.
A Borobudur vessel of about 14m length would have
outriggers about 8m in length: if the outriggers were
about 200mm diameter, and the outriggers were doubled
(inner and outer outrigger) the buoyancy of the
outrigger would be about 0.5 tonne which is
significant but not in proportion to the size and sail
area of the ship.
Fairings
Erp 6 shows a fairing on the forward end of the
outrigger. The other four Borobudur ships have no
outrigger fairings. Fairings similar to those on Erp 6
have been used in recent times so that the bamboo
outriggers can cut smoothly through the water. They are
a standard feature of most sailing outrigger canoes.
All the features discussed above suggest that the
outriggers of the Borobudur ships were not intended to
provide stability to the extent that the leeward
outrigger of double outrigger canoe normally does: they
lack volume and therefore the buoyancy to resist
heeling. They are not faired to cut through the water.
The outrigger booms or connectives project below the
outriggers and would cause significant drag to the
detriment of speed and steering if depressed into the
water. Erp 9 shows its lee outrigger apparently flying
clear of the water since the outrigger boom (connective)
ends can be seen projecting below the outrigger.
If it is concluded that the outriggers are not
primarily intended to provide stability another
explanation of their use is required. Like the
outriggers of the 19th century bouanga from New
Guinea, drawn by Capt M. Paris, the outriggers might be
seats for paddlers to propel the vessel in calms and in
martial use. If the outriggers are not designed to be
the vessel’s primary source of stability then the hull
form will not be a typical outrigger canoe hull form.
Instead it will have a broader, more stable and more
capacious hull form.
THE SUPERSTRUCTURES HULL PROFILES
The Borobudur ships all have considerable
superstructures obscuring their hulls. There are
outboard galleries for rowers along the full length of
the hull. In the bow and stern tall screens surround the
stem and sternpost. Heide has proposed that the bow and
stern screens are protective structures for use in
warfare. This seems very likely. Later warships used by
Sulu sea pirates had a heavier timber screen in the bow
to offer some protection from cannon shot.
|
19th C Sulu Sea vessel with bow screen
|
The tall screens seen on the
Borobudur ships would create much windage which
would be detrimental to sailing performance and
might not be fitted to ships engaged on long
voyages. The tall screens are fitted on top of
large through beams and wing-like projections in
the bow and stern. Both the heavy through beams (polangan)
and the wing-like transoms (kopengan) have
been features of some Javanese and Madurese
vessels until the late 20th century. |
| In some examples
those wings support the ends of small galleries (ambeng)
built out from the hull. |
Larger and wider galleries, running the full length
of the hull, were a feature of 18-19th century perahu
lancang.
The galleries seen on the Borobudur ships are large,
enclosed, and exhibit complex structure. Again martial
use is suggested with a need to protect the
oarsmen from spears and arrows.
All the Borobudur ships except Erp 9 have a deck house
with a pitched roof positioned aft of the main mast.
The deck houses appear to be small and are unlikely
to represent all the accommodation space in the ship.
| Hull Profiles |
Stern of perahu kacik showing
kopengan supporting an aft gallery
|
The upper parts of the hulls of the
Borobudur ships are hidden by the galleries and
the bow and stern screens. Four of the five
Borobudur ships have a straight, forward raked
profile to the bow. Erp 9 has a curved, forward
raked bow profile. In Heide’s interpretation,
Erp 7 and 8 both have an external stem. Erp 6 does
not obviously have a stem in the lower part of the
bow, but there is a high prow timber projecting
above the bow screen. Some types of Indonesian
perahu are built without a stem (and also without
sternpost). These include the Javanese perahu
jegongan. None of the Borobudur ships show a
sternpost.
However, very little detail of hull structure is
shown in any of the depictions. |
The Heide traces some evidence of hull shape below
the waterline in Erp 6 and 7. The bows do not show a
cutaway forefoot but in the stern there is a curved,
cutaway heel profile. Again, this is typical of Javanese
perahu design. Indeed the perahu konteng of East
Java when planked up to increase freeboard and cargo
capacity has a profile much like a Borobudur ship.
|
Profile of a planked up perahu konteng
|
Because of the full-length galleries
it is not possible to see the rail of the hull and
therefore the freeboard cannot be judged. However,
it is unlikely that outrigger booms would cross
the hull above the height of the rail. Clearly the
lower outrigger booms pass through the hull;
possibly the upper outrigger booms rest on the
rail. The hulls do appear to have considerable
freeboard and the waterline. It is not proposed
that the freeboard/length ratio measured from the
depictions could be taken as representing the
actual ratio. Distortion, exaggerating freeboard,
is more or less a standard feature of ship
iconography. |
If the hulls do have considerable freeboard, then
they will either have fairly considerable beam to
provide stability or they are narrow canoe like hulls
deriving all their stability from outriggers. But for
reasons given above that seems unlikely.
HULL FORM
Little information about hull form can be derived from
the Borobudur iconography. The bows and sterns appear to
be sharp rather than bluff. The underwater body of the
hull is not shown and the bas-relief does not provide a
fully three dimensional representation that would allow
assessment of beam. Hull form must be inferred from
archaeological data and from critical use of more recent
ethnographic data.
Midships cross-sectional shape
A fairly large number of Medieval shipwrecks have been
discovered and investigated in Southeast Asia. The
vessels discovered at Butuan in the Philippines
illustrate a relatively small and sharp type. A larger
and more capacious type has been identified as a South
China Sea hybrid type combining some Chinese
construction techniques with Southeast Asian hull form
and edge-doweling of planks. A large wreck
discovered near Palembang, Sumatera probably represents
a version of the type with entirely indigenous
structure. All these wrecks exhibit similar cross
sectional shape. They all show hollow deadrise and
fairly slack turn to the bilge. None of the wrecks
include the remains of the topsides (with the possible
exception of Butuan 5). Ethnographic data suggests that
the topsides were flared rather than vertical since
vertical topsides are virtually unknown in the
region. However, if the rowing galleries are fitted
outboard of the topsides, the flared topsides would seem
to interfere with the use of the galleries. |
|
Length-beam ratio, beam-depth ratio
The iconography gives no clear indication of the ratio
of proportions of the hull. As noted above, outrigger
vessels usually have very little beam relative to their
length and depth. Non-outrigger Indonesia vessels very
often have length-beam ratio of about 3:1 and beam-depth
ratio of not less than 2:1. (“Depth” here means
moulded depth of the midsection and has no
connection to draft.)
These ratios produce a hull with very large righting
moment (stability) at low and moderate angles of heel
making outriggers totally unnecessary. Indeed, such a
hull form, when rolling in a beam sea would tend to
immerse and damage outriggers if they were fitted. The
19th century kora kora illustrated by Paris has a
length-beam ratio of 4:1 and a beam-depth ratio of
1.8:1. It is proposed that these proportions be used as
a guide in developing a design for the Borobudur ship
reconstruction. |
|
References:
Burningham, N. 1989. The Structure of Javanese Perahu.
The Beagle, Records of the Northern Territory Museum
of Arts and
References Sciences, 6(1): 195–219.
Burningham, N. and
Stenross, K., 1994. Mayang:
The Traditional Fishing Vessels of Java. The Beagle:
Records of the Museums and Art Galleries of the Northern
Territory, 11:73–132.
Collins, G.E.C., 1936. East Monsoon, Scribner, New
York.
Erp, T. van. 1923. Vorstelling van vaartuigen op de
reliefs van den Boroboedoer.
Nederlandsch-Indië Oud en Nieuw 8:227–
57.
Heide, G.J. van der, 1929. De samanstelling van
Hindoe-vaartuigen: iutgewerkt naar beeldwerken van den
Boroboedoer. Nederlandsch-Indië Oud en Nieuw 12:343–57.
Paris, F.E. 1841. Essai sur la Construction Naval
des peuples extra-Européens. Artus Bertrand, Paris.
Piollet, P. 1995. Equipages et Voiliers de Madura.
Paul Piollet, Ternant.
Reith, E., 1992. le Voyage de la Favorite, Amiral
E. Paris. Editions ANTHÈSE, Arcueil.
Vosmer, T., 1993, The yatra dhoni of Sri
lanka.
Bulletin of the Australian Institute for Maritime
Archaeology,
17.2: 37-42. |
