A short text on my opinion. On reading this text in detail, it can be seen clearly there is only one outrigger Additionally the outrigger is only kept to windward. Now on first reading this seems very odd, as the boat is limited to which direction it can travel, it can only go one way! However in the region where it sailed the winds were from a stable and predictable direction, and voyages were timed to coincide with favourable monsoon winds. Here again we have evidence that double outrigger canoes (trimaran configuration) were not preferred for open ocean sailing due to the extra strain on the crossbeams that is incurred. The evidence of this ship gives more weight to the idea that Borobodur ship that colonized Madagascar from Indonesia 1000 years ago was a tacking outrigger (a tacking craft with only one outrigger) and not a double outrigger like the Banca or Jukung.
Another small insight to be seen by looking at the model in detail, is that the masts are not on the centerline, instead they are to leeward (away from the outrigger), no doubt this was done so as to reduce the stay angle and thus reduce the compression loadings on the mast... smart hey!
I have put this article up on 27 February 2011. I have contacted Mr Jeremy Green via email at the Western Australian museum, and he has kindly allowed extracts of his article to be published here
What follows is an extract from Mr Jeremy Green's article
In Sri Lanka there exists a number of unique sewn vessels the madel oruwa (Figs. 7-18),
madel paruwa (Fig. 8) and the yatra dhoni, or maha oru (Fig. 16), meaning big outrigger
canoe. The former two vessels, which are still widely used for beach seine fishing, have been
described in extensively by Kapitan and Kentley and Gunaratne respectively. No example of
the yatra now exists, the last example having been wrecked in the Maldives in the 1930s.
Indian-built dhoni still sail in the region (see Fig. 19). However, a model of this type was
recently examined and documented in the Maritime Museum in Galle, Sri Lanka by
Vosmer. This model had originally been in the Kumarakanda Vihara at the port of
Dodanduva. It is said to have been built by a boat-builder, and to be over 100 years old.
Hornell stated that the yatra ranged up to about 30 m in length, but normally about 15-18
m, carrying 25-75 tons of cargo, usually averaging about 50 tons. Mookerji mentions yatra
dhonis being about 18 m in length with a beam of about 5 m. They are sewn craft, planked
from domba (Callophyllum inophyllum), at least 50 mm thick. In recent times the yatra dhoni
was used as a coastal trader and for voyages to India and the Maldives.
The model had been built by a boat-builder and exhibited the hallmarks of his care. For
example, it was noted that the four hooked scarf joints in the keel - stem and sternpost structure
were made exactly as they would have been on the real vessel with tiny locking wedges.
Other elements were also executed with attention to detail: the frame fastenings were roved on
the inside, the sewing together of the planks was detailed, and the general finish of the components
were of high quality. In view of this attention to detail, it was thought that the accuracy
of the model, both in scale and detail would make a fairly reliable source for documentation.
The hull is double-ended, with slack bilges but full midsections. The forward sections
are only just slightly finer than the aft sections, displaying a subtle hollow entry at the bow.
The forefoot is extended forward by a gripe attached to the keel - stem and there is also a skeg
aft to which the rudder is fitted. Both these devices would be aids to lateral stability, helping
to reduce leeway and balancing the helm while sailing. It should be noted that at least one
drawing of a yatra does not show these additions.
The carvel-planked hull comprises wide planks sewn together (up to the level of the
deck) along their edges. The bulk of the sewing is on the outside of the hull, a practice common
to Sri Lanka but unusual in sewn craft of the Arabian Gulf and India. Planking is fastened
to the frames with nails roved on the inside. The frame timbers are large but relatively
few for any vessel. The total sectional area of all the frames, however, is more than adequate
for strength. With the exception of the pairs of bollard timbers near bow and stern, the
frames are continuous, all crossing the keel and running from sheer to sheer.
The beams are also large in section, few in number (seven) and protrude through the
sides of the hull. It is presumed that the edge of the planking is slotted into them in order
to lock them into place, though this cannot be discerned on the model.
A large outrigger is fitted on the port and windward side of the vessel, (according to the
set of the sails); this is similar to the boat from Borobudur (Fig. 20-21). The use of an outrigger
is curious on a vessel that appears to possess a rather stable hull rig configuration.
Hydrostatic analysis of this hull form by Vosmer showed it to be a reasonably seaworthy vessel
even without the outrigger. It appears that the port side was intended to be always to
windward and therefore for trading voyages it would need to utilise the monsoons.
Alternatively, the sea breeze could be worked during the day to move northward along the
western coast, while the southward journey could use the land breeze at night. Voyages to
the Maldives could be accomplished in similar fashion, by using the monsoon winds at
The vessel is rigged as a ketch with square-headed lug sails and a jib set on a short
bowsprit, a rig common to the region of the Indian subcontinent. The arrangement of the
halyards was such that they prevent the mizzen yard from passing around the forward side
of the mast. It must therefore be concluded that the mizzen sail on the yatra was never
tacked, but went aback against the mast when occasionally on a starboard tack. It has been
suggested that the yatra is a derivative of the types of vessels illustrated on the Borobudur