The Boats of Borobodur

[Dangun]

Can anyone recommend a good discussion of the boats engraved on the Temple of Borobodur, in Java, Indonesia?
I'm spending a week in Yogyakarta and can't find any particularly illuminating references...

[Duncan Head]

You've probably found these, but FWIW:

http://oaktrust.library.tamu.edu/handle/1969.1/153576 - a thesis that you can download
https://en.wikipedia.org/wiki/Borobudur_ship
http://voices.nationalgeographic.com/2015/09/25/the-borobudur-temple-ship-bringing-a-memory-back-to-life/
http://www.swahiliweb.net/ziff_journal_3_files/ziff2006-04.pdf - expedition on a reconstructed ship
http://www.themua.org/collections/files/original/0b14878c9aec955a75254a2c544e675d.pdf - more about the Buddhist tales
http://www.hinduwisdom.info/Seafaring_in_Ancient_India.htm - the Indian connections

[Patrick Waterson]

And perhaps also a glance at Missing Links in the History of Boat Building Technology of India in Marine Archaeology Vol 4, June 1993.

The vessel is incidentally a ship and not a boat: the difference is that a boat heels in the same, and a ship in the opposite, direction to the turn.  Hence a ship turning to starboard heels to port, while a boat turning to starboard heels to starboard.  (This is why all submarines, even 20,000-plus tonners, are 'boats', not 'ships'.)

[RichT]

The vessel is incidentally a ship and not a boat: the difference is that a boat heels in the same, and a ship in the opposite, direction to the turn.  Hence a ship turning to starboard heels to port, while a boat turning to starboard heels to starboard.  (This is why all submarines, even 20,000-plus tonners, are 'boats', not 'ships'.)

That's an interesting definition I hadn't heard before, though I suspect the roll in the turn is more a factor of size, centre of mass, speed, propulsion etc than a simple boat/ship difference. In practice, since smaller vessels tend to have the characteristics producing the inward heel, it's probably true, but then it's just another way of saying 'boats are smaller than ships; ships are larger than boats' which is the usual definition. Plus ships can carry boats, boats can't carry ships, which is the other usual definition - submarine boats having originally been, like torpedo boats, small enough to carry on a ship. Definition of ship types - especially in the age of sail - is a wonderfully arcane subject. I wonder if submarines do heel into the turn - when surfaced or submerged?

And a bit more on topic - how can you tell which way this vessel heels in a turn?

[Patrick Waterson]

I suspect the roll in the turn is more a factor of size, centre of mass, speed, propulsion etc than a simple boat/ship difference.

That is basically what contributes to heeling behaviour and hence provides the distinction on which the rule-of-thumb definition was based.  In the Age of Sail there was of course 'ship rig' (three masts and square/rectangular sails) as opposed to ketch, schooner or sloop rig, not to mention brig, barque, brigantine and barquentine rig, but that was essentially definition finessing by style and type which does not affect the basic behaviour distinction.

I wonder if submarines do heel into the turn - when surfaced or submerged?

Both.  Ask anyone who has served in submarines.

And a bit more on topic - how can you tell which way this vessel heels in a turn?

The re-enactment crew refer to her as a ship consistently throughout.  They sailed on her - they would know.

[RichT]

I wonder if submarines do heel into the turn - when surfaced or submerged?

Both.  Ask anyone who has served in submarines.

Surprisingly enough, I don't know anyone who has served in submarines.    I wondered if there was documentary evidence. Hold on - Google to the rescue.-

Submarine Hydrodynamics by Martin Renilson, p.55

Or this: http://ocw.mit.edu/courses/mechanical-engineering/2-154-maneuvering-and-control-of-surface-and-underwater-vehicles-13-49-fall-2004/lecture-notes/lec7.pdf

7.3.4 Heeling in Submarines with Sails
Submarines typically roll into a turn during all phases. Unlike surface vessels, which have
the rigid mass center above the center of fluid forcing, submarines have the mass center
below the rudder action point, and additionally feel the effects of a large sail above both.
The inertial equation
(m − Yv˙)v˙ − (Yr˙ − mxG)r˙ = Yνζ
is dominated by mv˙ (acting low), −Yv˙v˙ (acting high), and Yνζ (intermediate). Because
v˙ | | > m, the vessel rolls under the sail, the keel out of the turn. In the steady state,
−Yvv + (mU − Yr)r = Yνζ
The drift angle α keeps the Yv-force, acting high, toward the center of the turn, and again
centrifugal force mUr causes the bottom of the submarine to move out of the turn. Hence,
the roll angle of a submarine with a sail is always into the turn, both initially and in the
steady state. The heel angle declines as the speed of the submarine drops

(NB that the 'large sail' doesn't mean what it normally means]

And a bit more on topic - how can you tell which way this vessel heels in a turn?

The re-enactment crew refer to her as a ship consistently throughout.  They sailed on her - they would know.

Surely a sailing vessel will always heel to leeward, regardless of size? In anything but the lightest airs, the force on the sails will outweigh centrifugal force in a turn. I imagine the re-enactment crew had lots of reasons to call her a ship (not least, size), regardless of what happens when turning under sail.

Anyway as rules of thumb go it's fine - as I say I just hadn't come across it before. There's some interesting physics behind it too.

I like facts 

[Jim Webster]

Interestingly in the yard where they build them, each is referred to as 'the boat.'
Whether it's a sub, a mine sweeper or the Invincible 

[Patrick Waterson]

Interestingly in the yard where they build them, each is referred to as 'the boat.'

Although the yard is owned by a shipbuilder ...

Surely a sailing vessel will always heel to leeward, regardless of size?

Unless it is a submarine with a 'large sail'*.   But essentially, yes: the difference shows when other forms of propulsion (oars, paddles, screws, thrusters) are used.

*Or, as we used to call it, a conning tower.

[Jim Webster]

Interestingly in the yard where they build them, each is referred to as 'the boat.'

Although the yard is owned by a shipbuilder ...

Interestingly 'boat yards' are entirely different in scale

[Dangun]

You've probably found these, but FWIW:

http://oaktrust.library.tamu.edu/handle/1969.1/153576 - a thesis that you can download
https://en.wikipedia.org/wiki/Borobudur_ship
http://voices.nationalgeographic.com/2015/09/25/the-borobudur-temple-ship-bringing-a-memory-back-to-life/
http://www.swahiliweb.net/ziff_journal_3_files/ziff2006-04.pdf - expedition on a reconstructed ship
http://www.themua.org/collections/files/original/0b14878c9aec955a75254a2c544e675d.pdf - more about the Buddhist tales
http://www.hinduwisdom.info/Seafaring_in_Ancient_India.htm - the Indian connections

Thanks.
I'd spotted some of them, but definitely not all of them.

[Dangun]

Its pretty amazing how little is written about it, especially considering how conspicuously large it is.