max length for a wooden ship

[JWintjes]

The other day I talked with some colleagues about maximum ship length in wooden ships (of mediterranean construction). Now, we know that the Nemi ships reached 200ft, but these were barges rather than seagoing ships - both the hull form and the general construction would make them unsuitable for proper operation, say, as a warship. Behind this is of course the old discussion about the Hellenistic super warships.

Any opinions (Chuck...? )?

Jorit

[chuck]

I have not done any quantitative studies, so I can only give you general qualitative answers. My qualitative guess is well over 220 feet using just the Greco-Roman practices that we know of. This is because all wooden Atlantic sailing ships of the line of early 19th had reached ~220 feet. Post-Renaissance European carvel built Altantic ships were really structurally much less efficient than greco-Roman Cravel-ships. This is because Post-Renaissance European ships used caulking rather than edge jointing in the hull, consequently the hull planks contributes little to sheer resistance and therefore little to hogging resistance. The hull first, plank edge jointed construction had given Greco-Roman ships had a true monocoque hull that would be capable of superior hogging resistance compared to the caulked but un-jointed planks of frame first Post-Renaissance European Altantic ships. We know hogging formed the barrier that prevented Post-Renaissance European all-wooden ship builders from going above 220 feet or so. So I would venture to guess that if really pressured to increase the size of their ships, by increasing the depth of the hull but still using their familiar hull first, edged jointed carvel hull construction technique, Greco-Roman ship builders ought to be able to reach significantly greater hull length than could Post-Renaissance European all wood Atlantic ship builders.

BTW, this is recognizing that Post-Renaissance European carvel built Altantic ships were structurally much more massively built than known Greco-Roman ships. But I don't think anything stands in the way of Greco-Romans adopting equally massive frame and hull timbers as well without having to make any fundamental changes to their construction techniques.

The technique of using a strong cable to put the hull in compression and suspend the ends of the hull against hogging was also used by the classical Mediterranean ship builders starting with the Egyptians and going all the way to Romans, but not used again in Post-Renaissance European ship building. This is also an effective method to overcome hogging. So this also would tend to increase the maximum hull length achievable with classical mediterranean construction compared to the 220 feet that limited post-Renaissance European Atlantic ship building tradition.

There may also be large ship building techniques used in classical Mediterranean that we don't know about. Specifically Internal structural bulkheads comes to mind. Chinese junks used internal structural bulkheads to greatly increase the strength attained by junks. There are traditional accounts of junks much larger than 200 feet. Really. there is absolutely nothing in internal structural bulkheads that would put it beyond the technical capabilities of classical Mediterranean ship builders.

[HMAS]

& this
http://www.worldwideflood.com/objection ... apable.htm
Chinese Junks
Then there were the sea going Chinese junks of the 1400's. Zheng He's treasure ships had a length of 444 chi (Chinese foot) which, by the Ming gong bu chi = 450 ft, Huai chi = 494ft, or at the very least a shorter shipbuilding chi = 390 to 408 ft. Like most Chinese ships of the day, they were quite wide for their length - a ratio of 44:18 zhang (=10 chi). This makes a very large vessel by anyone's reckoning, entirely of wood with metal fastenings, and it sailed the open sea as far as Africa. (Ref 3. p80). The sheer scale of the vessels (40 percent longer and 65 percent wider the best Western efforts) have been too much for the Euro-centric scholars, with claims the Chinese scribes were exaggerating. Some, like Richard Gould (ref 4) suggest they were "a grandiose dream" or "perhaps...the ships...were built...but never sailed." The unearthing of a rudder post in the same Ming shipyards in 1962 lends support to the credibility of the figures. The scale of the 36ft long and 1.25 ft diameter post calculated by Chou Shih Te using accepted formulae to a vessel length of 480 to 536 ft. "The discovery of the rudder post shows that the Ming texts are not 'spinning a yarn' when they give dimensions at first sight hard to believe for the flagships of Cheng Ho's (Zheng He's) fleets. (Ref 5). More recent work by Professor Xi Long Fei of Wuhan University of Technology, who has written extensively on the subject, is currently being translated. (Ref 6).

These 2 cases demonstrate what can be achieved in timber. Both Greece and China were known to have used mortise and tenon strake jointing unknown or ignored in Europe. In fact the Greek workmanship was more like 'furniture joinery' than the rough work of later shipwrights. (Casson Ref 2). It has been suggested that no timber ship ever repeated the technical perfection of the best triremes, which flies in the face of the evolutionary 'upward and onward' theme, but fits very nicely into the Biblical worldview.

Yet the feasibility of Noah's Ark does not stand or fall on the historicity of these examples. The ark was different in many respects. However, it is worth noting that there were 4 separate times in history when shipwrights attempted the largest timber ship ever, and in every case they achieved a fairly similar scale - somewhere near 400 feet long. The problems with the large ships of the late 1800's do not disqualify the ark, but indicate that we are working near the limit for a timber hull. So the imagined need for steel in a hull over 300 feet might be just that - imaginary.

then of course this http://www.1421.tv/pages/evidence/index.asp
tony

[JWintjes]

The hull first, plank edge jointed construction had given Greco-Roman ships had a true monocoque hull that would be capable of superior hogging resistance compared to the caulked but un-jointed planks of frame first Post-Renaissance European Altantic ships.

Hm. The monocoque hull argument is quite convincing. I wonder, though, why Caesar stresses that the ships of the Venetian, which by all accounts are built in the Celtic (ie frame first) tradition, are better suited for sailing the Ocean. Obviously hull shape comes into it, which is also why they are so difficult to board, but he also explicitly states that they were of a particularly firm construction (tanta in iis erat firmitudo) in the context of being able to weather a storm, which would suggest not only an advantage coming from a higher hull, but also from a sound structure.

We know hogging formed the barrier that prevented Post-Renaissance European all-wooden ship builders from going above 220 feet or so. So I would venture to guess that if really pressured to increase the size of their ships, by increasing the depth of the hull but still using their familiar hull first, edged jointed carvel hull construction technique, Greco-Roman ship builders ought to be able to reach significantly greater hull length than could Post-Renaissance European all wood Atlantic ship builders.

Ok. Obviously, the number I'm ultimately after is in the region of 420 feet. Of course, all these observations are probably also valid when researching that Academy ark model...

The technique of using a strong cable to put the hull in compression and suspend the ends of the hull against hogging was also used by the classical Mediterranean ship builders starting with the Egyptians and going all the way to Romans, but not used again in Post-Renaissance European ship building. This is also an effective method to overcome hogging. So this also would tend to increase the maximum hull length achievable with classical mediterranean construction compared to the 220 feet that limited post-Renaissance European Atlantic ship building tradition.

As for cables, I don't see that many evidence, at least in Hellenistic and Roman warships. Although of course, talking about exceptionally big ships one should probably allow for exceptional engineering solutions, one would imagine that a huge cable might have attracted some attention as a remarkable feat of engineering in itself.

There may also be large ship building techniques used in classical Mediterranean that we don't know about. Specifically Internal structural bulkheads comes to mind. Chinese junks used internal structural bulkheads to greatly increase the strength attained by junks. There are traditional accounts of junks much larger than 200 feet. Really. there is absolutely nothing in internal structural bulkheads that would put it beyond the technical capabilities of classical Mediterranean ship builders.

That is indeed an interesting thought. Internal bulkheads seem to be not that commonplace in galley construction, though; I wonder what the effects on the internal arrangements would be.

By the way, has your polyreme project made any progress?

Jorit

[chuck]

Unfortunately years of working on riggings burned me out. So the polyreme project, along with the Victory and the Soleil, are both currently rotting in their building sheds awaiting a better day. The polyreme actually currently consists of 2 unopened Zveda boxes. I imagine I will return to them sometime by the second half of this year.

I don't know the evolutionary history of north western European ship building from 1st century BC to about 10th century AD. But later North western European ships may have been clincker built, but they were also monocoque hulls because the overlapping planks are nailed to each other. Indeed they are also built skin first, and would have to have some properties of monocoque to avoid structural collapse before the frames are inserted. This may well have also applied to 11 centuries earlier when Caesar saw their ancesters.

Regarding the trick of using cables to stay the ends of the ship, Egyptian use of it on small as well as very large ships is well attested to, including aboard Hesepusut's obelisk transport. It is also used in the biremes and triremes of Greek and Phoenician origin. I may have overreached myself when I said they definitely were also used in later large Hellenistic and Roman ships. However, I see no reason why it would be abandoned in a continuous ship building tradition, since it is a very light and effective means of increasing the hull's hoggin resistance.

So what caused you to emphasize the 420 foot figure?

[JWintjes]

Unfortunately years of working on riggings burned me out. So the polyreme project, along with the Victory and the Soleil, are both currently rotting in their building sheds awaiting a better day. The polyreme actually currently consists of 2 unopened Zveda boxes. I imagine I will return to them sometime by the second half of this year.

Ah, sorry to hear so. I'm sure though you'll finish all three of them before the ice caps melt...

I don't know the evolutionary history of north western European ship building from 1st century BC to about 10th century AD. But later North western European ships may have been clincker built, but they were also monocoque hulls because the overlapping planks are nailed to each other. Indeed they are also built skin first, and would have to have some properties of monocoque to avoid structural collapse before the frames are inserted. This may well have also applied to 11 centuries earlier when Caesar saw their ancesters.

Yes and no. North Western ships from the 6th century onwards were built skin first, in a building tradition that was fundamentally Skandinavian. Celtic shipbuilding tradition however knows ships built frames first, something that disappeared around the 5th century. The Guernsey ship would be an example for that. Although Caesar's account is not totally clear, t is plausible to assume that the Venetian ships were built in a similar way.

Regarding the trick of using cables to stay the ends of the ship, Egyptian use of it on small as well as very large ships is well attested to, including aboard Hesepusut's obelisk transport. It is also used in the biremes and triremes of Greek and Phoenician origin. I may have overreached myself when I said they definitely were also used in later large Hellenistic and Roman ships. However, I see no reason why it would be abandoned in a continuous ship building tradition, since it is a very light and effective means of increasing the hull's hoggin resistance.

I think you're right on that. I might have to look into super freighters (corn or obelisks), perhaps there is some evidence for that.

So what caused you to emphasize the 420 foot figure?

As a side project I'm currently working on a paper on the 40 - which according to Casson was 420 feet in length; although it seems to be rather common to accept his model of a huge catamaran, I'm still quite sceptical about that.

Jorit

[chuck]

Hmmm, the 40 was probably not intended for the Atlantic or even a breezy day in the Mediterranean, so her structural strength need not be in the big leagues. Furthermore she doesn't need to stow large amounts of cargo or provision, so it may be possible to selectively ballast her hulls in such a way as to reduce the hogging stress on her hull. Additionally, as a catamaran, she would have very high stability, and may be able to support very large reinforcing structural trusses high over her decks, or possess extremely deep hulls, in order to increase the structural stiffness of the hull beyond what can be achieved within stability constraints of a monohull vessel. Basically, the outer limits of structural possibilities facing a calm weather catamaran designed by some clever and innovative (but still reasonable) designers are probably not easily extrapolated from those facing smaller conventional vessels designed to be adaptable to a variety of sea conditions and uses.

I think people who argues that it would not be possible to build such a 40 are probably thinking a bit small and along limited number of avenues. But I won't put my name to the 420 foot figure. Only it is possible to build very large.