Mycenaean War Galley by Woodrat - 1:48 - Shell first Plank on Frame

[Louie da fly]

The trireme reconstruction Olympias is apparently very tender - she tips over quite easily. This must make it hard to row her in anything except a flat calm. However, using a theoretical reconstruction to prove anything is fraught with risk - the hull shape of Olympias itself is the result of theorising based on fairly scanty evidence and may not necessarily be correct.

 

But it must be a common factor with all galleys no matter what the era - the flatter the angle of the oars, the more efficiently they use the energy of the oarspersons, so the oarports have to be as close to the water as possible - so if they heel they become difficult or impossible to row. Cross-sections of the Byzantine galleys found at Yenikapi in Istanbul are shown at  https://journals.openedition.org/archaeonautica/3684 and perhaps these should be taken into account despite the huge time difference between them and the Mycenaean galleys. Interestingly, the bilge shape seems quite similar - maybe a bit more angled - to that of the bases in Woodrat's photo.

 

 

Steven

[woodrat]

Just a correction to my previous post. Due to my lack of Greek, I misinterpreted the photo showing the hull support. It is actually on Samothrace not Samos. The stereobates on Samos give a measurement of length and width only. However this does not alter the discussion on hull stability. I note that a large number of stone anchors are found in these bronze age wrecks. Presumably one of their functions was as useful ballast to counter the horrid tendency for these barkies to turn turtle (as is illustrated in the Medinet Habu reliefs). I don't think the Uluburun wreck will help us much as it was a merchant sailor. Should I deepen the hull a bit, do you think? Also, the keel plank would be a rather bulky baulk of timber which could help with stability.🤔

Another thought. As there is pottery evidence of the mycenaean galleys being rowed from either top or bottom bank, would they only use the lower bank in calm waters and the upper bank if there was a tendency to heel a bit?

Dick

Edited January 9, 2023 by woodrat

[Waldemar]

 

When it comes to the stability and performance of historic (mainly rowing) vessels of modest size, this item is probably worth at least browsing through. For modelling purposes it may be an overkill as a whole, but perhaps some data in this work will prove useful in your project. It all depends how much formalistic approach one wish to take.

 

Bo Ejstrud (ed.), Seven Boats. Assessing the performance of ancient boats, 2012:

 

Ejstrud Bo - Seven Boats. Assessing the performance of ancient boats - 2012.pdf

 

 

Edited January 9, 2023 by Waldemar

[Roger Pellett]

That’s a really interesting paper that deserves careful study when I have time.  Thanks for posting it.

 

Meanwhile, a hopefully simple explanation of a subject that has confused more than one Naval Architecture student.  We can limit our discussion to Initial Stability or the tendency of the boat to list slightly from an even keel.  This is what makes the boat feel “tender.”

 

There are two forces involved.  These are “vectors” as they each act in a specific direction.  Acting down from the boat’s center of gravity and perpendicular to the surface of the water floating the boat is the weight of the vessel.  Acting upwards from the boat’s center of buoyancy and parallel to the weight vector is the buoyancy force.  According to Archimedes these must be equal.

 

With the boat floating on an even keel, the two opposite vectors lay atop each other.  If the boat is heeled slightly,  the boat’s center of gravity remains unchanged but its center of buoyancy and associated upward vector shifts in the direction of the heel to reflect the new shape of the submerged portion of the hull.  Since the two vectors are separated, the resulting couple formed by the downward weight and upward buoyancy acts to return the boat to its upright position.  The tendency for the boat to return to its upright position therefore depends on how far the center of buoyancy moves when the boat is  heeled.

 

We are used to equating stability with objects where the object’s center of gravity is below the center of the upward force, but except for heavily ballasted sailing yachts this is often not true for floating vessels.  Hull shape that determines the center of buoyancy  therefore becomes an important factor. The center of buoyancy for a boat with a rectangular hull cross section shifts considerably when the vessel is slightly heeled so the hull feels very stable.  On the other hand,  a when a cylinder rotates, its geometric shape never changes so the upward buoyancy force does not move.  Unless the center of gravity can be made much lower than the center of buoyancy the boat becomes “tippy or tender.”

 

The hull cross section that Steven posted above will produce a more stable vessel than a cylindrical one.  One with “harder” bilges will be even better.  On the other hand, with so much of the vessel’s weight concentrated in the rowers well above the waterline it was probably difficult to design adequate initial stability into these hulls.

 

Roger

 

 

 

 

[Waldemar]

 

Indeed. The requirements in this particular case are so contradictory that, in order to verify the correctness of the reconstruction, I would probably require at least basic hydrostatic calculations on a mandatory basis. On the other hand, it is just modelling largely for fun...

 

 

[Waldemar]

 

But perhaps we worry about it too much unnecessarily? For most of the year, the Mediterranean is as flat as a ping-pong table. Only in winter was sailing refrained from in ancient times due to frequent storms. And that's how ships were designed, just for good weather. But if they were caught by surprise by an unexpected storm, whole fleets of hundreds of ships would go down straight away...

 

This is why the classic galleys performed so well in Mediterranean conditions, and at the same time so inadequately in the usually wavey northern waters.

 

 

Edited January 9, 2023 by Waldemar

[Louie da fly]

11 hours ago, woodrat said:

and the upper bank if there was a tendency to heel a bit?

Hmm, interesting question. I can see what you're getting at, but I think the skipper would try to avoid submerging the lower oarports at all - it's impossible to keep the water out, even with leather "grommets" to seal the oarports. Any tendency to heel, and I think he'd head to shore as fast as he could.

 

My first thought was that manning the upper benches when the ship was heeling would move the centre of gravity upwards, making the ship even more unstable. But if they're not on their benches, where would those upper oarsmen be? There's probably not room for them anywhere else. So I think that point is moot.

 

BTW, I studied (Ancient) Greek for a year, so if i can be of help with translation, please feel free to ask.

 

Steven 

[Roger Pellett]

The initial stability of a floating object is not a function of sea state.  A boat with a low metacentric height can be tippy in a flat calm due to the moving weight of the people on board.  The worst loss of life on the Great Lakes of the USA occurred when the excursion steamer Eastland capsized at her dock in the Chicago Harbor.

 

Roger

[Louie da fly]

Granted, but rough seas would surely be likely to cause an unstable vessel to turn turtle more easily by putting the CofG and the CofF further out of alignment.

 

Steven

Edited January 10, 2023 by Louie da fly

[Roger Pellett]

The couple formed by the opposing weight and buoyancy forces always tries to rotate the hull so that these forces are perpendicular to the vessel’s actual waterline.  If the vessel is in a heavy sea traveling parallel to the crest of the wave then these forces will try to rotate the hull until they are perpendicular to the slope of the wave.  The stiffer the hull from a stability standpoint, the more violent this action becomes.  The mathematical measurement of this stiffness is called the Metacentric Height.  I tried to explain this in a non technical manner in post #34 above.  While a large metacentric height makes the vessel stable in still water, it is not necessarily desirable in rough water.  Passenger vessels and battleships were intentionally designed with smaller metacentric heights to reduce motions in rough weather. 

 

Wether the rolling hull actually capsizes depends on the vessel’s Range of Stability, the point where the couple trying to right the vessel disappears.  This is actually heavily influenced by the shape of the upper part of the hull.

 

The tenderness that I described in post #34 caused by a very small or nonexistent metacentric height will not necessarily capsize a vessel.  Often the hull will list until the two forces align and will not tip further.  The danger is that the list will allow flooding through hull openings that are normally above water.  The “free surface” from this unrestrained water further destabilizes the vessel.

 

It’s a surprisingly complex subject and not particularly intuitive.

 

Roger

[Louie da fly]

1 hour ago, Roger Pellett said:

It’s a surprisingly complex subject and not particularly intuitive.

That's for sure. I've tried to get my head around it several times, with little success.

 

Steven

[Waldemar]

 

Yes, and it is not just a question of stability or more generally of the ship's seaworthiness. Classic oar-powered galleys need to be proportionally very long with the smallest possible hull cross-section and at the same time of extremely lightweight construction (like today's Oxford-Cambridge racing boats, for example) in order to be effective. But in choppy waters such a structure would be torn apart in the blink of an eye. Not to mention that it is probably impossible to row effectively using dozens of long and heavy oars unisono in such less than ideal conditions.

 

Apart from the technical considerations, I was most impressed by the descriptions of naval campaigns from the Punic Wars. When caught by the heavy seas, entire fleets with many thousands of lives aboard went bottom at a stroke, often reversing the strategic situation of the parties involved by 180 degrees. Yet, navigare necesse est, vivere non est necesse.

 

 

[Louie da fly]

Yes, the galleys recovered from the Yenikapi excavations are incredibly lightly built - though they were about 30 metres (90 feet) long, their keels are made of timbers only 150mmx150mm (6”x6”), the frames 50-60mm (2-2.5") square and 160-200mm (6"-8") apart, and the planks are only 20-30mm (3/4”-1.2”) thick. However, they are reinforced longitudinally with stringers and wales.

 

And yes, storms sank many fleets, not only in ancient but also mediaeval times, as recorded in Byzantine documents.

 

Steven

[Waldemar]

 

I am terribly curious to see what solution Dick finds and what methods he uses. Steven, with your assistance it will certainly be much easier for him, I think more so than with anyone else's. And more interesting for others.

 

I'm now going to limit myself to just watching rather than actively participating. It's bound to be an interesting project, plus Dick's ability to see his projects through to completion.

 

 

[woodrat]

With great thanks to Roger, Waldemar, Steven and Thanasis. The posts supervening have opened my eyes to things of which I have little ken. My training is biomedical but I have often interfaced with engineers and usually bow deeply to their arcane skill. Somewhere in the dank recesses of my brain a cunning plan is forming which, it can be said, cannot fail. Hopefully then I will not let Waldemar down and produce a model that is, if not  perfect, then at least feasible.

Cheers

Dick

[Louie da fly]

6 hours ago, woodrat said:

a cunning plan is forming which, it can be said, cannot fail.

 

With the level of research and care Dick puts into everything he does, I'm looking forward to seeing the result.

 

Steven

Edited January 11, 2023 by Louie da fly

[Waldemar]

 

3 hours ago, Louie da fly said:

10 hours ago, woodrat said:

a cunning plan is forming which, it can be said, cannot fail.

 

😁

 

Killing! It made my day! 

 

 

[trippwj]

So the big questions - will you will you build it bottom first with sewn planks (as built approach)?

[Roger Pellett]

Based on your previous efforts including the “Credible Hulk,” this should be a show stopper!

 

Roger

[allanyed]

Dick,

Just tuned in and wanted to go a step past the "like" button.  You obviously love the research as well as the building and I would agree that it can be as fulfilling as making sawdust.  Excellent presentation, thank you very much for sharing.

Allan

[woodrat]

Thanks all

15 hours ago, trippwj said:

So the big questions - will you will you build it bottom first with sewn planks (as built approach)?

Thanks all for the encouragement. Big question: was the hull sewn or mortice and tenon. Nobody knows . But we have the Uluburun wreck from the ssame period which is pegged mortice and tenon and  a keel. I have been looking at the Khufu Royal BArge from the Old Kingdom of Egypt, a sewn vessel with a keel plank. This is from a much earlier period but shows how well sewn vessels of size can be made. I think for the first iteration of the hull I will try edge to edge planking with a keel-plank, run it up to the flagpole and see if anyone salutes

Here is the latest sheer

If the upper bank is manned the cowhide, which is suspended from  a longitudinal rail, provides protection from sun, spray and arrows . The oars would project under the free edge of the cowhide.

The lower bank of rowers is seated more medial and less in need of protection except from nasty things dropped on them by the upper b......s!

Cheers

Dick

[Louie da fly]

That's starting to look very interesting, Dick. The cross-section looks considerably more stable in my (admittedly ill-informed) opinion.

 

Have you read "Age of the Galley"? It's a collection of papers on galleys of various eras, including this one IIRC. The issue of protective screens appears in it. I think they suggested it was some kind of wooden lattice, but it's quite a while ago and the rotten local library went and sold the book without offering to sell it to me!

 

Also Prof John Pryor's Age of the Dromon is worth checking out - it contains considerable calculations regarding oar length and angle, and offsets for oarsmen in different banks. He came to the conclusion that the oars of the upper bank should be longer than those for the lower bank.

 

OTOH the builders of the Olympias trireme (IIRC) had them the same length because of issues about pendulums of different lengths having different periods of "swing", so they wouldn't be able to keep in time with each other. Of course that meant the upper bank oarsmen, the thranites, had their oars at a much steeper angle than the bottom bank, the thalamians.

 

Just a few things that might bear thinking about at this early design stage.

 

Steven

[Waldemar]

 

No, there will be no comment from me. I'm just suggesting material that you will or will not use. From the book The Gurob Ship-Cart Model and its Mediterranean Context by Shelley Wachsmann. It's about a model of a vessel found in Egypt, yet identified by Wachsmann as a Sea People's ship.

 

Link to its digital model (showing both remains and reconstruction):

Gurob Ship-Cart Model Digital Supplement - VIZIN - Institute for the Visualization of History, Inc.

 

Sample page:

 

 

And also two illustrations of another model (4th cent. BC?) taken from this work:

 

 

 

 

[Louie da fly]

Very interesting model. That strange swelling at the bow is something I've never come across before. I think the thing is a ship-shaped oil lamp, and that is the oil reservoir.

 

The inscription reads something like "holy/sacred/priest/temple of Athens" possibly "sacred to Athens"?

 

Steven

[Waldemar]

 

1 minute ago, Louie da fly said:

I think the thing is a ship-shaped oil lamp, and that is the oil reservoir.

 

Bingo!

 

 

 

[Louie da fly]

I've had a lot to do with oil lamps, made one or two out of pottery, seen any number of them in Byzantine museums. A bit of an unfair advantage .

 

Steven

[Waldemar]

 

12 minutes ago, Louie da fly said:

The inscription reads something like "holy/sacred/priest/temple of Athens" possibly "sacred to Athens"?

 

That's right, again. There is more about it in the book and it was used to date the model, but I am not sure if it will be needed by Dick. But I would also scan the passage if necessary.

 

 

[woodrat]

Yes, Steven, I have the Age of the Galley and Pryor's tome and have used both. A precis of Shelley Wachsmann's book on the Bronze Age appears in the Age of the Galley. I have also thought that different length oars may be need for upper and lower banks. Also there has to be a way to rapidly ship oars by bringing them inboard. Are the port and starboard rowers offset so that they can shoot their oars across?

A double banked corinthian galley is seen showing the upper and lower banks being rowed out of phase,

From Greek Oared Ships, Morrison and Williams 1968

This possibly supports the differential oar lengths. It would also lead to a smoother progress for the galley and maybe more speed?

 

Waldemar, thanks for that great link to the Gurob model. The egyptian model certainly has features like a Sea Peoples or Mycenaean galley as seen through egyptian eyes. The vertical stanchions are emphasised and are not seen in egyptian ships. The vertical stempost is notable as is the small protrusion of the keel which could not yet be called a ram.. The Erechthion model seems to be an oil lamp but does suggest a shape of the ship plan. Also, note the large through beam on which the quarter rudders would bear.

Dick

[Waldemar]

 

14 minutes ago, woodrat said:

The egyptian model certainly has features like a Sea Peoples or Mycenaean galley as seen through egyptian eyes. The vertical stanchions are emphasised and are not seen in egyptian ships. The vertical stempost is notable as is the small protrusion of the keel which could not yet be called a ram.

 

Hopefully it may be even more interesting for you, as this model is believed to be actually left by the Sea People in one of the fortress they occupied in the Nile delta. I just wanted to make sure you knew of its existence.

 

 

[woodrat]

I think the Gurob ship cart model reinforces the likelihood of there being a keel-plank rather than a keel. There are other useful things. Thanks, Waldemar

Dick