Research questions about Sailing Characteristics of an old Cog Ship

Hi,

I am a Post Doctoral Fellow and doing research on an old 15th Cog Ship found in the Netherlands. I have made a reconstruction of the ship (see image below) and we are interested in its sailing characteristics. We use Orca 3D software to perform various hydro-static and stability analysis such as (Holtrop) speed/power analysis, but we have no tools to calculate the propulsion forces by the sails.
I found some information on the website (Horsepower/Sail Area equivalence https://www.boatdesign.net/threads/horsepower-sail-area-equivalence.28551/) about the sail generated forces, but it seems quite general. The Cog ship is a single square rigged boat and I am not sure if the described theory is accurate enough to get a good sail force estimate. We would like to calculate the maximum sailing speed of the ship.
My first question is which forum at boatdesign.net is most suited for this question. Secondly I would like some advice how to approach this question in a (semi)realistic way.
Kind regards, Sander

 

The estimated sail area is 60-80 m^2.

 

Hi Sander, welcome to the forum . .

I think Boat Design, or the Sailboats forums.

You can ask the Moderator to move this thread to the forum of your choice, you can do so by clicking on ‘‘report’’ below any post in this thread, and then post your request to the Moderator in the window that appears.

You can also start a new thread on your prefered subject forum, and then post a link to the new thread here.

Good luck with your Cog Ship research . .

 

It may help to know that in force 4 winds, about 50 Sq. ft. of sail area is about 1 HP. Given the extreme burden that hull form carries, you could surmise slightly less, per sq, ft.

 

Here's a Dutch government article (auto translate to English) about this thread's 1415~1420 built historical topic ship, which was found in 2012 and lifted in 2016.

She's in the special frame in picture 1, and kept wet in pic 2 . . .

 

I don't know how faithfully the Lisa von Lubeck follows the shape of the true cog,but they might be worth speaking to on the topic.

 

I've just looked her up Wet Feet, she certainly looks to be worth a chat for the researchers about her sailing characteristics . .

↓ Lisa von Lübeck​

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There's a in 1994 to 1998 built Dutch reconstruction of a Cog ship from Kampen, which is also the place where in 2012 the one of this topic was found, so I'm sure Sander knows about it, and the ones from Bremen as well, so those are just posted here for general interest...

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↓ Kampen Cog <aka> Kamper Kogge | Website | (these two links are both in Dutch)​

Zwarte Dame - = - Black Lady​

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She seems to be straight downwind motor sailing there ^{Dutch link}, note the direction of the flags, and also note the aft starboard cooling water squirt from the engine . .

It looks like she's going upstream the river IJssel there, with a fresh breeze (± force 4~5 Bft ?) against some current, in front of her home port Kampen, while a lot of rain upstream the river Rhine can cause much more current there than is shown in this picture.

Oh well, that's just something for Sander to research why the engine was running there, and whether she can or can't do by her sail alone under these circumstances, and how they did this 600 years ago with these sailing craft . .

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↓ Bremen Cog <aka> Bremer Kogge​

↓ Ubena von Bremen​

↓ Roland von Bremen​

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At their own websites... | Lisa von Lübeck | Ubena von Bremen | Kieler Hansekogge ^{is the below picture source} | Poeler Kogge | Pommern Kogge | Kamper Kogge |

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Hi,
I would like to move this thread to the Sailboats forum.
Kind regards,
Sander

 

And thanks for all the suggestions. I will contact the different Cogship organisations to get an idea of their sailing characteristics.
The Cogship (as far as we know) is quite a late model and differs quite a lot from previous found ships. I would therefore also like to pursue the more mathematical approach.

 

You can also run the asked for mathematics on an existing Cog ship reconstruction, so you can compare the outcome with performance in reality, and maybe fine-tune the calculation method with this.

I'll quote your post #1 main request to the forum, since I've drifted quite a bit away from that...

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Hi SanderV.
I think we can safely assume that the cog-ship was a cargo/freight-shipping-vessel, especially considering its holding capacity.
Do you know of any other EARLIER Dutch/Danish/German/Frisian ships or small vessels that have been located?
My interests, specifically, are smaller predecessors (I'm assuming ship-building began on smaller scale) to the cog-style-ship, (sail or oar powered; with ruddered or oar-steering) and NOT the typical viking/norwegian craft.
And, if so, could you provide any links or sources you may have discovered in your research?
Thanks much!

 

Then what you are looking for is a "hulk" similar to those shown on many medieval seals ... influenced by Romano-British-Frankish Dark Age shipping built in the mediterranean tradition and the NW european stepping stone between earlier lapstrake and later carval/lapstrake cogs. Try to get your hands on The Evolution of the Wooden Ship by Basil Greenhill.

Hulk (medieval ship type) - Wikipedia https://en.wikipedia.org/wiki/Hulk_(medieval_ship_type)

An important thing to remember about merchant ships of this time is that most engaged in seasonal route sailing (both because of weather and cargos). Working to weather was not a high priority unlike the smaller, less burdensome, vessels of the eastern mediterranean or the coastwise fishing fleets.