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-   -   Why did wooden ships never get much beyond 300 feet... (https://www.cruisersforum.com/forums/f47/why-did-wooden-ships-never-get-much-beyond-300-feet-165533.html)

MarkJ 03-05-2016 09:10

Re: Why did wooden ships never get much beyond 300 feet...
 
Because its too long to walk with a peg leg and parrot on your shoulder.

Cadence 03-05-2016 09:21

Re: Why did wooden ships never get much beyond 300 feet...
 
Quote:

Originally Posted by bauer965 (Post 2111979)
To answer the OP, it's mostly economics, not an engineering limitation.
Especially true for vessels enaged in trade, they are truly designed to meet certain service requirements, while making a profit for the investors.
Big isn't always better in maritime trade, depending on the service, and historically (and even in most parts of the world today) ships were also limited in size by shipyard physical constraints, shore-side infrastructure, size / capacity of ports of call, and ship husbandry capabilities. The economics in the age of wooden ships likely led to the conclusion that 4 300' ships made more money than 1 600' ship, for example.
Today, it's simply that a large steel ship is cheaper than a large wood ship, and we always are talking life-cycle costs over the intended service life.

That and one going down would not be as catastrophic. Not the owners probably cared about the crew just the pocketbook.

reed1v 03-05-2016 09:25

Re: Why did wooden ships never get much beyond 300 feet...
 
Quote:

Originally Posted by Dave Lochner (Post 2111963)
An issue with large wooden boats is hogging. There is less buoyancy in the stems, this causes the keel to bow, i.e., the there is a curve in the keel with the ends being lower than the middle.

I assume it could be corrected by increasing the buoyancy in the ends and/or bigger stiffer keel timbers, but those solutions affect performance and add weight and reduce volume.

Then there is cost effectiveness, a big wooden ship requires more maintenance that a similar one of composites or metal.

Hogging occurs as the ship ages. ends sag downward due to less support from the water vs the middle section. Actually occurs with steel ships as well, just not as pronounced. However, most commercial ships are usually designed to last about 20 years in service so hogging is not a relevant issue.

There is no theoretic limit as to how big you could build a wooden ship. Just by the time they were replaced by steel, 300 or so feet was about the max most shipyards could handle. Once you get to overhead cranes, dry docks, and modular construction, virtually any size economically feasible can be built.

Shrew 03-05-2016 09:47

Re: Why did wooden ships never get much beyond 300 feet...
 
Quote:

Originally Posted by jrbogie (Post 2111956)
noah built himself a pretty big boat. so they say anyway. something like forty cubits, whatever a cubit is.

Traditionally the distance from the tip of the middle finger to the elbow.

1 cubit = 1.47637795276 ft
0.4572 meter

Dimensions of the vessel: 300 cubits in length,
50 cubits in width
30 cubits in height

Stumble 03-05-2016 10:09

Re: Why did wooden ships never get much beyond 300 feet...
 
As mentioned hogging, and it's corrilary sagging start to become insurmountable problems when the length of wooden ships excedes about 300'. Simply put the Youngs Modulus simply isn't high enough for the material to resist the flex generated.

It isn't just wave action that is an issue here, turning a 300' long ship exerts tremendous torque loads on the hull, and wood simply isn't stiff enough to resist them. The boat will start to flex and pop seams pretty quickly.

All materials have this issue of course, but the stiffness of other common boat build materials is just much higher. It's the same reason steel ships have a maximum theoretical size of a couple of thousand feet. I am not sure exactly but what I remember is somewhere in the 2,500' range (about double the longest ship ever built) is the upper limit for steel.


Not that good engineering today couldn't probably build a better 300' wooden ship than in the age of sail, but the material limitations still apply.

TurninTurtle 03-05-2016 10:29

Re: Why did wooden ships never get much beyond 300 feet...
 
The size of a cubit changed... because the size of people changed. 5 ft used to be tall.

kentobin 03-05-2016 14:13

Re: Why did wooden ships never get much beyond 300 feet...
 
I've talked to a wooden boat surveyor and it's not just the fact that the wood flexes but if there are continual forces it starts to take on a permanent bend in the direction of the force. He showed me reinforcements to a wooden hull that attempt to try and counter the pull of the standing rigging. It helps but it doesn't stop it and this was just in a 24 foot boat.

Even wooden power boats have problems with torque and flexing and taking on a new shape but I don't remember any specifics of their issues.

Oceanride007 03-05-2016 16:22

Re: Why did wooden ships never get much beyond 300 feet...
 
As then as now, the worse case a vessel can find itself in, is when the pitch of the wave is the same as the length of the vessel. When the wave is midship, it hogs, when the wave is at ships end, it sags.
Modern ships over a certain size but fairly recent, had to change to longitudinal construction (Longitudinal stringers), notch tough steels, designs that avoided stress raisers, high fatigue life. What is still difficult is achieving these requirements, while still avoiding corrosion and the wish to maximise return to the investor. Would think 25 years would be a good life.
If you could build a wooden vessel of sufficient beam strength, and restore strength across a join, and if you could convince a investor/dreamer, yes longer ships would have occurred.

HappyMdRSailor 04-05-2016 04:37

Re: Why did wooden ships never get much beyond 300 feet...
 
Quote:

Originally Posted by MarkJ (Post 2112059)
Because its too long to walk with a peg leg and parrot on your shoulder.


HAAAAAAAAAAAAAAAAAAAA!!!!! :thumb:

black_sails 04-05-2016 05:06

Re: Why did wooden ships never get much beyond 300 feet...
 
Quote:

Originally Posted by Stumble (Post 2112111)
As mentioned hogging, and it's corrilary sagging start to become insurmountable problems when the length of wooden ships excedes about 300'. Simply put the Youngs Modulus simply isn't high enough for the material to resist the flex generated.

It isn't just wave action that is an issue here, turning a 300' long ship exerts tremendous torque loads on the hull, and wood simply isn't stiff enough to resist them.


I can understand that far, but would it be the same if there were a steel frame and wood were only used as the outer hull material? I would have assumed it's a global vs local strength issue.

I guess part of my curiosity is that I assume if a steel frame wooden 'envelope' hull would have worked, why wasn't that seen...

Jim Cate 04-05-2016 14:32

Re: Why did wooden ships never get much beyond 300 feet...
 
Quote:

I guess part of my curiosity is that I assume if a steel frame wooden 'envelope' hull would have worked, why wasn't that seen...
Quite possibly because the cost would have been higher than simply plating in steel! The additional strength afforded by said plating would likely mean that t he framing would be less expensive to build... a win-win situation.

Jim

El Pinguino 04-05-2016 14:37

Re: Why did wooden ships never get much beyond 300 feet...
 
They did build quite a few composite ships with steel or iron frames and timber planking and a few survive to this day. Cutty Sark was one.
Benefits were that they could copper clad a timber hull but not a steel one and fouling was a major issue on early steel ships... as was electrolysis .

reed1v 05-05-2016 05:08

Re: Why did wooden ships never get much beyond 300 feet...
 
Quote:

Originally Posted by El Pinguino (Post 2113019)
They did build quite a few composite ships with steel or iron frames and timber planking and a few survive to this day. Cutty Sark was one.
Benefits were that they could copper clad a timber hull but not a steel one and fouling was a major issue on early steel ships... as was electrolysis .

Quite true plus related to electrolysis was the electrical field set up by a steel ship. Created havoc with compasses until degaussing tools became available. The field created by moving thousands of tons of steel through salt water is quite significant.

Cherp 05-05-2016 06:35

Re: Why did wooden ships never get much beyond 300 feet...
 
Quote:

Originally Posted by Shrew (Post 2112095)
Traditionally the distance from the tip of the middle finger to the elbow.

1 cubit = 1.47637795276 ft
0.4572 meter

Dimensions of the vessel: 300 cubits in length,
50 cubits in width
30 cubits in height

No, a cubit in the ancient world was (as the name implies) a cube, measuring four fig-fruit lengths a side. That's a very small boat, but you must recognise that Noah and the animals were not evolved to their current size. Noah himself would have been only two feet tall, in today's measure and a few cubits in girth - small but stocky. The flood itself was probably only a couple of hundred gallons. As Albert Einstein said, it's all relative.

Saleen411 05-05-2016 07:28

Re: Why did wooden ships never get much beyond 300 feet...
 
https://en.wikipedia.org/wiki/Nemi_ships

HUGE wooden ships.....more like barges...built over 2000 years ago.

The largest of the 2....240 feet long and 79 feet wide.


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