Ark Design Part 2: Demonstrated

All Images and text © Tim Lovett Sept 06 | Home | Menu

Why the 'new' look?

While there could be other solutions to the design of Noah's Ark that would still comply with the biblical specifications. Here, we attempt to combine modern knowledge of how a ship behaves in the water with some of the surprising technology of ancient shipwrights. 

 Demonstrated.  Is the rigid sail really necessary? And why the underwater projection? ... It almost looks like the bulbous bow of a modern tanker, or is it related to the ramming bow of a Greek trireme? 

These features work together to control the Ark, using the wind (Gen 8:1) to maintain direction and avoid broaching.    > See video demonstrations here  

 


That Sail... 

The rigid, fin-like structure at the bow of the Ark helps to keep the vessel pointing downwind. This works in conjunction with a submerged projection at the stern, causing the vessel to align itself perpendicular to wind driven waves. This gives the most comfortable ride possible, and lowers the risk of capsize in extreme seas. It also makes some sense of the otherwise mysteriously long proportions of this particular 'lifeboat"1. Noah's Ark is six times as long as it is wide, yet most lifeboats are more stout than this. So if it wasn't meant to travel fast, why was Noah's "lifeboat" so slender?

Enough words. Let's see the "sail-fin" in action.

Big Turn-Around

The 2m (6ft) fibreglass model is weighted to give a draft of around 40% of the hull depth. The model was pushed into a light headwind (approx 8 knots).

With initial momentum it stays on course for a while, until it slows and the waves begin to knock it off course. The sailfin now catches wind and begins to turn the vessel. The waves try to hold the hull at 90 degrees (beam sea, waves approaching from the side). This is the worst situation for a ship - uncomfortable in small waves and dangerous in a heavy sea.

The wind continues to drive the bow around to a following sea. This brings the vessel under control without any effort from the crew.

Launch in external player  

 

 

 

 

 

 

 

 

 

 


Noah's Ark just had to float, right?

If it "just had to float" it would have saved Noah a lot of time and effort to build a "just had to float" kind of boat. A long hull is more difficult, so it needs a good reason, like speed for instance. This is what the clipper sailing ships of the 1800's were designed for. Noah's Ark had a similar length to breadth ratio, yet it didn't have to race anywhere. 

It would have been tempting to shorten the vessel and save some work. Here's why; 

1. It Must Be Strong

As waves pass under the Ark, the middle experiences bending forces alternately upward (hogging) and downward (sagging). A ship hull has to act like a bridge, only worse - a bridge one minute and a see-saw the next.

The longer the hull, the greater the bending effect. Now Noah has to put add wood to make the middle strong enough. If it  were half as long the wave bending effect be approximately halved. See Wave Bending Moment2.

2. Surface Area to Volume Ratio

A cube has the highest volume with the least surface area (for rectangular prisms). As the hull grows longer and narrower, more wood is needed to achieve the same total volume. 

The amount of wood increases with the slenderness of the hull, and logically, Noah's workload increases in proportion.

Using proportions closer to a lifeboat would save another 20% or so. 

 

3. Stability

A shorter, wider vessel is more stable. This was a clear conclusion of the Korean study. The most stable "Ark" had a length-to-breadth ratio similar to lifeboat. 

Hull 10 topped the comparison. Note that the Korean study assumed a random sea rather than a regular sea which a large scale wind would produce. (Gen 8:1)

 

 

 

 


Broaching the Subject...

Broaching4 is when waves turn a ship side-on. This can even result in capsize in heavy seas. Any long object floating in the water will be turned sideways (wave induced yaw). Basic physical laws drive a buoyant object towards its lowest energy state, and roll motion has the least inertia. Without power or navigational control, a ship is simply "caught in the trough of the waves". The proportions of Noah's Ark are no exception. In fact, it's long length is a disadvantage in a regular sea (Gen 8:1) where a steady wind generates near parallel wave fronts. 

Watch what happens seconds after a 6ft (2m) model of biblical proportions (300x50x30) is left drifting in wind-generated waves.  

No Escape

Driven by the dynamics of wave motion, a simple box with the proportions of Noah's Ark drifts in a beam sea. 

The model turned immediately and never recovered. Avoiding a beam sea becomes a top priority in heavy weather. For a drifting ship (without propulsion) there is no escape unless something can overpower the turning force (yaw) of the waves.

Launch in external player  

 

 


How Big Does the Sail-fin Need to Be?

The sail-fin must be big enough to overcome the turning effect (yaw) of the waves. This means it can't be trivial.  

However, the upturned stems of ancient ships and the huge areas of sail on the "windjammers" mean that a sailfin of a large size is viable. Since no adjustments are needed, a rigid wooden structure can be used, rather than troublesome canvas. It must also be big enough to ensure correct operation even if the wind begins to die down. If it is unable to overcome wave yaw at the most dangerous time, it has failed.

One side effect of the sailfin is that it helps to dampen roll and increase roll inertia. A century ago as steam power was replacing sail, roll was suddenly a big problem. The huge masts had been suppressing roll motion.   

Smaller Sailfin

The optimum size of the sailfin is dependent on many factors. Wind speed, the amount of fetch available to develop waves, the presence of other waves generated by previous or distant wind.  

Another factor when using a scale model is that the relative strength of wind and water do not scale linearly. Wind is also very height dependent, so a full-scale vessel interacts with higher wind velocities. The size and shape of the waves is another factor.  

Launch in external player  

 

 


Is the Projecting Stern Really Needed?

While the sail-fin pulls the bow around to point with the wind, the submerged stern projection does exactly the opposite - prevents the stern being pushed to the front. 

Does it really work?  This feature is a like a skeg or a fixed rudder. Even on unpowered barges design to be towed, a skeg helps to give directional stability in the open sea. Most ships have a skeg-like structure of some description. The reason? So the stern can't go sideways. 

A submerged projection may look familiar - like the ramming bow of a Greek Trireme. However, depictions of ships from thousands of years earlier show a similar feature. Historians call it a mystery.3 It makes more sense that the first ship in post-flood history (Noah's Ark) set the precedent, and this became the standard way to do things - even when a ship is too small to really need it. 

Canceling Each Other Out

To test the effect of the skeg, the sail-fin was moved from bow to stern. Now both are fighting against each other - the sail-fin tries to push the stern around while the skeg is trying to stop it.  

The result? They cancelled each other out and the model remained in its natural position - almost exactly in a beam sea.  

Launch in external player  

Rigid Sails

Kindled by the fuel crisis in the 1980's, commercial use of sail power was investigated - particularly by Japan. As the crisis waned, so did interest in the maintenance intensive mechanized sails. They worked of course, but cargo is always worth too much to let the wrong weather slow things down. 

Yasuo Yoshimura commented 5; "Aft-sail is sometimes convenient and safe for the operation of a small fishing boat, as it automatically turns the shipís heading to the weather side."  This is less efficient since the rudder and skeg work against the wind pushing the stern leeward. (As shown above)



References

1. A shorter hull is stronger, and being wider and taller, would also be more stable. Strength and stability both push for a shorter length. See Why Such a Long Hull?   Return to text

2. ABS Rules. American Bureau of Shipping.  See Wave Bending MomentReturn to text

3. Could ancient ships give any clues about Noah's Ark? Since the Ark is the first ship in our history, it is like a prototype for Noah's descendents. If certain features emerge in the depictions of ancient ships they might be derived from Noah's Ark. See Flood LegendsReturn to text

4. See Wave Yaw and BroachingReturn to text

5. "Aft-sail is sometimes convenient and safe for the operation of a small fishing boat, as it automatically turns the shipís heading to the weather side." A summarizing remark (1 of 4) by Yoshimura, Yasuo., A Prospect of Sail-Assisted Fishing Boats, Proceedings of International Commemorative Symposium - 70th Anniversary of the Japanese Society of Fisheries Science, October 1-5, 2001, Yokohama.  http://eprints.lib.hokudai.ac.jp/dspace/bitstream/2115/621/1/JFSF2000.PDF  Return to text


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