The Boat of No Specific Bow or Stern

Ata Atun

 

The boat of no specIfIc bow or stern

 

Ata ATUN*

Near East University & SAMTAY Foundation

Nicosia, North Cyprus

 

Abstract

 

The design concept of one of the sailing boats of our voyaging ancestors has no fixed bow or stern [1]. This concept of at least three thousand and five hundred years old, may open up a new era in the form of sailing boats and fishing boats, propelled by wind. 

 

There are no forward and aft perpendiculars and the keel itself turns in to perpendiculars at both ends.

 

The curvature of the keel is absolutely symmetric at amidship [1] and both sections are in duplicate hyperbolic shape, touching each other on the tip of x-axis.  The keel is constructed as a bar keel type.

 

Transversely the cross section is symmetric at centerline and both halves are in identical semi elliptic shape, crown downwards.

 

The mast is placed right in to the geometric center of the boat, longitudinally and transversely. The sail is in rectangular form.

 

There is no fixed rudder and an oar shaped flat plank with a widening tip [2] is used as a rudder. Strong loop shape knots made of thick rope are placed on the starboard side of each end and the rudder is slipped in according to the direction of sailing and wind.

 

The speed of this unique boat, I believe, topped 9 knots from time to time with no option of capsizing.   

 

Block coefficient, Waterplane area coefficient, Midship section coefficient, Longitudinal prismatic coefficient and Vertical prismatic coefficient of this boat reveals very interesting and interrelated ratios. [3]

 

The depth, draft and freeboard ratios are worth to study to find out the physical features leading to high speed and almost non capsizing stability, which is almost impossible to be achieved in our modern time. 

 

 

 

 

1.      Introduction

 

Three thousand five hundred years old boat of an amazing ancient design. The design concept reminds the early cars with no reverse gear. Sailing ahead with this boat needs no maneuvering at all times.

 

The peculiarity of this boat is its double-ended shape. That is to say, there was little or no difference in the shape of their bow and stern [4]. As long as ships were steered by oars or by oar-shaped rudders hung over one side near the stern there was no reason to alter this double-ended design.

 

2.      Design

 




























The boat is symmetric longitudinally and transversely.

 

 

Sides Plan, Top view and Midship Transverse section plans

 

















Main mast is located right in the center of the symmetry in both directions.

The keel is not straight even partially and is in the shape of two semi hyperbolas touching each other from the lowest allowable -x- coordinate at the bottom of the vertical axis of symmetry [5].

 

The keel on the tip of the bow raises 1.00 m. above the upper floor level vertically.

 

 

 

                                                                                                                         

 

Longitudinal Cross section


Longitudinal Metacenter is 13.97 m. above the center of the keel. [6]

 

The design and stiffness values are below.

 

KL    =    1.15 m.




















 

KB   =    0.77 m.

 

KG   =    1.85 m.

 

KML =  13.97 m.

 

 

 

 

 

The boat is propelled by wind naturally and the rudder is not in a fixed place.

 

The rudder is in the shape of an ore but rather more wider and thicker in size. Usually its place is to the post side of the stern part at that specific sailing position. [7]

Design values

 























A thick rope knot is fitted to the port sides of each end for the purpose of sliding in the rudder, according to the direction of wind and sailing.

 

The rudder has no effect at all on heeling or tilting.

 

Thickness of the sides plank is around 2.5 cm. .The type of wood used were oak, acacia, hop hornbeam, juniper and soapberry for smaller parts and  the majority of the pieces including side planks were of cedar from Lebanon [8] .

 

The size ( width x thickness) of the :

Deck planks          : 20 x 3 cm.

Bottom planks       : 15 x 3 cm.

Freeboard planks   : 20 x 2.5 cm.

Bulwark planks     : 15 x 4 cm.

 

Post size : 5.5 x 7.5 cm.

Post spacing : 25 cm.s center to center

 

 

Ribs are of 3 pieces and their average lengths of each rib is 70 cm.s.  

 

The oar position and detail

Although the average speed of the boat looks like around 6 knots per hour and the maximum speed 9 knots per hour, according to the coefficient of form, it should be around 15-25 knots, if not capsized.

 

The sail area is 12.375 m2. and is made of  a single piece of canvas sized  2.75 m. (height) by 4.50 m. (width), in rectangular shape.  The sail had a boom which was allowed to rotate [8].  It is reasonable estimate that the ancient sailors never sailed with the wind more than 30 degrees from dead astern. [9]

 

 

3.      Coefficients of Form [10]

 

a)      Block Coefficient (CB)

 

Displacement  Volume, Ñ    :    9.32 m3

 

Depth to the Breadth, T       :    1.15 m.

Water Line Length,    LWL   :    7.14 m.

Water Line Breadth,  BWL    :    2.14 m.

 

CB = Ñ / (LWL x BWL x T) = 9.32 / (7.14 x 2.14 x 1.15) =  9.32 / 17.57

CB  = 0.53

 

 










 

b)      Waterplane Area Coefficient (CA)

 

The water plane area, AWP : 10.37 m2

Water Line Length,    LWL :   7.14 m.

Water Line Breadth,  BWL :   2.14 m.

 

CA = AWP /(LWL x BWL)

      = 10.37 / (7.14 x 2.14)

      = 0.68

 

 

c)      Midship Section Coefficient (CM)











 

Area of immersed Midship, AM : 1.265 m2

 

Depth to the Breadth, T       :    1.15 m.

Water Line Breadth,  BWL    :    2.14 m.

 

CM = AM / (BWL x T)

     =  1.265 / (2.14 x 1.15)

     =  0.51

 

 

 

 

d)     Longitudinal Prismatic Coefficient (CP)

 

Displacement  Volume, Ñ          :    9.32   m3

Area of immersed Midship, AM :    1.265 m2

Water Line Length,    LWL            :    7.14   m

 

CP =  Ñ / (AM x LWL)

     = 9.32 / (1.265 x 7.14)

      = 1.04  

 

 

e)      Vertical Prismatic Coefficient (CVP)

 

Displacement  Volume, Ñ    :    9.32 m3

The water plane area, AWP    :  10.37 m2

Depth to the Breadth, T       :    1.15 m.

 

CVP =  Ñ / (AWP x T)

       = 9.32 / (10.37 x 1.15)

       = 0.78

 

 

 

 

4.      Conclusion

 

This ancient boat is very seaworthy and speedy.  Although the boat is not stiff and the tilting or heeling is non stop, I believe the capsize possibility is very low. [11] 

 

After checking the coefficients of forms, the speed turns about to be around 15-25 knots. [12]

 

The results of the Block coefficient and Water Plane area coefficient  satisfies the empirical formula CA = CB + 0.10 [13].

 

Every rope connected with the rudder rigging was to have its purpose, the strains nicely calculated and so arranged that practically all tension was taken from the rudder post when the boat was under way. [14]

 

Since the Egyptian warships had a stout metal ram at their bows [15], this proves the use of nails made of metal, probably soft iron, in the construction. 

 

References

 

[1]  Phillips-Birt, D., A History of Seamanship, Jarrold & Sons Ltd., Norwich, UK, 1971,      pp. 59

 

[2]  Mondfeld, W. zu., Historic ship Models, sterling Publishing Co. Inc. NY, 1985

      pp. 128

 

[3] Ata Atun, Unsalan, D., Ship Construction for Merchant Marine Officers, Near East University Press, North Cyprus, 2000.  pp. 2-7, 8, 9, 10, 11.

 

[4]  Anderson, R and R.C., The sailing Ship, Biddles Ltd. Guildford, Surrey, UK, 1980. pp. 30

 

[5]  Morrison, J., The Ship 3000 BC-500 AD, HMSO, Ipswich, UK. Pp. 12         

 

[6]  Ata Atun, Unsalan, D., Basic Ship Stability, Near East University Press, North Cyprus, 2000. pp. 8-2

 

[7]  Güleryüz, V. H., Uygulamali Gemi Modelciligi, Kaptan Yayincilik, Istanbul, 2003.        pp. 169

 

[8]  Johnstone, P., The Archaeology of Ships, Henry Z. Walck, Inc., NY, 1974. pp.10

 

[9]  Phillips-Birt, D., A History of Seamanship, Jarrold & Sons Ltd., Norwich, UK, 1971,      pp. 36

 

[10]   Ata Atun, Unsalan, D., Ship Construction for Merchant Marine Officers, Near East University Press, North Cyprus, 2000.  pp. 2-6.

 

[11]   Agip SPA., A Tribute to the sea. Colora, Lodi, Milano, Italy. pp 25

 

[12]   Ata Atun, Unsalan, D., Ship Construction for Merchant Marine Officers, Near East University Press, North Cyprus, 2000.  pp. 2-7.

 

[13]   Ata Atun, Unsalan, D., Ship Construction for Merchant Marine Officers, Near East   University Press, North Cyprus, 2000.  pp. 2-8.

 

[14]   Culver B., Henry, The Book of old ships, Dover Publications Inc, New York,  pp. 9.

 

[15]   Cornwell, E. L., An Illustrated History of Ships, Fratelli spada, Italy, 1979. pp.12