The Boat Of No Specific Bow Or Stern
Ata Atun
17th
Annual Symposium on Maritime Archeology and
History of
Hawai’i and the Pacific
February 1819, Big
The
boat of no specIfIc bow or stern
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
xaxis. 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 doubleended 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 oarshaped rudders hung over
one side near the stern there was no reason to alter this doubleended 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
Longitudinal Cross section 
Longitudinal Metacenter is
The design and stiffness values are below.
KL =

KB =
KG =
KM_{L} =
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
The size ( width x
thickness) of the :
Deck planks
: 20 x
Bottom planks
: 15 x
Freeboard planks
: 20 x
Bulwark planks
: 15 x
Post size : 5.5
x
Post spacing :
Ribs are of 3 pieces and their average lengths of each rib
is
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 1525 knots, if not capsized.
The sail area is
3.
Coefficients of Form
[10]
a)
Block Coefficient
(C_{B})
Displacement
Volume,
Ñ
:
Depth to the Breadth, T
:
Water Line Length,
L_{WL} :
Water Line Breadth,
B_{WL} :
C_{B} =
Ñ /
(L_{WL}
x B_{WL}
x T) =
C_{B}
=

b)
Waterplane Area Coefficient
(C_{A})
The water plane area, A_{WP }:
Water Line Length,
L_{WL }:
Water Line Breadth,
B_{WL} :
C_{A} = A_{WP} /(L_{WL}
x B_{WL})
=
= 0.68
c)
Midship Section Coefficient
(C_{M})

Area of immersed Midship, A_{M}
:
Depth to the Breadth, T
:
Water Line Breadth,
B_{WL} :
C_{M }= A_{M}
/ (B_{WL} x T)
= 1.265 / (2.14 x 1.15)
=
d)
Longitudinal Prismatic Coefficient
(C_{P})
Displacement
Volume,
Ñ
:
Area of immersed Midship, A_{M
}:
Water Line Length,
L_{WL
}:
C_{P }= Ñ
/ (A_{M }
x L_{WL})
=
=
e)
Vertical Prismatic Coefficient
(C_{VP})
Displacement
Volume,
Ñ
:
The water plane area, A_{WP
}:
Depth to the Breadth, T
:
C_{VP} =
Ñ / (A_{WP}
x T)
=
= 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 1525 knots. [12]
The results of the Block coefficient and Water Plane
area coefficient satisfies the empirical
formula C_{A} = C_{B} +
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]
PhillipsBirt, D., A History of Seamanship, Jarrold & Sons Ltd., Norwich,
UK, 1971, pp. 59
[2]
Mondfeld, W. zu., Historic ship Models, sterling Publishing
pp. 128
[3] Atun, A., Unsalan, D., Ship
Construction for Merchant Marine Officers,
[4]
[5]
[6]
Atun, A., Unsalan, D., Basic Ship Stability,
[7]
Güleryüz, V. H.,
[8]
Johnstone, P., The Archaeology of Ships, Henry Z. Walck, Inc., NY, 1974.
pp.10
[9]
PhillipsBirt, D., A History of Seamanship, Jarrold & Sons Ltd., Norwich,
UK, 1971,
pp. 36
[10] Atun, A., Unsalan, D., Ship Construction for Merchant
Marine Officers,
[11]
[12] Atun, A., Unsalan, D., Ship Construction for Merchant Marine
Officers,
[13] Atun, A., Unsalan, D., Ship Construction for Merchant Marine
Officers, Near East University Press,
[14] Culver B.,
[15] Cornwell,