Section 1 Towing arrangements and resistances

101. Towing arrangements

Towing arrangements in tugboats and barges are divided into towing equipment and ments and specified generally as follows:

towing arrange-

102. Tow-lines

1. The length of tow-lines is determined by the following formula. However, when its service restricted within smooth water, it is to be at the discretion of the Society.

area is

Å G ÄFÄË ĞÄË F

Å : length of tow-line (m )

ÄË : length of tugboats or half length of barge (m )

ÄË : length of barge (m )

Ä : the value obtained from following table

2. The strength of towing arrangements is to be in accordance with followings.

(1) Minimum breaking strength of tow-lines is to be in accordance with the following table.

(2) in case of chain, shackle, deltaplate and ring, etc. for linking tow-line

Å G ËĦÈ× B

where,

Å : minimum breaking strength of chain, shackle, deltaplate, ring, etc. (ton)

B : minimum breaking strength of tow-lines as specified in (1) (ton)

(3) in case of towing hook

Å G ËĦÈ× B

where,

Å : minimum breaking strength of towing hook (ton)

B : minimum breaking strength of tow-line as specified in (1) (ton)

(4) in case of brackets, bollards, bits and fair leaders

Å G ËĦĖ× B

where,

Å : ultimate strength of brackets, bollards, bits and fair leaders (ton)

B : minimum breaking strength of tow-line as specified in (1) (ton)

103. Total resistance of towed ships

1. Total resistance of towed ships is to be in accordance with followings and requirements for determining the bollard pull of the tugboats.

the values may be the

ĄŹ G ĄX ĞĄŽ Ğ ĄŴ (ton)

ĄŹ : Total resistance of towed ships (ton)

ĄX : frictional resistance as obtained from the following formula

X Ë Ë

Ą G ŊĦŊŊŊËĖÈÁ A ÃË (ton)

Where,

Ë

ÁË : hull surface condition coefficient, 0.8 A : surface area below the waterline (m Ë) Ã : towing velocity (knots)

ĄŽ : wave making resistance as obtained from the following formula

Ž Ë Ë

Ą GŊĦŊËĖÆÁ A ÃË (ton)

where,

Æ :

AË :

à :

ÁË :

resistance coefficient of rough sea condition, 1.2 hull cross sectional area below the waterline (m Ë)

towing velocity (knots)

bow shape coefficient as obtained from the following table

ĄŴ : air resistance as obtained from the following formula

Ą ŊĦŊŊŊŊËŊÈÆ Æ A FÃ ĞÃËF (ton)

Ŵ G Z Ă Ė Ž

where,

Ė

A : total cross sectional area exposed to wind above the waterline (m Ë)

à : towing velocity (knots)

ÆZ : shape coefficient of hull surface facing the wind as obtained from the following table

ÆĂ : coefficient of height following table

from waterline to center of area facing the wind as obtained from the

ÃŽ : wind velocity due to service area as obtained from the following table.

2. In addition to the requirements of 1, added resistance due to significant wave height in the follow- ing table is to be considered.