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What is difference between Heel and Roll in case of ships terminology?

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Question added by Najeefullah Abdul Azeez Jaffer Ali , Naval Architect / Structural/ Production Planning Engineer , Nakilat Keppel Offshore and Marine Ltd (NKOM)
Date Posted: 2015/07/11
Kambiz Mohtashami
by Kambiz Mohtashami , Naval Architect , BATSERVICE Iran

Roll is ship's motion around its longitudinal axis  and it happens for  every ship at sea when it's not drived by its propulsion and a ship has other motions as well , like  its motion around transvese axis and so . But heel is when a ship is not upright and tilted around its longitudinal axis by an angle which should be avoided and most of the time happens when mass distribution of ships hull or equipments is not symetrical .

Florencio Edaño
by Florencio Edaño , Sales Staff , SM Supermall

Heel describes a temporary inclination generally involving motion, such as wind or turning while roll indicates periodic inclination from side to side such as wave action.

Heel is a deviation around the longitudinal axis (static). Roll is a movement, tilt, around the longitudinal axis (as it's a movement, roll isn't static).

Osman Ornegyazalim
by Osman Ornegyazalim , Production Engineer , Hanse Yachts Group

Heel angle represents constant floating angle of vessel, which must be zero. At different heel angles you have different heeling moments. For Ex. If you have STB5 degrees of heel it means ship was loaded more heavily on STB and at this angle you have zero heeling moment to zero the ships heeling angle.

Rolling is motion of ship regarding the dynamic conditions. Rolling angle is zeroed by heeling moment in even heel loaded conditions. 

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