2.6.1.2 Synthetic Line Systems
Due to the lower recommended allowable loads in synthetic lines (refer to Section 4), it is recom-
mended thar the vaJues of ' S )( MBL' and 'BR )( MBL' obLained by formulae (22) and (23) be
increased by 20070 for nylon and by 100 /0 for other conventjonal synthetic mooring lines. Tn case of
newer, low stretch. synthetic materiaJs. such a Aramid, specific recommendations have not been
made at this t.i.me due to the limited experience.
2.6.2 Rough Spring Line Restraint Determination for Oil Tankers above 16 kD WT when the Ship's
Transverse Wind Area is Unknown
Where a ship's length. beam and depth are koown, a very approximate determination of spring line
requirements for tankers with wire mooring lines can be made using the fol.lowing formula:
S x MBL = 1.992DB - 0.0398 Lop + 19.9B + 40 + 0.369 (0.OlL5p + Lop) (24)
Tbe formula is derived from formula (22) by substituting the following for A'i1I
A'i1I = BD - 0.02 L8P + lOB + 20
The super.'ilrucrure and house transverse area is roughly approximated by "lOB + 20",
2.6.3 Rough Breast Line Restrainl Determination for Oil Tankers above 16 kDWT when the Ship's
Latera! Wind Area is Unknown
Where a sbip's length, summer draft a nd depth are known, a very approximate det.ermination of
breaSt line rc:quirements for tankers with wire mooring hnes can be made using the following formula:
BR x MBL = Lop[1.550 (D - T) + 1.291 T + 2.0664J + 517 (25)
This fonnula is derived from formula (23) by substituting lhe following for A LF:
A LF = 1.05 Lnp (D - T) + 1.4 Lop + 350
where 'D -T' is the freeboard midships in the full load condition.The term "J.4 Lep + 350 ml", constitutes a rough statistical approximation of the superstructure
and house lateral area. Even though this value can vary considerably from tanker to tanker, the
inaccuracy arising from variance in superstructure and house area is generally small. This is due to
the relatively far greater importance assigned lO the hull area.
A formula of this lype may be used by a terminal operator to assess the suitabi]jly of individual
ship moorings at his berth rather than relying on a general set of requirements based sol ely on
dead weight or displacement.
2.6.4 A,laoring Restraint Requirements for Gas CarriersThe required mooring restraint for gas carriers may be approximated by the method described in
Section 2.6.1. The same assumptions as listed in Section 2.6.1.1 apply, except Ihal ma..ximum forces
ro be restrained are based on formulae (16) and (19) for the longitudinal direction and formulae
(18) and (21) for the transverse direction.The following approximate mooring line requirements for gas carriers apply to wire rope systems.
For synthetic li.nc systems refer 10 Section 2.6.1.2.