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Review and Update of U.S. Coast Guard Vessel Stability Regulations and Guidance (2019)

Chapter: Appendix D: Results of Lightship Weight Sensitivity Analysis for Selected Small Passenger Vessels

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Suggested Citation:"Appendix D: Results of Lightship Weight Sensitivity Analysis for Selected Small Passenger Vessels." National Academies of Sciences, Engineering, and Medicine. 2019. Review and Update of U.S. Coast Guard Vessel Stability Regulations and Guidance. Washington, DC: The National Academies Press. doi: 10.17226/25565.
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Suggested Citation:"Appendix D: Results of Lightship Weight Sensitivity Analysis for Selected Small Passenger Vessels." National Academies of Sciences, Engineering, and Medicine. 2019. Review and Update of U.S. Coast Guard Vessel Stability Regulations and Guidance. Washington, DC: The National Academies Press. doi: 10.17226/25565.
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Page 101
Page 102
Suggested Citation:"Appendix D: Results of Lightship Weight Sensitivity Analysis for Selected Small Passenger Vessels." National Academies of Sciences, Engineering, and Medicine. 2019. Review and Update of U.S. Coast Guard Vessel Stability Regulations and Guidance. Washington, DC: The National Academies Press. doi: 10.17226/25565.
×
Page 102
Page 103
Suggested Citation:"Appendix D: Results of Lightship Weight Sensitivity Analysis for Selected Small Passenger Vessels." National Academies of Sciences, Engineering, and Medicine. 2019. Review and Update of U.S. Coast Guard Vessel Stability Regulations and Guidance. Washington, DC: The National Academies Press. doi: 10.17226/25565.
×
Page 103
Page 104
Suggested Citation:"Appendix D: Results of Lightship Weight Sensitivity Analysis for Selected Small Passenger Vessels." National Academies of Sciences, Engineering, and Medicine. 2019. Review and Update of U.S. Coast Guard Vessel Stability Regulations and Guidance. Washington, DC: The National Academies Press. doi: 10.17226/25565.
×
Page 104
Page 105
Suggested Citation:"Appendix D: Results of Lightship Weight Sensitivity Analysis for Selected Small Passenger Vessels." National Academies of Sciences, Engineering, and Medicine. 2019. Review and Update of U.S. Coast Guard Vessel Stability Regulations and Guidance. Washington, DC: The National Academies Press. doi: 10.17226/25565.
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Page 105

Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

PREPUBLICATION COPY—Uncorrected Proofs 100 Appendix D Results of Lightship Weight Sensitivity Analysis for Selected Small Passenger Vessels 65 ft/179-Passengers Tour Boat FIGURE D-1 Subject vessel for hypothetical sensitivity study: 65 ft/179-passengers Subchapter T Small Passenger Vessel. TABLE D-1a 65 ft/179-Passengers Tour Boat–Vessel Particulars Vessel type: Aluminum, flush deck, single-chine hull, main deck cabin; open upper deck LBP (ft) 64.90 Beam (ft) 20.20 Depth (ft) 8.10 Draft (ft) 4.58 Lightship (LT) 26.85 VCG in Lightship condition (ft ABL) 8.62 Least GM condition Full load departure Displacement in that condition (LT) 47.41 VCG (ft ABL) corrected for F.S. 9.97 GM (ft) corrected for F.S. 7.59 NOTE: ft = feet; ft-ABL = feet above baseline; GM = metacentric height; KM = height of metacenter above the keel; LBP = length between perpendiculars; LT = long ton(s); pct = percentage; VCG = vertical center of gravity.

PREPUBLICATION COPY—Uncorrected Proofs 101 TABLE D-1b Summary Results of the Impact of Lightship Weight Growth on Intact and Damaged Stability on 65 ft/179-Passengers Subchapter T Small Passenger Vessel LOAD CONDITION Cond II Depart Cond II Depart Cond II Depart Cond III Return Cond III Return Cond III Return Intact Requirement As certified +2% of LS +3% of LS As certified +2% of LS +3% of LS 46 CFR § 171.050–Passenger Heel GM > 3.50 – 4.00 FT 7.59 7.46 7.42 7.93 7.81 7.70 46 CFR § 170.170 (a)–Weather criterion GM > 4.20 – 4.80 FT 7.59 7.46 7.42 7.93 7.81 7.70 46 CFR § 170.173(e) Criterion for vessels of unusual proportion and form. (e) For the purpose of demonstrating…or the following criteria is required: (1) For partially protected routes, there must be - (i) Positive righting arms to at least 35 degrees of heel; 37.50 37.50 >35 36.50 >35 >36 (ii) No down flooding point to at least 20 degrees; and 30.00 30.00 30.00 30.00 30.00 30.00 (iii) At least 15 foot-degrees of energy to the smallest of the following angles: (A) Angle of maximum righting arm. (GOVERNS) 15.27 15.00 14.91 15.08 14.85 14.75 (B) Angle of down flooding. (C) 40 degrees. Damaged - 46 CFR § 171.080(f) requires vessels built after April 15, 1996, to meet the following criteria with any one compartment flooded: (1) Positive righting arms for a minimum range beyond equilibrium of 10 degrees (Partially-protected waters/Great Lakes in summer) 22.73 23.01 (2) No downflooding point within the range in (1) above. (3) Area under righting arm curve of at least 0.015 meter-radians (2.82 ft-degrees) to the least of: (i) The angle of downflooding 7.33 7.80 (ii) The angle of vanishing stability (4) GZ (righting arm) = C × {[Heeling moment/Dips] + 0.131} ft (but not less than 0.328 ft) 0.51 0.53 (5) Not applicable to this vessel (6) Angle of equilibrium not to exceed- (i) 7 degrees for flooding of one compartment; 0.00 0.00 (ii) 12 degrees for flooding of two compartments; or (remaining not applicable to this vessel) (7) The margin line must not be submerged when the vessel is in equilibrium 0.47 0.47 (8) and (9) Not applicable to this vessel Where GZwind = 0.75 × {[2.506 × 730 × 8.65]/(45 × 2240)] + 0.131} = 0.216 Where GZpass = 0.75 × {[0.5 × 183 × 185 × 3.0]/(45 × 2240)] + 0.131} = 0.476 GOVERNS NOTE: GZ = Righting Arm.

PREPUBLICATION COPY—Uncorrected Proofs 102 90 ft/340-Passengers Excursion Vessel FIGURE D-2 Subject vessel for hypothetical sensitivity study: 90 ft/340-passengers Subchapter K excursion/dinner boat vessel. TABLE D-2a 90 ft/340-Passengers Excursion Vessel – Vessel Particulars Vessel type: Excursion. Steel, flush deck, single-chine hull, main deck cabin; open upper deck LBP (ft) 84.00 Beam (ft) 30.00 Depth (ft) 7.08 Draft (ft) 5.23 Lightship (LT) 116.66 VCG in Lightship condition (ft ABL) 9.57 Least GM condition Full load departure Displacement in that condition (LT) 153.41 VCG (ft ABL) corrected for F.S. 10.50 GM (ft) corrected for F.S. 11.43 NOTE: ft = feet; ft ABL = feet above baseline; GM = metacentric height; KM = height of metacenter above the keel; LBP = length between perpendiculars; LT = long ton(s); pct = percentage; VCG = vertical center of gravity.

PREPUBLICATION COPY—Uncorrected Proofs 103 TABLE D-2b Summary Results of the Impact of Lightship Weight Growth on Intact and Damaged Stability on 90 ft/340-Passengers Subchapter K excursion/dinner boat vessel LOAD CONDITION FL Depart FL Depart FL Depart FL Depart 90% Burned out 90% Burned out 90% Burned out Intact Requirement As certified +2% of LS +3% of LS +6% of LS As certified +3% of LS +6% of LS 46 CFR § 171.050 - Passenger Heel GM > 5.35 – 5.75 Ft 11.43 11.40 11.27 11.13 11.42 11.26 11.12 46 CFR § 170.170 (a) - Weather criterion GM > 5.50 – 5.70 Ft 11.43 11.40 11.27 11.13 11.42 11.26 11.12 46 CFR § 170.173(e) Criterion for vessels of unusual proportion and form. (e) For the purpose of demonstrating…or the following criteria is required: (1) For partially protected routes, there must be - (i) Positive righting arms to at least 35 degrees of heel; 37.40 37.00 36.75 36.08 37.00 36.50 36.00 (ii) No down flooding point to at least 20 degrees; and 35.72 32.55 33.68 30.57 35.50 34.00 32.50 (iii) At least 15 foot-degrees of energy to the smallest of the following angles: (A) Angle of maximum righting arm. (GOVERNS) 17.36 16.70 16.47 15.68 17.46 16.56 15.90 (B) Angle of down flooding. (C) 40 degrees. Damaged 46 CFR § 171.080(f) requires vessels built after April 15, 1996, to meet the following criteria with any one compartment flooded: (1) Positive righting arms for a minimum range beyond equilibrium of 10 degrees (Partially protected waters/Great Lakes summer) 10.05 9.46 9.11 11.30 (2) No downflooding point within the range in (1) above. (3) Area under righting arm curve of at least 0.015 m-radians (2.82 ft-degrees) to the least of: (i) The angle of downflooding 8.88 7.99 7.45 11.30 (ii) The angle of vanishing stability (4) GZ (righting arm) = C × {[Heeling moment/Disp] + 0.131} ft (not less than 0.328 ft) 1.42 1.38 1.34 10.77 (5) Not applicable to this vessel (6) Angle of equilibrium not to exceed- (i) 7 degrees for flooding of one compartment; 0.00 0.00 0.00 0.00 0.00 0.00 (ii) 12 degrees for flooding of two compartments; or (remaining not applicable to this vessel) (7) The margin line must not be submerged when the vessel is in equilibrium 0.41 0.00 0.30 0.51 (8) Not applicable to this vessel (9) Not applicable to this vessel NOTE: GZ = Righting Arm.

PREPUBLICATION COPY—Uncorrected Proofs 104 120-ft Vehicle Ferry Barge FIGURE D-3 Subject vessel for hypothetical sensitivity study: Passenger and vehicle ferry barge; Subchapter T; 149 passengers/24 autos/light trucks or 4 semitrailers. TABLE D-3a 120-ft Vehicle Ferry Barge – Vessel Particulars Vessel type: Passenger/vehicle ferry barge; Subchapter T; 149 passengers/24 autos/light trucks or 4 semitrailers LBP (ft) 120.00 Beam (ft) 35.00 Depth (ft) 4.75 Draft (ft) 3.00 Lightship (LT) 127.69 VCG in Lightship condition (ft ABL) 4.70 Least GM condition Maximum load: 3’-0” draft Displacement in that condition (LT) 302.00 VCG (ft ABL) corrected for F.S. 8.69 GM (ft) corrected for F.S. 31.66 TABLE D-3b Summary Results of the Impact of Lightship Weight Growth on Intact and Damaged Stability on Passenger/Vehicle Ferry Barge; Subchapter T; 149 Passengers/24 Autos/Light Trucks or 4 Semi-Trailers LOAD CONDITION MAXIMUM DECK LOAD – four 80,000 lb GVW trucks Intact Stability Criteria - As certified +3% of LS +5% of LS +10% of LS 46 CFR § 171.050 – Passenger Heel GM = [(W/Δ)(2/3)(b)]/(tan(T)) = 1.68 ft 32.98 32.55 32.31 31.73 46 CFR § 170.170 (a) – Weather criterion GM = [PAH]/Wtan(T) = 0.09 ft 32.98 32.55 32.31 31.73 PFM 1-89(2) FOR PROTECTED WATERS

PREPUBLICATION COPY—Uncorrected Proofs 105 (e) For the purpose of demonstrating acceptable stability…compliance with § 170.173 or the following criteria is required: (1) For Protected routes, there must be (i) Positive righting arms to at least 25 degrees of heel; over 40 over 40 over 40 over 40 (ii) No downflooding point to at least 15 degrees; and 15.04 15.00 14.68 14.41 (iii) At least 10 foot-degrees of energy to the smallest of the following angles: (A) Angle of maximum righting arm. (GOVERNS) 41.55 40.83 40.64 39.11 (B) Angle of down flooding. (C) 40 degrees. Damaged Stability Criteria - 46 CFR §1 71.080(f) requires vessels built after April 15, 1996, to meet the following criteria with any one compartment flooded: Note: For this analysis, only the values of the most critical compartment are given. (1) Positive righting arms for a minimum range beyond equilibrium of 5 degrees (Protected waters) 10.87 10.69 10.57 10.26 (2) No downflooding point within the range in (1) above. 10.87 10.69 10.57 10.26 (3) Area under righting arm curve of at least 0.015 meter-radians (2.82 ft-degrees) to the least of: (i) The angle of downflooding 24.76 23.54 22.74 20.8 (ii) The angle of vanishing stability (4) GZ = C × {[Heeling moment/Disp] + 0.131} ft (but not less than 0.328 ft) 3.596 3.5 3.39 3.184 (5) Not applicable to this vessel (6) Angle of equilibrium not to exceed- (i) 7 degrees for flooding of one compartment; 0.00 0.00 0.00 0.00 (ii) 12 degrees for flooding of two compartments; or (remaining not applicable to this vessel) (7) The margin line must not be submerged when the vessel is in equilibrium 0.5 0.45 0.42 0.35 (8) Not applicable to this vessel (9) Not applicable to this vessel NOTE: GZ = Righting Arm.

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U.S. Coast Guard (USCG) ship stability regulations governing the ability of a vessel to return to an upright position after being disturbed is the focus of a new TRB publication, Review and Update of U.S. Coast Guard Vessel Stability Regulations and Guidance. The authors advise the USCG on how it can make its stability regulations more usable and complete in meeting the requirements of different types of vessels and those vessels that have undergone weight changes that can affect their stability characteristics.

The USCG has safety regulatory jurisdiction over vessels registered in the United States. One of its oldest regulatory functions is to ensure these ships, boats, and other floating vessels remain upright as they encounter both expected and unexpected loading, operating, and weather conditions, including wind and wave conditions and unexpected failure of watertight integrity.

Stability standards have been improved over time - particularly in the past 30 years - and the USCG remains keenly interested in making sure the regulations are kept updated based on the latest technical knowledge, well aligned with international standards, and organized and presented in a manner that facilitates compliance and enforcement. The recommendations in the report are intended to further these aims. The USCG earlier commissioned a National Academies study to identify options for improving vessel stability regulations, and after receiving that study in September 2018, the USCG asked for this second study to provide more in-depth advice on applying these options.

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