Westlawn Institute of Marine Technology




Education and Training for Boat Designers, Surveyors,
Technicians & Marine Pro...
Dave Gerr, Director
Westlawn Institute of Marine Technology
          c/o Mystic Seaport
             PO Box 6000
       7...
Some Useful References

Nature of Boats:
Comprehensive coverage of
all aspects of boat design,
construction and behavior.
...
The Problem
a) Numerous small commercial passenger vessels
   operate on inland waters outside the jurisdiction of
   the ...
There are Boats . . .


Some boat’s at least are pretty
obviously properly designed and
built . . .
Imagine 57-Foot Voyaging Motorcruiser
Belle Marie/Summer Kyle 42-Foot Shoal-Draft,
           Beachable Motorcruiser
Kestrel 76-Foot Shoal-Draft, Beachable Motoryacht
And Then There Are . . .




     ??
150 Passengers?
Safe? How Many Passengers?
Stability Standard Must Apply To All


    Regardless of outward appearance, it’s still
    necessary to ensure ALL boats ...
Ethan Allen
              Passenger Deck




Ethan Allen
   40 ft.
Fiberglass
 boat, on
   Lake
George, NY
Ethan Allen Capsize

On October 2, 2005, the New York State
certificated vessel Ethan Allen capsized on Lake
George, NY.
a...
Animation of Ethan Allen Capsize




Animation: JMS Naval Architects & Salvage Engineers - www.jmsnet.com
Ethan Allen After Capsize
NTSB Report - Cause of Ethan Allen Capsize
a) An old (1976) Certificate Of Inspection (COI), which
   permitted 48 passeng...
Lady D Water Taxi
36 ft. LOA, 8 ft. Beam, Pontoon Water Taxi
Lady D Capsize

On March 6, 2004, the inspected passenger vessel
(a pontoon water taxi) Lady D capsized in
Baltimore harbo...
Lady D Capsized
NTSB Report - Cause of the Lady D Capsize
a) The sister ship used for stability assessment in 1999,
   was incorrectly tes...
SCItantic 90-ft. Stern Wheel Passenger Vessel
SCItantic Capsize
On July 7, 1984, the passenger vessel SCItantic (a
90-foot stern wheeler) capsized on the Tennessee
Rive...
NTSB Report - Cause of the SCItantic Capsize

a) The vessel’s GM exceeded USCG
   requirements under CFR 170.170.
b) The v...
CRF 170.173 for Vessels of Unusual Form

a) Plot curve of righting arms against curve of heeling arms
b) Crossing point (p...
NTSB Report - Cause of the SCItantic Capsize

a) The vessel’s GM exceeded USCG
   requirements under CFR 170.170.
b) The v...
Insufficient Stability Can Show Up
  Immediately in Severe Cases




 Home designed and home built boat of all steel.
Insufficient Stability Can Show Up
  Immediately in Severe Cases - 2




As Launching Progressed Something Was Very Wrong!
Insufficient Stability Can Show Up
            Immediately in Severe Cases - 3




The Boat Had Insufficient Displacement ...
Insufficient Stability Can Show Up
             Immediately in Severe Cases - 4




The Boat Was Listing to Port and in Da...
Metacentric Height (GM) and Heeled Center of
               Buoyancy (CB)
Metacentric Height (GM) and Righting Arm (GZ)
Solution – Part 1
Create an Applicable Inland Stability Rule that Will:
 a) Conform with the general principles and requir...
Operating Procedure

a) Designated, approved state personnel will act as
   inspectors to conduct the review, inspection, ...
Stability Rule Name and Availability

The rule will be called:

The Inland Stability Standard or ISS
a) The complete ISS d...
Solution – Part 2
        Create Distance-Learning
     ISS Inspector Training Program:

a) Create a training program—deli...
The Training Program Will:

a) Familiarize inspectors with the need for and meaning
   of stability requirements and testi...
About the Westlawn Institute of Marine Technology
a) Founded 1930 — 80 years this January.
b) Has trained more practicing ...
Boats Designed by Westlawn Alumni
More Boats Designed by Westlawn Alumni
Still More Boats Designed by Westlawn Alumni
The Two Fundamental Stability Criteria

The two primary stability criteria to be met are:
1)Wind Heel: That the boat will ...
Wind Heel
a) For powerboats, use a multiplier in pounds per square foot of wind
   pressure for the appropriate maximum av...
Wind Heel Example Boat
27 Foot Cruiser Inboard Profile
Determine Allowable Heel/Immersion

a) For a flush-deck boat with no cockpit or well
   deck, the maximum heel is 1/2 the ...
Determine Allowable Heel/Immersion 2
The amount of heeled freeboard allowed is determined by the
following formula (from C...
Allowable Heel/Immersion for the 27-Foot Cruiser

LOD is not the same as LOA. LOD is the length of the
deck itself and is ...
Understanding the Allowable Immersion Results
a) From the sections, the lowest freeboard happens to be at the transom on
 ...
Calculating the Heel Angle from Wind Pressure

The heel angle from the wind pressure can be found from:


Heel angle, degr...
Wind Pressures for Wind-Heel Calculation

Use wind pressures (P) as follow for the intended
boat use:
Ocean crossing (50 k...
Martin’s Wind-Pressure Formula

Wind pressure for a given wind speed is
found from Martin’s formula which is:

P = 0.004 x...
27-Foot Cruiser Wind Heel Area




2.63 ft. + 0.66 ft. = 3.29 ft. HA (heeling arm)
27-Foot Cruiser Wind Heel Calculation

Though we’re discussing inland boats, this is rugged
little cruiser intended for ve...
Passenger Heel
a) Passenger heel determines how far the boat will heel with the
   passengers moved to one side of the boa...
Calculating Passenger Heel

The angle of heel resulting from moving weights already
aboard a boat a given distance is foun...
Passengers to One Side of the 27-Foot Cruiser
Passenger Heel for the 27-Foot Cruiser

Say we have total crew of 8. Two thirds of this is 5.28,
say, 6.
Six times 185 pou...
USCG/CFR Wind Heel Criteria – “GM Weather”


a) The preceding works out the naval
   architects calculations.
b) Passenger...
CFR 170.170 – “GM Weather”

                       GM ≥ P x A x h
                            W x tanT
Where:
GM = metacen...
“GM Weather” Wind Velocities

The wind velocities in P for the factors 0.005,
0.0033, and 0.0025 are (using Martin’s formu...
CFR 171.050 – “Passenger Heel”
      GM ≥                Nxb
             24 passengers/long ton x W x tanT
Where:
GM = me...
What’s Needed for ISS (Inland Stability Standard)

 a) What we’ve done is review the principles
    underlying stability r...
Base ISS Primarily on CFR 171.030 “Simplified
Stability,” with Reference to 171.170 and 171.050
              and ABYC as ...
a) Maximum Allowable Heel
The amount of heeled freeboard allowed is determined by the
following formula (from CFR 178.330)...
b) Determine Passenger Heeling Moment
Two thirds of 8 crew = 5.28. Use 6.
Six x 185 lb.= 1,110 lb.
1,110 lb. x 2.8 ft. to ...
c) Determine Wind Heel Moment

2.63 ft. + 0.66 ft. = 3.29 ft. HA (heeling arm)
10.7 lb/sq.ft. wind pressure x 125.3 sq.ft....
d & e) Incline Boat with Weights to the
               Larger of the Moments
a) Mark hull side with grease pencil at max. ...
Checking Maximum Heel Angle


a) The mark on the side of the hull is maximum
   immersion relative to freeboard and cockpi...
46 CFR, ASTM Heel-Angle Measurement Procedure
Under the CFR, per the ASTM standard, the heel angle must be
measured with 3...
ISS Heel-Angle Measure Using Digital Levels
The CFR/ASTM pendulum method was created decades ago. ISS
will move to using 3...
Other Considerations in ISS Test


a) Proper scupper drainage, per
   ABYC H-4 Cockpit Drainage
   Systems
b) Openings nea...
Other Vessel Types for ISS

This discussion has been for monohull
powerboats. Other types of boat to be covered:
a)Monohul...
Upcoming SlideShare
Loading in …5
×

Stability Standards and Testing of Commercial Vessels on Inland Waters (ISS)

4,471 views

Published on

The new Inland Stability Standard that the Westlawn Institute of Marine Technology is developing for NASBLA is discussed and also the cost-effective training program being developed to equip state law-enforcement personnel to inspect and approve such vessels' stability as either safe for operation or unsafe and not approved. Implementation of ISS and the associated training program will serve to close this gap in safety standards, provide firm guidance for state regulators to enhance public safety.

Published in: Education, Business, Travel
0 Comments
1 Like
Statistics
Notes
  • Be the first to comment

No Downloads
Views
Total views
4,471
On SlideShare
0
From Embeds
0
Number of Embeds
18
Actions
Shares
0
Downloads
106
Comments
0
Likes
1
Embeds 0
No embeds

No notes for slide

Stability Standards and Testing of Commercial Vessels on Inland Waters (ISS)

  1. 1. Westlawn Institute of Marine Technology Education and Training for Boat Designers, Surveyors, Technicians & Marine Professionals – www.westlawn.edu
  2. 2. Dave Gerr, Director Westlawn Institute of Marine Technology c/o Mystic Seaport PO Box 6000 75 Greenmanville Avenue Mystic, CT 06355 USA Tel: 860-572-7900 Fax: 860-572-7939 Email: dgerr@westlawn.edu Web: www.westlawn.edu
  3. 3. Some Useful References Nature of Boats: Comprehensive coverage of all aspects of boat design, construction and behavior. Easy read. Non technical. Boat Mechanical Systems Handbook: Straightforward reference on all aspects of boat systems engineering. Elements of Boat Strength: Easy to use and comprehensive reference for evaluating and calculating boat structures.
  4. 4. The Problem a) Numerous small commercial passenger vessels operate on inland waters outside the jurisdiction of the U.S. Coast Guard and the Code of Federal Regulations (CFR) governing such vessels under 46 CFR. b) There is currently no generally recognized stability standard applicable to such inland commercial vessels. c) The states seldom have personnel trained to apply 46 CFR stability requirements or assess the safety of a boat with regard to stability. d) Lack of standards and lack of trained personnel leaves a gap in public safety for commercial passenger vessels operating on inland waters.
  5. 5. There are Boats . . . Some boat’s at least are pretty obviously properly designed and built . . .
  6. 6. Imagine 57-Foot Voyaging Motorcruiser
  7. 7. Belle Marie/Summer Kyle 42-Foot Shoal-Draft, Beachable Motorcruiser
  8. 8. Kestrel 76-Foot Shoal-Draft, Beachable Motoryacht
  9. 9. And Then There Are . . . ??
  10. 10. 150 Passengers?
  11. 11. Safe? How Many Passengers?
  12. 12. Stability Standard Must Apply To All Regardless of outward appearance, it’s still necessary to ensure ALL boats meet basic stability requirements. Insufficient Stability Can Be Deadly!!
  13. 13. Ethan Allen Passenger Deck Ethan Allen 40 ft. Fiberglass boat, on Lake George, NY
  14. 14. Ethan Allen Capsize On October 2, 2005, the New York State certificated vessel Ethan Allen capsized on Lake George, NY. a) The operator and 47 passengers were aboard. b) 20 passengers died. c) 3 passengers suffered serious injury. d) 6 passengers suffered minor injuries. e) The operator and 18 passengers survived without injury. The weather was good and conditions on the lake were calm with very light winds.
  15. 15. Animation of Ethan Allen Capsize Animation: JMS Naval Architects & Salvage Engineers - www.jmsnet.com
  16. 16. Ethan Allen After Capsize
  17. 17. NTSB Report - Cause of Ethan Allen Capsize a) An old (1976) Certificate Of Inspection (COI), which permitted 48 passengers, was accepted by the state without a new stability test. b) Modifications had been made to the vessel but were not reported to the state. c) Post accident stability tests indicated that the vessel had a high center of gravity (CG) and marginal metacentric height (GM). d) The boat had a 2-degree list to port, prior to the capsize to port, and was down by the bow by almost a foot! This reduced the waterplane moment of inertia and so further reduced the initial stability. e) The capsize was caused by INSUFFICIENT STABILTY.
  18. 18. Lady D Water Taxi 36 ft. LOA, 8 ft. Beam, Pontoon Water Taxi
  19. 19. Lady D Capsize On March 6, 2004, the inspected passenger vessel (a pontoon water taxi) Lady D capsized in Baltimore harbor. a) 3 crew and 23 passengers were aboard. b) 5 passengers died. c) 4 passengers suffered serious injury. d) 12 passengers suffered minor injuries. The weather was poor, with rain, developing strong winds and nearby thunderstorms.
  20. 20. Lady D Capsized
  21. 21. NTSB Report - Cause of the Lady D Capsize a) The sister ship used for stability assessment in 1999, was incorrectly tested using methods applicable to monohulls not to pontoon boats. b) Test weight had not been moved as far outboard as possible in the test. c) The USCG granted incorrect sister-vessel status to the Lady D based on the incorrect stability tests. d) Passenger weight for the stability tests was based on 140 lb./passenger, per regulations, but average passenger weight was 168 lb. at the time of the capsize. e) Correctly calculated capacity should have been 14 persons total, not 25. f) The capsize was caused by INSUFFICIENT STABILTY.
  22. 22. SCItantic 90-ft. Stern Wheel Passenger Vessel
  23. 23. SCItantic Capsize On July 7, 1984, the passenger vessel SCItantic (a 90-foot stern wheeler) capsized on the Tennessee River, near the Redstone Arsenal, in Alabama. a)3 crew and 15 passengers were aboard. b)11 passengers died. c)7 individuals (3 crew and 4 passengers) escaped with little or minor injuries. The forecast was for the possibility of typical afternoon summer thunderstorms. After leaving the dock, a severe thunderstorm warning was broadcast. By 11:03, winds of 38 knots were reported, and a local downburst/microburst with 70 knot winds then occurred, striking SCItantic broadside.
  24. 24. NTSB Report - Cause of the SCItantic Capsize a) The vessel’s GM exceeded USCG requirements under CFR 170.170. b) The vessel was not of “usual proportions,” however, and so should probably have been require to also meet 170.173. c) The high sided vessel didn’t have sufficient reserve righting energy to withstand 70 knot beam winds. d) The capsize was caused by unusually high winds on a boat with very high cabin sides.
  25. 25. CRF 170.173 for Vessels of Unusual Form a) Plot curve of righting arms against curve of heeling arms b) Crossing point (point of steady heel) not more than 10° (15°-20 sail°) c) Height of RM curve at steady heel no more than 60% of maximum RM d) Residual righting energy (Area A) not less than 140% if Area A2
  26. 26. NTSB Report - Cause of the SCItantic Capsize a) The vessel’s GM exceeded USCG requirements under CFR 170.170. b) The vessel was not of “usual proportions,” however, and so should probably have been require to also meet 170.173. c) The high sided vessel didn’t have sufficient reserve righting energy to withstand 70 knot beam winds. d) The capsize was caused by unusually high winds on a boat with very high cabin sides.
  27. 27. Insufficient Stability Can Show Up Immediately in Severe Cases Home designed and home built boat of all steel.
  28. 28. Insufficient Stability Can Show Up Immediately in Severe Cases - 2 As Launching Progressed Something Was Very Wrong!
  29. 29. Insufficient Stability Can Show Up Immediately in Severe Cases - 3 The Boat Had Insufficient Displacement & Was Severely Down by the Stern
  30. 30. Insufficient Stability Can Show Up Immediately in Severe Cases - 4 The Boat Was Listing to Port and in Danger of Capsizing in Calm Water Right at the Dock!
  31. 31. Metacentric Height (GM) and Heeled Center of Buoyancy (CB)
  32. 32. Metacentric Height (GM) and Righting Arm (GZ)
  33. 33. Solution – Part 1 Create an Applicable Inland Stability Rule that Will: a) Conform with the general principles and requirements of 46 CFR Simplified Stability, and/or to ABYC standards for pontoon boats, or other existing stability standards as applicable and appropriate. b) Be as direct and straightforward to read and interpret as possible. c) Apply only to vessels carrying 149 passengers or less. (Vessels carrying more passengers will be required hire a qualified naval architect, small-craft designer, or marine surveyor to conduct full stability tests under 46 CFR, and present documentary proof of compliance with 46 CFR to the appropriate state regulatory agency to operate in the state.) d) Be applicable to monohull powerboats, multihull powerboats, pontoon powerboats, monohull sailboats, and multihull sailboats. (Pontoon sailboats will not qualify.)
  34. 34. Operating Procedure a) Designated, approved state personnel will act as inspectors to conduct the review, inspection, and tests required to pass stability requirements. b) Upon a vessel’s passage of stability requirements, the state will issue a license or permit to operate while carrying up to the approved number of passengers. c) The license or permit will be good for a limited period (recommend five years) at which time it must be renewed. d) The license or permit will also specifically state that it is void if any alterations or additions are made to the vessel. e) In the event of such alterations or additions, a new ISS will be required for a new license or permit.
  35. 35. Stability Rule Name and Availability The rule will be called: The Inland Stability Standard or ISS a) The complete ISS document will be published in PDF format, available at no cost to for download from the Westlawn Institute website. b) Any state or local agency or organization, any corporation, or any individual may download and post the ISS PDF document on their website, print it out, or distribute it at will. c) The ISS document will state that it is void if altered in any way and must be presented in full.
  36. 36. Solution – Part 2 Create Distance-Learning ISS Inspector Training Program: a) Create a training program—delivered entirely through distance learning— for the personnel who will be conducting the review, inspection, and tests required to pass ISS. b) The course will be supplied and taught by the Westlawn Institute of Marine Technology.
  37. 37. The Training Program Will: a) Familiarize inspectors with the need for and meaning of stability requirements and testing. b) Familiarize inspectors with the overall ISS process, approach, and paperwork. c) Familiarize inspectors with the terminology used in ISS and its meaning. d) Review the complete ISS process step by step. e) Test inspectors knowledge of ISS with an integral series of examinations, including a final exam representing a complete ISS test. f) Award a certificate to graduating students attesting to their successful qualification as an ISS Inspector.
  38. 38. About the Westlawn Institute of Marine Technology a) Founded 1930 — 80 years this January. b) Has trained more practicing boat designers than any other school in the world. c) Nationally accredited by DETC, in Washington DC. d) State approved by the CT Department of Higher Education. e) Recognized by the US Dept. of Education and by the Council for Higher Education Accreditation. f) Was formerly owned by NMMA. g) For the past 6 years part of ABYC. h) 100% of all courses have always been taught via distance learning.
  39. 39. Boats Designed by Westlawn Alumni
  40. 40. More Boats Designed by Westlawn Alumni
  41. 41. Still More Boats Designed by Westlawn Alumni
  42. 42. The Two Fundamental Stability Criteria The two primary stability criteria to be met are: 1)Wind Heel: That the boat will not heel more than between one-quarter to one-half of freeboard, but never more than 14 degrees in the strongest average beam wind it is likely to experience. This is based on CFR (Code of Federal Regulations) 170.170, often termed “GM Weather.” 2)Passenger Heel: That the boat will not heel more than between one-quarter to one-half of freeboard (more later), but never more than 14 degrees with two thirds of the normal passengers and crew permitted aboard standing on one side or along the rail on one side of the boat. This is based on, CFR 171.050, often called “Passenger Heel.”
  43. 43. Wind Heel a) For powerboats, use a multiplier in pounds per square foot of wind pressure for the appropriate maximum average wind speed the boat is likely to experience. b) Take the complete area of the profile of the boat. The designer finds the full area of this in outline including all: stanchions, rails, lee cloths, davits, radar masts, and so on. Also the designer finds the center of the area (CE) above the waterline. c) Next, the designer locates the center of the lateral plane (CLP) of the hull underbody. Measure the distance it is down from the waterline. This can be estimated as 50% of draft on powerboats. d) Add the distance WL to CLP to the distance WL to CE to find the total heeling arm HA. e) Enter this in the powerboat wind-heel formula. The answer should be one quarter to one half freeboard or no more than 14 degrees or less depending on whether it’s an open boat, or a boat with a cockpit, or a flush-deck boat with no cockpit at all. f) If the resulting heel angle is greater, you must either reduce the “sail” area of the boat’s profile, increase beam, or lower the center of gravity, or some combination of these.
  44. 44. Wind Heel Example Boat
  45. 45. 27 Foot Cruiser Inboard Profile
  46. 46. Determine Allowable Heel/Immersion a) For a flush-deck boat with no cockpit or well deck, the maximum heel is 1/2 the freeboard or 14 degrees, whichever is less. b) For a completely open boat with a “cockpit” the full length, the maximum heel is 1/4 the freeboard or 14 degrees, whichever is less. c) Most contemporary boats are largely flush decked but have a cockpit (or a well deck) of some form. For such craft, the maximum heel is somewhere between 1/2 and 1/4 freeboard, or 14 degrees, whichever is less.
  47. 47. Determine Allowable Heel/Immersion 2 The amount of heeled freeboard allowed is determined by the following formula (from CFR 178.330): For exposed waters: immersion = f x ((2 x LOD) - (1.5 x cl)) 4 x LOD For protected waters: immersion = f x (2 x LOD) - cl 4 x LOD Where: immersion = maximum allowable immersion due to heel, ft. f = lowest or minimum freeboard, ft. LOD = length on deck, ft. cl = cockpit length, ft.
  48. 48. Allowable Heel/Immersion for the 27-Foot Cruiser LOD is not the same as LOA. LOD is the length of the deck itself and is almost always less than LOA. For our 27-foot cruiser it is 26.8 feet, not the LOA of 27.5 feet, see drawing. Using the formula for maximum allowable immersion, for our 27-foot motorcruiser, which will operate on exposed waters: 3 ft. freeboard x ((2 x 26.8 ft.) - (1.5 x 8.9 ft.)) 4 x 26.8 ft. = 1.1 ft. allowalbe immersion
  49. 49. Understanding the Allowable Immersion Results a) From the sections, the lowest freeboard happens to be at the transom on this boat. This is 3 feet minimum freeboard. b) The immersion to the 14-degree heeled waterline is 0.9 feet, which is well under half the lowest freeboard (1.5 ft.) and also is under the maximum allowable immersion for this boat of 1.1 feet allowing for the cockpit. c) Accordingly, we use the 14-degree heel angle as maximum allowable. d) If the heeled waterline, at 14 degrees, was higher than half the freeboard or if the immersion depth was greater than 1.1, we would have to find a lower heel angle until we had a heel angle that met all criteria.
  50. 50. Calculating the Heel Angle from Wind Pressure The heel angle from the wind pressure can be found from: Heel angle, degrees = P x 57.3 x Profile Area x Heeling Arm ÷ GM x Disp. Where: Heel angle = degrees of heel P = wind pressure for the selected wind speed, lb./sq.ft. Profile Area = area of the profile of the boat above the waterline, sq.ft. Heeling Arm = distance from center of lateral plane of the underbody to the center of effort of the profile area, ft. GM = metacentric height, ft. Disp. = displacement, lb.
  51. 51. Wind Pressures for Wind-Heel Calculation Use wind pressures (P) as follow for the intended boat use: Ocean crossing (50 knots wind) = 13.2 lb./sq.ft. Coastwise ocean (45 knots wind) = 10.7 lb./sq.ft. Partially protected waters such as lakes, bays, and harbors (40 knots wind) = 8.5 lb./sq.ft. Protected waters such as rivers, inland lakes, and sheltered harbors (35 knots wind) = 6.5 lb./sq.ft. Note: For the U.S. Great Lakes, use coastwise ocean for summer service and ocean crossing for winter service.
  52. 52. Martin’s Wind-Pressure Formula Wind pressure for a given wind speed is found from Martin’s formula which is: P = 0.004 x mph2 or P = 0.0053 x kts2 Where: P = wind pressure, lb./sq.ft. mph = wind speed in miles per hour kts = wind speed in knots
  53. 53. 27-Foot Cruiser Wind Heel Area 2.63 ft. + 0.66 ft. = 3.29 ft. HA (heeling arm)
  54. 54. 27-Foot Cruiser Wind Heel Calculation Though we’re discussing inland boats, this is rugged little cruiser intended for venturing anywhere along the coast and possibly some offshore fishing, so the wind pressure (P) should be based on 45 knots wind, or 10.7 lb./sq.ft. Accordingly: Heel angle = 10.7 lb./sq.ft. x 57.3 x 125.3 sq.ft. Profile Area x 3.29 ft. HA ÷ 3.85 ft. GM x 6,900 Disp. Heel angle = 9.5 degrees. This is well under the 14 degrees we found was allowable and indicates that this boat is is acceptable with regard to wind-heel stability.
  55. 55. Passenger Heel a) Passenger heel determines how far the boat will heel with the passengers moved to one side of the boat. b) The U.S. Coast Guard formula for passenger heel uses 140 pounds per person, assuming a mix of men, women, and children. (Other rules from the CFR use as much as 165 pounds.) c) These weights were settled on decades ago when the U.S. population was physically smaller. d) Over the last few years, there have been a few capsizing incidents where it became apparent that the average weight of the passengers aboard was well over 140 pounds. e) In May 2006, the U.S. Coast Guard issued voluntary guidelines for owners and operators of small passenger vessels to re- evaluate the passenger capacity for their vessels based on an updated average weight allowance of 185 pounds. This has not yet been officially changed in the CFR.
  56. 56. Calculating Passenger Heel The angle of heel resulting from moving weights already aboard a boat a given distance is found from: Heel angle, degrees = arcsin   W lb. x d ft.   Disp. lb. x GM ft.    Where: W = weight moved, lb. d = distance moved, ft. Disp. = boat displacement, lb. GM = metacentric height, ft. arcsin = The arcsin of X is an angle whose sine is X, often notated as sin-1. It is not the same as 1/sine. The arcsin or arc sine can be found quickly on any inexpensive scientific calculator or in any standard spreadsheet program.
  57. 57. Passengers to One Side of the 27-Foot Cruiser
  58. 58. Passenger Heel for the 27-Foot Cruiser Say we have total crew of 8. Two thirds of this is 5.28, say, 6. Six times 185 pounds equals 1,110 pounds shifted to the rail. Then, for our 27-ft. cruiser passenger heel would be: arcsin   1,110 lb. x 2.8 ft.   =6.7 degrees passenger heel  6,900 Disp. x 3.85 ft GM.  Referring back to our earlier calculations for wind heel, we already found that the maximum 14-degree heel was acceptable and so this vessel easily meets passenger-heel criteria.
  59. 59. USCG/CFR Wind Heel Criteria – “GM Weather” a) The preceding works out the naval architects calculations. b) Passenger vessels on the navigable waters of the U.S. need to comply with the CFR exactly. c) This is CFR 170.170, often termed, “GM Weather.”
  60. 60. CFR 170.170 – “GM Weather” GM ≥ P x A x h W x tanT Where: GM = metacentric height, ft. P = wind pressure in long tons per square foot, tons/ft.2 P = 0.005 + (L ÷ 14,200)2, tons/ft.2 for ocean and coastwise service. P = 0.0033 + (L ÷ 14,200)2, tons/ft.2 for partially protected waters such as lakes, bays, and harbors P = 0.0025 + (L ÷ 14,200)2, tons/ft.2 for protected waters such as rivers and harbors L = length between perpendiculars (waterline length for most ordinary boats), ft. A = projected lateral area of boat profile above the waterline, sq.ft. h = vertical distance from center of “A” down to center of underwater area (center of lateral plane), ft. W = weight of vessel (displacement), long tons (tons of 2,240 lb.) T = heel angle = Heel not greater than between one-quarter to one-half of freeboard (as explained earlier regarding cockpit size), but never more than 14 degrees. The amount of heeled freeboard allowed is determined by the formula from CFR 178.330, exactly as discussed earlier.
  61. 61. “GM Weather” Wind Velocities The wind velocities in P for the factors 0.005, 0.0033, and 0.0025 are (using Martin’s formula): 46 knots for ocean and coastwise 37 knots for partially protected waters 33 knots for protected waters The “(L ÷ 14,200)2” factor in the wind-pressure calculation (P) is to increase the wind speed by 0.0458 knots for each foot of boat length.
  62. 62. CFR 171.050 – “Passenger Heel” GM ≥ Nxb 24 passengers/long ton x W x tanT Where: GM = metacentric height, ft. N = number of passengers b = distance from the boat’s centerline to the geometric center of the passenger deck, ft. W = weight of vessel (displacement), long tons—tons of 2,240 lb. The “24 passengers/long ton” makes the following assumptions: That the average weight of all passengers (a mix of men, women, and children) is 140 pounds each, and that 2/3rds of them move to the side of the vessel, so – 2/3 x 140 lb. = 93.34 lb., and 2,240 lb./long ton ÷ 93.34 lb. = 24 passenger/long ton. T = heel angle = Heel not greater than between 1/4 to 1/2 of freeboard (as explained earlier regarding cockpit size from CFR 178.330), but never more than 14 degrees.
  63. 63. What’s Needed for ISS (Inland Stability Standard) a) What we’ve done is review the principles underlying stability requirements and calculations. b) The procedure has to from a foundation for ISS, but . . . 1) It’s too complicated 2) Real displacement (weight) is often unknown 3) VCG (vertical center of gravity) is unknown 4) GM (metacentric height) is unknown 5) There often is no architect’s lines drawing of the hull available.
  64. 64. Base ISS Primarily on CFR 171.030 “Simplified Stability,” with Reference to 171.170 and 171.050 and ABYC as Appropriate Procedure: a) Determine maximum allowable heel b) Determine passenger heel moment c) Determine wind heel moment d) Incline boat with weights to the larger of the moments e) Check that allowable heel or immersion is not exceeded
  65. 65. a) Maximum Allowable Heel The amount of heeled freeboard allowed is determined by the following formula (from CFR 178.330): For exposed waters: immersion = f x ((2 x LOD) - (1.5 x cl)) 4 x LOD For protected waters: immersion = f x (2 x LOD) - cl 4 x LOD
  66. 66. b) Determine Passenger Heeling Moment Two thirds of 8 crew = 5.28. Use 6. Six x 185 lb.= 1,110 lb. 1,110 lb. x 2.8 ft. to one side = 3,080 ft.lb. moment.
  67. 67. c) Determine Wind Heel Moment 2.63 ft. + 0.66 ft. = 3.29 ft. HA (heeling arm) 10.7 lb/sq.ft. wind pressure x 125.3 sq.ft. = 1,341 lb. 1,341 lb. x 3.29 ft. HA = 4,412 ft.lb. moment
  68. 68. d & e) Incline Boat with Weights to the Larger of the Moments a) Mark hull side with grease pencil at max. immersion. b) Place known weights on deck at specified distance from center to create maximum moment. c) Check to see that the boat has not immersed beyond the grease pencil mark or 14 degrees. Wind heel is greatest moment for this boat at 4,412 ft.lb.
  69. 69. Checking Maximum Heel Angle a) The mark on the side of the hull is maximum immersion relative to freeboard and cockpit length, per CFR 178.330 b) It’s also necessary to check the heel angle itself to ensure that the angle isn’t greater than 14 degrees. c) Under the CFR, the ASTM Standard Guide for Conducting Stability Test requires the use of pendulums.
  70. 70. 46 CFR, ASTM Heel-Angle Measurement Procedure Under the CFR, per the ASTM standard, the heel angle must be measured with 3 pendulums set up in buckets to damp out swing. This is complex and cumbersome for use on boats.
  71. 71. ISS Heel-Angle Measure Using Digital Levels The CFR/ASTM pendulum method was created decades ago. ISS will move to using 3 digital levels, to speed up and simplify the heel-angle measurement.
  72. 72. Other Considerations in ISS Test a) Proper scupper drainage, per ABYC H-4 Cockpit Drainage Systems b) Openings near the waterline or in the hull side c) Watertight integrity d) Vessels of unusual form
  73. 73. Other Vessel Types for ISS This discussion has been for monohull powerboats. Other types of boat to be covered: a)Monohull sailboats b)Multihull powerboats c)Multihull sailboats d)Pontoon powerboats (ABYC H-35 Powering And Load Capacity Of Pontoon Boats) Pontoon sailboats will not be covered Vessels carrying more than 149 passengers will not be covered.

×