ASTM F3052-14(2020)e1
(Guide)Standard Guide for Conducting Small Boat Stability Test (Deadweight Survey and Air Inclining Experiment) to Determine Lightcraft Weight and Centers of Gravity of a Small Craft
Standard Guide for Conducting Small Boat Stability Test (Deadweight Survey and Air Inclining Experiment) to Determine Lightcraft Weight and Centers of Gravity of a Small Craft
SIGNIFICANCE AND USE
4.1 From the lightcraft characteristics, calculations of the stability characteristics of the small craft for all load conditions can determine compliance to applicable stability criteria or provide mass properties information for other analyses or investigations. Accurate results from an air incline stability test may therefore determine future survival of the boat, the crew and compliment. If the small craft is not 100 % complete or there is fuel or other liquids in a tank that is supposed to be clean and dry then the person leading the stability test must determine the acceptability of all variances from the guide based on the ability to correct for these variances analytically. A complete understanding of the principles behind the stability test and knowledge of the factors that affect the results is therefore necessary.
4.2 The results of the stability test typically supersede the corresponding values in the weight estimate for any subsequent use in ascertaining compliance to stability or weight control criteria and may be used in weight margin adjudication.
SCOPE
1.1 This guide covers the determination of a small boat’s lightcraft characteristics. The air incline stability test can be considered two separate tasks; a deadweight survey and an air-inclining experiment. The stability test is recommended, but not required, for all small craft upon their construction completion or after major conversions, or both, where stability information is required. It is typically conducted indoors and an enclosed facility to protect the vessels from unprotected environmental conditions.
1.2 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.3 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
General Information
Relations
Standards Content (Sample)
This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
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Designation: F3052 − 14 (Reapproved 2020) An American National Standard
Standard Guide for
Conducting Small Boat Stability Test (Deadweight Survey
and Air Inclining Experiment) to Determine Lightcraft Weight
and Centers of Gravity of a Small Craft
This standard is issued under the fixed designation F3052; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
ε NOTE—Keywords were added editorially in February 2020.
INTRODUCTION
Small craft operators, builders, buyers, accident investigators, and others may be required to
determine the centers of gravity for their craft in order to apply stability criteria or perform other
analyses. The conventional in-water stability test can be difficult to perform accurately on small craft,
so an in-air inclining experiment may be specified. However, there are no guidelines available to help
standardize and explain the process.
This guide provides the marine industry with an understanding of an Air-Incline stability test for
small craft. It contains procedures to ensure that valid results are obtained with precision at a minimal
cost to owners, shipyards and the government. The guide is not intended to direct a person(s) in the
actualcalculationsofthelightcraftweightandcentersofgravity,buttobeaguidetotherecommended
procedures required to gather accurate data for use in the calculation of the lightcraft characteristics.
A complete understanding and documentation of proper procedures to conduct a stability test is
paramounttoconfirmthattheresultsgatheredduringthetestcanbeexaminedforaccuracy,especially
by third parties subsequently reviewing the data. This guide is recommended to be used for all small
craft capable of being lifted safely with forward and aft pick points capable of enduring additional
inclining weights to be used for the stability test.
1. Scope 1.3 This international standard was developed in accor-
dance with internationally recognized principles on standard-
1.1 This guide covers the determination of a small boat’s
ization established in the Decision on Principles for the
lightcraft characteristics. The air incline stability test can be
Development of International Standards, Guides and Recom-
considered two separate tasks; a deadweight survey and an
mendations issued by the World Trade Organization Technical
air-inclining experiment. The stability test is recommended,
Barriers to Trade (TBT) Committee.
but not required, for all small craft upon their construction
completion or after major conversions, or both, where stability
2. Referenced Documents
information is required. It is typically conducted indoors and
2.1 ASTM Standards:
an enclosed facility to protect the vessels from unprotected
F1321 Guide for Conducting a Stability Test (Lightweight
environmental conditions.
Survey and Inclining Experiment) to Determine the Light
1.2 This standard does not purport to address all of the
Ship Displacement and Centers of Gravity of a Vessel
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
3. Terminology
priate safety, health, and environmental practices and deter-
3.1 Definitions:
mine the applicability of regulatory limitations prior to use.
3.1.1 deadweight survey, n—comprises weighing the vessel
at two longitudinal points to determine the total weight and
This guide is under the jurisdiction of ASTM Committee F25 on Ships and
Marine Technology and is the direct responsibility of Subcommittee F25.01 on
Structures. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Feb. 1, 2020. Published February 2020. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 2014. Last previous edition approved in 2014 as F3052 – 14. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/F3052-14R20E01. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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longitudinal center of gravity of the craft, then auditing all points. The SRP is where all relative locations of outfit and
items found on board to be added, deducted or relocated on the centers of gravity should be referenced in Fig. 3.
craft at the time of the stability test so the observed condition
3.2 Symbols:
of the small craft can be adjusted to the specified lightcraft
3.2.1 B—vertical distance from SRP to pick points and roll
condition. All loose items or outfit equipment (that is, anchor,
axis/centerline of knife edges.
anchor warp, dock lines, fire extinguishers, etc.) found on
3.2.2 LCG—longitudinal center of gravity measured from
board should be removed completely from the craft and
the SRP.
weighed separately on a calibrated scale.
3.2.3 Tan θ—tangent angle of deflection.
3.1.2 inclining experiment, n—comprises moving a series of
3.2.4 VCG—vertical center of gravity measured from the
knownweightsinatransversedirectionandthenmeasuringthe
baseline.
resulting change in the equilibrium heel angle of the craft.This
information is used to calculate the vessel’s vertical center of
3.2.5 W—W1+ W2, is total weight of the boat.
gravity.
3.2.6 W1—weight in pounds at the aft pick point.
3.1.3 keel(baseline),n—thedatumpointusedformeasuring
3.2.7 W2—weight in pounds at the forward pick point.
the vertical location of the pivot points and subsequently
3.2.8 X—longitudinal distance from stern reference point
defining the vertical location of the weights involved in the
(SRP) to longitudinal center of gravity of the boat.
test. It is often the lowest point of the craft hull, but may be
3.2.9 X1—longitudinal distance from stern reference point
defined as any convenient point, provided it is consistent
(SRP) to aft pick point.
within the experiment, consistent with any other documenta-
tion such as the drawings or weight estimate, and well
3.2.10 X2—longitudinal distance from stern reference point
documented.
(SRP) to forward pick point.
3.1.4 lightcraft, n—a small craft, or boat in the lightest
4. Significance and Use
condition (“Condition 1”) is a boat complete in all respects
without consumables, stores, cargo crew and effects and
4.1 From the lightcraft characteristics, calculations of the
without any liquids on board except machinery fluids, such as
stability characteristics of the small craft for all load conditions
lubricants and hydraulics at operating levels. The lightcraft
can determine compliance to applicable stability criteria or
should be as defined in the craft procurement or other
provide mass properties information for other analyses or
specifications, or in the operating manual, as to outfit perma-
investigations.Accurate results from an air incline stability test
nently aboard, etc.
may therefore determine future survival of the boat, the crew
3.1.5 stern reference point (SRP), n—the intersection of the and compliment. If the small craft is not 100 % complete or
transom and the keel (baseline) of the boat or as otherwise there is fuel or other liquids in a tank that is supposed to be
definedinthedocumentation,butshouldbeclearlydefinedand clean and dry then the person leading the stability test must
determine the acceptability of all variances from the guide
documented in the test report, and should be verified by
physical measurement at the time of the test relative to the lift based on the ability to correct for these variances analytically.
FIG. 1 Typical Incline Plot
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FIG. 2 Measurement of KM, GM, & KG
FIG. 3 Relationships of Pick Points and Center of Gravity
Acomplete understanding of the principles behind the stability experiment. Similar terms are used in some cases based on this
test and knowledge of the factors that affect the results is analogy, but these terms should not be confused with those
therefore necessary. derived from hydrostatic data.
4.2 The results of the stability test typically supersede the
5.2 The Metacenter—The transverse metacenter “M” is the
correspondingvaluesintheweightestimateforanysubsequent
point around which the boat swings through small angles of
use in ascertaining compliance to stability or weight control
inclination (typically 0° to 5°). This is the point at which
criteria and may be used in weight margin adjudication.
transverse movement is not constrained relative to the craft
hull. For example, as shown in Fig. 5, the lift straps constrain
5. Theory
thelowershacklefrommovingtransverselyrelativetothecraft
5.1 This test is analogous to the standard in-water inclining hull,butthereisnosuchconstraintontheuppershackle,sothe
test of Guide F1321 and the basic concepts are similar, but the lower shackle pivots on the contact surface between the upper
information determined by the readings of the scale(s) and the and lower shackles and the metacenter is at their mutual
location of the pivot point are substituted for the hydrostatic contact point, The height of “M” above “K” is known as
properties of the floating vessel in an in-water inclining “KM”. The location of M is fixed over the range of angles of
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FIG. 4 Typical Lifting Arrangement with Pick Point References and Water Tube Location
FIG. 5 Improvised “Knife-Edge” Configuration (Forward and Aft) Pick Points
inclination during the stability test. The intersection between baseline of the boat. Note also that one source of error in this
the bearing surfaces of the shackles is known as the “knife- experiment is inaccurate or inconsistent location of the pivot
edge”. It is imperative that this height, “KM”, be exactly point. It is important the system from the craft hull to the pivot
parallel between the forward and aft pick points and the point be effectively rigid in the transverse plane and the pivot
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point itself be completely free to rotate through the full range nations thereof can be used. At least three independent means
of observed angles of inclination without any binding. of measuring the angle should be used.
5.3 Metacentric Height—The vertical distance between the 5.7 When pendulums are used, the two sides of the triangle
center of gravity “G” and “M” is called the metacentric height,
definedbythependulumaremeasured,“Y”,isthelengthofthe
“GM”.At small angles of inclination, GM is equal to the initial
pendulumfromthepivotpointtotheruledbattenand“Z”isthe
slopeoftherightingarm“GZ”curveandiscalculatedbasedon
distance the pendulum deflects from the initial reference
the relationship:
position along the ruled batten where transverse deflections are
measured. Tangent “θ” is then calculated, see Fig. 6:
GZ 5GMsinθ (1)
tanθ 5 Z⁄Y (7)
GM is a measure of stiffness in roll that can be calculated
during the air inclining experiment. Moving a weight “w”
Plotting the readings during the stability test will aid in the
across the deck a distance “A” will cause a shift in the overall
discovery of a bad shift in weight or deflection. Since Eq 1
center of gravity “GG ” of the small craft equal to:
should be constant, the incline plot theoretically should be a
straight line. Deviations from a straight line are indicators that
w A
~ !~ !
GG 5 (2)
S D
there are other moments acting adversely on the craft or the
W
height of “B” is not the same at the fore and after sling pick
and parallel to the movement of “w”.The small craft will list
points. These errors should be identified and corrected and the
over to a new equilibrium heel angle. Because the angle of
weight shift repeated until a straight line can be achieved.
inclinationduringthestabilitytestissmall,theshiftof“G”can
5.8 Free Surface—During the stability test, the inclining of
be approximated by:
the vessel should result solely from the movement of the
w A
~ !~ !
inclining weights. It should not be inhibited or exaggerated by
GM 5 (3)
S D
W tan θ
~ !
unknown moments of shifting of liquids or on board compo-
nents so all such liquids or other weights should be removed or
Because the GM and weight remain constant throughout the
documented so that they can be corrected for during the
entire air inclining experiment, the ratio in Eq 3 will remain
analysis. Note also that any free surface has the effect of
constant. A series of weight shifts will result in a plot of
reducing the observed roll stiffness of the system, because it is
tangents at the corresponding moments. This ratio is the slope
similar to an additional inclining weight. This means that free
of the best represented straight line drawn through the plotted
surface effects have the effect of raising the observed KG and
points as shown in Fig. 1. The line does not necessarily pass
therefore are subtracted from the observed KG resulting in a
through the origin or any other particular point, for no single
lower lightcraft KG.
point is more significant than any other point. Therefore, a
5.8.1 Tankage During the Air-Inclining—There should not
linear regression analysis should be used to fit a straight line
be any liquids on board with the exception of machinery fluids,
through the points.
such as lubricants and hydraulics at operating levels as defined
5.4 Calculating the Height of the Center of Gravity Above
in the specified lightcraft condition. Unless the exact weight
the Keel—KM remains constant throughout the entire stability
and distance of liquid shifted can be precisely calculated, the
test and is represented as “B”, see Fig. 2. The metacentric
GM from Eq 1 will be in error. Free surface should be
height, GM, as calculated in Eq 3, is determined from the
minimized by emptying the tanks completely and making sure
inclining experiment. The difference between KM and GM is
all bilges are dry. The shifting of fluids within tanks due to the
the center of gravity, KG. Therefore, the center of gravity
entrapment of air or pocketing within a complex tank causes
above the keel is:
considerable errors in the computation of the GM. Note
KG 5 B 2GG1cosθ
especially that tanks near to empty or full may exhibit heeling
moments that vary with the inclining angle as the fluid in the
wA (4)
KG 5 B 2 cosθ
W tank touches the top of the tank or as part of the bottom of a
tank goes dry. These varying moments severely d
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