Submission to Yachting Australia regarding Resistance to Capsize Paper Document Date: 10 Dec 12 Observations 1. Within the first section of the document titled “Step 1. Establish the context” we note the statement “there is a safety risk involved where a yacht cannot resist capsize to approximately 90o, particularly in a Category 5 race.” We agree with this statement and note that our previous submission dated 27/9/12 also raised this concern and highlighted the fact that ISO12217‐2 categories C and D do not require a yacht have any resistance to capsize to 90o whatsoever. 2. Under “Step 4. Treat the Identified Risks”, the second point calls for an RMI index of 0.625 to be reinstated per previous issues of the special regulations. Whilst there is a statement within appendix C referring to the fact that it unknown as to how the current value of 1.1 was arrived at, no reference is provided as to how the value of 0.625 was determined. 3. Within appendix C, Table C1 contains no reference to mast weight. Whilst it is difficult to assess, as no formulae are given for how it is determined, the RA90 values may be inaccurate given this omission. Our on water testing has shown that for small boats, as the mast weight is a large proportion of TM, it makes significant difference. On Water Testing 1. ASBA conducted pull down testing of a range of boats per the attached “RMI TEST DATA” table and photos. Tests were all conducted by AMS/SMS measurers. 2. The HSF values we determined do not match those shown in Table C1. Our values were calculated from measured data using the formula:  HSF = (3 x LOA x Beam2 + 11 x LOA) / IM + 0.2 x Mast Height2 3. The attached “ESTIMATED RMI AND ASSOCIATED DATA” table uses a range of measured data together with an assumption that B is 0.35 x FML below the sheer to generate an estimated RMI for sample boats that were not the subject of a pull down test. Date: 14 May 2013 Page 1 of 4 Conclusions 1. Our on water testing has shown that a range of boats, representing the majority of the ASBA fleet at some recent regattas will not meet the proposed 0.625 RMI requirement, nor will they meet the existing HSF requirement. Therefore, this will leave the fleet in the exact same situation that it currently faces, that being ISO12217‐2 is the only available option to comply with Category 5 and 6 events. ISO12217‐2 Table 2 option 7 (and likely options 5 and 6) allows for boats with zero ballast and therefore allows for no ability to resist capsize beyond their inherent hull form stability. This is in direct contradiction to both the title of Appendix B1 in the Blue Book and the statement referred to in the observations section: “there is a safety risk involved where a yacht cannot resist capsize to approximately 90o, particularly in a Category 5 race.” 2. We recommend that Yachting Australia take the following action: a. Delete reference to Horizontal Stability Factor b. Revise the required RMI to 0.625 for open boats and 0.425 for boats with fully enclosed watertight hulls (i.e. without companionway’s). c. Revise the required ISO12217‐2 compliance to Design Category A, B or C via Table 2, Option 1 or 2 except that the STIX Number shall be increased to XX if calculations show that the current Category C STIX of 14 to be less onerous than an RMI of 0.400. 3. We recommend that the ASBA EC take the following action in lieu of the above taking place: a. At the next AGM (or EGM), propose to revise the ASBA constitution section 4.1.5 From: Resistant to Capsize as defined in Yachting Australia Special Regulations Appendix B to Part 1 using, at minimum, the values as defined for Safety Categories 5 and 6. Boats with moveable ballast shall also satisfy all requirements pertaining to them in Appendix B. Variable ballast is not permitted. To Resistant to Capsize as defined by the formula; RMI = TM / 1.7 x ((2.79 x LOA x Beam2) + (0.05 x I3) + (20.13 x LOA x FML)) / I + 0.5 x FML, where TM is the Test Mass required to hold the mast in a horizontal athwarthships position with the mass suspended at the upper point of I, FML is the freeboard at half LOA and I is the height of the foretriangle from the deck. RMI shall be greater than or equal to 0.625 for open boats with non‐fully watertight hatches and 0.425 for boats with fully enclosed watertight hulls without a companionway. Boats with moveable ballast shall also satisfy all requirements pertaining to them in Appendix B. Variable ballast is not permitted. Date: 14 May 2013 Page 2 of 4 Appendix 1: ASBA Resistance to Capsize Testing Please refer over page Date: 14 May 2013 Page 3 of 4 RMI TEST DATA
Boat Type
Boat Name
LOA
BEAM
FML
I
W
TM
(m)
(m)
(m)
(m)
(kg)
(kg)
Egan 7
Shaw 650 (Home Build)
VX One
Viper 640
Shaw 650 (Production)
Leech 650
Stealth 8
Crank
Monkey Business
One Design
One Design
Lickety‐Split
Stay Tuned
Guided Missile
7.23
6.50
5.82
6.51
6.50
6.50
8.00
3.47
2.50
2.21
2.41
2.50
2.30
3.50
0.70
0.55
0.60
0.55
0.55
0.70
0.57
8.67
6.06
6.03
6.87
6.06
6.43
9.00
71.12
52.71
43.15
46.11
52.71
50.35
73.54
12.40
15.00
16.00
19.20
23.30
29.00
64.30
Stealth 8.5
Sports 8x (Viv)
Melges 24
Thompson 7
Magic 25
Thompson 8
Raptor
Vivace
One Design
One Design
One Design
Zippier
8.50
8.00
7.56
7.00
7.57
8.00
3.50
3.50
2.50
2.50
2.30
2.50
0.70
0.70
0.80
0.75
0.80
0.70
10.00
9.70
9.00
9.00
9.00
10.00
75.60
73.04
52.45
47.91
48.84
49.64
D f
Draft
Est. Bulb
Est. Mast Weight
(kg)
Est. Mast i b
Tip above shear
(m)
EEst. TM
t TM
(kg)
Est. RMI
HSF
Picture Ref #
EG‐100312‐01
RMI
Picture Ref #
0.174
0.285
0.371
0.416
0.442
0.576
0.874
EG‐100312‐01
VX‐XXXX13‐01 to 03
VI‐170313‐01
SP‐XXXX13‐01 to 02
ST‐XXXX13‐01 & 02
n/a
n/a
n/a
n/a
n/a
n/a
ESTIMATED RMI AND ASSOCIATED DATA
Boat Type
Boat Name
Di
Disp
(kg)
(m)
(kg)
Egan 7
Shaw 650 (Home Build)
VX One
Viper 640
Shaw 650 (Production)
Leech 650
Stealth 8
Crank
Monkey Business
One Design
One Design
Lickety‐Split
Stay Tuned
Guided Missile
453
390
300
380
385
390
770
1.89
1.77
1.32
1.37
1.70
1.77
2.16
115
80
70
120
115
115
300
27
18
12
16
18
18
30
10.6
8.2
7.9
8.5
8.2
8.5
11
13.7
14.9
11.3
19.2
25.4
26.2
63.2
0.192
0.283
0.261
0.417
0.482
0.521
0.859
61.8
45.4
37.3
41.4
45.4
41.6
66.6
Stealth 8.5
Sports 8x (Viv)
Melges 24
Thompson 7
h
Magic 25
Thompson 8
Raptor
Vivace
One Design
One Design
One Design
Zippier
498
685
855
800
930
850
2.31
1.98
1.52
1.90
1.70
2.20
120
220
260
350
400
450
30
32
30
30
40
30
12
10.7
9.5
10.3
11
12
14.3
35.8
40.9
72.1
70.5
97.1
0.189
0.489
0.780
1.504
1.443
1.956
69.4
62.3
43.0
44.4
46.8
52.6
VX‐XXXX13‐01 to 03
VI‐170313‐01
SP‐XXXX13‐01 to 02
ST‐XXXX13‐01 & 02
RM/LOA
RM/SA
(kg per m)
Heel
Heel angle
RM
(m2)
(N.m)
(N.m/m)
(N.m/m2)
118
79
47
63
81
76
127
62.7
60.0
51.5
58.4
59.2
60.0
96.3
90
90
90
90
90
90
90
2,131
1,389
906
1,612
1,917
1,996
6,354
294.8
213.6
155.7
247.6
294.9
307.1
794.3
18.1
17.6
19.3
25.6
23.7
26.3
50.0
125
126
89
105
90
126
58.6
85.6
113.1
114.3
122.9
106.3
90
90
90
90
90
90
2,718
4,271
3,875
6,521
6,668
9,708
319.8
533.9
512.6
931.6
880.9
1213.5
21.7
33.9
43.5
62.1
74.1
77.0
T t l SA Disp/LOA
Total SA
Di /LOA
LOA: Length overall
FML: Freeboard at half LOA (waterline to sheerline)
I: Sheer to forestay attachment point
W: W is the theoretical equivalent mass at the upper point of I representing the total effect of the dynamic condition of a storm on a yacht whilst laying on its side
TM: The Test Mass required to hold the mast in a horizontal athwartship position with the mass suspended at the upper point of I
RMI: TM divided by W
Sheer/Sheerline: Refer to ERS D.1
Est. Bulb: Approx bulb weight (excludes fin weight)
RM: Righting moment
SA T l il
(jib
i ki )
SA: Total sail area (jib + main + kite)
Australian Sports Boat Associated RMI Testing
Print Date: 14/05/2013
DESIGN: EGAN 7
NAME: CRANK
REF: EG-100312-01
DESIGN: VX ONE
NAME: THE BEAST
REF: VX-XXXX13-01
DESIGN: VX-ONE
NAME: THE BEAST
REF: VX-XXXX13-02
DESIGN: VX-ONE
NAME: THE BEAST
REF: VX-XXXX13-03
DESIGN: VIPER 640
NAME:
REF: VI-170313-01
DESIGN: STEALTH 8
NAME: GUIDED MISSILE
REF: ST-XXXX13-01
DESIGN: STEALTH 8
NAME: GUIDED MISSILE
REF: ST-XXXX13-02
DESIGN: SHAW 650 (Production version)
NAME: LICKETY-SPLIT
REF: SP-XXXX-01
DESIGN: SHAW 650 (Production version)
NAME: LICKETY-SPLIT
REF: SP-XXXX-01
Appendix 2: Yachting Australia Category 5 and 6 Stability Paper Please refer over page Date: 14 May 2013 Page 4 of 4 COM 9 2010 CMP_Cats_5_6_Stability.docx Page B1
Yachting Australia
APPENDIX A CHANGE MANAGEMENT PROCEDURE (CMP)
Title:
Resistance to capsize requirements for Categories 5 & 6
Initiator
Date 10 Dec 12
Step 1. Establish the context
(What is the hazard/issue/problem/incident)
Background
YA Special Regulations have required monohull yachts entering Category 5 and 6 races to demonstrate
compliance with resistance to capsize requirements by one or other means for over a decade and
continue to do so. This is an Australia-only prescription. ISAF Special Regulations do not have stability
recommendations for these Categories, stopping at Category 4. The currency and continued suitability of
this assessment or alternative methods for Categories 5 and 6 is the subject of this CMP. The current
Australian requirements are:
Category 5 and 6 races:
IMS or ORCi stability index of 103 or greater
Or
ISO or IRC Category A, B or C
Or
IRC SSS Base Value of 8 or greater
Or
SV of 14 or less subject to B.5.1
Or
RMI of 1.1 or greater
Or
Horizontal Stability Factor
The Hazard
The hazard is capsizing and the boat not self-righting, in turn putting undue imposition on local rescue
services. The existence of a hazard to crews in the absence of the enforcement of suitable criteria for
resistance to capsize is in question. Category 5 comprises “races with limited rescue availability, in
protected waters, in daylight hours or in sheltered waters at night”, whereas Category 6 comprises “short
races close to the shoreline in protected waters, in daylight hours only and with effective rescue
availability”. Protected waters “are those not fully exposed to the extremes of the ocean in such a way
that the ocean swell has been broken. It may include large bays and gulfs”. Sheltered waters “are
those sheltered from the extremes of the sea by reefs, headlands or islands. This would infer that the
ocean swell has been broken and that there is limited fetch. It can include harbours, estuaries and
lakes”.
The Issues
The issues to do with the regulation of resistance to capsize for Categories 5 and 6 are adherence by
competing yachts, enforcement by race organizers, practicalities of measurement such as repeatability
and technically proficient measurers, safety of the measurement process and possible risk of damage to
yachts during such measurement. Anecdotally, enforcement by race organizers has been at best patchy
and usually absent over many years.
The Problem
All sizes of monohull yachts compete in Categories 5 and 6 but there is generally growth in numbers of
sportsboats. Notwithstanding the mandatory nature of the resistance to capsize requirements in Part 1 of
the YA Special Regulations, a lack of enforcement by race organizers and attention paid to the
requirements by classes has lead to a design evolution particularly amongst some smaller sportsboats of
high performance that more closely resemble small open ballasted boats as defined in the YA Special
Regulations Part2 For Off the Beach Boats even though this type has a maximum LOA of 6.1m and
almost all sportsboats are longer. It is timely to assess the current resistance to capsize requirements of
Part 1 and as appropriate to endorse, modify or remove them for Categories 5 and 6.
Incidents
COM 9 2010 CMP_Cats_5_6_Stability.docx Page B2
Yachting Australia
This CMP has not come about due to any specific incidents.
Circumstances of safety risk or potential safety risk
Resistance to capsize does not mean that a yacht is self-righting from any angle of heel however the
larger energy required to capsize a yacht that is “capsize-resistant” is normally associated with a
corresponding tendency to self-right from an angle of heel of at least approximately 90° or slightly greater
when the mast touches the water. If a yacht self-rights from such an angle it is self-evident that this is
desirable for crew welfare in the circumstances of a Category 5 race with “limited rescue availability in
protected waters in daylight or sheltered waters at night”. The risk is less in the circumstances of a
Category 6 race, being short and “close to the shoreline in protected waters in daylight hours only and
with effective rescues availability”.
Thus it follows there is a safety risk involved where a yacht cannot resist capsize to approximately 90°,
particularly in a Category 5 race.
These risk circumstances would not exist if the current requirements for resistance to capsize are
effective, practical and enforceable and provided self-sufficiency for a yacht and its crew if capsized
either because it stays afloat and promptly self-rights or remains a safe platform to support the crew
pending the arrival of rescue facilities. Being a “safe platform” also means that it shall not flood through
openings such as hatches and portlights while at a large heel angle (“down-flooding”) which is the first
stage of sinking.
Scope of the circumstances of safety risk
Australia-wide, primarily sports boats but applicable to all
Step 2. Identify the risks if we do nothing.
Risk 1. The boats may capsize and not self right, or may sink, and as a result fail to provide a safe
platform to support the crew.
Risk 2.
Risk 3.
Step 3. Analyse and Evaluate the Identified Risks
Use the Guide in Appendix B.
Risk
Assessed Risk
(Current)
>C+ Risks (Highest to lowest)
Assessed Risk (New)
1. Capsize and resistance to Capsize
B-
1
C+
2.
3.
4.
5.
6.
COM 9 2010 CMP_Cats_5_6_Stability.docx Page B3
Yachting Australia
Step 4. Treat the Identified Risks
For each of the risks in the previous section list possible treatment alternatives. Please identify the preferred treatment option based
on the impact analysis below.
Risk1 Inadequate requirements
1. Amend SR 3.04.1 to require stability documentation to be carried on board in order to increase the likelihood of compliance
2.Amend SR Appendix B2 to revert the RMI requirement for Categories 5 and 6 to 0.625 per previous SR editions. Primarily an
admin change reverting to previous regulatory position
3.Issue safety information notice to clubs on the importance of resistance to capsize, including advice on how to vet
documentation for any given method of compliance
See attached discussion paper Appendix C.
Provide an impact analysis for each of the treatment alternative above. Also attach supporting data, reports, subject matter expert
opinion etc.
Risk1 Alternative 1
Current Situation
New Situation
Part A. Initial impact Analysis (compulsory) – See attached discussion paper Appendix C.
What are the current and proposed
Safety Risk Ratings (refer workshop)?
B-
C+
Does the proposed change impact a
Fleet, Class, Region or all yachts?
All yachts
All yachts
What is the cost of not implementing
(loss of property, lives etc.?
Damage to vessel, minor injury to crew
and the imposition on emergency rescue
Remove imposition on rescue and make
boats more self sufficient
Are any other Special Regulations
impacted?
No
No
What is the impact of the change on
yachting performance?
nil
nil
Is this solution feasible?
Yes
Yes
Yes
Yes
What is the estimated cost of
implementation?
E.g. Can the equipment be sourced?
Does it work somewhere else in the
world?
Is the solution relevant to Australian
conditions?
Is this solution enforceable?
Part B. Detailed Impact Statements (specify which additional Subject Matter Experts might be required and Why)
Detailed Cost/Benefit analysis
Technical support within NSC committee and appointed experts
Review/Interpretation of some Rules
and Regulations
Legal advice
Engineering/Technical advice
Safety Practitioners opinion
Occupational Hygienists opinion
Other (Please specify)
See discussion paper attached
COM 9 2010 CMP_Cats_5_6_Stability.docx Page B4
Yachting Australia
Step 5. MYA or Class Association Review and Endorsement
Reviewed by (MYA CEO)
Name:
Date:
Endorsed by (MYA President)
Name;
Date:
COM 9 2010 CMP_Cats_5_6_Stability.docx Page B1
Yachting Australia
Guideline for Use of Risk Assessment Matrix .
APPENDIX B YACHTING AUSTRALIA GUIDELINES FOR RISK ASSESSMENTS
NOTES:
Only risks identified
with a Final
Assessed Risk Rating
as being greater
than C+ will be
considered for a
Rule Change or New
Rule introduction.
These risks
MUST have a Risk
Treatment attached
to the submission.
Consequence
>10 Fatalities
2-10
Fatalities
1 Fatality (210 Major
injuries)
1 Major
injury
1 or more
minor
injuries
First aid
treatment or
illness/injury
not requiring
treatment
Event
Frequency
Historical
(Likelihood)
Predictive
(Likelihood)
Less than
once every
1000 years
Once every 100
to 1000 years
Once every 10 to
100 years
Unheard of in
the Yachting
industry
Has occurred
once or twice in
the Yachting
industry, but
not in Australia.
Has occurred
many times in the
Yachting industry,
but not in
Australia.
Definition for Use-at MYA Level
More than once
per year up to
and including
10 times per
year
More than 10
times per year
This matrix can be used for the
assessment of all risks identified.
Has occurred once
or twice in
Australia.
Has occurred
frequently in
Australia.
Has occurred
frequently at
specific locations
When there is insufficient data or
considerable difference of opinion at
the Risk assessment Workshop, this
matrix needs to be supported by
additional expert opinion and/or
credible industry statistics.
Expected to
occur at least
once this year if
performing
similar activities
Expected to occur
at least once this
month if
performing
similar activities
Once every 1 to10
years
Not expected
to occur
May occur only
in exceptional
circumstances
Could occur at
sometime but not
likely
Expected to occur
at least once in the
next 10 years if
performing similar
activities
F1
Incredible
F2
Improbable
F3
Remote
F4
Occasional
F5
Probable
F6
Frequent
C6
Disastrous
B-
B+
A
A
A
A
C5
Catastrophic
C+
B-
B+
A
A
A
C4
Critical
C-
C+
B-
B+
A
A
C3
Major
D
C-
C+
B-
B+
A
C2
Minor
D
D
C-
C+
B-
B+
There are 3 options for descriptors
which can be used to determine the
frequency category. One set of
descriptors which can be used to
determine the frequency category. One
set of descriptors is provided for
frequency, one for historical likelihood,
and one for predictive likelihood.
Choose the most appropriate.
To score the risk, follow the steps:
1.Identify the magnitude of the credible
consequences if the risk were to occur.
If applicable, risks should be considered
in terms of the safety (this matrix),
commercial and environmental impact
(using other matrices).
2.Identify the likelihood of this level of
consequence occurring. (This is done
after considering the effectiveness of
the current controls in place)
3. Score the risk using the combination
of likelihood and consequence ranking.
C1
Negligible
D
D
D
C-
C+
B-
Note: Where there are a range of
credible consequences which may lead
to a different level or risks and/or
where the controls may be different. It
may be useful to score the risk more
than once.
YACHTING AUSTRALIA
YACHTING AUSTRALIA SPECIAL REGULATIONS PART 1 FOR RACING BOATS
Change Management Procedure – Resistance to capsize requirements for Categories 5 and 6
Appendix C – Discussion Paper accompanying CMP Appendices A and B
Regulation 3.04 Stability – Monohulls and Appendix B Resistance to Capsize for Monohulls
1. Introduction and Scope
As part of routine review of its Special Regulations, Yachting Australia has initiated a Change Management
Procedure (CMP) for resistance to capsize requirements for monohulls in Categories 5 and 6.
Regulations 3.04.1 and 3.04.3 refer, while Appendix B provides the operative part of the provisions.
Compliance with the requirements is implicit but not mandated. B.3.2 states “a race committee may require the
owner or charterer of a boat to confirm its resistance to capsize ability before accepting its entry”.
Current requirements are:
Category 5 and 6 races:
IMS or ORCi stability index of 103 or greater
Or
ISO or IRC Category A, B or C
Or
IRC SSS Base Value of 8 or greater
Or
SV of 14 or less subject to B.5.1
Or
RMI of 1.1 or greater
Or
Horizontal Stability Factor
Yachts measured to rating rules (ORCi, formerly IMS; IRC) or assessed to ISO 12217-2 (“ISO”) are not within
the scope of this discussion paper as there is presently no suggestion that yachts determined as resistant to
capsize by one of these methods present extra or un-assessed risk if compliant while racing in Categories 5 or
6.
Size of yacht expressed in terms of length and displacement presents a reasonable delineation between yachts
usually measured to a rating rule (ORCi, IRC) or assessed to ISO, and unmeasured or unassessed yachts:
Above LOA = 9.0m and displacement exceeding 1500kg: More likely to be rated to ORCi or IRC
Below LOA = 9.0m and displacement less than 1500kg: Likely to be unmeasured
The exact point of delineation is debatable but analysis of the Australian and international fleet supports this
separation between the “bigger boat fleet” and the “small boat fleet”.
The screening value SV described in B5.1 mandates a practical haul-down test or calculation where
displacement is less than 1500kg.
YACHTING AUSTRALIA
While boats measured to a rating rule or ISO-compliant can and do sail “down” in categories 5 and 6 and are
thus already assessed for stability, unmeasured and un-assessed yachts in the smaller size range as defined
above rarely sail “up” in categories 4 and above.
So the scope of this discussion becomes:
Assess resistance to capsize requirements for unmeasured and un-assessed yachts most often racing
in Categories 5 and 6 with respect to adequacy and risk.
2. Fleet Details
Since the current body of stability requirements for unmeasured yachts was drafted and published, largely
unchanged since the 2001-2004 YA Special Regulations “Blue Book”, the “small boat fleet” as defined above
has evolved and now includes a large proportion of “sportsboats”. Characterized by light displacement, large
sail area, shallow wide hull forms and occasionally, the inclusion of movable or variable ballast (MVB), these
boats have significantly influenced the small boat fleet technical profile.
A study of stability requirements must account for sportsboats as well as the surviving fleet of trailable yachts
found in category 5 and 6 events, which are still numerous.
Example boat type /particulars
VX One
L (m) IM (m) LA (m)
6.0
6.00
6.18
est Disp (L)
(kg)
250
HSF
est Disp (H)
TM >=
(kg)
HBI (m) L (kg)
500
0.55
29
RMI
W
(kg)
48
TM (RMI 0.625) TM (RMI 1.1)
(kg)
(kg)
30
53
RA90 (L) RA (H)
TM625 TM625
(m)
(m)
0.744
0.372
RA90 (L)
TM11 (m)
1.310
RA90 (H)
TM11 (m)
0.655
SV(L)
68
SV(H)
34
Viper 340kg/LOA6.4/HBI0.5 ● Shaw650 /310kg ● Melges
20
6.5
7.50
7.71
350
700
0.63
25
46
29
51
0.636
0.318
1.119
0.560
53
26
T7 600kg ● E7 700kg ● Longtze T6/750kg
7.0
8.60
8.83
525
900
0.70
24
47
30
52
0.497
0.290
0.874
0.510
38
22
T750 760kg ● E770 820kg ● Magic25 845kg ● Melges
24
Lyons 800 Too-Hot-2-Trot
7.5
8.0
9.60
10.33
9.86
10.61
750
1025
1150
1450
0.78
0.85
23
22
49
52
31
32
54
57
0.403
0.335
0.263
0.237
0.709
0.590
0.463
0.417
28
22
18
16
Stealth 850 Raptor
8.5
11.00
11.30
1400
1775
0.91
22
54
34
60
0.274
0.216
0.483
0.381
17
14
Melges 32 ● Mumm 30
9.0
11.50
11.81
1850
2250
0.95
36
63
Example boat type /particulars
VX One/290kg ● Sprint 550/418kg
L (m) IM (m) LA (m)
6.0
6.00
6.18
est Disp (L)
(kg)
250
23
57
HSF
RMI
est Disp (H)
TM >=
W
(kg)
HBI (m) L (kg)
(kg)
500
0.55
29
48
0.227
0.187
0.400
0.329
14
11
RA90 (L) RA (H)
TM (RMI 0.625) TM (RMI 1.1) TM625 TM625
RA90 (L)
RA90 (H)
(kg)
(kg)
(m)
(m)
TM11 (m)
TM11 (m) SV(L) SV(H)
30
53
0.744
0.372
1.310
0.655
68
34
Viper640 380kg/LOA6.4/HBI0.5 ● Shaw650 /372kg ●
Melges 20
6.5
7.50
7.71
350
700
0.63
25
46
29
51
0.636
0.318
1.119
0.560
53
26
T650/730kg ● T7 795kg ● E7 648kg ● Longtze T6/750kg
● Stealth 7/508kg
7.0
8.60
8.83
525
900
0.70
24
47
30
52
0.497
0.290
0.874
0.510
38
22
T750 867kg ● E770 820kg ● Magic25 930kg ● Melges
24 855kg ● E780/883kg
T8 Zippier/ 812kg ● Sports 8/685kg ● Sports 8xx/522kg
7.5
9.60
9.86
750
1150
0.78
23
49
31
54
0.403
0.263
0.709
0.463
28
18
8.0
10.33
10.61
1025
1450
0.85
22
52
32
57
0.335
0.237
0.590
0.417
22
16
Raptor Stealth8.5/ 498kg
8.5
11.00
11.30
1400
1775
0.91
22
54
34
60
0.274
0.216
0.483
0.381
17
14
Melges 32 ● Mumm 30
9.0
11.50
11.81
1850
2250
0.95
23
57
36
63
0.227
0.187
0.400
0.329
14
11
Table C1 – “small boat” particulars. Note: Modern ultra light sportsboats are ordered by length even though
displacements for the longer boats in this category type are much less than the displacement/length trend – this
does not affect W and TM calculation as they are not displacement dependent.
Table C1 collects a sample population of small boats and summarizes the parameters that establish a measure
of resistance to capsize principally in terms of righting arm at 90° heel.
Typical examples of boats are shown in the left hand column with some particulars where known
L = average of overall and waterline length
IM = height from sheer at mast to hounds “upper point if I”
LA = lever arm as shown in figure F1 below
est Disp (L) = empty displacement at light end of range for size
est Disp (H) = empty displacement at heavier end of range for size
HBI = freeboard abreast mast
HSF TM = horizontal stability factor test mass Blue Book B.6
RMI W = theoretical equivalent mass at upper point of I Blue Book B.5.2
TM (RMI 0.625) = test mass to achieve RMI of 0.625 (Blue Book Cat 5 and 6 requirement 2001-2008)
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TM (RMI 1.1) = test mass to achieve RMI of 1.1 (Blue Book Cat 5 and 6 requirement 2009-2012)
RA90 (L) TM625 = righting arm at 90° heel light end of range for size to achieve RMI of 0.625 (2001-2008 rqmnt)
RA90 (H) TM625 = righting arm at 90° heel heavier end of range for size to achieve RMI of 0.625 (2001-2008 rqmnt)
RA90 (L) TM11 = righting arm at 90° heel light end of range for size to achieve RMI of 1.1 (2009-2012 rqmnt)
RA90 (H) TM11 = righting arm at 90° heel heavier end of range for size to achieve RMI of 1.1 (2009-2012 rqmnt)
SV(L) = screening value light end of range for size
SV(H) = screening value heavier end of range for size
Figure F1 – TM measurement
3. Discussion
It is self-evident that if a yacht achieves a positive value for TM then it has a positive righting arm at 90°
and hence will return to upright in still water.
Table C1 reports a noticeable variability in TM values depending on the threshold of acceptance (RM =
0.625 or 1.1). The corresponding RA at 90° for a given TM is dependent on the assumed empty
displacement.
At issue is the “desirable” amount of positive RA at 90°. Designers assign righting moment in order to
achieve satisfactory upwind and reaching sailing performance through power to carry sail and gust-strike
response. Such stability is operative in the range of HA between 0° and say 30° and just as at larger
angles of heel is dependent on the vertical height of the yacht’s centre of gravity and hull shape.
Remaining RA at 90° becomes of interest only when capsize or knock-down recovery is involved:
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Figure F2 – Typical righting arm curve
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For a given boat size defined by L, RA at 90° as displayed in Table C1 varies significantly depending on
displacement and RMI threshold.
For example, a boat such as the VX One, a popular contemporary small sportsboat design in the range of 250500kg displacement, RA90 implied by TM compliance varies from in the order of 0.40m (RMI = 0.625) to in
excess of 1m (RMI = 1.1). Depending on measurement afloat this particular design may well achieve this, as
may others of its type:
Example boat type /particulars
VX One
L (m) IM (m) LA (m)
6.0
6.00
6.18
est Disp (L)
(kg)
250
HSF
est Disp (H)
TM >=
(kg)
HBI (m) L (kg)
500
0.55
29
RMI
W
(kg)
48
TM (RMI 0.625) TM (RMI 1.1)
(kg)
(kg)
30
53
RA90 (L) RA (H)
TM625 TM625
(m)
(m)
0.744
0.372
RA90 (L)
TM11 (m)
1.310
RA90 (H)
TM11 (m)
0.655
An intermediate size yacht such as is found in the group of 7.5m yachts like the Thompson 750 in the range of
750-1150kg displacement, RA90 implied by TM compliance varies from in the order of 0.40m (RMI = 0.625) to
0.7m (RMI = 1.1):
T750 760kg ● E770 820kg ● Magic25 845kg ● Melges
24
7.5
9.60
9.86
750
1150
0.78
23
49
31
54
0.403
0.263
0.709
0.463
The RMI threshold was increased from 0.625 to 1.1 with effect from the 2009-2012 Blue Book. The reasons for
this are not apparent.
In order to gauge “how much” RMI is appropriate for categories 5 and 6, we can look elsewhere for correlation
of stability data against special regulations category and survivability. Survivability has often been suggested to
mean a yacht’s ability to re-right from inversion. Total resistance to capsize is non-existent as there are likely to
be wind and wave conditions in protected and sheltered water environments as described in Appendix A to this
CMP that lead to knock-down and even complete inversion. Of importance is how long it takes for the yacht to
re-right itself, if at all as well as stay afloat so that crew have a refuge until they can re-organise themselves or
until help arrives.
There is a body of measurement data for smaller yachts taken from the ORCi rated fleet. A selection of five of
these in the size range 7.5-9.5m and displacement 1200-2500kg empty displacement is shown in Table C2
below:
Boat
Este
24
Platu
25
JV 4
Buck
Atria
LOA
DSPM
RA90
LPS
Cat
7.495
1199
0.225 106.70
3
7.515
7.512
9.555
8.998
1247
1330
2362
2479
0.657 131.80
0.487 124.4
0.339 110.9
0.373 115.2
1
1
2
1
Table C2 – ORCi small boat sample
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Unfortunately the smallest sportsboats in the Australian fleet are not similarly represented in the ORCi fleet at
this time. The ORCi boats however present a good overlap with the larger and heavier boats in our sample
category 5 and 6 small boat space.
Of particular interest is that the RA90 values in Table C2 are all close to or below 0.5m while in four out of the
five cases possessing sufficient large angle stability (LPS°) to satisfy category 1 or 2 requirements and always
sufficient for category 3.
Table C1 reveals that in almost all instances, SV exceeds 14 (requiring RMI examination) and if these boats
satisfy RMI = 0.625 they have values of RA90 that place them favourably or in company with the ORCi rated
small boats cited here which in turn satisfy at least category 3 by means of LPS.
A greater sample of ORCi small boats would inform this comparison better but this preliminary conclusion is
offered.
The HSF method outlined in B.6 is also included in Table C1. It can be seen that this method is “softer” than
RMI=0.625 as TM is less in all cases. Given that RMI data is “populating” broadly around equivalence with at
least category 3 compliance by the ORCi method and we are only concerned with category 5 and 6, the fact
HSF is softer than RMI=0.625 does not automatically rule it out as inadequate.
The difficulty is that every boat is different and the Australian population of small boats is unmeasured and unassessed in almost all instances.
4. Conclusions
4.1
In the absence of ORCi, IRC or verified ISO12217-2 data, the use of a simple pull-down test for the
assessment of large-angle stability / resistance to capsize for “small boats” (L<9-10m and empty displacement <
~2500kg) with SV exceeding 14 in races held under categories 5 and 6 is recommendedshould be maintained in
the Special Regulations.
4.2
The risk of a knock-down / capsize which may lead to inversion in small boats racing in protected waters is
real. ISO12217-2 Category C is the companion ISO stability criterion for categories 5 and 6, being broadly
analogous and stipulates significant wave heights of up to 2m, and winds up to Beaufort 6 (gusts to 27knots).
These conditions are conducive to a likelihood of capsize that exceeds 10 instances a year in the Australian
fleet with the possibility of at least major injury as found in Appendix B frequency F6/consequence C3 leading to
risk assessment category A. The use of ISO 12217-2 Category C should be maintained in the Special
Regulations.
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4.3
As noted in the introduction, B.3.2 does not make stability assessment mandatory. In order to achieve a new,
modified risk assessment of category B as shown in Appendix A steps 3 and 4, all small yachts with SV
exceeding 14 that are not ORCi or IRC measured must independently demonstrate adherence with the RMI or
HSF method. Race committees should insist on this. Removal of the word “may” and its replacement with the
word “shall” constitutes the change in this CMP. It is recommended that SR 3.04.1 should be amended to
require that documentation shall be carried on board, and SR Appendix B 3.2 should make it mandatory for
clubs to check this documentation.
4.4
Further data will inform these conclusions and may lead to enhancements to this advice but these conclusions
can be adopted as interim and conducive to reducing risk. It is not envisaged that the recommendation to
mandate a pull-down test will be removed by further work.
4.5
The use of RMI=0.625 and HSF are consistent with the recommendation. It is recommended that SR Appendix
B 2 be amended to reinstate the RMI value to 0.625 in accordance with previous editions of the Special
Regulations.