INTERNATIONAL SMALL CRAFTINDUSTRY CONSULTATION AND

VALIDATION STUDY

ISO/DIS-12215-9 Hull Construction – Scantlings –Part 9: Appendages and rig attachment.Validation against existing boats - (Fixed ballast FRP yachts ONLY)

Supported by

The European Boating Association

International Sailing Federation

Royal Yachting Association

27 March 2009

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REPORT TITLE

INTERNATIONAL SMALL CRAFT INDUSTRY CONSULTATION AND VALIDATION STUDY.ISO/DIS-12215-9 Hull Construction – Scantlings – Part 9: Appendages and rigattachment. Validation against existing boats. (Fixed ballast FRP yachts ONLY)

SUMMARY

This report describes the results of an industry consultation exercise conducted betweenOctober 2008 and March 2009. The objective was to obtain feedback and actual boat data forfixed keel, composite yachts and compare these against the current requirements of ISO/DIS-12215-9.

Twelve companies were targeted and asked to supply input for two boats each, which wouldhave yielded data for 24 boats. In the event 9 boats were received from five organisations.Additional discursive feedback was received from several companies. Further valuablefeedback was obtained by the attendance by one company at a working group 18 meeting inNovember 2008 and by others at a number of meetings outside WG18 organised by the group’sconvenor.

Given the data made available, the validation is considered suitable for spot-checkingpurposes. The plots of minimum compliance factors should be viewed collectively to give anoverall impression of ISO/DIS-12215-9 requirements versus the diverse range of industrypractices. Industry practice for keel design is expected to vary from use of past-experience/rules of thumb, class rules (with or without class involvement) up to full finiteelement analysis using measured loads. Against this backdrop considerable variations are to beexpected. Viewed overall, the scantling requirements of ISO/DIS-12215-9 seem to bereasonable and there is sufficient evidence to conclude that part 9 is ready for progression toFDIS as far as the fixed keel component is concerned. From previous experience with earlierparts of ISO-12215, progression to FDIS is usually followed by increased levels of interest fromthe industry and this is expected to be the case with part 9.

DISTRIBUTION UNRESTRICTED ISSUE DATE 27 March 2009

AUTHOR: R Loscombe, CEng, FRINA. navalarchserv@ntlworld.com

DISCLAIMERThis report is for information only and is only to be used for ISO/DIS-12215-9 developmentpurposes. The results may not be used to support or otherwise any existing keelconfiguration. ISO/DIS-12215-9 may not be referred to as an International Standard and thisdraft does not constitute an ‘advanced draft’ under the meaning of RSG guidelines.

Supporting organisations

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1. BACKGROUND

1.1 ISO-12215

ISO-12215 is a nine part small craft scantling standard which has been under development sincethe early 1990’s. The standard is being developed by Working Group 18 (WG18) under theconvener-ship of Gregoire Dolto of Fédération des Industries Nautiques (France). Parts 1-6 havebeen harmonized and may be referred to as ‘International Standards’. DIS and FDIS denoteDraft and Final Draft international standard respectively, with DIS being a pre-FDIS version.The FDIS version is the draft voted on by the national standards bodies concerned. Revisionsafter harmonization are generally at five yearly intervals unless a safety issue is identified inthe interim period.

1.2 ISO/DIS-12215-9

Full title: Hull construction – Scantlings – Part 9: Sailing craft – Appendages and rigattachment. Part 9 is currently at the DIS stage. The intention is to develop the FDIS by May2009 for approval by WG18 at the 18th June meeting in London.

Part 9 covers keels and their attachment for keel boats and dinghies, dagger boards,chainplates, foundations, mast steps and other associated structure. The only items covered inthis report are fixed ballast keels and their attachment.

The Royal Yachting Association has supported the attendance of one of its staff at WG18meetings since 2001. In addition, it has been their practice to use advanced drafts of 12215 forRCD scantling assessments, as permitted under RSG guidelines, as part of its role as a notifiedbody. ISO/DIS-12215-9 has been used on an informative basis to complement other methods(where these exist). In this way, the requirements of the draft have already been comparedwith actual boat keel configurations and found to give good agreement for 12-18m productionyachts. The current industry-wide validation therefore is only one in a series of ongoingvalidation exercises. Accident investigation reports have also been reviewed as these becomeavailable.

1.3 Industry consultation project

This project commenced in the autumn of2008 following the WG18 meeting in Berlin atwhich time the working group judged thatthe development process would benefit mostfrom a targeted industry-level validationexercise.

A number of key leaders in the field of fixedkeel structures were identified andcontacted. Of these, twelve indicated awillingness to assist either directly by emailcontact with the report’s author or asrelayed indirectly by the convenor.

Each was asked to identify only TWO boats asbeing representative of their range or ofspecial interest to them. This was intendedto give a good spread of types/sizes andminimise their time commitment.

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Companies were supplied with a spreadsheetdeveloped by WG18 at the end of November 2008which was intended to reduce the labour involved.The workload was estimated to be no more than ½-1day for the two boats, if the data was readily tohand.

Due to external time pressures (see 1.4) a ‘deadline’notification for end of January 2009 was sent tocompanies at the end of 2008 and subsequentlyextended to the last quarter of February. A finaleffort to gathering in outstanding boats was made inMarch.

In the event, data for nine boats were received by the deadline as follows: Finland (2), France(4), New Zealand (2) and UK (1). The quality/consistency of data often required someintuitive ‘work-arounds’ by the author. This was done without compromising the integrity ofthe process, since one can only take so much of company’s time. The data is considered to beof sufficient quantity and quality to render the validation study meaningful, given that only anoverview is being sought here.

Several companies provided general feedback in respect of canting keels, fatigue-based designand composite laminate requirement in way of keel bolts. Two companies were unable toassist since the spreadsheet did not cater for their keel types being tray or recessed types (see1.5).

Of course, it is understood that companies have to balance issues of client confidentiality,diversion of their staff from fee-earning work and the limited incentives for releasing theirexpertise into the public domain. On the other hand, there is no question at this stage of ISO-12215-9 being ‘dropped’ so everybody needs to work together to make it as good as it can be.It seems likely given the importance of keel structures, that even those companies who did notsupply data or reply in anyway will have taken a thorough look at the requirements and it maybe presumed (perhaps optimistically) that they are reasonably content.

1.4 International Sailing Federation (ISAF) agenda

Following a number of incidents with lost keels combined with the effective loss of theAmerican Bureau of Shipping’s plan review service some years ago, ISAF voted in November2008 to institute a plan review for 0, 1 and 2 category boats. This is to be based on ISO-12215and is due to commence in June 2009.

This (together with the useof 12215 within the Volvo 70rule) has swung the ‘centreof gravity’ of the ISOscantling standard moretowards all-out racing yachtsaway from production craftthan would otherwise havebeen the case. The ISAFdecision has also imposed aneed for part 9 to be issuedas a FDIS as soon as possible.

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1.5 Part 9 limitations

In developing part 9, WG18 have moved away from the part 5 approach whereby ‘the designpressures given in this part of ISO 12215 are only (to be) used with the given equations’. Thisis because the design loads in part 9 are more independent of the selected is the case with thepressures of part 5. The four key ballast keel load cases are:

90 degree knockdown (fixed keels) 70 degree maximum cant angle plus 40% overload factor (canting keels) Vertical force (up only) Longitudinal grounding (normal and enhanced resistance)

The allowable stress factors are set at a level which should generally mean an explicit fatiguelife assessment is not necessary, although an informative annex detailing one fatigue lifeprediction method is included. See discussion. Designers are free to use a range of alternativemethods such as ‘deflection-compatibility grillage theory’, matrix-displacement or finiteelement methods.

However, it would be an excessive burden if such more advanced methods were IMPOSED onall users of the standard. To counter this part 9 provides a series of ‘strength of materials’level beam theory based procedures. It is these which are implemented within the keelcalculator spreadsheet.

These methods are intended to be conservative and are limited in their scope. The part 9annexes assume that the floors carry the transverse load. Version two of the spreadsheet (notsupplied to companies in November 2008) includes an algorithm for distributing the groundingload between the floors and girders. This was derived from simple grillage analyses but is onlyapplicable to one centreline or pair of closely spaced girder.

Keels which fall outside the applicability of part 9 annexes: Recessed keels Multiple girder tray-moulding style keels Lifting keels, particularly keel boxes

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There is no simple engineering method for analyzing these, leaving the choice between rules ofthumb/experience (which puts these types outside the scope of 12215-9) or finite elementanalysis. It is not possible to develop simple methods for every configuration meaning there isno alternative, if the keel is to be ‘engineered’, but to apply suitable computational methods.At least part 9 provides loads and criteria.

2. RESULTS

2.1 Actual boats used in validation exercise

All are category A, with lengths between 8 and 20 metres. Indicative hull lengths, full loaddisplacement and ballast ratio and keel type are provided within this report. To furtherpreserve confidentially, boats are labelled A to I and can only be identified by the originators.

2.2 Assessment conditions

Of the nine boats supplied two used grillage-derived floor and girder moments/forces. This maywell be representative of industry design practices. Where supplied, these grillage calculations(and other studies carried out by the author) indicate that the simplified annex ‘isolated floor’approach is only slightly conservative for transverse bending load cases and but excessively sofor the longitudinal grounding case. Of course where no girders exist, the isolated floorassumption is likely to be less conservative (although the role of the rigid CL girder, aka thekeel fin is another issue).

For validation purposes, the spreadsheet provides an approximate equation for distributing theload between floors and girder(s) (for the grounding load case only). This equation was derivedby matrix-displacement analysis of various floor/girder combinations varying end conditionsand flexural rigidity ratios (approximately 80 configurations).

1 girder x 3 floors 2 girders x 4 floors1 girder x 4 floors2 girders x 3 floors

F

G

n

j jF

FEF

n

i iG

GEF

GFSR

LEIk

LEIk

K

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Of course, this is only an approximation, showing the expected fair amount of scatter and therecommended approach is to model the grillage in 3-D so that loads may be applied directly tothe keel rather than the grid (see figure on page 4). In practice, users will be able to submittheir own estimate of the load share between floors and girders. Without a grillage analysis,this can only be intuitive and hence the equation-fit to the above data is considered to be agood intermediate approach between guesswork and rigorous 3-D analysis. It will be up to theworking group to decide whether the load-share equation should be included within thestandard.

Two companies (of the five) supplied their own floor/girder offered capabilities (EI, ultimatemoments in crown tension or compression and web shear force). In one case, the designerconfirmed that these were based on the ABS Offshore Racing Yacht Guide equivalent thicknessfor sandwich plating which is considerably more generous than the ISO-12215-5 approach. Inthis validation, these have been replaced by ISO-12215-5 Evaluation level B mechanicalproperties, except in two cases where the designer supplied only final compliance table for oneboat and no laminate schedules for the other. In this second case, the company values havebeen used.

This combination of reasonably achievable mechanical properties and conservative isolatedfloor method are considered to provide a fair ‘middle of the road’ comparison, neither too‘high-tech’ nor excessively conservative. This is the design/assessment approach which manyproduction builders are expected to adopt as it involves the minimum level of deviation fromthe standard and no recourse to more advanced stress analysis methods.

2.3 Presentation of results

Results are presented as MINIMUM compliance factors (ratio of offered value to ISO/DIS-12215-9 required value or limiting stress divided by actual stress). As capabilities are reduced by thelimiting stress factor, a compliance factor of 1.0 indicates NOT that there is no margin ofsafety, but that the offered scantling JUST complies with the requirements of part 9 (whichhave a margin of safety factor built in).

COMPLIANCE FACTOR = 1.0 (component JUST complies)COMPLIANCE FACTOR < 1.0 (component does not comply)COMPLIANCE FACTOR >> 1.0 (component easily complies)

A histogram is provided for each boat for 9 ‘critical’ items:

Minimum CF for floors under knockdown moment (Load case 1 – LC1) Minimum CF for floors under longitudinal grounding (normal) – (Load case 4 – LC4/I) Minimum CF for floors under longitudinal grounding (enhanced) – (Load case 4 – LC4/II) Minimum CF for girders under longitudinal grounding (normal) – (Load case 4 – LC4/I) Minimum CF for girders under longitudinal grounding (enhanced) – (Load case 4 – LC4/II) Minimum CF for keel bolts under knockdown moment – (Load case 1 – LC1) Minimum CF for keel bolts under longitudinal grounding (normal) – (Load case 4 – LC4/I) Minimum CF for keel bolts under longitudinal grounding (enhanced) – (Load case 4 –

LC4/II) Minimum CF for the fin at root under knockdown moment – (Load case 1 – LC1)

The vertical load case is rarely critical from this study and so results are not reported here.Keel flange and bulb-fin connections are also not reported as this information was not suppliedin general by the companies. However, tentative calculations were made for fin-bulbconnection using four horizontal bolts of the same diameter/material as the keel bolts, located

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equidistance along the tip chord and in most cases this gave compliance factors marginallygreater than one under bulb deceleration loads in grounding.

As these are minimums it should be recognised that other components are likely to have higherCF’s. In a real RCD assessment for example, it may only be necessary to introduce localisedreinforcement in order to produce a fully compliant boat.

The laminate in way of the keel has been reputedly an issue in a number of keel loss incidents.It is also one of the most difficult areas to rigorously analyse, at least within the zero R&Dbudget available to WG18.

It is considered to be too important an area to neglect and yet it is an area in which it seemsclassification societies prefer to work on a case by case basis rather than provide extensivedesign equations. WG18’s preferred approach is to provide indicative values within theAnnexes. These should be taken as indicative of reasonable practice and the intention is toflag this up as an important issue for designers. However, it is NOT intended that these shouldbe interpreted as ‘cast-in-stone’ figures.

As there are numerous criteria (backing plate diameter and thickness, hull thickness, lappingtray requirements, location of bolt with respect to floor/girder webs and load case, boltforce), a ‘compliance map’ is provided whereby red means non-compliance, green compliance.This provides an ‘at a glance’ indication as to the extent to which the structure complies.

The ‘map’ assumes that the same backing plate/laminate/tray configuration is applied for allbolts. This of course need not be the case and many ‘red’ areas may simply require localreinforcement. There is also some uncertainty about the integrity of the supplied data in thisarea.

THE RESULTS FOR THE NINE BOATS ARE GIVEN IN APPENDIX I. No attempt is made to drill downinto particular areas of non-compliance. This is only worth doing is there is 100% confidence inthe supplied data and this is not the case. In reality, the only way to do this is to supply plansand material test data reports.

3. DISCUSSION POINTS

Please note; the opinions expressed here are those of the author and do not necessarilyrepresent the views of working group 18. This section is included to provide some widerperspective than merely reporting the validation results. Comments from readers arewelcomed, especially if this comes in the form of validated equations or solid data.

3.1 What constitutes a ‘good’ result

It will be noted that there are areas of non-compliance amongst the nine boats. This is to beexpected and is not wholly unwelcome (in the author’s opinion only) for the following reasons:

1. It must be recognised that keel attachment is too important for the standard to beseen as a ‘rock-bottom’ minimum. A bit of healthy conservatism is seen as theresponsible course of action. The risk of users ‘designing down to a minimum standard’should not be ignored, a particular concern if ‘design by experience’ is replaced by‘handle-turning’ of the Annex/spreadsheet-level method. As experience is gained withthe standard (see conclusions) it may be possible to adjust the requirements on thebasis of well documented case studies, but this should not be done on the basis of anine boat study.

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2. The validation uses the annex methods of part 9. There is some evidence gleanedduring development of the standard and in discussions with companies that thesemethods are conservative in comparison with 2-D and 3-D numerical methods. Thereshould be some incentive for designers to use more theoretically sound procedures andit believed that many structural specialists will welcome the ‘edge’ this flexibilityprovides.

3.2 A suggestion as to how part 9 should be used

This last point is seen as critical. Keel grids are complex structures. The components do notbehave as isolated beams. ISO/DIS-12215-9 recognises this by permitting more rigorous stressanalysis methods. Stress distributions around keel bolts/backing plates are complex andcannot be accurately represented by simple equations of the sort contained in part 9 annexes.

The part 9 annexes (as implemented within the validation spreadsheet) cannot assess recessedkeels, keel boxes, canting keel ‘wet’ compartment bulkheads or complex grillageconfigurations. What the annexes aim to do is to supply a simple, inexpensive not excessivelyconservative assessment tool for assessing the vast majority of conventional fixed ballastsupported principally by floors with one or two ‘tie-ing’ girders close to the centreline.

ISO/DIS-12215-9 = Simple holistic (and conservative) procedures for production boatbuilders +Loads + criteria + guidance on advanced engineering methods for structural specialists

It must be recognised that the standard, even if eventually harmonised, should not be regardedas ‘the only way’. A tick-box compliance mindset must be avoided at all costs and assessmentbodies, such as notified bodies assessing for RCD compliance or ISAF approved notified bodiesmust possess the engineering competence to review designers/builders alternative methodswhen these are presented.

While ISO/DIS-12215-9 should be seen as an assessment load-criteria based method, allowingsome flexibility in the stress analysis methods for those that want it, this does not relievedesigners of their responsibility to work within ISO-12215-5 in terms of grid properties, e.g.evaluation levels and effective plating.

3.3 Background to the stress factor (agreed by WG18)

The stress factor is currently set at about 1/3rd of ultimate for metals, wood and composite. Ithas been set at this level to effectively reduce the need for an explicit fatigue life prediction.Guidance for this is currently provided within the standard, but it is a difficult calculation sinceit requires a lifetime stress range v number of stress cycles history. By setting the stress levelat a low level for infrequently occurring load cases, fatigue life becomes less of an issue. Thisis not necessarily the case for very high strength steels or where the structural configurationcontains significant local stress-raisers. Again, ‘just ticking the part 9 boxes’ may not beenough for all keel configurations.

3.4 Background to the load cases (under consideration by WG18)

The load cases have been exhaustively checked against current classification society practiceand design methods (where these were divulged). The transverse bending load cases (90degree knockdown -fixed, maximum cant angle plus 40% dynamic overload factor -canting) areconsidered to be well grounding in existing methods and ‘real’ load cases.

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The most contentious load case is the fore and aft grounding (load case 4). This has been partof the ABS ORY guide for 20 years, albeit subject to various interpretations/amendments overthat period.

The current F4 formula has been extensively checked against other methods, but this is stillhighly non-scientific.

F4-ENHANCED = 0,8 g mLDC (LWL/10)1/2 N (with FRP stress factor of 0,33)

Using ABS at LWL = 20m, (assuming 35% ballast ratio) and stress factor = 0,5, would yield acoefficient of 1,95 x 0,33/0,5 /1.414 = 0,91

Using DNV Large yacht rule, (assuming 35% ballast ratio) and stress factor = 0,5, would yield acoefficient 1,495 x 0,33/0,5 /1.414 = 0,7

It is not possible to relate the speed directly to grounding force and in any case this would bemeaningless as a low speed impact on rock may be more damaging than a high speed impact onmud. The mechanics of impact of yachts with containers, berg-bits or whales defies simpleanalysis. Solid mechanics would need to be factored in - quite inappropriate for a simplestandard. This is a crude deterministic approach to a probabilistic load case and should betreated with caution.

Notwithstanding this, to give a feel only for the effective decelerating force (applied at thecentre of gravity) implied by 0,8g (10m boat) or 1.1g (20m boat), assuming a constant impulseapproach, a boat travelling at the hull speed would stop in about 0.5 second (translation only).The load applied at the keel would cause a bow down attitude of (very roughly) 0.5m at thebow. This all seems to constitute a pretty severe load case. Please note again – very roughfigures.

It emerged from the validation that some boats, particularly those with no girders had littlehope of complying with this load case, without substantial local reinforcement.

It is important to recognise differences between the risk/consequences of impact loads onocean racing boats with those of typical recreational craft. Hence, it was felt sensible to havea dual grounding load case approach; NORMAL and ENHANCED. Designers/builders could optfor either.

A category A or B yacht need not necessarily be designed to impact Type II. It is for thedesigner or builder to decide. Type II may be applicable to ocean-going racing yachts incollision with floating objects, ice flows or marine creatures. For other category A or B craft(while designed to the appropriate requirements in all other respects) such a load case may notbe appropriate. Whatever type is selected, the following note shall be included in the owner’smanual to the effect: ‘This boat has been designed to a Impact Type [I] [II] (delete as necessary)grounding scenario as defined in ISO-12215-9, where the craft is expected to be operating at[low] [high] speed prior to the impact (delete as necessary). While compliance does notguarantee that the boat will suffer no damage in such a grounding, the resistance of a boatdesigned to Type II is normally expected to be substantially greater than that designed toType I’.

The ‘NORMAL’ grounding deceleration is subject to discussion and the validation study has beeninformative in that respect. The current formulation is:

F4-NORMAL = 0,3 g mLDC N (as of beginning March 2009)

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Note: another version F4-NORMAL = 0,4 g mLDC (LWL/10)1/2 has been recently proposed 10-March2009, meaning the normal load case 4 value is 50% of the enhanced value.

Results are presented for the first formulation. For the alternative simply multiply LC4/IIcompliance factors by two to obtain CF’s for this version.

Again no speed can be associated with this factor, but using the same grossly simplified logic asabove, the speed is of the order of 3-4 knots. This is considered to be typical of operatingspeeds in shallow waters, where skippers, aware of the danger of grounding, proceed withcaution. Grounding at this speed might lead to very minor injuries but should not it mightreasonably be argued result in any hull damage. This then seems a reasonable minimumstandard which the boating public might expect all boats to be designed to.

Of course there will always be cases where groundings result in damage and no doubt ISO-12215-9 will be cited by various parties. This is perhaps why an explicit speed-load relationshipwould be dangerous as well as scientifically invalid. This is not a reason for avoiding building inof some measure of collision resistance.

3.5 Other issues

3.5.1 Centre of rotation under load case 4 (refer to draft standard, annex B for details)

This discussion is relevant to load case 4 only. The draft uses a centre of rotation (CoR) basedon the relative stiffness of the floors, ignoring the girders and the thorny issue of how to treatthe ‘rigid’ keel root/flange.

The method works well when CoR is located reasonably centrally with respect to the floorpositions. It even works well when the configuration includes a ‘grounding floor’ located nearthe trailing edge of the keel. However it does have a problem if the after floors are fairlysimilar but the most forward floor incorporates the stiff mast step. This rigid forward member‘attracts’ the CoR meaning that few bolts are forward of the rotation point (bolts are assumedto be effective in tension only). It would seem logical that the keel ‘kick-up’ is taken bybearing on the shell aft of the CoR and the load is apportioned accordingly. Nevertheless thisapproach can lead to very low compliance factors on the forward (few) bolts.

Ideally the standard should not drive design, but the provision of a stiff after (grounding) floordoes seem intuitively correct. If this feature is employed then whether the mast step is thereor not, the CoR is located near the bolt group longitudinal centroid (or aft which is even moreadvantageous) and there then do not appear to be any problems with keel bolts in the forwardzone failing to comply.

3.5.2 Effective plating

There are three general approaches to the effective breadth of attached sandwich plating:

1. ABS guides – ‘t’ based, using equivalent EI (i.e. strictly an effective width, postbuckling phenomenon).

2. LR/ISO-12215-5 – ‘t’ based, using 20 (to + t i) (i.e. strictly an effective width, postbuckling phenomenon).

3. DNV HSLCNSC rules – beff based on flange elastic and shear moduli, distance betweenpoint of zero bending moment AND only the inner skin is considered to be effective(shear lag based phenomenon)

Using author’s best interpretation of the published rules, for a typical floor configuration (550 x1500) for which LR/ISO would yield 517mm width, ABS would yield 480mm and DNV 78 or

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183mm (fixed or simply supported). For the same configuration but with 2400 gsm outer, 1680inner and 30mm core, LR/ISO would yield 250mm, the DNV figure would be unchanged BUTwould only consider the inner skin and ABS would yield 597mm (although capped by the floorspacing for this example).

Reality is probably covered (one hopes) by this massive spread. Nevertheless it does seemrather odd that designers should be spending design time deciding on suitable stiffener pads(typically 3 or 4 plies of CU300 300mm wide) to lower the neutral axis, when the effectiveplating is still so crudely defined.

There are two issues here; firstly to flag up for the benefit of companies using the ABSapproach sandwich panel effective breadth, that a notified body proceeding under ISO-12215might have a major problem accepting such grid properties. Secondly, given that the aboverule formulations are still current, isn’t it about time that this issue was resolved given that afew finite element analyses should allow a common formulation to be devised, if indeed thishas not been already been done?

4. CONCLUSIONS

The validation study shows reasonable support for the current level of design loads andcriteria employed in ISO/DIS-12215-9, although it may be more correct to say that thevalidation has not throw up any issues which require a fundamental rethink. Somecomponents appear to easily comply with the requirements of the draft standardwhereas others struggle. This is not a surprise as in some cases, floors depths forexample will be stiffness driven (not within scope of draft) or determined by cabin soleposition. Grillage analysis may resolve many of these.

The majority of components examined comply with the requirements of the draftstandard even using the Annex methods which are considered to be conservative

Non-compliances are not considered to be excessive unless the enhanced groundingcase is selected, especially if no longitudinal girder is fitted (boat E). Changingboundary conditions may produce significant different results at floor ends and if somelocal reinforcement IS required, this is not considered to be a disaster for the builder.

Given the problems encountered in obtaining reliable data, further validation studiesshould involve direct access to engineering drawings. Given the commercial sensitivityof such information, this is considered unlikely to happen and so further validationshould be carried out by notified bodies as part of their normal structural assessmentwork. This information must remain confidential to the notified body but withnumerous NB staff working on WG18, general trends will be informative.

The problem of engaging industry encountered during the validation of part 5continues, often for perfectly reasonable and well understood reasons. It isencouraging that despite the initial cries of despair, part 5 seems to be increasinglyused with few problems, apart from a couple of known issues. It may well be that part9 will follow the same path. In one respect their paths will be identical; ISO-12215 willnot feature on industry’s radar UNTIL it is at least at the FDIS stage (maybe not untilharmonisation). In one respect, this validation has been invaluable in raisingawareness, such that WG18 is likely to receive some further feedback between June2009 (hopefully FDIS launch) and say November 2009 when all the ‘typo’s/tweaks’ haveto be done. In this respect the adoption of part 9 as ‘an approved (but not exclusive)method’ by ISAF would do much to facilitate this.

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APPENDIX I

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