40 Arden Close, Bradley Stoke, BRISTOL BS32 8AX, U.K.

phone/fax: +44 (0) 117 969 8772       e mail:





Notice to all International 505 Class Measurers






Since 2000 505’s built by Van Munster Shipwright and Boat Building in Australia have incorporated a low level moulding that connects the rear of the plate case to the side tanks.  A query was raised with the International Office by a measurer in the USA who considered that the moulding breached Rule 5.6.3 as it exceeds 150mm in width.  Previously Measurers in Australia took the view that this was not a thwart and therefore 5.6.3 did not apply.


The IEC and the International Measurer have considered the matter after inspecting one of the boats in question.    It has been concluded that the moulding IS a thwart and therefore it breaches the rule.  None of the items referred to in 5.6.3 is defined in the ISAF Equipment Rules of Sailing.  We therefore had to consider what these terms meant within the overall context of the 505 Class rules.   A wide variety of different cross members have previously been accepted as meeting the requirement for the compulsory “thwart” under 5.6.2.  These have included angled alloy bars and low timber cross beams, neither of which could be described as a thwart in the conventional sense.  On the basis of these precedents it was concluded that the Van Munster structure would probably be acceptable as the compulsory thwart, apart from the width.   It would then be inconsistent to say that it was not a thwart for the purpose of 5.6.3. 


However, the IEC appreciates the impracticality of rectifying the boats that have been built already, or that are in production.  In view of the fact that the over-width thwart is very unlikely to have a discernable effect on performance, a dispensation has been granted for all Van Munster boats built and registered before 31 December 2002.  If measuring one of these boats, please record this as a deviation on the form, but advise the owner that this will not prevent the boat being registered and a certificate issued.


Furthermore, the IEC concluded that the existing rule does need revision as clearly it is ambiguous.  It believes that the main purpose of the rule is to maintain the open nature of the boat and to prohibit double bottoms or bridge decks.  Since most builders in the history of the class have tried to keep the cockpit area as clear as possible to permit ease of crewing, there seems to be little need to place a maximum limit on the width of any cross-boat structures.   Demand from sailors for a clear working area is the most effective control.


Accordingly a revision to Rule 5.6 is to be put to the AGM at the Fremantle Worlds in December.  This would have the effect of legalising the current Van Munster design, but clearly banning double bottoms or additional buoyancy chambers.  If approved at the AGM it will then have to be approved in a postal ballot of the whole class.    The wording of the proposed rule change is being finalised and will be circulated to National Associations within the next week or so.






C G Thorne


International 505 Class Yacht Racing Association


28 October 2002








Extract from 505 Class Rules






5.6.3       Additional thwarts, bridge-decks and sheet horses may be fitted across the hull. The total width of all such additional thwarts etc. shall not exceed 150mm.




5.7       Not in use


5.8       Weight

5.8.1              Boats shall be weighed in dry conditions for measurement and certification after an uninterrupted period of two weeks not having touched water.


5.8.2              The sailing weight in dry condition shall not be less than 127.4kg. The sailing weight is the weight of the hull including metal corrector weights, the spars, standing and running rigging, centreboard, rudder and tiller, but excluding the sails and battens. Fittings and components of exaggerated weight and artificially heavy areas construction are not permitted: examples include use of lead or other heavy metals, except for corrector weights permitted under Rule B-5.8.3.


5.8.3              If the sailing weight is less than 127.4kg, the difference, without limit, shall be made up by metal corrector weights fixed against the centreboard case or spine and visible when viewed from a standing position next to the boat, half between 1100mm and 1500mm and half between 2900mm and 3500mm from Station 11, such ballast to be retained for the life of the boat or until the boat is reweighed in accordance with Rule B - 5.8.5.


5.8.4              Each metal corrector weight shall be hard stamped in a visible place with its weight in kilograms to the nearest 0.1 kilograms and a serial number to identify the piece of ballast and the total number of pieces used in the boat