Halfton Class Europe

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Technical matters / Considérations techniques.



Subject: IRC and changes to boats


If you are thinking of making changes to your Half Tonner, please make sure that you check any effect it may have on your IRC rating.

For instance changing keel or rudder, or any changes to the hull, rig or sails.

The best way to check this is to ask for a Trial Certificate through your local IRC Rule Authority, this will show you the rating for a proposed change and may save you a nasty surprise later !

If you are making changes to the hull, keel or rudder then you will need to send drawings of what you propose.

You can find more information about IRC and contact details for Rule Authorities on http://www.ircrating.org

Regarding the post about STL on this page, this may be misleading, and is also now out of date as the Rule about the STL 'base' value has now been removed (because it was confusing!).

There are no minimum or maximum STL limits, you will simply be rated higher for longer STL and lower for shorter STL.

Wishing you all good racing in 2012.

Regards Jenny Howells Technical Manager, RORC

Name: Jenny Howells    Email: jenny@rorcrating.com  Date: 12/04/2012 IRC n°004


Subject: A new rudder for Waverider


As we were no longer  trusting our 35 years old  rudder  which was showing alarming signs of wear and tear, it was decided to go for a new rudder, safe and with good hydrodynamic characteristics.


After considering various and expensive solutions, ea.  molding or copying an existing one or even purchasing a blade from a production boat with similar characteristics,  the best solution came from Denmark where JEFA ( www.jefa.com )  is producing standard rudders for a large variety of boats with various lengths and displacements, cruising or racing.


The blade that proved to fit the best for a Half Tonner was the so-called RUD 31. The only thing JEFA needs to know before to start the production  is the distance top of deck / bottom of hull, in order to deliver a rudder with the exact rudder stock height.


This racing and thin rudder only accepts a stainless steel stock, which results in 22kgs total weight. Corresponding tube and self aligning bearings are of course available.


Price proved to be very competitive, about 2000 Euros, ex VAT … pricelist on their website. This price includes blade, stock,  tube, bearings and tiller head.


The increase of TMF will be 0,003 and I’m confident that the higher  rating will be compensated by a better speed … to be confirmed next season.


Name: Alain Delvaux    Email: dumontdelvaux@hotmail.com   Date: 14/03/2012 IRC n°003


Subject: Head sails


Here in Sweden as well as in Denmark has the IRC rule not yet become spread widely.

It is on its way but I think it will take several years before it outruns the SWE-Lys in Sweden and the Danish Handicap System in Denmark.


Nevertheless can we see a trend that especially in Denmark, boats that were originally designed with overlapping genuas (and I am not talking of IOR-boats only) now skip there genuas and re measure with non overlapping jibs only.


This, giving a lower rating and also according to rumors, true or false, are non overlapping jibs favored in the Danish Handicap System.

Evan if most of you are sailing under the IRC, would it be interesting to here if someone has any thoughts around this question.

Jan “Antheor” Lomma, Sweden 

Name: Jan Carlander    Email: jan.carlander@survey-international.m.se    Date: 27/12/2010 IRC n°002


Subject: Length of the spinnaker pole  /  Longueur du Tangon.


Les bateaux jaugés en IRC utilisent la formule suivante pour le calcul de la longueur

maximale du tangon:

Lmax= 0.456 x √‾SPA     ( SPA étant la surface IRC du spi sur la lettre de jauge )


Il s’agit là d’une longueur maximale au delà de laquelle une surtaxe interviendra.


D’autre part, on tiendra aussi compte de l’encombrement d’un tangon plus grand à l’empannage, de la hauteur de capelage, etc…


Comparez pour exemple les longueurs de tangon de Wave (47,22 m²/ 3,06m) ou Tapioca (58,97 m²/ 3,04m) par rapport à leurs SPA respectifs …


Des tangons carbone, ultra light, à la dimension IRC max de votre spi sont disponibles chez Outsider Sails à Bruxelles, www.outsidersails.be


Longueur jusqu ' à : 3 mtr Ø 38 mm = 350 € /ttc 
  3, 50 mtr Ø 50 mm = 450 € /ttc
  4 mtr Ø 60 mm = 680 € /ttc


Les tangons sont livrés complets avec des embouts en composite de chez FORESPAR à déclenchement automatique, hâle-haut et bas en Dyneema 78.


Les tubes sont composés de fibres unidirectionnelles avec une dernière couche de fibres croisées.


Half Tonners déja équipés de tangons Outsider :  Red Cloud,  Général Tapioca, Blues, Envol, Waverider …



Name: Alain Delvaux    Email: dumontdelvaux@hotmail.com     Date: 28/11/2010 IRC n°001