@klein - de kelt is volgens mij niet volgens ior gebouwd. Uiteraard kan je gewoon een wedstrijdje met de kelt varen onder Sw of Orc/irc.
Tonners (mini, 1/4 , 1/2 , 3/4 , 1 en 2 ) waren boten gebouwd onder de IOR rating , welke in de jaren negentig is opgevolgd door de chs formule, die werd weer de huidige Irc.
Indicatief:
Mini: ca 6,5 m1
1/4 - lenge ca. 7,5 m1/8 m1
1/2 - ca 9 m1
3/4 - ca 10 m1
1 - ca 11/12 m1
2 - ca 13/13,5 m1
Handicap formules zijn bedacht om verschillende zeilboten tegen elkaar te kunnen laten strijden (een formule is dus bij one dedign klasses niet nodig).
Voorbeeld van uitleg op wikipedia:
“In order that yachts of different types can race against each other, there are handicap rules which are applied to differect boat designs. The Half Ton Class was created by the Offshore Racing Council for boats within the racing band not exceeding 22'-0". The ORC decided that the rule should "....permit the development of seaworthy offshore racing yachts...The Council will endeavour to protect the majority of the existing IOR fleet from rapid obsolescence caused by ....developments which produce increased performance without corresponding changes in ratings..."
When first introduced the IOR rule was perfectly adequate for rating boats in existence at that time. However yacht designers naturally examined the rule to seize upon any advantage they could find, the most noticeable of which has been a reduction in displacement and a return to fractional rigs.
After 1993, when the IOR Mk.III rule reached it termination due to lack of people building new boats, the rule was replaced by the CHS (Channel) Handicap system which in turn developed into the IRC system now used.
The IRC handicap system operates by a secret formula which tries to develop boats which are 'Cruising type' of relatively heavy boats with good internal accommodation. It tends to penalise boats with excessive stability or excessive sail area.”