Just familiarising myself with the 10R rating formula before building my boat. Seems not so complicated after all, until I looked at the web site for the two versions.

The IRSA 10R web site states a length of 1.3 to 1.8M and a sail area 0.9 - 1.1 sq M.  This seriously alters my concept of the boat since I am aiming outside both these parameters. I can find no reference to an over all length or sail area restriction in the 10R Class rules on the MYA pages here, and the rating formula make the class quite an exciting concept. 

Are these two different classes ? There seems little actual information about the boat on either web site. One is for the IRSA and the other GBR is WS IRSA.

Do I need to join the WS,  IRSA and / or MYA to race a 10R ?

Sorry if this seems a silly question.

Richard

Richard,

 The best place to start is with the Class Rules. (IRSA website/classes/10R/ Technical & Measurement)    

The key thing to note is that the permitted sail area relates to the waterline length. Both as established and measured in accordance with the class rules.  note: trim can affect waterline length and consequent permitted sail area.  Overall length is not a controlling  measurement, except for the ability to get it in your car and transport it!   The figures you quote are typical examples of ranges for modern boats.  There are also some specific rules and limitations in the Class Rules i.e maximum mast height, number of spars. (Dimensions of additional spars have to be measured and included in the sail area.)

To race a 10R it needs to be measured by an official measurer, certified and Registered.  To do this in the UK you need to be a MYA member.

 

 

Thanks Solent.

I have familiarised myself with the class rules and it is the 10R formula that I particularly like, to produce an interesting boat. It is mainly the confusing information or none at all; that exists on the various class sites; particularly the one that limits the overall length. I am aiming for a WL of 1150 and have good ideas on the allowable rig that that will enable. I note your advice that overall length Is not a controlling measurement though and I am going for the GBR 10R class rule from the MYA class info here.

I have the bits and pieces now and am starting the build.  Will put some pics up as I go, if anyone is interested.

Richard

 

 

Richard I am confused.  There is no overall length restriction in the 10R Class.  The MYA website https://www.mya-uk.org.uk/kbtopic/classes/ten rater class states this as follows:-

A Ten Rater is not limited in length and has overhangs beyond its waterline endings making them light, sleek, and fast. This IRSA rule is based on the 1887 ‘length and sail area rule’ which allows short waterline length boats to have a big sail area and longer LWL boats have smaller sails. It is an ‘open’ rule with great freedom to develop design and construction, particularly in rigs and sail plans.

There is and can only be one 10R Class.  There is not a 'GBR Class rule' only the class rules as currently published on the IRSA website.  The dimensions you see in the table on the website are not definitive but example dimensions found on current modern boats.

Thanks Solent. Like you I was also confused. As you say; the length for the boat stated on the IRSA may be assumed to be an average for the class. Not certainly though.  This was my worry when I started my build.  definitely outside those tolerances or average dimensions. Still not 100% certain though since the IRSA site seems quite specific on the length between 1.3 - 1.8M and also a clear definition on sail area too. 0.9 - 1.1 sq M. I have also noticed another web site: ITCA which reflects more what I thought the class was. There is so little information on the class on the web sites and no forum discussion on the MYA site at all.

I have read and digested the class rules and understand the rating formula; which I like. Just ploughing through the WS, IRSA, MYA and now ITCA to glean info seems a bit protracted.

Anyway, looking forward to an exciting boat to sail.