Spinnakers and Poles/Bowsprits explained..

The RORC Rating Office is sometimes asked whether symmetric and asymmetric spinnakers are rated differently, and whether there is a rating increase if you use both types. The question is often prompted by the IRC application form asking questions about the spinnakers of each type carried aboard, rather than just the largest spinnaker area (SPA) and total number of spinnakers. There are two aspects of downwind sail rating: the sail itself and the type of pole (if any) it is set on - as explained below. Text in italics is taken from the IRC 2018 Rule text.

SPINNAKERS

For the calculation of your rating, IRC considers the largest spinnaker area (SPA) and the total number of spinnakers carried.
21.6 Spinnakers
21.6.1 Boats carrying more than three spinnakers in total on board while racing will incur an increase in rating.

21.6.2 Spinnaker area (SPA) shall be calculated from:
SPA = ((SLU + SLE)/2) * ((SFL + (4 * SHW))/5) * 0.83
SLU, SLE, SFL and SHW of the largest area spinnaker on board shall be declared. The calculated area of this spinnaker will be shown on a boat’s certificate as the maximum permitted SPA.

8.10.1 Values stated on certificates for LH, Hull Beam, Bulb Weight, Draft, x, P, E, J, FL, MUW, MTW, MHW, HLUmax, HSA, PY, EY, LLY, LPY, Cutter Rig HLUmax, SPA, STL are maximum values.

Are symmetric or asymmetric spinnakers rated differently?

Not directly, but see the section on pole type below.

Is there a rating increase if I carry both symmetric and asymmetric spinnakers?

Not directly, but see the section on pole type below.

If not, why does the application form ask how many of each type of spinnaker I carry, and which is the largest?

The information is useful for picking up errors or oversights on the application form before the certificate is issued. For instance if an application form says that the boat carries symmetric spinnakers we would expect the boat to have a spinnaker pole for the symmetric spinnaker.

On revalidation or amendment forms, we ask whether the symmetric or asymmetric spinnaker is the largest because sometimes we will be given data for a new asymmetric spinnaker, for instance, but then find out that the symmetric spinnaker on the last certificate is still the largest.

Requesting this information often means that an owner avoids having to amend their certificate to correct errors.

If the linear measurement data for spinnakers (SLU,SLE,SFL,SHW) are not maximum limiting values, but only largest spinnaker area (SPA), why do you ask for this information?

Rule 21.6.1 states that the linear data shall be supplied for the largest spinnaker, and IRC application forms ask for the linear data for the largest of each type of spinnaker. As above, this is to help the Rating Authority identify possible issues before the certificate is issued.

For instance, we can check that an asymmetric spinnaker complies with the spinnaker definition ie. SHW => 75% SFL. In many cases where this test fails, it is because the SHW measurement has been taken incorrectly and supplied as 50% of actual SHW. Having the linear data also helps us identify typographical input errors, for instance if we get a warning showing a spinnaker is very large or very small we can check the spinnaker data compared with the rig data.

POLE TYPE

The spinnaker type does not affect the rating, but what does make a difference is the way the spinnaker is flown and hence the type of pole you use, if any, and the rated STL (see definition below).

21.3.5 Boats will be rated according to whether they use a spinnaker pole and/or a bowsprit according to the following configurations:

(a)  No spinnaker pole (spinnaker tacked on deck) or a centre line bowsprit only.
(b)  An articulating bowsprit only.
(c)  A spinnaker pole or poles either with or without a bowsprit.

STL The greatest horizontal distance from the forward face of the mast spar, measured on or near the centreline of the boat, to any of the following:

- the extremity of the spinnaker pole, whisker pole or bowsprit;
- the spinnaker tack point on deck projected vertically as necessary;
- if a headsail may be tacked forward of the forestay, the headsail tack point on deck projected vertically as necessary or to the extremity of the bowsprit.

Effect on rating of different pole types

It is impossible to estimate the rating effect on pole types for all boats, as this depends on many variables. The only way to get an exact rating for a potential change of configuration is to apply for a trial certificate for your boat (available to boats holding current IRC certificates).

However, the following are examples of different popular configurations, assuming the same spinnaker SPA, with TCC A being the lowest and TCC E the highest:

Information correct November 2017, and may be subject to change in the future. 

Bulb Weight - Clarification

IRC Bulb Weight refers to the Bulb as defined by the ISAF Equipment Rules of Sailing. This document is provided as clarification that all under-fin spacers and infills shall be included in the total Bulb Weight.

The ERS defines Bulb as
E.1.2(e) A hull appendage containing ballast at the bottom of another hull appendage primarily used to affect stability.

Ballast is defined as
C.6.3(e) Weight installed to influence the stability, flotation or total weight of the boat.

E.1.1 defines Hull Appendage as
Hull Appendage Any item of equipment – including the items listed in E.1.2– which is:
• wholly or partly below the sheerline or its extension when fixed or when fully exposed if retractable,
• attached to the hull shell or another hull appendage, and used to affect: stability, leeway, steerage, directional stability, motion damping, trim, displaced volume.

And clarifies that:
Any of the following shall be included in the hull appendage:
• corrector weights,
• integral ballast, and
• associated fittings.

Therefore, all under-fin spacers and infills shall be included in the total Bulb Weight.

Addition in reply to a specific question:
Q. We have read the latest IRC bulb weight clarification were it clearly states that all under-fin spacers and infills shall be included, but we are not clear about the bolts/nuts/washers. Do you mind clarifying if we should consider these items as part of the weight?

A. As any retaining bolts and attachments, as well as infills and adjustable weights, are only there as part of the bulb and would not be there if it was not for the existence of the bulb, these would be included in the bulb weight.

Changes to 2017 Certificates

Please note the following layout changes to the IRC certificate for 2017 (listed from the top of the certificate):

• New certificate header – these have been updated to reflect our new IRC logo.
• Aft rigging replaces Runners/Checktays in the Detail section
• The validity stamps have been updated and your certificate will show either ‘Standard’ or ‘Rating Authority Endorsed’, see below.

If you have not already done so, please read the 2017 Rules and Definitions which are online at

https://www.ircrating.org/technical-a-certification/rule-a-definitions - changes for 2017 are marked with a sidebar.

Endorsement:  This is denoted by the ‘Rating Authority ENDORSED’ stamp at the bottom right of the certificate.   ‘Non-endorsed’ certificates are now known as Standard as shown on the stamp.  If you need Endorsement for an event you are entering, please contact your local IRC Rule Authority office as soon as possible for advice (details at the end of this document).

Will I get a mast sticker?  NO.  With all IRC certificates now being emailed, after 28 years we have discontinued the IRC mast stickers.  

 Validity dates are shown at the bottom of the certificate. When your certificate expires you will receive an invitation to renew it, please make sure your contact details are kept up to date by emailing us with any changes to your postal or email address.

Please check the data and details on the certificate.   If there is anything you think is incorrect please contact us; however for production designs remember some standard data may have been used which differs from that submitted (usually hull data).

Ratings may go up, down or stay the same from year to year, depending on changes and developments in the maths behind the rating calculation.  This is developed on an annual basis and is generic for certain design characteristics.

Age Allowance is automatically applied to boats over 3 years old, but it is a small part of the calculation. (It cannot be assumed that the rating will reduce each year because of age allowance).

Crew limitations IRC Crew Number is not variable by a boat and has no effect on TCC (see also ‘Fair Play’ in the Yearbook).

CERTIFICATES

Amended or Trial certificates:   We cannot accept data by telephone.   Please make sure you complete the ‘Source of Information’ to avoid any delays, thank you.

Note that there are limits to the number of trial certificates that are allowed, you can find details on the IRC website. http://www.ircrating.org/technical-a-certification/certificates-extra-info.

We reserve the right to refuse to amend a certificate if we believe its purpose is to take advantage of a forecast eg. reducing sail for a race that is forecast to be windy.

If you have an Endorsed certificate, remember that any amendments to rated data will require official measurement, please refer to our website especially regarding sail data and talk to the Rating Office for advice if necessary.

Change of Ownership:  If you sell your boat and the new owner wishes to race it, or if you buy a boat with a current IRC certificate, then Re-Registration is required. 

Short-handed certificates:  If you do short-handed (1 or 2 people) racing, and your boat is in a different configuration for this, you can apply for a separate Short-Handed certificate, see IRC Rule 8.2.1.  

STIX and AVS Stability data :  If you are planning to enter an event that is OSR Cat 3 or over you may need to have STIX & AVS (stability) data on your IRC certificate. Please check the specific events you are entering, to see if it is required. Information about STIX & AVS can be found on the IRC website:  http://www.ircrating.org/technical-a-certification/sssn-a-stix. Once obtained, the information will be added to your certificate free of charge as long as there are no other changes.

IRC Rule changes 2017 – a summary

• The definition of STL has been changed to cater for boats that do not use a spinnaker but fly a large headsail from the end of the bowsprit. All ratings will therefore include an STL measurement even if not rated for spinnakers.

• To simplify the Rule, a new definition Aft Rigging has been added: IRC will no longer distinguish between backstay(s), running backstays or checkstays.

• New rule 19.6 has been added requiring declaration of materials over specific gravity of 8.0 (eg. lead) in some types of keel fin. This is to counter the trend of moving lead from the bulb into the fin.

• Rule 2.6 has been updated to reflect actual practice.

• The new ERS 2017-2020 now incorporate definitions that were previously included in the IRC Rule, so these have been removed or updated as appropriate.

• A number of detail changes have been made throughout the text to correct typographical errors and inconsistencies in terminology. 

What should be aboard my boat for weighing?

If you are having your boat weighed for IRC it needs to be in IRC Measurement Condition.  This is described in IRC Rule 17.1 and 17.2 and also applies to measuring the Overhangs and the Draft.

One way we often describe it is that if you turn the boat upside down and shake it, nothing would fall out (although we don't expect you to actually try this!).