FAQs

Our most frequently asked questions

Q 1, How does SCHRS rate foilers?

Skimming: Small catamarans are increasingly using lift generating foils to enhance performance. Curved daggerboards on classes such as the Nacra 17 are used to make the boats skim over the surface in certain wave and weather conditions. These are penalised under SCHRS in two ways - first the daggerboards are measured around the curve which is a longer measurement resulting in a bigger penalty. And secondly we have introduced a "lift generating foil" penalty of 1.5%. There is a further penalty for winglets on rudders of 0.5%.

Full foiling: Boats with foils designed to lift the hulls clear of the water have a penalty of 4%.

Q 2, Why have you removed the WL from the rule.

The measurement of the waterline length is a time consuming and difficult process for the measurer. It involves floating the boat with sails and measuring the wetted length. This is deemed to be an unnecessary complication when most new designs have vertical or reverse rake on them and thus in general the waterline length or effective sailing length will be equal to the overall length. The proposal allows for the grandfathering of existing boats in the system as many of the older designs do have raked bows, but removes the necessity to measure the waterline length of new boats.

Q 3, How has beam of the boat and righting moment of trapezing crew been introduced?

This has been applied as a "Power Factor", applied in a similar way to the existing "Board Correction". The power factor is derived from the relationship between the righting moment and heeling moment of the boat. The Heeling moment takes into account the white sail heeling moment, the spinnaker heeling moment and the relative "importance" of the spinnaker heeling moment in cat racing. The Righting moment takes into account the number of crew trapezing, the beam of the boat and the presence of non-trapezing crew assumed to act at the boat's beam (ie hiking).

Q 4, Why have wind factors NOT been introduced.

The Righting Moment component of the rule caters for this by factoring the "power" of the boat, and so the performance across wind ranges. To introduce wind factors would add a lot of complication and require additional subjective input from race officers, which is not practical.

Q 5, Why has the F18 been chosen as the scratch boat (or fulcrum)

Each year we adjust the formula to ensure that the F18's rating is 1.000. We need to normalise the ratings from year to year because they are sometimes linked in to other systems such as PY. The F18 has been chosen because it is in the middle of the speed range and is raced in significant numbers in most parts of the world.

Q 6, How are you addressing the issue of policing the rating system, to make sure people sail boats that match their rating

Wherever possible SCHRS refers back to class rules, thus delegating some of the enforcement back to classes themselves. This is particularly valuable for the weight measurement which is difficult for SCHRS measurers to check at events.

Q 7, How about when an existing class of boat has rule changes? (Like changing to carbon masts on the Tornado?).

We have amended the wording to make sure that such a class is re-measured (or at least the changed parameter is updated and a new rating generated).

Q 9, What about ratings for "Formula" classes, they need to keep up with the latest developments.

We have added the requirement that for Formula classes (and A-Class), the rating is to reflect the limiting values given in the class rules. Where a measurement is needed for SCHRS but is not controlled by class rules, items will still need to be measured, (eg daggerboards).

Q 10, Why are two values given for the "A" Class?

We have tried to reflect the reality of the A class fleet where some boats have full foiling kit, and some older ones (A class classic) don't. Although both comply with their class rules we feel it would be unfair to apply a full foiling penalty to the older boats which don't have that capability.

Q 11, Can I keep using my old rating after 1st March 2007.

No, as the new ratings are calculated using a different formulation. From 1st March 2007 you must use the new rating which is calculated to 3 decimal places.

Q 12, What has been done to address the high performance single handed boats: a common view is that they "run out of hands" sooner than the 2 up boats and so are at a disadvantage when it's windy.

These boats are also lacking Righting moment compared to their Heeling moment. The Power Factor correction has addressed this. It is difficult in a rating system like this, to address the boat handling issues.

Q 13, Why are the new SCHRS values still not in line (proportionally) with the RYA PYs for some boats?

There are only a small number of cats which have RYA Primary PYs generated from sufficient returns, as not much cat racing has been done using the PY system recently. RYA PYs are, based upon returns whilst the SCHRS is a measurement formula. There will be always be differences.

Q 14, How can cats race against monohulls if they don't have an RYA PY?

If the cat doesn't have a published PY, we suggest scaling the SCHRS rating to obtain a "PY Look-alike". Please refer to the PY Look Alike page for further information.

Q 15, My boat does not have a published rating, what should I do ?

We can calculate an indication of the rating for you by entering the rating point values into the calculation formula. Ratings can only be confirmed by formal reference to class rules, and/or formal measurement. If you require us to calculate a rating you must provide the data points described here in section C.2 Data. For formal ratings, Annotated class rules showing where each data point is defined or an World Sailing measurement certificate must be provided. Failure to do so will result in the email being returned requesting that you supply the data points.