SCHRS 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 3%. There is no penalty for winglets on rudders.
Full foiling: Following the 2013 America's cup there is rapid development of full foiling in the small catamaran community, with the hulls being lifted clear of the water for significant periods. The position is being monitored closely, but to date SCHRS has little hard data on the performance improvement. For the 2014 season boats designed for full foiling will have their main boards measured round all curves and in addition the "lift generating foil" penalty will be increased to 7%. The resulting ratings are provisional ratings, and race organisers may choose to rate foilers apart.
Q 2, Why have you taken the calc to 3DP.
Rounding of the rating system numbers to 2 decimal places produces too coarse a system. Consider an hour long race (3600 seconds)
The corrected time for a boat racing off 0.995 is 3618 seconds. The corrected time for a boat racing off 1.004 is 3586 seconds. This gives a difference of 32 seconds, but under the previous system they would both receive the same corrected time of 3600 seconds.
There has been a recent trend of existing established classes being modified to take advantage of the "slack" in their rating. Changing to 3DP will prevent that in the future.
Q 3, 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 4, 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 5, Why have wind factors NOT been introduced.
The RM 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 6, Why has the F18 been chosen as the scratch boat (or fulcrum).
We needed a fixed point - ie a boat that did not move when the new Power Factor was applied. The F18 is the most widely sailed modern boat world wide. It is also not right at one end of the speed range, as would have been the case if the Tornado were to be used.
Q 7, Why has the 800mm control limit on overhang of the Spi pole been removed?
The rule was arbitrary and served no real purpose. Thus it was removed. The SCHRS rule is not in place to limit the design thinking of boat designers, it is here to handicap boats that are sailed. In fact, some existing designs (eg Tornado, F16) have pole projections in excess of 800mm. It is felt that class rules should control this, if they wish to (as done in F18 for example).
Q 8, How are you addressing the issue of policing of the rating system, to make sure people sail boats that match their rating?
We have amended the text to put the onus on the sailor to ensure their boat conforms to the rating certificate. It remains necessary for the cat sailing community and event organisers to self-police proper use of the ratings, as it has done in the past.
Q 9, 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 10, 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 11, Why are two values given for "A-Class", based on two specific designs?
The Class rules for A-Class are very open and every boat should have it's own SCHRS rating and certificate. These values, for a current design at 2006 and another common older design, are published for guidance to show the range of ratings.
Q 12, 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 13, 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 14, 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 15, 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 ratings page for further explanation.
Q 16, My boat had a rating in the old system, but the table now says "Incomplete data".
This is because the calculation now needs to know the beam of the boat and the number of crew trapezing. Please provide this data to us (with some evidence of where it came from, i.e. Class rules or manufacturer's data) and we will update the table.
Q 17, 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 Datas. For formal ratings, Annotated class rules showing where each data point is defined or an ISAF measurement certificate must be provided. Failure to do so will result in the email being returned requesting that you supply the data points.