A new Model

After squeezing as much information as possible out of relatively limited reliable race data for twin keel yachts, an upgraded model for the Portsmouth Number equivalents of such boats has been obtained. As always, results will be monitored and any further information fed into future model development.  Details are shown in the revised Article 2.5.

Article Update

An updated version of Article 1.3 has been posted.  This is to reflect movements in various rating systems internationally and to further emphasise the role of LinStat models in setting club level handicaps in a quick, transparent and relatively straightforward way.

LinStat Register

A draft first edition of the LinStat Register for Portsmouth equivalent handicaps can now be found under Article 4.2.  The list, currently of 400 boats, will be updated in the near future and further expanded at intervals.  As said many times already, a list will never serve all requirements, but may be a useful facility alongside the handicap formulae.  I am happy to receive any questions arising from the list, or requests to include particular boats. The input data have been checked as much as possible, but data sources are not always consistent.  Guidance notes are given in Article 4.1.  In due course, there will be an update on work to refine the handicapping of bilge keel boats.

A Register of Handicap Numbers

The LinStat models developed to date for Portsmouth Number equivalents and corresponding time correction factors have proved to work well. I am conscious though that many involved, willingly or unwillingly, in setting handicap numbers would still appreciate some sort of list to refer to. Gaps or uncertainty in user supplied boat data is often an issue. So, a project is underway to produce a database of sailing cruisers, identified by a range of key data, along with predicted PNs from a number of equally well performing LinStat models. The list will be confined to single keel boats initially and the aim is to have a first edition published on this website in time for the (hoped-for) 2021 sailing season. It has to be remembered, though, that no such list will ever contain every possible boat, which is one of the reasons for all the work in producing straightforward statistical formulae for handicap numbers.

A Model Variation

In response to the desire of some users to include overall length as well as waterline length in their calculations, I have looked at producing an acceptable alternative to Model 10A.  There are inevitably pros and cons in doing this, but one possible option is discussed in the new Article 2.5A

A note of caution

No single handicap formula will 100% capture all boats in all conditions, so inevitably ways to tweak formulae will be sought. There are several approaches to this, but care must be taken not to damage the statistical integrity of the formula.  For example, it is inappropriate to replace LWL (waterline length) with some other definition of length without a re-assessment of the model coefficients.  I will shortly publish an article on model variation, with particular reference to Model 10A (see Article 2.5).  

 

Update

There is a continuing problem with getting sufficient reliable performance data for bilge keel yachts on which to base refinements of my Portsmouth Number equivalent formula for these craft.  So, I have decided to look at the problem from a different angle. Given that the formulae for fin keel boats continue to work well, my current quest is to look at designing an appropriate adjustment that will enable the same formula, in essence, to be used for all keel types.  A significant advantage of this approach is the possibility of extending it to the TCF models described in Articles 2.6 and 2.9.  I will report on progress in due course.

Correction

My thanks to the eagle-eyed reader who spotted a typographical error in Article 2.11. The suggested high-tech sail adjustment should of course be negative not positive for a PN type handicap. The correction has been made.

Adjusting Handicaps

A new article has been added here, 2.11, on the subject of handicap adjustments. This covers some of the reasons and approaches to varying handicap numbers.  Of course all systems need some review on a regular basis, but whatever the system to arrive at a ‘base’ number, there will be additional factors, not necessarily already accounted for, that might need some minor allowance.

Aspects of handicap setting

As another sailing season draws to a close, it is time for more reflection on the performance of the LinStat models.  As explained in a new article, the suite of models, though looking different from each other, all give similar results. Further, they can be applied equally well to different handicap systems.
A real practical issue is the accuracy of input data, as referenced in Article 2.9.  More detailed illustration is given in the new article, 2.10.  A further article will discuss a number of factors that those producing handicap listings need to think about in the context of handicap adjustments/allowances.