Remove radius normalisation in station keeping?

[Yu Cao 曹宇]

The rule on station keeping currently normalise the radius of each boat based on its length. I doubt if we should keep doing this in WRSC 2019 as the normalisation seems give too much advantage to longer boats.

Team	Initial Radius	Length	Normalised Radius
Aber	12.59	1.3	9.68
Soton	13.26	1.0	13.26
Difference (Aber-Soton)	5.3%	30%	36.98%

Taking the competition result from last year as an example, in micro-sailboat class, team Aberystwyth (Aber) achieved a normalised radius at 9.68 metres with their 1.3 metres boat. Team Southampton (Soton) has an normalised radius at 13.26 metres with a 1 metre long boat. The total advantage Aber over Soton is (1+5.3%)(1+30%) = 1 + 36.98% which means the length itself contribute more than 30% in the final grade.

Similar example can also be found in between ENSTA and Shanghai.

Team	Initial Radius	Length	Normalised Radius
ENSTA-1	14.30	2.6	9.68
Shanghai-3	14.90	1.5	13.26
Difference (ENSTA-Shanghai)	4.1%	73%	80.54%

Team ENSTA can take advantage of the normalisation by more than 73% precent. Does a 2.6 metres long boat is 73% harder to control than the 1.5 metres one? If not I think the normalisation had given too much advantage to the longer boat, not to mention the smaller boat is actually more difficult to control due to its Froude number.

This issue is first raised at GitHub https://github.com/WRSC/rules/issues/12

[Colin Sauze [cos]]

I don't see any problem with removing this normalisation. I'm not sure i'm even convinced by the whole idea that the smaller boat is more maneuverable, often the small boats struggle to steer against the wind and the tide and will be slower moving. If anything these results show that there isn't any practical difference.

Colin.

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-- 
Dr. Colin Sauze
Research Software Engineer
Super Computing Wales Project
Room 2.16, Physical Sciences Building
Aberystwyth University,
Penglais, Aberystwyth
Ceredigion, UK, SY23 3DB

Tel: +44 (0)1970 622774
Webpage: http://users.aber.ac.uk/cos

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