Safety cover

back in the day we had no safety cover, alot more boats racing, why can't we just organise a flash race on a weekend if the weather is nice and facebook/internet have got a few like-minded people down for a blast. We need to inform the sailing committee and the rescue officer and by the time the general committee get involved it is binned!
 The SI's stated that every club boat must carry a paddle and anchor and flares even with 4 & 5000 sailing the committee boat could be 15mins away from rescue Self sufficiency was key.

In view of the sheer varietsy of circumstances that can arise, the RYA seems reluctant to set any definite ratios of safety boats to competitors. 

Thus the RYA Race Management Guide at http://www.rya.org.uk/SiteCollectionDocuments/Racing/RacingInformation/RaceOfficials/Resource%20Centre/Best%20Practice%20Guidelines%20Policies/Race%20Management%20Guide.pdf

states:

Patrol Boats

The number of patrol boats at an event depends on the competition level, age, ability and number of 

competitors, anticipated conditions, etc. There is no recommended ratio as there are too many 

variables to consider - so it's a matter of common sense and judgement. The patrol boats should be 

of a design and size appropriate to the task -RIBs are commonly used

If they were prescriptive, of course, there would be a danger that a club might be blamed for not following the fixed guidelines even when they weren't appropriate to their situation.

A boat should be available on standby with people ready to helm if needed. There is a ratio that if you are an rya club you need to adhere to.

For the formal answer, the RYA is where you want to go.