YA safety inspection sheets require statement re Stability Factor or IRC SSS numeral or RMI - I recall reading on the forum a pull down on the mast of a RL28 at 68 kg yet when you look at YA references there is a complicated formula which has me lost. if someone could post the required data it would be helpful
Ken. The TM in fact is the pull down figure. ie, 68 for that particular boat, and can be used in the final formular which appears difficult, but not so bad if you take it step by step. It is a great pity that YA do make it so difficult, but it is for your own saftey.
What is the safety category of the racing you are competing in? I think it was this year that YA required all trailer yachts racers to comply with the easy to understand Horizontal Stability Factor (HSF). The HSF is a pull down test based on a simple formulae that gives you a hold down or TM figure in kgs. All you need is the boats Length Overall, Max Beam, Sheer to Hounds Length and Mast Length above the step. The simpler HSF is allowed for all boats racing in Category 6 and 5 races which should cover 99% of all TY races so I cannot see why you would want to use the more difficult Righting Moment Index (RMI).
If you go into the YA website and click on racing and then on special regulations all is explained, it also shows a rushed amendment to cover a YA booboo in the new HSF formulae!! The YA do not appear to be giving any boats an allowance for floatation or age and I have received conflicting information from other sources so now I just follow whats recorded in the RRS rule book. I feel that many TY class associations and the boating magazines are failing their members and readers by not taking a more active approach by either putting the boot into the YA or clearing up this confusion.
IRC SSS Numeral can be is a very expensive test and is really meant for deep sea racers and ships and involves in some cases an inclination trial (not a pull down test) to find the floating vesselís Centre of Gravity in relation to its Centre of Buoyancy.