Looking at notices of race for some port phillip and coastal stuff.
Looks like entries are under either AMS or ORC.
If you buy a boat that's older than AMS or ORC do you have to pay to get it measured - and if so is this why there aren't many older boats entering these races - i.e. is having a measurement a potential selection criteria for a boat?
I've been out for a few years, but this is how it works (or used to!)
AMS, IRC & ORC are all measurement based rating systems. That is, they are not handicaps - Doesn't matter how good / bad you sail, that is your rating.
IRC is the most commonly used in most of the world for major sailing events (incl. Oz).
AMS is a "poor man's" version of IRC used in some areas of Australia. Measurement & annual costs are less than for IRC.
ORC is bigger in the US. It evolved out of the old 90's IMS (which may have evolved out of the 70/80's IOR rule...?) ORC involves much more detailed measurement of the boat, including inclination test.
They are all valid & good rating systems. I have noticed that a boat sailed well & "winning" under one system, shall typically do well under a different system. We run IRC & AMS side by side in Div 1, and the top 3 - 4 results are very similar. I've noticed the same for IRC & ORC.
Trust this helps... 
So if I buy a half-tonner I will presumably need to get it AMS or ORC measured / certified in order to compete? Is this just administrative or is it possible that a half-tonner can't measure in one of those systems (too short etc?)
Select to expand quoteJonE said..
So if I buy a half-tonner I will presumably need to get it AMS or ORC measured / certified in order to compete? Is this just administrative or is it possible that a half-tonner can't measure in one of those systems (too short etc?)
All clubs have a PHS (performance handicap system) which any boat can race under. it is an arbitary system based on yacht's past performance and subject to change (which is a source of much debate).IRC, ORC and AMS are defined rating systems where the handicap is fixed based on yacht's parameters.
Hi Jon, I guess everyone's been kind of dancing around the original question so I'll give it a go.
I have no idea about AMS, so I'll leave that to others.
I'm guessing as you have an IOR half tonner it won't be a one design class, so we can dismiss that option.
For IRC you will need a full hull shape measurement including weighing as a stripped boat (empty tanks, no sails, dry inside, nothing movable onboard).
There are 2 different ORC's. Both can race together, but ORCi boat for boat will have a better handicap, as more data points are measured and better data is generated.
ORCi (for ORC International) will also require a full hull measurement and weighing.
ORCc (for ORC club) is more up your alley as it uses generic data for many of the data points. It's a lot less measurement needed. First is to use the knowledge base here on Seabreeze to locate another half tonner with a similar hull shape that has an ORC certificate. You can use this hull file on your certificate. I think you still need to be weighed and maybe the overhangs & freeboards measured, as well as the other normal simple measures. Sails will also need measuring but you don't have to go through the REALLY hard measurements like inclining etc.
ORCc is not overly onerous, but obviously it's more work than just getting a PHS handicap issued by the club. A lot will depend on how much you want to get into it.
and that's my 2c worth... 
Brilliant Jethrow thank you.
Actually this puts the pieces together because one of the boats i'm looking at online has put their IRC certificate on the ad (since I posted).
Each certificate will give you important information about the boat such as an indication of stability for IRC and AVs for ORC i
Send through the Ct if you like
