Boom Rules Anomaly
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After a certain amount of head scratching on my own account and also regarding Wietze’s questions, I had another look at this point and I think there is a bit of a muddle in the Rules regarding Boom Bolt position and black bands.
If, as I did, you transfer a (legal) boom from a Needlespar mast to an Aardvark, The boom black band measurement is found to be about 17mm too long, (if measured from the ‘mast track – extended if necessary’ point), so I changed it.
I measured it under the latest Rules, No 13.2 ie. from the Boom Bolt position, and it’s still too long. So I changed it.
I had a bit of a discussion about it with the measurement guy at Carnac, he understood but, and I quote, ‘Je suis ici Monsieur le President’! – and he was having none of it, bless him!
The latest version of the rules, No 12.3 give a boom bolt position at a Max. 39mm from the ‘aft face of the mast’ – defined as ‘the sailtrack, extended if necessary’. My Aardvark is 37mm. The Needlespars if measured the same way, are 22mm (this is because the boom pin centre is 37mm from the Round Mast Extrusion, not at the (15mm) sailtrack ‘extended’ position.Is this where the problem started………..I wonder.
Anyway, It’s all about as clear as a bucket of mud.
Would it not be simpler to have a boom ‘inner point’ marked on the mast gooseneck, ie. at the ‘mast sailtrack – extended’ point, as per the previous versions, because that point has to be found, anyway, to check the bolt hole position.
Using the Boom Bolt position as a method to measure the boom black band is just not consistent with older rigs and varying bolt positions. The black bands are on spars as a check to see that sails are being set within the measurement rules, and as the mast and boom sail track lines intersect at the tack, nothing else should be required. The Boom Bolt is outside of these limits. One might as well use the kicker lever bolt (have its position closely defined of course (+ or – 2mm)), and measure from there!
I realise that the rules cannot be retrospective, and once measured ok, it’s ‘OK’, but the rules seem to be diverging here, from what was and is done as standard practice. Thoughts anyone……Wasn’t involved when this was changed – do you know the reasons for changing this Terry, and what was proposed for the old goosenecks where the pin was further forward?
Billyou tell him Burt,
The lastest version of the Class Rules (12.3) get round the ‘Needlespar’ problem by giving a MAX dimension (39mm) for the Boom Bolt from the ‘mast sailtrack – extended’ point;- prior to that Needlespars would have been out of Class – (the rule read 37mm + or – 2mm). Needlespars are 22mm ish.
Interesting that the ‘Class Rule 13.2’ measurement, 2640 from Boom Pin, when at the Maximum 39mm, is still 1mm short of the ‘Measurement Form 13.2’ 2680mm (at Max from Mast sailtrack). The Measurement form I’ve seen seems to be lagging behind here, still giving 35mm to 39mm for the Boom Pin distance from sailtrack, so Needlespars are still either OUT or have the disadvantage of a shorter sail foot (or both!).
Bob.
In order to answer this ‘question’ I should first point out the process in which a Rule might be changed.
First off, an idea is suggested to the Technical Committee. They then spend a lot of time discussing this change and getting any wording correct. The Proposal is then sent to the Secretary who publishes it with the next AGM agenda. National Associations then have 8 weeks to discuss the proposal and come up with a decision. At the AGM the Rule is voted on by all member nations present.
The boom Rule was no exception. The Rule was passed at the 2012 AGM with 8 votes for and none against. To be discussing this change at such a late date means that either your National Association did not discuss the proposal with its members or that you did not take part in the discussion at the time. Either way, here is an explanation.
When the new mast Rules came into effect in 2003 a new Rule was introduced specifying the position of the gooseneck hole; that is, its centre should be 37mm +/- 2mm from the aft face of the spar. At the time the majority of mast makers had no idea what was meant by aft face of the spar, and so placed their gooseneck holes at 39mm from the aft face of the mast section itself. When I checked masts at the 2005 worlds the only legal masts were the Danish masts from Pedersen. Slowly the mast builders got it correct but this left a lot of masts still out of class, including all the old alloy masts. I don’t know the history of including this Rule and I don’t know why a new Rule was introduced that made alloy masts out of class.
Move on a few years and the next generation of masts were being built and sailors were turning up to Worlds with 2 masts (one legal and one not). Now, as the boom outer limit is measured from the aft face of the spar, the sailor’s boom would measure with one mast and not the other. This meant that booms were not interchangeable between masts as the holes in the mast were in different places. Obviously a silly situation to be in! Either a boom should measure or it doesn’t.
By 2011 most masts had the gooseneck hole in the correct place and these were becoming the majority. It was suggested that we follow the lead of the Finn class and measure the boom outer limit mark from the hole in the boom. This would mean that a boom is always legal no matter what mast it was put on. It also makes event measuring and manufacturing a lot easier. As a side Rule to this proposal we also changed the 37 +/- 2mm to a 39mm max. This would make all older masts legal. The fact remained however that using an older mast would result in a marginally shorter effective boom length. This was also discussed at length in the Technical Committee. Most booms affected would only have 15mm less length and this was considered a necessary and satisfactory side effect. This was actually reduced to 14mm by picking 2640mm as the outer limit length, although this was actually done to have a round number rather than what would seem to be a strange choice at 2641mm.
Now that we have a standard system and manufacturers are following the correct methods, any anomalies should get less and less. The measurement form is lagging behind the Rule updates but I’m afraid that’s just a consequence of being an amateur class where we all have limited time. It will get updated at some point.
Alistair
Thanks Alistair that’s very clear.
A pity the Rule had to be changed in the first place, but I see the point about being able to make and measure Booms to a ‘standard’, easily.
I guess the idea was to bring the OK’s into line with the Finn and Europe methods.
The Finn rules seem quite similar to the Ok’s, while the Europe, (if I’ve understood it correctly!) is a fixed position for the bolt.Perhaps a ‘grandfather’ clause should have been used for us, with older (pre new rule) boats being measured from the ‘sailtrack extended’ position, but it does make things more complicated during measuring, that’s granted.
Cheers,
Bob
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