Lower measurement band

Discuss measuring an IOM and being a measurer

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spaldi01
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Lower measurement band

Post by spaldi01 » 30 Sep 2005, 15:19

On my boat I want to have each rig set up so that the main booms are different heights off the deck. However Rule C7.4 States that the lower measurement band has to be between 60 and 100 from the deck limit mark and within these limits, the variation in height of each rig is + or - 5mm. Does this mean:

a)If one rigs measurement band is 70mm from the deck point I can have another rig where the measurement band is 80mm from the deck point

b)If one rigs measurement band is 70mm from the deck point I can only have the measurement bands on the other two rigs between 65mm and 75mm

c)If one rig fitted with a mast ram that allows the rig height to be adjusted has its measurement band at 70mm it can only be adjusted in height by + or – 5mm and I could have the other rigs with bands anywhere between 60mm and 100mm

Thanks in advance

Chris

Lester
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Re: Lower measurement band

Post by Lester » 30 Sep 2005, 15:49

Hi Chris

My unofficial opinions:
spaldi01 wrote:a)If one rigs measurement band is 70mm from the deck point I can have another rig where the measurement band is 80mm from the deck point
Yes.
b)If one rigs measurement band is 70mm from the deck point I can only have the measurement bands on the other two rigs between 65mm and 75mm
No.
c)If one rig fitted with a mast ram that allows the rig height to be adjusted has its measurement band at 70mm it can only be adjusted in height by + or – 5mm and I could have the other rigs with bands anywhere between 60mm and 100mm
Yes.
Lester Gilbert
http://www.onemetre.net/

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Olivier Cohen
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Post by Olivier Cohen » 30 Sep 2005, 17:33

I think it means that all your rigs must have the limit band within 10 mm (=+/-5mm) and that you can't have a band outside of the limit 60-100mm.

So you can have 60-65-70, 60-70-70, 80-70-70, but not 60-80-70 nor 55-60-65

But if you want an advice, keep it close to 60!

Best regards.

Steve Landeau
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Post by Steve Landeau » 30 Sep 2005, 18:01

My interpretation of this has been that in no instance can any rig be +/- 5 mm from any other rig. If your #1 is 60, and your #3 is 70, that is +10, and is not legal.
Steve Landeau
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awallin
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Post by awallin » 30 Sep 2005, 19:23

(unofficial personal comment)

slightly offtopic, but something for the TC to consider:
having read C.7.4 I fail to find a definition in the 01-04 ERS for lower limit point.

if we want to increasingly use the definitions in the ERS in the future, the rule could read:
lower point height .........................60 mm 100 mm
within these limits, variation in lower point height for each rig +/- 5 mm

this would require that a mast datum point is defined in the class rules... ('point on mast closest to deck limit mark' or similar ?)

Anders

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Post by Lester » 30 Sep 2005, 21:02

Steve Landeau wrote:My interpretation of this has been that in no instance can any rig be +/- 5 mm from any other rig. If your #1 is 60, and your #3 is 70, that is +10, and is not legal.
Hi Steve

Can see how the rule could be read this way. Am confident that the intention (smile) of the rule is merely to restrict your ability to move a given rig up or down too much once it is set, but that you can set a rig anywhere you like between 60 and 100. The rule was introduced because sailors like me would turn up with a spacer length and set the No.1 rig at 100 when the winds were light, then remove the spacer so the rig was at 60 when the wind was at the top of the rig range...
C.7.4 MAST wrote:(a) DIMENSIONS
Within these limits, the variation in height of lower limit point for each rig .......... ± 5 mm
I read the phrase "variation in X for each rig" to say that, taking each rig separately, X cannot vary by more than 5 mm, and do not read it as saying that each rig must be within 5 mm of X of each other.
Lester Gilbert
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Steve Landeau
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Post by Steve Landeau » 30 Sep 2005, 22:20

Lester wrote: I read the phrase "variation in X for each rig" to say that, taking each rig separately, X cannot vary by more than 5 mm, and do not read it as saying that each rig must be within 5 mm of X of each other.
If 1x = 60, and 2x = 65, and 3x = 70, how can 1 and 3 be "within +/- 5? The rule is not clear enough for one to assume that you'll take the middle measurement and use it as a baseline. The way it is written, one could easily argue that a boat with a 60 and a 70 is clearly illegal.
Steve Landeau
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Post by Lester » 30 Sep 2005, 23:47

I don't think the rule regulates the position of the lower measurement band across the three rigs. 1X can be anything you like between 60 and 100; so can 2X, and so can 3X. For example, No.1 can be at 95, No.2 at 80, and No.3 at 60 if you want.

What the rule regulates is, having stepped No.1 at, say, 90, you can then only vary this by 5 mm for the remainder of the event. No way can you drop No.1 down to 65 if the wind should build. Similarly, having stepped No.2 at, say, 70, this can only vary by 5 mm thereafter. No way can you raise No.2 to 100 if the wind should ease.
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Post by Steve Landeau » 01 Oct 2005, 00:04

Interesting view.
If this is actually the case, Then 2 things should be changed:
1) the rule should be better clarified
2) these height numbers for each rig should be noted on the event measurement form. The way it is now, there is no way to show what it was when the boat was measured in.
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Post by Lester » 01 Oct 2005, 00:23

I guess what could be better clarified is whether or not the permitted maximum variation of 5 mm applies during an event. At the moment, this rule is a rule of Part C, which are rules that only apply "while racing". So does this mean that the height of a rig cannot vary by more than 5 mm while "actually" racing, but the rig could be moved up or down *between* races by more than 5 mm? This is not how I read it, because otherwise it is a pretty pointless rule (how could the rig height of an IOM be varied by even 3 mm during a race?) but others may disagree.
Lester Gilbert
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Steve Landeau
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Post by Steve Landeau » 01 Oct 2005, 00:27

Lester wrote:I guess what could be better clarified is whether or not the permitted maximum variation of 5 mm applies during an event. At the moment, this rule is a rule of Part C, which are rules that only apply "while racing". So does this mean that the height of a rig cannot vary by more than 5 mm while "actually" racing, but the rig could be moved up or down *between* races by more than 5 mm? This is not how I read it, because otherwise it is a pretty pointless rule (how could the rig height of an IOM be varied by even 3 mm during a race?) but others may disagree.
Another good point.
In my experience, mainly with big boats, when it comes to changing the boat in any way, "while racing" would mean from the start to the end of a regatta.
Steve Landeau
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Post by cfwahl » 01 Oct 2005, 03:26

Steve Landeau wrote:
If this is actually the case, Then 2 things should be changed:
1) the rule should be better clarified
2) these height numbers for each rig should be noted on the event measurement form. The way it is now, there is no way to show what it was when the boat was measured in.
I don't think that the rule is vague; though I never thought much about it, in rereading it, seems to mean exactly as Lester Gilbert interprets it: "each rig" is not "any two rigs" but a single rig. Each of the rigs can have bottom band anywhere from 60 to 100 mm from the deck mark, and has to remain at the chosen location "while racing". I agree with Lester, that perhaps the meaning of the duration of "while racing" is the only part that might leave doubt.

And I think that the suggestion #2 would create a restriction that the current rules don't intend. Why shouldn't a skipper choose to raise or lower the entire rig for a given regatta, depending on anticipated conditions? Not much different from showing up for a regatta with a completely different A rig than used during the last competition. As long as the new rig has been measured, and falls within class specs, what's the problem?
Charles Wahl

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Post by Steve Landeau » 01 Oct 2005, 05:39

cfwahl wrote:
And I think that the suggestion #2 would create a restriction that the current rules don't intend. Why shouldn't a skipper choose to raise or lower the entire rig for a given regatta, depending on anticipated conditions? Not much different from showing up for a regatta with a completely different A rig than used during the last competition. As long as the new rig has been measured, and falls within class specs, what's the problem?
Dont confuse Event Measurement with Fundamental Measurement.
Reading back on the rules, I am reminded that this is not checked in Fundamental, so that leads me to believe Lester's interpretation is more correct than mine. That, in turn, makes my point stronger for Event Measurement to document the measurement findings. If it is not documented at the beginning of a regatta, there is no way to prove that it had been moved should a protest arise.
Steve Landeau
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cfwahl
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Post by cfwahl » 01 Oct 2005, 22:38

Steve Landeau wrote:
Dont confuse Event Measurement with Fundamental Measurement.
Sorry, my mind missed the "event" (not the first time!). Your point is well taken; obviously if one wants to ensure that each rig is kept to within 5 mm of its original height, one would have to measure its position before racing begins.
Charles Wahl

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Post by Roy Thompson » 09 Oct 2005, 23:34

this rule is a rule of Part C, which are rules that only apply "while racing". So does this mean that the height of a rig cannot vary by more than 5 mm while "actually" racing, but the rig could be moved up or down *between* races by more than 5 mm?
Didn't we once discuss when 'racing' starts? I can't remember if it was on this forum or another but it seems to be a sticking point in a number of rules.
But I do agree with Steve's opinion that it should be recorded at equipment inspection (=event measurement) so that it can be checked during the event.
Roy Thompson
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Olivier Cohen
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Post by Olivier Cohen » 11 Sep 2008, 09:55

On that subject, does anyone know if the +/- 5mm variation wasn't included to consider boats where shrouds tensionning is made by adjusting a screw under the mast?

I think M. Scharmer's boat got something like that.

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