IOMICA Forum

I've been trying to understand CR C.7.3 which states

"Weights of any material may be positioned in and/or on a mast spar below the lower point. Weights of density greater than 8.000 kg/m3 may be positioned in and/or on a mast spar above the lower point."

The way I read this, anything can be used for additional weight (eg Tungsten) below the lower point. What confuses me is the 8 Kg/m3 figure for weight that extends above the lower point.

For example, Air = 3.556 Kg/m3, Carbon Fiber (generic) = 1780 Kg/m3, Cow's Milk (skim) = 1033 Kg/m3. Generally anything solid or liquid (short of aerogels) has a greater density than 8.000 Kg/m3. This second sentence tells me that pretty much anything is allowed for counterweights above the lower point.

If it's a typographical error, and is meant to say 8000 Kg/m3, I'm still not sure what relevance that density figure holds. Lead = 11,350 Kg/m3 and Aluminum = 2,700 Kg/m3, so if the 8.000 (eight, very accurately) figure really is supposed to be 8,000 (eight thousand), this rule still confuses me: it says that I can't use more aluminum, cow's milk, or carbon fiber above the bottom band but can use lead.

Let's assume it's supposed to be 8,000 (eight thousand) Kg/m3 - does anyone have any idea where this figure comes from? Obviously, whom ever wrote this rule had something in mind that he was trying to prevent, but it escapes me.

If it's to prevent the use of carbon (or cow's milk) mast stiffening inserts, why not simply specify it that way rather than being obtuse? (and who ever said our rules were complicated?)

I'm sure the reason is obvious, but I can't see it - HELP!

ps. What does this say about the composition of the jib counterweight?

In CR F.3.3.13 (the mast section), "extra weights" are allowed, and the section above (C.7.3) specifies of what they can be made.

CR F.4.4.b.3 (the boom section) similarly specifies that boom counterweights are allowed, but no section seems to clearly specify of what they can be made.

since C.7.3 applies to weight "...in and/or on a mast spar..." it's pretty clear that it's not talking about the jib counterweight.

Hi Bruce

I can try to clarify a little.

It should be read 8000 kg/m3, 8.000 is the european way to write it.

Why is it then specified, that is should be more than 8000 kg/m3?
I think it's because, you then can't strengthen, when you ad weight to the mast. You are only allowed to use alu or wood, and if you didn't specify a minimum weight/m3, you could use alu or carbonfibre as a weight. Since the rule allowes you to use it abowe the lower band, you can put it along the hole lenght of the mast. If the was no minimum, you could carbonfibre and therefore strengthen the mast, and effectely bypass the rule that the mast should be of alu or wood.
I think the minimum is set at 8000 kg/m3, to rule out iron (~7900 kg/m3). Thereby you are only left with heavy metals, and they are mostly soft.

Regarding counterweights, I can't see that they are limited in any way.

Hope it makes sence.

Søren
DEN 93

thanks Soren - it makes sense that way - reading the rule as written, didn't even get the inference that a rule about corrector weights actually was included to prevent internal mast stiffening devices!

the question of what is allowed for jib counterweights still exists however

since we specified what the corrector weights can be made of ("...anything..."), we probably need to do the same for the jib counterweight.

we could probably propose it as a CR change at the next AGM - Oh wait - we don't know when that's going to take place do we? I wonder how much time we have to formulate proposals for the 2010 AGM?