Net Height measuring tool... suggestions?

[Retrozetti]

I was just at this season's USAV Rules Meeting, and we were cautioned that certain net measuring chains will stretch and lengthen in time. Also, those chains offer good "approximate" heights, but they're not "exact." Does anyone have suggestions on a best & most accurate net height measuring tool? Thanks.

[TimTaylor]

How about a tape measure

Seriously, I have one of the beaded chain versions & it works quite well. I adjusted it when I first got it to make sure it was accurate - only modification I made was to paint the appropriate marker bead for HS red to make it easier to see.

The whole stretching argument doesn't make much sense to me. The only way to make a material stretch enough that it results in permanent elongation is to apply opposing (pulling) forces sufficient to overcome the material's yield point or elastic limit. What was their explanation for the cause?

[MCBear]

I have a net measuring chain that has a distinct color change from women's to men's heights. I never remove the extension for the men's net height since it all the beads are black from the connector to the end of the chain. All the rest of the beads in the women's length are pink, green, yellow...i.e., multi-colored.

As for verifying the length, when I first got it, I measured both heights on the chain using a tape measure so that I knew if the indicators were correct or not (and they were both correct).

However, if you want to go hi-tech, there is an electronic laser net measuring device that is available from most officials' suppliers.

[refnrev]

Retro...
I'm not an engineer by any means, however, I, Like toolman, am wondering why your colleagues are suggesting that the chain would stretch. Mine sits in my bag, comes out for a couple of minutes, hangs, and goes back into the bag. I'm having trouble buying this one... however if anyone has experience to cite otherwise, I'd like to hear it. RR

[IHSAref]

Where can you buy one that is multi colored? All the ones I have gotten are all the same color with not extra link

[refnrev]

Mine just has a collored dot for G, B, and I think MS. Got it from the old NFHS supplier. I think they call it getofficial.com or something real close to that.

[refnrev]

Originally Posted by IHSAref

Where can you buy one that is multi colored? All the ones I have gotten are all the same color with not extra link

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IHSA,
Did you get to see the Maroa - Carlinville match up? I wanted to go but it was a little too far for me that night. They say Marao has a one girl wrecking crew that's headed to Ohio next year.

[MCBear]

IHSARef, I got my multi-colored chain through the NCVA, the regional arm of USAV here in Northern California.

[IHSAref]

Originally Posted by refnrev

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IHSA,
Did you get to see the Maroa - Carlinville match up? I wanted to go but it was a little too far for me that night. They say Marao has a one girl wrecking crew that's headed to Ohio next year.

I did go see that match-up. Rachel Hockaday is the one girl wrecking crew. She is a pretty good player. She is getting offeres from Bowling Green, Indiana, and other D-I schools. If you can get down to Illinois State this weekend I would recomend it. They play friday at 12:30. I will be there

GO TROJANS!

[Back In The Saddle]

Originally Posted by refnrev

Retro...
I'm not an engineer by any means, however, I, Like toolman, am wondering why your colleagues are suggesting that the chain would stretch. Mine sits in my bag, comes out for a couple of minutes, hangs, and goes back into the bag. I'm having trouble buying this one... however if anyone has experience to cite otherwise, I'd like to hear it. RR

Unless you use your net chain as an emergency car tow chain, the only reason I could see for it to change length would temperature. Metals contract and expand according to temperature just like any other material. Perhaps if you used the same chain at 120 degree beach volleyball matches and 65 degree indoor matches, it would vary in length (depending on the metal used and the construction of the chain). But certainly not very much.

[Retrozetti]

Originally Posted by refnrev

Retro...
I'm not an engineer by any means, however, I, Like toolman, am wondering why your colleagues are suggesting that the chain would stretch... I'm having trouble buying this one... however if anyone has experience to cite otherwise, I'd like to hear it. RR

I "want" to agree with everyone's input here... but it was at a USAV Rules Meeting that we were informed.. I have to give it legitimacy. Now onto the science... I'm going to trust my net chain, but I'm going to measure it's length and track it every season. If I notice the chain lengthening, I'll post an update. One thought, when checking net height, I hang it alongside one antenna, remove it, then hang it alongside the other antenna... however; while prepping for an NCAA match, I saw a coach hang the chain alongside one antenna, then leave it hung on the net and "dragged" it along the net to the other antenna. I can absolutely see how that might stretch the chain over time.

[TimTaylor]

Originally Posted by Back In The Saddle

Unless you use your net chain as an emergency car tow chain, the only reason I could see for it to change length would temperature. Metals contract and expand according to temperature just like any other material. Perhaps if you used the same chain at 120 degree beach volleyball matches and 65 degree indoor matches, it would vary in length (depending on the metal used and the construction of the chain). But certainly not very much.

Lets assume mild steel or similar ferrous alloy. The thermal coefficient of linear expansion is approx. 0.0000073" per inch of length per deg F. Using BITS's numbers (65-120) the net change in length of a 88" chain would be would be approx. 0.035332" - hardly significant. For aluminum it would be approx. 0.059532", brass would be approx. 0.050336".

[refnrev]

Originally Posted by TimTaylor

Lets assume mild steel or similar ferrous alloy. The thermal coefficient of linear expansion is approx. 0.0000073" per inch of length per deg F. Using BITS's numbers (65-120) the net change in length of a 88" chain would be would be approx. 0.035332" - hardly significant. For aluminum it would be approx. 0.059532", brass would be approx. 0.050336".

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You know, Toolman, I was thinking the very same thing.: confused:

[TimTaylor]

Originally Posted by refnrev

_________________________

You know, Toolman, I was thinking the very same thing.: confused:

Sorry, sometimes the geeky engineer in me sneaks out...

Actually, both of my posts were my subtle, tongue in cheek way of saying that if USAV is challenging the accuracy of some net chains, lets see the supporting data. Clearly there's no physical property of any common metal that would result in lengthening over time under normal use, so it must be something else. Is it a design issue...i.e.; light gauge open links that can deform under tensile load? Or perhaps (here comes my cynical side) it's related to who ponies up the bucks to get "USAV approved".

My point is, all we have so far is "a conclusion derived, from information inferred" -" it must be true because USAV says so". In engineering circles we call that a WAG (wild-assed guess).

[refnrev]

Originally Posted by TimTaylor

Sorry, sometimes the geeky engineer in me sneaks out...

Actually, both of my posts were my subtle, tongue in cheek way of saying that if USAV is challenging the accuracy of some net chains, lets see the supporting data. Clearly there's no physical property of any common metal that would result in lengthening over time under normal use, so it must be something else. It it a design issue...i.e.; light gauge open links that can deform under tensile load? Or perhaps (here comes my cynical side) it's related to who ponies up the bucks to get "USAV approved".

My point is, all we have so far is "a conclusion derived, from information inferred" -" it must be true because USAV says so". In engineering circles we call that a WAG (wild-assed guess).

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I was just having fun telling you that I had absolutely no idea what you were saying, how to calculate that stuff, etc. I still think the idea of a chain stretching is very farfetched at best... and if the guy is really worried about it, get a cheap tape measure and forget the chain. The tape measure won't get all tangled up either!