How to split 3000' of line?

An intriguing problem!

Hmmm…I’ve not worked with kite string, but I’d be concerned about either tangling, or twisting stress on the line if you unraveled it that far in an open space and then wound it back up. The trouble is you can’t count revolutions, because as the spool dwindles, each revolution is a different distance.

The arduous route would be to set up the target spool across the table from the source spool and mark off (count, really) feet or yards as you slowly wound it from one to the other. I’m curious to hear…there must be a very clever solution to this…

@Mangus:

Interesting ideas—you could actually do it something like 10–20’ at a time with something like a clothespin to track where you were in each section. (e.g., clip the clothespin, run the line to the spool 20’ away, unclip the line and bring it back). Seems not too painful. At 20’ runs it would only take 75 “passes” to spool out 1500’, that’s definitely doable.

The twisting shouldn’t be an issue—the spool of line has been wrapped correctly from the factory, as long as we take off the spool by unwinding, we won’t introduce any twists, and the winders we’ll be putting it on are designed to not introduce new twists.

Potentially go reel to reel like the first suggestion, using identical spools, try and wind it as evenly as possible, and stop when they’re at equal diameters?

Surely there’s a mathematician in our midst who could figure out the equation for revolutions, taking into account the ever increasing diameter. I, of course, am not him, as math is but an abstract idea to my primitive brain, but it seems doable, as the entire Universe is held together with duct tape and mathematics.

How about it Fluther?

Weigh it. When you have half the weight, you have half the line.

Remember the old joke about counting the cows in the field? You add up all the legs and divide by 4. What about anchoring one end, then driving and unspooling out the window (so string doesn’t drag) for a previously measured 1500’ ofdeserted road. Or call the company for ideas. (cwilbur’s concept does seem the simplest.)

I think the weighing and diameter ideas are problematic because they both require very sensitive instruments. Assuming the goal is an exact 50/50 split, the difference in weight or diameter of 10 or 20 or 100 feet might not be easily measureable unless you have a lab-quality scale or calipers.

The precision of the instruments you need depends on how precisely you need to divide the line. If you can find a good knitting or yarn store, they will have tools to wind and weigh yarn, because this kind of problem is one that fiber crafters frequently encounter. Scales accurate to 0.1g are fairly easy to come by, and odds are good that a good yarn store will have one.

cwilbur—looks like this line weighs in around 0.3g/foot (or so), so 0.1g is plenty accurate (unless the line’s mass decreases continuously through the spool, random errors will not accumulate in either half)

However, do you know what the maximum capacity of a yarn winder might be? I’m guessing I may need as much as 700g of capacity, which seems like a lot of yarn.

Different yarn winders have different capacities—the capacity is usually expressed in terms of weight/mass, but practically speaking it’s the volume of the wound ball that matters. If this is sufficiently dense line, more dense than spun wool, you might be able to do it on a 100g ball winder.

Alternately, you could wind it by hand onto a spool, taking the weight of the spool into account.

So the method I’m leaning towards now is very similar to Mangus’s method.

I have a winder that is just a wooden spool with an axle, with about a 2’ circumference, and I’m thinking the method is going to be to pull off of the factory-spindle, wrap 1.5 times or 2.5 times around the wooden spool and count revolutions, and have someone taking up onto another winder to keep a little tension on the spool.

If it is a 24 +/- 1/8” diameter spindle, that means my error will be +/- 8’ of line total (since I’m winding 750 times, 750*0.125 = 94”), I just need to measure the circumference of the spool within +/- 1/16” to be safe.

But the circumference you are winding on changes as you get more and more line on the spool. But I’m not sure I have a good image in my head of how thick the layer of wrapped line is on your spool. If it is thick, then as you get more and more on the target spool the amount added per revolution will increase, making your measurement even further off. But if you are ok with +/- 8’, then probably that’s still ok…this is my favorite sort of Fluther question. SO fun. :)

@Mangus:

The “measuring spool” has a flat wrap (constant circumference) that is—in effect—piling up on the floor as it comes off.

Much with a capstan on a sailboat—the line wraps on and back off, the multiple wraps keep the line from slipping along the spool.

So, rather than the circumference changing as the line piles up, the line just piles off the winder, keeping the circumference the same at the point at which it is being measured.

Brilliant! I totally missed that detail. Very nice.