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Discussion Starter · #1 ·
I've been working on a flying ghost aka Axworthy ghost and I'm wondering what type of thread and wire to use and also what gauge and color. I was originally thinking of using either fairly thick (2-3mm or about 1/10 inch) nylon braided rope or non-braided nylon fishing rope.

However while browsing through this forum I discovered the Axworthy from Spirit Halloween and that uses Spiderwire brand braided fishing rope which is much thinner than what I was thinking of using.

Obviously I do want the wire to be as invisible as possible so I was wondering what gauge of wire I should use when I decide to go with Spiderwire and what color?

There are various gauges:

Gauge (thickness in mm)Tensile strength (kg)Tensile strengh (Pound)
0.065.411.9
0.087.316.1
0.097.516.5
0.1110.322.7
0.1312.728.0
0.191839.7
0.2323.652
0.2926.458

I don't really want to have to try different thicknesses as that would get rather costly. For safety I could just go with the 0.29/26.4 wire of course but how visible would that be? And how (un)necessary is that. The ghost I'm planning on using weighs about 300-400 grams (11-14 ounces). The wheels I'm using have a rectangular groove which I think will help in keeping the wire on them compared to round grooves. And Spiderwire apparently has very little stretch to it so that should help to reduce the require amount of tension.

However, I have no idea how much tension I will need to put on the rope to keep it from sagging and to ensure it will stay in the groove of the pulley wheels.

Also, what color would work best? Black does not appear to be available but there is a rather dark 'Moss Green Smooth Braid' and there is also a translucent. However if I understand correctly the translucent actually has a light green tint to it so I'm not really sure exactly how translucent it is, hard to tell from pictures.

TL;DR: So, which gauge works best and which color? Or is there another option I should consider?
 

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Discussion Starter · #2 · (Edited)
The above table refers to their 'Stealth Smooth 8 Translucent' line but I just noticed they also have something called 'SpiderWire Ultracast Braid Vanish'. I like the sound of that but maybe the Vanish bit just refers to that type of rope not floating on water?

EDIT: Hold on. After reading the description of the Vanish product again it has become clear that this box actually contains two completely different spools, one with a braided and the other with 'Berkley Vanish Fluorocarbon leader' which appears to be a monofilament and is probably the invisible bit. Unfortunately I have zero knowledge about fishing.
 

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I don't know that I have all, or heck, even any of the answers - but will throw out a few points to consider:

You say the ghost is max 400 grams, so that is a good start. (though seems to be a bit heavy compared to the styro balls and light fabric ghosts I typically see) Also take into consideration how long the runs are and how much sag you can tolerate in the rope. There are some fancy calculations, but in general the longer the run, the more stretch/sag there will be in the wire, so higher tensile strength would be needed. Also, maybe not an issue, but at least worth considering - does that 400 grams include (or need to include) any water weight. Any chance the ghost can get soggy from a rain or foggy/misty evening?

If you want to play around a bit, I'd suggest two calculators:

A 'tension on rope' calculator. Just ballparking some numbers...400 gram ghost, 3 degree angles on the rope (sag due to weight) and that puts about 8.5 pounds of tension on the rope. You'd likely want to double or triple that for safety and longevity, so that already starts to put you near the top end of the range.


Next, look at a triangle calculator. In this case, punch those numbers in... angle A and angle B at 3 degrees and side c to your longest run. For example, I chose 50 feet. Calculate that and what you're interested in are 'vertex coordinates' which shows a C of 25, 1.31 for my example. This means with the ghost at the center of the run, the wire will sag 1.3 feet.


You can obviously run these forward or backward. If you have a known distance and max sag you're willing to allow, punch that in, then go back to the tension calculator and see what that does to the tension. (hint: shallower angles make substantially more tension!)

As far as color - would depend a bit on your set-up. These ghosts are typically overhead, so would the spectator be looking up into a black sky? green trees? colored ceiling / wall? etc. I'd probably try to get the wire to be some relatively matching color. The actual background will come into play too. If it is a dark patchwork of irregular shapes like tree branches, leaves, etc - then you likely have virtually nothing to worry about in seeing a black or dark green wire. Though if it is a smooth, moderately lit ceiling, then the wire would likely stick out a bit no matter what color.

As far as square pulleys - I don't know about that. A round or V or U notch seems to have somewhat of a 'self correcting' feature where the string starts running to either side and that creates a bit of tension which nudges it back to center. With a rectangle, there is no self correcting and the string may tend to rub the side and jump off at random intervals. With that said, I believe some have successfully used bike wheels for pulleys, so might not be a huge issue as long as you can guide the string relatively straight. But if you run into troubles, creating more of a V might be a good start.

Obviously a lot to consider but overall, I'd likely just go with one of the stronger strings. It will be less hassle overall, less chance of breakage and if anybody starts gawking around looking for a wire, jump out and scare 'em and send 'em on their way!
 

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Discussion Starter · #4 ·
Thanks, that is very helpful. I'll do some calculations myself with those calculators but you're probably right about needing one of the stronger strings as I do want to minimize sagging.

Background for the string will be either the night sky (although most activity will be between 6pm and 8pm so it might not be fully dark by then) or the red brick facades of the houses on both sides of the street. I was thinking translucent might work best, except perhaps if it's also reflective and the darker color isn't. Decisions decisions...
 

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Discussion Starter · #6 ·
Thank you for that. You made me realize that one option I was considering is not going to work. I was thinking I might just get away with 'suspending' the satellite pulleys on one or two ropes and then pull them horizontally. That would probably not have worked with even the strongest Spider Wire due to the limited tensile strength, but even with my original much thicker nylon rope that would probably not have worked since as the ghost gets closer to the pulley it's going to cause that pulley to turn downward on the side where it approaches which would certainly result in the wire derailing. Definitely need to make sure those pulleys are firmly fixed so they will stay horiztonally no matter what.
 

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The year after that video was taken I reworked the pulley assemblies and added guide arms with little rollers on them to try and keep the string from derailing. That did help, sort of. I think I over engineered the thing. I think that having some sort of guide that takes the weight of the string is needed, but not sure how they should be designed. Look forward to seeing what you come up with.
 
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