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Making you own line sets


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#21 BAZ

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Posted 29 May 2010 - 08:19 PM

Yes, I measured 50, 90 and 150lb LPG. It's hard to come up with a single value to publish. Thus, I did the calculations to demonstrate to myself that I was in the ball park with my measurements. My measurement of 90lb LPG was a little less than yours ... about 0.50mm +/- 0.05mm. The 50lb and 150lb came out close to my calculations at 37mm and 0.66mm respectively. Again, a wide variance in diameters based on where you measured and how tightly you squeezed the line.

Your two data points don't follow the trend I'm seeing with the LPG. From a diameter of 0.17mm to a diameter of 0.24mm is close to a doubling in the cross sectional area, yet the breaking strength only went up 60 percent. If we extrapolate to a zero diameter line, then it would have a breaking strength of 20lb. Something must be different between the two lines for which you're showing data. Mind sharing the web site?

Cheers,
Tom


not at all
https://www.tackleuk...tal-p-4203.html
this is what some of the rev fliers i know use and they have had no problem so far
i might give it a go
thanks for your input Tom

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#22 Jeepster

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Posted 30 May 2010 - 06:01 AM

not at all
https://www.tackleuk...tal-p-4203.html
this is what some of the rev fliers i know use and they have had no problem so far
i might give it a go
thanks for your input Tom


Funny site ... breaking strength in lbs, length in yards, but diameter in mm.

Using all of their numbers on the graph, the breaking strength vs area for their product plots in a reasonably straight line not unlike what I showed with the LPG. The zero (no area - no diameter) intercept, using all of their data, now equals 16.2 lbs. They most likely use a different criteria for their published strength than LPG. You might want to subtract 16 lbs from their published numbers when you pick your line strength to get a fair comparison.

You will report back what you find ... yes?

Cheers,
Tom

#23 BAZ

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Posted 30 May 2010 - 09:31 AM

Funny site ... breaking strength in lbs, length in yards, but diameter in mm.

Using all of their numbers on the graph, the breaking strength vs area for their product plots in a reasonably straight line not unlike what I showed with the LPG. The zero (no area - no diameter) intercept, using all of their data, now equals 16.2 lbs. They most likely use a different criteria for their published strength than LPG. You might want to subtract 16 lbs from their published numbers when you pick your line strength to get a fair comparison.

You will report back what you find ... yes?

Cheers,
Tom


Thanks once again Tom
if I do go down that route I certainly will report back

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#24 --Pete

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Posted 19 October 2010 - 08:56 AM

Making line sets:

A technique I have used to make all the lines in a line set equal in length is to make the set "in the air". I have two boards with four nails set in a row about an inch apart. I clamp these to the tops of a pair of sawhorses (you could use chairs, stools, small tables).

I set the sawhorses at the distance suitable for the length I want and begin making lines. I make the first line pulled tight enough that it has just a bit of sag between the nails. This puts a definite and repeatable tension on the line. Then as I make the rest of the lines, I pull them so as to get exactly the same sag as the first line, adjusting the position of the second loop as needed. This is very easy to judge by eye. This way all the lines are the same length at the same tension. I found it too hard to get the lines the same length under tension any other way. Otherwise you would need four accurate tension meters (expensive).


Measuring lines:


Getting accurate measurements of line (and other soft items). While there are screw micrometers with wide flat anvils for measuring soft materials, these are expensive, and limited in usefulness. Many of us have (vernier or dial) calipers. If you put your line under moderate tension and get as much line between the flat part of the jaws as possible, accurate and repeatable measurements are possible. I checked a random piece of braided Dacron line, and the measurement difference between barely closed down on the line and really clamped down was only about 10% and when I tried to put the same pressure on the line each time, the measurements were within a few percent each time. I can't say how well this will match the manufacturer's specifications, but the conversion factor should be easily calculable. (Measure a line you know the specs for; calculate the multiplier; use that multiplier for all future measurements.) (Sorry, the camera focused on the mill, not the calipers.)



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#25 awindofchange

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Posted 19 October 2010 - 11:01 AM

Just came across this post. One of the biggest misconceptions about line drag is that the smaller the line the less drag it will create. This is not always true and in most cases, exactly the opposite. Line drag is created by the resonating frequency of the lines. The lower the resonating frequency the more drag the line creates. Most everyone has heard their lines "sing" to them in the stronger winds. This singing is the resonating frequency being produced by the lines as it moves through the air. The higher the frequency the shorter the resonating wave length of the lines and the less drag the line will be creating. All lines resonate whether you hear it or not. Most of the time the resonating frequency of the lines is below the normal hearing spectrum of your ears, but the line is still resonating.

As the line resonates, it "waves" back and forth very fast. You can re-create this phenomenon by taking an extension cord or Jump Rope and wiggling it back and forth really fast. The total distance created by the "wave" of the line is what creates the total amount of wind resistance - NOT the actual diameter of the line. So having a line that is less than 1/8" in diameter, but is resonating at a distance of 2" will create the same amount of wind drag (or even more) as a 2" diameter pipe. The reason that the wind resistance can even be more than the same size pipe is that the wind flows evenly and smoothly over the roundness of the pipe but is abruptly disturbed as it flows around the "wave" of the line, making the line appear to be even larger in the eyes of the wind.
Powerline Sports is a manufacturer of Q-Power line, similar to that of Shanti and Laser Pro and also produces line for many military and commercial applications. Powerline Sports created a specialized spectra line that has a linear wrap around the entire length of the spectra line - called Q-Power line. This extra wrap nearly doubles the overall diameter of the line compared to the same test line produced by other companies. Q-Power line has been wind tunnel tested against other lines including LPG and Shanti and has proven that the larger diameter line with the specialized linear wrap actually produces less wind resistance and overall line drag than any other line on the market (as of 3-4 years ago anyways). The reason is that the linear wrap of Q-Power line allows the wind to flow smoother around the line and the extra stiffness of the line reduces the amplitude of the resonating frequency. One of the most noticeable feature of Q-Power line is that it "sings" much louder and higher pitched than other lines.

I am not pushing or pimping Q-Power line, just using their line as an example to show the differences in diameter and the effect it has on line drag. We use a ton of Q-Power line for our power kite sports, especially kite surfing and snow kiting. The line is pretty awesome in that the extra linear wrap means that you never have to use sleeving, just fold and tie. The line seems to last much longer than other line as well. I have some Q-Power line sets that I have been using on my traction kites for over 8 years with no show of wear (other than they are quite dirty now).

The biggest reason that light weight line is used is not because of the smaller diameter and less line drag (myth), but more because of weight savings. Trying to fly an indoor Rev on 200# Q-power line will just be silly. You will have nearly zero line drag but the weight of the line will kill the flight of the kite. Weight savings would be much more important than that of line drag, especially when flying indoor or in SUL conditions where kite speed is so slow anyways. When flying my Focus Manta in zero wind conditions we can see the difference in line weight. Right now it has 130# waxed line on it which is easier to feel, see and grab than the thinner 50# Spectra line. You can see the heavier line actually pull the nose of the kite down more than the lighter weight 50# line. The reason I like the heavier line is because it is easier to grab when pulling the line in, pays out easier when you set the Manta into a glide and it rarely ever tangles up. Tangles were a constant pain with the 50# line but the glide was slightly better. :)

Anyways, just wanted to add some food for thought. Not that it means anything at all, but it may give you something to BS about the next time you are sitting around waiting for the wind to pick up. :) :)

As always, this post is worth exactly what you paid for it.

#26 Baloo

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Posted 19 October 2010 - 09:52 PM

Making line sets:
(Sorry, the camera focused on the mill, not the calipers.)




Dont you just hate it when that happens. :)

Thanks, interesting post Pete.

#27 Mike

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Posted 20 October 2010 - 05:43 AM

That was really interesting Kent, it will be something to talk about at the next gathering of engineers/kite fliers. Thanks!
Mike Kory:
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