What's the real diameter of my lines other issues:

[GERALD WIMMER]

Having made up many sets of Spectra lines I have a few observations and questions.
Been flying only Spectra for the last few years (except for my sons use steel for combat or team race, usually as required) and their seem to be some issues others may have seen too. 
There seems to be a big difference in the way Spectra line diameters are measured with some manufactures giving a deceptive flattened measurement that is nothing like the diameter we see when flying. When compared to steel they look good on paper but when compared with my Mitutoyo micrometer some appear to be presenting a lot more drag and you can feel this as less overhead tension and reduced speed.
There is a big difference between brands as most will know but I have also seen differences between batches of line and even between differences in colour of the same brand and rating. 

A common problem I have too is after pre-stretching some shrink back more then others and if you cut your lines to length before pre-stretching they normally end up oversize. It can be hit and miss not knowing how much each will change after the 'preconditioning' and how much or long we should pre-stretch before use or cutting to length.

First some steel lines test ratings for diameter comparison (test data from Ruslan Kurenkov).

Stainless 0.015” breaks @ 25-27lb
Stainless 0.018” breaks @ 38-40lb
Ukraine Steel  0.0145”  breaks @  48-50lb
Ukraine Steel  0.0155”  breaks @  50-53lb
Ukraine Steel 0.018”breaks @  60-64lb
Laystate Modelair soldered line 0.026 (Easily kinked being solder covered, stuff of my youth)
PAW products 3 strand high tensile solder covered line
Staystraight 0.012 with 24lb breaking strain rating
Staystraight 0.015 with 36lb breaking strain rating
Staystraight 0.020 with 57lb breaking strain rating

Line diameters non steel: Measured without squishing with micrometer

Terylene 0.025”   Like we used for our Cox 049 models many years ago
Kevlar pulled round 0.023   Oval or nearly flat section making it very draggy
Dial cord 0.028 Strong radio dial adjustment cord, round section and light but no good when wet

  Spectra lines
30lb Berkley    0.014” a nice smooth line
30lb Maxistrike 0.014” ('The Warehouse' brand a little more stretch)
50lb Maxistrike 0.019”
65lb PowerPro Maxcuatro 0.016”
65lb Fins 40G 0.019”
65lb Spider Power 0.024”
80lb PowerPro Maxcuatro 0.019”
85lb Fins 40G 0.020”
100lb PowerPro HollowAce 0.032” Not recommended for flying , leadouts maybe?
100lb PowerPro Maxcuatro 0.021”

Note stainless steel 0.018 will squash down to 0.011” with a hammer and anvil
If you squish Spectra lines down Maxcuatro 65lb it will reduce to 0.005” and Fins 65lb down to 0.009” but this is not the diameter you fly with.           
My favorite all round line for slow combat and medium sized stunt/sport models is the Maxcuatro 65lb and this seems to compare most closely to 0.016thou steel while Fins 65lb is smoother it seem like it has more drag . The 45lb Fins may be a better match with its 61lb break rating.

[katana]

Query - did you tension the braided test sample before measuring?

Wire doesn't compress its diameter to any great degree under tension but braid will as there are voids between the fibre strands and the diameter could be much less than when un-tensioned.

Also did you test breaking strain or are you taking manufacturer claims at face value?

With braid being so 'soft', I don't believe a std. micrometer is the correct tool for measurement - even only using the clicker the anvils will likely squish the braid to a degree skewing the result IMO.

I've no axe to grind as I have no preferences having only ever used wire and have several sets of Ukranian pre-made wire sets to see me out.

[John Carrodus]

Gerald, I've never seen your work bench lookin soooo tidy.
Good research with interesting findings. I think your last sentence gets the cigar.
Cheers
John

[GERALD WIMMER]

Hello

Yes John my workbench is a mess , been trying to tidy up as I go but the covid has still got me working slowly and running out of puff.

On pre tensioning yes I pulled it up before measuring and yes the clicker ratchet/tensioner on the micrometer crunches it up a lot so was not used but I did get consistent measurements that my digital veneer could not give .

Only interested in why some lines seem more draggy then others and wanted a measurement comparison and not testing line strength.

I think you will find big differences in how manufactures measure line thickness/diameter and this is what I am highlighting.

bye Gerald

[Lauri Malila]

One reason is, that depending on braid type, the cross section of line is not round when it comes from storage reel. It is usually flat or square, and seems to be more permanently so in the end of a big reel.
That makes the line flutter in airstream, and drag goes up.
I don’t know how long it takes in cl when the line becomes more or less round, but usually in free flight it takes about 100 flights to stabilize. In launch height, difference between new and well stabilized line is about 5-7m. So a fluttering line absorbs quite a lot of energy. L

[Dennis Toth]

 Gerald,
Interesting work. Your numbers differ from the manufactures by a significant amount. Here are two site that give the Maxcuatro (https://www.powerpro.com/content/powerpro/northamerica/us/en/homepage/PDP.P-MAXCUATRO.html) (note the line diameters are in mm) and FINS 40G numbers (https://www.finsfishing.com/FINS40G-p/fns40g.htm). For the 65LB Test line the Max is 0.36mm which converts to 0.0141 inches, the FINS 40G is 0.011 inches. Not saying your method of measurements is wrong but since these are lines designed to be thin and go on reels where they can pack the most line on those reels and the Fishing community is much larger then those of use flying CL they would make a fuss if they were getting wrong information as it misleads how much line they can have on a particular style rig.

However, the exact diameter is really not our concern since we are concerned with strength and drag. Did you fly all the lines you tested? That is where the rubber meets the road. For me the only real advantage of the Spectra lines are you can reduce tip weight and for the same strength as SS lines they are thinner and less drag. The reduced drag for my electric ships allows a small capacity battery pack and significant reduction in battery weight.

I have flown both the Maxcuatro 40LB Test line and the FINS 40G 45LB Test line on the same ship and the FINS 40G was less drag then the Max and reduced amp draw down by 4%. This allowed using a battery pack that was ~1oz lighter then the pack normally used for a 35 size ship. Also reduced tip weight by 3/8oz. That is a significant amount for any stunt ship. For IC's I think you could compare lap times between the different brands to see which one has less drag.

There are lots of brands of very thing and Spectra lines at many different price ranges. If you can do some flying tests and report back on your findings, it will help us all get better performance from our ships.

Best,   DennisT

[Ken Culbertson]

You need a pretty good micrometer and a pretty light touch to be able to get accurate readings on something that is soft and woven.  I wonder what the manufacturer uses to stretch the line for wrapping on the spool.  Does the actual diameter really mean that much?  We are only concerned with stretch, weight and drag. Diameter is only a factor in that equation.  On the planes I tested, once retrimmed, the only serious benefit I saw from "Spectra" was battery usage.  Still, all other things being equal, that is a legitimate reason to switch.

Ken