ADVENTURES IN SPECTRA

[Mike Alimov]

Secondly, since my decision matrix is between Spectra and the Ukraine lines, has anybody done a stretch comparison between the two?   My anecdotal experience is that spectra stretches more but the literature says less.  It also seems to have more rake but, my ability to do my usual video analysis is grounded.   Anybody have any thoughts?

Ken

Ken, instead of asking for thoughts or opinions (which many here readily offer), ask for measurements. 
It just so happens that I was wondering the same thing, so we went outside today and made some measurements. 
Methodology: four types of lines were measured for stretch.  Each line (single line, terminated per AMA rules) was anchored firmly at one end, and pulled by the other end using a fish scale using a 20 lb load as a randomly picked load, consistent across all lines.  The amount of stretch was measured by observing the displacement of the line end using a stainless steel ruler placed on the ground.  A slight preload of 1 lb was applied to the line to straighten it out, then the ruler origin was aligned with the line termination (eyelet or knot), and a 20 lb load was applied. At this load, the stretch was measured against the ruler.  Then the measured amount of stretch was divided by the overall line length (different lines came from sets of different lengths), and the elongation percentage was calculated.  Here are the results:
Brass plated 4-strand (Ukrainian) 0.0165" elongation 0.5%
Stainless 7-strand 0.018" elongation 0.41%
Stainless 7-strand 0.015" elongation 0.63%
PowerPro Maxcuatro 65# elongation 0.72%

In addition, the PowerPro Maxcuatro 65# line was stressed to failure, and once again we registered a load of about 42 lbs when the line failed (not at the knot). 
So, at this point I can say that even though the Maxcuatro 65# will withstand the 10g line pull test, it stretches even more than the 0.015" stainless, and thus is not very attractive for use in full-size stunt planes, despite its low weight and low drag (0.014" diameter).

So far, the least stretchy line that we have tested is the good ole' 18 thou stainless.  I don't have other lines to test at this moment. I would be interested to have others perform a similar 20 lb stretch test and report their measurements on other lines (such as PowerPro Maxcuatro 80# or 100#).

[Dennis Toth]

Mike,
Very interesting information, it would be interesting to know the length of the line you tested, what type of clip you used for the terminations and what type of knot and the process you used to tighten, chinch down the knot. Some of these things can impact the stretch, also did you do a pre-stretch to the Spectra line? Some have indicated that once you set the knot you need to load on the line up to 60 -75% of the line rating a couple times then it will be set, then check the stretch.

Bests,   DennisT

[Mike Alimov]

Mike,
Very interesting information, it would be interesting to know the length of the line you tested, what type of clip you used for the terminations and what type of knot and the process you used to tighten, chinch down the knot. Some of these things can impact the stretch, also did you do a pre-stretch to the Spectra line? Some have indicated that once you set the knot you need to load on the line up to 60 -75% of the line rating a couple times then it will be set, then check the stretch.

Bests,   DennisT

Dennis, I used a single 50 foot long line of the 65# Maxcuatro, terminated with a Uni knot, cinched all the way to the scissor-style metal line clip, and pre-loaded several times.  As I mentioned before, there was no problem with the knots: they did not give out, slip, or induce failures. 
To make the amount of stretch a little easier to visualize, the 50' line stretched about 4 inches under a 20 lb load.  We typically need about 1 inch of line movement to turn a sharp corner.

What I need to emphasize is that the line being tested (65 lb rating, 0.014") was much thinner than is being used in combat, and the line that was tested by Dennis in his original post, which is 100 lb line (0.018"-0.017").  Just as is with the steel cable, it looks like the thicker line is both stronger and less stretchy.  I was hoping to capitalize on the premise that the Spectra fiber is stronger than steel, and therefore can be used in smaller diameter, thus reducing the parasitic drag and saving us some battery charge.  But it turns out that the amount of stretch at those lower diameters is such that the control feel will be lost, and that's not the price I'm willing to pay for reduced weight and drag.
So, back to the 100 lb line - still lighter, smoother, and stronger than steel, but not necessarily less drag.  Oh well, can't have it all.

[Reptoid]

Help me understand.......
     After reading through hundreds of posts about spectra and associated other brands of fishing line and the attempted use by many for control line flying. I can't find the big advantage that you all are looking for other than slightly lighter in weight. From what I have seen that is the "only" plus in a world of minus as far as it's use. It looks like to get a safety margin I'd be comfortable with, the diameter is going to be the same or larger as stranded stainless or plated steel.
     I have been using steel lines for over 65 years from 1/2A to 60 size controline aircraft pretty much trouble free. I make all my own lines and they are easier to make up than fishing line, they stretch very little, and if terminated correctly, last a long time and don't fail. In addition, I can make them dead even every time.
     I can make lines from bulk for less money than you're spending on fishing line and can get all the sizes in bulk easily from Melvin Schuette (MBS). He also sells wrapping wire, crimp sleeves, and eyelets. I use those lines for everything from 1/2A(.012") to fast/slow combat (.018") to my stunt airplanes (.015"). For F2D aircraft I use pre made lines from the Ukraine (.0154" x 52'2.77")as we go thru some due to tangles, crashes, etc and they are very inexpensive @ $6/set ready to fly. These lines on an F2D are pull tested at 45lbs for an airplane that weighs about 18 oz RTF ( yep, that's about 40G's)
     So, what am I missing that motivates you to fly fishing line?

[John Park]

[quote Some guys have concern about securing to a line clip because of the tight radius. The thimble will spread the load.  So far in combat the only area of concern has been where the line passes thru the leadout guide. In time chaffing has occurred,  which will cause an eventual failure.
  Phil C is really the authority on the knot. He says modified surgeons,  thats alright by me!

Tom

I sheathe the part of the clip where the line goes round, using the trick described in my earlier post.  It's fiddly, manoeuvring the soft, floppy PVC tubing into place on the clip, but when it hardens it increases the diameter of the clip to a useful extent.  Also, it's not going to be as potentially abrasive as the wire of the clip itself.

John

[GERALD WIMMER]

Hello In reply to some of Don's questions I think better quality steel lines will still have the drag advantage over Spectra for F2b as you need 80 or 100lb line to reduce the stretch , I found 65lb stretches too much for medium or large models.
Spectra will probably become the line of choice world over for general sports flying and slow combat where rules allow it. This is because the lines feel nice and light and the model changes direction easier but you need to try them to see the difference. The lines only take about 5 minutes to make up, which I can say after videoing this process recently after making over 20 sets now. They are very cheap if you buy a big roll and very durable in combat and general use surviving tangles and trip overs better then anything else I have used.
I think there has been some poor quality line out there perhaps falsely rated, marketed or packaged but the Power Pro Max Cuatro I have used has been good and tested well but on the other hand other brands of line I have experimented with have proven surprisingly good too.

One thing nobody has mentioned as a down side that infuriates me with Spectra is its ability to get tangled up in twigs and small branches or stuck to bark on trees if blown by the wind but this normally only happens on ruff sites or windy days due to its fibrous nature and light weight.
My sons and wife always prefer to fly Spectra where rules allow but few locals around us fly it let alone try it .

Regards Gerald

[Jim Svitko]

When I first heard of Spectra and similar materials for lines, I was interested enough to do my own tests, as others have done.  I was looking for an alternative to the stranded steel lines and it looked like Spectra was the way to go.

It has been a few years now since I messed with Spectra lines. The Power Pro is the only version I have tried so my experience might not be applicable to other brands of similar material.  At that time, these lines were not approved for use in the events I fly.  Therefore, I saw no reason to go any farther with them after my testing period and I gave up on them.  Any notes have been lost since then and I have to rely on memory here.

After doing pull tests and flying with these lines, I am on the fence.  Yes, there are advantages--less weight, less susceptible to damage from walking on them and getting kinks, faster to make up a set.

But, there are disadvantages, at least for me.  One negative aspect was the greater drag.  The bow in the lines was far greater than with stranded steel lines.  How does that affect leadout position?  I never figured out how to deal with that greater drag.

I did pull tests on lines of different rated strength.  Most of the testing was with the 65 pound and 80 pound line.  From what I remember, the line broke at approximately 60% of the rated strength.  The line never broke right at the knot.  It usually broke about an inch or two inches from the knot.  The only knot I used was the Uni knot.  I seem to remember that the Uni knot was the approved knot as stated in the rules at that time for general use and sport flying with Spectra.

I also did some stretch tests, using a metal scale taped to the sidewalk to measure stretch.  The Spectra stretched more than steel lines.  I can't say exactly how much more since my notes are gone but I do remember being disappointed in that there was no advantage there over the steel lines.

After doing my tests, I see no clear advantage to using Spectra, at least for my use.  But, others might find them acceptable and possibly superior to the steel lines.

If time permits, I will look into more tests with the newer products and maybe I can be convinced to use them.









 

[Ken Culbertson]

....but few locals around us fly it let alone try it .
Regards Gerald

This seems to be universal!

I sheathe the part of the clip where the line goes round, using the trick described in my earlier post.  It's fiddly, manoeuvring the soft, floppy PVC tubing into place on the clip, but when it hardens it increases the diameter of the clip to a useful extent.  Also, it's not going to be as potentially abrasive as the wire of the clip itself.
John

Can heat shrink tubing be used for this?  It seems like a really good idea.  My experience mirrors Jim's minus the break testing.  My use test was before I switched to the Ukrainian lines and well before their newer offerings.  I concluded that they were usable but I did not want to practice with something I could not use in competition.  I am glad we have the new rule though, it makes sense and will no longer be the roadblock to innovation.

Ken

[Dennis Toth]

We seem to be getting into analysis paralysis talking about the stretch of the lines. Most people doing stretch tests have been using a pull of several times what would normally be expected from a stunt ship. Most ships pull less than 8 lbs. at the speeds we fly. The other thing to consider is that this load is applied over two lines, so the actual line area is double. If you are looking for an excuse not to use Spectra lines you can say they stretch too much at 10x the model weight, that's OK. But in reality, at normal flying pull, it is not a real issue.

The lighter weight, durability and thinner diameter on the newer smooth 8 braid Spectra lines will reduce line load and can help reduce fuel/amps needed, which in turn reduces model weight. Seems we need to be looking to find the brands with the most strength, least stretch and strongest, most reliable termination rather than worrying about a non-critical issue.

Best,   DennisT

[Dennis Adamisin]

We seem to be getting into analysis paralysis talking about... AMEN!
Best,   DennisT

In my case my next flights may not happen until May. I am not terribly concerned about strength of line or knots, my main parameter will be stretch.  I will be testing 80# Maxcuatro back to back with original Power Pro 100# which I know works.  If my airplane pulls 8 lbs then I will be loading my lines (2 x 80# capacity) to 5% of there rated load.  I think it will be OK.  If I do not like the Max 80#, then I can either try Max 100#, original PP 80# which both have larger diameters (and presumably less stretch), or just go back to the original PP at 100#.  Likewise I will be testing Maxcuatro 50# versus Suffix 832 65#.  Same story line with 3 ways to get to a higher diameter.

BTW, I got an eye-opener last fall when I was doing the pre-stretch on a bunch of Spectra lines.  I tied them to a tree then held them with a handle at the other end.  Pulled what I though was a 30-40 pound load and held it while I counted to 100, all the time also wiggling the handle just a little to introduce a bit of a dynamic loading.  The lines felt stretchy.  Then for comparison I tried the same thing with my .018" 7-strands, they felt at least as stretchy.  The next day's flight test confirmed that observation.


In other news I found a few videos of a guy testing breaking strength of various sizes of Maxcuatro. His test device looks good, his results show reasonable repeatability, and his numbers show breaking strengths higher than rated line strength.  When I first found these tests it gave me confidence that Maxcuatro would do the job.  I have no explanation as to why Tom & Mike got much different results than the guy in these videos below.  Maxcuatro was been getting the most discussion here, but he also has tests on other brands. If you are interested, the results he calls "ABS Test" focus on the line independent of any knots.  He also tests the lines when knot to a leader line but that does not apply to us at all:

* Maxcuatro 20# line, broke around 35 lbs, see vid:


* Maxcuatro 30# line, broke around 49 lbs, see vid:


* Maxcuatro 50# line, broke around 58 lbs, see vid:


* Maxcuatro 65# line, broke around 76 lbs, see video:

[Mike Alimov]

It is interesting to see how the same information gets digested and interpreted by different people.
Some think that persistent experiments to find the optimum line brand, type, diameter, knot, etc.  is evidence that we want everyone to switch to a particular type of line at all costs, ignoring the decades of relatively successful experience with the steel line.
Others interpret posted numbers as evidence that we want to shut down the nascent technological trends (Spectra) before giving them a chance to succeed.
As an engineer, I've been trained to look at numbers as just that - numbers, quantitative indicators of some physical property (mass, volume, density, conductivity, tensile strength, etc etc), and leaving any emotions out of the process ("oh look how cool this carbon fiber weave would look on this crockpot lid!" or "I hate anything aluminum"), apply an engineering reasoning process to a decision process while considering all available alternatives.
In this case, Dennis Adamisin has reported a number of performance improvements when switching from 0.018" stainless cable to a 100# Maxcuatro braid (lighter, stiffer, more slippery line, needing less tip weight).  The combat folks have evidence that the line is also durable and more abuse-resistant.  This by itself is good enough for me to invest some time and test for myself.  I went a step further and asked a question, can we achieve yet another benefit of using a thinner line that is still 10G- pull compliant (65#).  The experiments showed that while we will achieve less drag, the added stretch is not worth the trade.
That's all.  Finding an optimal solution through a series of experiments and compromises, using measurements (and not feelings or opinions) as guidance.
  And sharing the results on this forum is just a means of contributing to the stunt community by not making others go through the same expensive and time-consuming path.  This is NOT an attempt to sway or convince anyone to either change anything they've been doing, or to stay with the status quo.   Just as I'm not trying to make anyone stop building balsa airplanes by extolling the virtues of composite technology, or switch combustion aficionados over to electric.  Everyone is entitled to their own preferences.

I have a spool of 100# Maxcuatro on order.

[Jim Svitko]

If the drag of the Spectra lines can be reduced, that would be a big plus for me.  I would have to get some of the newer product, the thinner line but with strength equal to something thicker, and see how that compares to what I experienced in the past regarding the drag issue.

[Dennis Toth]

I really think we need to look at the newer 8 strand braid lines as opposed to the original 4 braid lines. The 8 braid line should be smoother (less drag) and offer a bit of a safety indicator as you can lose a few strands, get a fuzz-up indication of the failure and still have a lot of strength in the line to get down safe. There is also a fused line that I want to learn more about the strength of, which are very smooth but not sure of the strength to diameter on these.

There is a 9 braid line, Berkely X9, that is a 9 braid that seems to be very smooth and strong here is the chart of lines specs: https://www.berkley-fishing.com/products/x9-braid-1486839?variant=34171397275787 the break (https://www.360tuna.com/threads/berkley-x9-20-lbs-crystal-abs-fg-and-pr-knot-test.56204/) at the first part of the video on just the line, the rest is line splices to mono.

There is a very high-end 16 braid line (GOSEN 16) which reported to be the smoothest line made, about 3x the price of the 8 braids but for our use might be worth looking into.

Best,     DennisT

[Brent Williams]

Interesting article comparing 4-strand and 8 strand spectra/dyneema lines.  Sadly, there is no mention of use with control line airplanes...

https://www.sportfishingmag.com/comparing-4-and-8-carrier-braided-fishing-lines/

[GERALD WIMMER]

Hello Some interesting information coming up here, was keen to try Power Pro 'Super Slick' or the 'Fins' 8 strand line but Brent's article at Sportfishing sounds promising particularly :
"Burch believes he might have the next evolution in braid with FINS’ latest nine-carrier 40G product. “The center of the line is Spectra High Tenacity fiber with eight ends of PE wrapped around it,” he says. “Spectra HT is 25 percent stronger and 30 percent smaller than traditional deniers of Spectra fiber. It is the smallest diameter-to-strength ratio we have ever offered.”

I suppose I really need to try out a few new products to see if something beats Maxcautro

Ordered some Fins 40G in blue in 65 and 85 lb will see how this works




Regards Gerald

[Dennis Toth]

I ordered a spool of the FINNS 40G 45LB, should be very strong, smooth and round with the 8 braids. I was wondering if the form of the braid has a significant impact on the line drag through the air. What I mean is the outer bumpiness of the number of braids. It seems that not only does the thickness matter, but the smoothness of the round shape.

I'm thinking that thin is good but thin and closes to what a solid round wire form would be less drag and require less amps to pull the line around. What I would like to get to are lines that are strong enough, light (to allow reduced needed tip weight) and as thin or thinner than if I flew on solid steel (reduce line drag and amps).  It seems there is still work we can do to get better termination that meet our needs which are different then fishing needs.

Best,    DennisT

[Dennis Nunes]

Well I did it! I made my first set of Spectra line using Power Pro Maxcuatro 65 lbs. These lines are for a 39 oz. plane were I currently use .012" x 60' stainless steel lines. The 65 lbs. Spectra lines is an overkill for this size of plane. However, I am more interested in how these lines stretch and did not want to risk my primary plane for testing.

Before making up my set of lines I purchased a couple of items to assist in addition to the Spectra lines. The first item is a Berkley Hot Line Cutter. I purchased mine at https://sportco.com/berkley-hot-line-cutter/ for under $11, including shipping. This uses two AA batteries and heats a retractable wire element that cuts or melts the Spectra line. The benefit of this is that it cauterizes the ends of the lines and keeps them from fraying.

The other item purchased was a portable LED Fish Scale (or Luggage Scale) from eBay for under $10. This scale can handle up to a 100 lbs.

The last item was some Fishing Solid Stainless Steel Ring Connectors (not the split ring connectors) at Walmart. I got 50 of the small size that are rated for 150 lbs. More on this later.

Mike Stinson updated his video on YouTube on how to tie a set of Spectra lines:
 

 
I tied a set of lines with the modified surgeons knot at each end exactly 60' from loop to loop prior to stretching. I then stretched of each line at 50 lbs. for 1-minute using LED fish scale. I did each line twice. BTW, you get a good workout when doing this. I re-measured the lines and to my surprise each line stretched and additional 2 1/2"! Lesson learned: Stretch your lines before using them!

The Berkley Hot Line Cutter works pretty well. It requires that you have some tension on the line that you are cutting. It take a few seconds for the wire element to heat up. Once it heats up it cuts through the Spectra lines like butter. However, be very careful not to get the hot wire element near you main line.

Attaching the lines to the plane I use what are called stainless steel Quick Change Hawaiian Snaps. I attach the Spectra lines using what the StuntHangar Hangout gang has now affectionately called a Lenny Loop, which is nothing more than a "Lark Head" knot and added a 1/4" long piece of surgical tubing over the snap to keep the Spectra line in place. Again look at Mike Stinson's video.

On the handle end I ran into an issue. I use a Cox/Resinger carbon fiber handle with line clips made using the Derek Moran Line Clip Bender tool. The holes in the handle can only pass the single loop end of the clip which leaves the doubled up portion of the line clip to attach the Spectra line to. I didn't have any surgical tubing large enough to pass over the clip to hold the spectra line in place. So for the time being I'm using the solid ring connector to connect to the spectra line and connecting the solid ring connector to the line clip. I plan on switching the connectors on my handle to the "Kitty Clips" that use a spring retainer.

The last thing I did was another 1-minute 50# pull test of everything including, the handle, all connectors and the Spectra lines, everything with except to the plane. The Spectra lines did not stretch any further.

Hopefully, I will get some good weather and put everything is the air. Stay tuned...

Dennis

[Mike Alimov]

I tied a set of lines with the modified surgeons knot at each end exactly 60' from loop to loop prior to stretching. I then stretched of each line at 50 lbs. for 1-minute using LED fish scale. I did each line twice. BTW, you get a good workout when doing this. I re-measured the lines and to my surprise each line stretched and additional 2 1/2"! Lesson learned: Stretch your lines before using them!

[...]

The last thing I did was another 1-minute 50# pull test of everything including, the handle, all connectors and the Spectra lines, everything with except to the plane. The Spectra lines did not stretch any further.

Dennis

Dennis,
I would be curious to see if your lines "shrink back" by the full 2.5" or some fraction of that stretch over time (a week? a month?).  Most polymers have such tendency, and I wouldn't be surprised if Spectra (polyethylene) is not an exception.  2.5" is a significant enough value, because uneven stretching or shrinking between the two lines might cause some serious problems with the neutral setting. I know we fuss sometimes over 1/16" neutral adjustment...

[Brett Buck]

Dennis,
I would be curious to see if your lines "shrink back" by the full 2.5" or some fraction of that stretch over time (a week? a month?).  Most polymers have such tendency, and I wouldn't be surprised if Spectra (polyethylene) is not an exception.  2.5" is a significant enough value, because uneven stretching or shrinking between the two lines might cause some serious problems with the neutral setting. I know we fuss sometimes over 1/16" neutral adjustment...

    Less than that, I routinely adjust by 1/64" or so just depending on how I am feeling the inside/outside turn difference from day to day. It's probably adjusting for something else changing, but handle adjustments are easy and predictable.

     Brett

[Mike Alimov]

    Less than that, I routinely adjust by 1/64" or so just depending on how I am feeling the inside/outside turn difference from day to day. It's probably adjusting for something else changing, but handle adjustments are easy and predictable.

     Brett

OK, agreed, even small neutral adjustments down to 1/64" can be felt. 
At this point, from what little I know about the Spectra braided lines, the issue of stretch memory, or "line length consistency" if you wish, is the most significant issue that threatens to make these lines unusable for us in competition stunt - not the drag, the breaking strength, knot strength, or many other things that have been discussed earlier.
If I can't rely on the lines to maintain their length to, say, 1/64" flight after flight, week after week, then we're back to steel.  I don't know too many competitive flyers who would be willing to put up 6-8 flights to compensate for the ever changing neutral before starting their weekend practice.

This is my thinking at the moment, and is mostly conjecture and speculation. I haven't made "stretch memory" measurements, and given the weather forecast, I may not be able to get to making any measurements for a while, it's just too cold outside.  Guys in warmer climates might get to it before I do...

[Brett Buck]

OK, agreed, even small neutral adjustments down to 1/64" can be felt. 
At this point, from what little I know about the Spectra braided lines, the issue of stretch memory, or "line length consistency" if you wish, is the most significant issue that threatens to make these lines unusable for us in competition stunt - not the drag, the breaking strength, knot strength, or many other things that have been discussed earlier.

    I am certainly not arguing with you, it is very interesting (as has been the rest of this most excellent thread). I have flown 3 flights with Spectra, all on the Skyray, so that is nearly nothing.

      Brett

[Brent Williams]

I'm more interested in the range of expected stretch at typical flight loads, not 10x. 

[Dan McEntee]

I'm more interested in the range of expected stretch at typical flight loads, not 10x.

   Yeas, I'm watching this thread with interest also. I have bought some line with the intent to just use it on my "foo foo" fun fly airplanes and some small models.  Just so I  don't have to worry about messing up a set of steel lines as what they cost now. It makes sense for just fun flying. I'll keep with steel lines for competition airplanes for now. I have been doing far more fun flying than contest flying the last several years.
   Type at you later,
     Dan McEntee

[Brett Buck]

I'm more interested in the range of expected stretch at typical flight loads, not 10x.

   At 10G, you would get similar elongation on .018 7-strand.

   Brett

[Dan McEntee]

   At 10G, you would get similar elongation on .018 7-strand.

   Brett

   But does it stay? I have never checked that. On an initial pull test to "set" a new set of lines, I would expect some sort of change, but I have never measured. I can feel they stretch a bit like a spring action, but never did think much of it.
  Type at you later,
   Dan McEntee

[Brett Buck]

   But does it stay? I have never checked that. On an initial pull test to "set" a new set of lines, I would expect some sort of change, but I have never measured. I can feel they stretch a bit like a spring action, but never did think much of it.
  Type at you later,
   Dan McEntee

   No, it goes back (for the most part). But if you are interested in it relaxing between uses, you might have an issue.

      Brett

[katana]

should be very strong, smooth and round with the 8 braids. I was wondering if the form of the braid has a significant impact on the line drag through the air. What I mean is the outer bumpiness of the number of braids. It seems that not only does the thickness matter, but the smoothness of the round shape.

Interesting point although a non-smooth surface can be often less draggy than a smooth one! Compare a dimpled golf ball against a smooth one - the former flies further with a better flight profile compared to the latter! Think of full-on, glossy paint against the semi matt versions seen on recent F1 race cars - it was found the latter experience significantly less drag when compared. It goes against 'common sense' but boundary effect on un-smooth surfaces can be a thing to consider as maybe a benefit not a hindrance?

[John Park]

   At 10G, you would get similar elongation on .018 7-strand.

   Brett

Even the tinned 3-strand 'Laystrate'-type lines in common use in England have a noticeable stretch on a 10G pull test.

[Ken Culbertson]

Interesting point although a non-smooth surface can be often less draggy than a smooth one!

Hold that thought, this is the wrong thread but finally!  I have been trying to convince folks for as long as I can remember that my planes fly better with a matt finish than they do buffed.  I started a new thread so this one doesn't get hijacked.

Ken

[Dennis Adamisin]

Dennis N - THANKS for sharing your line stretch results you proved the need for pre-stretching! I am even going to buy a pull scale so I can do a better job of controlled pre-stretch than I have in the past. Being lazy, the one thing I might change is to connect the lines end to end and pull them at the same time to assure exactly the same load - in half the amount of time!

From what I have heard the Combat guys do the stretching ONCE then forget about it.  However, Mike Alimov raised the point about polymer "memory" (stretching then reverting), but I wonder if at least part of the effect of stretching is simply to align the strands and tighten the weave of the braid?  Also if Mike is right then we made want to periodically repeat the stretching exercise to correct whatever the amount of stretch is caused by polymer material stretch?

I know SS cables & even solid lines stretch, can't help thinking that we SHOULD have been pre-stretching SS cables all along.

In those line strength videos I posted (reply #59) I noticed that the tester first loaded the line to around 50% then held it for a few seconds, before continuing to load the line to failure.  I suspect that the tester was letting the weave tighten up as the strands got aligned - which probably improved the ultimate failure point.  Similarly, I wonder if when knotting the line it is possible to inadvertently get more tension on one or two strands, causing them to fail first, even if it is away from the knot, with that failure cascading across the remaining strands?  If so then pre-stretching & holding the load (per Dennis N) should help the strands align and increase breaking strength.  Note: this might also explain some of the tests that show line breaking below its rated strength?


I am past deciding whether I will use Spectra, and expect that concerns with stretchiness will be answered over a couple sessions at the flying field.  My biggest concern before flying season will be removing all the built in tip weight I have pre-installed. I do this so I can use the tip weight box for fine tuning.  However, I cannot remove enough from most of the fleet!  Those airplanes with large asymmetry (Classics & OTS) may need INBOARD tip weight boxes..!

[Ken Culbertson]

I am not positive how many wraps our lines get during the course of a pattern.  I do know that, depending on how you do the Reverse Wingover you end up with three.  The wrapping causes friction and ware on the lines.  On the Ukranian lines you can see that ware as a slight dulling after 10 or so flights.   I haven't used Spectra enough with the same line to know how it reacts and if the effect on controls is any different.  Just how far from the plane the wrap occurs may also be quite different.

Brave new world - Ken

[Dennis Nunes]

Dennis,
I would be curious to see if your lines "shrink back" by the full 2.5" or some fraction of that stretch over time (a week? a month?).  Most polymers have such tendency, and I wouldn't be surprised if Spectra (polyethylene) is not an exception.  2.5" is a significant enough value, because uneven stretching or shrinking between the two lines might cause some serious problems with the neutral setting. I know we fuss sometimes over 1/16" neutral adjustment...

Hi Mike,
I re-measured my lines today, 24 hours after the initial stretch, and the 2 1/2" increase in line length remained the same. It's difficult to "accurately" determine how much these lines either increased or decreased in length. I'm trying to maintain the same amount of tension on the lines with each measurement but it could be off 1/8" or so either way and who knows what my 100' steel tape measure is doing. But it definitely *did not* shrink back the full 2 1/2"! I'll measure again in a week or so and see if there are any significant change.

Dennis

[Jim Svitko]

Pre-stretching the Spectra is something I never did, at least not with that as the primary purpose.  All I ever did with Spectra or stranded steel is to proof load them to the pull test load after making up the line set.  That is, each line was pulled to 1/2 of the 10G requirement.  Maybe the proof loading produced the necessary pre-stretch.

I never went back to measure the Spectra after I did my proof test to see if the lines remained stretched.  For that matter, I never did it with the stranded steel lines, either.

On the stranded steel lines, I could certainly notice the stretch and when the load was removed, the lines went back to what I assume was original length.    I would expect that to be true as long as I did not exceed the yield point of the material.  I have not messed with Spectra for quite some time and I can't remember if it behaved like the steel lines after proof loading.

[Larry Wong]

Hi Mike,
I re-measured my lines today, 24 hours after the initial stretch, and the 2 1/2" increase in line length remained the same. It's difficult to "accurately" determine how much these lines either increased or decreased in length. I'm trying to maintain the same amount of tension on the lines with each measurement but it could be off 1/8" or so either way and who knows what my 100' steel tape measure is doing. But it definitely *did not* shrink back the full 2 1/2"! I'll measure again in a week or so and see if there are any significant change.

Dennis

.  Dennis are you sure that the line stretch? or is it the knot tighten ?

[Dennis Nunes]

.  Dennis are you sure that the line stretch? or is it the knot tighten ?

No the knots were tight, it was the line.

Dennis


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[Dennis Toth]

OK, found some very interesting information about knot strength and how it affects the breaking strength of the braid line. The weakness of our uses of Spectra is having confidence in the selecting the proper LB test line and not overkill. With good knots we can go closer to 10X the model weight for the LB test line and likely have thinner lines.

Here is the site: https://www.knotsforfishing.com/strongest-braid-knots/

Scroll down and it has link to each type of knot. Now we need to figure out which of the 100% plus knots to use. The "Burke Knot" on the list just a double Uni knot that AMA recommends.

Best,    DennisT

[Brent Williams]

OK, found some very interesting information about knot strength and how it affects the breaking strength of the braid line. The weakness of our uses of Spectra is having confidence in the selecting the proper LB test line and not overkill. With good knots we can go closer to 10X the model weight for the LB test line and likely have thinner lines.

Here is the site: https://www.knotsforfishing.com/strongest-braid-knots/

Scroll down and it has link to each type of knot. Now we need to figure out which of the 100% plus knots to use. The "Burke Knot" on the list just a double Uni knot that AMA recommends.

Best,    DennisT

For me, line strength and knot strength are lesser of a determinant than the line stretch characteristics in use.  Much like flying a 60oz piped ship on .012 or .015. stainless stranded lines.  Yes, you can, but the flight performance will suffer greatly compared to a line material or diameter that exhibits less elasticity.  So, yes, you could probably safely use 40lb spectra with a 100% strength knot on a big plane, but the performance aspect would likely suffer compared to 80-100lb line on a big stunt ship.

Is there a problem with the knot the combat guys have tested, vetted and widely used for a decade? 

[phil c]

I have been doing a bunch of reading on this.  Mostly from the Kite flyers.  One problem seems to be fake line.  Seems some of the Chinese stuff actually comes in identical packaging as the real.  Is there a surefire way to know you are not getting the fake line?   

Secondly, since my decision matrix is between Spectra and the Ukraine lines, has anybody done a stretch comparison between the two?   My anecdotal experience is that spectra stretches more but the literature says less.  It also seems to have more rake but, my ability to do my usual video analysis is grounded.   Anybody have any thoughts?

It is hard to pass on something that is lighter, thinner and 15 times stronger but putting your pride and joy out there in a 15mph wind on fishing line sort of bothers me still.  Help me get over it!

Ken 

I posted up above,  at the NATS I used an "official" pull tester Bob and Andy Mears built.  Anyway brass plated, 4 strand Ukrainian lines managed the 44lb. pull test and stretched 2-1/4 inches.  The braided, .175 Australian line, from around 1993 pull-tested fine and stretched 2-1/4 inches.  One really nifty feature, for combat, in a line tangle the metall lines lock up with one wrap.  The rough surface can't slide until the Spectra line unwraps.

The braided line does bow more which generally isn't a problem as long as the LO guide and sweep is allowed for.

[phil c]

We seem to be getting into analysis paralysis talking about the stretch of the lines. Most people doing stretch tests have been using a pull of several times what would normally be expected from a stunt ship. Most ships pull less than 8 lbs. at the speeds we fly. The other thing to consider is that this load is applied over two lines, so the actual line area is double. If you are looking for an excuse not to use Spectra lines you can say they stretch too much at 10x the model weight, that's OK. But in reality, at normal flying pull, it is not a real issue.

The lighter weight, durability and thinner diameter on the newer smooth 8 braid Spectra lines will reduce line load and can help reduce fuel/amps needed, which in turn reduces model weight. Seems we need to be looking to find the brands with the most strength, least stretch and strongest, most reliable termination rather than worrying about a non-critical issue.

Best,   DennisT

It's a good idea, but not absolutely required to stretch Spectra lines to set the braid or twist.  About 50% of the listed pull test on the package usually is enough.

[pmackenzie]

I posted up above,  at the NATS I used an "official" pull tester Bob and Andy Mears built.  Anyway brass plated, 4 strand Ukrainian lines managed the 44lb. pull test and stretched 2-1/4 inches.  The braided, .175 Australian line, from around 1993 pull-tested fine and stretched 2-1/4 inches.  One really nifty feature, for combat, in a line tangle the metall lines lock up with one wrap.  The rough surface can't slide until the Spectra line unwraps.

The braided line does bow more which generally isn't a problem as long as the LO guide and sweep is allowed for.

Was the line lying on the ground the whole time during the pull test, or suspended?
If the latter, then a lot of that observed "stretch" could just be the catenary curve moving up under tension.

I make up F2D lines to the correct length with zero pull, laying on the ground. If they actually stretched  2-1/4" during a pull test, I probably would have seen it at some point since the length tolerance is less than that.

[Reptoid]

  "One really nifty feature, for combat, in a line tangle the metal lines lock up with one wrap.  The rough surface can't slide until the Spectra line unwraps."

You think that's "nifty"
 
That's why they aren't legal in F2D and a mix of synthetic vs metal should never be allowed in competition. Two reasons; Metal lines tend to lock up in a tangle but: if the planes fly with tension for more than a few seconds while tangled the spectra lines will fail. I have seen it multiple times.

Ask yourself why fishermen going after tough fighting fish use the synthetic line but use a braided steel leader. Answer, it sucks under abrasion or sharp object encounters.

[Dennis Toth]

I like Mike Stinson's video on tying the knots, seems to make it fairly easy to get the line length correct enough. The knot looks like it does not over stress the line when tightening and can hold up to the rated LB test of the line, all good. One thing I would like to see if Mike could show how he gets the clip loop knot very close to the clip. I don't like the loop being able to slide around on the clip as I feel this will be a wear point. If it is tight up against the clip it could bent but not slide would seem to be a one less wear failure point of worry about.

The point raised by Katana about the dimples on golf balls is interesting. It makes sense that the super smooth lines may not be the least drag. Seems we need to do a flight test of both types side by side.

Best,     DennisT

[Dennis Nunes]

One thing I would like to see if Mike could show how he gets the clip loop knot very close to the clip. I don't like the loop being able to slide around on the clip as I feel this will be a wear point. If it is tight up against the clip it could bent but not slide would seem to be a one less wear failure point of worry about.

Hi Dennis,
One of the methods for attaching the Spectra lines to the line clip when using the modified surgeon's knot is a "Lark's Head" knot or what the StuntHanger Hangout Group calls a "Lenny Loop". This can help hold the line in place and is stronger than just using just the two loops.

The combat guys have been using Spectra lines for several years and apparently like them. But the expectant life span of a combat plane, in most cases, is relatively short lived when compared to a stunt ship. I'm curious, how often do combat flyers replace their Spectra lines if there not involved in an incidence?

Dennis

[Dennis Toth]

I tried Dennis N's suggestion to use the Larks Head to attach the scissor line clip to the Spectra with the double Surgeons termination, it works great!! Solved my concern about the line moving around on the clip.

The Larks Head is used by the Kite flyers and is simple to apply. Simply take the double loop created by the double Surgeons knot (MS illustrated in his video), pass it though the line clip (you could go around twice if you have a big loop) and bring it under around the bottom of the line clip. Then open the loops and pass the end through the loops and up over and around the clip, pull tight and BAMB it is cinched down. This secures the line and neither stress the Spectra as they are formed.

Thanks for the suggestion Dennis N.

Best,     DennisT 

[Brent Williams]

The combat guys have been using Spectra lines for several years and apparently like them. But the expectant life span of a combat plane, in most cases, is relatively short lived when compared to a stunt ship. I'm curious, how often do combat flyers replace their Spectra lines if there not involved in an incidence?

Dennis

Mike Londke, Phil Cartier and other users report that generally, combat fliers replace thier Spectra lines annually as a matter of seasonal maintenance or combat readiness.  The primary reason for the annual replacement of the Spectra lines is because many of those combat guys attach the lines directly to the bellcrank.  This arrangement causes very localized wear on the Spectra line material as it constantly rubs on the leadout guides.  The wear pattern is described as fluffing, fuzzing or fraying. 

This type of wear is simply something that does not occur on a stunt plane with traditional leadouts.  I do not believe annual Spectra line replacement is necessary for Stunt use.  As with any of the metal line materials in use, inspect your lines often and replace as needed.

[Mike Alimov]

I was able to sneak out at lunch today and take advantage of a "balmy" 40-degree day to make some more measurements, now adding the newly arrived 100# Maxcuatro into the mix.  First I measured "virgin" line elongation, i.e. the line as it just comes from the factory spool, with no previous load applied.  Then, using the knowledge gained from Dennis Nunes' experiments, I added the procedure I will refer to as "conditioning", which involves applying progressive load up to 30 lbs, and holding this load for 1 minute, repeated two times, which sets all the knots and stretches the lines.  The lines do indeed stretch out some, in my case about 1.25".  I did not want to apply more than 30lbs of conditioning tension because I expect that if lines are stressed to 80-90% of the rated breaking strength, two things can happen: knots will fail, and/or the line will relax somewhat, changing the elongation properties and rendering original results useless.
I also discovered a mistake in my earlier reported measurement, so the new set of corrected numbers is here:

Brass plated 4-strand (Ukrainian) 0.0165" elongation 0.5%
Stainless 7-strand 0.018" elongation 0.41%
Stainless 7-strand 0.015" elongation 0.63%
"Virgin" Maxcuatro 65# elongation 0.79%
"Conditioned" Maxcuatro 65# elongation 0.65%
"Virgin" Maxcuatro 100# elongation 0.55%
"Conditioned" Maxcuatro 100# elongation 0.45%

(While I haven't tested it, I expect 80# Maxcuatro to fall somewhere in between 65# and 100# results).

Preliminary conclusions:
- after "conditioning" and with properly terminated ends, Maxcuatro lines with ratings from 65# to 100# will comfortably pass 10G pull tests for planes in the 55 - 65 oz range, with a 2X-3X safety margin;
- after "conditioning", Maxcuatro 65# line is expected to give about the same stretch feel as a 7-strand stainless 0.015" cable, and has comparable diameter;
- after "conditioning", Maxcuatro 100# line is expected to give the stretch feel between a 7-strand stainless 0.018" cable and a 4-strand  0.0165" cable, and has comparable diameter to 0.018" cable;

So far, the only performance advantage over the steel lines is smaller weight of the Spectra lines; the rest of the advantages fall into the usability category: kink resistant, hydrofobic, easy to see, etc.  The ability to control after 40 loops and come out of a line tangle without damage are not of interest to us for stunt application.

What remains unanswered is to what degree will Spectra-based lines maintain their length, and their elongation properties, over time as well as under different environmental conditions.
Specifically, here are the example scenarios that worry me:

- A user stretch-conditions his lines, performs a few trimming flights to dial in the neutral, and starts practicing; then a month later he goes to a contest, where a contest official performs a 10G line pull; somehow one of the lines stretches a little more than the other - but the user is unaware, until he goes into official flight, and is unable to deliver his best results due to the neutral being off;

- At a contest, a user passes the 10G pull test, performs the first flight of the day, and then puts down the lines on a hot tarmac to wait for the second round flight; the heat shrinks one of the two lines a little more than the other - once again, the neutral trim is lost, and a good flight cannot be performed.

The time and temperature study is difficult to do by using measurements: as Dennis N. noted, how do you accurately and repeatably measure a length of nearly 70' down to 1/64" accuracy (or better) over the course of days, weeks, and months?  Of course this could be done by someone with a very keen sense of neutral, flying a plane with the same set of lines and same handle over a long period of time, but I'm not one of them - my neutral can be off by 1/8" and I'm still OK with it.

As of today, I'm still on the fence about adopting these lines.

[Dennis Nunes]

Very good information Mike. Hopefully I will get to test the 80# Maxcuatro lines this Saturday to see how they perform. However, my test will be performed on a plane that only weights 39 oz. The 80# Maxcuatro line I believe is an overkill for this size plane. Currently, I use.012" x 60 7-strand stainless steel lines. For the first flight I plan on flying the plane with the stainless steel lines and then the very next flight switch over to the Maxcuatro lines and see if there is a difference. One of the things I'm curious about is if the 80# lines are too large and how much it effects the performance. Will see...

One of my concerns is when we "condition" a set of lines, how much will the break point of the line drop. I'm no Structural Engineer (but I can play one on TV ). I would think that as a result of conditioning, the break point of the line is lowered. How much is what I'm concerned with.

Dennis

[Mike Alimov]

One of my concerns is when we "condition" a set of lines, how much will the break point of the line drop.

Dennis

Based on a few destructive tests that Gabe ran on the 100# Maxcuatro last night, the breaking strength is actually increased after "conditioning".  I'm not ready to report by how much, but it definitely doesn't deteriorate.
I'm no longer discussing the breaking strength as part of our tests because at 4X-5X margin, does it really matter?  We are using 80-100 lb line to withstand a 20 lb pull test and a 5 lb normal flight load.

[Dennis Toth]

Tried Mike S knot and found that if you take a very thick piece of twine to practice with it is much easier to get the hang of which way the bite loops are pushed through the initial loop. Once you do it with the twine you can do the fine line. Got half a set done will complete tomorrow.

Best,   DennisT

[Dennis Adamisin]

Based on my still limited experience with Spectra, and after a thorough analysis of the test results posted here and other online sources, I have narrowed my new line purchase to the single best line for a particular airplane of mine.  The airplane and the line in question are shown below:

(eat your hearts out)


Seriously folks, read through the posts in this threads, I think it is pretty easy to pick/choose a line for your own trials and your own in-flight prove-out...  Choose your line, tie it as indicated above, condition the line by pull testing to 50% load for 1 minute, and fly it.  I suggest you fly with an old familiar airplane on cables first then switch the next flight.  If you like it try it on the rest of your fleet...