My Unscientific Spectra Test

batjac Sun Sep 25, 2016 8:59 pm

Well, since a question about the AMA’s numbers for Spectra was brought up in my other post, I figured I’d do a highly unscientific test of the Spectra I have on hand. In the AMA Control Line General Rules handbook, Spectra is good for sport flying at:

20 Lb Test - .09 or 300 Watt aircraft weighing up to 24 ounces
40 Lb Test - .25 or 450 Watt aircraft weighing up to 40 ounces
60 Lb Test - .40 or 600 Watt aircraft weighing up to 60 ounces

I have 10#, 20#, 30#, 50# and 65# test Spectra, Power Pro brand by Shimano. Since these are just for sport flying, I decided to just do the 10G test of each weight. The AMA manual doesn’t list 1/2A test, but I usually use 10# test for my .049s, and my 1/2A models usually top out at around 7 ounces, so I used 10 ounces for the test weight. My 10G values for each test were as follows:

10 lb test – 10 ounce model – 6.25 pounds pull
20 lb test – 24 ounce model – 15 pounds pull
30 lb test – 30 ounce model – 18.75 pounds pull
50 lb test – 50 ounce model – 31.25 pounds pull
65 lb test – 65 ounce model – 41.65 pounds pull

I have a nifty luggage scale that’ll go that high, but I decided to go old school and just use analog weights. I grabbed my dumbbell handle and some weights to make up the required pull, and a nylon strap to throw over a 1”x6” in the pergola on the back porch. I made up short lengths of control line using the AMA recommended 5-Turn Double Uni knot for each value of Spectra I have. My nifty test rig:

My Unscientific Spectra Test DSCN4938

I decided to hang each length of Spectra from the nylon strap with the weight hanging on the other end for 5 minutes. The 10#, 50#, and 65# all held at my calculated 10G weight. The 20# and 30# test samples failed at the knot. Hmmm…

My Unscientific Spectra Test DSCN4941

I’m going to make up a couple of new test samples of the 20# and 30# using the AMA recommended knot to see if I just messed up the first knots, and a new sample for each using the knots suggested in the pamphlet that comes in the Spectra box.

The Mad Scientist Mark

**Cribbs74** Sun Sep 25, 2016 9:10 pm

Cool test Mark, personally I don't bother with Spectra for anything other than 1/2A. Not that I have issue with Spectra mind you, just like steel cable: I use 8lb test and have never had a problem, apart from a pulled knot on the down line so I just did loops into the headwind until the plane stalled and landed softly in the grass.

I can attest to crappy foreign made Spectra. Not only does it fail it also tangles like crazy.

Looking forward to your future results.

batjac Mon Sep 26, 2016 7:50 pm

Well, the re-rest results were not exactly as I could wish, and not very consistent. I re-tested the 10#, 20#, and 30# lines and added weight until the knot failed. Due to the limits of my weight set, I had to work in 2.5# increments. I used the AMA recommended 5-turn Double-Uni and a Double-Uni as recommended in Shimano’s instructions. The results are as follows.

10# test line – 10G limit is 7.5# pull.
AMA held at 13 pounds, failed at 15.5 pounds after about a minute.
Shimano held at 15.5, failed at 18 pounds after about a minute.

20# test line – 10G limit is 15# pull.
AMA held at 25.5 pounds, failed at 28 pounds immediately.
Shimano held at 18, failed at 20.5 pounds after about a minute.

30# test line – 10G limit is 20# pull.
AMA held at 25.5 pounds, failed at 28 pounds after about a minute.
Shimano held at 23, failed at 25.5 pounds after about a minute.

So, all three tested weights passed the 10G test, and the 10# and 20# failed above their rated loads. The 30# did not meet its rated load. The variability in the results I would put down to my knot tying ability, as one knot failed low, I re-tied it on the same sample length, and it was good for another 5 pounds. I’m not sure exactly how I’m tying them differently, but I’ll be more careful in the future on all my knots.

The Inconsistent Mark

pkrankow Mon Sep 26, 2016 9:21 pm

Are you moistening the knots to tighten them? Are the wraps even or are there "overwraps" Yes tying small line well is difficult.

Phil

**Cribbs74** Mon Sep 26, 2016 9:54 pm

Interesting results. While not totally scientific, I think it was a pretty good test. I also think during normal flying/stunting the lines will hold just fine. My concern is when you get blown out of manouvers, you get a healthy pull when the tension hits and it would really test the line and the knots for that matter. Still going to stick to cables. Cool

OTOH if you doubled your line test theoretically it would never be a problem and all you would have to worry about is your knot tying skills.

Ron

Oldenginerod Mon Sep 26, 2016 10:14 pm

Here's a good video on tying the knot mentioned. Makes it look easy enough.

batjac Tue Sep 27, 2016 12:30 am

Phil, yes, I moisten the lines before pulling the bight. The line wraps are pretty straight. I'll just work on uniformity in the future.

Rod, that's the knot that the AMA endorses. In the video you see the bight passed through the eyelet once and then the knot tied. The Shimano instructions have you run the bight through the eyelet twice before making your loop and five wraps. From my experiment above, I can't say that one is better than the other. But in the future I think I'll go the Shimano route and pass the bight through the eyelet twice before knotting it.

The Reformed Mark

londke3 Tue Sep 27, 2016 9:48 am

The modified surgeons knot works much better. There are extensive posts and pictures of it over on Stunt Hangar. I can't seem to copy and paste a pic of it so you'll have to look at SH.

londke3 Tue Sep 27, 2016 9:51 am

Try this, I use 100lb PowerPro on Speed Limit and Fast combat planes and have never had a knot slip or break. http://wp-files.bdoutdoors.com/wp-content/uploads/2015/05/surgeons_loop.jpg

batjac Fri Oct 14, 2016 12:21 pm

londke3 wrote:Try this, I use 100lb PowerPro on Speed Limit and Fast combat planes and have never had a knot slip or break. http://wp-files.bdoutdoors.com/wp-content/uploads/2015/05/surgeons_loop.jpg

I've never tried a Surgeon's Knot, but I don't see it as a knot I would use. There's no good way to do it and have the line snug against the split ring that I use to connect to the line clips. I wouldn't want to fly with that big old loop just waiting to get a tangle.

Can you show me a picture of how the knot looks on your planes?

The Opinionated Mark

getback Sat Oct 15, 2016 7:35 am

Mark if i remember right it was Mike that turned me on to this Knot , i have it for reference on my desttop http://www.animatedknots.com/palomar/index.php?Categ=fishing&LogoImage=LogoGrog.png&Website=www.animatedknots.com#ScrollPoint

batjac Sat Oct 15, 2016 6:27 pm

Cool website! Bookmarked!

The Archival Mark

londke3 Sun Oct 16, 2016 8:57 pm

batjac wrote:
londke3 wrote:Try this, I use 100lb PowerPro on Speed Limit and Fast combat planes and have never had a knot slip or break. http://wp-files.bdoutdoors.com/wp-content/uploads/2015/05/surgeons_loop.jpg

I've never tried a Surgeon's Knot, but I don't see it as a knot I would use. There's no good way to do it and have the line snug against the split ring that I use to connect to the line clips. I wouldn't want to fly with that big old loop just waiting to get a tangle.

Can you show me a picture of how the knot looks on your planes?

The Opinionated Mark

What is a split ring? Do you mean eyelets? Post a pic please. As for "the big old loop" it can be made quite small with practice. Additionally no "split ring" or eyelet is necessary. You hook the line connector directly to the loop. I'm quite sure if I can fly them on a Nelson .36 going 130mph that they are suitable for most any sport flying. This knot has been used for YEARS in the combat world and believe me if it didn't work we would all know it and NO ONE would use it.

sws200 Tue Nov 15, 2016 7:56 am

I have just started using the spectra line for 1/2A... I am liking it. after reading test results... it occurred to me that when we pull test... we have both lines connected... so the load is over both lines equally... (Hopefully)... so the capacity should be somewhere around 2X the test results?

My biggest problem has been getting equal line lengths. I am using my old hot rock handle with 2 lines. I have thought about making a new handle for 1/2A to use a single line that can be adjusted on the handle. 1 70' line rather than 2 35' lines... anybody else done this?

londke3 Tue Nov 15, 2016 8:33 am

sws200 wrote:I have just started using the spectra line for 1/2A... I am liking it. after reading test results... it occurred to me that when we pull test... we have both lines connected... so the load is over both lines equally... (Hopefully)... so the capacity should be somewhere around 2X the test results?

My biggest problem has been getting equal line lengths. I am using my old hot rock handle with 2 lines. I have thought about making a new handle for 1/2A to use a single line that can be adjusted on the handle. 1 70' line rather than 2 35' lines... anybody else done this?

Yes, this is exactly what I use for 1/2A combat. Small wooden handle with the line passing across the back. I route out a channel for it, put a notch in the center and then use a small screw with a smooth shoulder on it. Take a few wraps on the up line and a few on the down line and secure it with a rubber band. Let me see if I can post a pic.

londke3 Tue Nov 15, 2016 8:54 am

https://www.youtube.com/watch?v=Rd2zLTo5SVw

sws200 Tue Nov 15, 2016 10:53 am

I think I will build some handles like yours... they look great... I like the notches so you can wrap the lines

thanks

steve

roddie Tue Nov 15, 2016 3:10 pm

londke3 wrote:https://www.youtube.com/watch?v=Rd2zLTo5SVw

Nice little handles Mike. I like them a LOT! Are the antenna-tubes glued-into the handle?

An option to a rubber-band safety at the adjustment-post.. might be found in a small rubber grommet.

My Unscientific Spectra Test Adj-po10

I suppose it would be easy to loose too.. unless a short lanyard string was attached to it. Easier to install though.. and easier to remove as well.

I too have trouble tying two separate lines reasonably the same length.. and want to make some single line-thru 1/2A handles for synthetic braid. I like your handle and the antenna-tube approach.. but I think that forming a smooth "U" transition-radius somehow.. or at least breaking (rounding) the corners inside the groove with a rat-tail file would lessen the chance of line-fatigue in those areas. I wonder if the tubes could be fluted on the handle's groove end (by heating) might provide somewhat of a radius.. rather than a sharp corner? Perhaps you've applied that. I watched the vid.. but it's hard to see those particular areas.

batjac Tue Nov 15, 2016 5:09 pm

sws200 wrote:I have just started using the spectra line for 1/2A... I am liking it. after reading test results... it occurred to me that when we pull test... we have both lines connected... so the load is over both lines equally... (Hopefully)... so the capacity should be somewhere around 2X the test results?

My biggest problem has been getting equal line lengths. I am using my old hot rock handle with 2 lines. I have thought about making a new handle for 1/2A to use a single line that can be adjusted on the handle. 1 70' line rather than 2 35' lines... anybody else done this?

During normal flight, yes, each line carries half of the load. But 1) with full deflection up or down, one line would be carrying the full load. And 2) if one line failed, the other line would then be carrying the full load, until the plane crashed, or you did loops until the fuel ran out.

I have also made wood handles of various types/sizes out of wood for 1/2A models. Now I mostly just use SIG handles pre-loaded with 25', 30', 35', and 42' lines. Each has line clips that attach to split rings at the plane.

The Loaded Mark

londke3 Tue Nov 15, 2016 9:58 pm

What the hell is a split ring please????? I asked before and it went unanswered. Please explain to all of us what a split ring is
and how it is used on control line model airplanes. Post a pic. or use a term that is well known in the CL world. Surely this will go unanswered as my last query to you did.

batjac Wed Nov 16, 2016 1:03 am

londke3 wrote:What the hell is a split ring please????? I asked before and it went unanswered. If you are going to chime in on this post please explain to all of us what a split ring is
and how it is used on control line model airplanes. Post a pic. or use a term that is well known in the CL world. Surely this will go unanswered as my last query to you did, You sign off as the "BLAGH BLAGH BLAGH MARK" Please enlighten me as to all your awesome control line tips.

I apologize if I've wasted your time or bored you. I'm sure you do not need me to enlighten you. A simple Google search for split rings would surely be more enlightening than any of my "awesome" tips.

The BLAGH BLAGH BLAGH Mark

BTW: if it's too much effort for you to Google split rings, you can just look at the photos in the first post and see split rings on both ends of all of the test pieces. BLAGH BLAGH BLAGH.

getback Wed Nov 16, 2016 1:05 am

but smaller for 1/2 A

londke3 Wed Nov 16, 2016 8:26 am

getback wrote: but smaller for 1/2 A

Now that I see what Mark is using I can't tell you enough what a bad idea using those rings for connectors is. I've seen it firsthand. I warned a guy that they would open up if he lost line tension and regained it. That is exactly what happened. The airplane became a freeflight model. Why on earth would anyone use these when there are purpose built connectors for control line models? It's just asking for trouble. Using these is bad advice and I suggest anyone using them stop immediately.

londke3 Wed Nov 16, 2016 8:31 am

roddie wrote:
londke3 wrote:https://www.youtube.com/watch?v=Rd2zLTo5SVw

Nice little handles Mike. I like them a LOT! Are the antenna-tubes glued-into the handle?

An option to a rubber-band safety at the adjustment-post.. might be found in a small rubber grommet.

I suppose it would be easy to loose too.. unless a short lanyard string was attached to it. Easier to install though.. and easier to remove as well.

I too have trouble tying two separate lines reasonably the same length.. and want to make some single line-thru 1/2A handles for synthetic braid. I like your handle and the antenna-tube approach.. but I think that forming a smooth "U" transition-radius somehow.. or at least breaking (rounding) the corners inside the groove with a rat-tail file would lessen the chance of line-fatigue in those areas. I wonder if the tubes could be fluted on the handle's groove end (by heating) might provide somewhat of a radius.. rather than a sharp corner? Perhaps you've applied that. I watched the vid.. but it's hard to see those particular areas.

I think the grommet may work well if you can squeeze it enough to keep it from slipping. And yes I do round out the corners in the handle. A little light sanding with a dremel does the trick. I'll bet you could heat the tubing and get it to keep a radius. Good idea. Yes the antenna tubes are glued to the handle with a dab of epoxy.

fredvon4 Wed Nov 16, 2016 10:07 am

Not intending to be argumentative Mike L but if you go to first post and first photo and see the split rings referred to, and understand this is light 1/2a sport (not combat) use.

I have never used them as shown but have many Eagle claw # 5 split rings in my fishing tackle box. About the smallest I can open with my fat old fingers. I have had strike and line spin out 30 to 50 yards, go slack, and reel like hell before the sudden rod bending in half new fish direction...eventually landing the 40+ pound Salmon. I have had every kind of tackle breakage, but never saw a 3 turn "split" ring open up

I hear what you are saying and do not dispute your observation...BUT I would not hesitate one bit to use my # 5 split rings with Spider wire 1/2a lines

But then hey I still have a set of dacron lines with swivel snaps to fly one of my 049 plastic models...OH the sacrilege!

I can already hear the "never ever use fishing tackle Snap swivels!" hew n cry
And it is indeed great advice, no doubt about it

On the other hand, if that anemic, never could do a loop, air plane ever had the notion to pull hard enough to break one (snap swivel) I would grin my arse off as it zoomed for the trees... And I would probably leave the sucker there

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My Unscientific Spectra Test

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testing one line

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your handles look great

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