ADVENTURES IN SPECTRA

[Dennis Adamisin]

No kidding!  Now that you mention it, I think the plane was fishtailing where it should have been locking.  I blew that off as crappy piloting having not flown in a month or so.  Thanks for giving me an excuse to blame the plane!  Next time out I will divest it of some tip weight and add a few RPM's to keep the lines tight.  Funny you should mention rudder.   It has a cam for just the reason you stated.  Best whisper (shhh), because admitting to using rudder might get you cancelled. 

I was quite proud of how this profile flies.  It appears to fly like a real PA, but after a few months flying the canard, I was shocked at the difference in turning.  My first pullout on the RWO caused several worms to have heart attacks.

Ken

Ken
Switching to Spectra of course required at least a little re-trimming on existing airplanes. Not stopping there, whenever I pick up something haven't flown for awhile I end up with some kind of trim tweak to get a little  better feel, a little better performance.  Works both ways too; go back to the main bird and as often as not I'll get another idea to try to squeeze a little more out of it too!

[Ara Dedekian]

      Used my 100# dark green Spectra to lash the brass hinge barrels to the elevator of a well used, unknown combat plane destined for Brodaks. It looks suspiciously like Phil's Rugged Stunt Trainer modified from its former life to fly combat.

      Ara

[kiwibrit]

I am trying out my first set of Spectra type lines (actually Shimano Kairiki).  Pre stretching went fine.  I have used the modified surgeons knot to form the loops. Very pleased that my 60' lines are of identical length (beginners luck)? and just 1/4" short of the intended 60' length.

Question: do the free ends of line have to be sealed?  In his video, Mike didn't seal his.  I attempted to seal the ends using the flame from a match - but it didn't work well, and I have fraying as far as the knot.  My guess is that it can't go further, since the knot itself will stop any further progression, so all is well.  But I would be grateful if experienced users can confirm.

[Colin McRae]

I am trying out my first set of Spectra type lines (actually Shimano Kairiki).  Pre stretching went fine.  I have used the modified surgeons knot to form the loops. Very pleased that my 60' lines are of identical length (beginners luck)? and just 1/4" short of the intended 60' length.

Question: do the free ends of line have to be sealed?  In his video, Mike didn't seal his.  I attempted to seal the ends using the flame from a match - but it didn't work well, and I have fraying as far as the knot.  My guess is that it can't go further, since the knot itself will stop any further progression, so all is well.  But I would be grateful if experienced users can confirm.

I have never 'sealed' the free ends. Never had any issues.

[Dennis Nunes]

Question: do the free ends of line have to be sealed?  In his video, Mike didn't seal his.  I attempted to seal the ends using the flame from a match - but it didn't work well, and I have fraying as far as the knot.  My guess is that it can't go further, since the knot itself will stop any further progression, so all is well.  But I would be grateful if experienced users can confirm.

I've had some ends fray. I've used a Berkley Hot Line Cutter. I purchased mine at https://sportco.com/berkley-hot-line-cutter/ for under $12. This cutter 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.

Dennis

[Colin McRae]

I have various sets of Spectra lines that have many flights on them. Mine were cut with a simple wire cutter.

The free ends on mine are around 3/8" long away from the knot and show no signs of fraying. I have only used the PowerPro brand. Maybe the brand used has something do with possible fraying.

[kiwibrit]

Dennis Nunes, thanks.  That looks a very practical solution - I'll buy one.

Colin McRae, thanks.  I'll try Spectra next reel - I have started with Shimano Kairiki because my first flights with this sort of line were with it - courtesy of a kind New Zealand modeller who let me fly a couple of his models ... and I was impressed. I think using a hot wire cutter is a good idea and will probably use it on all future line sets I make with Spectra type line.

Meantime, I shall use the lines I have made up.  The knots are so tight, I don't think there will be trouble, but I shall do frequent line pull checks.

[Dan McEntee]

   I am on my second season of learning and flying with Spectra lines. So far, the biggest improvement I have seen on the airplanes I have tried it on, is vertical and overhead maneuvers have better tension and feel. I pretty much use the knot that Mike Stinson shows in the video, with a single loop for small models and a double loop for larger airplanes. The experiment continues.

    But I'll have to ask the question I have been looking for some one else to ask !! Has there been any kind of failures by anyone?? Just curious. After doing something one way for so many years, it's difficult to put all your faith in a new method in one big leap!!

   Type at you later,
     Dan McEntee

[Lauri Malila]

..

[kiwibrit]

Wow, once shipping and all the charges have been applied, one of those Berkley hot line tools costs $40 to arrive at my UK home. Times are tight;  I shall experiment to see if a small electric soldering iron will do the job!

[kenneth cook]

                 Dan, we were using them for combat but I fly all the sport stuff with the same lines. The only failures we ever encountered was at the line guide at the tip. We would flip our lines now and then because it would fray them were it rubbed on the bushing. It didn't matter what material we used because I was also using the ceramic tip guides used on fishing rods. I love the stuff and I never EVER had a knot fail. The lines always broke where it exited the plane. Most of my  early combat planes were using nylon bushings at the tip guide. It took quite a bit to fray the lines but eventually they would.

[Dave_Trible]

                 Dan, we were using them for combat but I fly all the sport stuff with the same lines. The only failures we ever encountered was at the line guide at the tip. We would flip our lines now and then because it would fray them were it rubbed on the bushing. It didn't matter what material we used because I was also using the ceramic tip guides used on fishing rods. I love the stuff and I never EVER had a knot fail. The lines always broke where it exited the plane. Most of my  early combat planes were using nylon bushings at the tip guide. It took quite a bit to fray the lines but eventually they would.

I think I would use cable to the bell crank and exit the lead out guide just like with steel lines and then attach the other line there.  That would eliminate the wear problem.  I'm just getting my first airplane intended for those lines ready to go and that's my method.  I can also go back to the steel quickly if I wanted.

Dave

[Colin McRae]

This is how I have been doing my PowerPro Spectra, very simple using Sullivan 80# clips. Never had a line failure or knot come loose. And no fraying.

I have been using 65# test Spectra lines, even on my heavy Vector 40 at 62 oz. Concerning overall strength, two 65# test lines to a model would total 130#. In level flight, my Vector probably has a pull of say 10# (5# per line). Or a safety factor of 13.

Some pilots are using 80# test. The only reason to do so that I can think of would be for lower stretch. But 80# is surely not needed for overall strength.

Also, lines can end up with slight damage over time (dragging lines on the ground, someone maybe stepping on them, etc.). I can make up a new set of lines for around $5. So, I have been replacing my lines that have lots of flights on them every couple of years. Just additional safety factor overkill for me.

[kenneth cook]

            Dave, I don't use a adjustable handle on my combat planes. My lines are exact length using a button style bellcrank. 60' center to center. Using leadouts to the tip would be consistently changing from plane to plane therefore I keep them all the same. We pull test prior to a match and inspect at the designated area. Unfortunately, more than once the failure I mentioned only happened in the area subjected to wear.

[Jim Hoffman]

I see some discussion of Spectra failures.  Perhaps this empirical data will be helpful

I’ve done a bit of destructive testing on Spectra materials. I pull test samples to destruction to allow me to make decisions on lines material for a given weight airplane.  Based on testing, my rule of thumb is to plan on failure at 50% of manufacturers rated capacity.  I then size and validate my flying lines to withstand a 15G pull test knowing they will see a 10G pull test at contests.  A proof test of 50% of max normal operating load is an aerospace standard.

TESTING
•   I make the test sample ends exactly the way I make my flight lines.
•   Test samples are  1 to 2 foot in length.
•   I generally make 5 test samples of any product under test.
•   I tie the knots per the Mike Stinson You Tube video and use weld rings at the ends.
•   I use a luggage spring scale with a max load indicator dial.
•   I work my way up to failure in 5# increments and dwell at each load maybe 5-10 seconds.

RESULT:
•   I have found that the material fails at about 50% of the rated strength, although there is certainly some variation.
•   Failure occurs where the line exits the knot.
•   I have tried knitted overbraid per the kite community and found no improvement.

My test samples included:
•   Macuatro Power Pro 50# test
•   Macuatro Power Pro 65# test
•   Fins Spin 5  25# test
•   Fins Spin 5  50# test
•   Windtamer 100#  test   (this made it to 70% which is the highest % load achieved by me)

[Dave_Trible]

            Dave, I don't use a adjustable handle on my combat planes. My lines are exact length using a button style bellcrank. 60' center to center. Using leadouts to the tip would be consistently changing from plane to plane therefore I keep them all the same. We pull test prior to a match and inspect at the designated area. Unfortunately, more than once the failure I mentioned only happened in the area subjected to wear.

OK , well I still don't quite follow where the problem would be as long as you were careful to tie all the ends off equally-might require a holding fixture.  In my combat days (1970's)  we did this but did have a somewhat adjustable handle- the Hot Rock.  In any event maybe nylon guides or eyelets might help.  I'm using the nylon/teflon sheath from those RC control cable pushrods on some of my classic airplanes albeit with .027 cable.

Dave