mikeainia

My Feedback: (1)

Just to clarify the lines that are now 'legal' and covered by insurance per AMA are braided spectra or dyneema not monofilament, which is way too stretchy to use anyway. Note that they must be braided line. Spectra and Dyneema are trade names for the "GSUMP" substance that is specifically called out in the General rules - where GSUMP stands for gel-spun ultrahigh molecular-weight polyethylene. Spiderwire has the legend 'Spun with Dyneema - the worlds strongest fiber' on its advertising now. One of the other name brands specifically mentions 'Spectra fiber' on theirs. As for the knots, a lot of testing has led to the conclusion that most all the knots shown cut the line strength about in half. We have found that Phil's modified figure 8 does offer advantages in strength.

GallopingGhostler

Hello Mike. Not sure where you are getting the absolute AMA requirement for Spectra. According to the current AMA National Model Aircraft Safety Code effective January 1, 2011 (see [link]http://www.modelaircraft.org/files/105.pdf[/link]), an inspection and pull test are required according to the current Competition Regulations (see [link]http://www.modelaircraft.org/files/2013-2014CLGeneral.pdf[/link].

According to the Competition Regs: For one, a little common sense. I am using monofilament line rated at 20 lb test for flying half-A sport models in a non-competitive environment in places say, like the back of my one acre lot. I am not doing this as a club activity. The local stores do not sell the Spectra. the 0.018" dia. lines is a little larger than the standard 0.008 steel cables, but I figure it is probably about as draggy as Dacron.

These 1/2-A models are less than 1 lb. weight, somewhere about half that and do not pull like the larger models, so any so called stretching is very minimal at best. The modern monofilament does not stretch like the stuff 30 years ago. For the larger aircraft I have the properly rated Spectra and steel cables.

If I don't replace the lines when they become damaged or fail a pull test, then I've failed to follow the safety code. That goes ditto for the properly rated stuff.

If one is a member of a club that has a policy to adopt the competition rules in its entirety including the line construction for sport flying, then comply with the club's rules.

The whole intent of the code is to ensure that our modeling activities are done in a safe manner. Lines are verified to be sufficiently strong and in a good state of repair to prevent from releasing a model by accident. Remember that there was a time that even Spectra was disallowed for competition, but CL fliers were using it for sport flying and their own competition practice.

I'd say in most R/C clubs, that if one showed up with their kid and an 18" wingspan CL plane with a .049 engine and non-Competition Regulation dacron lines, flying in a corner away from others, I doubt anyone is going to say anything.

mikeainia

My Feedback: (1)

GallopingGhostler

Sir, those documents I quoted are the latest publications from the AMA website. The Safety Code effective January 1, 2011 is the current one. It is referenced in the 2013 AMA Membership Manual on Page 4.

[link]http://www.modelaircraft.org/files/memanual.pdf[/link]

mikeainia

My Feedback: (1)

You are correct the ban on 'Fused' line is in the CL Combat section - sorry.  The table in the CL General section does not mention braided or non-fused construction, though in practice there is no monofilament Spectra or Dyneema.  Berkely Fireline is one of several 'fused' filament lines and I have used it for 1/2A's with no issues. 

GallopingGhostler

After reconnoitering, I was able to find gel spun ultra high molecular weight polyethylene (GSUMP) generic (Spectra is a trade name) in 30 lb. test 0.28 mm (0.011 in) dia. line in 100 meter spools for $5 shipping included on E-Bay.

This meets the criteria in the 2013 - 2014 AMA CL Competition Regulations, Paragraph 5.3.5.1 Spectra Lines, for aircraft to 24 oz. using up to an .09 engine, line rating 20 lbs with a 0.010 in. minimum diameter. It is not yellow, but then the paragraph states that yellow is preferred but not a requirement.

Reason for change is that I was able to find a source so reasonably priced, and I can get my money back from Wal-Mart for returning the unopened monofilament line. Since I plan to travel to a CL club meet in the near future, I'd be compliant if their site has adopted the Competition Regulations line requirements for sport and demo flying. I will have sufficient line to make up multiple and replacement pairs.

Also, I will be able to fly .09 planes with it.

scott17

I have used 10 lb. Spectra at 42' for 1/2A models with good results. I use 20# for .10-.15 size planes. Have been using it for a year or so and still use some of my original lines with no signs of wear. Small planes fly so much better on Spectra that I would never go back to steel!

GallopingGhostler

That is good to know, Scott. I've got a reel of Spectra, Pylon brand I think in my flight box for the larger planes. In this case, I'll know more when the stuff comes in. The smaller diameter stuff sort of reminds of the Dacron used years ago except it is significantly stronger, came in a small paper spool. Then we didn't care because it worked and it was cost effective, even came with the Cox RTF plastic jobs along with a small CL handle.

GallopingGhostler

The Dyneema 30 lb, 0.28mm dia. 100m (328 ft) line came in today.

After looking at the AMA CL 2013 - 2014 Competition Regulations, Paragraph 2 General states that Dyneema is compliant. Paragraph 5.3.5.1 Spectra Lines states that the line I purchased appears to comply with models for up to a 24 ounces weight using up to an .09 engine.

Aircraft Engine Watts Rated
Weight Displacement Spectra St.

24 oz .09 300 20lbs. .010”
32 oz .17 375 30lbs. .0115" < Extrapolated
40 oz .25 450 40lbs .013”
64 oz .40 600 60lbs .016”
75 oz .75 750 100lbs .018”

Some mentioned that they use the 30 lb. for up to .15 sized planes without problems. I gather that by extrapolation between #1 and #2 below more or less substantiates that observation, correct? Reason why I ask, is if I am flying with those who take a strict interpretation of the competition regulations for sport flying and demo, I can be assured I am compliant.

scott17

I use 30# for .35 size planes. 2 lines, 1/2 rated strength for knots and such, gives 30#. If your .09 size plane pulls anywhere near 30# you may need some adjustments...

aspeed

I don't think an .09 really pulls that much, The reason the pull tests are so high is because of whipping and especially when the lines go slack and it yanks back.  I have had the handle yanked out of my hand and the safety thong pulled on my wrist a fair bit with a .40 on a slow combat plane.  The next couple of days, my wrist hurt a bit, not the same day though. That was the end of the plane unfortunately. I have a fair bit of .009" wire but am thinking about the Spectra type stuff anyway because it is at least lighter and the wire is kind of rusty.

GallopingGhostler

I think you are correct about that, aspeed. The Competition Regulations were developed IMO to ensure a sufficient safety factor to prevent a model on the loose. That jerk factor you mention is a valid concern. This is why they test the lines per the following:
Personally in a sport flyer setting, I'd say that with the Spectra 30# test should be sufficient to .10 power. Given the low cost of Spectra / Dyneema, I'll buy another spool to take it up to the mid sized CL planes.

A half-A weighing 3/4 of a lb. should be pulled to 7.5 lbs.

Lou Crane

... a few days late into this thread, but I'll offer the thought that the GSUMP braided lines are much less stretchy than anything but steel. They should be available through a sporting goods store that carries just about anything for fishing.

Whatever you fly, there will come a time when you'll appreciate this instant, no-questions-asked response. You're not flying it on rubber bands any more.

Good references to the AMA rules information (membership not required). (I still think it is good to be an AMA Member, for the past 60 years!)

Enjoy!

GallopingGhostler

Lou, believe it or not, here in Clovis, NM, I haven't been able to find GSUMP line, except in bundled fishing reel packages. I guess that there isn't as much fishing out here in the semi-dessert. You've been an AMA member longer than I. Mine goes back to the 1970's. Passed by Sierra Vista a couple times over the years, seems to be a real pleasant community and in the cooler upper atmosphere. I guess you also deal with elevation effects there, I guess about the same elevation as Clovis at 4,300 feet.

Would be interested to know what CL fliers do to compensate for elevation effects on .09, .19 and .35 classes for sport / sport stunt.