Blackie

After using the search I was unable to find the answer I am looking for. Can someone please tell me how to attach the kevlar to the cuppling. Do I use the crip via tub method or can I just use the fish hook tie method?

Thanks
Randy

majortom-RCU

My Feedback: (40)

See my comments in post #5 on the following thread: http://www.rcuniverse.com/showthread...ghlight=kevlar

I use the yellow kevlar thread, and my comments apply to that form of kevlar. There is a comment further on in the thread concerning Aramid, which is a Dupont proprietary version of kevlar, which could also be used, but its physical characteristics are quite different from the yellow kevlar thread--at least in the form in which I've seen it. Aramid "cable" that I've seen is maybe braided, or some other process, whereas the kevlar thread is just parallel fibers with no particular structure to it. Aramid is a dark gray, sort of charcoal color, kevlar thread is yellow. The Aramid is coated, the kevlar thread is uncoated. I expect the Aramid would be a lot less prone to fraying compared to kevlar. Aramid has much larger diameter than the kevlar, not sure the Aramid would slip into the Sullivan threaded coupler the way the kevlar thread does. But probably the next larger size threaded coupler would fit it, although the next larger size is not hollow all the way through like the 2-56 is..

Blackie

Majortom, here's what I have. I already have the yellow type kevlar Du-Bro rigging couplers 2/56 threading along with the clevis. The kevlar will be ran through push rod tubes.

From what I gather in your post is that knots are bad so would I be better off stringing the cable through the couplers and then use crimp type tubes to hold the cable and use CA on each end of the tube?

Thanks
Randy

Forgues Research

My Feedback: (7)

Randy,
I don't know if this will help, but have a look.
http://www.geocities.com/roger_forgues/test.html

I use this setup on my 33% Extra on the rudder with a Multiplex Jumbo servo, and it hasn't failed me yet.

DGrant

My Feedback: (4)

Here's how I did mine...with coated Kevlar, K&S aluminum tubing, and electricians crimpers. The alum tubing is just big enough to get the strand through 3 times. I loop it through the connector, then come back through it again, then come back again for the final time. If you practice, the way you rig will help when you have to get that final tension, just before crimping.
The final adjustment is where the eyelets come into play. If you installed correctly, it should only take about 3 or so turns of the eyelets. The kevlar does not stretch either.

Here's a pic of the top.....this has the clevis's....BTW...this is a MidWest 27% Extra...

DGrant

My Feedback: (4)

And....here's the hor. stab...no clevis's necessary.

BTW...the tubing cuts nicely by just rolling it on the table with an X-acto. I measured mine to 1/2" increments.

Here's pic

DGrant

My Feedback: (4)

and one more of the bottom area rigging.....

Also..the plyers used for crimping...I got at HarborFrieght for about $3, there's a few different types of crimps on them.

Here's pic..


Don't forget.............after you've flown the plane...and in your preflights...if you adjust the wires...even slightly...it changes trim, it definately will, ever slight if adjustment is slight, but if you adjust bigtime, just be aware of trim. These flying wires are VERY functional.

Blackie

Thanks guys, I see there are no knots so its either by way of shrink wrap and glue or crimping.


Thanks again
Randy

majortom-RCU

My Feedback: (40)

Randy, I do not use crimp tubes at all. My components are, from one end to the other, servo arm, sullivan clevis in servo arm, threaded coupler threaded into clevis, kevlar thread CA'ed into the hollow tube of the threaded coupler. That's the servo end. In the middle I like to run some kind of nyrod from an inch or two behind the servo in a fairly straight line to the fuselage exit, where I trim the nyrod flush with the fuselage. I epoxy or goop the nyrod at servo end and tail end, and also somewhere in between depending on what structure is available to goop to. I glue a 1/8" thick balsa scab inside the fuselage at the nyrod exit, just to have more of a glue joint. When I say "fairly straight line" it's not geometrically precise, but I just don't want much of an angle where the kevlar exits the nyrod on the way out to the rudder/elevator. It is the one or two inches of kevlar at the nyrod exit that I don't want to expose to fraying, so I CA that part of the kevlar thread to protect the fibers, and I run the CA all the way to the rudder/elevator end, so the "thread" is now stiff and will slip into the hollow tube of the threaded coupler easily.

The CA'ing of the thread is done to measure before I hook up the terminations on either end. I just clamp a length of thread from whatever skyhook is handy, and clamp a piece of something heavy to make it hang down straight. Then I CA the servo end for a few inches, and the rudder/elevator end for whatever distance will run from inside the nyrod to the rudder/elevator coupler.

When the thread is cut to approximate length and CA'ed on both ends, I do the servo end connection: CA the kevlar inside the threaded coupler (no crimp tubes anywhere), thread the coupler into the clevis about halfway in, snap the clevis into the servo arm. Then I slide the other end of the kevlar into the nyrod as far as it wants to go. Sometimes if I hold the fuselage nose up the kevlar will slide right out the other end; sometimes it hangs up, and I just kiss the exit and suck air through the straw, and that pulls the kevlar through. Now I have 6-8" kevlar thread hanging out the end. I clamp my rudder/elevator to neutral, snap the clevis onto the control horn, slip the kevlar into the threaded coupler and hold it up so it's in line with the clevis. I set the end of the coupler even with the middle of the threaded barrel of the clevis, pinch the thread and coupler together at that point, and touch a drop of CA into the nearer end of the threaded coupler. Most of the time the CA wicks through, and I find my fingers are glued to the other end of the coupler. I'm used to that, so I just pull the thing off, leave some of my dead skin on the coupler, and for good measure maybe put another drop on the farther end of the coupler. I use a light pinch when I do this, so if the CA comes all the way through to my fingers, I don't have much of a grip on the threads of the coupler. I don't want CA fouling the threaded surface. It really helps to use a micro-thin tube for your CA to keep from dropping too big a drop into the coupler.

Now I trim whatever excess length there is of the kevlar, and thread the coupler into the clevis. You now have maybe 1/4" of exposed thread on the couplers to take up on either end, so you can take up 1/2" of slack in the line, if there is that much. Usually there isn't. If that's not quite enough, you can twist the kevlar thread, and that will take up a bit more slack.

The kevlar "cable" does not need to be guitar string tight, all it needs is to have zero slack. When I have both sides rigged, I turn on the tx and play with the stick while holding the rudder/elevator lightly, just to see how loose/tight I am. It needs only light tension, but it should not be loose. I aim for being able to deflect the rudder slightly--maybe 1/8" or so-- before the servo arm will move.

I have learned to put a 2-56 locknut on the coupler before I thread it into the clevis, so when I have the length and tension just right on both sides I can lock it in. It is important to have pretty much the same tension on either side of a pull/pull cable pair.

There is a problem which has not (so far) troubled me, but I have seen an installation where, when you moved the stick from one side to the other across the neutral point, the rudder did not transition smoothly, but at a certain point seemed to hop or snap from one side to the other. That I suppose is a hinging problem, and if I had that problem I think I'd probably re-build or at least re-hinge my rudder.

Just to provide a solid bearing for whatever tension there is in the pull/pull rigging, I like to have a pinned hinge as close as possible to where my control horn is.

As to knots, I just like CA better. You can CA to a fairly precise length with good control on tension. I have been a fisherman since I was a pup, and think I'm adept at knots, but haven't seen any that I like as well as this CA technique.

Fishing for bluefish, tuna, sharks, etc. I have rigged a lot of nylon coated steel wire leader with the crimp tubes and all that, so my preference for kevlar is just that--a preference. I know multistrand steel wire is used by a lot of better fliers than I ever hope to be, so I don't knock what works for the other guy. I hope this is helpful.

Blackie

Majortom, yes it was helpful I will see what our local hobby shop has in the way of the sullivan products you mentioned. Might I suggest that you try Vaseline, on your finger tips and on the threads this way the glue can not stick leaving your skin in tact.

Thanks
Randy

Robert300XS

My Feedback: (2)

DGrant, that's the Midwest Extra 300S, isn't it? You have an XS too, right?

DGrant

My Feedback: (4)

Hi Robert...that's a Midwest 300S. I got the kit for such a deal, I couldn't pass it up. The only diff is the flat stab, and that really didn't matter to me. Actually the elevators are different as well, to compliment the foiled tail on the newer ones they have counter-balancers. I was going to scratch out updated stabs from plans, but really didn't want to spend more time and money in it. I'm very hooked on it as it is.

Hey...what am I tellin you for....with a screen name like yours...I'll come to you with questions...(just kidding)

Really though, hehe....this is the only 27%er I have at this point. The next step in Giant's will be the GreatPlanes 330 @33%

Blackie

A club member that has long history in big bird 3D uses kevlar on his rigging, he is the one that gave me the idea of using the fish hook method. I saw him at the field yesterday and asked him about it again. What he does is loops the kevlar through the eye of an eye bolt and then gives it several twist then loops the thread back through the very first twist of the kevlar pulling it tight up against the first twist locking it in, then CAing the thread.


I believe I will use his method as since he trust this on his 33 and 32% big birds.

Randy

Robert300XS

My Feedback: (2)

DGant, I live in San Diego, you ever come down here to fly at all?

I tried flying my friend's MW300S, he won't let me fly long enough to do a decent comparison of my XS to his S He's got quite a bulky tail brace... I should talk him into lettin me lighten it up, lookin how it's tail heavy very slightly and all.. Poor guy is using a Hitec Flash 5, and there's some funky thing where it changes trim when he changes rates... He's getting ready to order a 9CAP so who cares

Blackie

Hello!! hey guys would you all mind using the PM to talk about your areas of flying I would like to keep this thread related to the title.

Thanks
Randy

CrashMeister

My Feedback: (4)

See http://cih.home.mindspring.com/hobby.../PullPull.html

Craig.

bugsiegel

My Feedback: (2)

i don't use kevlar any more.
now i use 30lb nylon coated fishing wire. it's easy fast and strong. I have never had one fail. I just loop it though the servo arm , twist two or three times and heat till the nylon melts to its self. low slow heat till you see it melting. use a lighter and keep it about two inches away. on the control serface end I use a rigging coupler for easy adjustment. clean cheep and strong as anything.
I have crashed planes and everything else is in pieces but the wires never break. no crimps or weak spots.
a few meetings ago i brought in a 4ft piece of wire and looped it in front of club. not one member could break the loop with thier bare hands.

DGrant

My Feedback: (4)

Randy...hey..sorry bout that...got carried away, as we sometimes do in the hobby.

Another thing I do, and it seems to help some, is lubricate the cables at the exit points in the rear of the fuselage. I pack it in pretty good with a very light grease, actually what I use is differential grease from RC cars. I did notice some chaffing where the cables exit, so I smoothed the exits some more, and added lube...replaced cables of course, and no more problem.
Once you get the hang of the cabling/rigging it's very easy to replace a marginal cable...like 5 minutes or so.

I'm thinking the stuff I'm using is the same as kev-cord..it's got to be, have a look at Crashmeisters link, and go to the link within that too. Matter of fact..I got this from Crashmeisters link.... There are some serious composites, and cables in here Blackie..this might be useful. ..I know where I'm getting mine next time...It's very reasonable price..
http://www.acp-composites.com/acp-cat.htm

redxfred

My Feedback: (3)

I want to try a pull-pull setup with no external horns. Everything hidden in the fuselage and wings. Here's the challenge: It's in a .60 size P-40! Any help?
Fred
VA

Blackie

After further investigating I found that Kevlar will fray real easy if it rubs up against a surface. Since the plane (Modeltech Magic) has already installed nyrod tubing for the small metal push rods offered in the kit. I will be using the tubes and where they exit out the end of the fuse I may get some rubbing so I am thinking of the 30lb test line that bugsiegel, offered. Anything thats light and will not fray will be idea.

Thanks
Randy