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Quote:
The original strings used in the CX2 are spun from "Kevlar" which is by far more inelastic and can provide much better throw precision at less than half the string tension compared to "Dynema" type strings. To reduce friction at the pylon leading edge, where the upper strings bend into the boom tube, small portions (5-6cm) of "Dynema" string are knot-in. The rest is all "Kevlar" string. To restring. I suggest to pull out the strings at the pylon opening and knot new strings directly to the old ones at about 4" distance to the belcranks. The strings can be fed back into the boom one by one, by clamping on little weights made from soldering wire. The string tension is right, if the stretched strings produce a lower tone buzz, rather than producing an improper higher pitch "ping" which would be by far too much of tension. Roland |
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Last edited by KINETIC; Mar 16, 2012 at 11:40 PM.
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Tom:
The last time I bought some kevlar string, I got it at Hobbies n Stuff, which of course is no more. However, check with Skyler or Stan, they will steer you right. Hint: with kevlar, don't worry too much about the "strength". If it threads through the holes on your servo arms, you won't be able to break it. Yours, Greg |
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Thanks guys
Skyler has a spool of kevlar thread at the shop but we decided it was much smaller diameter than the stock cx2 thread,so I didn't get it. Kevlar fly tying thread is indeed very strong, but I think it too has much smaller diameter than what I'm trying to match.the diameter might not make a difference, but I'll look around for the closest thing to the stock string. My strings are all in good shape now but I'm tryin to prepare for a replacement before they show wear . Thanks for the input guys- Tom |
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I got a couple spools of Kevlar thread at McMaster-Carr.
I don't particularly like Kevlar thread for pull lines - it gets torn up easily if you use the "loop around the servo screw" method to tie it to the servo horn. I find spectra/dyneema mouch tougher. More elastic than Kevlar in theory, true; but it'd probably be difficult to tell the difference in how the model flies I actually have to go into the man-cave today and replace a section of Kevlar thread on one of my planes... |
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I've only replaced one. After reading Roland's setup tips, I think I had them stretched too tight. I elected to just go ahead and use pushrods as a replacement. That cost me .5oz but I used the heaviest stuff (.032") that I had just to test the theory. So if you want to keep it light stay with the string. I think I've heard of someone else restringing before but it is not common that I know of.
Charlie |
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I have replaced the strings on both my CX2s with #24 teflon tubing and .020 wire. Didn't add any additional wt to the plane (after removing the bell cranks from the tail boom). I have no double centering issues anymore and the surfaces are stiffer than I could get with the strings.
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I was able to route the wires so I could use the stock horns. Also, by using .032" wire, I did not need to modify the hole size and it fits very snuggly.
I might consider using lighter wire on the next install if any of my string setups ever need repairs. Charlie |
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Oh one other thing. If you use the thinner .020 wire I found that I needed to thread a toothpick through the hole in the pylon where the bell crank shaft was and glue the tubing/pushrod to that toothpick "bridge" to stiffen it up. It's an obvious "fix" when you realize you can't exactly glue the pushrod down for the whole length of the install.
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Other option works really well...
Go to a large crafting store and head to the beading section. Look at the 19 to 21 strand braided steel line Teflon coated. Won't stretch ... Try and break it.
In the same section , look at the small beading crimps. Super small tubes that you crush with pliers once the line has bee run through. Nice, simple and strong and you can replace one (if you ever have to) I'm about 5 minutes. Tbird out! |
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