Installing wiring within a foam wing to outboard ailerons
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I am in the process of constructing a 65 inch span Mustang. The Aileron servos will be placed out in the wing at some distance from the fuselage hence will require an extension lead from the receiver out through the wing to the remote servo. With a solid foam cored wing, what is the best way to do this so that you could disconnect and remove that servo if you so wanted. Do you for example leave the extension wire buried in the wing from the the receiver and make a pocket outboard where the servo lead can be plugged into this extension or is there a better way? I do not want to cut the servo lead and solder on an extension as that makes it almost a permanent fixture. The aim is to have the servo as mentioned located out in the wing and coupled via an extension to the receiver, but, in a way that would allow for removal of that servo with its lead intact and ideally, without having to cut into or damage the wing to do so. Any expert ideas would be most appreciated. Thank you...Paul.
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an effective way to make a wire tunnel is to get a piece of 3/8 copper tubing (thin wall) long enough
to fit from the root of the wing to the servo cutout. Sharpen the tubing with a razor knife and slowly
use the tubing by pushing into the foam and using a slight twisting motion to cut. Back the tubing out every
inch or so and clean out the scrap, then continue further into the foam. This procedure will leave you with
a nice tunnel and make extension install very easy.
to fit from the root of the wing to the servo cutout. Sharpen the tubing with a razor knife and slowly
use the tubing by pushing into the foam and using a slight twisting motion to cut. Back the tubing out every
inch or so and clean out the scrap, then continue further into the foam. This procedure will leave you with
a nice tunnel and make extension install very easy.
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I have the copper tubing too and do the same thing except I heat the tube very hot with A torch, it melts the foam as it goes, A perfect lead tube. I cut my servo leads and solder in new wire to extend my servo leads. I have had the extensions get dirty and slow down servo action unless you remove the leads and clean them every year at least. I solder and forget. It's A lazy thing!!

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Drill out the channel thru the foam using either of the previous posted methods (drilling or melting). Then buy an extension such that the length will allow you to extend the wire into the receiver. When you need to remove the servo (to replace it or for maintenance), you disconnect the wire from the receiver, tie a string on it. Pull the servo out until you get to the plug. Disconnect the servo and repair or replace it. Then connect it back to the extension wire. The string you tied earlier is then used to pull the extension back into the fuse so you can plug it back in to the receiver.
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Thank you for the replies sent. Just one further question...if you cut the tunnel through the foam, I take it the idea is to feed all of the wiring and the plug connections through this. I have just measured the extension connectors I have for my Futaba set which are exactly 3/8in across so would be a tight fit. The other potential problem might be then, if and when you had to remove the servo, pulling this lead out with its connector plugs (with a string attached) could lead to its dragging in the foam tunnel and consequently ripping into the foam as you pulled it:Is that a potential problem here? Many Thanks.
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Yes, the tunnel you drill or melt out needs to be large enough that the extension cord with the connector on the end can be easily pulled through. If the wing is thick enough, you can use 1/2 inch pipe to drill the hole. If you use the melting method, the hole will be larger in diameter than the pipe because the heat will melt away the foam a little larger than the pipe itself. When you connect the servo lead to the extension cord, tie a string around them to hold them together inside the wing.
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The only thing I shall add to the suggestions given is: after making the connection to servo lead with extension wrap both connectors with masking tape to prevent them from coming apart. This will also permit them to be withdrawn without scraping the foam tunnel, if and when you wish to do so.