Radio Control Installation Tips

Quite frankly, a lot of radio installations I have seen at the field frighten me.  They seem carelessly thrown in as an afterthought in the rush to get a new or repaired plane in the air.

I have learned that the time taken to ensure the radio is installed properly pays big dividends in life expectancy of the aircraft, ease of and reduced maintenance as well as simpler flight trimming.  In fact, if there are loose servos or excessive play in the setup, then the aircraft will not trim properly.

• Example of a Poor Radio Installation

• Always check your radio installation against the plans before building anything.   If you need to plug precut holes or cut new holes, it is a lot easier to do before the component is built.  Make sure you write notes and good measurements on the plans so you remember what you were doing later.

• Most R/C models have a removable wing that covers the radio compartment.  The fuselage has a "U" shape through this compartment and is inherently weaker and more flexible than the rest of the fuselage.  This arrangement has been proven to work satisfactorily.  However there is no reason not to improve it.

I like to cut a former that splits the radio compartment into two parts.  The aft section is the servo compartment and the forward section is the receiver/battery compartment.  Measure the length of the battery and receiver.  Add 1" to the longer measurement and that is how far back from the LE the new former should go.  You want enough room to surround the receiver and battery pack with foam without it being able to shift around.

Mount the switch and the charge jack in the servo compartment so the wires coming from them do not have the receiver or battery pushed up against them.  Be sure to cut a 1/2" or larger hole in the former to pass the servo leads to the receiver and also drill a hole for the throttle pushrod housing.

In the above image, the charge jack is mounted in the wrong compartment due to poor planning on my part.  It is in the way and I have to be careful not to stress the wires too much when working around it.  A wire can break causing intermittent contact and result in bad things happening to my model.

Unfortunately in this case there wasn't a lot of room in the servo compartment to mount the jack.  In retrospect, the former could have been moved slightly forward to make the servo compartment larger.

• Please use foam rubber to wrap your receiver in.  I have seen several planes at the field that were simply stuck inside the airframe using sticky-back Velcro.  When you are holding your plane and you can feel the vibration coursing through it, the receiver is feeling the same thing and it is not good for it at all.

  The electronics we put in our models are delicate and should be treated as such.  Some people seem to think these things were designed to withstand anything, but they are wrong.

• I used to install the radio after the basic structure was complete.  What usually ended up happening was I had a lot of binding to take care of and it was hard to get everything lined up properly.  It also took a lot of time for a less than satisfactory result.

Now I do the servo installation before I even begin framing up the fuselage.  It seems tedious, but the actual fact is I save a lot of time by doing it in the beginning.  There are a couple measurements you need to have.

First, I put the grommets and eyelets in the servos and then I measure from the bottom of the grommet to the center of servo arm (servo in side view).  This tells me where the servo rails need to be from the pushrods.  Now it is an easy task to glue rails into the fuselage sides before I join them and also cut the pushrod exits.

The only other measurement I need is how from the tail the pushrod exit should be.  Just draw a line on the plan from where the servo will be mounted (you will need to know what servo arm you are going to use) to the control horn.  The hole goes where the line intersects the fuselage side.

• Example Radio Installation

• When installing servos, one of the biggest mistakes I see made is to crank down the screws until they squeeze the life out of the rubber grommets.  Those grommets are there to absorb vibration which they will not do if they are too tight.

  The idea here is to tighten the screws only to the point where the grommets start to bulge and then stop.  After all the screws are in, try to wiggle the servo.  If it is solid, then the job is done.

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Copyright © 2002 Paul K. Johnson