How to install aileron servos in the wings

As I mentioned in the article about installing aileron torque rods, I prefer to drive my ailerons with torque rods attached to a single servo in the middle.  But sometimes there isn’t enough space in the radio compartment for tail servos and an aileron servo, and some people simply prefer to mount the aileron servos in the wings.  It’s easy to install a short push rod from the servo to the aileron, and the dual servos allow flaperon and spoileron operation.  Even if you like torque rods, some planes have an inconvenient arrangement where the torque rods will hit the bulkhead at the rear of the radio compartment when the aileron stick is moved.

Consider the wing trailing edge of the Aerostar 40 that I am building.


As you can see, the trailing edge extends a long way behind the torque rods, and the bulkhead is behind it, so there is no way these torque rods will ever hit the bulkhead.

The other plane I’m building right now is a Bingo 20.  Here’s the plan, specifically the part of the plan showing the trailing edge of the wing, the torque rods, and the bulkhead at the back of the radio compartment.


The plan is misleading because if you build it just like this you won’t be able to get the torque rods into the radio compartment while you’re sticking the leading edge dowels into the holes in the forward bulkhead.  Believe me, because I built it this way and it didn’t work.  So I cut them off and got rid of the little block that used to cover the torque rods in the middle of the wing.  Then I filled the space with a piece of 1/8″ balsa attached to the fuselage.  Here’s what it looked like after surgery.


I’m going to attach my servos to little plates and then attach the plates to holes in the wings.  Here is one of my plates.


I just need some rails to screw the plate onto.  First I have to put something inside the wing to attach the rails.  I made this little plate from 1/16″ birch ply and attached it to the rear spars like a shear web.


Then I added small basswood sticks to the front and rear of the compartment.


Then I trimmed and sanded the plate to make sure it fits in the hole.



Next a couple of little blocks were added to the inside surface of the plate for mounting the servo.  First the servo is lined up in the correct spot to place the output arm in the middle of the slot.


Then a little piece of spar stock is cut off and glued next to the servo mounting tab.


Then the other mounting block is attached.


It’s checked for proper fit.


It looks pretty good.  Now the plate is placed back over the wing compartment and mounting holes are drilled for #2 self tapping screws.


The servo is mounted, the screws are installed, and everything looks pretty good.




Now it just needs some little pieces of wood around the hole to help hold the Monokote when the wing is covered.  I put a 3/16″ balsa stick on each side.


I wanted to show the finished product, but the Bingo 20 still needs to be covered, so I’ll just show you a photo of the exact same installation on my Lazy Ace.


Now let’s assume that you like this idea, but you just don’t have the patience to do go through all of the little steps.  You could simply glue a lite ply or birch ply plate into the bottom of your wing with a servo-shaped hole in it, and install a servo with the head sticking out in the breeze, as seen on my Telemaster.


It doesn’t look nearly as good, but that’s one of the great things about model planes.  You can build them however you want.  My Telemaster flies great, but don’t look under the wings.  My Lazy Ace flies great, too, and it looks good no matter where you’re looking.