Servo Mounting

The standard method for mounting the servos have two problems:
  1. The control horns wind up hitting the main body when thrown all the way over in that direction. (See picture)
  2. Using foam tape for mounting, allows the tape to compress or expand slightly when large forces are placed on the servo, allowing a bit of "slop" in the control response.

The "Better" illustration shows standard foam tape used to mount the servo, however the servo is additionally "zip-tied" (or "tie-wrapped") to the body. If tied tightly, this will squeeze the servo (and tape) to the body, thus eliminating the ability for the servo force to compress/decompress the tape, and thus eliminate the servo slop.

The "Best" illustration shows a wood or plastic spacer being used, which is both thicker than the standard foam tape, allowing more servo travel without hitting the frame, and also more rigid, eliminating the servo slop described above.
One thing I tried is that when using foam tape, after the servo is securely in place, placing a drop of thin CA onto the foam tape. What happens is that the foam tape sucks up the CA, which then hardens, stiffening the foam tape. This seems to make it much more resistant to compressing and decompressing, eliminating the slop problem. I haven't tried yet removing the servo afterwards, so I dont know how much of a mess this might make!

Another thing I discovered is that sometimes the force on the servo is strong enough that even a servo which was mounted in foam and zip tied started to break-away and twist out from under the zip tie. The CA method (above) in conjunciton with an added zip-tie seemed to stop this. I don't know which one actualy did it. The point is, after you do have the servos mounted, check them occasionaly to see if they are moving when force is applied (via. radio input.)

Dave von Linsowe reports using 3M Scotch 468 Hi Performance Adhesive, as a good alternative to foam tape.  It comes in rolls or sheets and it is just adhesive.  No foam or backing of any kind. It works really well for this application. This would probably be categorized in the "better" category, as you are not going to get the servo slop, because the adhesive is rigid. I will also add, several people have had success in not using a wood or plastic thicker spacer, and and just being careful to use good strategic planning of the movement of the servo arm - as well as maybe cutting the horn a bit so it doesn't strike the body.
People have also had success removing the label on the side of the sticker which they are gluing to the Hornet body (or spacer). This allows the servo to be glued directly to the spacer, rather than relying on the strength of the glue between the servo and the sticker, which was not meant to handle any type of load.

Also, plan on putting the pushrods into the farthest hole on the cyclic servo arms, not the closest one in.  While you will have to tone down ATV's, this gives you better resolution.

Note that it is this sticker (on both sides of the servo) that prevents the top from separating from the base, and all the gears coming out! Make sure that when removing the sticker and gluing the servo on, that care is taken so the top will not separate from the base.