Posted for "Angier M. Ames" <N2811a@comcast.net>:

For any of you with the LNC2 MKII tail, a description of how you go about 100% mass balancing the elevators would be most helpful!

The manual (the one I stopped reading several years ago) states 100% mass balance will be achieved when the counterweight arm hangs 1/2" to 3/4" low with all bits and pieces of hardware attached. Presumably this overwieght position is to account for the extra weight of paint, etc.

With the ailerons, balancing was a simple process because the hinge line was at the top skin surface. With the mkII tail as you know, the hinges are located on the centerline. Correct me if I'm wrong but I don't think this was the case with the older smaller tail. The hinge location was the same as for the ailerons...right? All of this is my round about way of saying (guessing) that the balance instructions mentioned above were meant for the old tail. If not, then I'm dumber than I thought.

For the balancing process on the bench, and in an effort to remove as much friction as possible (if there was any to begin with), I machined 4 bushings, each with .63 hole on the centerline and inserted them into the 1/4" holes in the elevator hinges. Now the elevator rides up and down on a .63 stainless pin through each hinge instead of the -4 bolt.

What I experience is that when the elevator has a certain amount of weight, there is a range of motion up or down on the trailing edge of approximately 1.5" each way where if you move the elevator up or down in this range the elevator will hold that position. Tip it a fraction further either way and the elevator will move on its own to full up or full down.

It's probably time to go get another beer and ponder while awaiting humorous responses to my pleas for help.

Angier Ames


[Before the masses start sending in their replies, I thought I'd just jump in here and toss in my own 2c.  I think what you are experiencing is a result of the friction between 1) the bushings and their axles, 2) the bushings and the hinges, or 3) a combination of both.  As you mentioned, the original small tail used piano hinge, the MKII tail uses centerline hinges with bearings. When the hinges are properly assembled the hinge brackets on the elevator are clamped tightly to the hinge bearings, and those bearings are what provide the only friction in the system (as long as they are in a nice straight line, all with a common axis.)  You would probably do better to insure that your hinge alignment is proper, install the elevators to the stab with the -3 bolts and tighten them so the bearings can do their jobs, then start the balancing process.  If the hinge alignment is right the elevators should hang TE down without any balance weight.  Start adding weight to the counterweight arms until you start lifting the elevators' TE.  In a frictionless system, when you have 100% mass balanced the elevators they would actually hang horizontally and the least amount of imbalance would cause them to eventually travel to their stops in the direction of greater imbalance.  Since it is impossible to eliminate all the friction you're going to find a dead band in the weight required where the elevators will hold a position until they are moved by more or less weight or a push in either direction.  If you can find the place where they hang TE up that 3/4" and return there when upset I think you'll have done the job.  If you've got too much friction in the system you can locate it by hanging the elevators separately by the end hinges (center weldment and outboard hinge), then insert the middle bolts one at a time and see which one causes the bind.  Sooner or later you'll find the problem (if one exists) and then you can address that situation.  I hope this helps, and look forward to hearing that you've gotten the elevators balanced to your satisfaction.  Knowing the level of excellence you strive for I'm sure that you'll get this sorted out in short order.  Keep at it.

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