Building the Legal Eagle Fuselage Systems
Page One

4/24/2010; rudder pedals fabricated

Shown is the rudder pedal attachment. The fuse stub coming off the lower longeron is 5/8 x .035 and the pedal pivot tube is 3/4 x .049. Two collars were cut, one was welded to the stub, the other drilled along with the stub for a cotter pin (shown temporarily safety-wired in place). The collars capture the pedal and will prevent it from wearing out the cotter pin and/or binding against the weld at the longeron.

4/26/2010; control column assembly

The various parts of the control column have been fabricated and assembled. I am departing a bit from the XL plans because I want the elevator to be pushrod actuated instead of via a closed loop cable system. The standard configuration involves pulleys and cable guides in a mildly complicated setup. The pushrod may be a few ounces heavier but will be much simpler, require no maintenance, and satisfies my aircraft sensibilities when it comes to the elevator control circuit.

I added a .035" metal sleeve in two locations plus a bushing for the control stick pivot bolt. This will add rigidity and durability to the control stick and prevent the pivot bolt from wearing out the hole in the control tube.

4/28/2010; Lower tail brace cable attachments

Bushings were welded into the lower longerons so the lower tail brace cable fittings could be attached with AN3 bolts. This arrangement makes it possible to remove the tail brace cables from the fuselage after they are swaged onto the fittings. Adjustment is also possible by putting washers on either side of the fittings.

5/1/2010; tail fittings fabricated and tail surfaces mounted to fuselage

A drill block was made from scrap lumber and drilled on the drill press to assure the holes in the top longeron for the horizontal stab attachments would be drilled square. The fuse was carefully leveled and the drill block leveled. 3/16" pilot holes were drilled then enlarged to 3/8" for the bushings.

Detail of the forward horizontal stab attachment.

And the rear attachment. Incorporated into this fitting are the elevator stops. I will probably use smaller hardware for the stops when the plane is assembled.

The shop is getting smaller!

All tail attach fittings and holes have been drilled. The tail surfaces flop the way there're supposed to and the tail is ready for fabrication of the brace cables.

Work has begun on the elevator bellcrank and pushrods. Bits and pieces for attaching the Soneri tailspring and wheel are also in hand.

5/8/2010; fuselage controls assembled

Note: Most of the hardware in the following photos is low-grade temporary stuff for mock-up purposes only. Rest assured final assembly will be exclusively with proper AN hardware.

Let's take a tour of the elevator control system. The control stick has been stiffened by the addition of 4130 sleeves. Visible is the rod end bearing at the forward end of the elevator slave pushrod. Bushings keep the bearing centered in the control yoke.

The slave pushrod terminates at a bellcrank at mid-fuse. Elevator control is transferred to the master pushrod which extends to the bellcrank on the elevator.

Two pushrods were used for the following reasons:

1) The forward portion of the pushrod has to be located low enough to not interfere with the bottom of the seat.

2) Most importantly, the side-to-side motion of the stick (aileron control) must be accommodated by the elevator pushrod. The use of rod end bearings translates the lateral motion of the control stick without causing any binding in the pushrod.

Detail of the bellcrank bearing and the yoke that captures the rod end bearing.

Since this intermediate bellcrank only has forward/aft motion, the rear master pushrod doesn't require rod end bearings. Much lighter aluminum fork fittings on used on the rear pushrod.

Here is a view down the fuse from the control stick to the tail showing the alignment of the pushrods.

The action of the elevator control is absolutely free of any slop or friction. Very, very nice!

A very slight 1/2" jog is necessary to get the pushrod to clear the fuse members at the tail.

Because the pushrods are 5/8" x .049" 6061, a guide is located midspan of the longer rear pushrod. This removes any flex from the system. This may be overkill for a 60 mph airplane but flex and/or flutter in the elevator circuit is unacceptable.

Two Adel clamps on the pushrod serve as elevator control stops. Adjustable, light and simple.

The above illustrated elevator control scheme is not per the official Legal Eagle plans. The original system uses a combination of pulleys, cables, and simple fasteners similar to what is found in the marine community. Field experience has proven that system to work but I wanted a more conventional aircraft setup. Obviously the question of increased weight of the pushrod system is going to be raised. Because I didn't build the original system I can't directly compare weights. However, here is a listing of the components of each arrangement:

Standard Legal Eagle elevator controls:
1) 24' 3/32 cable
2) Two turnbuckles
3) Four cable sleeves and thimbles
4) Two pulleys with brackets and hardware
5) Elevator bellcrank with two arms
6) Four cable fairleads with welded fittings

The pushrod elevator system:
1) 11' 5/8" x .049" 6061 aluminum tubing
2) Two rod end bearings
3) Two aluminum fork fittings
4) Intermediate bellcrank with mounting bracket and bearing
5) 1/2 elevator bellcrank
6) welded pushrod guide

I suspect the weight difference between the two systems is very slight at most. The smoothness and tightness of the pushrod systems has to be felt to be truly appreciated. It will also be practically maintenance free. I like it.

Another departure from the Legal Eagle plans is a simplified rudder stop. The standard stop is an adjustable arrangement that includes a clamp, 4130 channel and two bolts with four nuts.

I saw no reason for the adjustability so went with a very simple piece of 4130 strap welded to the tailpost.

Here is the rudder stop doing its thing. If wear is ever detected at the contact point very small pads will be welded to the ends of the stop.

The Sonerai tailwheel assembly from Great Plains was attached to the fuse via a single piece of 3/4" x .035" 4130 tubing. The spring comes drilled for an attachment bolt and makes for a clean, simple, and easy installation.

The cast aluminum fork and wheel are also part of the Soneri setup. The 4" wheel is very nice with ball bearings but a little chunky. A lighter wheel may be installed later.

Shown is the tailwheel spring tube and the lower tail brace cable fittings which are attached with bolts in welded bushings in the lower longeron. The standard attachment uses clamps around the longerons which would make it impossible to remove the cables once installed.

This arrangement has proved itself to be invaluable as the tail group has been assembled and disassembled several times in the course of designing the elevator pushrods.

10/12/2010; This is one of the aileron bellcranks. The plans call for the bellcrank to be made from a single piece of 1/8" aluminum and secured to the strut via a 1/4" bolt, but I decided to use bearings so there would be no wear or slop in the system. The bellcrank was built up from two pieces of 1/8" aluminum so the bearing can be centered in the bellcrank and this will also allow tweaking of the geometry of I decide to add differential aileron travel. The rivets can be drilled out and the output arm reclocked a few degrees to provide more up travel than down. Flight testing will reveal whether or not there is enough adverse yaw to make that mod necessary.

The forward left aileron cable pulley needs to be offset a little in order to clear a fuse diagonal tube. The plans call for a simple strap, I thought this bracket was a bit more elegant and sturdy.

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