Get yours from the Airplane Factory
The Armadillo is tough, and provides breakaway mounting for the main gear and wings. However, the most vulnerable part of the plane--the engine and front rails--are not protected. Ours tip-stalled in a steep turn and nose-dived into the ground. The top rail was bent behind the front vertical brace. Here is a simple modification that provides a breakaway engine mount.
Using a hacksaw, score the aluminum frame of the top engine mount on all four
sides, just in front of the front vertical brace. Cut fairly deeply. We want a clean
break here in a hard crash. If this breaks off, it may be easily repaired later.
Cut a piece of 3/8" square hardwood stock (we used maple) slightly shorter than the lower engine mount.
Mark the lower engine mount just in front of the front vertical brace with a pen. We will saw the engine mount in two at this mark. Before sawing, prick the brace on either side of the mark with a prick punch so that you may easily reassemble the two pieces with the same orientation as before they were cut. You can use a miter box to get a more professional-looking cut.
Hammer the hardwood into the two pieces of the lower engine mount, making sure to keep the two pieces oriented properly. Be careful not to ding the aluminum with your hammer, as we will want to make it easy to punch the wood out if it ever breaks. Use another piece of wood stock as a driver.
Drill the wood at the proper place so that the bolts may pass through.
If the upper mount breaks off, you may easily repair it. Drill out the rivets from the top of the front brace. The tricky part is getting the old wood out of the top frame rail. Cut the broken wood off smooth where the break occurred. Mark the center of the wood, then drill it out as best you can using as big a bit as you can without damaging the aluminum. Drill to a depth of 3 or 4 inches. Now, use a screwdriver to ream out the wood that the drill missed. Punch the wood out of the fromt piece of the rail that broke off.
Replace the wood you removed with a piece of 3/8" hardwood. Drill 1/8" holes where the rivets were. Reassemble using bolts instead of rivets.
Now, drill the engine mount holes, mount the engine, and go flying. No one will know you ever crashed.
If the engine is mounted
in the normal manner--with the rails below the mounting flange on the engine--the plane is
quite off-balance, requiring trim adjustment or a counterweight at the end of the left
wing. Mounting the engine as shown--with the rail above the mounting
flange--provides nearly perfect side-to-side balance.
In addition to better balance, this arrangement should provide better flying characteristics due to the right-thrust resulting from having the propeller to the left of the centerline. Right-thrust counteracts the tendency to fly left due to torque roll. The stock configuration provides left-thrust, which is the opposite of what you want!
We use a Supertigre 40. I don't know if all other engines can be mounted this way, but check it out the next time you have the engine dismounted.
Aileron
servos: We use a separate servo for each aileron, mounted in the wing as
pictured. We glued small pieces of plywood inside the wing with CA to screw the
servos into, but some guys fasten them to the wing spar with wire ties. Use music
wire to stiffen the ailerons. I used the ones that came with the plane.
Besides giving you flaperons, it seems to fly better, probably because there is less
aileron bending due to the torque point being closer to the center of the aileron and
there is less control wire to flex.
Weight and balance: With the ball-bearing Supertigre, the plane is nose-heavy. Our first armadillo had two lead tail weights installed by the previous owner. Since we mounted the aileron servos in the wing, there is no servo behind the fuel tank, we moved the fuel tank back as far as possible. Our original Armadillo had hard rubber tires. The new one came with sponge rubber tires that are a little over an ounce lighter per pair. With the new wheels and the fuel tank mounted as we have it, it is only slightly nose-heavy with no weights. It still needs a bit of down-trim to fly level.
Dihedral: We broke our wing spar in a bad crash. As the
manufacturers claim, it is no problem to open up one end of the wing and repair the
spar. While doing this, I increased the dihedral to approximately 3". It
seems to fly a lot more predictably and corner better now. We replaced the propeller
with a more efficient APC, and replaced a frame that was slightly bent (slightly before
the crash, that is!), so I can't say for sure if the dihedral was the cause of the
improvement.
Tricycle or tail-dragger? The armadillo may be built either way. The tail dragger version actually has a tiny steerable tail wheel. I have never flown or even seen an Armadillo built in the tricycle configuration. Using the Easy-Fly 40 trainer for comparison, I like the tail dragger better. Takeoff and landing techniques are not much different. The armadillo handles easier on the ground. After all, tail draggers have a larger triangle of support. A nose wheel is in a vunerable position and is often damaged during a hard landing. The taildragger probably files better due to less air drag.
Hardware: Socket-headed screws are easier to work with than the straight-head screws procided with the plane. To save weight, I used two nylon screws to fasten the landing gear. The steel bolt that attaches the wing was replaced with aluminum, as well as most of the washers. I could not find aluminum fender washers, a large and small regular washer works fine and weighs a lot less than steel.
I've flown only about four different planes in my life, so take this for what it is worth! Here I compare it to the Easy-Fly 40 trainer.
General: The armadillo flies faster and stalls at a higher speed than the trainer. Don't get too slow when you are close to the ground!
Takeoff: It is possible to take off with the Armadillo or trainer by simply holding full up-elevator and applying full-power. But that isn't the right way. The armadillo does not climb as steeply as the trainer, and while it will get off the ground, it will stall unless you remove the up-elevator quickly. Most likely you will end up back on the ground, or the plane will make a sharp turn.
Here is the proper way to take off. This is an adaptation from Microsoft Flight Simulator and my limited experience.
When taxiing and at the beginning of takeoff, hold the elevator full-up to keep it from nosing over. (Our Armadillo is a tail-dragger, but the up-elevator while taxiing is a good idea for any plane.) Advance the throttle slowly. Release up-elevator as the plane picks up speed. Stay on the ground until you get enough speed so that the plane wants to fly. Then rotate by applying a little up-elevator. It will rise smoothly. Continue to steer with the rudder for a while once it is off the ground. With good speed and a shallow climb, you will not experience the turn tendency to veer off in a sharp turn once it is in the air.
The Armadillo and trainer will take off with considerably less than full-throttle unless the grass needs mowing.
Turning: I have crashed the armadillo several times in short turns. It would just stop flying and head towards the ground. Keep the power on and speed up in turns! Also, it won't bank as steeply as the trainer, though it seems much better on our new armadillo, possibly due to the dihedral I added.
Landing: This is the plane I learned to land with. I STILL can't land the Easy-Fly without killing the engine. It just doesn't want to stop flying even at idle. The armadillo, on the other hand, will descend positively at idle--it descends a bit too fast if anything. I do my final approach with just a bit of throttle to slow the descent rate. When it touches down after a successful flare, set the throttle to idle. Or try idling it just before touchdown. The flaperons slow down both the speed and descent rate a fair amount.
September 04, 2002