AeroWorks Free Style Extra 260- Electric Conversion

[flylow3d]

Overview:

Flying the AeroWorks 100cc Extra 300 in XFC this year really gave me a good insight to the quality and flight characteristics that you receive with an AeroWork’s airframe. I was someone who always thought AeroWorks built heavy airplanes, for 3D style of flying anyways. After a friend let me fly an AeroWorks for the first time (which was the 100cc Extra 300) I went home and purchased one that same day. Impulse buy, probably, but I have loved every flight with it and it served me well at XFC. Long story short, Aeroworks offers some incredibly competitive planes for 3D and freestyle flying including the 79” Freestlye Extra 260. This plane really lives up to its name as it really excels at freestyle flying (which means that is 3D’s just as well as it flies precision.)

In this thread, I am going to show some detail into converting this bird to electric. The AeroWorks manual is extremely detailed so also take a look at that when assembling this model. I am not going to show every step as I will focus on the tips and tricks I use when building an airplane.

Specs:
Wing Span 79 Inches
Wing Area 1175 Square Inches
Fuselage Length 66 Inches (Rudder to Front of Cowl)
Fuselage Length 69 Inches (Rudder to Front of Spinner)
Cowl Width 8.5 Inches
Weight 10.5 to 11 Pounds
Engine 30cc to 35cc Gas
Spinner Size 3 Inches
Radio 6 Channels Minimum

Equipment Used:
Motor: Motrolfly 4330- 200kv
ESC: Jeti Mezon 90 lite
Lipo: Two Pulse 6s 2650 mah 45C in parallel for 12s 2650mah
Prop: Falcon 19x10 Electric Wood
Servos: MKS X8 850 on elevator and rudder, MKS X8 380 on ailerons
Radio/Receiver: Jeti Ds-16 with R7 rx
Backup supply: Scorpion Backup Guard

The Build:


Step 1- Control Horn Installation.


The kit includes very light, but strong, carbon control horns. To start, I use a file to rough up the portion of the control horn that will be glued into the surface. After assembling the controls with the supplied ball link, bolt, and nylon lock nut, I cut the slots and test fit the control horns for all of the surfaces. I found that the control horns needed to be pushed towards the hinge line on each of the surfaces to be sure that the ball link was centered over the hinge line. After I had the control horn where I wanted it, I taped around the control horns. This does two things for me. It gives me a guide to cut out the covering where the control will be glued, and it also makes it easier to clean up after gluing the control horn in as you can easily pull off the tape. I personally use Loctite Hysol 9462 for control horns and for gluing in the hinges.

Step 2- Hinging the Rudder

To make it so the airplane fits in a decent size box to ship it, AeroWorks leaves the rudder off of the plane. This means we are required to used the supplied hinge point style hinges to install the rudder. The manual is very detailed in how to do this properly, so I will just provide some helpful hints that make the process even easier.
First, use blue painters along with a hole punch to put tape around each of the holes that will get a hinge glued in them. This makes clean up a ton easier since you really only need to get the big globs of glue off after sliding the rudder on. After it is done drying, you can pull the tape off and the covering will be free of any left over glue as it will be on the tape. Remember to flex the rudder in both directions to make sure no binding will occur after the glue has dried. Tape the counter balance to hold the rudder in place and let it dry.

Step 3: Seal the Hinge gaps.

One thing I always do on my plane is seal the hinge gaps. Sometimes it makes a huge difference, and other times not so much. It is hard to tell whether it will help or not, but there is no downside to doing it as it can only make the plane fly better. I use any kind of clear tape, or covering. It really doesn’t what you use, as long as its sticky and will stay in place.

Step 4: Mounting the motor and ESC.

First, I always mount the cowling and measure how far it is from the firewall to an 1/8” outside of the cowling. I measure 6 ½”, which is what the manual recommends as well. Simply measure the distance from the back plate of your motor to the prop hub and subtract that from 6 ½” to figure out how long to make the standoffs.
Next, we have to decide how to mount the motor. We can either use long standoffs to mount the motor using the mounting pattern of the motor, or we can make a second firewall which has a wider mounting pattern that will support the motor even better. I went with the second option. I made an aluminum plate that I could mount the stands off to, as well as the motor. I clamped this plate to the firewall along with a wood block behind the firewall (to keep the wood from splitting while drilling) and drilled some holes. I made some aluminum standoffs and mounted everything up.

To mount the ESC, I glued a carbon plate to the balsa that directs the air out of the bottom of the plane just behind the cowling. I had to sand a small notch in the first former so that the plate would lay flat. I used Hysol to glue this in place as well. I mounted the ESC here since most of the air exiting the plane will be forced to go over the ESC. This should ensure that the ESC stays cool.

Step 5: Tail Wheel and Landing Gear

There is not much to cover here as I followed the manual for this part. The wheel pants are very strong, so there is no need to brace them or anything. The only tip I will add here is for installing the tail wheel. I personally use gorilla glue when screwing directly into the wood to mount the tail wheel. The manual recommends super glue which works great as well, but gorilla glue expands around the screw and creates a really strong joint.

Step 6: Installing Elevator Servos.

The manual covers this step in detail so be sure to check it out. I just wanted to mention that I had to make a slight modification since the X8 servos sit a little bit deeper in the slots. The two elevator servos hit each other when installed, so I used phenolic servo washers to space both of the elevators servo out and the problem was solved. These washers can be purchased at Esprit Model. I also use these washers to install all of my servos as it holds them in place better.

Step 7: Pull-pull Setup
This seems to be one of the more difficult steps for new comers when it comes to this size of an airplane, so here are a few tips to make it a little easier.
First, build the servo arm side of it first. Install the ball links, crimps, cable, ect.. outside of the plane. Next, center the servo and install the arm. Make sure the arm is perpendicular to the servo case as this is very important for achieving a rudder that feels consistent in both directions. Now you are done with this end of the system. Doing it this way makes it so you never really have to work inside of the plane to pull the cables tight, crimp it, ect…
Next, tape the rudder to make sure it stays centered, and then pull the cable tight. To keep the cable from developing any slack while running the safety loop the crimp, use hemostats to pinch the cable. You should end up with a perfectly centered rudder, as well as tight cables.

 

[flylow3d]

Step 8: Aileron Setup using the “Finding the true center” method


The manual recommends a 1 ¼” arm for the ailerons, but I ended up using a 1” arm. I ended up with 40 degrees of aileron which is what the manual calls, but this setup will have a little bit better resolution.

I also want to mention how I setup the ailerons as I go about it very different than most. Let me first say that if you are simply setting up the aileron servo so that the arm is 90 degrees to the servo case, then you are more than likely not ending up with the best setup. Most people preach that a servo arm needs to be 90 degrees to the servo, but that would only work if the servo slot is perpendicular to the hinge line, the servo is mounted straight in the slot, the arm is a precise length, the control horn is directly over the hinge line,ect…. Any, and I mean ANY inconsistency here will make it so that 90 degrees to servo case really isn’t the proper spot for the servo arm. The cool thing is that we can actually compensate for any inconsistency, without even knowing what it is, by simply moving the arm on the spline or using subtrim.

Let me break this whole process down as I feel this is super important to setting up a plane, but most people are getting it wrong.

What is the goal? The goal here is that up aileron travel always equals the travel of the aileron going down. Sounds simple. So if my aileron travels up 40 degrees and down 40 degrees, then I am good to go, right? Absolutely not! This tells you nothing about the travel in between. If you set a reduced dual rate for the aileron (let’s say at 30 degrees), will both the ailerons be traveling 30 degrees (i.e. one is traveling up 30 degrees, while the other is traveling down 30 degrees)? More than likely no if you set the servo arm at 90 degrees.

Why matching up and down travel isn’t the whole story. A servo arm follows an arc, not a line. The point being that you can follow two different arcs, and still end up at the same point, but points in the middle will be different. If you setup the aileron servos with the arms at 90 degrees, then the arc that the servo arm follows pushing the aileron up will be extremely close for both ailerons, as will the arc for down aileron as well. Cool, right? But ailerons oppose each other, which means that the arc traveling down on one aileron, actually needs to match the arc traveling up on the other aileron. If the arcs don’t match here, then there is a good chance that the aileron travel from wing to wing won’t match between centered and full deflection. Which means you will be left with an aileron differential issue everywhere except at full deflection.

How will we know when we have fixed the problem? We will know the problem is fixed when the endpoints in the radio for the aileron servo are equal in both directions. This means that the arc that the servo is following is the same in both directions. If we do this for both wings, the aileron traveling down will match the aileron traveling up everywhere throughout the travel. Now the endpoints from aileron to aileron don’t have to match, and they probably won’t. For example the endpoints for the right aileron might be 130 and 130, and the endpoints for the left aileron might be 127 and 127. This isn’t a concern.

How to actually fix the problem. I set my endpoints to 125 and 125 for my ailerons as this gives me a small window to use subtrim if I end up needing it. I set the arm as close to 90 degrees on the spline of the servo because this is a decent starting point. I measure both up and down throw. Now let’s say that the aileron travels up 40 degrees, but travels down 45 degrees. Now this is where you would usually increase the endpoint for the aileron traveling up so it would also travel up 45 degrees, but now you should see that that means the servo has to move the arm further in one direction to achieve the same travel! This means the arcs are not the same since the servo is required to move more in one direction. Ok, to fix this, we move the servo arm on the spline in the direction in which we have more travel. In this case the servo arm gets moved so it points more towards the leading edge of the wing. Adjust the linkage to center the aileron, and take a step back and look at what happened. We increased the arc traveling up, but at the same time decreased the arc traveling down. Now measure travel up and down again and see if they are equal. If the “true center” is found to be in between two spline locations, then this is where subtrim comes into play. Just subtrim 5 points or so in the correct direction, adjust linkage to center the aileron, and measure again. Once you 125 and 125 gets you equal throw, you can adjust them a little to get the throw you want. Maybe drop them both to 120 if you want a little less throw, ect…

Does this apply to every surface? Of course, although it is not nearly important since other surfaces work together. For example, if you have two elevator halves with separate servos, up travel on one just has to match up travel on the other. If you set both arms to 90 degrees, then the elevator travel of both stabs should be very close to matching. Now if you want a consistent feel for both up and down elevator then this “finding the true center” method should be used.

Important note: Changing the length of a servo arm means you have to go back through this process as the “true center” location will change.

 

[flylow3d]

Step 9: Final Tips

To reduce the chance of a battery ejection, run the Velcro straps around the entire tray. This is much stronger since the straps now go around two glue joints. Gas planes are usually designed to just hold a gas tank, so the slots in the tray work fine. A battery, or two in this case, weigh more and this can cause a tray failure. This applies to almost every airplane I have ever owned, so it is definitely not specific to aeroworks.

Protecting the battery in case of a crash:

Always put foam on the back of the firewall to ensure that the bolts won’t puncture the battery in the event of a crash. Many nose in crashes lead to a fire because the lipo is punctured. Having your plane crash will already ruin your day, no need for it to burn up as well.

Prop spacer alternative:

The center hole on the falcon prop is tad big compared to the size of the prop shaft on the motor. Instead of buying and waiting for a special spacer, you can simply use tape. Carefully wrap the tape around the prop shaft being careful not to stretch the tape. This increases the size of the shaft equally on all sides so that when you do install the prop, it will be centered and therefore won’t vibrate.

Clips for the anti rotation pins:

Instead of using the supplied hairpins (which can be hard and time consuming), I made new pins using the supplied throttle pushrod. I cut 4 pieces and bent them twice to make them easy to install. I use small white servo wire clips which are used to clip the new pins into. These can be purchased from Experience RC.

Layout of Rx:

Setup for flying:

CG: I used the included “CG Buddy” to balance the plane, and the batteries ended up right in the middle of the tray.

JETI MEZON INTERNAL BEC: I used the internal BEC in the Mezon ESC to power my RX and servos. I am comfortable using this BEC for a few reasons. First, the Mezon has both a throttle lead and a telemetry lead that supply power to the RX, so connector wise, I am good for around 10 amps. The telemetry also tells me current load and voltage of the BEC, so I am always aware of how it is being used. To be safe on this size of a plane, I would never trust only one source of power for the RX though, so I am also using the Scorpion backup guard. This little unit provides 5 volts if for some reason the BEC should fail. The Jeti radio will warn me if the RX voltage drops to 5 volts, and then I will know to land. Now even if you don’t have a Jeti and might not know when the BEC fails, the Scorpion Backup packs enough capacity to fly a plane of this size for a whole flight.

Throws: I ended up using the same throws that the manual recommends.

 

[bigblueswope]

Two things:

1. The batteries are in series not parallel.
2. None of the pics are showing.