Black Horse Liberty Electric ARF
I have always enjoyed watching model airplanes fly and spending time with the wonderful people who fly them. As a hobby shop owner, I got to know many modelers personally and found that they and their families are some of the best people I have ever met. After a while watching other people fly, I decided to join them in the air.
It took a while, the hobby shop made weekend flying with an instructor difficult to schedule, but I had advanced to the point that I could fly a trainer without everyone in the pits diving for cover each time I landed. After a few more landings even my trainer’s nose wheel stopped bending so far backwards that it needed to be straightened before the next flight.
A few years ago I “retired” and closed the Hobby Shop. Family responsibilities and a busy travel schedule kept my trainer securely grounded except for one or two flight sessions per year. This was not enough air time to keep up my piloting skills. Gradually, my flying skills diminished and I no longer felt comfortable flying solo.
I do not like losing skills and miss all the friends I had made during my flying years. So this year, things are going to be different. This year, I am going to fly, solo and become a better pilot than I ever was. With that decision made, I needed to find an airplane that will let me get into the air often and is easy to fly with the fewest hassles.
Electric power has advanced since I was active in the sport. I had no trouble fueling and starting the glow engine in my old trainer. Even setting the mixtures was not a real problem. But an airplane that starts almost by itself with just a switch, and doesn’t go “dead” in the air, will allow me a lot more air time.
Photo 1 Photo 2
After talking to many pilots, reading Sport Aviator and Model Aviation, and checking around for electric-powered trainers, I settled on the new Black Horse Models “Liberty” Almost-Ready-to-Fly (ARF) trainer. This brand new airplane combines the power of an advanced “outrunner” electric motor with an easy-to-manage size and light weight. The wingspan is just under 58 inches and will be easy to see in the sky and to transport on the ground. Weighing around 2 1/2 pounds makes this airplane easy for me to handle at the field. It is supposed to have a very light wing loading around 12 oz. / sq. ft. so it should fly slowly and give me time to regain my skills.
Hobby Lobby offers the Liberty and all the support equipment to finish it at a good price. The airplane itself costs just $110 for the ARF kit. I chose the AXI motor, despite its $80 cost, on the advice of some of my flying “buddies”. They said this airplane would do best with a strong motor to handle climbs and winds. The Jeti Advance PLUS 30 Amp Brushless Controller cost $69 but can be adjusted to suit the airplane using the included programming card.
The HS-55 HiTEC and HS-85BB servos seemed the right size for the Liberty and cost less than $60 for the three of them. Power is supplied by the Poly-Quest 1800 mAh, 3-cell, Lithium-Polymer battery. This battery is called the “Twenty” because it can continuously put out 20 times its rated 1800 mAh capacity.
Translated into English (not always easy for a native Cuban like me to do) this means the battery can supply up to 36 amps of current for the entire time the airplane is flying. As it turned out, the AXI motor and APC 9 x 6 in. propeller required only 21 amps of power. Since the Speed controller was rated at 30 amps continuous power output, the battery was outperforming the rest of the power system. The battery costs $64.
The total cost form me was just under $400. This is about the price of most Ready-To-Fly (RTF) glow trainers that do not have the convenience of electric power. And I will not need to buy fuel and a lot of field equipment, just a charger. On that, one of my good flying friends, Joe Lachowski, had an extra Smart Charger 2500 that he was kind enough to give me. Thanks, Joe! Like glow equipment, all these new items can be transferred from one airplane to another so the cost is not really as much as it may first appear.
The Smart Charger senses when the battery is near full charge and also works with the Poly-Quests’ Protective Circuit Module / and PCM Guard to monitor each of the battery’s three cells during charging. Monitoring each cell is the safest way to charge a Li-Poly battery as no one cell can receive too much charge.
As you can tell, learning all this “electric stuff” took some time but my friends helped out and any remaining questions the people at Hobby Lobby were able to answer. I am not an electric power expert but I am learning. I love to learn new things and this is just one more good part about model aviation.
Building the ARF Liberty
Photo 3
Another new thing to learn was how to build an ARF. My other trainer was an RTF; I just screwed the tail on and rubber banded the wing halves together. There are few RTF aileron equipped electric-powered trainers available and I don’t think they would include the motor and battery selection the ARF Liberty allows me. So I had to build an ARF if I wanted a high-performance electric-powered airplane.
But the Liberty is easier to build than many ARF trainers. Some parts bolt on like an RTF. The wing spar is an aluminum tube just like my old RTF wing. The motor mount must be glued in place but then the motor is just bolted to it; no positioning or adjustments required. There is no fuel tank or throttle linkage to worry about. All the construction is strong but light and easy to align.
Photo 4 Photo 5
The wing looked like the simplest thing to build. So, after warning some of my best friends not to leave home without their cell phones so I could call for advice, (model people really are the best around), I opened the box and started my first major airplane project. I tried sliding the wing tube (spar) into one wing half. It fit but it looked like too much was left sticking out. I marked the wing tube where it met the center of the wing and then measured each “half”. The tube seemed a little too long on one side. I tried sliding the wing halves together just to check and they did not meet as planned (photo 5).
Photo 6 Photo 7
When the distance was measured, it turned out the tube was nearly 1/2 in. too long (photo 6). I marked slightly more than 1/2 inch on one side and used a pipe cutter to cut the tube (photo 7). The pipe cutter, a regular plumbing tool, cut the tube without bending it or deforming the ends. Use light pressure during the cut. Now everything fit together as it should so I went ahead and started wing construction.
(Ed. Note: We checked with Hobby Lobby, the exclusive Liberty distributor, about the wing tube spar problem Ms. Bueso experienced. Hobby Lobby checked the Liberty Kits in stock and found that every wing tube spar was the proper length. Obviously, Ms. Bueso’s wing tube spar problem was strictly a one-of-a-kind incident that will not be repeated in any other Liberty kit. But it did happen so Sport Aviator included it in this review. At least we all now know that the kits we receive from Black Horse Models are just stock kits and not “hand picked” for reviews only. We also now know that Hobby Lobby cares enough about their quality to check every one of the hundreds of kits they have in stock just to be sure no defective products are shipped to their customers.)
Photo 8 Photo 9
Photo 7 has the items used to assemble the wing. One clap is an electrical connector and the other is a standard carpenter gluing clamp. I used 3M’s low tack masking tape to hold the wings together without hurting the plastic covering. Spread the 12-minute dry epoxy on one of the wing root ribs. Insert the wing tube into one half, then slide the other half onto the tube until both center ribs are together. Use the electrical clamp to hold the two front wing mount pieces together. Then apply the masking tape to both top and bottom.
Photo 10 Photo 11
Use a strong rubber band to hold the two aileron torque rods together at the rear of the wing. Finally, apply the carpenter’s clamp to the back edge of the wing to make sure both halves match (photo 11).
Photo 12 Photo 13
The directions did not provide it, but the correct amount of dihedral is two inches at the wingtip when the other side of the wing is against a flat surface. This is one inch under each wingtip. Just to be safe, I put a 2-inch high spacer under one wingtip while the epoxy was drying (photo 12). You probably wouldn’t be using a cake mix box (my grand daughters were coming to visit and they really like my brownies) but the box was a perfect fit. Whatever you use, make sure it is two inches high and flat enough to fit under the wing. With all the tape, clamps and dihedral spacer in place, hold one side of the wing flat against the building board until the epoxy cures.
Photo 14 Photo 15
Once everything is dry, remove the clamps and the tape. While the ailerons, elevator and rudder hinge slots are cut and the hinges mounted, the hinges are not glued. Remove the ailerons and drill a 3/16 in. hole in the center of each slot. Install the hinges half way into the wing. Normally a pin is put into the center of each hinge to position it halfway into the wing while the aileron is installed. Then the pin is removed. But the Liberty’s hinge slots were an exact half-hinge fit so no pins were needed. Apply 12-minute epoxy into the torque rod hole in the aileron. Then hold the aileron tightly against the wing and tilted up or down. Apply thin CAA adhesive to both the top and bottom of the hinges.
(Ed. Note: See the Sport Aviator Article “Installing Mylar Hinges” in the Flight-Tech section for complete hinging details.)
Photo 16 Photo 17
The Liberty’s aileron servo mount is designed for a micro servo like the HiTEC HS-55. This is my first electric airplane but I know that electrics do not need as much servo power as do glow airplanes. Servo demands are lower to do less vibration which also means the airplanes are lighter too. But still, I just was not sure that the 15 oz. in. output of the HS-55 was enough for two long ailerons. So I substituted an HS-85 BB servo which has a 42 oz. in. output.
But this required the servo mount hole to be made bigger as shown in photo 16. After cutting the larger opening, lay the mount on the wing and mark the area for the larger opening (photo 17).
Photo 18 Photo 19
After cutting out the larger opening, use a high speed rotary tool to remove enough of the center rib area to fit the larger, deeper servo (photo 18). Lay the mount centered on the larger opening and mark around it. Then remove the plastic covering where the mount will glue to the wing. Use epoxy to glue the mount to the wood in the center section.
Photo 20
Install the servo and screw in place. Assemble the provided aileron linkage and hook it up. The final result should look like photo 20 above. After test flying, the excess metal pushrods can be cut to final length. Center the servo and make sure the ailerons are centered as well when hooking up the final linkage.
Building the Fuselage
Photo 21 Photo 22
The Liberty’s stabilizer bolts on the fuselage using two nylon bolts. This simplifies alignment and can eliminate gluing the stabilizer in place. My experience selling some of the early RTF glow trainers makes me distrust this system. Sometimes these glow airplane stabilizers loosen after extensive flying. So I epoxied this stabilizer in place. Mount the stabilizer using the supplied bolts then mark the area along the fuselage (photo 21).
Use a metal straight edge and a Great Planes heat cutting tool to remove the plastic covering from the area to be glued (photo 22). The heat tool melts the covering without cutting through the thin balsa wood and weakening the stabilizer. Remove the plastic covering.
Photo 23 Photo 24
Seal the covering back into place with a covering trim iron (photo 23). Apply epoxy to the bottom of the fuselage area and bolt the stabilizer in place. After the epoxy dries, seal the area over the fin slot with the trim iron (photo 24).
Photo 25 Photo 26
Cut out the covering over the slot and seal it against the edges (photo 25). Insert the fin and mark it where it sinks into the slot (photo 26).
Photo 27 Photo 28
The fin has an extension that tapers to the fuselage forward of the slot. This dorsal fin only glues to the covering. It is possible to cut away the fuselage covering under the dorsal fin but the wood is very thin here and the covering is well adhered and tight. Instead, I tried something a little different.
Use 12-minute epoxy in the fuselage slot, make sure it is also applied to the inside part of the horizontal stabilizer. Use canopy glue under the dorsal fin where it contacts the top of the fuselage. Canopy glue not only dries clear, but it will adhere wood to plastic covering.
Use a modeling triangle to keep the vertical fin straight and a pin clamp to hold the dorsal fin in place. Sometimes tape can help keep things aligned until the glue dries (photo 28). For added strength, run a thin bead of the canopy glue along the base of the vertical fin against the fuselage and in the same area where the horizontal stabilizer meets the fuselage. This “fillet” reduces drag and strengthens the vertical surfaces. Run a finger along the bead to form a curved surface before the glue starts to dry.
Photo 29 Photo 30
Mount and glue the elevator hinges in place as you did with the ailerons. Keep the trim lines straight. Inside the fuselage’s back half are two plastic tubes. Insert the metal control rods into these tubes. The elevator rod exits at the rear of the fuselage but the rudder rod comes out the side. Cut away the covering where it exits (photo 29). Slide the elevator control rod to the rear and attach the plastic clevis. Snap the clevis over a nylon control horn and position the horn on the elevator. The clevis pin should be over the hinge line (photo 30). Make the screw holes and mount the control horn in place. Do the same for the rudder hinges and control horn.
Photo 31 Photo 32
I used two HiTEC HS-55 servos for the rudder and elevator. These servos weigh only 8 grams (0.28 oz.) yet are strong enough for the job. They also move fast using just 0.17 seconds for full travel. I like the speed because I can correct my wrong control directions faster, and there are a lot of those still.
The Liberty uses adjustable sliding control locks. On a glow-powered airplane with all the vibration, using this system on elevator control could be a problem. But the Liberty uses electric power and doesn’t have engine vibration. Still, use thread locking compound on the nut when mounting the control lock to the servo arm (photo 32)
Photo 33
At this point, mount the servos and insert the control rods. Center the elevator and elevator servo and lock the control rod in place. Use thread locking com pound on the center locking screw also. There is no center screw in the rudder control yet as the servo arm may be removed to fit the nose wheel steering arm into the plastic tube shown in photo 33.
Photo 34 Photo 35
The Liberty comes with a nice, pre-built motor mount. Insert it into the “firewall” slots and glue in place using medium CAA. Do not use accelerator here as it weakens the CAA bond. Let the adhesive dry on its own. After the mount is installed, run a bead of CAA around it against the firewall where it meets the mount base. This fillet makes the installation stronger. Again, do not use accelerator but hold the fuselage in place while the CAA hardens.
The Liberty’s motor is the AXI 2808/24. This outrunner motor has a 28 mm stator diameter that is 8 mm long. That is the 2808 part of the name. There are 24 winds of wire in it for extra torque. This is the /24 part. While other motors can be used, the Liberty was designed around this one. The motor mount and cooling inlets fit this AXI well. Mount the motor using the screws provided.
Note that the motor’s wires in photo 35 run underneath and through the small fuselage cooling hole on the passenger’s side of the firewall. Don’t do this. The wires block too much cooling air. Sorry to jump ahead but I had some cooling problems during the first few flights. The motor would run fine for about two minutes then shutdown as the speed control overheated even though the 30-amp controller was only working at 21 amps.
Photo 36 Photo 37
Solving this problem required several changes. First, make a hole on the pilot’s side of the firewall as shown in photo 36. This is for the motor’s wires. Then enlarge the small cooling hole on the other side as shown. This is easily done using a high-speed rotary tool. Originally, the speed controller was mounted further back inside the fuselage. Move it right up to the behind the hole for best cooling.
Use the high-speed tool with a 1/2 inch cutting end to open a 1/2 inch hole in the cowling as shown in photo 37. Since the Liberty looks a lot like a full-size Cessna, this hole looks like a Cessna’s landing light. The “landing light” should be directly in front of the speed controller’s enlarged cooling hole for maximum cooling.
Photo 38
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There are no exit holes for cooling air in the fuselage. Rather than possibly ruin the fuselage trying to make one, I first tried modifying what was available. Enlarge the rear elevator control rod’s exit hole as much as possible as shown in photo 38. The fuselage is open from the firewall to the back so air is able to flow all the way through it and out the bigger back exit.
Photo 39
Additional air exit holes were cut into the plastic cover for the landing gear. Cut these holes after the cover has been glued in place.
Photo 40 Photo 41
The motor just screws in place in the mount (photo 40). After soldering the connectors on, install the speed controller as described above. The Jeti Advance PLUS 30 Amp Brushless Controller can be programmed for each motor and airplane. Photo 41 shows the program settings used for the Liberty.
The Accu type sets the controller for lithium batteries (Li-XX) and mainly sets the range of the cutoff voltage. This cutoff voltage, the voltage level that makes the speed controller shut off the motor to protect the batteries while still keeping the radio system working, is fine tuned at the next setting. I have been told that the higher the cutoff voltage of a Li-Poly battery, the longer it will last so the Liberty has a high cutoff voltage setting.
Since the Liberty is a trainer and my first electric, I wanted the throttle to work like a glow engine’s so it was set for linear. The AXI motor is one of those outrunner types so the timing was set for it. To start, the brake was set on. Once all the pins were set, plug in the controller to the right side and a regular charged receiver battery to the left. After beeping things sounded, the Jeti Controller was set. There are more complicated programming systems using computers but this method is so simple any new electric pilot will have no problems.
Photo 42
Photo 42 shows the battery compartment. The battery tray is factory installed. It uses rubber bands to hold the battery in place. This system probably works well, but I knew the many bad landings the Liberty would be experiencing so opted for a stronger system. The hook and loop tie wraps are available at any hardware store. Screw each side to a hardwood block and epoxy the blocks in place as shown in photo 41. Remember, the speed controller does NOT go in the position shown here as already discussed.
Photo 43
The nose wheel bearing just bolts into the factory installed blind nuts. The steering control rod runs from the rudder servo through a slot already cut in the firewall. The rod runs inside a plastic tube that is also factory installed. The Liberty has more factory work done than is usual for an ARF and this helped me a lot in my first “building” effort. When installing the nose wheel strut, put a cardboard spacer between top of the spring and the fuselage (photo 43). There needs to be a little clearance here.
Photo 44 Photo 45
The main landing gear is screwed in place into the factory drilled holes (photo 44). One of the best things about the Liberty is that Black Horse Models have done all the drilling, blind nut mounting, alignment and positioning for you. I am not sure if my first effort would have been so easy with the usual ARF that required me to do a lot more.
Photo 46 Photo 47
Once the landing gear is in place, install the thick plastic cover. Cut notches for the landing gear as shown in photo 45. Then hold the cover in a curved position (photo 46) and use a modeling hot air gun to apply gentle, not a lot, warmth, not heat, so the plastic assumes a curved shape. Then use thin CAA to install the cover. Once installed, cut the air exit holes as shown in photo 39.
Photo 48
The last fuselage building step is installing the cowling. The cowl is factory decorated and fits the fuselage well. Make sure to center the propeller hole on the motor shaft and try to align the stripes. Most importantly, make sure there is enough propeller clearance. I learned that electric propellers have a lot more bend (pitch) at the center and so need a lot of space between the cowling and the propeller. Trial fit it first. Then drill the four mounting screw holes. It took me a few tries to get it right but it can be done.
Finishing the Wing
Photo 49 Photo 50
Just a few finishing touches are left on the wing. Trial fit the wing to the fuselage. It should fit well as did mine. Then install the center covering strip using a trim iron (photo 49). The wing has the bolt mounting holes drilled into it under the covering. Cut away the covering and install the two black hole reinforcers on the bottom of the wing. Cut out the top fairing and mount the wing in place as shown in photo 50. Measure the distances from each wingtip to the top front of the vertical fin. Both should be equal; mine were. If they are different by more than a sixteenth of an inch, you will have to enlarge the hole and reposition the wing. But since my wing was perfectly aligned, I just glued the top fairing in place with thin CAA. Make sure not to glue the wing to the fuselage.
Photo 51 Photo 52
Once the wing is aligned, install the plastic wingtips. Score along the wingtip. Do not try to cut all the way through. After scoring, bend the plastic flashing away from the wingtip. The plastic will break along the score line (photo 51) Mark each wingtip 1/8 inch in as shown in photo 52. Then position the tip on the marks and thin CAA it in place.
Photo 53 Photo 54
The final step is to install the wing decoration. I actually learned how to do this reading Sport Aviator’s building articles. Wet the area with a spray of dishwashing liquid and water. Apply the stick-on decals and then push out the water from under them using a few playing cards (photo 54). Let dry for a few hours and the decals are set.
Photo 55
I think the wing turned out good for a first attempt. Notice that the wing in the photo has the wingtips in place but not the center fairing. I decorated it first and then tried to mount it. Having the wingtips already on the wing made it hard to measure it for alignment. Remember this was my very first building attempt and I got a few things out of order. Learn from my mistakes and build the Liberty in the order mentioned and you will not have any of the problems I did.
Honestly, I made several of those “help calls” to my flying friends while building the Liberty and they came through for me. Thank you, guys. But the best help was the Liberty itself. So much was done and the rest pre-aligned and drilled that I could actually build this airplane, I am really proud of my first attempt and can’t wait to get it flying.
Flying
Photo 56 Photo 57
The Liberty looks more like a small Cessna than a Basic RC Trainer. I like the colors and the lack of a big muffler. I think the electric option allows the airplane to look better than it would with a glow engine.
Photo 58 Photo 59
Since I have not flown for almost two years, I let one of my instructors, (your esteemed editor), do the first flights. There were a number of club members at the field and they were interested in how well this “electric plane” would fly. So was I. All the questions were answered when the throttle was applied. The Liberty jumped ahead faster than a glow engine trainer would. It jumped off the ground in a short distance and climbed pretty fast.
I, and most of my friends who were watching, was surprised at the fast climb and high angle the Liberty could maintain. The Liberty reached several hundred feet high in just seconds. It really did not need full power for the takeoff. Once the power was reduced, the Liberty flew very slowly.
Photo 60 Photo 61
My Liberty, at 2.75 pounds, weighed a little bit more than the 2.64 pounds the book said it should. No doubt the battery straps and the larger aileron servo account for this extra weight. The actual airplane itself was very light yet strong. However, the Liberty never seemed to notice it was on the heavy side. It flew as if a big glow engine was in it, only cleaner, quieter and with faster response.
Photo 62 Photo 63
We had a speed controller cooling problem on the first few flights. So I only had just a little time flying it on the dual control system. I am not any kind of expert pilot, yet, but I thought the Liberty reacted faster to my stick movements. I also thought that it would fly more slowly than my 40-sized trainer which already flies slowly enough. The red stripes under both wings and under the stabilizer made the white airplane easier to see.
Photo 64 Photo 65
My instructor says that the airplane floats like a glider yet flies well in the wind. I guess that means he thinks the airplane lands well and would make a good basic trainer. I did notice that Liberty landed very slowly and appeared steady even with the nose pointed high in the air.
Photo 66 Photo 67
All the takeoffs happened very quickly. The airplane did not roll more than 30 feet before jumping into the air. The AXI motor was so powerful that the airplane would climb at a steep angle without slowing down. Landings were done slowly, even in a good wind, and with full control.
Photo 68
My instructor even tried a heavy cross-controlled slip landing (photo 68) and the airplane never once wobbled, it just landed on one wheel and then settled on all three wheels and rolled about 10 feet to a stop.
Once we solved the cooling problem, I got to fly the Liberty more. This is a very gentle trainer and I found it easy to start polishing off the rust. I even did a few loops and rolls, one at a time of course. The loops were much larger than I would have thought possible. I did the rolls by pointing the nose up and then applying full aileron. The Liberty rolled completely in about two seconds and the nose was back to level at the end of the roll. I don’t quite have the “down elevator when inverted” skills yet, but I know the Liberty will let me learn that too.
Photo 69
I like the easy “starting” this electric airplane has but I like the way it flies even more. I have only had a dozen flights on it so far and I think I will be soloing very soon. The Liberty flies for about 8-9 minutes on each charge so I get a lot of flying time each flight to regain my piloting skills. I never knew that electrics could fly this well. There is no feeling of not having enough power and the airplane does everything I want and nothing that I don’t want it to do unless I put in the wrong controls.
Photo 70
This is a very good airplane to learn on. I’ll keep my old glow trainer just in case I really mess up, but I don’t think that will happen. The Liberty just flies too well.
For more information on this electric-powered Basic Trainer, please go to: http://www.masportaviator.com/activedit/redirect.asp?website=ArticleLink_HobbyLobby_Liberty
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AIRCRAFT SPECIFICATIONS Radio: JR 631 6-channel Cost: $110.00 |
| Special Features Very Light Weight; More prefabrication than the usual ARF; Great Flyer; Good Power. |
| Notable Positives Very easy to build Extremely fast assembly Very good looks Light flying weight Good basic trainer performance Friendly electric power Very strong motor Notable Negatives |
Short URL: http://masportaviator.com/?p=617
Posted by Maria Bueso
on Jul 11 2006 Filed under Basic Trainers.
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