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Great Planes DR1 E-Conversion with Kontronik Power
By Michael Heer
Aug 14, 2004, 02:00 AM
Introduction
This plane flies great! Handles well in the air and does aerobatics very responsively. Needs to be landed in a straight line into any wind or it "dances" (drags wing tip and/or noses over) when it lands. The plane and motor make for a very nice conversion project, but I had a couple of problems I had to work out before I praised the combination. I did a little head scratching and a little grumbling during problem solving. This review should let you get right to the fun that this combination provides. But I am getting ahead of myself so let me start at the beginning. The kit came very complete for use as a gas/glow engine powered plane. Page 5 of the instruction booklet showed a picture of the main components and a parts list. I set aside parts 13 (engine mount) and 16 (fuel tank with hardware) as they would not be used for my electric conversion. I examined all of the parts and all appeared to be of good quality and the covering with MonoKote was very nicely done. I didn't need to tighten up the covering on the rudder but I did on the elevator, on all three wings, and the fuselage required some work with the sealing iron and hot air gun to tighten everything back up. The covering even had a small rip in the bottom of the fuselage. I covered this rip with a small part of the piece of covering I removed from the horizontal stabilizer so that I could glue the stabilizer, wood-to-wood, onto the fuselage. This was a very easy MonoKote repair. The MonoKote finish was too smooth and pretty for a true scale plane but the coloring and the decals were appropriate for a version of one of the Red Baron's planes. (He flew more then one Dr. 1 triplane.) Actually, I liked how pretty this plane was and was happy to have it "prettier then scale"! The kit is a good bargain, with all they include for the price. Details included the twin machine guns and the metal step for the left bottom side of the fuselage. I used the Kontronik 500 Fun set that included the Kontronik 500 brushless motor (with 5.2:1 planetary gear drive) and a Kontronik Jazz 40-6-18 speed controller. These came with matching plugs to solder. I bought a pair of Sermos connectors to solder to the power supply end of the speed controller to plug into the battery pack. I had to purchase a simple 6 mm prop adapter for the drive shaft and a 14 x 6 propeller. I found this Jazz controller does have Battery Elimination Circuitry (BEC) that works with up to 18-cells, 24 volts. This gave me more options for use of this power package in other projects in the future. There is a two year warranty on these items per the Kontronikusa website and that is good to know in case something goes wrong down the road.
Finding A Motor Mount, and Making a Custom Front MountingRather then making my own custom motor mount I decided to try and use a commercially available electric motor mount so that anyone could buy that same electric motor mount and have confidence that they can correctly complete the conversion. I didn't know of anyone that made an electric motor mount for Kontronik motors, much less the Kontronik 500 with 5.2 :1 gear drive that I am using. I posted two inquires in two RCGroups.com Forums for information/recommendations on motor mounts. RCGroups.com member BEC responded in the Kontronik Forum and recommended that I check out the electric motor mounts sold by Esprit. I did and I liked the looks of one of the adjustable electric motor mounts they sell, listing it as a mount for another companies motor. It looked like it might work and there was some room for adjustment. I sent Esprit an e-mail with my questions. Zbynek Hubalek responded and he recommended that I use their motor mount and I ordered one from him. Unfortunately, the measurements on my Kontronik's planetary gear drive didn't have the screw holes in a matching location to use the front plate of his motor mount. I looked for other ready-made alternatives to fit the Kontronik and I e-mailed Kontronik on the subject. Unfortunately, I came up empty for a front mounting extension mount that fit this motor/gearbox right off the rack. That was a disappointment to me as it was my preferred method to mount the motor. Additionally, if there were a commercial front mount that fit it would make duplication of my conversion very easy.
With no ready-made mounting front plate available I was looking for ways to modify the one I purchased from Esprit and was considering making a plywood front mounting plate. I mentioned my search and problems to a friend, Fred Bronk (RCGroups.com moderator and good guy) and he volunteered to make one out of aluminum to match up with my Esprit mount. My final motor mount used the base plate and rods from Espirit and the front plate mount made by Fred. The bolts that were used to secure the motor to the front plate were from Orchard Supply Hardware (M3s). I hope that with the availability of the Kontronik motors in this country increasing, that an off-the-rack fitting mount may soon be available for this motor. In case that doesn't prove to be the case, I reviewed some other motor mounting options below.
RequiresBesides the motor, motor mount, and speed controller, other parts needed for the plane include:
A trip to R/C Country on a Saturday and I got the additional servos and wires I needed for this project. The battery packs to power the motor were Lipoly packs from Apogee, they are discussed later in this review. Having examined and photographed all the parts, I remained impressed with the quality of this Great Planes kit. I was ready to begin assembly.
ASSEMBLY
The completeness of the instruction booklet is excellent. I expect that any modeler investing the money and the time into this conversion would have at least one or two planes under his or her belt and will be able to follow the instructions and self answer questions by looking at the many pictures included in the instructions. As stated above I will be focusing my attention on the steps that relate to the conversion of the plane from a gas engine to the Kontronik electric brushless motor. I have only limited comments on the general assembly of the plane....the first one being "Use a screw driver with as large a handle as possible." Much of the assembly is drilling holes, screwing in the proper screw, removing it and hardening the hole with thin CA, then reinstalling the screw. I started with a small metal handled screwdriver and developed a blister before I finished installing the landing gear, which is the first official step. I bought a screw driver with a larger handle (still small point), which made the process much easier. Also, slightly sharpening the tips of the 4 large plastic wing mounting bolts helps greatly to ease and speed assembly at the field.
Aileron ExtensionsMy first deviation from the instructions was to use a twelve-inch extension wire for the aileron servos, not the recommended six-inch extension. Ultimately I added a six inch extension wire to the Y connector that I painted red and glued to the side of the metal strut. It plugs into a socket mounted in the fuselage for easy assembly at the field. In all I used 1 Y connector, 2 twelve-inch extension wires, 1 six-inch extension wire and an on/off switch with charging jack. Finally, one mounting plug for the aileron extension from the upper wing to plug into at the fuselage.
THE CONVERSION PROCESS
I determined that there are four separate steps that needed to be discussed as part of the conversion process. The first and most important was the selecting of the motor system to power the plane. The second step was selecting the electric motor mount and securing the motor and mount to the plane. The third step was the selection of the batteries to power the motor and where and how to configure and secure them to balance the plane. The fourth step was what if anything to do for easy access to the batteries for replacing or recharging them at the field without disassembling the plane, if possible.
Step 1 -- Power Plant SelectionThe first step was easy. I saw that Great Planes had become the exclusive distributor in the U.S. for the Kontronik electric motors and speed controllers. This same announcement recommended the Kontronik 500 Fun System as the appropriate power for conversion of several Great Planes kits from gas power to electric power and the Fokker Dr.1 was on that list. The 500 Fun System includes the Kontronik 500 brushless motor with the 5.2:1 planetary gear drive installed and the Jazz 40-6-18 speed controller. Since then Great Planes ads have announced the Kontronikusa website and there they have the product application chart. That chart confirms my motor/speed controller selection as the one they recommend for the Dr.1. The only assembly on these parts was to solder the connectors that come with the motor and the controller onto the wires so they can be connected, and then heat shrink the color tubing over these connectors so they won't touch each other and short out the system. I added Sermos connectors to the wires for the battery connection, as that is my connector of choice for this project. (These connectors were important as they allowed me to use a very flexible battery pack system to power the plane.) Lastly, I trimmed the receiver connector on the speed controller to remove the fin for Futaba J connectors as I am using a Hitec Electron 6 receiver with positive shift to match my Jr 8103 transmitter. A little trimming with the Exacto knife and the plug fit into the receiver just fine.
Step 2 -- Motor MountingI've already mentioned where and how I acquired the specialized electric motor mount. Let me supply you with a few more details. The instruction manual informed me that the "drive plate" (That is the portion of the prop adapter that the back of the propeller rests against) must be 4-1/2" in front of the fuselage for proper cowl mounting. To further complicate the conversion process, as shown in the picture above, the motor mount/firewall was actually recessed about an inch from the front of the fuselage, and angled to give the proper thrust line of right and down thrust to adjust for the engine torque of the recommended gas powered engine. I decided to go with those same thrust lines. Actual mounting of the motor mount was really quite simple. I measured to determine where the adjustable front end plate should be located to get the back of the propeller the required 4 1/2 inches in front of the fuselage (That was fuselage and not firewall) and assembled the mount accordingly. I determined that I should add two 5/32" plywood shims to the firewall and then mount the metal motor mount to those. I next measured to match up a hole for the speed control wires with the existing hole in the firewall. I scored the firewall and the back of my now 10/32 (5/16) with an Exacto knife and mounted the spacer with thirty-minute epoxy applied to both parts. Latter bolts went through the firewall and my spacer, so the plywood addition was very strong. The motor mounted onto the front of the metal motor mount with four M3 bolts in the predrilled holes (that Fred made) so that was easy. I had to trim the bottom off the plane's motor cowling (as required for any type of power) so it could be used to confirm proper motor location. With the cowling now ready for use, I rested the back of the fuselage (Where the rudder would attach.) on the floor and placed the assembled motor unit on top of the plywood I added to the firewall. I trial fitted the fiberglass cowl over the motor and slightly adjusted the position of the motor mount base to best line up the fit with the cowling. Holding the motor mount in position, I removed the cowling and marked where the bolts should go into the plywood to secure the motor mount to the fuselage. With the markings made, I drilled 3/32" holes for the mounting bolts. I set aside the motor and mount and used a small drop of instant CA to harden these holes, and wiped away any excess glue. After the CA had dried I bolted the motor mount to the plane with the motor already installed. I used six, 3/32 x 1-1/2" long bolts through the mount with a washer, lock washer and nut on each bolt inside the fuselage. With motor and mount in place, I trial fitted the fiberglass cowling per the instructions. I had a good fit. I recommend mounting the motor in the proper location before doing anything else. It was much easier without the wheels in the way or the rudder on the back of the fuselage. I then assembled the plane step by step per the instructions.
ALTERNATIVE MOTOR MOUNTS
My quest for an off the rack front plate motor mount system failed but I have hopes that someone will develop one for the 500 Fun System in the near future. I spent several weeks in my search for the perfect front mount. I could have used the motor mount that came with the plane and a "clam shell" mount to go around the motor and secure the motor to the mount. An additional wood spacer as I described above might have had to be added to the front of the firewall to get the "drive plate" on the prop adapter 4 1/2 inches in front of the fuselage with this method. Another alternative would have been a clamp mount that secures the back of the motor on or near the wooden mount to the fuselage. That is the type of mount recommended by Great Planes Support when I contacted them by e-mail. They recommended a J'Tec mount part number: JTCG6801 (pictured above). A thick additional spacer to move the motor forward would have to be used with that type of mount for certain. If I were doing this review over I would probably go with the clam shell mount onto the motor mount because my goal was ease for others to duplicate my project. The mounting plate Fred made for me was simply too nice not to use on this project. Only one step into the project and I had violated my goal for easy duplication, but I have given you alternatives to use to mount your motor in the conversion process. Pictured above are Kontronik 500 motors mounted using the different methods I described into the Tiger Moth of Michael Rogozinsky and the Pilatius Porter of Ryan Van Beurden. Both of these are recent E Zone reviews. Both of those mounts have 1 to 2 degrees of down thrust and no right thrust in their motor mount assemblies. It was obvious by looking at my plane's motor that I had several degrees or more of both down and right thrust and I worried if this was to much for either or both. I decided to fly it this way to Keep it Simple and see how it performed. This was more right and down thrust angle then I had ever used with an electric motor and it was a concern that almost caused me to remount the motor on several occasions before conditions allowed for the first test flight. The Key Points of Motor Mounting The keys to remember are that the back of the propeller has to be 4 1/2 inches in front of the fuselage and the motor has to be mounted so that the prop adapter goes through the small hole formed for it in the cowling. This meant I had to test-fit the motor in the mount with adapter and the cowling to get it properly located against the firewall/wood spacer to get the motor and the prop correctly positioned.
Step 3 -- Battery Selection, and APOGEE LIPOLY BATTERIES
With this plane weighing over 9 pounds ready to fly when configured for gas power it is considered a light plane for its size. I initially planned to use two packs of seven or two packs of eight 2400 nicad cells connected in series. Instead I am going with Lipoly batteries from Apogee, as their greater power and duration should help the flight characteristics and time in the air. The lighter weight of the Lipolys was not a factor in this project. The plane was tail heavy without the planned big and heavy gas motor on the front, so the weight of heavy nicads (if located behind the firewall) is not a disadvantage in this project. I connected two packs of Apogee Lipolys in series to power the plane. One pack was a 3s2p and the other a 2s2p pack with each cell having 2080 mA and the pack had red and dark sermos connectors. To power the motor I simply plugged the red connector (positive) of one pack to the dark connector (negative) of the other pack (thus wiring them in series) and connected the speed controller to the two remaining wires, one from each pack. The packs were in series this way, and I had the juice of 5s2p. That was the power I wanted for the motor and I was only using 10-cells. I can (slowly) recharge the individual packs with my simple Hobbico charger as separated I have a three cell count pack and a two cell count pack. The first benefit of this arrangement was the flexibility I got in combining the packs. (This type of assembly of packs must be charged separately and not as a combined unit! Do not try and charge as a 5s2p pack!) Secondly, the packs can be used in separate smaller motor projects or harnessed to even more packs for a larger project. Lastly, this arrangement allows for additional flexibility in battery positioning in the plane and the potential for better battery cooling than using a single 5s2p pack. If more duration was desired I simple use two 3s2p and two 2s2p packs in both a series connection as described above and then a parallel harness putting them together to get 5s4p power. The Lipoly powered test flights used this 5s2p power supply described. I have previously used other Apogee batteries in smaller projects starting with a 2s 830 pack and I found it worked excellently with several different planes starting with the Cermark Dragonfly that I first flew in Hawaii and my Great Planes Wright Flyer. NOTE: While my Hobbico charger charges two packs at the same time, it is limited to a maximum rate of 1 amp and these 2080 cells can be charged at just over 4 amps. A higher capacity charger, charging just one pack at a time, could get the job done in about half the time. I decided to power the radio unit and servos with a separate 4 cell Nicad 600 flight battery pack. I removed the red wire from the speed controller to disable the BEC in the speed controller. This allowed me to connect the Lipoly's to the speed controller and finish assembly of the plane with the motor and radio systems off. I turn them on with the switch mounted (per the instructions) under the middle wing on the left side of the fuselage. Even with this on/off switch it is best not to connect the motor batteries until you are ready to fly for safety reasons.
STEP 4 -- BALANCING ON THE CENTER OF GRAVITY
With the system wired up it was necessary to determine were I needed to locate and secure the batteries to get the proper Center of Gravity (C/G) balance location on the plane. Per the instructions that was 2-5/8" behind the leading edge on the middle wing. I started looking to obtain the proper C/G by putting the receiver and motor battery packs as far forward (next to the firewall) as I could. I reinstalled the middle and top wing but left off the wing struts that go between the middle and bottom wing for convenience in this process. I picked up the plane with two fingers on the C/G point that I had marked on the bottom of the middle wing and saw the tall drop quite a bit. The plane was tail heavy using the proposed Apogee Lipoly's.
The Dr.1 missed that heavy gas motor up front. I sided with Jeff Hunter's input to mount the weight as far forward as possible so that less weight would be needed. The forward most point would be above the motor on top of the motor mount. I removed the cowl and started stacking large round fishing weights on the front top of the motor mount. I added two, six-ounce weights and ultimately one, three-ounce weight for a total of fifteen ounces to balance the plane at the recommended CG of 2-5/8" from the leading edge of the middle wing, the weights were tightly taped in place. If I had used heavier Nicad batteries in a brick formation right behind the firewall I would have needed less lead but would have less flight duration as well. My 5s2p pack weighed 17 ounces while 15 Nicad 2400 cells weighed 32 ounces. I have built a parallel harness and have used two 5s2p packs for 5s4p power as mentioned below. For my initial tests the plane was balanced for the 5s2p pack. For the flights done with Nicads I was able to reduce the amount of lead on the motor mount. That was affected by the shape of the battery pack and how I could position it in the fuselage. I never had a proper shaped brick style Nicad pack to try against the firewall so I won't be discussing balance weights any further. The 2-5/8" measurement was the balance point used for all test flights. Control for acrobatics and level flight was good at the recommended C/G.
MISCELLANEOUS, TECHNICAL "STUFF" AND BENCH-TESTING
The plane assembly was estimated to take 20 hours for glow/gas power. I probably took more then twice that time as I worked very slowly on this project. The assembly was really quite easy, and the experienced builder can probably do it in about twenty hours with the proper screwdriver while working fast, but I wasn't in a rush on this project and admittedly assembled the plane quite leisurely. The throws on the ailerons, elevator and rudder were all set to match the recommendations. I found these recommended throws worked perfectly in flight testing. I strongly advise that the movement of the control surfaces in the instructions be followed. More is NOT better here!
Exploring the Jazz ESCThe Kontronik Jazz 40-6-18 Speed Controller has some very nice features! It can be used with simple programming in glider, plane, boat, helicopter or 2 car modes. Its battery elimination circuitry (BEC) works with 6 to 18 cells (or equivalent Lipoly up to 24 volts). It can be programmed for automatic shut-off for Nicad/NiMh batteries or Lipoly type battery packs, or it can be programmed for reduced power instead of shut-off. You can unplug the red wire going to the receiver and use a separate receiver battery pack to power the radio and servos if you prefer, or leave the red wire connected and have parallel power for your radio system with a separate receiver battery (WARNING: with BEC the system is always armed when the battery is connected even with an additional flight pack battery using an on/off switch.) I opted to disconnect the red wire so the radio on/off switch I mounted on the fuselage under the middle wing would let me turn the system on and off with the motor batteries connected to the speed controller. For even more information on this speed controller (and the Kontronik Fun 500) please see The Kontronik 500 Review here in E Zone posted on June 26th, 2004 by Ryan Van Beurden. Using my AstroFlight Watt meter and a Top Flite 14 x 6 propeller and the Apogee Lipoly packs (3s2p+2s2p) mentioned above, at full throttle using charged Lipolys, I recorded 38.5 amps and 667 watts drawn. With my Cermark One Touch tachometer I got a propeller RPM of 8,800. Since this was the prop size recommended by Kontronik/Great planes for this combination and as it was in the proper voltage/wattage range, it was time to fly.
FLYING
For most of my reviews I test fly the plane first, sort it out and then get a friend to fly the plane while I videotape it. For this review I had my friend Jeff Hunter initially fly the plane. Jeff is an R/C flight instructor, but more importantly he has had a number of flights with a gas powered Great Planes Fokker Dr.1 and I decided to put that experience to use. Jeff started up the plane and although the plane veered a little right, initially going down the runway, the take-off and climb were nice and smooth.
Motor ShutdownsIn fact, the plane performed perfectly for the first minute and forty seconds... and then the motor stopped working. Jeff moved the throttle down and back up and power was restored but he kept it off full throttle and wisely decided to set it down. The plane landed smoothly as shown in the video after a first flight of two minutes and thirty seconds. On the ground we ran the motor up at full throttle once more, but it shut down rather quickly. I removed the top and middle wings in a process that takes about ten minutes and nothing seemed excessively hot. The fuselage was very spacious but there was no air flow inside it. The question of what was the problem or problems that caused this short flight would need to be answered. However, since I had a second 5s2p lipoly combo ready to go I decided we should go for a second flight but stay near the runway. Jeff had another good flight with a loop and double rolls and when he went for a second loop the motor stopped again, as shown in the video. Again Jeff lowered the throttle and it rearmed and he brought the plane in under power and landed it.
After the first two test flights I knew the plane flew great but the flight times were way too short and my battery packs should work with this combination. I borrowed a friend's Astroflight 109 charger and took apart my combo packs and recharged my 3s2p and 2s2p packs one at a time. All four packs took nearly identical mA to recharge and proved there had been plenty of power at the shut down. I tried a fifteen-cell Nicad pack and the amps under power started at 34 and watts were about 550. Still after about 1 minute forty seconds the motor again shut down. The Nicads still had plenty of power. That made the speed controller the main suspect. Although I was drawing more amps then I wanted to, I couldn't go down much in the length of propeller because of the size of the fuselage. According to the Astroflight Watt meter I was within the specs for this speed controller and the prop was the recommended size.
Working on Getting Air IN to the ControllerOn Saturday afternoon I went up to R/C Country hobby store in Sacramento to get supplies to make a parallel wiring harness to make a 5s4p battery pack and to bounce some ideas off Fred Bronk who works at the store on Saturday. I just told him the facts, and he immediately asked me about cooling for the speed controller and battery packs. I told him that thus far it was just the big compartment with no airflow. His best guess was that with the lack of airflow, and that many amps, the controller was getting too warm and I needed airflow around it to cool it down. (It is intended that they operate with cooling air going past them.) It was good to hear that he independently came to the same conclusion I had, but Fred even had a couple more suggestions. He recommended drilling air intakes on the front of the fuselage. These would be hidden by the cowling, and install a cardboard tube to direct the air flow right onto the speed controller and a couple more holes generally to help cool the batteries. Secondly, he recommended I try a different prop and I did but I will discuss that later.
I took an empty toilet paper tube and cut it in half the long way giving me two half pipes. I cut them down and trial fitted them into the right side of the fuselage against the firewall and next to the right inside of the inner fuselage compartment. This way I had two cardboard half pipes directing air onto the speed controller. I drilled four air exit holes behind the bottom wing and one at the very back bottom of the fuselage (It is a really thick piece of wood back there, don't drill your air holes there.). Now with airflow I hoped I had solved the cut off problem that I and Fred "best guessed" was caused by the speed controller becoming too warm in the fuselage. Time to test the theory and proposed solution.
Success!The next test flight was again done at full throttle and with the air cooling holes in place and the outside temperature about the same as the first day I got close to double the duration time before the motor shut down. If I had stayed on topic I would have completely solved the problem right then. Ultimately, I simply enlarged the exit holes into an exit "trench." This finally allowed for sufficent airflow for the controller to be properly cooled by airflow as is planned for in operation. My initial holes for the exiting air where not sufficient to draw the air out as was necessary for continuous full throttle operation. Once I made the larger air exit space my shut down problem was solved. I could fly the entire flight at full throttle if I wanted and the motor would keep operating now without shut down.
Proper Prop SelectionI mentioned above that I didn't stay on topic and let me briefly discuss that in hopes of helping prevent you from repeating my mistake. Despite having almost doubled the full throttle duration with the cooling holes I didn't initially work on them further but rather started trying different propeller combinations. This lead to new problems with shut down at full throttle in under 10 seconds. A 14 x 8 Scimitar prop draws 44 amps and that caused the speed controller to shut down, exactly as designed. A 13 x 8 wooden prop still drew over 40+ amps and again caused shut down for excess amperage draw. The 14 x 6 or 13 x 6 Top Flite props will work fine in this conversion. Your prop selection is critical to your success.
Getting Air OUT of the Fuselage is as Key as Getting it IN!I reasoned that because of the size and shape of the interior of the fuselage, the airflow wasn't as good as I had expected from my past experience with gliders. The additional space for the air to exit the fuselage was more critical to establishing the proper airflow then I first realized. Working toward the upper range of the speed controller at full throttle, the cooling was critical. With the Dr.1, the proper prop size and sufficient airflow were the keys to success. My Dr. 1 now flew great at full or partial throttle. It only needs about 60% throttle to fly great with the 5s2p pack (even with the 14 x 6 prop). Beyond 70% throttle the extra throttle literally supplies more heat than speed as increased wattage doesn't make it much faster but more throttle does reduce flight time. I now only go to full throttle for take-off or a brief acrobatic maneuver such as a climb for a loop, and when completed I reduce throttle. It is important to use the speed controller as a controller and not just as an on/off switch as far too many pilots do. Throttle management is easier on the batteries and produces longer flights.
With the plane working perfectly I was able to enjoy my flights even more. The plane took-off easily and flew exactly as I directed it in the sky. Go to full throttle and I had a nice loop and eased off the throttle. Axial rolls were literally a snap (pun intended). Barrel rolls required a little more finesse with the blending of ailerons and rudder to get it just right but practicing is fun and easy and the plane comes back into line very responsively if I slightly miss a manuever. I liked doing tail overs in half pipes with the plane followed by an intentional spin in a dive and the Baron pulls out of it at the last (well not so last) minute. The landing was still a pucker factor but keeping it straight I have made every landing (fingers crossed).
CONCLUSION
The assembly of the model was really very easy and went per the instruction book. Pick your method of motor mount for the conversion and you can go with the thrust angles on the firewalls, as I did, or you can reduce the amount of right thrust some with no ill effect. I would stick with the amount of down thrust that they give, as that seemed to work very well. The plane flew just as great as an electric design, as it did in the original gas powered version. In fourteen plus flights to date there was only one bad landing (no damage), and that was when there was no breeze (shown in the last video above). Landings are best going into the wind and after making your final turn fly as straight as possible. Try and track straight down the runway and don't turn too soon or you will drag a bottom wing tip (as seen in the video). Take-offs were surprisingly easy, especially if there was a slight breeze to head into. The Fokker Dr. 1 with three plus wings (Don't forget the flying surface between the wheels.) has a lot of drag. Once the plane was airborne and a few feet off the ground I started clicking back on the throttle one notch at a time. The speed of the plane was only slightly reduced but the duration of the flight was lengthened considerably by reducing the power consumption. This was especially true with the use of Lipolys that can supply much more amp power then the plane needs to fly with 5s configurations. I just went to full throttle for acrobatics on the last few flights. Because the plane has no guide wires it was easy to assemble and disassemble this plane at the field. I loved not having to clean gas residue off of the plane when it was time to go home. I liked the versatility of using the Apogee batteries in series or in my harnesses for parallel. I have a large airforce and I will not be flying this plane every week, but I do plan to keep it hopefully for years to come. Being able to use the batteries as 3s2p or 2s2p packs in other projects lets me get much more use out of the batteries. For safety sake I never recharged the Lipoly batteries in the plane. I removed them through the middle wing slot and I am happy I didn't cut a special hatch into the bottom of the fuselage. If you go with Nicads get them in a brick pack to fit them as far forward as you can near the firewall, but remember you will need to add some cooling vent holes in the front and cooling vent exit holes behind the lower wing to get air flowing through the plane and over the speed controller. I have only shown pictures of the final vent holes/trench to avoid confusion on the amount I needed for continuous full throttle operation. You can probably make your exit holes look much nicer than my flying field, effort. Additionally, with throttle management you don't need as big an exit hole area. (I have since cleaned it up and painted the exposed wood a matching red. It really isn't noticed when the plane is flying.) The plane did fly fine with 14 or 15 nicads, exactly as promoted. I used 2400mA cells in my testing and test flights. Be sure you have the plane's C/G balanced for the type of battery pack you are using on a given flight. With testing complete I will only be using the Apogee Lipolys. My plane is balanced for the 5s2p pack, but if I add a second 5s2p combo to make it a 5s4p, I can fit them in and keep the plane balanced with one of the 2s2p packs going back under the pilot a bit with the wires forward and near the 3s2p pack to which it is wired in series. Remember to always charge the Apogee batteries in their original packs only as 3s2p or 2s2p packs. I found the $50.00 Hobbico charger got these packs to about 93-94% of full charge. Using the Astroflight 109 charger I could get them fully charged. The Astroflight charger can charge one of these packs 4 times faster then the Hobbico charger, but only charges one pack at a time, whereas the Hobbico charger can charge two packs at a time. This plane's a real eye catcher and a very good and easy flyer. I won't say it is easy to handle on the ground. It handles OK on the ground going into a little headwind, so long as you go straight. Don't be afraid of it on the ground, just keep it straight. The combination really works very nicely and with the proper cooling the motor and speed controller are well matched for powering the plane. An intermediate pilot can handle this plane but the people watching at the field will think he is an expert...as long as he is straight on his landing.
THANKS
I want to thank Fred Bronk for help with the motor mount and for allowing me to bounce ideas off of him and getting good straight answers. I want to thank Jeff Hunter for being my test pilot so I could videotape the first several flights of the plane. I want to thank Bill Birmingham for his help with the versatility of the Apogee battery packs and his "long distance" encouragement. Being able to easily reconfigure the arrangement and break them down for charging allows me many more opportunities to use these battery packs. It also allowed for versatility in testing at different voltage/wattage. I want to thank Dick Andersen for use of his Astroflight 109 charger and someday I may return it to him if Santa brings me one of my own. I want to thank my wife, Star, for tolerating me and my mess as I worked on the problem solving portions of this review. Of course, thanks to Great Planes for this great project! Finally, my thanks to AnnMarie for her assistance on this review.
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Aug 14, 2004, 12:09 PM
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#2 |
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I plant balsa sticks too
Join Date: Feb 2000
Location: France
Posts: 3,575
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nice!
I did also a conversion with an HP motor in 5S2P (without any lead in the nose!) see details here http://www.rcgroups.com/forums/showt...&highlight=DR1 |
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Aug 14, 2004, 05:32 PM
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#3 |
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Registered User
Join Date: Apr 2001
Location: Stockton, Ca. USA
Posts: 6,627
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Dear Luc:
Very creative to make the platform for the batteries out in front of the firewall. Now that I have seen your pictures I realize that would be easy to do with the Kontronik motor and avoid the need for the lead. The speed controller could be mounted out front as well and hidden by the cowl but still getting the air flow it needs for cooling. Plane would fly even better at a pound lighter. Thanks for sharing what you did. Mike Heer 
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Aug 15, 2004, 07:01 AM
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#4 |
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I plant balsa sticks too
Join Date: Feb 2000
Location: France
Posts: 3,575
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My controller (shulze 18 61 opto) is just behind the motor but still in front of the firewall, so no special cooling is needed. also , I used an sbec (2g) to save the weight of the Rx battery and HS81 mg servo. AUW with 5S2P Irate 2200: 3800g = 8.4 pounds
Last edited by luc; Dec 03, 2004 at 12:31 PM. |
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May 10, 2008, 08:34 AM
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#5 |
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Registered User
Join Date: Apr 2001
Location: Stockton, Ca. USA
Posts: 6,627
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Well this beautiful bird is flying better then ever with a new Common Sense brick battery pack. I have replaced most of the nose lead that was on the motor mount with a 4" speaker mounted to the firewall. She now flies with the RC Aerosound system installed. Mike
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