| As a novice wannabe RC pilot, I have suffered two | | | | wheel collars and also the engine-mount nose-gear |
| fatal plane crashes in my short flying career. The | | | | holes so everything would fit. |
| crashes were due to radio failure: the communication | | | | REBUILDING THE SERVO TRAY |
| between the transmitter in my instructor's hands and | | | | The servo tray also had to be replaced. Although |
| the receiver in the aircraft failed and not even my | | | | some might consider this an overbuild, I used a piece of |
| experienced instructor was able to save the planes. | | | | 1/4" plywood for the tray. First, using some card stock, |
| Experienced pilots told me that crashes happen to all | | | | I made a template of the tray and then cut out the |
| pilots sooner or later. So, I was prepared, mentally, for | | | | plywood tray with a jigsaw. Finally, I drilled holes for the |
| a crash, especially after my instructor saved my | | | | servo screws with a 5/64" drill bit. |
| aircraft numerous times--when I placed the aircraft in | | | | FIXING THE WING |
| jeopardy during my training sessions. Some aircraft | | | | Only a little CA was needed to repair the wing. |
| crashes result in a total loss of the plane; other | | | | However, a new arrangement was required for the |
| crashes result in varying degrees of damage that can | | | | wing positioning dowels. I epoxied a block of balsa to |
| be repaired. | | | | the bottom leading edge of the wing and epoxied two |
| My first crash, a Great Planes Easy Sport, resulted in | | | | positioning dowels into the block. I built a new plywood |
| a total loss on June 6, 2009; my second crash was in | | | | former to accept the dowels and epoxied it into the |
| November, 2009, and resulted in fixable damage. I | | | | fuselage. This arrangement made for a much more |
| decided to fix the damaged trainer, a challenging | | | | secure wing than the old, weak arrangement. I reused |
| project considering my building experience, small | | | | the original DU-BRO wing hold down blocks for the |
| workspace, and tool inventory. My last model building | | | | trailing edge wing bolts. |
| was done nearly 50 years ago, and building materials | | | | REMOVING THE OLD COVERING |
| and techniques have changed drastically since then. I | | | | At this point, I decided to remove the old fuselage |
| considered fixing the trainer to be a great learning | | | | covering. Since I had never done any covering and did |
| opportunity for building and repairing my RC aircraft. | | | | not have any of the necessary tools, I visited club |
| Fortunately, I belong to an RC club, Sanderson Field | | | | members to learn as much as I could before ordering |
| RC Fliers, and club members helped me throughout the | | | | tools and materials. Eventually, I removed the covering |
| project. Collecting the necessary tools and materials | | | | and then removed any leftover adhesive with Methyl |
| and effecting the repair was done over a period of | | | | Ethyl Ketone (M.E.K.). Once the old covering was |
| several months; an experienced modeler with the | | | | stripped, I could clearly see other areas that needed to |
| necessary tools and materials could probably have | | | | be re-glued or strengthened. |
| completed the repair in a few hours. | | | | SHEETING THE STABILIZER AND VERTICAL FIN |
| THE DAMAGE | | | | One area that needed to be strengthened was the tail. |
| The damaged trainer was a Tower Trainer 40 ARF | | | | The stabilizer and vertical fin were not mounted |
| (Almost Ready to Fly) which was given to me by | | | | securely. I decided to sheet the surfaces with 1/64" |
| another club member. The nose section needed a | | | | plywood and reinforce the joints to the fuselage with 1 |
| complete rebuild, as did the wing mounting and other | | | | 4" triangular balsa. Previously, I had to balance the |
| areas of the fuselage, such as the main landing gear | | | | trainer with a good deal of lead weight attached to the |
| area. The covering also needed lots of repair work. | | | | tail. I calculated that the weight added by the |
| Fortunately, except for some trailing edge damage, the | | | | strengthening could usefully replace some or all of the |
| wing was in good condition. | | | | lead weight (in fact, when the repairs were completed, |
| REPAIRING THE NOSE SECTION | | | | the plane balanced almost perfectly). Before sheeting, I |
| Early in the project, I decided to replace the standard | | | | cut away the solid-balsa rudder and elevator: these |
| clamp-type engine mount with a Great Planes.46-sized | | | | would be replaced and re-hinged later. |
| engine mount. This would require plugging old mounting | | | | I used thin CA to attach the first side of the sheeting: I |
| holes and drilling new holes for the Great Planes | | | | could reach all contacting surfaces through the open |
| mount. My first step was to remove the old balsa | | | | side. In order to attach the second side, I first attached |
| from the bottom and top of the nose section. After | | | | the trailing edge and allowed the CA to thoroughly set. |
| drilling the necessary engine mounting holes and | | | | Next, working towards the leading edge, I applied thick |
| installing blind nuts for the engine-mount bolts, I | | | | CA to about 1/3 of the remaining contacting surfaces, |
| re-epoxied the existing engine firewall into place. I also | | | | held the sheeting down until the CA set, and moved |
| added a 1/16" thickness of plywood to the inside sides | | | | onto the next 1/3. The thick CA allowed me enough |
| of the engine compartment to stiffen the front end of | | | | time to quickly position the sheeting before the CA set. |
| the fuselage. | | | | I used an Xacto with a #11 blade to trim the excess |
| A club member drilled the engine mounting holes in the | | | | sheeting. Where necessary, I used additional thin CA |
| engine mount using his drill press and I tapped the holes | | | | around the edges of the sheeting. After sanding the |
| with a 6/32 tap: I used 6/32 socket head cap screws | | | | edges of the stabilizer and fin, the sheeting blended |
| to secure both the engine mount and engine. After | | | | nicely into the edges. When the sheeting was |
| coating the interior of the engine compartment with a | | | | completed, I added the 1/4" triangular balsa |
| thin coat of epoxy (diluted with 99% isopropyl alcohol), I | | | | reinforcement. |
| bolted the new engine mount to the firewall. My next | | | | COVERING THE FUSELAGE |
| step was to remount the fuel tank. | | | | After filling holes and gaps with either Hobbylite filler or |
| I glued some flexible tubing to the fuel tank cradle to | | | | DAP spackling and sanding everything smooth, I was |
| help dampen engine vibrations. On a tip from a club | | | | ready to begin covering with red and white monokote. |
| member, I used flexible tubing from a sling-shot repair | | | | Starting with the fuselage bottom, I covered the |
| kit purchased at my local Walmart sports department. | | | | fuselage. After covering the fuselage, I rated the job |
| Before installing the fuel tank, I painted the | | | | as a 10: looks good from 10 feet or more. My next job |
| compartment with a thin coat of epoxy for fuel | | | | should be better. |
| proofing. I also used silicon adhesive around the front | | | | NEW ELEVATOR AND RUDDER |
| of the fuel tank to further isolate the tank from engine | | | | I cut out a new rudder from 1/4" balsa; I used 3/8" |
| vibrations and seal the tank compartment from any | | | | trailing-edge stock for the new elevator. Hinging the |
| engine compartment fuel leakage. I covered the top of | | | | elevator to the stabilizer was not too difficult. I had to |
| the fuel tank compartment with a hatch made from 1 | | | | reposition the hinge slots on the old stabilizer because |
| 8" plywood and recovered the bottom of the | | | | the old hinges were still in the wood: I used an Xacto |
| compartment with new balsa. | | | | knife with a #11 blade to cut the new slots. I slotted the |
| NEW LANDING GEAR | | | | elevator leading edge to match. Because of the more |
| Since the landing gears, both nose and main, were | | | | limited space to reposition new hinges on the rudder, |
| damaged, they had to be repaired or replaced. I | | | | and on the advice of a club member, I elected to use |
| decided to replace the main 5/32" wire landing gear | | | | Hayes Live Hinges, which needed to be epoxied into |
| with a more durable "Super Strength Landing Gear" by | | | | small holes. In order to bevel the leading edges of the |
| DU-BRO. The DU-BRO landing gear is made from a | | | | elevator and rudder, I built a small bevel-sanding jig. The |
| shock absorbing composite material and will not bend | | | | bevel jig worked well for the soft balsa rudder but the |
| out of shape as the wire gear did. In addition, I planed | | | | hard trailing edge stock needed to be razor planed to |
| to use larger wheels for both the main and the nose | | | | the approximate bevel before final sanding on the jig. |
| gear: I decided to use 3-1/4" Dave Brown "Lite Flite | | | | After the beveling, I covered the surfaces with red |
| Wheels." I felt the landing gear upgrade would make | | | | monokote and then attached the rudder and elevator |
| the trainer more durable as I learned to fly--and would | | | | to the stabilizer and fin. |
| be a good setup for our grass field, too. Also, with the | | | | VOLTWATCH2 |
| upgrade, I thought the plane would track better on the | | | | It was necessary to replace the plywood windshield, |
| ground and, because of the added ground clearance, | | | | and I decided to mount the VoltWatch2 here. I use a |
| lessen the chance of damaging a propeller during a | | | | VoltWatch2 to monitor the receiver battery--a low |
| rough landing. | | | | battery level can lead to crashes! I cut a small slot in |
| In order to accomplish the upgrade, I first replaced the | | | | the windshield and mounted the VoltWatch2 under the |
| original main landing-gear strong point with a wider 3/8" | | | | slot. I covered the slot with a small piece of clear |
| plywood base for attaching the DU-BRO gear. | | | | monokote donated by a club member. Installed in this |
| Underneath the plywood, I reinforced the strong point | | | | way, the LEDs of the VoltWatch2 are protected and |
| with 1/2" triangular balsa. I used four 6/32" socket head | | | | the battery level can be easily monitored. |
| cap screws to securely mount the DU-BRO landing | | | | IN THE AIR |
| gear to the fuselage. The landing gear can be painted | | | | On March 30, 2010, my instructor thoroughly checked |
| and I plan to use a red spray paint for this sometime in | | | | out the trainer before we drove to the flying field. |
| the future. | | | | Once ground checks were completed, we flew the |
| For the nose gear, and to level the aircraft longitudinally, | | | | finished aircraft for two successful test flights. I would |
| I bent a DU-BRO "5/32 Universal Nose Gear Wire." | | | | like to thank the members of SFRCF, my RC club, |
| One problem with wire landing gear these days is that | | | | who helped me with this project. Special thanks are |
| commercial landing gear comes with a plating that | | | | due to members Bob Beatty, Richard Robb, and Bob |
| increases the wire diameter slightly. This creates a | | | | Andrew for their help, advice, and tips. |
| problem when using it with commercial parts, | | | | Copyright © 2010 Royce Tivel Select Digitals |
| engineered for 5/32" wire, such as wheel collars. I | | | | After the Crash - Fixing a Tower Trainer 40 ARF, |
| found I had to use a #20 drill bit to enlarge both the | | | | April 5, 2010. |