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| Scale Aerobatics Scale Aerobatics/IMAC in Canada |
Topic Review (Newest First)
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| 09-01-2020 01:19 PM | |
| Trumpetman |
Re: IMAC DR-107 One Design Build Aaah, my head is starting to swell  There is always a transition involved with going from .60 nitro plane to 50cc aircraft. You are doing great and I’m looking forward to seeing you kick butt with that plane.
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| 08-31-2020 10:33 PM | |
| Christavia |
Re: IMAC DR-107 One Design Build Thanks for the kind words. Unfortunately, last weekend’s IMAC competition as weathered out... but there’s another one this Saturday! Hope to compete with it then!!! |
| 08-31-2020 04:47 PM | |
| Randy Brown | Loved my tbm One Design |
| 08-29-2020 07:47 AM | |
| scaleguy |
Re: IMAC DR-107 One Design Build Ken glad to hear you've worked all the kinks out. Gord is a good IMAC mentor. Yes Tom at TNT is a great guy to deal with I've been to his shop many times and probably bought a good 10 or so gear from him over the last 15 years or so. Glad to see you are finally able to enjoy the fruits of your labor. Have fun with your new IMAC career. |
| 08-28-2020 09:19 PM | |
| Dennis Pedersen |
Re: IMAC DR-107 One Design Build Well Ken, hopefully the next 1,000 flights will be trouble free ! Plane looks great. |
| 08-28-2020 08:25 PM | |
| Christavia |
Re: IMAC DR-107 One Design Build DR-107 Revisited So, my last post was a little over a year ago and a lot, and a little has happened with this plane. There’s been a lot of work and only a little bit of flying. Sorry, this one is a little long, but it has been a while  First, it turns out that my receiver was just fine. The problem with the engine turned out to be a failing solder joint on the high tension lead from the ignition module. It was creating enough EM noise that the throttle and choke servos were jumping around. Fortunately, I have a second DA-50 and robbed the ignition module from it to swap into the DR-107. Problem solved. Last fall I shipped the module back to DA and they repaired it for free. It only cost me the shipping from Calgary to DA. Fantastic service on a 10+ year old engine! The second issue has more to do with me than the plane. Out of the four flights I did last summer, only the first one ended up with the plane still standing on its gear. The second and third had the plane over on its back with a broken prop… the fourth ended when the left wingtip touched the ground and the gear tore out of the plane and a broken prop! Fortunately, it was a fairly clean break and was easy to repair. The issue was two-fold. First, this is only my second foray into the gasser world. The first being a DynaFlite 89” Super Decathlon. That plane flies much like my nitro planes… approach slow at idle, nice high flare and three-point the landing. Unfortunately, this absolutely does not work on a plane like the DR-107. The higher wing loading requires an airliner-like approach: low, shallow with about 1/4-1/3 throttle. There was definitely an expensive learning curve experienced here  . Fortunately, my coach Gord figured out what I was doing wrong and advised me on what I needed to do. The second issue was my choice of landing gear. The original plane had 3” wheels at the bottom of 6.75” gear. Since I couldn’t find an exact match in carbon fiber, I went to an 8” gear leg. I also decided to use 4.5” wheels due to our field conditions (it’s also closer to scale size). This resulted in a gear that was 2” taller. Bigger is better… right? Maybe not! I ordered a new carbon fibre gear that is only 6” tall which, with the 4.5” tires, will put the height back to stock. My reasoning is that the taller gear has moved the center of gravity up quite a bit making the plane want to tip forward more. Also the longer rear has more leverage on the attachments which contributed to the loss of the gear on the hard landing. I also ordered a new Seacraft tailwheel when I noticed that the budget tailwheel fork had broken off (likely due to my somewhat hard landings  ).By the time I repaired the plane, winter had set in and I would have to wait until summer to try out my fix. I started out the summer by hauling out the Decathlon and practicing the landing technique Gord had suggested. It took a bit of concentration, but I finally had the airliner approach perfected on the forgiving Decathlon. I met with Gord one fine evening and had two great flights with the plane. The landings were good and Gord’s tutelage was definitely helpful. About a week later, I was at the field again with Gord and another IMAC team mate Rick. For my first flight, there was a definite right crosswind from the so Gord reminded me that right rudder was going to be my friend on this approach. Following his advice and keeping the speed up, the plane settled onto the ground with the right wing just a little bit low and the right wheel touched first. It did a slight bounce and the left wheel was down. It appeared to be a good landing! The only thing was, there had been a small, black object, about 4-1/2” in diameter, which bounced away from the plane. I immediately realized that it was the right wheel!!! Fortunately, the plane was running on the left wheel with the right gear leg off the ground. I tried to keep the right wing up, but I ran out of airflow and the gear touched down dragging the plane to the right and… BREAKING ANOTHER PROP!!! The three of us went to inspect the damage and found the plane intact except for the prop and the gear leg. My first thought was that the attachment hardware had loosened off, but the wheel was still attached to the axle and the axle nut was still in place. When we checked the gear leg, it became obvious what had happened. The leg had split along its length from the axle to about halfway up the leg. It likely occurred since I had been crabbing slightly to the right when the plane touched down. Both Gord and Rick agreed that the landing was good and should not have caused this damage. Fortunately, everything else was fine. Back to the drawing board. Since I was happy with the gear geometry, I decided to order a new gear from TNT Landing Gear. TNT specializes in aluminum gear and were quite helpful in helping me design a custom replacement gear. It took about 3 weeks to show up. It was an expensive fix ($70 USD for the gear and $40 USD for shipping) but wasn’t time consuming… just drill, bolt and go. So, for anyone keeping tally, that was 8 flights, 4 broken props and 2 broken landing gear. Not a stellar performance by any means! Fortunately, the aluminum gear was just what the plane needed. I’ve since logged another 10 flights… all on the same prop and landing gear.Despite the ordeal, I love how the plane flies. It’s my first, true IMAC style plane and I finally understand that bigger IS better when it comes to RC planes. I hope to fly it in competition next weekend and will see just how well I do with it under pressure. The first picture is with the ill-fated short CF gear and the second shows teh break it suffered. Third picture is of the plane in its current configuration! |
| 07-12-2019 11:00 AM | |
| Christavia |
Re: IMAC DR-107 One Design Build It finally flew! The initial flights went well, but clearly indicated that I should have built in some right thrust as it pulled to the left quite a bit. The DA-50 is providing plenty of power using a Menz 22x8 spinning at 7050 RPM. Our club IMAC guru, Gord, flew the first flight and I did the second after our IMAC competition this past Saturday. However, I noticed a bit of a burble in the mid RPM range. Thinking that the newly rebuilt engine still needed tuning, I brought it in and spent a good chunk of the following morning trying o tune it. We were waiting for a low cloud cover to lift and I had several pilots available who all have more experience on gas engines than I do. We decided that the engine tune was good and the mid-range burbling was likely just a function of the rebuild and would likely work itself out with some more flying. On Monday night, I pulled the engine and fuel tank out to add a couple of 1/8" spacers behind the right mount extensions giving me about 2.4 degrees of right thrust. You can see the change in the last two photos.I haven't offset the cowl yet as I want to wait until I'm happy with the offset before I glass in the original mount holes and drill new ones. Last night I decided to bring the plane to the Stampede field for our IMAC night and get a few more flights in. The engine fired up normally but still doing its routine burble thing. The range check was fine with the engine running. Before taking the runway, I did a full power run. All good. However, when I pulled the throttle back, the engine stayed at full power for 1-2 seconds!!! Something wasn't right! I shutdown and had a peak at the throttle pushrod. It appeared to be working normally. I fired up again and had the same hesitation when throttling down. I pulled the cowl off and ran it again. With the engine running, there was an obvious uncommanded movement in the throttle servo and is jittered away! However, it wasn't just the throttle... the choke was also jittering and the ignition light from the Ultra iBEC ignition switch was flickering! essentially, I was getting extreme interference on three channels, but the 5 flight channels were fine. That sparked a couple of hours of troubleshooting where everything but the servos and receiver were swapped or removed from the equation. Finally, I packed up, went home and swapped the receiver with a new Optima 9 spare. Suddenly, all the problems were solved INCLUDING the mid-range burble! The jittering of the throttle in the sensitive part of the throttle curve was the cause. Since the receiver was only failing with vibration, I added a little more foam padding around the new RX and I'm looking forward to flying it again tonight. |
| 02-13-2019 12:04 AM | |
| Christavia |
Re: IMAC DR-107 One Design Build I actually used AutoCAD. I already had the drawings done in AutoCAD and just used the solid hatching function to colour it. |
| 02-12-2019 08:49 PM | |
| scaleguy |
Re: IMAC DR-107 One Design Build Ken, Nice Job. Way back when you revealed your colour scheme you had a three view drawing showing the scheme. Did you just take a 3 view drawing and use what program to colour it in, MS PAINT? or something? |
| 02-11-2019 05:02 PM | |
| Randy Brown | The da 50 is going to rip it apart, tbm use to sell it and I owned the game me design matter of fact still have it, I competed it in many contests when I started iMac with a Moki 1.8 and I could have tore it apart easily if didn’t watch throttle. Just warning you |
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