Product Review:
Cermark 87" Yak 55
Perspective By:
Steve H.
Manufacturer Contact:
If you have any questions or concerns and would like to contact CERMARK, you can Email us at: services@cermark.com
For inquiries regarding sales, web alliances and business development opportunities, Email us at:
Manufacturer Website:
http://www.cermark.com/
FlyingGiants Ratings:
| Packaging: |
 |
| Kit Quality: |
 |
| Ease of Build: |
 |
| Huckability: |
|
| Overall: |
|
|
The Yakovlev Yak-55 and 55M (short wing) is an aerobatic aircraft designed by Slava Kondratiev. It has a thick mid-mounted symmetrical wing and is of a conventional monocoque all-metal construction. The undercarriage is fixed with sprung main gear and tailwheel. The engine is a 360 horsepower Vedeneyev M14P. The prototype first flew in May 1981 and was shown to the West in 1982. However, the Russian aerobatic team did use the aircraft until 1984 when they won the World Aerobatic Championship. The aircraft has been relatively free of Service Bulletins (Airworthiness Directives) and has proved exceedingly effective in competition at all levels. The obvious capabilities of the aircraft and its success in use, together with the relatively large numbers built (some 250) has meant that owners make relatively few modifications and that few are needed. The cockpit is roomy (but a bit short in leg length), and the aircraft is a delight to fly although some say it is difficult to land neatly, thus affectionately nicknamed the crop duster. (From Wikipedia) The Cermark Yak 55 is modeled after this rare full scale plane, and I jumped at the chance to review one. Since everyone has a Yak 54 or Extra it was nice to see a "new" model in the 50cc class. |
Kit Contents The kit includes Pre covered wings Fuse Horizontal stab/Elevators Rudder Fiberglass Cowl Fiberglass wheelpants Plastic Hatch/Canopy Hardware package Aluminum Landing gear Decal sheet Carbon Fiber wing tube Fuel tank Kit Requires 5 High Torque servos and one standard for Throttle 50CC Class Engine Prop/Spinner 18", 12" Servo Extensions and Switches 6 Channel Radio system Misc. Building supplies
| Wingspan: | 87" (2210mm) | | Wing Area: | 1451 sq. in. (93.6sq. dm.) | | Weight: | 15-17lbs (6800-7600g) | | Length: | 80 5/8" (2048mm) | | Servos: | 150oz or better servos | | Transmitter: | Futaba 14MZ | | Receiver: | Futaba R608FS 2.4ghz | | Motor: | 3MM 53cc TOC | | Available From: | Cermark | | Price: | $549.99 |
The manual is Written fairly well, although it is a general manual for the line of 50CC models they offer and some steps don't apply, and some are missing. (Wheel pants install for the Yak 55 for example) The assembly begins with hinging the control surfaces. The included "Robart" style hinges are included, and instead of 30 minute Epoxy I used Pacer hinge glue; the cleanup is much easier and it has never failed me. One of the Elevator hinges needs to be cut as seen in the picture so it doesn't hit the stab joiner. Wing I finished the wings next, but the manual lists them as one of the last steps; I just like to work on them first and get the easy parts out of the way! I first mounted the aileron servos. The manual shows the control arm closer to the hinge surface, but in the next picture it shows it farther from the control surface. I had my servo mounted like the first picture in the manual, but had to remove it to flip it around because the included linkage would not fit. The Blue servo arms were not mentioned anywhere in the manual. I chose not to use them because I don't like mounting a metal arm to a plastic arm; Previously I have had them strip out the plastic arm. The Aileron hinge gaps were sealed with clear Ultracote which seemed to stick well to the covering on the Yak. Fuselage I mounted the scale wheelpants to the gear and then to the fuse. The wheelpants are a lot stronger than typical wheel pants, and they are securely mounted. The Tailwheel assembly mounted as seen in the picture. There is very positive control with this type of system. The Elevator servos mounted in the stabs, and I had to route out a lot of wood for them to clear. If I had used the taller blue arms were used, I would have had to route out even more. Although I said I don't like using the metal arms mounted to plastic ones, I did use the included one on the rudder because I did not have a long enough servo arm. The included pull-pull setup did not include the tiny spacers to keep the ball link from hitting the servo arm, I used some that I had in my parts box. The metal ferrules were also too large for the included wire, so again, I used some that I had on hand. I put one wire on top of the arm and one on the bottom to keep them from rubbing against each other since they cross in the rear of the fuse.
Next, I mounted the 3MM TOC 53CC engine to the firewall. The kit includes a template for a 3w and a DA-50 engine, but doesn't include one for the recommended 3MM Engine. The engine comes with its own template, and I used that to position the engine on the firewall. | 
3MM TOC 53CC engine specs | | Type: | Gasoline | | Displacement: | 53cc | | Horsepower: | 5.5 | | Weights: | Engine Only - 3.1lbs | | Carburetor: | (Included) | | RPM: | 1,200-7,800 | | Fuel: | Gasoline/Oil mix | | Crank: | 3 ball bearings (nsk) | | Ignition: | 4.8~6.0 volt | | Props: | Blade,22x8,22x10,23x8,24x6 | | The manual did not say what size standoffs to use, only that the backplate of the spinner should be 2mm from the front of the cowling. 2mm is way too close and would not look scale nor work very well with the round cowl. I used 1 1/8" standoffs which put the spinner about a 1 1/2" from the front of the cowling, and it looked perfect. Our field has noise restrictions on anything 50cc and larger, so I used a canister muffler with the 3MM engine. The Yak 55 has a tunnel in the fuse for a canister, but it was too short for the commonly used K+S Canister I was using. I'm not sure what brand of canister it was made for, so I had to cut the back of the tunnel out, and extend it so that the canister would fit properly. The Engine did come with a nice looking side mount
Mounting the cowl was somewhat difficult; my cowl was warped and would not fit on the fuse easily. I was told that they had no replacement parts and could not send me another cowl. One of my cowl mounting tabs on the fuse was also missing, so I had to make a new one. I also made a baffle in the front of the cowling to force air over the cylinder head. This is a good idea to make sure the Engine gets proper cooling and only takes a few minutes. My canopy/hatch was also warped badly and would not mount to the fuse. Again no replacement parts were available, so I soaked mine with water, forced it on the fuse and let it dry for a couple days. This got most of the warp out, but I still have to push down on it to get it mounted. The manual says to "bind the fuel tank with nylon strips" but there were no nylon strips included, nor was there any place to "bind" them, just a flat area where the tank should sit. I made a small tray from lite ply and used tie wraps to secure the tank to the tray. There was nowhere to mount the switches in the fuse since there were so many lightening holes. I had to cut a piece of ply to fit inside the holes so I had something solid to mount them to. I used one 2300mah A123 receiver pack on the Futaba 8 channel FASSST 2.4ghz receiver, and it works perfectly: There are no regulators to mess with, and it can fast charge them in 10 minutes. The pack was mounted right behind the fuel tank on another tray I made. I mounted the throttle servo in front of the fuel tank with the wood mount that was included. I use an electronic switch on all of my gas planes to kill the power to the ignition in case a throttle servo fails, linkage falls off or breaks or any other reason I would need to kill the engine from the radio. The ones I use are the RC100X from here here.
I finished up the Yak 55 with the decals. They did not match any picture I found online or in the manual of the Yak. There is a bare spot on the side of the fuse that the online picture shows with a number decal, but none on the included sheet would fit inside the opening.. None of the Decals really seemed to fit the Yak very well so I just applied one to the wing. Flying I took the Yak out to the field with a fresh gallon of fuel and the oil mixed at 25:1 ratio per the engine manual. This seemed like too much oil to me, and I later switched to 32:1 for break in. The control throws were set per the manual, and the CG was perfectly at 6" from the leading edge of the wing at the root. The AUW with no fuel was a touch over 18 pounds, 1.2 pounds over the highest weight in the specs, and I used a light setup. Here are the throws from the manual: Aileron low rate 20 degrees and 25% expo Aileron high rate 40 degrees and 45% expo Elevator low rate 20 degrees and 25% expo Elevator high rate 40 degrees and 45% expo Rudder low rate 30 degrees and 30% expo Rudder high rate 45 degrees and 45% expo The control throw settings were a good starting point, and I later increased the high rates to all I could get on the surfaces. The 3MM took about 20 flips before firing up for the first time, and I used a 22x10 which the manual calls for. I used a Troy Built Models (TBM) prop. for break in. The Troy Built Models Beechwood Props are very nice and priced right. It was almost perfectly balanced. They have sizes for 40cc up to 150cc, and I highly recommend them. Take off was very easy with only minor rudder correction. The Yak flew with almost no trimming needed and felt perfectly balanced; only a touch of down elevator was needed for inverted flight.
Aerobatics/Special Flight Performance I noticed the power was lacking in any kind of hovering or 3D so I landed to check out what could be the problem. I tached the 22x10 at 5800RPM on the ground, which is not enough RPMs to get the thrust the Yak needed, and from reading other posts on the Internet was lower than others with the same engine. I switched out the prop for a Vess 23A which is a good match to other 50cc class engines. I also removed the spinner. which yielded a increase to 6200 RPM, so I went for a few more flights. The Yak would now hover but not really pull out of one. I switched to a Vess 22A, and the 3MM turned it at 6800RPM which is closer to where it should be. I have also read that Wildhare sells a Hop Up kit for these engines that is supposed to increase RPMs by a couple hundred, but I have not tried one. I still have not had the confidence to get down low with it. I think the weight is a little on the high side to pull out with a lot of authority. The Yak 55 flies very well, even better than the Yak 54s I have had and flown. It will knife edge either direction with almost no coupling, and it locks in place. Harriers do have some wing rock but with spoileron mixing that goes right away. You can see in the video that when the wings are rocking, I hit the switch, and it locks in. Inverted flight is just as easy as upright flight with only a touch of down needed. The Yak 55 does a nice Blender and inverted flat spin, although upright flat spins were not very flat. It seemed to do rolling circles almost by itself with hardly any rudder needed. I noticed after my first 3 flights that the gear was loose. Upon further inspection I saw that the gear plate that they bolt into looked like it was never glued at the factory and was not aircraft ply but a 3 or 4 layer lite ply. I beefed up the gear with some hardwood blocks underneath it, and if you do not use a canister muffler you could put a piece of ply across the 2 sides which would make it even stronger. I suggest you look at your gear plate when building the model. Landing the Yak is as easy as lowering the throttle after making a final turn and guiding it to the runway. The Yak slows down nicely for 3 point landings, and I did not notice any bad tendencies like trying to tip stall or snap.
Conclusion The Yak 55 from Cermark is a great flying plane. I had a few issues, but a builder with some experience can overcome most of the difficult areas. I like flying the Yak 55 over my Yak 54s, it just feels like a smoother flying airframe to me. All of the guys at the field didn't know what a Yak 55 was, and they were all really impressed with the looks and flight of the Cermark version. Pluses: - The Yak 55 flies very well
- The covering scheme is sharp looking
- The scale fiberglass wheel pants really hold up to grass fields
- Carbon fiber wingtube and excellent hardware package
Minuses: - Nowhere to mount any of the switches
- Plastic canopy and cowl were warped on mine, and there were no replacement parts
- Must cut away sheeting for the elevator servo arms to clear
- It was 1.2 pounds over their highest recommended weight even though I went light on all components
- The manual is a general one for all of the 50cc models. Some steps are not in it, and some do not apply.
- The gear plate seems to be loose after only 2 flights with perfect landings, and it isn't easy to access
|
| If you have any questions or concerns and would like to contact CERMARK, you can Email us at: services@cermark.com
For inquiries regarding sales, web alliances and business development opportunities, Email us at: http://www.cermark.com/
|
|
11-28-2008, 09:08 PM
Re: Cermark 87" Yak 55 ARF
Similar Threads
