The EAM Mig 17

Ducted Fan columnist Chris True covers EAM's Mig-15, including some hop-up tips to make this little jet really scream

 

A few weeks before Thanksgiving I received an e-mail from Dave at Electric Aircraft Models (EAM) asking if I would be interested in receiving one of their Mig 17 kits for review. I didn't need to think about that offer for too long, I quickly replied YES.

The EAM Mig 17 kit is designed around the Kyosho fan unit. Alternatively, a Wemotec HW-609 fan can also be used, either the "Gnat Pack" version or the normal full length 609 should fit. I have tried the "Gnat Pack" and that fits with no problems. The Mig is a 225 square inch airplane, the fuselage is molded from fiberglass with the wings constructed from white foam cores skinned with 1/16" balsa. Just about everything you need to construct the Mig-17 is included in the box, with the exception of a Sullivan cable set to actuate the elevators. You need to supply the radio, motor, fan, battery, and covering material, of course. The kit also arrived with a fairly substantial step-by-step instruction manual, containing written instructions, 3-views, and various drawings bound in a red folder. No plans are supplied nor are they required. Various fuselage formers from high quality plywood or balsa are all cut to shape. Band sawed balsa for the tail surfaces and wing tips are also supplied. A clear canopy and cockpit base are included along with paper patterns for adding wing fences.

Construction

Fuselage

The fuselage is molded from polyester resin and appears to my uncritical eye to be quite scale. The fin is molded as part of the fuselage and the typical sugar scoop fairing is molded into the area between the fin and rear fuselage as an example.

The fuselage weighs 7.25 ounces as supplied. Adding the three duct sections brings the total weight of the glass moldings to 10 ounces. Some sanding of the join lines will be required as well as priming and painting the fuselage. The molding is not gelcoated.

The duct system is an interesting aspect of the kit. The inlet duct is a stiff glass molding to resist the suction on the inlet side and has a socket molded into the rear face to accept your Kyosho fan as a slip fit. The duct expands smoothly from the 62mm inlet diameter to the fan diameter over the length of a few inches; from that point back to the fan the duct is a constant diameter. The exit duct is also molded from glass, but is a much lighter lay-up since the exit side is under positive pressure. This rear duct ends well short of the front duct to allow you space to install your fan. The gap is bridged by a third constant diameter section of duct, with another socket to accept your fan molded on one end. This third section is a light slip fit in the exit duct. The idea being that you slip this all the way into the rear duct, install your fan, bring that third section forward to swallow the fan and secure the joints with tape. 90% of the inlet lip is molded into the fuselage. What remains for the modeler to do is to sand a slight curve from the inside of the inlet duct to the outside once the inlet is installed with a generous fillet of epoxy and micro balloons bridging the joint.

OK, first task is to take your nice new fuselage over to the kitchen sink and give the entire thing a good scrubbing with a scotchbrite pad and warm soapy water to remove the mold release. This mold release is all over the outside; if you do not remove it glue or paint will not stick. After drying the fuselage I laid out masking tape on the fuselage sides as a cutting guide for the removal of the hatch. Per the instructions, there are 4 indents molded in which define the corners of the hatch. After struggling with a not so sharp razor saw for the first long cut, I switched to a Dremel tool fitted with the thinnest cutoff wheel. The Dremel made quick work of the hatch cuts, although I did manage to break several wheels in the process.

Once the hatch is removed there are several formers to install. Former 1 is a 1/8" balsa partial former, which is easily installed with thick CA glue. Former 1 goes at the very front of the hatch area. Former 4 is next and gets installed at the rear of the hatch area. This one is a full former and requires some sanding for a good fit; it was 1/32" or so too large to begin with.  The former has a hole for the elevator pushrod on one side and not on the other side, so be sure to install it correctly as per the instructions. Former 6 is towards the rear of the fuselage and supports both the tail pipe and the fin. This former was also oversize and required several sand and fit iterations before a satisfactory fit was achieved. Both F-4 and F-6 were secured with a mixture of epoxy and micro-balloons. The micro balloons are supplied in the kit. Once these two formers are installed you need to measure carefully to cut the slots for former 3, which comes in two halves with stub spars which eventually support the wings. Before gluing this one in place, check the fit of the inlet liner; some sanding may be required. Once happy with the general fit, the two halves are joined with 2 pieces of 1/16" ply, which overlap the joint at the bottom. Later, after the duct is installed, the remaining open section of this former is bridged by a third former section which is glued in place.

The next major assembly milestone is to install the ducts, but first there are a couple minor items to tend to. The kit provides a 1/8" thick birch ply tow hook to use for bungee launching the plane. The ply hook fits into a slot at the bottom of the fuselage, which I routed out with a small spiral cutting Dremel bit. Glue the hook in with a generous amount of epoxy filled with micro balloons to limit the spread of the glue as it cures.

Since the inlet on the Mig is a little small at only 62mm in diameter, the kit is designed with a cheater hole to compensate for this. A hot wire cut block of white foam is supplied which fills the area between the duct wall and fuselage outside skin; glue this in place with epoxy before securing the ducts. OK, now we are ready for the duct installation. The rear duct gets installed first; secure it with a few dabs of 5 minute epoxy. Slip the rear duct extension in place, then test fit the front duct. You will want to check the fit of your fan at this point.  I needed to shorten the rear duct by a couple of inches to allow enough space for the fan to fit in the opening.  The rear duct extension is plenty long enough to bridge the gap required. Once happy that the fan will fit, mix up some 2 hour epoxy and micro balloons such that it will still run slowly. Apply a large amount at the nose where the front duct fits through, insert the front duct, tape the joint on the outside so the glue will not run out and stand the fuselage on its nose to cure.

The epoxy / micro-balloons mixture will slowly fill the first 3/16" of the front fuselage and duct wall area. Once this cures, you can sand in a slight rounded edge for a nice inlet. NOTE: Make sure that rear duct extension is in place before you glue the front duct in place; it can't be installed later!

Join the balsa pieces for the tail surfaces, sand to a pleasing airfoil shape and follow the remainder of the instructions. The fuselage has alignment marks for the elevator mounting slot. I used the 1/8" Dremel cutter again to route out this slot. Block up the fuselage securely such that the fin is perfectly vertical; this is one of the more difficult construction points because the fuselage is ROUND and not easy to secure! I used lots of foam bits and long lengths of masking tape. Once the fin is perfectly vertical test fit the stabilizer and make sure it is perfectly level. To glue the stab in place I mixed another stiff batch of epoxy and balloons. I used a small spatula to pile this up inside the fin on the skin sides ABOVE the stab slot. I then inserted the stab, blocked it level and let the glue settle into the joint. Once the glue had cured I removed the fuselage from the bench and did a similar operation with the fuselage upside down and used a thinner mix of epoxy / balloons inserted from the underside of the fin.

The wing cores supplied with the kit were of nice quality. Before getting to the wing skins you need to prepare the cores. The instructions give measurements for cutting the servo pocket in each panel as well as the location to cut a groove for the servo leads. The servo lead groove exits the core just behind the wing spar area. The balsa skins were reasonably light, and all the remaining parts were quite light balsa. The instructions advise securing the wing skins with 3M77 spray adhesive. I have used this method in the past, but I prefer laminating epoxy so that is what I used. With the epoxy you do not need to glue the skin panels together; merely tape them together with masking tape, squeegee the glue onto the skins, stack the cores on their beds, and weight down the stack with plenty of cinder blocks. The next day I had a nice set of wings ready to accept the leading and trailing edges plus an enormous wing tip block on each panel. I do have one complaint about the wing: the trailing edges at first appear entirely two short. It seems that sanding the upper and lower wing surface contours will result in a trailing edge thickness of almost 1/4". My first thought was to add some more wood, but when I held the wing up to the fuselage molded in wing root I found that the wing would then be too wide. It appears to me that the trailing edge portion of the wing cores are approximately 1/8" too thick. I solved the problem by aggressively sanding the skins at the trailing edge as thin as I dared then sanding at a slightly steeper angle on the last solid balsa portion. Not what I would prefer, but it worked out OK. I advise you to draw a centerline on the rear face of the trailing edge before you do this so you have a reference line to work to.

Once the wings are sanded to final shape it is time to cut out the ailerons, face them with balsa where required, and install hinges. The kit provides two sizes of telescoping aluminum tubing to use for aileron hinges, as well as control horns (by flattening the end and drilling a hole). I chose to use two medium Robart hinge points in each aileron instead of the tubing. The tubing would work just as well, but since I plan on keeping the Mig-17 for several years I was concerned about the tubing eventually wearing out. Similarly for aileron control horns I chose to use convention nylon moldings sunk into the surface. My aileron servos are 2 Hitec HS-81's.  The linkage from the servo to the control horns are short lengths of 2-56 rod with one threaded end and one "Z" bend end. NOTE: as noted on the drawing, the servo needs to be square to the aileron hinge line, not the direction of airflow. Failure to do this will result in a lot of problems when hooking up the controls. Once you are happy with the ailerons, you need to carefully finish sand the entire wing, paying particular attention to making the root area match up with the fuselage fillet.

Using a razor saw, carefully cut a slot in the wing root to accept the plywood stub spars from the fuselage. Allow plenty of clearance; we will fill the slot with epoxy / micro-balloons and sand it flush with the surface later. Block up the fuselage in a level position again and check that the wings have the proper anhedral.  When fitted tightly against the wing root fillets, some adjustment may be required. I had some difficulty in attaching the wings until I came up with an aid to keep the incidence correct while I set the anhedral. What I did was use two broken golf tees as incidence pins. I drilled holes in the fuselage which were a snug fit on the tees, then I cleared out enough foam in the area of the core where the pins were for clearance. I slipped some little 1/64" plywood "washers" on the ends of the pins and with a thick dab of epoxy/micro-balloons in the core hollows I taped the wing in place at the proper incidence until the glue hardened. Once the glue was set I was able to remove and reinstall the wing panel easily at the correct incidence. When doing the second wing panel I checked the incidence carefully against the first panel using a Robart incidence meter. The molded in fuselage wing fillets were at the same incidence.  I was concerned that the wing roots when simply matched to the fillets might not accurately set the incidence, but it turned out that that was not a problem. Making sure the fuselage is still blocked up perfectly vertical, fill the spar slot with epoxy / balloons and coat the root generously. Slip the wing in place and secure with tape on the top and bottom of the wing fuse joint and the spar slot, then check that the anhedral is correct again before the glue sets.

Install the elevator horns and cables as directed. I initially thought I was smarter than the designer and tried to use the larger diameter Sullivan cables as well as some control horns I had in stock. There were two problems: the larger diameter cables were too stiff due to the tight bend involved, and I installed the horns too close to the hinge line. This is not a conventional elevator linkage installation. The hinge line is swept, resulting in considerable side to side motion of the control horns. Read the directions and follow them exactly using the materials called for and/or supplied. Once I did this the elevator linkage worked fine. I used a JR micro servo on the elevator which gets screwed to a plywood tray and glued to the front inlet duct.

Power System

The Mig is designed to fly satisfactorily with a Kyosho fan, AP-29L motor and 8-9 "A" diameter Sanyo NiCads. After flying my Mig with a much heavier power system on only 8 cells and moderate power input, I am sure the recommended setup will work fine. I chose the use an Aveox 1406/2Y motor installed in a Wemotec HW-609 fan unit. The 609 fan shroud is thinner than a Kyosho fan, so to install it you first need to build up the diameter of the shroud with several wraps of masking tape on the front and rear of the shroud until a slip fit is achieved with the ducting. For the first series of flights the Mig was outfitted with the 1406/HW-609 motor/fan set, an Aveox EZ-30 ESC, and 8 zapped Panasonic 2000 NiMH cells. This combination resulted in an all up weight of 45 ounces and power ranging from 280 watts hot off the charger to 225 watts towards the end of the charge. Later the battery and ESC were changed for more exciting performance. The second setup was 9 2400 mAh Sanyo NiCads and a Schulze Future 45bo sensorless ESC. This second setup also required a separate Rx power pack, since the Future controller was not equipped with BEC. The all up weight of this configuration was 54.5 ounces with input watts ranging from well over 400 watts hot off the charger to 360 watts near the end. Static current draw started at 45 amps and stayed above 40 for a full 2 minutes of the discharge.

First Flight!

I say first flight rather than test flight, because there really weren't any problem areas on the first flight - it isn't always that way. The plane weighed 45.5 ounces with the following equipment:

• Aveox 1406/2Y & EZ 30 controller
• 8 of Greg Kamysz's (www.sms.com) zapped 2000 NiMH cells (1250 SCR size)
• Wemotec HW-609 "Gnat-pack" fan
• 2 HS-81 Hitec micros on ailerons and a JR hi-torque micro servo on elevator.
• JR 9 channel credit card style receiver.

The flying surfaces were covered in silver Ultracoat, but the fuselage was unpainted for the first flights. Initial current draw on the 8 cell setup is 32 and 285 watts fading to 27-28 and 240 -250 watts for a good part of the charge.  There was a strong but steady breeze with temperatures in the low 40's. I set up my bungee stakes, then left the bungee in the warm car while I charged up the Mig-17. Once a glow Ugly Stick landed, I brought out the bungee and hooked up the Mig for launch. I'm using the Glockner heavy duty bungee with their foot pedal release, which works well. The plane sits on the ground for launch but lifts off within 5 or 6 feet. I run the motor up to 10% power before stepping on the release. In case of any grass ingestion I think it is better to chop it up as it comes in rather than build up a big clod.

I stepped on the release and hit full throttle as it came off the ground. The Mig came off the bungee straight as an arrow in a fairly aggressive, but not steep, climb. I let it climb without adjusting the trim since it was probably due to extra launch speed. After gaining about 80 feet of altitude I initiated a gentle left turn, which went fine. It tried to flatten out part way through the turn but a little more aileron fixed that. Coming back down wind it was looking good and moving pretty fast for only 100 or less watts per pound. I flew race track circuits for a while getting the feel for the handling characteristics. The roll rate is modest; not fast at all considering the larger 3/8" throw each way recommended in the instructions. The ailerons are only 8 inches or so long. though. The plane handles a lot like a Robbe Gnat; their sweep angles are pretty similar and they both have airfoils with a fair amount of camber. 1.5-2 minutes into the flight it was going well and the plane felt solid so I tried a loop as I was flying downwind. The Fresco pulled up into a large loop and started to lose speed at the top. As I came over the top and started down I rolled it upright and continued on the 45 degree downline to regain speed. A few more rolls and it was time to land. I throttled down to about 10% and flew the downwind leg. As I turned base and back into the very strong wind the plane seemed to almost stop so I brought the power up to half for most of the final approach. Crossing the fence @ 10 feet altitude worked well. 50 feet downwind of myself I started to flare, the nose came up nicely to bleed off speed. Touchdown was 75 feet upwind of where I was standing and was a greaser. Total flight time was approximately 3 minutes, with 30 seconds or so left in the pack. With only a few cycles on them I am getting approximately 1.6 amp hours from the NiMH's.

Over the next several weeks I put in a series of additional flights on the EAM Mig-17 with this power system, feeling out the plane's handling characteristics. The plane flies in a very solid manner; both the ailerons and elevators trim out at essentially dead neutral, which tells me the kit incidence marks on the stabilizer and molded in wing roots are spot on. I initially balanced the plane on the point called for in the plans, and I have not had a reason to change it. Flying the plane in calm air revealed a moderately fast approach speed; the wing loading at a flying weight of 45.5 ounces is fairly high at 29 ounces per square foot. However, the Mig-17 does fly a steady approach and I found it easy the land the plane within 50 feet of where I wanted every time at this wing loading. The approach angle is steep enough to make landings enjoyable without the added complication of flaps or mixing ailerons as spoilers.

Second series of flights with more power

My reason for using the Aveox 1406 series motor and HW-609 fan was always to step up to more power at a later date. My ultimate power system for the Mig consisted of the Aveox 1406-2Y motor powered by 9 Sanyo RC2400 cells using a Schulze Future 45bo sensorless ESC. The Schulze controller I have is not the BEC model, so I also needed to add a 350 mAh Rx pack. The Mig now weighs 54.5 ounces with this power system and all paint and markings added.

 

The wing loading is now up to 34.75 ounces per square foot, which is quite high. Anyone contemplating flying the Mig-17 with this power system should be very confident in their flying abilities. The excellent solid handling characteristics of the Mig still applies here; ripping along at full throttle the Mig is a joy to fly, but the landing approach speed is quite high.

The battery installation consists of several different sticks of cells slotted into various areas of the fuselage. Two 3-cell sticks fit in each wing root ahead of the wing spar former; behind that former is a 2 cell stick on one side and a single cell on the other. The Rx goes in the right hand wing root behind the 2 cell stick and the ESC goes at the rear of the fuselage compartment in the wing root behind the single cell.

The day to test fly the new power system had a medium speed breeze, about 12-15 mph blowing in variable directions and a temperature of 45 degrees. At the start of the fight the wind was down the runway, but when it came time to land it was cross wind, which made things a little exciting. I set up my Glockner bungee and slung the Mig into the air. Immediately the increase in power was obvious; the Mig was now very fast and would climb as fast as I wanted without losing much speed. After flying a few circuits, I pulled the Mig up into a very large loop, which it completed without any difficulty and with good speed at the top. The wind was blowing across the runway at this point, so some aileron correction was required to maintain the heading of the loop. The roll rate was now quite a bit faster than earlier due to the increase in speed, but still not so fast that I felt the need to rate down the throws. I had done a static discharge test before flying this combination and I knew my battery would last something over 3.5 minutes, so I had my timer set for 3 minutes. I had a great time cavorting about the sky in a carefree manner for 3 minutes, performing lots of rolls and a few loops for good measure. When the timer went off at 3 minutes I throttled way down to test the low speed handling, which was solid enough but not all that low <g>. I set up my landing starting at an altitude of 60 feet and flew a long down wind leg. Turning onto final I carried approximately 20% power until the field was made and then cut the throttle off. The wind was now blowing directly across the runway, so I dipped the upwind wing slightly, put the plane in a flare attitude, and kicked the wings level as it got close to the ground. The landing was uneventful, but a little longer than I would have wanted. In the future, if the cross wind is not there the landings will be much easier. I do have my JR 783 Tx set up to pop the ailerons up as spoilers in the landing mode, but  I have not yet found that necessary.  I may experiment with it in the future.

Conclusions

The EAM Mig-17 Fresco is a great flying little EDF. Designed around the stock Kyosho fan and motor powered by a light battery, the plane setup that way will be faster than a stock T-33 while still maintaining easy low speed handling. Setup the way mine is with the heavier but substantially more capable Aveox / Wemotec power system, the plane is capable of exhibiting really sterling performance.

Which power system you choose really depends on both your budget and your flying abilities. The flyer on a budget who already owns a Kyosho fan and fresh motor should not feel any great need to buy new equipment. The Mig-17 has a considerably smaller wing than a Kyosho T-33, which means the plane will fly better and more crisply on the same input power. For the stock Kyosho fan and ferrite motor I would stay with the manufacturers recommendation of 8 1000-1400 mAh AE cells to keep the weight under 42 ounces.

For the flyer willing to spend a little more money but still not wanting to go with a brushless power system, I would recommend the HP 200-25-4 motor in the Kyosho fan powered by 8-10 1250SCR cells or 2000 NiMH cells. With this system the all up weight should not be allowed to exceed 45 ounces for good performance and reasonably easy landings. Good but not exceptional piloting ability is required to land the Mig confidently at this weight. Another good choice in the same weight class would be an Aveox 1010/2Y motor in the Kyosho fan running 10 1400AE cells.

For the expert pilot willing to invest in a quality power system, the Aveox 1406/2Y and Wemotec HW-609 fan results in the highest level of performance. I would advise performing the first flights on 8 1250 SCR cells or 2000 NiMH cells to get the feel for flying the Mig with a reasonable wing loading. Performance is really quite good on 8 smaller cells, and for many this will be all that is desired. If you feel you piloting abilities are up to the task, 9 2400 Sanyo cells really makes this plane and power system come alive, with top speeds estimated above 80 mph and very nice vertical performance with nearly 4 minutes of flight duration available.

The Kit was a pleasure to build with only two problem areas. The wing trailing edges required a bit of fancy sanding to result in a reasonable thickness, and the elevator linkage needed to be redone when I disregarded the instructions. I should reiterate that problems with the elevator linkage is not a design flaw of the kit. Rather it is a built in problem with modeling planes having swept hinge lines; any scale plane with a heavily swept elevator hinge line will be a challenge to hook up properly. The Mig-17 kit builds into a very nice scale representation of the real plane; this is not a "cartoon scale" type of kit. I can be reached by e-mail @ truercflyer(at)cs.com if you have any comments or questions about this review.