Background
The Eagle series is the top performance helicopter of Hirobo and it helped Manabu Hashimoto gained two consecutive World Championships, which is a record not achieved by anyone else at of today.
The Eagle series existed for quite a long time, and all through its evolution from the original SST Eagle to the current offering Hirobo design each new Eagle version to be forward compatible, so flyers having old Eagle model could update their Eagle to the current model easily by buying the necessary parts. In addition, Hirobo is well known for its very good parts support throughout the world. Due to these factors, most F3C pilots would keep an Eagle for its ease of upgrade.
On August, 1999, I was present at the World Championship in Poland and saw the outstanding performance of Hashimoto with his Eagle to gain his second World Championship title. His Eagle featured some very unique parts that was not available at that time. Later, this Eagle version was released by Hirobo as the Eagle 99 WC, and featured these changes in parts compared to the Eagle EX 98 Spec. on sale at that time:
Like the previous Eagle 97 WC, the Eagle 99 WC was limited to a production run of 500 units. The cost of the Eagle 99 WC was around US$2,500- at its release.
Later, after the introduction of the Eagle Freya, Hirobo introduced the Eagle 99 WC DTDS, that included similar DTDS dual gear system. The inclusion of the DTDS system is specifically targeted to the new schedule B autorotation maneuver of the 2002 new F3C rules that requires tail to be constant driven. Like the Eagle 99 WC, the Eagle 99 WC DTDS was also limited to a production run of 500 units. The cost of the Eagle 99 WC DTDS was around US$2,800- at its release.
My Eagle WC DTDS started its life as a limited edition Eagle II WC-99, which helped Hashimoto gained World Championship in Poland at 1999. Like the previous Eagle II WC-97, the WC-99 comes included with some special parts that are different than "run of the mills" Eagle EX, runs for a population of 500 units. After I got my Eagle WC-99, it stayed in the box for about half a year, and to my dismay, Hirobo later offered the Eagle WC-DTDS, which is the WC-99 version with the very successful DTDS system featured in their Eagle Freya. Not to let my Eagle 99 WC outdated, I assembled my Eagle 99WC, and modified it to include the DTDS version to make it a Eagle 99 WC DTDS version.
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| Box | SSR-V rotor head |
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| Canopy with carbon inserts | Special white colored flybar paddles |
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| Special low profile landing gear struts | 680mm carbon WC main blades |
Upon opening the box, I noticed that inside the package of the Eagle WC consists of several small boxes. One box contained the canopy, another had long parts like main blades, tail boom and tail carbon drive, one had the SSR-V rotor head, and the rest had all other parts. All parts are packed nicely into different bags, with each bag according to steps of instructions. Bags are packaged in a way that when I arrived to a step of instruction I open one bag that is tagged with the step number in relation to the instruction and all the parts and screws required for that step of assembly would be included inside that bag. I see some of my money already went to the packaging....
The instruction manual came in two separate books. One was the same instruction manual as with Hirobo Eagle EX 98 spec, and another one was an addendum specifically for the Eagle 99 WC. Cross reference had to be made from one manual to the other.
Before assembly, modifications had to be made onto the main frame pieces for it to fit the DTDS system. According to Hirobo, I had to buy these parts to convert my Eagle to DTDS pipe tail drive system:
All of the above cost around US$500- list. Further investigation revealed that the DTDS upper and lower main frames had dimension the same as my non-DTDS main frames, and the only difference was that the DTDS frames had main gear opening larger than non-DTDS frames. I could modify my Eagle carbon main frames to take up the DTDS gear system, without buying another set of main frames, and that would save me around US$300- . As a result, I took out my trusty Dremel to modify my Eagle's main frame. Basically, to enable non-DTDS main frame to take up the DTDS system, all you had to do was to cut the gear opening by about 5mm lower and it should take DTDS system without any problem. My friend Gary Strausser drawn the Eagle DTDS main frames in PDF format to further illustrate the dimension of the DTDS frame opening, and you could have a look at it here.
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| Measurement of the DTDS frame | Carbon frames after modifications |
Below were measurements on the diagram:
Modify the main frames according to the measurement above to modify the regular Eagle main frame to take the DTDS dual gear system. Its better to do the modifications before assembly of main frame. Modifying the frames took me two hours with a Dremel, saw and file, but two hours would save me US$300- and wasted parts, why not?
According to my previous experience in assembling the Eagle, the instruction steps did not follow a logical flow of assembly, and the Eagle WC instruction was no different. In fact, assembly started with the rotor head, but I skipped that and went ahead to engine assembly. I use YS61ST2 as power plant for my Eagle. A 12mm cross member was used as a throttle arm extension because the stock throttle arm did not stick far enough for the throttle linkage to reach. A clutch hub, mounted with a cooling fan, was slotted onto the engine's crankshaft, lock onto position by the engine's woodruff key, and secured by the prop nut. Note that YS engines did not came with the woodruff key, so one had to be ordered (YS part # F1265). With the Eagle's clutch design, there was absolutely no need to dial indicate the fan hub. The stock cooling fan was a plastic molded item, but I changed that to a machined aluminum part made by Correct. The clutch was to be secured onto the clutch hub, fastened by two 4mm screws. The whole engine sat onto the blue T-shaped engine mount, secured by 4mm screws. A two piece fan shroud was to be installed to cover the engine's heatsink. Trimming on the fan shroud was required for it to fit, and Hirobo had included a diagram in the manual showing what to cut and trim on the shroud. The whole engine assembly was to wait until later stages of assembly after fitting the fan shroud.
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| YS 61 ST2 engine | Engine installed with clutch parts |
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| Note throttle extension (purple) |
Correct engine mount reinforcement plates¡@ |
After engine installation, I skipped to steps for assembling the lower main frames first. The fuel tank had to be assembled first before putting up the lower main frames, and it finished without any problem. Then, the completed engine assembly, fuel tank, and other cross members would be sandwiched by two carbon lower frames, and temporary secured by hex screws on a flat piece of marble to ensure squareness of the frames. (If you use DTDS on your WC, you should have the frames properly modified by this stage) Once again I use stainless steel hex screws and aluminum screw base on my Eagle. All things went without any problem, but I would like to share one tip. The fuel tank was held into position by six rubber grommets, and the instructions said to first glue these grommets onto the carbon frames before fitting the fuel tank. However, following the instruction's method, if later you would like to take off the fuel tank for maintenance, the only way to do would be to disassemble the lower main frame to do so. Instead to glue the grommets onto the frames, I would glue them to the fuel tank. Doing this would enable me to take off the fuel tank easily from the assembled main frame for ease of maintenance. Also, after prolonged usage, the two 3 X 64 cross members under the fuel tank would be rubbed flat due to rubbing from the fuel tank, and prolong rubbing like this would one day made a hole on the fuel tank. So, I would always thread two pieces of fuel tubes onto these two cross members so that the tubes would prevent much of the rubbing of the fuel tank to the cross members. The lower main frame was erected by mounting the fuel tank, engine assembly, and the WC front bracket together on a piece of marble to ensure squareness. I used engine mount reinforcement plate set from Correct to strengthen engine mounting. The landing gear bracket of the Eagle 99WC (Not DTDS) came standard with the machined aluminum EX item that was much stronger (and looks nicer) than the pressed metal part, but I heard that the Eagle 99 WC DTDS came with the press metal part instead of the better EX item.
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| Assembled lower frame | Engine installed |
After the lower main frame, I skipped steps to the upper main frames. The upper main frames housed the elevator arms, collective pitch assembly, various mixing arms and levers, so these parts had to be assembled before erecting the upper main frames. The elevator arms assembly came pre-installed, so there was not much work for it other than to put on the two ball links that connect to the swashplate. However, with my Eagle I used elevator arms assembly from Correct, that featured better material and a wider stance for better precision. The assembled elevator arms would then be held onto the collective pitch assembly, which fit together without any problem. Works on the various mixing arms would be to put on joint balls, and those were easy. When fitting the X shaped mixers, note their orientation. Both X shaped mixers either have a dot on one side to mark their upper and lower side. I use a special aileron control arm with revised geometry that prevent differential aileron control that is present with the standard item. The battery trays are two pieces of metals bent into shape. Then all these parts would be installed onto the upper main frames with three bearing blocks. These bearing blocks came pre-installed with inferior Thailand bearings, and I changed all speed rotation point ones (e.g. main shaft, tail shaft) to better quality ones from SKF. Thailand made bearings are known to be wear out easily and wear out bearings cause glitches. I took the Thailand bearings from the bearing blocks by using a torch to heat up the bearing block, and after heat the bearing would drop off easily from the bearing block, then I would put in the better bearings with loctite to held them into position. While fitting these bearing blocks onto the main frame, be careful of their orientation. These main bearing blocks each had a 1mm offset for adjustment of gear mesh, and each of them would have a notch on one end of the block to identify the side with more offset. With the Eagle WC's stock 95 tooth main gear, the notch on the two main shaft bearing blocks should face to the rear of the helicopter, and the dual bearings clutch bearing block should have its notch facing to the front. The upper main frame was erected on a flat piece of marble to ensure squareness, and temporary set with hex screws.
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| Elevator arms of Hirobo and Correct | Alignment of upper main frame on glass |
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| Upper main frame | Close-up of the Correct elevator arms |
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| Place bearing block on a vise | Heat the bearing block with torch |
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| Bearing drop easily after heating the block | Use loctite to place new bearing into block |
Joining of the upper with lower main frame comes next. At this stage, another pair of helping hands would be best to help ensure the whole main frame was squared. What I did was to ask my brother to secure the hex screws that joint both main frames one by one, while I held onto the frame on one hand and an angled rule on the other to make sure the whole main frame was squared. Once the frame was set squared, I would unscrew each screw again, put on loctite, and secured them again to lock on the frame. Joining the frames looked easy, but if you absolutely want your helicopter to have a right mechanical foundation, you had to use much care and attention at this stage. Also, starting with the Eagle 98 spec a third main shaft bearing block would be used under the main gear as a cross member. This bearing block was the same thing as the other main shaft bearing blocks, but did not came with bearings pre-installed. The direction of this third bearing block should be the same as the other two main shaft bearing blocks. However, some pilots would put a bearing on this third bearing block cause it would give another bearing support to the main shaft. While this was logical in theory, I did not recommend doing this. I tried putting a bearing on the third bearing block, but found the Eagle to have weird flying performance after the modification. I compared notes with other pilots and Hirobo, and we concluded that a bearing on the third block would take out the minor flex on the main shaft that was needed for smooth flight performance, so we opt not to use it. So, for you guys who were thinking of putting a bearing on the third bearing block, I'd say "Don't do it!", it would be a waste of time.
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Joining of upper main frames to lower |
Another look of joined main frame |
Next I skipped to the fitting of the drive train onto the main frame. The main shaft of the Eagle 99 WC provided two mounting length adjustments (185mm and 195mm respectively). I followed the instruction manual to use the 195mm hole for the longer length main shaft setting would provide better hovering characteristics. Make sure the main shaft could "drop" easily onto the two bearing blocks, cause that meant your main frame was squared. The stock main gear (Non DTDS) came pre-assembled. For conversion to DTDS system the lower LSD part of the main gear assembly had to be taken off for the lower DTDS second gear. In fact, for my case, I left the original main gear assembly alone, and assembled the DTDS gear using parts I had. I used a main gear from Correct, which was proven for better precision and smoothness compared to the Hirobo gear to build my dual main gear DTDS system. If you were converting from stock LSD to DTDS, make sure that a tiny free play between the two gears had to be present for smooth operation, and make sure the lower part of the main gear hub would not rub on the inner side of the DTDS lower main gear. If rubbing between gears occurred, use a file to trim the bottom part of the aluminum hub to fix. Fix the DTDS main gears onto the main shaft provided no problem. I replaced the stock collar with a "clamp on" style one from Correct to prevent denting on the main shaft. Then, I fitted the 0414-155 DTDS counter assembly for pipe to replace the original assembly for LSD. The DTDS counter assembly was a direct replacement to the LSD version, so no modifications was needed. Proper gear mesh between the DTDS lower main gear and the DTDS counter gear assembly had to be set at this time for smooth operation. I used a pair of Correct parts to further strengthen the mounting of the DTDS counter assembly.
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DTDS with Correct main gear |
Close-up of DTDS counter gear assembly |
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K&S 7mm hex start adapter |
Correct gyro mount and reinforcement plates |
One of the gems of the Eagle 99 WC was the SSR-V rotor head. This rotor head was fitted to Hashimoto's machine when he won the World Championship in Poland in 1999. In Poland, when I saw Hashimoto's machine, I immediately noticed that the width of the rotor head was much wider than the SSR-IV rotor head that came standard with the Eagle 98 Spec. This SSR-V rotor head was an updated version of the SSR-IV rotor head, in that it improved the aerobatic performance while did away the flaws of the SSR-IV head. Owner of SSR-IV rotor head might known that when the collective pitch was at over -5 degrees while the flybar was deflected to the max one of the blade grips might be "locked" into position because the short pitch change linkage would locked itself up. When this happened, most likely the helicopter would be at an inverted position during a roll, all cyclic controls would be gone and led to a heavy crash. SSR-IV rotor head owners had to take great care in setting up the short pitch change linkage so that the "locking" won't happen, and it usually took great efforts. Sadly, this problem was not mentioned in the Eagle II with the SSR-IV head, so pilots had to learn this through the hard way, or from some other pilots that had the same problem. The SSR-V head solved this problem by shortening the distance between the flybar and the blade grip, so that "locking" won't occur even at -10 degree collective pitch. In addition, the SSR-V rotor head comes standard with the EX yoke that did not have any deflection for better aerobatic capabilities. Other improvement on the SSR-V head was a pair of updated flybar control brackets that further strengthen the flybar. The SSR-V head came pre-assembled with the 99 WC, and it was packed by itself in a small box. There was not much to do for assembling the rotor head other than fixing the flybar paddles, and linkages. The flybar paddles that came with the Eagle 99 WC was the same plastic WC paddles as with the Eagle 97 WC, but with a special edition while colored label that was not for sale. Two pieces of 7gram flybar weights were also included for pilots to tune cyclic response. After I assembled the rotor head, I balanced the whole rotor head on a high point before putting it onto the main shaft
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SSR-V rotor head |
SSR-V rotor head |
Next I skipped to the assembly of the tail unit. Tail gear box came pre-assembled. However, I had to disassemble it for some parts change. As with all my Eagles, I used the Correct tail pitch link instead of the flimsy plastic stock one. The Correct tail pitch link was made in metal, and was bearing equipped to make tail pitch change very smooth and precise. I'd say its a must have for all Eagles. Tail rotor had two bearings and a thrust bearing on each blade grip for smooth operation, but instead of the stock plastic blade grip I used machined aluminum tail blade grip of Correct. Also, I changed the stock tail pitch lever mount from the stock metal pieces to carbon ones by Hirobo. The tail boom that came with the Eagle 99 WC was in carbon, specially weaved, and in hexagon shape to ensure rigidity. The whole tail gear box was secured onto the tail boom through screws and the metal vertical fin mount that was equipped with dampers for vertical tail fin mounting. Power was transferred to the tail through a carbon pipe drive that operated inside of the carbon tail boom. While the Hirobo carbon pipe was very nicely made, when broken I had to buy another whole piece cause there was no carbon pipe replacement. Instead of using the stock item, I opted to made my own carbon pipe drive through machining of parts and a carbon arrow shaft so that if I damaged the carbon pipe I could just replace the carbon pipe and not the whole set. My own carbon pipe drive had better bearings and wider support for a smooth and secure operation. The tail servo mount was made by two metal mounts and a piece of graphite. Stock tail pitch change linkage was a piece of carbon wire with metal rod ends, but I changed that to the pipe type linkage of Freya for more direct tail control. The whole tail assembly was to be mounted onto the main frame with a plastic mount that mount on the main frame. To prevent the boom from slipping, I drilled two 3mm holes on both sides of the plastic mount through the tail boom and used screws to secure them together. To further strengthen the tail mounting, I used a pair of metal reinforcements from Correct. Two carbon tail boom support was installed from the lower main frame to the metal horizontal fin mount to support the tail, and I use a K&S tail boom supporter in between the boom supports.
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Close-up of tail gear box |
Note optional carbon tail pitch support plates |
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Correct tail pitch links |
Correct tail blade grips |
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Rudder servo mount with control pipe |
Stock pipe on the left, my item on the right |
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Wider support with high quality bearings |
Reinforced dog-bone joint |
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Extra 3mm screw used on boom grip |
Top view of tail boom mounting |
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Mounted rudder servo |
Note the fin type surface of the 9251 servo¡@ |
Servo installation comes next. I used Futaba 9Z WC II radio with Futaba 9252 digital servos on cyclic, 9201 on throttle, a GY601 gyro and a 9251 on tail. I made all pushrods according to the instructions, but instead of the flimsy 2mm metal rods and stock Hirobo links, I used 2.3mm hardened stainless steel CMPS push rods and Pioneer oil filled ball links for better strength and smooth operation. While making the ball links, I used a JR ball link sizer to prep the links. Take note of the orientation of the X-shaped mixers while fixing the pushrods for their orientation, with the wider side on the bottom, and the narrower side on the top. The instruction clearly show the position of the linkage mounting point from the center of the servo discs/arms, but they are more suited for Futaba servos. For the aileron and elevator servo disc, make sure that both balls are not in line, but set back a bit from the center to prevent binding on the extreme position. After all servos and pushrods were mounted, I set up the radio for the correct movements and ATV. I mount the GY601 gyro on the front main frame. The instructions provided a very detailed setup instructions as to how to setup the Eagle with Futaba 9Z radio to achieve the same setting as used by World Champion Manabu Hashimoto. I set my Eagle strictly according to the instructions, and later found that only minimal tune up was needed to better suit my needs.
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Futaba 9Z WC2 |
Futaba GY601 with 9251 servo |
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JR ball link tool used to prep ball links |
GY601 gyro installed |
After radio setup, I put on the landing gears. The landing gears that comes with the 99 WC were special type that had a shorter struts. According to Hirobo guys, these shorter struts were not for the low profile look, but for Hashimoto to eye check the distance of the helicopter from him. They said at Hashimoto's height, if during hovering both landing gear braces look to be overlap to each other, then that means the helicopter was hovering right on the center line of the F3C hovering square. I don't know if there was any merit to this use of these special struts, but they sure gave a meaner look. Next I put on a dummy glow plug on the underside of the main frame so that I do not have to take off the canopy to put glow driver onto the engine during startup.
The canopy was another nice item, in that the "glass part" was a piece of carbon. The whole canopy was silky smooth, and looked very cool. The 99 WC came with a special set of decals to apply to the canopy, but instead of that I asked a friend of mine to custom paint the canopy and fins. They came out so nice that I had to buy another set of canopy and fins just for usual practice, and would opt to use the custom painted canopy and fins for contest.
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Custom painted canopy |
Custom painted fins |
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FRP canopy used for practice |
Vertical tail fins with dampers |
Final steps involved putting on the canopy, fins and muffler. I used a K&S muffler for its better performance. After everything was mounted, the CG of the helicopter was head heavy. I used a Ni-Mh 2,500mah pack made by my friend which was about half the weight of a usual 2,000 mah Ni-Cd pack, but still its head heavy. About 20 grams of weight is glued onto the tail gear box to balance the CG. The dry weight of the Eagle WC DTDS was a tad less than 10lb.
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| Left side of assembled main frame | Right side of assembled main frame |
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| Lead weight used on tail to balance CG | K&S muffler |
Being the owner of several Eagle EXs, I could more or less anticipate what this Eagle WC 99 DTDS would handle in flight. Hovering was the usual rock solid, but during pirouettes a lot of correction has to be made on the cyclic to hold the Eagle in position even in calm winds, which was normal for Eagles. I always said that the Eagle EX is not a good performer in F3C hovering when compared to other top line F3C helicopters like JR Superio and Kyosho Caliber, and this WC was no different than other Eagle EXs that I had. In fact, for hovering pirouettes, I felt that even the Freya was better than this Eagle. On the other hand, the new SSR-V rotor head did provide better stability during hovering compared to the old SSR-IV rotor head, and cyclic correction during pirouettes with the SSR-V head required less than the old head.
Once my Eagle was in aerobatics, then the true colors of this new Eagle would show. On aerobatics, this Eagle tracks much better and solid than other Eagles. Loops and rolls could be executed with more precision and control. The YS 61 ST2 worked liked magic, with very good torque, and a smooth performance. The "leaning while diving" as evident with OS 61s were not present with the YS61, and I could say the YS gave more top end power than the OS.
During autorotation, the DTDS system did provide much better tail control, while saving power reserves. Autos could be executed with more precision and grace with the DTDS system installed when compared to the older model Eagles. Compared to the old LSD design, I'd say the DTDS system was much simpler to adjust (in fact, there was nothing to set) and provided much better power reserves.
In general, I could describe that the flight performance of the Eagle WC II DTDS to be balanced between hovering and aerobatics, which stand at different end of the spectrum. The JR Superio could beat the Eagle in hovering, while the Kyosho Caliber would beat the Eagle in aerobatics, but both these helicopters lacked the required performance on the other end of the spectrum. The Eagle's performance was balanced so that it could have good (not the best) hovering and aerobatic performance.
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Hirobo Eagle EX 99 WC DTDS provide a very good solution for F3C pilots as their contest helicopters. The Eagle could perform very well right out of the box, and it included most of the upgrade parts that Hirobo made for it, so there was not a need to spend more on upgrade parts as needed with other helicopters in the same price range. There was very less pitfalls during assembly. Aside from the bearings, most of the upgrades that I put in mine were not necessary to have good performance. With this Eagle, you just buy the kit, assemble and setup according to the instructions provided, and it would have performance near to factory machines. While the Eagle was not the best performance in both hovering and aerobatics, it provide a well balanced machine for F3C pilots to perform. Adding Hirobo's very strong parts and technical support around the world, the Eagle WC 99 DTDS sure makes a "one stop" solution if you are seriously looking for a contest grade helicopter.
Follow Up
As of the finish of this web page, my Eagle WC 99 DTDS have been with me for over half a year, logged over one hundred flights, and still going strong. I had to say I am very lucky because this Eagle has yet to encounter a major crash. During this time, I have further put on more modifications to my Eagle, and I would like to share my experience with you. While I don't think these upgrades were necessary, they sure enhance the performance.
NOVA 3 fuselage
I had a Nova 3 fuselage lying around my home for some time. The Nova 3 was a contest full fuselage designed and made by Hirobo. It featured a "two part" design for ease of maintenance and installation, while maintain a good aerobatic shape. In fact, Hirobo emphasize very much on the "ease of maintenance and installation" part, and according to Hirobo that was one of the main reasons why they did not release the Black Shark II fuselage that Hashimoto used for the Poland World Championship. In fact, I also have a Black Shark II fuselage, but I did not put that in any of my helicopter due to its difficulty in installation and tuning.
The Nova 3 came with either pre-painted in factory scheme, or in white. All the necessary parts and accessories were included with the Nova 3 package. I got the unpainted version because I don't like the look of the "factory scheme", and plan to have someone custom paint it for me. Nova 3 comes in two sections, the canopy and the tail. The surface finishing of the Nova 3 was flawless, no pinholes, seams were found. The sides of the Nova 3 were reinforced by the factory to prevent flapping on the sides.
One day, being a bit tired of the "pod and boom" look, I took the Nova 3 fuselage to one of my friend to let him custom paint it. Putting on the Nova 3 was easy, and goes strictly according to the instructions provided. After putting on the Nova 3, the CG was very tail heavy, and about 160grams of lead weight was stacked on the very tip of the front fuselage to balance. The look of the Nova 3 sure beats the "pod and boom" look, and thanks to my friend who helped paint my fuselage my Nova 3 looks much much better than "run of the mill" Nova 3s.
With the Nova 3 installed, during hovering a lot of cyclic correction was needed, and at heavy winds precision hovering was very very hard. However, its aerobatics that the Nova 3 helped a lot. With the Nova 3, straight line forward flight was much much faster, and tracks much straighter. Noise level was down also with the fuselage, so its more pleasant. The one good thing that I liked about the Nova 3 was that I could install or take off the Nova 3 very easily at my will, all it takes will be about 15 minutes of work at the field to transform the Eagle from "pod and boom" to Nova 3, and vice versa.
I liked flying with the Nova 3 fuselage for aerobatics. It was very graceful to the eyes, and sure make the pilot look more "professional".
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Unpainted Nova 3 fuselage |
Nova 3 during hovering. Looks nice, isn't it? |
YS80 engine
As of the year 2002, a new F3C schedule will be in force. One of the changes in this new schedule was that engine size limit was ease from 10cc (.61) to 15cc (.91). As a result of this change, many engine manufacturers was busy making their engines to better suit the new rules. YS came out with a .80 displacement new engine, and OS with a .91. I chose YS because I had much success with their engine. Mine was a pre-production YS80, and coupled with a prototype Hatori muffler. According to my sources, my engine and muffler was at the final stage of testing so they should be very close to the version that will eventually enter the market.
The look and size of the YS80 was actually very much like the YS61ST2. Careful examination revealed that the carburetor of the YS80 was a new design, but I was glad that YS retained the three mixture needle design with the YS80 carburetor. My source confirmed that the YS80 was in fact using the same crankcase of the YS61 to ease production cost. As a result, the YS80 could fit all helicopters that could fit YS61 ST2. The Hatori prototype muffler, on the other hand, was much longer compared with usual 60 size muffler. Judging with my eyes, the Hatori muffler should be about one and a half times longer in length than most mufflers for 60 size engines.
Except for the engine and muffler, the gear ratio of the Eagle had to be changed also to better suit the YS80's power curve. I used a prototype 12 tooth pinion from Hirobo, and change the main gear to 93 tooth to achieve the gear ratio as recommended by Hirobo.
With the YS80, my Eagle transformed into another machine. The mid range was very sensitive, even with the mid range set a very rich. Forward flight speed was awesome, to say the least! Even at 80% throttle the YS80 would beat the YS61 on any day. It took me some time to get accustomed to the forward flight speed with the YS80 and Nova 3 fuselage installed. Aside from the much better power, the operation of the YS80 was much quieter than the YS61, which was another plus.
Later, when the YS80 was officially released, I bought another YS80 from the market, and found the performance to be the same as my prototype. I definitely recommend other pilots to upgrade to the YS80 if they have not done so.
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YS80 engine with Hatori muffler |
Note the length of this Hatori muffler for YS80 |
