A brief introduction and
opinion on one of Hirobo's finest helicopters.
Did you know that Eagle means Sword in Japanese. Well it does, according to page 2 of the manual...Numerous people have written to me to say that it doesn't, and they are of course absolutely right. It is a hold-over from some bad editing.
There are now several versions of the Eagle 2 available. There is the Eagle 2 that is shown here, The Eagle 2 EX which is a carbon fiber version that also uses more machined levers, and Eagle 2 WC that is a copy of the World Championship winning model, and finally the Eagle 98. The Eagle 98 is an updated Eagle 2 that employs some of the engineering from the Eagle WC. Finally, there is the Eagle 2 gasser which is being imported at an incredible sub $1000 price.
If you have opened up the GPH346 kit box, you will appreciate the packaging that protects and presents the kit. The Eagle is similarly packaged but lacks the clear covered display packaging that shows off some of the mechanical parts in the GPH kit.
The manual is a 62 glossy pages long in black and white. It contains both English and Japanese instructions in columnar format, with clear line art isometric drawings. Supplementing the manual were 3 pages of corrections, most of which were numerical or identification errors.
If you have built any of the other popular Hirobo models; GPH346 or Tsurugi, you will readily identify many of the common parts and construction style. In many ways, the GPH346 is a 46 sized Eagle as it is quite similar in frame structure. The major differences between a Tsurugi and Eagle concern the beautiful metal head and seesaw, 90º tail rotor drive take off from the main gear, machined tail rotor gear box, and miniature ball bearings on the control arms of the tail rotor pitch change mechanism. The Eagle shares the stainless steel tube drive and tailboom though the boom is 805mm long versus 735mm on the Tsurugi. The longer boom and shorter head span (blade bolt to blade bolt) allow the use of 710mm main blades if desired. Like the GPH, the Eagle uses a flat, stacked frame with fixed servos.
The Eagle employs push-pull linkages till just below the swashplate. The Tsurugi has push-pull all the way to the swashplate so that it is supported on all four points by a control arm. The fore-aft cyclic is fully supported but the roll input to the swashplate is on the right side only.
One of the greatest features in building this kit was the absolutely flawlessly produced FRP canopy. All that you have to do is drill four 10mm holes, trim and fit the transparency, and finally stick on the colorful decals. The rest of the kit is a clean and assembly job which took me about 12 hours of work. There was only one area where I had to break out the Dremel. This involved the collective pitch assembly which is a massive molded and steel unit. Two collective pitch levers (0404-622, page 16, item 7) are assembled to the molded carrier with two countersunk screws. Even when these countersunk screws are fully secured their heads interfere with the side frames. I used a dremel to grind down the heads so that they fit perfectly recessed. This took less than five minutes to complete.
My Arcamax heading hold gyro was already in my Tsurugi, so I installed a JR 3000. Yes, it is an expensive gyro that can be beaten in the heading hold department, but it has a buttery feel to it with no overshoot or propensity to wag which makes it perfect for FAI work. This mounts on a dedicated platform just aft of the main shaft.
The radio install was performed exactly as outlined in my guide to mechanical and radio setup. The one departure that I made from my previous radio installs was the use of the Futaba GV-1 engine governor. The big advantage to using the governor is that it makes the the throttle curves basically redundant. With the governor on the curves programmed in the radio are nothing more than straight lines, but you really want to program them anyway, just in case you loose a sensor or something else goes wrong. Originally, I was using a YS 61ST heli engine but just could not get it to cooperate with the GV-1. I replaced the YS with a new OS61 SXWC and now everything works as advertised. My flying has not improved with the use of the governor, but the consistency of the engine is evident. You must be sure to make all your engine mixture adjustments before turning the governor on as it will mask any lean condition and your engine could be damaged. Eventually, I'll provide details of how I setup my governor to work with my JR radio.
From my measurements, here are some of the details:
| Main Rotor diameter | 62" with MA 680mm |
| Tail Rotor diameter | 11" |
| Body Length | 55" |
| All Up Weight | approx 11lbs 4oz |
| Engine | 60-61 class |
| Radio | Heli with options for mixture and governor |
Everybody has one of these, but here is mine anyway. Firstly, the kit is beautiful. The parts are perfectly made and all the moldings are clean and dimensionally correct. Every detail that you uncover is engineered from the beginning for a purpose; the only engineering close to these Hirobo kits is found in the German equipment. It is a pleasure to build.
Flying the Eagle proves it to be a fast, stable rotorcraft. I first flew it with a set of semisymmetrical FAI blades and was amazed at the sheer speed. This produced some of the biggest loops I have ever seen a heli perform. With 3D symmetrical blades, it rolls and tumbles as eagerly as an X-Cell but shows a delicacy in the hover not possible with an X-Cell. I must admit that in comparison with my Tsurugi, it does not appear to "groove" quite the same. I have a feeling that the composite head on the Tsurugi performs an extraordinary job of damping the helicopters motion, something that is not possible with the all metal head on the Eagle.
If you have the extra cash that the Eagle costs above that of the Tsurugi, then give it a try. You would not be let down; however, if you think that the extra cash outlay brings something extra in the way of performance or reliability over the Tsurugi, then keep your hand in your pocket. The fact of the matter is, that it is going to be difficult to beat the Tsurugi at any level, especially in the cost/benefit area. This is probably why the Tsurugi is not popular in Japan, everyone flies an Eagle. If you have any questions, please write. I have more pictures but did not want to bog down your browser, perhaps I'll post them later.
Chris Berardi.
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Copyright © 1998 Chris Berardi. All rights reserved.
Revised: November 25, 1999.