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Evo Reviews - A Review by R. Wilkin

"Robin sent us this review in March 2006 after building and flying his Mugi Evo. The following text is unchanged in content but has been edited for spelling and readability if necessary. We have added the photo captions."

ROBIN'S FINISHED MUGI EVO - IN GLIDER FORM

ROBIN'S FINISHED MUGI EVO - IN GLIDER FORM
General review:

The kit arrived very promptly and undamaged after ordering via the internet.
 
Building took no time at all, helped by about the best set of instructions I've seen. You have to allow time for the Evostick to set otherwise it could have been completed in an evening. Mine was built as per the kit with no changes – very unusual for me. I used a pair of 5g micro servos I had laying around - perhaps not a good choice as it turned out later.
 
I had intended to use a Speed 400 motor + Gunther prop and one of the 500 - 800mah, 7 cell battery packs I have in stock. However, when I did some dummy runs by taping the motor and pack onto the model, it was clear that the CofG would be too far aft. My lightweight servos contributed to this problem as they are ahead of the CofG. What was needed was a heavier pack that was configured to fit as far forward as possible: e.g. wide and flat.

After some head-scratching I took the easy option and flew the Mugi as a sloper. Fitting a Micron mini receiver and a flat 600mAh battery in the nose gave a CofG at the recommended point.

Test flying the Mugi on the slope:

First flights were done in very light winds and showed that: i) there was far too much control movement and ii) that the CofG could be moved further aft. It also showed that it would drift about and stay up in very un-promising conditions.

I was rather stuck with the control movements as the servos are buried in the wing/body and I’d used the outer holes in the arms. Thank goodness for modern transmitters allowing the adjustment of servo travel.

Flying in better conditions showed that it’s a model that can really move and would twinkle roll faster than I could keep up with. I also found that the CofG could be moved about 10mm back from the recommended point. This improved soaring performance but is close to the limit. Further back and the elevator control becomes ultra-sensitive and the dreaded flick appears. One fun-feature was landing. In a 10mph wind, the Mugi could be slowed up in front of the pilot and allowed to mush gently backwards onto the ground at his feet.

Overcoming my CofG problem:

I got hold of a cheap, brushless, Bell motor that was considerably lighter than a Speed 400. If this was moved as far forward as possible balancing the model was easier. I ended up making a small pylon to mount the motor with just the prop overhanging the trailing edge. Now lots of battery option became available.

AN INNOVATIVE MOTOR MOUNT - PLANE NOW LOOKING A BIT GRUBBIER (see text)
AN INNOVATIVE MOTOR MOUNT - PLANE NOW LOOKING A BIT GRUBBIER (see text)
Electric flight at last:

I am now flying with a 1250mah, 2-cell Lipo battery (and a small bit of lead) to give a weight of about 390g. Using a 7x6 GWS prop, launching is easy (I use the cow pat throwing technique) and performance is excellent. Unfortunately, the 7x6 is too small for the Bell motor on 2 cells so it doesn’t give vertical performance. Nevertheless, it is super to fly and far outstrips my ability to wring it out. I intend to try a 3-cell battery as this should lift the revs and therefore the thrust and pitch speed. The best bit is that, despite the extra weight it will still slow right down for landing. Even at very low speed there is still a lot of control authority. Another bonus is that it is extremely quiet. I don’t know how much of this is down to the motor + prop and how much the design of the model but it allows me to fly where I can’t use my Pico Jet or Twin Jet.

Despite its performance potential, this is still a very benign model. I was flying the other day when suddenly down elevator started to cause it to dive right and up caused a climb left. When the panic subsided, I managed to get it down without damage. Inspection showed that one servo had failed during the flight - how many other models would have survived that sort of disaster? I have since discovered that yes it is just possible to get one of servos out from the built up model.

I haven’t seriously crash tested it yet but it has survived the general rough and tumble of slope flying, including some firm arrivals. Grubby marks of the white twinwall are the main issue.

R. Wilkin

 
Mugi says:

"Many thanks for your review, Robin. Excellent to see your innovative stick motor mount pylon. It's also very interesting to read about your experiences with the Bell type motors. These represent a very cheap way into brushless flight and so it's enheartening to see that such an inexpensive powerplant works well with what is, fundamentally, an inexpensive model aircraft.

These Bell motors are available from many model stores. We recommend AllElectricRc on 01782 788778. They can supply a 2410/08 motor with 15A nominal brushless ESC for just £24.99 (They don't pay us to say this - we just know them to be very helpful and jolly nice chaps) "

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