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Highly modified "F-15/EAGLE" 90mm EDF Jet

Old 01-25-2017, 05:47 AM
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jofro
jofro
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Join Date: Jan 2017
Location: Mid North Coast
Posts: 3
Default Highly modified "F-15/EAGLE" 90mm EDF Jet

Highly modified "F-15/Eagle"
Recently I have got hands on this 90 mm 'Plug&Play' EDF jet model kit. For an experienced modeler it might take only few hours to assemble, plug it in and take off, but after opening the box and closer inspection I have decided to spend more time on it by number of improvements. After reading few reviews I learned that with the stock '6S' power set up it is bit of a 'slug'. Despite that, I still like to use the stock power unit which is basically a copy of the "Stumax" fan with just one extra blade added to the impeller. The motor is also a copy of "1680kv HET" inruner with different logo on it.
Fitted 130Amp marked ESC is no where near that, after closer look at it and I rather put it in my 90-100A basket, so it was replaced by fully programmable high voltage 120A Pentium, I have many years of experience with. I rather be safe than sorry with this high current draw, close to 120A stock fan unit. The main power leads were also upgraded to larger gauge with 5.5 mm gold bullet connectors, and the stock voltage regulator stealing the power from the main lipo power supply was removed and replaced with additional H/duty 5 cell NMHi battery to operate all the functions and the receiver. These minor improvements to the power set up increased my static thrust from the 2.5 kg to just over 3 kilos after few tests. Still little marginal for a heavy EDF model but good enough for some nice scale flying.
Further improvements were done to rather inefficient twin inlet/ outlet ducts for a single power EDF by smoothing, filling-up all the imperfections inside and final sealing and gloss finish. The stock 4-5 mm strait cut trialing edges were fitted with finely shaped soft timber ones, giving some 13 mm extra flying surface to all controls, finished off by light filler and painted. Battery bay had to be enlarged by some foam removal and redesigned to take larger 6 - 9 Ah, 6S Lipo packs I have intention to use. Due to this additional weight, the weak scale front section of fuselage had to be strengthened giving me an opportunity to use bit of extra nose lift rather than adding more lead to the rear, by adding some ply formers to join the air intakes to the fuselage on the bottom and creating new leading edge/canards on the top along the nose part, both creating also extra flying area.
While working on the elevators by adding small amount of lead to the inside of LE for balance I have found a serious problem by incorrect size of the control axis which created too much of the free play while fully assembled. For a one thousand dollar model I would expect much better so new elevator axis were machined by trial and error for perfect fit inside the installed tubes in both control tabs and stiffer linkaged used to eliminate any play. Secure washers were added to all control ball lings for the piece of mind. After taking out my temporarily assembled model to do some runs along the back street to check the nose tracking and acceleration all seem to work fine but stronger heavy duty springs had to be fitted to all landing gear oleos, bouncing the model all over the place at close to 4.7 kilogram AUW loaded up with 9000/65C rated six cell lipo at 1.35 kg alone. Just looking at the model with the very high and narrow span retractable landing gear, also very sleek wing span for pretty long fuselage, I just didn't like it, took it strait back on my work bench deciding to do a major mod to the wing tips which is my norm with less efficient and heavy models. Cutting out the wing tips with careful removal of wing tip lights I laminated some balsa and shaped up the concaved profile to fit and extend each wing tip by 90 mm. This gives me not only extra stability but definitelly more impressive look to the model no matter what few scale buffs say. After finishing it off by more filling, sanding and final touch of paint to match existing coat it was back to check how all this innovations are going to affect my CG. Moving the CG slightly back than recommended, loading it up with 6S/6000/65C lipo and 2400mAh, 5cell NMhi I took it to the beach at low tide to try my first little "Joey's hop". Little windier than I would like at some 20km/h northerly, tho blowing in perfect direction. Firstly I did few runs along the hard packed sand and while happy with the tracking I have deployed 15 deg. flaps and gradually applied the full stick, taking only some 30 meters for the model rotating and lifting to aprx. one meter. Holding it in nice level for about 100 meters and bring it down to perfect touch down was all I wanted to see, all with positive result and filmed with my cap cam for further analyses back in my studio. Taking some 300 meters before the model slowed down to make U turn to taxi back made my heart pounding little as the water mark was coming little close for comfort at that distance.
Couldn't be happier, especially after my darling while helping me to carry the gear bag promising to give me a nice reward after the daily siesta for my effort. Well, all I can say it was much better reward than some commentaries I have received so far, such as, Quote- "hope it will fly better than it looks". My motto always was, they only fly as good as you build them.
To really find out, I had to wait few more weeks due to the Xmas period of unsettled coastal weather, it was either too windy or too wet but finally settled and taking it out to my local flying field for a maiden. Typical country of extremes, the day turn out dead calm, not an ideal conditions off the grass and sticky hot and humid day. Loaded up with 6000mA capacity lipo at 4.5 kilo AUW while using 15 deg. flaps the model rotated after only some 40 meters with the help of the little bounce off my rugged strip. Little bit on the slower side but no problem doing the gentle climb after retracting the landing gear and starting of the flying circuit. After leveling off the speed increased and I was more than pleased with the stability and the power to keep up this heaviest six cell powered EDF jet. The landing was perfect, maybe little on the hot side so there was no power needed during the final touch down with the nose up, a typical "Eagle", with same flap deployment as taking off, while using the full length of the strip in the dead calm. Just another perfect flying day, and the new model to enjoy in my EDF fleet. Happy flying, Joseph Frost.
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Last edited by jofro; 01-25-2017 at 06:02 AM. Reason: pics
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