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Confused???
Well, here I am back at it again. After a long break, I have managed to finish the repairs on my KMP F-18. Back a few months ago I tried to maiden this EDF with disastrous results
I figured that I had everything right CG, control throws, etc, etc. But the flight was very short, and didn't end well. Now my question is what went wrong? I'm not new to EDFs but this one has me quite puzzled. I've read this thread from start to finish and took my time building and setting up this jet. So here is the set up, the motor is a HET 700-60 1485kv with HET 9305 fan unit, CC 75A ESC on 8s 4000mah 40C Zippy Flightmax batteries. I had this same power set up in my Fly Fly F-86 and it flew great with plenty of power. The F-86 was a much bigger jet than the F-18 so I figured it should be fine in the F-18. My total weight with batteries is 7.5 lbs. On the maiden it came off the ground in a short distance(maybe to soon?) and piched up like it was tail heavy. I managed to gain control but it didn't seem to have the power to pull out and circled like a feather in the wind and slamed level onto the ground from 6ft. completely damaged the gear and some cracks in the airframe. I set the CG 85mm and made sure it was a bit nose heavy. So I do not believe that I have a CG issue? What I am starting to wounder is I might have pulled up to soon. From all the videos I've seen on this thread it looks like it needs a long run to build up speed before it gets airborne. If any one has some suggestions I'm all ears
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Stick with 80mm on the CG to be safe.
Need some more info. 1) did you modify the exit diameter of the thrust tube? 2) did you modify the linkage in the horizontal stabs? Answers to these questions will give you the answer I have had a few of these and they have their issues but can be resolved with some modifications. |
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Thrust tube needs to be opened not just cut back, I need to measure mine to give you the proper size, with out opening them then you will be flying around in fifth gear all the time,
The horizontal stabs are the most common culprit to the tail heavy feel you had, if there is any flex or slop then you need to go back to the drawing board on your mod. They also list a lot of expo for the elevator in the manual, in my opinion it's way too much especially if you have any flex or slop in the stabs, you will be pulling up elevator to compensate for the slop or flex and then you hit the expo curve and it will pitch the plane. 7.5 lbs is totally fine but if its flying heavy then you need to look at expo on the elevator, if you have too much the plane will feel sluggish and heavy. The thrust tube being to small will also make it feel under powered until it really gets going, it will have good top end but will need a lot of power to fly, again making it fly "heavy" |
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I know not scale but I got a nice pusher set up doing 14k on a 12x12 with 5000mah 6s 40c
I can't find a prop jet that I like the looks. Do you think this bird can fit a 5000mah 6s Lipo? Will 10pounds thrust with 145mph prop speed be ok Also will the eflite 60-120 electric retracts fit as I have exstras? |
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Quote:
![]() those retracts are way too big, we use eflight 15-25's and they are a perfect fit and match to this airframe, just expensive
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