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Jul 18, 2019, 04:14 PM
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Warbirdmadman's Avatar
Maybe it's because I don't have the two fuse parts glued. Do you unscrew the front cone to remove or leave that in there?
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Jul 18, 2019, 05:21 PM
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Lynxman's Avatar
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To install the fan I first insert #1, then install the fan unit #2. It might be easier to glue them together and install together. Then I slip the rubber ring #3 all the way onto The duct #4 and drop the duct in. After it's in place I pull the rubber ring #3 back so that it covers the join between The fan unit #2 and the duct #4. Removal is in the reverse order.
Jul 18, 2019, 06:41 PM
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Warbirdmadman's Avatar
Quote:
Originally Posted by Lynxman
To install the fan I first insert #1, then install the fan unit #2. It might be easier to glue them together and install together. Then I slip the rubber ring #3 all the way onto The duct #4 and drop the duct in. After it's in place I pull the rubber ring #3 back so that it covers the join between The fan unit #2 and the duct #4. Removal is in the reverse order.
Oh, that make perfect sense. Doh!!! As Homer would say. I hadn't thought of sliding the seal over the cone because of the step inside but if you do that first, that will work a treat.

Excellent explanation too, I appreciate it.
Jul 19, 2019, 04:58 PM
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Lynxman's Avatar
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Almost had a bad day today. The right main landing gear wouldn't come down because the 3D printed shoch eye end broke on takeoff and caused the gear to jam while retracted. I made several circuits cycling the gear to try to get it down, not knowing why it was stuck. After a failed emergency landing approach I tried to cycle the gear one more time and it came down. I flew for 7 ,5 minutes and spent 4400 mAh. I get amazing duration. I had set the timer to 4:40. I'm gonna change the timer to 5:30 to give me an extra minute of flying before I land.

The gear door servo for the left main gear broke too for some reason. No idea what happened there. Doesn't respond for some reason, and it hung open during the flight.

easily achivable 7:30 flight duration must be some sort of record.

It wasn't because the shoch end broke. The retract is just sticking. I will take it out and see what's going on. It's the Hobbyking unit. Maybe I need to replace it.
Last edited by Lynxman; Jul 19, 2019 at 06:27 PM. Reason: Mistake.
Jul 19, 2019, 05:16 PM
Purdue Engineering
Rocketman1092's Avatar
Hey Lynxman,

I've started printing this model on my Prusa MK3S (250mm x 210mm x 210mm) and Pegasus (300mm x 300mm x 300mm). The larger printer has been causing me some tuning/extrusion frustrations, so I'm tempted to figure out how to print the whole thing on my Prusa. As far as I can tell, the changes I'd need to make are:

- Split fuselage parts 1-4 into two halves down the centerline
- Remove the trailing edge bit that supports the root of the flap from Wing01 and glue it on later

Do you see any drawbacks with this, and would you recommend a particular tool for editing the STLs? I don't like bringing them into Solidworks because loading in that many polygons really bogs down the PC.
Jul 19, 2019, 05:20 PM
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Dirty Dee's Avatar
Quote:
Originally Posted by Rocketman1092
Do you see any drawbacks with this, and would you recommend a particular tool for editing the STLs? I don't like bringing them into Solidworks because loading in that many polygons really bogs down the PC.
Try downloading blender. It's free, and you can import/export STLs. Might take a day or 2 to get use to the interface.
Jul 19, 2019, 06:31 PM
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Lynxman's Avatar
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I dont' see a problem with that. Might be a few grams heavier. I'm about to upload a video of the 8 minute flight.
Jul 19, 2019, 06:45 PM
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Lynxman's Avatar
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Here's the video from today. Looking into the retract unit now.

Jet landing gear trouble ends well (8 min 24 sec)
Jul 19, 2019, 06:55 PM
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Lynxman's Avatar
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The retract works outside the plane. I guess the mounting beams aren't aligned or something.

The shock eye end is broken. Seems the spring cup ripped it in two. Maybe the stock shock eye end is safest to use after all.
Last edited by Lynxman; Jul 19, 2019 at 07:45 PM.
Jul 19, 2019, 07:21 PM
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Warbirdmadman's Avatar
Nice flight and great landing.

Glad the retracts finally cycled for you.

Looks great on those low, high speed passes.
Jul 19, 2019, 07:47 PM
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Lynxman's Avatar
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The retract worked when I loosen the rear inboard mounting screw, so I added a washer under that point and now they cycle normally again. I also changed the springs on the shocks to some harder springs.
Jul 20, 2019, 04:17 AM
Registered User
Wow! Just watched the video and I'm stunned how cool you were, considering the flying time and the capacity of the battery.

My first thought about the stuck gear was that something is going wrong with the contol box due to the dead servo of the gear doors. Some missing signal or something like that.
Jul 20, 2019, 10:05 AM
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Lynxman's Avatar
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Turns out it was mechanical. Retracts can jam if the mounting surfaces aren't perfectly flat, and that'what happened. I should have checked the retration before the flight, but it's been perfect so far so I didn't bother.

The door servo seems to have a bruned transistor on the control board. It would only work in one direction. I replaced the board with one from another servo and it's fine now. Pure coincidence that it happened on the same flight as the gear failure.
Jul 20, 2019, 12:19 PM
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Lynxman's Avatar
Thread OP
The new springs I installed on the main gear are these 1.8x18x35 mm springs:
https://www.ebay.com/itm/1-8mm-Wire-...72.m2749.l2649

They hold the weight of the plane without compressing fully.
Jul 21, 2019, 03:45 PM
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Lynxman's Avatar
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If set my timer to 5:30 today. It was too long for me. The last minute felt like I needed to land. I'll reduce to 5 minutes on the timer for the next flight. I spent 4000 mAh and total flight time was 5:30, and it was a pretty spirited flight.

A friend had brought his Black Horse L-39, which is almost exactly the same scale. I made a video with both planes. His would stall when he pulled high G and it even happens once in the video as he's pulling out after an immelman-like maneuver. Mine can handle much higher AOA without stalling. He commented that he thought mine seemed to fly better. All I know is I like how mine flies. The BH L-39 has a symmetrical wing profile and doesn't seem to have any washout. He's clearly a better pilot than I am.

He has a 90 mm Jetfan with a 1200kv HET motor in his and he said it's pulling up to 5 kW, but is not sure about the peak figure. He removed the intake ducting and wheel doors to let in more air as it was starved with them. He rarely used full throttle. I use full many times, and for many seconds. My full throttle power is 3900 W.

My EL-39 spent 727 mAh per minute and his L-39 spent 745 mAh per minute of flight. We both have telemetry to record this. We actually flew with the same type of batteries, Gens Ace 12S 45C 5000 mAh.
Last edited by Lynxman; Jul 21, 2019 at 03:55 PM.


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