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Engine run in the plane - first time.
I made up a servo driven micro switch for the emergency engine cut and wired it in the model this morning. It works fine...............why worry about semi-conductor devices for such a simply function?
Vollrathd kindly posted details about an electronic engine kill switch, but it looks far too complicated for the task. Arduino board, MosFets, opto isolated relays, PCB boards, programming........................Whheww!........ ....... I assembled the model, staked it down on the grass and gave the engine a run. I tuned it a bit better; it is still not optimal, but its running very nicely. It will start with one or two flicks after shut down to adjust mixture screws or something. Nice! It sounds good, not as noisy as I first thought it was, probably about average for an IC engine of this size. I already suspect that the 1/2 liter fuel tank is too small though! But a bigger one can be fitted later on. I fitted the shorter, harder rubber engine mounts that I had. I think the "rate" is about right; they flex just enough to take the severity out of the engine vibration. 7,400 RPM max throttle on the 18 x 6 propeller. Running on AvGas and Stihl Ultra @ 30:1. AUW 8.2 kg. This is slightly heavier than Sorens (SpeedsterDen) 1/4 scale Spacewalker. His is powered by a 35 cc engine and AUW is 7.6 kg. and is capable of vertical flight. Special note for Scott: I swear I did try to take a video of it running, really I did! But both batteries were flat!......................So, you will just have to believe me............. Jim. |
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Model crashed on Maiden flight!
Sad news. I regret to report that I crashed it on the maiden.
Destroyed. Pilot error due to several factors including the following: 1. My age. 2. Rhinitis induced eye problems. 3. Nervousness increasing the above problems and causing tunnel vision. 4. Loss of orientation due to the combined effect of the above. Jim. |
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Bugger ! not the report we were wanting to hear. I am disappointed for you after all your hard work, but don't let it stop you. Aero modelling has it ups and downs ( no pun intended) and those high times lets us forget about the low ones. Remember the good, chin up and move forward, after all, we all know that you are a skilled builder and I take my hat off to you for your drive and innovation. I hope we see another build thread that we can follow and be asked to put our two bobs worth in.
Andrew |
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Quote:
Dave has already made me realise the model could be rebuilt from the few undamaged parts and components. Knowing me, I will most likely rebuild it, but I won't be doing it any day soon. Got to get over the shock. It has really shaken my confidence, to say the least. Also, when and if I do, I will not be flying it. There are other pilots with more than enough skill and capabilities to fly it for me. Edit: This conclusion was reinforced in my mind when I had a discussion with a good buddy in town today. He reminded me that this was two crashes in succession (during maiden flight); both big builds, the plank build was much longer than this tug. He asked what do I conclude from that? I said I will be sticking to gliders, I can fly them................. but not powered planes......................for some reason or other. An examination of the wreckage confirmed the integrity of my build methods; the wrapped spar is totally intact. The joiners broke, but not the spars them selves. All control surfaces are ok, etc.................I have pioneered some darned good building methods, I can say that much! He being an old aviator does not agree and suggests that I need beta-blockers! Jim. |
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Last edited by Jim.Thompson; Jun 19, 2019 at 02:57 AM.
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I just cleaned and stripped the motor down.
The bottom end appears to be ok. The crank was pushed too far into the rear bearing, but when I dissembled it, the bearings and shaft seem fine. Both manifold flanges are broken though. They might be repairable, but I will also look for another replacement. 38 mm diameter bore. Who knows? There might be one out there somewhere. |
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Jim, Don't let this stop you from flying powered planes. If you can fly a glider you can fly a powered plane. Have someone maiden and trim it. Let them take it up level and hand you the radio. You just need to get your confidence back.
You lost your MOJO son, you can recover.. Scott |
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Quote:
Thanks for the encouragement Scott. I greatly appreciate it. I've come to realise that I am a very good builder, but not a good powered aircraft pilot. I did fly slope the day after like nothing had happened on the day of the crash. I flew my light Entropy in fine style. So, I still have that skill unimpaired and still improving each time out. It is just powered planes that have brought me undone. I went into town and talked with my ex aviator buddy. He has been a flying instructor, sailplane pilot, cropduster pilot, regional airline pilot and more. He confronted me with the statement: "That is two in a row, what can you conclude from that Dude?" It was not until after I realised he was wrong, it is three crashed power planes in a row at my hands, two of them maiden flights. And all of them due to anxiety induced freeze up of the pilot; me! I know full well, he will continue to challenge, coerce and do anything he can to get me to fly another one if and when I rebuild the Spacewalker, or start with something entirely different. But the problem is, he is advocating doing what would be best for him, not me. That is the reason, or one of the reasons he is successful where I am not. I've already had nightmares about crashing, each time in different situations. I had one last night, woke up, went back to sleep and then had another one! Any new powered plane I eventually complete will be flown by one of our expert mode 2 flyers (I fly mode 2.....most flyers here fly mode1). I might, just might, fly it with a buddy cable and master pilot. There is a limit to my masochism. Jim. |
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On a more positive note.
The construction methods used in the build have been very well proven as excellent. Nothing less; I have yet to find something in the wreckage that suggests inferior engineering or constructions.
The fully wrapped spar is a winner on all counts. It is light (weights in an earlier post somewhere) and very strong and remains totally intact after the crash. The 8.3 kg model could be lifted by each wing tip without excessive flex. The foam ribs stuck to the back of the spar perfectly with the PU glue fully. (something I had doubts about) All four control surfaces are fine, I have yet to inspect them thoroughly, but it looks as though there is just some damage to the covering. The diagonal rib framing method of them stood up completely. I would certainly recommend that construction method without reservation. This also has excellent torsional stiffness. Silicone hinges took a punishing, but only one tore a bit. Most still intact. And it is only general purpose hardware store silicone. More as the post mortem continues................ Jim. |
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Last edited by Jim.Thompson; Jun 19, 2019 at 05:47 PM.
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If a buddy box is what it takes to calm your nerves, fly it on a buddy box. You simply need to convince yourself that a powered plane is nothing more than a glider in a never ending thermal. You can do it, you just need to convince yourself. find someone with a trainer and buddy box and take it around the block a few times.
Scott |
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Quote:
In my own defense, I am aware that in full size aviation, it (crashes due to freezing up) is not uncommon for pilots with low hours in type. A figure of less than 100 hours is considered vulnerable. Even in high hours pilots! By all accounts, something that pilots are not happy to admit, I am told. So, that kind of makes me feel slightly less of an old fool playing at something beyond his capabilities. The reader might be surprised to read that I am at least an average slope glider pilot and even fly low speed dynamic soaring. Thanks Scott. Jim. ..............Reaching for the whisky bottle! |
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Last edited by Jim.Thompson; Jun 20, 2019 at 07:55 AM.
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Johnny Walker Wisdom..............
After indulging in some anesthetic libation tonight to dull the memory temporarily, then falling asleep on the sofa, I had a flash of inspiration.
Don't hold me to this............but.......: I am considering going all out to re-build the Spacewalker before the September festival at Mt. Borah, which starts around the middle of the month. It is theoretically possible! Much depends upon the motor and whether or not the head can be fixed. As for the airframe rebuild, I am fairly confident I can manage that in time,. I stripped the engine and the bottom half appears to be ok. I will get my engine rebuilder buddy to check that over to be sure. But the manifold flanges on the cylinder head are both broken. I continued to strip out any serviceable parts from the wreckage today. All servos are ok. the other electronic components are yet to be checked, but they are most likely ok. The only parts of the aircraft that Dave Brown (the large model inspector) did not like (but allowed them and passed the aircraft anyway!) was the flexible undercarriage and the transparent (HobbyKing) fuel tank. (????) I could not, and still cannot, get my head around this. What is wrong with it? Don't know. I intend to send him the links to replacement tanks to gain his approval before ordering a replacement when i rebuild. Anyway, I will start the work one day soon regardless of the deadline. |
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