F-117 V3: The “Best Looking”

Discussion in 'Scratchbuilding!' started by RCPowers, Jun 10, 2013.

  1. CeeKay

    CeeKay Ace Pilot

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    Thanks for the advice. Ive had the V3 package for over a year now but I've mainly been building FRC Foamies designs of late.

    I originally bought the package to build the F18 and F35 but I have to confess that I preferred the look of the FRC F18 so I built that instead. I am going to do the F35 next.

    I've flown other F117 designs (Rc Foamfighters FF117 & FB28) so I know what to expect.

    I'm really impressed by how close this model resembles the real aircraft. Much better looking than the RC FF one.
     
  2. Nightware

    Nightware Rookie

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    Well, I need to build another one.

    The failure sequence: flutter of the tail assembly, dual cracks on each side, at the narrow point between the wing and tail, behind the prop slot. Added bamboo skewers to the leading edges of the V tail.

    Reinforced that with carbon strip epoxied into the wing plate. No problem.

    Turned up the control throws. <---- idiot

    Really enjoyed how fast it stops in midair, with a sudden pitch up........


    see it coming?


    Turned up the control throws <---- bigger idiot

    Folded both wings in two places, parallel to the elevon leading edge.
    Now flys very, very poorly, and will be salvaged to provide electronics for MK2......

    Good thing it'll snow soon, here.

    Don't be dumb like me :)
     
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  3. lethuye

    lethuye Airman

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    Nightware, do not be discouraged by this incident! I have built 8 RCP aircrafts and they all fly very well. On your next F-117, do try and follow the building instructions carefully. I used 55* template to mount vertical fins (this help in eliminate the flutter!) and also I used 90* template to check the motor mount.(Because of the sloping fuselage top, there is an optical illusion of the motor mount being with positive incident!). If you can program your transmitter, try dual rates with expo. High rate 100% with 40% expo and low rate 70% with 30% expo and fly with low rate on your first flight.. All the best for your next build as well as wishing you a successful maiden flight!

    Lethuye.
     
  4. Nightware

    Nightware Rookie

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    Oh, it flew great. It's just that I experimented, and found the edge :)

    I got an engineer's tour of the Canadian Aeronautical Engineering Test Establishment, and part of that was a bunch of great info and film about flutter.

    The flutter my model experienced, was at pretty high speed, with the control surfaces on the V-tail.
    Next time, I will use larger diameter control rods as well, to increase stiffness there, a bit.

    I've built other 6mm foamies (the sea dart is a hoot), and learned that deflection may not always be our friend.

    The only problem I have at the moment, is that I've only got enough foam to finish building all the V3's...... Well. The winter here is long, so maybe I'll get them all built before spring.
     
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  5. sundog

    sundog Cadet

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    Discouraging indeed for a beginner: the F-117 V2 was dead easy compared to setting up the recommended Xmitter. Anyone got a clue?

    What's "dual rates", what's "Expo" -- I need a drink :lol:
     

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    Last edited: Nov 4, 2014
  6. sundog

    sundog Cadet

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    "The flutter my model experienced, was at pretty high speed, with the control surfaces on the V-tail.
    Next time, I will use larger diameter control rods as well, to increase stiffness there, a bit."

    I plan to use hollow carbon rods for the servo actuator control rods with stock control rod wire for the short end sections. I use JB-Weld to secure the connections. For the "V" tail at the "38 Degree angle" (be sure the tail angle is correct) Ill put through ONE bamboo or carbon skew at 90* through both tails to secure them. I hope that will work.
     
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  7. DavePowers

    DavePowers Administrator

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    Yeah, the radio programming really sucks.
    You might not (probaly) don't need dual rates or expo for the F-117.
    "Dual Rates" work with one of the switches. You set it so switch "up" is full throws of the servos. Then you throw the switch "down" and the rates go to a preset lesser point (like only 40% throws). This is so you can dial down the throws on command if you are going super fast and don't want to over correct. "Nice" but not "needed" ya know.

    Expo is where it "softens the sensitivity" of the stick movements. 0% is "hard and real" where what you put in is what you get. 100% is where you can move the sticks around alot and the servos don't respond much, but then move alot towards the outside of the stick movements. Again, "nice" but not needed.

    For the F-117 you may want to dial down the roll a bit is all. Just watch for it rolling too fast. You can use (or not use) these features to help with that.
     
  8. sundog

    sundog Cadet

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    ""Dual Rates" work with one of the switches. You set it so switch "up" is full throws of the servos. Then you throw the switch "down" and the rates go to a preset lesser point (like only 40% throws)..."

    Yeah, I got that. But It's annoying I have to set the HK 35A ESC throttle calibration every time I start up -- perhaps a safety thing? Full stick throttle, then Xt ON then PWR Up ESC then beeps Beeps, then Min throttle followed by more beeps to set the motor throttle Min 0% Max 100%.

    "For the F-117 you may want to dial down the roll a bit is all. Just watch for it rolling too fast. You can use (or not use) these features to help with that. "

    Don't know how to do that, with the trims? I did mount the battery way forward to get the correct CoG and to the left of centre line to help counter the huge Prop Torque of the Super Sonic V2.

    Perhaps I should have used the Grayson ESC, but it has a funny plug like [-|] that won't fit my battery without modifications :(

    Evelon Mixing for the HK-T6A V2 Tx Tutorial Here :



    Be sure to click On "Get User" before you do any programming ... I couldn't figure how to save to a file settings, but the Tx remembers -- well, it has so far.

    Maiden maybe this weekend If the Wind dies down? I hope it will fly with the wheels down.
     
    Last edited: Nov 6, 2014
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  9. CeeKay

    CeeKay Ace Pilot

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    I've been using that type of ESC in most of my models for the past few months and never had that issue. Perhaps you've not bound it properly? Are you making changes to the memory settings on your tx for that model (moving it to different positions)? That would cause you to lose the bind. Have you followed this sequence;
    1. Tx on with correct model selected.
    2. Ensure throttle is all the way down.
    3. Connect battery and wait for the tones.
    4. Test your throttle.

    If it doesn't work, check to see if the bind light on the Rx is flashing which would indicate that you are not bound to that Rx.

    Once you've done that, disconnect the battery and then set your throttle to max. Reconnect the battery and you should hear a single beep. Close the throttle and you will get another tone. This has now set the throttle range on the ESC.

    With those ESC's, it's normal to get a beep every few seconds with the throttle at idle. It's to let you know that you've still got the system powered up. It got me confused at first :) until I figured it out.
     
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  10. sundog

    sundog Cadet

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    Yeah, that works -- when it "arms" after Max then Min Throttle I hear a series of beeps -- then slowly advancing spins the prop. If I later turn OFF the Tx then it remains armed and usually works when I turn the Tx back on.

    Now the pre-flight sequence I use is: Throttle full, Tx ON, connect battery (beep, beep, beeps) then throttle OFF (minimum or down) then acoustic beeping signals the armed condition. This is bassakwards in the HKing ESC instructions BTW! :(

    I went out to the RC air park today, nice weather no wind, only one other club member was there. He was very impressed with the 117. I did a couple STOL's, more tweaks to the air-frame and CoG tests. Used the "Ped Egg" to feather the leading edges of the wings and tails, then we went to lunch at the "Purple Cow" in Kingsport TN near the Air Park.

    The instructor will be there tomorrow after church, weather in Johnson City TN is supposed to be good again tomorrow, we will try for the Maiden flight, It's a heavy build -- I hope it will go up and then up!
     

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    Last edited: Nov 8, 2014
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  11. DavePowers

    DavePowers Administrator

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    Really good progress and good job making it work.
     
  12. sundog

    sundog Cadet

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    Yeah, this F-117 v2 beaste was a big hit at the local Air-park, several people at the club wanted to build one.

    A club instructor who took me under his wing, so to speak, told me "first off you have installed the prop backwards!" well that was the only way it would mechanically go on with the bushings provided? It was blowing air backwards -- not forward, to the front of the plane. Instructs "put the numbers to the front, which front? That's like "turn right" from which perspective? Anyway, the terse instructions that came with the prop were vastly misleading. Apparently an "Prop Reamer" would be required! Anyway, an field expedient Joe as usual, I took the prop off with an tiny Allen key and a surgical Hemostat I happened to have in my toolbox, I then painstakingly, very much McGiver like, reamed out the prop hole with an X-acto just shy of the originals shaft mounted bushing diameter. I then put the prop on and tightened the prop cone? Just to press it back into place.
    Success! The prop wash increased like 50% and cleared the tables inside the hanger -- papers 'n stuff flying everywhere -- people were amazed.

    As if to make a long story short, the guy I had fly it did a beautifully smooth taxi, takeoff and then the PJ did a sudden right roll from about 15' feet high -- straight into the bank on the side of the runway -- too quick to correct, but it just renovated my plane nose a bit.

    Well, I already have my plane mostly repaired, reenforced -- much better than new, with steel wire. The flight instructor made several airframe mod recommendations, including adding some form of servo-controlled rudder, then some suggestions about fixing my CTRL surfaces, reducing airframe weight & checking CG balance, battery placement, battery protection padding, a much better way to tape the servo control surfaces than what I had with some specialty X-mesh nylon tape etc.

    I will effect repairs before tomorrow, and we will try for a true Maiden flight then -- weather permitting.

    This time perhaps an "wheels up" hand launch from the top of a Tennessee hill? :lol:

    BTW: The F-117 Vx is not a beginner plane! Even for experienced there are some troublesome issues:

    1st with 3 wheels down (if you got em), it's a ***** to get this plane to taxi straight at all -- due to prop torque/wash, and it requires a LOT of runway (I did not employ an rudder option on my build, more on that later), but I got my plane to taxi fairly well by bending the front wheel left. A rudder & servo is likely needed, either above or below the flight plane (ie. As seen on the infamous Predator Drone) also with an \/ tail assembly.

    The motor, I was advised, may need a thin washer on the left (the prop from rear of airframe view) to offset the brutal prop torque? This is apparently standard practice in RC hobby circles.

    The plane is quite heavy, and it may well require some special skills, beyond those of a beginner or even intermediate in the RC sport, to get the F-117 sailing up up and away all the way to "2 mistakes high altitude" -- or the below mishap may result!
     

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    Last edited: Nov 9, 2014
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  13. DavePowers

    DavePowers Administrator

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    Hey great progress!
     
  14. sundog

    sundog Cadet

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    It floats like a butterfly, but can sting like a bee. Oddly enough, I got stung by a wasp on my control hand yesterday (they have those nasty ground nest yellow wasps in Tennessee), but thankfully no fire ants. My hand puffed up like an inflated rubber glove and it still itches like mad :(

    Anyway, my newly constructed RCP f-117 plane; with my newest mods soured like a Raptor, absolutely straight, all by itself. No corrections by me in flight -- only about 3/4 throttle power. I resisted the urge to buzz the Church steeple way up on the hill, and decided to just set it down to a feather soft and level landing in the grass just short of the neighbors house to the West of us in the subdivision.

    I don't plan to make any more changes to the airframe now. When it's working leave it alone!!

    I was impressed, and so where people coming out of their homes to look at it. It caused a stir in the neighborhood :lol: Very good for a plane partially made out of Elmer's heavy black paper covered foam board eh?

    The only damage? A piece of grass and one dog hair stuck in the nose.

    I caught a cold, almost over it. My flight instructor sliced his thumb and could not goto the air park today, but he may make it tomorrow.

    If he does, my advice to him before I launch will be "don't hold back, lets see what this thing can do."

    There is no such thing as bad experimental data, even if it does not agree with our expectations. If something breaks, you just go and find out why it failed and then try to fix it.
     

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    Last edited: Nov 10, 2014
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  15. DavePowers

    DavePowers Administrator

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    Ha! That is so good to hear!
    And what the heck, got stung on the flying hand?
    So great that you guys are making such good progress.
    People really stop and stare when they see that Stealth shape in the air huh?
    Very fun.
     
  16. sundog

    sundog Cadet

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    Yeah, hope to turn some heads this Sunday if I haven't headed back to Texas by then, and it's not snowing, windy or raining! I am curious to see how fast it is and if it can fly upside down or vertical provided I fly it "two mistakes high" :)

    One thing if we wreck it it will be easier to pack the remains in my truck for the drive home :lol:
     
  17. sundog

    sundog Cadet

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    Finally got in a Maiden ... the instructor crashed it on the 1st turn, when he got blinded by the sun. The nose went 6" straight into the ground, it bent a bit. Good thing I had reenforced it with coat-hanger wire around the leading edge of the nose. It needed the weight there for balance so why not just build it stronger? He also complained about my tape job on the Elevons and said one side didn't have much travel compared to the other so 1st we re-did those then I fixed the nose. He has a special taping technique (see picture) that worked well.

    After he went to lunch with his wife I got the "Top Gun" of the club, the one my instructor friend recommended to me, to fly the bird. He made it look easy. Said it was too heavy to loop, hover or fly upside down though. I noticed some "wing rock" while he was putting it thru its paces. Not sure what I can do about that, or even if I need to? He said adding a "gyro" might help.

    Ill do more renovations to make it lighter then try again tomorrow before Winter sets in.
     

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  18. DavePowers

    DavePowers Administrator

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    You guys have got it going on over there!
    Once you get settled, would love to see a video if you get a chance.
    Picturing this all in my head so far...
     
  19. MarkLoft

    MarkLoft Rookie

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    great look, like it very much
     
  20. gratefulfrog

    gratefulfrog Cadet

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    Well, thanks to all you guys, I just finished my second RCPowers scratchbuild: The F117 V3. There's a picture attached.

    This the link to the build-log.

    I'm not sure about the CG as there is a conflict between the instructions and the plans. I'm going with the plans for the maiden.

    The plane is a gift for a young boy and his father who have just leaped into our hobby!

    Ciao,
    Bob F117 before maiden.jpg
     
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