Need advice about RC options for ultralight paper airframe project

Discussion in 'RC Aircraft & Watercraft' started by liftline, Sep 29, 2010.

  1. liftline

    liftline Member

    Wheels need some work. The old design had too much friction - I feared nose-overs!

    The new design with bead bearings doesn't track well and is too hard to build anyway.

    Working on plan C.
  2. liftline

    liftline Member


    The wheels are on the model!

    Plan C turned out to be plan B done better. Each wheel rotates on a short music wire axle with a springy loop holding it in place within a paper tube. The tube is glued to the undercarriage struts which attach to lugs on the fuselage. The metal axles allow the wheels to flex up and down a bit - springs for the shock of landing. Each wheel can be removed from the undercarriage. I expect to bust a lot of wheels, so that's good.

    The wheels spin very nicely now. I put a short length of music wire into the forward struts of the undercarriage to add a bit of strength in compression.

    Looks like I nailed the CG. If I let the model rest on the top wing it balances almost level on the curved camber of the upper wing.
    The wing structure seems plenty sturdy to handle the all up weight - which does appear to be very close to 42 g.

    Final finishing touches are a tail skid, exhaust pipes and the Lewis gun. I'll fly the model without the radiator to give easy access to the motor and batter.

    Attached Files:

  3. liftline

    liftline Member


    Ready to fly! Take-off weight is 42.5 g. I put a bit of music wire in the tail skid, that was my last bright idea.

    I'll get some nice pics, but here is the web cam of her on the work bench.

    Started in at the end of September, prototype in early February. I think the real P-51 got built a bit faster!

    Attached Files:

  4. liftline

    liftline Member

    I made some careful taxi tests as soon as the glue was dry. Very short "runway, so I couldn't really open her up for more than a fraction of a second.

    The airplane accelerates quickly. Prop wash pulls it strongly to the right as it begins to roll- but I can keep it straight with full left rudder. The paper wheels aren't perfectly round and the ship bounces a bit, but the motor itself is silky smooth.

    I need to find a bigger venue. Not enough room to even lift the skid off the ground.
  5. liftline

    liftline Member

    A local recreation center let me use their multi-purpose room for some taxi tests.:mrgreen: I estimate the room to be about a 25-30 m square. Enough space to really open up the throttle but probably too small to fly comfortably. Very dark - a cloudy day and the manager didn't want to take the time to warm up the main lights and the auxiliary lights weren't working.

    Model response to the rudder is actually quite good, but at full throttle (& fresh battery) the rudder is a just a little too small to small to fully counter prop wash right yaw as the plane initially starts to roll. As speed picks up you quickly gain enough rudder authority to hold her straight. The wheels seem roll well, but with the narrow track it's easy to over-correct and ground loop. No big deal, the airframe is strong enough to spin nicely on a wing tip with no damage.... I know 'cause I did it several times.

    As I got more practice,I got overconfident, spun 180 and attempted to slowly taxi back. Inexperienced as I am, I got disoriented:confused:, left/right reversal, forgot to chop the throttle with the cutoff switch and hit the wall fairly hard 'cause the skid is not much of a brake. The only damage was to the motor mount-the epoxy bond to the popsicle stick lug failed.

    Very minor repair, but I'll need to cut a little hatch in the cowling to get to the lug. I fully expected this would happen sooner rather than later. I'll engineer a nice hinged cover.

    I think an experienced pilot could handle a takeoff, but for me a hand launch may be the better option.
  6. liftline

    liftline Member

    Scissors, white glue, epoxy and a bit of scrap paper have put the YSe5a back on test flight status. The usual not-so-good web cams are attached.

    The motor mount can be accessed through a hinged panel (not authentic, but looks period) and the battery box has a cover to prevent migration towards the prop circle. Simple slots and tabs keep the covers closed.

    Attached Files:

  7. liftline

    liftline Member

    I still have an old glider version of the model gathering dust. I'm going to ballast it to 42.5g and give it a toss in order to get some idea of how hard to throw on a hand launch.
  8. liftline

    liftline Member

    I was too optimistic. After the epoxy had set for 24 hrs I fired up the motor and it began to stutter - backwards. :curse:There was no way to diagnose and fix the problem without tearing down the model.:curse::curse: I salvaged the wings, tail, surfaces, under carriage, pushrods and servo mounts. That's most of the tough stuff, so rebuilding will be pretty quick.:violin1:

    One of the short leads off the 2g had fractured just north of the solder joint. I'm not sure if the crash broke it or if I damaged it repairing the motor mount. If re-soldering fixes the problem I've lost little time. If I need a new motor I get a few weeks of "hobby vacation."

    Big lesson: buy spares!
  9. ecuatoriano

    ecuatoriano New Member


    do not give up announce1
  10. liftline

    liftline Member

    Thanks for the encouragement. The Liftline is strong like ox! The Liftline is light like hummingbird. The bird will rise again!

    Seriously, the design philosophy of this project is a semi disposable airplane with an easy and quick to build airframe where more expensive components that can be salvaged after a wreck. My concept is being tested.

    I'm a bit busy this weekend, but I think I'll find enough time to rebuild the model by Monday. The only lengthy delay would be if the motor itself is damaged as well as the motor lead. I need to order spare motors and back order spare ESCs today.

    I'm auditioning a test pilot. My RC skills aren't up to test pilot levels, especially in a confined indoor space. The Wing Cubic Loading of the model is just under 8, suggesting handling should be easy, something akin to an advanced trainer.
  11. liftline

    liftline Member

    :curse: Looks like my project is going to be on hold for a few weeks. The receiver works fine, on all channels. I can't rule out failure in the motor (I soldered the broken motor lead and and I inspected the motor under a microscope, everything looks OK) but I think the ESC is the culprit. The chime still gives the correct note patterns, but they have gotten very faint. Not a good sign. I hate, hate, hate ambiguous failure modeswall1

    Motors are in stock, but the ESC is back ordered.

    I'll try to use my now abundant spare time to improve the wiring. This is clearly the weak link in my system - too heavy, too sloppy and too bulky to get in the lower tier servo for aileron control.
  12. schorhr

    schorhr Member

    Seems likea rough start, but a start is a start ;-)
    Next time make a video! :)

    If it allwaxs pulls in one direction (as wel on starts as in the air), angle the motor a little.

    Go try r2hobbies, hobbypartz , or ebay if Hobbyking has problems getting it back in stock...

    Wow, neat :)
  13. liftline

    liftline Member

    Greetings Schorhr!

    Wish I'd been able to find someone to work a camera, but the opportunity to taxi test came up unexpectedly and I went for it. I wonder if the crash somehow shorted the motor and overloaded the ESC? Or if the ESC failure is unrelated to the crash? Rebuilding won't take long, but I'm already at work on a better wiring plan.

    The latest copy of the Economist showed up in my mailbox with a picture of a plastic violin manufactured with a 3D printer. It is said to sound very good. Star Trek stuff, or maybe Hitchhikers Guide. You are on the cutting edge!
  14. schorhr

    schorhr Member

    If the motor blocks(prop on ground, motor mechanically jammed), it will draw very high currents.
    This can damage the ESC, I don't think the crash would damage it physically:

    Yeah, Hitchhiker or Startrek comes to mind all the time when using this thing :) It's crazzy.

    I hope your spare parts arrive soon :thumb::thumb::thumb:
  15. liftline

    liftline Member

    If the motor blocks(prop on ground, motor mechanically jammed), it will draw very high currents.
    This can damage the ESC, I don't think the crash would damage it physically.

    Makes sense. Would it have helped to hit the throttle kill switch or be quicker in hitting the kill switch.

    If the original motor is still intact I'll have 4 in a few weeks. B-17?
  16. schorhr

    schorhr Member

    B17 sounds like fun :)

    If you need something motor/esc less, look at this tiny ultra light sail planes that will fly even with the little winds & currents on tiny hills...

    OR... F3K/SAL, which you throw like a frisbee, and 60m height if you're good at it.


    Anyway, I hope you're plan(e)s will be back up in the air in no time, and hopefully my component advice was not a source for failure :mrgreen: This is a bit smaller then what I usualy build so far :)
  17. liftline

    liftline Member

    The sailplane video had me hooked in 10 seconds. Judging by the airspeed it must weigh next nothing. Gotta build one, its on the to do list.

    I'm going to use my down time to address wiring issues.

    I got a great suggestion for light weight RX connectors from another RC forum. Take apart computer serial/parallel port connectors and solder the female tubes to your leads. Shield and code with shrink tubing. Compact, light and cheap.

    I'd like to make some kind of wire conduit to keep the wiring in place and compact. With Spektrum type connectors (I think the female connectors come with my 1.7 g servos) at the ends for plugging in the motor ESC and servos. A product called Taperwire might work for me. It's a self adhesive electic cable with 2, (no 3), 4 or 8 conductors. 26 gauge is available. I could paste it onto a paper stiffener to get a very precisely routed and compact wire bundle. Do all the soldering outside the airframe and just glue the wire fixture in place.

    Your advice and discussion has been invaluable to me. I'm very pleased with how far I've come and how much I've learned with your help. I should stencil your name on the Se5a as "crew chief." Working on the edge is fun, but you expect to fall off a lot. :wave:
  18. liftline

    liftline Member

    I've made some prototype RX connectors from female D-sub Connectors purchased at the local Radio Shack. I cut the wire crimp connector off the connectors and solder my wire just above the gold plate zone. The connectors are just a bit loose and wobbly on my RX pins, so I gently crimp them with a needle nose pliers AFTER I've applied the shrink tubing. This makes them grip tightly and I'm getting good electrical connections. Crimping before putting on the shrink tubing doesn't work very well.

    Less weight, more compact and significantly less expensive.

    Just waiting on those ESCs to get out of back order status. We actually had a warm day this week, temperatures a staggering 17 C! At midnight! Can't wait for those warm, calm & flyable summer evenings.
  19. schorhr

    schorhr Member

    Glad I could help a bit :)

    serial/parallel port connectors --- sound great... Allways learning something new ^_^
    I guess I could try printing some plugs, but at that scale it will be a challange :D

    btw, if you ever want to look into quadrocopter flights, hobbyking is planning a control board.... probably the cheapest way to get a quad up in the air ^_^ I really need to finish my micro frame and print a bunch of them...

    I got an email notify that one of the 1s ESC is back in stock, the ones you where ordering as well?
  20. liftline

    liftline Member

    Hi, I have a big order on reserve with HK- 2g motors, 1 g escs, 1S lipos, wire - well, it's big for me and my recession constrained hobby budget. Now that I know all the components play together nicely I'm getting triplicate spares. A pair of Z bend pliers were holding up my order (APRIL!!!) so I canceled and put them on my wish list. I can do a decent free hand Z bend until then.

    HK sez they are way behind in getting things out the door due to the Chinese New Year holiday. At least everything I ordered is in the warehouse now with my name on it. I figure my stuff will show in about a week if I'm lucky. Until then, the wings, tail surfaces and landing gear of the Se5a remain in a shoe box, aging like a fine vintage.
    I intend to do a much more refined wiring job on the rebuild and lose at least a gram of weight, maybe 2. Gain some free space for a lower tier servo for the ailerons.

    A quad copter would be quite fun and much easier to fly during the winter months. With an on board camera of course, for that proper "inside the cockpit" feel. I'm pretty good in a flight sim, but such a klutz when my reference system is earth bound.

    Any freeware or cheap RC sims that allow you to dial in power loading and cubic wing loading? That would be very helpful.

    I'm also very taken with the idea of building a sailplane.

    Connector plugs should be a snap for you now - no pun intended. The hard part is finding or fabricating the little metal fittings inside. This explains why the hobby biz can charge so much for 'em.

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