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Thread: 1/2A Boomerang


  1. #1
    MJD's Avatar
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    1/2A Boomerang

    I've been posting this over in the extreme speed forum as I consider it an extreme (or at least modestly serious) speed attempt but in the 1/2A category. But since it is 1/2A..

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    Boomerang lekkie pylon racer
    Profi "Rambler" .049 (proto speed, open exhaust)
    The prop on it is a 4.1x4.5, I'll be fiddling with sizes along that range.
    118 sq in or 108 sq in depending on what you read. Prolly 118.
    AUW 9.4-9.5oz, we'll soon see = 11.6 oz/sq ft at 118 squares
    I predict it will turn fairly well..

    Top speed.. ought to be fun finding out.
    Sorry I'm late dear, I had to help my uncle Jack off his horse.

    Revver Bro #231

  2. #2
    combatpigg's Avatar
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    It turned out great looking..!
    That's a lot of prop, so you might end up with less sound effects but very impressive results.
    WHO GUNNA FEED MAW KEEEIDS..???

  3. #3
    hllywdb's Avatar
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    Really nice job on the cowl. Like the tye dye paint job

  4. #4
    MJD's Avatar
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    Quote Originally Posted by combatpigg View Post
    It turned out great looking..!
    That's a lot of prop, so you might end up with less sound effects but very impressive results.
    I hope the airframe is clean enough to make use of the pitch. This is an E3 thinned a bit and slightly down in dia to about 4.1". I will test and trim with a FG combat prop to slow things down a bit.
    Sorry I'm late dear, I had to help my uncle Jack off his horse.

    Revver Bro #231

  5. #5
    Pond Skipper's Avatar
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    Well done what a beautiful screaming Toucan its going to make in the air, should be a heart thumpah for sure..

  6. #6
    combatpigg's Avatar
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    Quote Originally Posted by MJD View Post
    I hope the airframe is clean enough to make use of the pitch. This is an E3 thinned a bit and slightly down in dia to about 4.1". I will test and trim with a FG combat prop to slow things down a bit.
    The FG combat prop will give you by far the least amount of time to react to an out of trim / balance condition from launch. Your plane will be doing 90 mph before it gets 20 feet from your hand..[[well, maybe just 88 or 89 mph].
    I used to use Cox 6 x 4s cut down to 4.2 or so before I discovered the APC 4.2 x 4. The Cox prop worked OK and was durable for "trim out duty".
    WHO GUNNA FEED MAW KEEEIDS..???

  7. #7
    combatpigg's Avatar
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    Quote Originally Posted by Pond Skipper View Post
    Well done what a beautiful screaming Toucan its going to make in the air, should be a heart thumpah for sure..
    THAT's what this plane is..a Screaming Toucan..!
    I'll bet those birds are pretty expensive nowadays. They are gorgeous.
    The closest I ever came to owning a talking bird was when a neighbor gave me a Conure. They are in between a parakeet and a parrot in looks and size. He tried to talk but just couldn't annunciate the words, so he had more of a drunken Hobo Babble speech pattern.
    This design looks like you could lay up the entire fuselage in one shot and slide out the plug after the cure..maybe with the help of compressed air.
    WHO GUNNA FEED MAW KEEEIDS..???

  8. #8
    MJD's Avatar
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    As a kid we had a Mynah bird, who ate mostly canned cherries as I recall. It could do a perfect ring, and "you're wanted on the phone".. which was funny the first 137 times.

    The trim from launch doesn't worry me (yet) - this thing is light enough to test glide in long grass, and we have gobs of that up at the glider field. I'll probably trim it out with hand tosses.
    Sorry I'm late dear, I had to help my uncle Jack off his horse.

    Revver Bro #231

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    holy doodle! It looks fast just sitting there! I really hope you get some video

  10. #10
    MJD's Avatar
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    Hey!

    Spent some quality time tonight with 1500 grit wet paper dealing with a few blemishes and epoxy fingerprints. Sat for about an hour with some chunks of cotton T shirt and a bottle of Crystal Glo to work some gloss back into the sanded bits. Looking pretty shiny now. A very shiny Screamin' Toucan.
    Sorry I'm late dear, I had to help my uncle Jack off his horse.

    Revver Bro #231

  11. #11
    Pond Skipper's Avatar
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    Might be more like a screaming rainbow streeeking across the sky in a blur of colors. How fast do you expect it to go in the 140's?

  12. #12
    MJD's Avatar
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    That's what I am hoping. I think 140 is realistic and if it's more, bonus.

    There is an identical version of the engine in 1cc/.061 available, but the whole point here is .049 power.
    Sorry I'm late dear, I had to help my uncle Jack off his horse.

    Revver Bro #231

  13. #13
    Pond Skipper's Avatar
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    And the crowd chants vid vid vid

  14. #14
    MJD's Avatar
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    For sure, I won't skip the video part. Every flight is the last flight unless it survives.. (that's not really profound, but it is always true)

    I cleaned off some overspray form the inside of the radio compartment so I could see the weave better. It is glass/Kevlar predominantly, with CF in the corners. So the RF windows are pretty big. Still vacillating over the Rx.

    If I am going to poke the antennae through the fuselage, maybe I'll orient the receiver so the antennae point fore and aft, and run them longitudinally on the side of the fuse with a piece of film or clear tape over top. Make sense?
    Sorry I'm late dear, I had to help my uncle Jack off his horse.

    Revver Bro #231

  15. #15
    MJD's Avatar
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    For sure, I won't skip the video part. Every flight is the last flight unless it survives.. (that's not really profound, but it is always true)

    I cleaned off some overspray form the inside of the radio compartment so I could see the weave better. It is glass/Kevlar predominantly, with some CF in the corners. So the RF windows are pretty big, but there is some longitudinal carbon. Still vacillating over the Rx. Maybe an AR400 if I for some reason shy away from the little micros.
    Sorry I'm late dear, I had to help my uncle Jack off his horse.

    Revver Bro #231

  16. #16
    Pond Skipper's Avatar
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    Here is a doodle of the fuel brake - I like it as its gentle on the fuel tubing and allows consistent metering via the servo.


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  17. #17
    MJD's Avatar
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    The Toucan sat dormant for a while, I've been doing a few other things through summer and into September, lots of time in the Moth for example*. And I been building a jet, that's a bit of a transgr.. er, digression.

    I got hung up too long on a tiny fuel shutoff mechanism for this thing, so today I finally said screw it and Dremeled a little slot in the side of the cowl for a hemostat or microclip. Perfect. Done.

    So tonight I weighed it with everything.. battery, step up regulator, Rx, fuel system, engine, cowl and prop = 265g = 9.35oz. I'm good with that.

    Home stretch now.. stick down the battery, regulator, Rx etc. and hook it all up. Line the bladder compartment. I'm not making a bladder tube. From the wing forward everything is impervious to fuel. I'll line the forward fuselage, slide in the bladder, then retain it with a 1" thick piece of foam stuffed just in front of the wing root. If the bladder bursts, the engine starves and dies, nose down and the fuel can pour out past the engine... failing that the foam will absorb and act as a barrier. No problemo.

    50/50 for this weekend, both finishing radio install and final setup and bad forecast. But.. nearly there now.


    *
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    Sorry I'm late dear, I had to help my uncle Jack off his horse.

    Revver Bro #231

  18. #18
    MJD's Avatar
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    Progress - really. Last two evenings completed the radio install and am very happy with the fit and balance etc. The aircraft is all ready to go except for two details:

    - fitting the bladder tank and a tube or bag spooge catcher.
    - saw off the thumbwheel on the NV and make it screw adjustable through a small hole in the cowl

    An hour's work tops.

    So if we get a break this weekend I can finally maiden the darn thing - hooray! Just in time for winter..

    2 x HS65HB
    Lemon 6ch Rx, caseless with one wrap of tape
    300mAh 1S Lipo
    HK step up 5v regulator (the darn things seem to work!)
    All up weight is still barely 9.5oz. This thing is going to haul.
    Sorry I'm late dear, I had to help my uncle Jack off his horse.

    Revver Bro #231

  19. #19
    MJD's Avatar
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    Temperature is 33F, winds gusty 10-15. So, logically, at lunch I took the Boomerang out back for some test glides. All is well - CG feels good, slightly nose heavy relative to race trim. Fast flat glide but obviously very low wing loading, controls feel solid. I have triple rates on the flight mode switch, I used middle rate for this.

    There, that's out of the way. Time to fly!

    I hate running 1/2A's in cold weather, I always end up with frostbitten hands.. lessee what the weekend brings. Where I'm going to test fly, I could start inside and launch from the edge of the field, if I am too much if a sissy to pit it outside.
    Sorry I'm late dear, I had to help my uncle Jack off his horse.

    Revver Bro #231

  20. #20
    skaliwag's Avatar
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    There's an age limit when "Sissy" becomes "Sensible".
    Real Airplanes have Round Engines and Two Wings.

  21. #21
    combatpigg's Avatar
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    I'm really hoping that the HK parts work well. Being able to go with just a single lipo cell really expands the possibilities for small RC.
    Maybe the obsolete NIMH packs can be used to heat thin gloves that have nichrome wire threaded through the back side of the fingers...? I've been threatening to try this idea for several years now. Otherwise, I use a 5 gallon propane Mr Heater for some relief, but it's mostly only good for preventing frost bite between rounds.
    WHO GUNNA FEED MAW KEEEIDS..???

  22. #22
    MJD's Avatar
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    Our new hangar/shop is a large shed next to 100 acres of flat cultivated fields with two runways. 20 minute drive away. So for starters I'll put in10cc of fuel and burn off 5cc walking to the edge of the field from inside.. .

    The Profi .061 racer has been sitting in the wings as well, I reset the wing incidence, moved the CG forward, and replaced the NiMH with a 430 mAh 2S LiPo and a Novak regulator. It's ready to go too. The Rx battery alone is probably big enough to fly the thing around for a couple of minutes at 60mph.
    Sorry I'm late dear, I had to help my uncle Jack off his horse.

    Revver Bro #231

  23. #23
    MJD's Avatar
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    Hey here's a question for the combat flier(s) in the crowd - how much does the needle setting vary between subsequent fills and runs on the same bladder?
    Sorry I'm late dear, I had to help my uncle Jack off his horse.

    Revver Bro #231

  24. #24
    aspeed's Avatar
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    Not too much, but the cold may affect it a bit, or break the bladder easier.
    Glow Head Hood # 7

  25. #25
    combatpigg's Avatar
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    All it takes is 1 over inflation to spoil the latex. I haven't done it yet, but I plan on converting my Cyclon .061 to backplate pressure and just use Hayes 1 oz tanks for 1/2A.

    The tubing has a shelf life, so the freshness is an unknown variable. Good stuff should last for at least 5 or 6 flights.
    A good habit is to toss the latex at the end of the day so you aren't tempted to reuse it the next time you go fly.
    If you over fill the bladder, the high pressure at the beginning of the run can fool you. You set the needle for what you think is rich enough, then once the plane is launched the bladder empties out enough for a pressure drop. When this happens, the engine suffers, you suffer, C/L flyers will belly land under power to save the engine if this happens.
    With case pressure, bad needle settings have been much more rare around here. The needle is much less critical and the pressure is more constant.
    Last edited by combatpigg; 11-12-2014 at 09:58 PM.
    WHO GUNNA FEED MAW KEEEIDS..???


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