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AMR Trainer 26 - (my) official build thread

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AMR Trainer 26 - (my) official build thread

Old 04-03-2015, 05:30 PM
  #401  
grosbeak
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Anchors cut and shaped for velcro straps.







Anchors glued and weighted.







Tri-stock for strength.







Sidewalls and battery test fit.







A couple of questions on the balance lead...


1) Are extensions available?
2) What's the maximum practical length for an extension?
3) Does anyone make an external port for balance plugs?
Old 04-03-2015, 07:16 PM
  #402  
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More tri-stock added.







Battery strapped in. At this point I flipped the hatch battery side down and gave it some vigorous shaking. All good.







Hatch up...







... and hatch down.


Old 04-03-2015, 07:23 PM
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The hatch battery is for the ignition - the receiver battery goes a little further back on the other side.







At this point I digress to a side project. I recently acquired a new phone (Galaxy Note 4, we're very happy together, thank you) and, as usual, an Otter Box Defender case to go with it. I don't use the Otter Box belt clip in the usual way - too big and bulky and I've always got pockets. But with a little ingenuity it makes a good tripod mount!


First step is to drill out the case so the camera and flash can "see" through. I start by marking the centre line.







Two pilot holes follow.







Off to the drill press, equipped with a 1" Forstner bit. The centre spur on the Forstner bit locates in the pilot hole.


Old 04-03-2015, 07:33 PM
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Two holes are drilled; one through each pilot hole.







Sides flattened with a file.







This is the interface between the belt clip and the tripod, made when I put my Galaxy S4 to the same use. You can see the making of this part in my Otterbox Defender tripod adapter album.







Belt clip on.







It makes a nice stable platform for video, time lapse and shutter-delayed photos. I used it for the latter purpose tonight to capture the CG balance test.





Just slightly nose heavy at the centre of the CG range. A perfect place to start!
Old 04-06-2015, 07:58 AM
  #405  
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Time for some propeller painting. I'm going to use the cream colour that closely matches the base layer of MonoKote.


Masked up.







Sanded, sitting on painting stick.







First coat.







Third coat.


Old 04-11-2015, 03:50 PM
  #406  
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Prop in the balancer - thanks to britcharming on YouTube for his video on balancing 3-blade propellers.







Blades are marked from lightest (one dot) to heaviest (three dots).







A look on the plane.


Old 04-11-2015, 03:58 PM
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I wanted some decals to complement the graphics I've put on the plane. I won't use them all for this project but you can only print to the sheet once. Three coats of clear Krylon should seal them just fine.







First step - cut out the decal.







Next step - a little Windex to clean the covering.







After placing the decal in a dish of water, I dab a bit of water on the covering, take the decal out and slide it into place. After positioning, some careful blotting with paper towel and it's done. I let decals cure overnight before flying.


Old 04-11-2015, 04:04 PM
  #408  
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Ignition and receiver switch decals.







A little website plug under the my logo and a maple leaf on the rudder.







I got pretty close to the MonoKote maroon - I scanned a scrap of it and used that colour for the decals.
Old 04-11-2015, 05:19 PM
  #409  
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Ignition cutoff enabled - here you can see the exterior red LED and the green LED on the cutoff transmitter module inside.







I also got the control servos set up - not really picture-worthy but direction, sub trim, end points, rates and expo are all set up.


I want to try the airbrake feature too... it will, of course, be tested three mistakes high... but I wasn't sure what to do with the elevator. I guessed that with the ailerons at the back of the wing and behind the CG, deploying the airbrakes would tend to raise the nose, so I added a little down elevator to counteract that. They're set to come on gradually so as to avoid sudden attitude changes.


Thoughts?
Old 04-12-2015, 08:29 AM
  #410  
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Originally Posted by grosbeak
Ignition and receiver switch decals.







A little website plug under the my logo and a maple leaf on the rudder.







I got pretty close to the MonoKote maroon - I scanned a scrap of it and used that colour for the decals.
Please. what product and printer are you using for the water-slide decals? They look terrific!

Sincerely, Richard
Old 04-12-2015, 12:26 PM
  #411  
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Originally Posted by spaceworm
Please. what product and printer are you using for the water-slide decals? They look terrific!

Sincerely, Richard
Hey Richard,

The printer I am using is nothing special - it's an Epson NX420 MFD that's several years old. I am using the Testors 8.5" x 5.5" clear decal paper because my LHS stocks it, and the decals were designed with Microsoft Visio. They get three light coats of clear Krylon and at least 24 hours of curing time before they are cut and applied to the plane.

I have sourced 8.5" x 11" sheets at decalpapers.com but their shipping prices to Canada are too expensive.
Old 04-12-2015, 05:43 PM
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Nice day to fire up the engine for the first time (first time for me - I bought it used). Tethered on the table outside.







Like my DLE 20 and RCGF 32, this DLE 30 does not want to flip-start cold - I left the windshield off so I could see the tank and it's just not drawing fuel with hand flips. But the drill did a fine job as usual.





There was an issue with delayed idle so I cracked the low end open a tiny bit. That solved the problem.


- - -


So, you may ask, why didn't you just take it to the field, start it, tune it and fly it?


My usual answer is that I like to tune my engines at home. It doesn't come naturally to me and I like to take my time and follow a set procedure. For any plane that I'm starting for the first time I also like to see if any problems make themselves apparent, and in this case there were 3 of them.


To start with, there was some oil spatter on the table. I expect that, but I also noticed that there was some spatter on the firewall and the top of the muffler. Looks like I need to check out the seal between the engine and muffler.







The other two were inside. The first thing I noticed as I was packing the plane up was that the pull-pull cables for the rudder were slack. What the?! I looked inside and the arm was off the servo... looks like I forgot to reinstall the screw!


The second issue was with the receiver - it had slipped out from under the velcro tie. Both issues are fixed now.


Either of the latter two issues may have proven fatal to plane if they had happened in flight... so it only reinforces my habit of test running the engine of any new plane at home first.
Old 04-12-2015, 06:54 PM
  #413  
52larry52
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+1 on running your engines at home before heading to the field on any new build, rebuild or engine swap (new engine or used engine it doesn't matter). Home is the place to get the little bugs out. The other thing I like to do in conjunction with testing and tuning the engine in the airframe is to do a Taxi test of the plane in my yard both on my paved driveway and on my lawn to simulate both types of runway. Just another thing to have the plane truly ready to fly when you do head to the field. Looks like you had a nice sunny day today in the" great white north", it was overcast and sorta crappy here in the "tropical west Georgia" area today but I flew anyway. Looks like maybe next weekend for your new bird? Yes? It looks good.
Old 04-15-2015, 08:58 AM
  #414  
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Originally Posted by 52larry52
+1 on running your engines at home before heading to the field on any new build, rebuild or engine swap (new engine or used engine it doesn't matter). Home is the place to get the little bugs out. The other thing I like to do in conjunction with testing and tuning the engine in the airframe is to do a Taxi test of the plane in my yard both on my paved driveway and on my lawn to simulate both types of runway. Just another thing to have the plane truly ready to fly when you do head to the field. Looks like you had a nice sunny day today in the" great white north", it was overcast and sorta crappy here in the "tropical west Georgia" area today but I flew anyway. Looks like maybe next weekend for your new bird? Yes? It looks good.
Taxi test - should have thought of that! I only fly off grass, and it's a lot smoother than my bumpy, clay-filled yard...

Hopefully next weekend or the one after!
Old 04-15-2015, 06:00 PM
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If you can taxi it on your "bumpy, clay filled yard" then it passes the taxi test !
Old 04-16-2015, 09:07 AM
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Old 04-20-2015, 12:35 AM
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The maiden flight was yesterday. The best way to summarize it is, "All's well that ends well."


The plane taxied well and responded well to rudder-controlled steering on the ground. In position facing into a mild headwind it took off in 50 to 75 feet at about half throttle in a nice level attitude - just floated off the ground.


In the air, things started to get hairy. When banking for the first turn, the low rates I had selected based on the manual didn't give me enough aileron authority... so I switched to high rate. The tail tended to drop - a lot - in turns. And even though the plane is perfectly balanced according to spec it flew like it was tail-heavy. I was flying a downwind leg on the third circuit working on the trim with a buddy at about 3 mistakes high when a small shiny object detached itself from the front of the plane - the spinner. As high as it was I decided to bring the plane in - on the crosswind leg there was a change in the engine note - a kind of rattling started. And on final, still descending and going too fast, the engine quit and I saw that the prop had gone too.


I ran out of runway but managed to set it down in the muddy outfield in one piece - from what I can see there is no damage to the airframe (that's the "ends well" part but I will be going over it thoroughly). But the single bolt prop adapter I had installed on this engine sheared all four of its bolts and disappeared. We walked the field but did not find it.








This is not the first time I've used a single bolt prop adapter - there's one on the RCGF 32 that powers my Pulse 125 - it's had a few flights and has been fine.


So now I've got to wonder - was the adapter, purchased new from Valley View RC - defective? Or was the engine - purchased used on RC Canada - involved in a crash that may have bent the crankshaft? I take full responsibility - caveat emptor and all that - but I have contacted the seller with the question, which I should have asked before I bought the engine. I'm hoping for an honest answer but if the response is "no crash" than I'll have to decide whether to take that on faith.


In the meantime I think I'll check the runout on the prop hub with a dial indicator. We'll see what, if anything, that reveals.


If I'm being honest myself, I should have seen this coming. When I test-ran the engine on the plane the weekend before this, I could see vibration in the prop arc. I thought at the time it was just due to the vibration of the plane at idle but I've since realized that I've never seen wobble like that in an idling engine before. Live and learn.
Old 04-20-2015, 04:20 AM
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Hmmm... on first glance it looks like you may have over-torqued those prop bolts, fatiguing each of them.
Old 04-20-2015, 04:51 AM
  #419  
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Originally Posted by DMehalko
Hmmm... on first glance it looks like you may have over-torqued those prop bolts, fatiguing each of them.
I've usually got a pretty good feel for that stuff but anything is possible...
Old 04-20-2015, 12:25 PM
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Interesting. Did you find the prop? If so, can you post photos? Would especially like to see the hub where it contacts the flange.
Old 04-20-2015, 12:50 PM
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Originally Posted by DMehalko
Hmmm... on first glance it looks like you may have over-torqued those prop bolts, fatiguing each of them.
What grade of bolts are specified/used? What torque value is specified? Thanks.
Old 04-20-2015, 01:08 PM
  #422  
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grosbeak - sounds like to me that you know what happened. Bummer.....but kudos on the save!
Old 04-20-2015, 01:29 PM
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Originally Posted by grosbeak
The maiden flight was yesterday. ...
In the air, things started to get hairy. When banking for the first turn, the low rates I had selected based on the manual didn't give me enough aileron authority... so I switched to high rate. The tail tended to drop - a lot - in turns. And even though the plane is perfectly balanced according to spec it flew like it was tail-heavy....
Sounds like adverse yaw, and you need to add aileron differential. Also, you may need to add rudder to lift the tail on turns. Much like a Cub needs the same for coordinated turns. Good luck.
Old 04-21-2015, 02:56 AM
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Originally Posted by Lone Star Charles
Interesting. Did you find the prop? If so, can you post photos? Would especially like to see the hub where it contacts the flange.
Unfortuately I did not.

Originally Posted by spaceworm
What grade of bolts are specified/used? What torque value is specified? Thanks.
Whatever Valley View RC provided with the prop adapter - I have no idea.

Originally Posted by R/C Art
grosbeak - sounds like to me that you know what happened. Bummer.....but kudos on the save!
I do have my suspicions... and thanks!

Originally Posted by spaceworm
Sounds like adverse yaw, and you need to add aileron differential. Also, you may need to add rudder to lift the tail on turns. Much like a Cub needs the same for coordinated turns. Good luck.
Sounds like a plan - I figured I was forgetting something!
Old 04-21-2015, 02:56 AM
  #425  
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I am not a machinist or engineer, but this - 0.004" - looks to me like a bent crank.


https://youtu.be/nYN0fx3IRV4

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