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Cessna L19 Bird Dog

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Cessna L19 Bird Dog

Old 06-17-2013, 08:59 PM
  #26  
Nodd
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Default RE: Cessna L19 Bird Dog

Radio Tray - Take II
Here's the new radio tray, pretty ain't she...



Gone from the tray is the SBEC & the capacitor. I've reoriented the receiver so the antennas are further away from the servos. I also stuck the receiver up on a block so I can get my fingers under & around the servo plugs...



The SBEC & capacitor are mounted along the fuselage side, away from the receiver...



So hopefully this layout is a little more radio friendly...



Today I also got the motor & ESC wired up & mounted. I replaced the stock bullet connectors with some nice heavy duty ones...



So the bulk of the electronics are hooked up & in place, sweet...

Old 06-18-2013, 06:58 PM
  #27  
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Default RE: Cessna L19 Bird Dog

Wing Hookup
Today I spent an hour or so building the wiring harness to go from the Rx to the wing...



And with that, the electronics are done, woohoo!...



CLEAR PROP!
It was finally time to fire up this bird-puppy...



I took her outside for the actual first run of the motor, didn't want walls around me for parts to bounce off. I ran her up to around 50%, "BLOODY HELL!" I said to my self, scary power. I don't want to push her much further until I have my watt meter hooked up. Unfortunately I don't have the right connectors to make that work right now though. I do have the Castle Creations USB doohickey though, could see how she's performing on the computer instead, will have to read the manual some. One thing for sure, this plane is not lacking for power. I did one more low power run (maybe 20%) on my work-bench, then removed the prop & disconnected the motor's leads. This motor I'm gonna treat with some serious respect...



Very nice to see everything is working.
Old 06-19-2013, 08:03 AM
  #28  
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Default RE: Cessna L19 Bird Dog

Hi Nodd very nice looking setup.

I am not sure how familiar you are with larger electrics and Castle speed controls, if this is old hat for you then please feel free to disregard. Looking at the setup Iwould estimate that with the prop/battery/motor setup you have you will be producing somewhere around 1200 to 1000 Watts pulling between 50 to 60 amps. As you said this is not a trivial amount of power, the prop would be spinning around 8000 to 8500 RPM, that would be real hard on anyones fingers. You mentioned in your post that at half throttle you saw a considerable amount of power, my guess is that your speed control (SC) is at default settings and thus your throttle endpoints are set to AutoCalibrate. This means each time your SC initiates you need to teach it where the full throttle is set. To do this you run the throttle to full and leave it there for a couple of seconds, then pull it back a bit and your motor should slow down, close throttle, now you are set. The next time you fire the motor up watch the speed control, there is a red light on it as you move the throttle up once it starts to flash the speed control is wide open. My guess is your half throttle test run was very close to full. If you do not like the thought of auto calibrate you can set it to fixed endpoints and adjust it as you would like. To do this you will need to plug the SC into the Castle Link and your computer.


Good Luck, its a great looking project!

Cheers
Old 06-19-2013, 03:51 PM
  #29  
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Default RE: Cessna L19 Bird Dog

Some great points & advice there Rick, thank you.

I've put together several electric planes now but this is by far the largest. This is also my first experience with a Castle Creations ESC but I'm familiar with all the usual functions. I did lots of research & discussed the setup at length with some very knowledgeable e-tow pilots over at RCAerotowing.com. I also ran everything through eCalc a bazillion different ways (here's the current setup). Your estimations are pretty much what we're expecting, yeap.

That's an interesting point about the ESC's auto calibrate feature. No way of knowing if she achieved full power while I was testing *shrug*. I'm not too worried either way, that was just a test. I'll set her up properly soon enough, get the USB cable hooked up & program all the goodies. I'm really looking forward to that stuff, love tinkering with settings. I'm really excited about the data logging feature too. Fun Fun.
Old 07-01-2013, 07:46 PM
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The Move
Where the heck have I been? Well I decided to move my entire workshop into a new dedicated, RC only, space. Here we have the workbench installed. That's probably the last time it'll ever look that clean LOL...



See I've already messed up the workbench...



Windshield
Test fitting the front windshield. Naturally it doesn't quite fit...



Before that goes on though, I added these scale support strut things. Unlike the structural ones in the rear window holding the aerotow release in place, these are just for looks...



There's all sorts of options for gluing clear plastic canopies. I've found this stuff does a fair job...



Wing Struts
I've never done struts so making this up as I go. What ever I design, it has to include a quick release system...



The notches cut into the metal rods help give the epoxy something to grab onto. The cotter pins should make life easy when its time to install/remove the struts...



This aluminum bar doubles as a support for the main gear & as an anchor point for the struts...



The bar bolted into the fuselage...



The ends of the bar protrude through the sides of the fuselage where the struts connect...



Pretty sure that'll be good & strong, yet quick-n-easy to setup at the field...



The Other End
On the underside of the wing I made up these little bracket doohickeys to mount the other end of the struts too...



I'm using the same cotter pin system here but these need a 90° angle. Annoyingly my hardened piano wire rod cracked when I attempted to bend it that much, bugger!...



No big deal I thought, I'll try heating it first...



Well that didn't work...



I'm thinking I need to bend these first & then drill the holes for the cotter pin *sigh*

The Tail
I'll deal with the struts later, time for something a little less metallic...



There's a big gap under the vertical stabilizer, obviously I need to fill that in with some wood. I don't like that the v-stab will just be glued on top of that though. I'd prefer something a little more structural. So I decided to make a new v-stab, one that extends all the way down to the h-stab. And while I'm at it, lets make it just a smidgen larger...



As you can see the new v-stab will be bigger than the old one. As long as I don't tell anyone, nobody will notice it's not quite scale *wink*. I figure for aerotowing, a tad more yaw stability can't hurt. Here's the new v-stab roughed out & gluing...



While that's drying I decided to start covering on the h-stab...



And that's a wrap for now, I'll have more to show soon...

Old 07-02-2013, 05:47 PM
  #31  
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Default RE: Cessna L19 Bird Dog

Now why didn't I think of that earlier?
I spent an hour or so today visiting various industrial supply outlets & even a welding supply store. Fascinating places but do you think any of them had 1/8" plain steel rod? Nope. Then it hit me... how many times have I bent a nail trying to hammer it home? NAILS! of course...



And wouldn't you know? This stuff drills like, well a hot drill through butter...



Piece of cake...



There we go, some bad-arse struts...



Happy with those I got down to shaping the new v-stab...



She looks like she wants to get off this workbench & fly already. Soon enough :-)

Old 10-13-2013, 06:35 PM
  #32  
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There's dust on my Bird Dog!



Okay after goofing around with other projects for three months I'm actually back working on this. Yay!

If you recall I made a new vertical stabilizer, slightly larger & with a tab on the bottom that I figured might make a stronger joint...



That was great but I just can't get past how heavy the new tail is...



So I'm going to toss the heavy new tail & use the old one after all. But I'd still like some mechanical way to mount it to the horizontal stabilizer rather than just gluing it on top. So here's my solution...



This piece of hardwood sticking down into the tail will help make a better joint. Here's the new weight...



In the meantime I set the plane up on two identical chairs so she's sitting perfectly level with my bench. That'll help when its time to attach the horizontal stabilizer. I need that to be nice & level with the wings...



Also getting ready to square up the tail with the fuselage. Putting the tow release to work already...



That's all for today. Very nice to be back working on the old gal. We'll get her flying soon enough (& yeah you've heard that one before).
Old 10-14-2013, 07:34 PM
  #33  
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The Tail
I need to carve a piece of wood to sit on top the horizontal stabilizer so that it blends in nicely with the top of the fuselage. It's a lot easier to do that before the tail goes on. So I created this plywood stand-in for the h-stab...



Next I CA tacked a block of balsa to the stand-in & got busy with the shaping...



Popped the balsa off the stand-in then gave her a test fit, looks good...



Hollowed out some of the underside to save weight then bored a hole to accept the rudder post...



Time to glue the horizontal stabilizer to the fuselage...



That's looking pretty square...

Old 10-19-2013, 05:23 PM
  #34  
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Vertical Stabilizer
Time to get this mounted...



Added my fillet piece...



I figured it'd be easier to cover the v-stab before its mounted...



Ladies & gentlemen we have a tail...

Old 10-20-2013, 05:24 PM
  #35  
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OOPS!
How come no one, myself included, noticed my tail is all wrong... WRONG!

A guy over at RCGroups correctly pointed out the counter balance part of my rudder & elevator is attached to the wrong part of the tail...



Well in my defense I didn't actually build this tail, this is the way I got it. I have no clue why the original builder put it together this way, guess we'll never know?

The question now is should I take the time to put it right? There's actually a really good argument for keeping it the way it is though. I've seen other tow planes that have counter balanced control surfaces experience issues with the tow line catching on the control surfaces. The line snags the pointed part & gets stuck in the gap between the stab & control surface. With the counter balance on the other part, problem solved, hmmm. So we're going to pretend we did it this way on purpose, so the tow-line doesn't snag... yeah that's why its this way :-P

Paint
I've decided to paint the corrugated control surfaces instead of cover them. It's less work & should look better. Applying the primer coat...



I'll be laying down coats for a while tonight, no need to photo each step. So that's all I'm posting for today.

Last edited by Nodd; 10-20-2013 at 05:31 PM.
Old 11-23-2013, 07:01 PM
  #36  
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Wing Mounting System
I thought I was done with this but I'm not happy with my wing mounting system...



Specifically I don't trust these wimpy little wooden dowels. They're made of soft pine & they're pretty short. It wouldn't take much to either break these or pop them out during flight...



So for the second time now, I opened up the wing...



I drilled out the center dowel & replaced it with a length of brass tube...



Cut the brass tube & capped both ends with epoxy...



While that was drying I got rid of the old wooden dowels, cya!...



Glued in the brass tube...



Re-sheeted & closed up the wing...



I drilled a matching hole in the top of the windshield & then glued the brass tube into that end too...



Use a hack-saw blade to cut the brass tube...



Now I have two pieces of brass tube perfectly aligned, one in the wing & one in the fuselage...



A short length of carbon-fiber...



Pop that into the brass tube...



And we're good to go...



I only have carbon-fiber rod in the correct size right now but I plan to swap that out with some carbon-fiber tubing. I want that to be a failure point in a crash but this CF rod is way way too strong. Anyway I'm feeling much better about the way the wing is mounted now. Those stupid wooden dowel nubbins were scary.

Home Depot Color Matching
So I schlepped on down to the hardware store with a roll of green Ultracote under my arm. The dude in the paint department didn't seem at all phased when I asked him to color match me some paint. I guess he's seen it all...



What's nice is they'll sell you a sample sized pot of custom paint (7 FL OZ (200 ML)) for a few bucks. You don't have to buy gallons of the stuff.

My elevator & rudder already primed...



This small airgun was a bargain at Harbor Freight. It's perfect for small jobs like this...



And we have green tail-feathers...



So much for the Home Depot's deluxe color matching system LOL...



I just want to get this thing flying already, not too worried about it.

Last edited by Nodd; 11-23-2013 at 07:28 PM.
Old 11-24-2013, 02:37 PM
  #37  
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Apparently mismatched paint is a Bird Dog tradition
Jim over at RCAerotowing.com pointed out the screwy fullscale paint in a photo I'd used earlier in this thread. Now I feel better LOL

Old 11-24-2013, 08:26 PM
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Glad you're enjoying it *smile*

The Wing
Today I started the prep-work for covering the wing. I printed these templates for the graphics...



All was going well...



And then I realized there was still work to be done before I could cover the wing. First I added this small piece of trailing edge to the center area...



And although I've been putting this off & thinking about possibly ignoring it, the trailing edge where the flaps go is somewhat warped...



Its kind of hard to photograph, maybe this super nifty sketch illustrates what's going on...



Its not actually that bad, I exaggerated somewhat for clarity but its not good. So I soaked the area with water...



I then clamped blocks of wood to the wing, hopefully tomorrow things will have improved...



So even though I didn't get the wing covered today, I feel good about at least trying to do something about the warped TE.
Old 11-30-2013, 07:03 PM
  #39  
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The Wing (continued)
My trailing edge seems to be a lot better...



Finally getting the wing covered...



The florescent green Ultracoat is seriously bright, I like it!...



Next is the dark green...



The wing's bottom is black. I opted to paint the recesses for the fowler-flaps instead of trying to cover those areas. Heat-shrink covering generally isn't good on concave surfaces, tends to pull away...



After the heat-gun, no more wrinkles...



Top side finished too...



Pretty happy with the results...



Glad to get that complete finally. More to come shortly...

Old 12-06-2013, 04:28 PM
  #40  
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How's thing comming?
Old 12-07-2013, 08:10 PM
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Things are a little slow but we're making progress...

Control Surfaces
I attached the ailerons & flaps. I also added some bold white panels to the wing's underside to help visibility on overcast days...



Hooked up the ailerons...



Those seem to be working nicely...







80% servo travel, 20% differential, 30% exponential

The wing looks a lot beefier with the trailing edge controls attached, liking those corrugations...



Next step is to get the fowler-flaps functional...

Old 12-08-2013, 06:40 PM
  #42  
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Two Fowler Flaps - One Channel - Zero Fun
My Spektrum DX7s transmitter maxes out at seven channels. This airframe ideally needs eight channels, with two devoted to the flaps. Wth the limitation of my radio however I'm forced to use a Y-harness for the two flap servos. I knew setting up these big fowler flaps with no electronic means to fine tune them was going to be a challenge. And guess what, it was.

Here's the fowler flaps before connecting them to the servos...



The linkages run internally which is nice but complicates any adjustment process. Here they are both hooked up...



Time to see how they work out. I adjusted each so they were even when closed...



At half flaps things are still close but we're starting to seem some drift...



And at full flaps we're way off...



Grumble Grumble Grumble
I more or less expected this but was hoping by some miracle I'd get lucky... nope. With no way to adjust these electronically I had to figure this out mechanically... oh joy. After poking around I discovered the culprit. This is where the servo linkage attaches to the flap...



As you can see these guys weren't installed accurately...



So I yanked one out...



I drilled a new hole & re-installed the pin & what'd ya know, it worked! Both flaps travel the same amount (plus/minus a degree). Close enough, that'll work...



So that actually wasn't as bad as I expected, very happy to have those working.
Old 12-27-2013, 08:33 PM
  #43  
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Rudder & Elevator
I'm happy to report I have a functional tail. Today I hooked up the rudder pull/pull system & also the elevator...



I was a little concerned about the clearance between the rudder pull/pull system & the elevator's control horn. It worked out fine though...



I have to say I'm pretty impressed with the Dubro pull/pull hardware. Nice quality kit...



Next I need to find some springs to connect up the tail wheel steering...

Old 01-12-2014, 08:08 PM
  #44  
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POS Tail-Wheel
Okay so I hooked up my steerable tail-wheel & guess what? It don't steer!...



I tried lots of different springs, the rudder turns but not the tail-wheel...



Turns out the tail-wheel baring was shot. It'd bind under any sort of load. No good...



So after some digging I was able to remove the old tail-wheel assembly...



I've heard good things about these Sullivan tail-wheels. Buying these online I couldn't get a feel for how beefy they were so I bought two different sizes. Either will fit but I'm going to use the heavy duty 10 to 22 lbs version. Tow-planes do a LOT of take off & landings...



I'm going to wait until she's covered before installing this but this test fit looks pretty good...



Rear Window
I'd been dreading installing this bugger. Nothing quite fits right on this model so I knew this was going to be a challenge...



After some futzing, reshaping with the heat-gun, lots of clamps, pins & bands I was able to wrestle it into position...



Side Windows
Hmmm what to do here...



Template time! Using the photo above I created these adhesive backed templates on the computer...



Used the template to cut my windows out of clear plastic...



Gluing the windows on...



Masking time...



Paint...



That's looking good...



Fuselage Graphics
I needed a way to transfer my graphic design to the actual fuselage. What I'm doing here is using my computer to calculate the height the stripes are off the work bench every 5cm...



Flipped the old girl on her back...



Made tick marks on the fuselage based on my computer measurements...



Used some wax paper to trace the tick marks...



Belly template ready to go...



I hate compound curved surfaces. Lots of scary wrinkles, don't fail me now Ultracote...



We like Ultracote, we REALLY like Ultracote...



Time for some fluorescent green goodness...



Mmmm minty!...



Pretty happy with the way this is going. Its late so that's all for now, will finish the covering shortly...

Old 02-04-2014, 06:33 PM
  #45  
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Finishing up the Covering
More fun with wax paper templates...



And we're done with the covering, woohoo!..



Wheels
Installed my fancy new Sullivan tail wheel. I have to say I like the design especially the way it indexes the rudder using a spring rod. That's brilliant...



That seems to be working nicely...



The 5" main gear is installed also. She's a roller now...



Engine Cowl
Ready for paint...



Primer...



Paint...



After all the trouble I went through trying to match the color of my tail feathers to the green Ultracote, turns out Hunter Green Rust-Oleum is a near perfect match...



My original design called for these fun shark teeth...



However after seeing her without the shark teeth I think we're going to leave it be. She looks slick as is...

Old 02-15-2014, 04:45 PM
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Battery Tray
This beast is way too big for my home-brewed balance stand so a couple of chairs will have to do. After futzing with the battery location I have her balanced, no need to add any nose or tail weight...



Marked the pack location on the battery tray & added Velcro...



My straps aren't exactly centered on the pack but I think they'll be fine. Nice that I have lots of room to reposition the pack if I need to adjust the CG...

Old 02-16-2014, 10:53 PM
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The Bench Test
It's finally time to see if my hardware will play nice together...

http://youtu.be/sKlJngxHaJ0
Old 04-04-2014, 09:57 PM
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With Spring in the air it's finally time to see if she'll fly...

http://youtu.be/9Gc_iCAVh8I
Old 04-06-2014, 07:20 PM
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Chris, Congrats on a successful maiden flight ! I have followed your Bird Dog thread for awhile as I have been doing a kit bash to also create a semi scale L-19. Your photos and build completion information have aided me in the bash. I started with a non L-19 high wing ARF and proceeded to modify it till it looks like a Bird Dog. Mine has a 54" wingspan and is powered with an O.S. .26 four stroke glow engine. I chose to finished mine as a white with red trim U.S. Air Force military version. The last of the paint and details got finished two days ago and I have yet to taxi test or fly it. May be next weekend. Thanks for sharing your L-19 adventure as it informs and inspires others. Cheers
Old 05-23-2014, 07:35 PM
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Good deal Larry, glad to hear this build-log helped.

So yeap my Bird Dog flies but will she tow?...

http://youtu.be/nYTFvOQt3bs

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