Scale Build-Off – 140" C-47 Foamy

ScottyWarpNine

Mostly Harmless
It's up to you. The harness would actually reduce the wires being routed through your wing tubes, and the pig-tail design is intentionally there so only the extension is routed, then the short harness is plugged in at the end, joining everything up. Everything still remains perfectly modular.

In this particular case, since you've also got retracts in the wings, you'd need to add on another row of pins and another wire to match . . . or build the whole extension out of a four conductor strip of ribbon cable, and provide servo power locally from the ESC

A distributed harness would work best with a small bay at the Nacelle for everything to join at. If you've built one to house the ESC behind the motor, that starts making more sense. Otherwise you get to feed servo extensions and power cables into your wing tube (granted you've got a bigger than average wing tube). Three extension runs + power cables isn't unreasonable, but you've got other options.

I'm not sure I follow 100%. Are you saying the aileron servo and gear servo would be powered locally by that wing's ESC's BEC, and just the signal and power wires are fed back throught the wing tube to the receiver? Then the receiver itself and the tail servos would be powered by my external BEC?
 

ScottyWarpNine

Mostly Harmless
I think one of my biggest concerns is the fact that I'm using cheap Chinese ESC's with cheap Chinese BEC's. I guess they have not given me any reason not to trust them, and my Castle BEC has no real reason for me to trust it more other than the fact that I spent a lot more money on it and I expect it to do it's job. I guess maybe I'm over thinking it. I'm sure and esc can control two servos just fine, right?
 

willsonman

Builder Extraordinare
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Put it this way... On my Top Flite AT-6 Texan I am using the built-in 5A BEC on my ESC to power 6 servos and one more retract servo (mechanical retracts) and have never had an issue.
 

Craftydan

Hostage Taker of Quads
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Your mistrust for lower cost gear is understandable.

If you can't trust the UBEC on the ESC to support less than the spec'ed servos, how can you trust it well enough to power the ESC's brain? the microcontroller wired into that monster transistor bank needs to be fed too . . . and if it goes hungry, the motor stops. A failure causing a strong Differential thrust may not be as catastrophic as an aileron servo failure, but at low altitude it can be devastating. Mac's B-29 is a fair example of this, and that was 1 out of 4.

The way I'd look at it, it's either designed to meet/exceed the spec, or it's not. The reviews for your ESC will be telling to that. People will complain even when they exceed the spec and it fails, and every complaint, valid or not, will cause a cascade of lost sales. The desire for long, high number production runs, will drive the design to exceed the spec by a reasonable margin. So go back and peruse the reviews -- that should give you a feel for how much you can/should trust it.

You probably can't take Wilsonman's evidence as a vote of confidence in YOUR ESC, but it is a good data point to prove it can be done.
 

willsonman

Builder Extraordinare
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To be fair, Mac's failure was due to oil from the IC engines getting into the servo/leads. With an electric plane this just does not happen.
 

Craftydan

Hostage Taker of Quads
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To be fair, Mac's failure was due to oil from the IC engines getting into the servo/leads. With an electric plane this just does not happen.

Very true -- and this project won't have a throttle servo, so I wouldn't expect the same failure mode, however the point is if one of these two engines suddenly goes out, the next few seconds of the flight will be . . . interesting.
 

ScottyWarpNine

Mostly Harmless
I think I'm going to do the setup described in your article. After reading some reviews of the castle bec I realized that it isn't without flaws either. I figure the best route would be to split up the load as equally as possible over my 3 BEC's there would be least chance of overload and failure. And if one of my ailerons were to go, I would still have a chance of retaining some control with the other. God help me if the tail goes.

Is my logic flawed?
 

Craftydan

Hostage Taker of Quads
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Passes a sanity check with me . . . but that assumes I'm sane enough to give a good check ;)
 

ScottyWarpNine

Mostly Harmless
My rudder hinge is just about done. I'm classing the rudder right now and working out the difficult wing Root fillet. Once that and wiring is done I can plank the bottom, then onto fiberglassing and painting and done!
Oh, and I have moved this big bird to the hanger Er I mean garage
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willsonman

Builder Extraordinare
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Indeed, looking nice. I would not worry about the wing faring until you have the bottom planked. Then secure the wing and make your filet. If you dont have any ideas on how to do the filet, check out Wilmracer's P-40 build or my Gee Bee Z Build. Both use essentially the same idea. Fill the area with foam and sand to shape. I used long strips while Wilmracer used small triangles.
 

wilmracer

I build things that fly (sometimes)
Mentor
The triangle method has the advantage of allowing you to cut most of the profile in before attaching the wing fillet, which minimizes sanding and shaping after the fact. It also makes it pretty easy to keep things symmetrical from one side to the other.

The downside is you'll be cutting TONS of them. The P-40 took two full evenings of just cutting at attaching wing saddle filler pieces before I could start spackling and cleaning it up. I haven't measured but I suspect your wing chord is even longer. It is nice that your wing doesn't separate from the fuse at the wing saddle line. Should make it easy to get a good clean seam from fuse to wing.
 

ScottyWarpNine

Mostly Harmless
The triangle method has the advantage of allowing you to cut most of the profile in before attaching the wing fillet, which minimizes sanding and shaping after the fact. It also makes it pretty easy to keep things symmetrical from one side to the other.

The downside is you'll be cutting TONS of them. The P-40 took two full evenings of just cutting at attaching wing saddle filler pieces before I could start spackling and cleaning it up. I haven't measured but I suspect your wing chord is even longer. It is nice that your wing doesn't separate from the fuse at the wing saddle line. Should make it easy to get a good clean seam from fuse to wing.

I just sorta planked it in. I have the fillet shape built into my formers so I attached a very thin piece of foam to the bottom to form the TE shape and I just planked over that. I'll need to sand it but it is looking pretty good. I'll take pics when I get home from work.
 

ScottyWarpNine

Mostly Harmless
Awesome work!!! That tail section must have been murderous to plank!

It's tharaputic once you get the hang of it. I'm pretty happy with how well the planking lined up with my carved tail. I guess my trimmed formers worked out just as they should.

My internet isn't working right tonight. It won't let me upload photos right now, but I've don't the wing fillet for both sides. I've flipped the fuselage over so I can wire it and planks the bottom tommorow evening. I still need to Hotwire the othe engine nacelle and carve some wing tips.

I am almost done 3d printing the main gears, but my printer decided this would be a good time to remind the world that it is a reprap and likes to be unreliable. Should be an easy fix, but that's one more thing to add to the list.

I'll try to post the pictures in the morning.
 

ScottyWarpNine

Mostly Harmless
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Elevator servos are placed. I went for quick and dirty since it is the bottom of the plane and I don't feel like hiding the linkages. I have more important things to worry about. Unfortionatly since it is a split elevator I have to run the two servos on separate slots on my receiver and program it into my radio. I wanted to put the ailerons on separate slots so I could program flaperons, but I don't think flaps will be necessary with how light (I hope) it will be.
I have 5 strands of wire going to the back of the plane. Two for servo power, and one signal line for each servo.
I have the edges of the hinge lines glassed so I can attach the elevators after I glass those surfaces. The rudder is curing now so I think I will be able to attach that prrminantly tommorow. The. Once I do some soldering I can seal up the bottom of the tail and aft fuselage forever.
The nose area is going to be getting some more attention pretty soon. I've decided not to have the removable fiberglass nose. Instead I will just have a large hatch on the bottom of the forward fuselage directly under the batteries. I have some ply epoxied into place to support the batteries. I'm thinking I'm going to slap a layer of fiberglass over all of that then make some holes to allow Velcro straps to pass through all the way around the batteries. I will use adhesive backed Velcro on the batteries and on the ply surface to prevent the batteries from sliding forward or backwards. That's the plan for now atleast. I really don't want them to move around. Their position is just a guess. They can be adjusted forward a couple inches in case she is tail heavy. If she is nose heavy I'll just have to add weight to the tail.
I bought a used canopy on Craigslist and i built it up to makes sure all of the parts are there. I sure hope it doesn't rain much for FTFF, since the canopy is really only big enough for my plane, and not much else!
 

wilmracer

I build things that fly (sometimes)
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Looking great! I have to admit I was a bit skeptical about this being flyable by FF but at this point I'm confident you can do it :cool:

I think we've all got our fingers crossed about the rain. I've got a big pop-up tent with 3 side walls and if we have enough people with shelters maybe we can put together some kind of airplane shanty-town.

I'm also bringing a box of emergency mylar blankets that can be used as tarps as well. They also have the added advantage of reflecting sunlight and heat, so they work great as sunshades and will protect foam models even in direct sunlight on hot days. I'll have plenty to cover the DC3.