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Avionics Wiring Conundrum

Foolishly, I decided to wire a rather complete G3X system myself. (This IS supposed to educational, right?) My question is this: How did you determine wire lengths and wire routings? The CAN BUS routing is straight forward, not so much for the rest of the connections. I can do the connectors OK, but defining the topography has me baffled. Your suggestions, please!
 
Sounds like fun.

Do you have a proposed wiring diargam to integrate all the things? That'd be step 0.
step 1 is deciding locations for all the things in your diagram.
step 2 would be measuring the routing from location to location.
step 3 logically draw it all out in a diagram of the plane
step 4 translate those measurements to a big sheet of plywood for your fullsize map to start cutting wires, the map


Ive never done it, but that'd be my approach.
 
There are a lot of ways to handle it. I wired my systems myself. The first thing I did was decide where every box was going to be located, and I mounted them. I looked around for where wires would run, where the grounding block would go, and things like that. I made sure that every box could be disconnected and removed with only the front panel removed (in my case a 10" display removed makes a big hole too).

It will save you $2000 in time to pay Stein $400 to give you the complete wiring diagram for your intended installation. He might not have charged even that much I can't remember but that drawing was worth every penny. I went over it with the manuals in full detail and made two minor changes that were simply what I wanted as there was no error in their drawings.

If you buy the equipment from Stein, they can kit up 90% of what you need to do the panel yourself. The rest is up to you..... and it is very educational. I could do the next one way faster than the first.
 
Harness by Stein

I was slow pulling the trigger on my ADSB installation because I told myself I was going to accomplish all the wiring / harness, etc. After a couple years of "naval contemplation" (procrastinating), I contacted Stein about a harness for my Trig TT31 / TN72 / new altitude encoder / new blade antenna. Difficult task made simple. I mounted the equipment, Stein did the harness. I plugged and trimmed excess wires / cables.

At a minimum, I would recommend getting a quote from Stein if you are "stuck".

Having Stein build my harness was a big win and my ADSB performance report is "clean" (once I figured out you need to put "N" in front of your registration number in the transponder).
 
Wiring Do it yourself

I'm doing my avionics wiring on my own. Here are the steps I'm following.

1. [done] Create a wiring diagram. As someone mentioned the Steinair diagram is rather expensive. I used Autocad web (free) and the G3X manual plus other Garmin manuals to create a DWG of my wiring. This was pretty straightforward and every educational albeit tedious. After doing this I felt very confident moving foward with the harness

2. [done] Figure out mounting locations and wire runs. I researched this on this site, facebook, talking with steinair, etc. This wasn't hard.

3. [done] Figure out harness lengths. I used this spreadsheet from Dark Aero. It is very very useful for documenting locations, devices, wiring lengths, etc..

4. [planned] Run main and aux power buss wiring

5. [planned] Mount all subpanel devices on the bench before installing subpanel

6. [planned] On my pooltable w/ping pong board map out all the locations w/ distances and lay out my wires based on the spreadsheet above. While also labeling each wire at each end

7. [planned] run wires in plane

8. [planned] install connectors

9. [planned] Profit!

Other considerations: I also did some analysis of how much conduit I would need under the baggage area and through the firewall which I didn't mention above. I'd be happy to give details.
 
did it myself

I did it myself.
1) took 2 months of nights, after working on plane all day, to build schematic using the wonderful diagrams in G3x manual.
2) spent 2 days figuring out where boxes were located to have access after top skin was on.
3) spent 3 months cutting sub-panel, mounting plate nuts for those boxes and wiring.
4) spent 2 months putting it all together and getting it in the plane

Things i would differently:
1) leave longer service loops.
2) route wiring harness using right angle corners and grid type design, although there may not be enough space between boxes for a really pretty grid-type routing.

Things I didn't do that was OK:
1) i wired with the sub-panel assembled, but clamp to the bench; I didn't use a plywood wiring panel/jig
2) I labeled all the wires using the heat shrink tubing printed with a Dynon label maker; I would buy a portable one to have at the shop; I relied on a offsite computer to print labels and this was a pain when I was making a change.
 

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I did my own as well. Totally worth it. The next one will take no time comparatively.

- Don't be afraid to order more wire than you need.
- Getting the wiring right comes down to spending about $20 on 4-5" wire ties as you're going to tie those up and cut them off left and right. Just make sure you do cut them off or you'll wind up with a weird bump in your bundles... that's the wire tie you left in there when it was only 3 wires now its 15.
- print on shrink wrap!!!! My Dymo has been a life saver.
 
The advice to make or buy a LRU interconnect diagram is spot on. I chose to pay Steinair to do mine. All my components were purchased through Steinair, so they knew exactly what the configuration would be. (all Garmin).

Now...to answer you question on how to figure out the route and distance for wiring, here's what I did.

I used some small diameter rope and snaked it through the fuselage. This is how I figured out the route. Anywhere there was a branch to a LRU, I taped some parachute cord to the main rope and marked it with the LRU name. All the twists and turns were simulated with the rope and cord, all the service loops were determined and precise lengths were measured.

This harness was built on a table and then installed in the fuselage. All the termination that could be completed were. The terminations that had to go through grommets and small openings were terminated after installing the harness in the fuselage but all the pins were already crimped. One could probably use the rope and cord method but build the harness in the fuselage but that seems harder to me. I also did a triple continuity check before installing the harness in the fuselage...I also made a pinout book.


Here is a link of a very boring but informative video to the rope and cord in the fuselage.

Here are photos of the process.
 

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I did it myself.
1) took 2 months of nights, after working on plane all day, to build schematic using the wonderful diagrams in G3x manual.
2) spent 2 days figuring out where boxes were located to have access after top skin was on.
3) spent 3 months cutting sub-panel, mounting plate nuts for those boxes and wiring.
4) spent 2 months putting it all together and getting it in the plane

Things i would differently:
1) leave longer service loops.
2) route wiring harness using right angle corners and grid type design, although there may not be enough space between boxes for a really pretty grid-type routing.

Things I didn't do that was OK:
1) i wired with the sub-panel assembled, but clamp to the bench; I didn't use a plywood wiring panel/jig
2) I labeled all the wires using the heat shrink tubing printed with a Dynon label maker; I would buy a portable one to have at the shop; I relied on a offsite computer to print labels and this was a pain when I was making a change.
nice project!! who makes this heat shrink tubing and how does a DYMO print on it? last time i looked it prints flat labels that weren't all that great. have any pics to share as an example?
 
Here are photos of the process.

I’m admiring your workmanship, sure. But I’m admiring that beautiful piece of plywood you laid it out on. These days, that has to be worth at least the same as your avionics?
 
Thank you.. thank you very much = Elvis

nice project!! who makes this heat shrink tubing and how does a DYMO print on it? last time i looked it prints flat labels that weren't all that great. have any pics to share as an example?

Thanks for the complement. My next one will even be better. :eek::eek:

The Dymo heatshrink tubing is available on Amazon thru third parties, or Dymo directly. I used two sizes, 1/4 “ and 3/8”. It supposedly shrinks more than regular heat shrink. The 1/4” works well for individual wires. I alos picked yellow so I could see where the label was on white wire.
 
The advice to make or buy a LRU interconnect diagram is spot on. I chose to pay Steinair to do mine. All my components were purchased through Steinair, so they knew exactly what the configuration would be. (all Garmin).

Now...to answer you question on how to figure out the route and distance for wiring, here's what I did.

I used some small diameter rope and snaked it through the fuselage. This is how I figured out the route. Anywhere there was a branch to a LRU, I taped some parachute cord to the main rope and marked it with the LRU name. All the twists and turns were simulated with the rope and cord, all the service loops were determined and precise lengths were measured.

This harness was built on a table and then installed in the fuselage. All the termination that could be completed were. The terminations that had to go through grommets and small openings were terminated after installing the harness in the fuselage but all the pins were already crimped. One could probably use the rope and cord method but build the harness in the fuselage but that seems harder to me. I also did a triple continuity check before installing the harness in the fuselage...I also made a pinout book.


Here is a link of a very boring but informative video to the rope and cord in the fuselage.

Here are photos of the process.

For those wondering, the particle board was purchased pre-COVID, so it was less than the cost of the avionics ;)

attachment.php
 
nice project!! who makes this heat shrink tubing and how does a DYMO print on it? last time i looked it prints flat labels that weren't all that great. have any pics to share as an example?

I use a Brother label maker (https://www.amazon.com/Brother-PTH110-Portable-Lightweight-One-Touch/dp/B01J3WQ360) and these 3rd party heat shrink tubes (https://www.amazon.com/SuperInk-Compatible-Brother-HSe-211-PT-P750WVP/dp/B07H95SPBF). Like old VHS tapes, sometime you have to add a piece of tape to the cartridge so the Brother recognizes it correctly, but besides that its been a cheap and easy solution.
 
Addressing the concern about getting all the harness lengths right, specifically avoiding the disaster of being an inch short somewhere, the approach I have taken is to deliberately make runs a bit longer than measured/modeled, and then terminating/connectorizing in place in the plane, not on the bench. A bit of a pain to do in the airplane, but that way you can get all the lengths and service loops exactly right and the locked down bundle routes neatest.
 
Apparently I failed to complete the upload to my Youtube video, thats been rectified.

Heres the link to the video....again

In the video, the mock harness I'm describing goes from the aft fuselage DB15 to the panel and then back to the right wing. I had already completed the harness from the GMU11 to the pitch autopilot servo, ending with a DB15 connector..
 
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