RickWoodall

RickWoodall

Well Known Member
If anyone had a good link or comments on conduit it would be appreciated. I know very little about the electrical part, and I have not yet bought the aeroconnection book. I want to get conduit run so baggage floor can go in, and just wondered if anyone had a rough diagram or comments on conduit. if I run one conduit from firewall to back and one out to each wing is that adequate? Should I run a couple to the back and two out to each wing? Might be a dumb question but I just need to know, i suppose there is no harm in having a couple extra runs in the floor. Strobes, landing, taxi, nav light will all be going in, as well as gps, radios etc. Just not sure if wires can all go in one conduit or if they should be spread out, lighting in one conduit, others in seperate. Stuck in rivet mode...figuring out the wiring is a fall job.

Any links appreciated
 
Well, lots of questions here-------------

The desired final configuration of your plane will dictate how many conduits, and size and location.

Day VFR, and steam gauges VS full IFR, all glass, night etc.

Wiring for some things is not compatible with wiring for others-------AHRS/magnetometer wiring in same conduit as high side strobe lines for example. Transponder coax with any other wiring is also problematic.

I an in the middle of exactly what you are going through-----only I am working on a project some one else started. After drilling out the floor boards, I ran a total of 4 conduits under the rear seat area on the left side, and there is one on the right. -10, in case you were wondering about the "rear" and left/right thing.

I used flexible PVC conduit from Home Depot, 3/4" and PVC fittings to terminate the front end at a bulkhead. The stuff is meant for electrical use, commonly called "Smurf" tube around here by local electricians.

You need to sit down and figure out what needs to be run where, and make a plan. Things to consider are battery location, strobe---single power pack or three, ELT location, if glass cockpit, where are you going to put sensors for heading/compass, audio wiring, ETC ETC.

Time spent planning is way more efficient than time spent re-working something not well thought out.

Whatever you end up with, it is probably wise to put in extra just in case---------sure beats drilling out all those pop rivets.

Good luck,

Mike
 
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Mike S said:
Whatever you end up with, it is probably wise to put in extra just in case---------sure beats drilling out all those pop rivets.

Good luck,

Mike
Click to expand...

Mike is exactly right. Install extra conduit, or at least oversize what you install.

I've postponed buying and installing a single axis (roll) autopilot for at least 2 years because I didn't install extra conduit in the wings of my airplane when I built it. Getting the wires out to a servo mounted in the wingtip is a big problem for me at this point.
 
After installing your (oversize) conduit, leave a pullstring in place in the conduit tied off to something on both ends, so you can attach a wire to it at a later date and pull it through easily.
 
KB lamented:

I've postponed buying and installing a single axis (roll) autopilot for at least 2 years because I didn't install extra conduit in the wings of my airplane when I built it. Getting the wires out to a servo mounted in the wingtip is a big problem for me at this point.
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Kyle, the utility of the wing leveler is worth the effort to run the servo wires. How 'bout running a thinwall PVC pipe from the wing root to the inspection hatch, then another one from the inspection hatch to the wingtip. The pipe can be inserted via the wingtip through the lightening holes and secured to the ribs with a combination of adel clamps at the ends of the pipes. I believe the only interference problems will be around the bellcrank; that is why you want two pieces of pipe so you can work the cable about the bellcrank area.

I did something similar to this when I added the LRI indicator and its associated plumbing.
 
You don't need to worry about leaving a string inside the conduit so you can pull wires later. All you need to do later is to tie a string around a piece of cloth, cotton, tissue, whatever, and suck it through with a vacuum. Works great, and no need to worry about making sure the original string is tied-off, protected, etc.

If you already left a string in place, no problem, that will, obviously, work, also.

BTW, how did you get the string in there in the first place?

Tracy.
 
no PVC

I think most everyone uses rigid or flexible PVC for their conduit. The thinwall stuff made for lawn sprinklers is probably the best bet. However, I think that any conduit in the cockpit/interior should be metal, not PVC, for the same reason we should be using Tefzel or Teflon wiring insulation, not PVC. When I did mine, I ordered the thinnest wall aluminum 6061 3/4" tubing that ACS had, and I used that. See here for example:

http://meyette.us/BaggageFloorAccessPanels.htm

The aluminum costs more, but I don't think PVC conduit in the cockpit is a good idea, and steel conduit is way too heavy

brian


 
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oh - and I clicked "send" too quickly - I certainly agree with the others' postings - if in doubt, add the conduit, if in doubt as to size, go bigger.
brian
 
brian said:
The aluminum costs more, but I don't think PVC conduit in the cockpit is a good idea, and steel conduit is way too heavy
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You have my curiosity up on this statement. Why don't you think using PVC conduit in the cockpit is a good idea?
 
thallock said:
You don't need to worry about leaving a string inside the conduit so you can pull wires later. All you need to do later is to tie a string around a piece of cloth, cotton, tissue, whatever, and suck it through with a vacuum. Works great, and no need to worry about making sure the original string is tied-off, protected, etc.

If you already left a string in place, no problem, that will, obviously, work, also.

BTW, how did you get the string in there in the first place?

Tracy.
Click to expand...

Obviously that's the easiest way to get the string in there in the first place - but keep in mind that some years down the road you may have difficulty getting enough access to the conduit to put a vacuum line on it. If you install the string early in the process while you have plenty of work room, you don't have to worry about messing with a vacuum later.
 
RickWoodall said:
If anyone had a good link or comments on conduit it would be appreciated. I know very little about the electrical part, and I have not yet bought the aeroconnection book. I want to get conduit run so baggage floor can go in, and just wondered if anyone had a rough diagram or comments on conduit. if I run one conduit from firewall to back and one out to each wing is that adequate? Should I run a couple to the back and two out to each wing? Might be a dumb question but I just need to know, i suppose there is no harm in having a couple extra runs in the floor. Strobes, landing, taxi, nav light will all be going in, as well as gps, radios etc. Just not sure if wires can all go in one conduit or if they should be spread out, lighting in one conduit, others in seperate. Stuck in rivet mode...figuring out the wiring is a fall job.

Any links appreciated
Click to expand...
Just for the sake of an alternative perspective, I'm going to argue contrary to the previous posts. The types of wiring you suggest above sounds like you are building a VFR plane. In this case, a single conduit running out to each wingtip, using conduit supplied by Van's should be more than adequate for the wings. If you are building a side x side RV where you want to keep weight forward, the only thing you really need to get to the back is the tail strobe light so don't even add conduit in the fuselage, just use some clamps every so often. Moreover, much of your wiring in the fuselage can be run under the canopy decks or through the center tunnel where conduit serves no real purpose that clamps by themselves wouldn't also address.

If you really need to add more conduit, then do it, and many threads have some good ways to do it, but I'd suggest firming up where and what you think you'll need before just adding more or bigger holes or conduit for the sake of adding more or bigger holes or conduit.

Again, just a different perspective. Good luck.
 
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As opposed to non toxic smoke?

Thanks for the discussion all. It just seem some sites show tons of noodles all over, others talk of needing seperate conduit for strobes, seperate for other lights, seperate for comms. Anyway i will just put in a few runs...to keep it simple. I dont think i need to go to alum pipe. Just my opinion...but if the fire is so bad that i need aluminum pipe ... i think too many other things have gone wrong and someone is telling me my numbers up and the wife gets to get enough insurance money to get a lear with pilot.
Thanks for the feedback, lots to learn.
 
Mike S said:
Toxic smoke is my bet.
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Could be, but if so, I would expect that there are also a lot of toxic materials in those electronic gizmos on the instrument panel that could cause toxic smoke too.
 
when PVC burns, it produces nasty gases. That's why automotive wiring, with PVC insulation, is not acceptable for aircraft use. So, if your wiring shouldn't be insulated with PVC, then neither should your wiring conduit. I suppose it doesn't matter as much in a wing, but in the cockpit you'll be flooded with toxic fumes if you get an electrical fire.
 
Just make sure that whatever conduit you buy from your local aviation department store is plenum rated. Not all meet this requirement, but most building codes require it, so it shouldn't be hard to find.

Yes, toxic smoke is one issue and how quickly it burns/melts is the other.
 
For what it's worth, the black drip irrigation hose that's about .70" OD isn't PVC. It's polyethylene. I wouldn't want to breath the smoke if that tubing was burning, but it's not as nasty as PVC. There's a thread here comparing weights of various conduit products. The .70" OD drip stuff weighs about the same per foot as the corrugated loom that Vans sells.
 
?

Would PVC be affected by avgas or its fumes?

I know long term sunlight or very much heat is not kind to it.
 
GAHco said:
Would PVC be affected by avgas or its fumes?

I know long term sunlight or very much heat is not kind to it.
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PVC, at least the irrigation stuff I'm familiar with, isn't fuel-friendly. Polyethylene is much more so. I have black poly drip hose lying on the ground in my back yard that's been watering my roses (you didn't know rose-growing and RV-building went together?) for 16 years here in Davis where summertime temps get to 100+. It's still pliant. UV doesn't touch it. Heat beyond 150 degrees or so is not a good thing.
 
If you properly protect your wire with the correct overcurrent device, you will never get any smoke because before your wire melts its insulation, the properly applied overcurrent device will have done its job.

100% of wire related fires from shorts are a result of improper overcurrent protection.
 
when PVC burns, it produces nasty gases. That's why automotive wiring, with PVC insulation, is not acceptable for aircraft use. So, if your wiring shouldn't be insulated with PVC, then neither should your wiring conduit. I suppose it doesn't matter as much in a wing, but in the cockpit you'll be flooded with toxic fumes if you get an electrical fire.
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Electrical fire????

I thought that is why we carefully designed our wiring architecture with either fuses or breakers. :)

Other than the fat battery cable in a tandem seat RV with an aft battery, there shouldn't be any unprotected wires aft of the, uh....firewall.
 
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