messydeer
Joined: 13 Feb 2006
Posts: 214
Location: Bellingham, WA
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 Posted: Fri Dec 14, 2007 10:17 am Post subject: Wing Wire Sizing and Installation |
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Hello 
I could use some help sizing the wires for my metal Sonex wing. I plan to install them before closing. I will have landing lights plus wingtip nav/strobe/pos lights. All but strobes are currently available in LED’s. If a xenon strobe is used, the power supplies would be mounted in the wingtips.
I spoke with a person at aveousa.net who said they will have an all LED nav/strobe/pos unit in production soon. No power supply needed! They also plan on getting out an LED landing light system. AeroLEDs.com already has a couple LED landing lights available called aerosun.
I’m not sure if I will want a taxi light (pros, cons?) in addition to the landing lights. If I don’t add the extra wires now and find I want the taxi light, I’d mount it on the cowl, I suppose.
Temperature correction
Using the formula L1/L2 = (234 + T2)/254 where T2 the temperature difference between 20C and the highest temp to be encountered. Using a max temp of 60C gives T2 = 40C. So L1/L2 = 1.08.
My round trip circuit length is 40 ft. To compensate for high temps, I need to increase the length by 8% when using the AC43.13 charts. That would give an adjusted length of 43 ft.
Nowhere have I accounted for the resistance increases of wire connections. Detachable wings and fuses may effect this.
Graphs
I was told my loads would be intermittent, so I used fig 11-3. To get the single wire amp rating, I used fig 11-4b. Altitude derating from fig 11-6 is .95 for 10,000 ft. For the bundle derating from fig 11-5, I used 100% loading for 8 wires, even though it would be much less.
Calcs
Here is what I got using all this info:
light type, amps, awg fig 11-3, amp rating fig 11-4b, altitude fig 11-6, bundle fig 11-5, max amp,
led landing light 2 20 17 0.95 0.5 8.075
55w landing light 4.5 16 28 0.95 0.5 13.3
led nav 0.5 22 14 0.95 0.5 6.65
led pos 0.5 22 14 0.95 0.5 6.65
xenon strobe 3.6 18 24 0.95 0.5 11.4
led strobe 2 18 24 0.95 0.5 11.4
max grd 9.1 10 65 0.95 0.5 30.875
Sorry, I don't know how to make it a nice table, but there should be 7 columns.
It looks like all of the max amp ratings are well above the actual loads.
Wires
I’ve been told 20 awg should be used instead of 22 for convenience in handling. There are also 2 more wires needed if I wanted wig wag function in the led landing lights, so 2 more 20 awg wires would be needed. So my bundle would consist of one 16 awg for the landing light, four 20 awg for the wig wag and nav/pos lights, one 18 awg for the strobe, and a 10 awg for grounding all of this. 7 wires total.
Bundling and Installation
Haven’t gotten very far into the actual process of how to bundle and support these wires. Aeroelectric.com has a pic of wires going through an opening secured by adel clamps to an L-bracket. I’m thinking of something similar, routing the wires through the leading edge lightening holes and using padded adel clamps. The ribs are 10” apart. I don’t know if any other stuff (lacing or ty wraps) would be needed.
I would leave the ends of the wires dangling out the wing tip. The nav/strobe/pos light would mount to the tip rib, which I won’t make for some time. The landing light would require the leading edge to be cutout and a bracket installed between the ribs. It would be easier to do this before riveting the wing shut, but cheaper to wait 3 years or so until assemble is almost complete. Wouldn’t want lights sitting around that long getting outdated and having their warranties expire.
Well, that’s about it for now. Any insight is appreciated.
Take care! 
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