Thorp Air Command - T18.net

I have wired my plane using the Bob Knuckolls Z-11 diagram (diagram is attached). I am planning to put my battery behind the baggage compartment to make my W&B work out. With that in mind, I have a couple of questions that I need help with:

1) The wire running between the master relay and the starter relay is 4awg. Do you guys think that is big enough?
2) The wire connecting the master relay and the main buss is 6awg. Do you guys think that is big enough?
3) I have an internally regulated alternator, so do I run the 20awg wire off the "F" lead on the alternator straight to the 5A alt field breaker?

Ryan : Attached are 2 wiring diagrams I used . The main one was from Composite Design . I used their Power Panel in my AC. The two things I did different from the 2 diagrams is that I bussed together the 2 relays using copper buss bar and connected them to the POS term of the battery . The other was I used #4 wire from the starter relay to the starter...I only had about a 3 1/2 ft run to the starter. If you have the battery in the baggage compartment I believe the the recommended wire is #2 . I used shielded wire to the max extent possible .[attachment=0]

RB Captain Electron

thanks Rich. Trying to figure out the electrical section of 43.13 is beating me up. I cant figure out whether to use a chart, a table or a formula....or all three together.

The Tony Benglis (sp) books will also help .

RB

If you intend to use parts of 43.13 I suggest a Law Degree to understand them !

RB

Hopefully, all of the aluminum wire that flooded the market years ago is gone. As Piper found out, it is a huge fire hazard. While many use arc welding wire, I would suggest good aviation wire from an approved aviation source for this one time expense. And yes, the lead from the aft mounted battery to the master contactor and on to the buss needs to be #2. Your starter will appreciate it.

_________________
Bob Highley
N711SH
SN 835
KLAL

I had both my solenoids mounted on the firewall. However, my battery is in the baggage compartment and therefore always had a live wire running from baggage compartment to firewall. Well this weekend I moved the master solenoid next to the battery in the baggage compartment. Also, made an interested discovery; I have an ammeter and this what someone put in line as a shunt for the meter (see pic). I've decided to replace the ammeter with a volt meter; that's a power packed subject in its self. BTW, I've been referring to Bob Nuckolls book on aircraft wiring; it's very informative.

_________________
Chuck Kincer
Richmond, Me
575CK
KIWI

I`m redoing my wiring too. Originally I thought I could get by with just straightening out the rats nest, but when I found that the 35A alternator was protected by a 50A breaker, I decided to go clean slate.

Bob Nuckolls book is a great resource, but he goes into excruciating detail and analysis. Nevertheless, there are many gems of information in the book. This was the only place that I found that actually stated that one should not put any more than three circuits on a single breaker. I also like the idea of protecting the system with a fusible link outside of the firewall (for those of us with batteries up front.) One thing about his generic wiring diagrams... he specifically states that the wire sizes and CB values are dependent on YOUR devices. You shouldn`t just blindly use his numbers without checking what you have. Also, be sure to do a load analysis to satisfy yourself that your system will handle all missions. It took me a while to understand how to do this... just search the weeb for an example.

Good luck, Ryan.

d

I would suggest using Tefzel aviation grade wire . It withstands the heat much better firewall foward . Stein Air has descent prices on the wire . Spruce also . Spend a wee bit more on the stuff foward of your feet !

RB

+1 with Stein Air. I just bought supplies, and talked to the man himself. He is interested in you and your project, so he may just ask you about it! I got help and didn't even know to ask.
On an other weight / electric issue; I'm thinking about upgrading to a Skytec Flyweight starter, eliminating the starter relay and moving the 27 pound battery + fiberglass box out from behind the baggage. I would like an Odyssey PC680 on the firewall or under the copilot seat. I'm hoping to drop 20 pounds and get better starts. Less starter wire, lighter battery, lighter battery support, lighter starter w/ built in relay.
I'm trying to work up the nerve to remove the vacuum system and the fuel pumps too
EAA326, our local chapter, has scales, so this would be a good time to "Weight & Balance" the plane.

_________________
Scott Emery
EAA Chapter 326
T-18 N18TE

I was just reading where Bob Knuckolls suggested using welding cable for the big wires running firewall forward. I even priced them, but I couldnt bring myself to do it.

Im also a Stein fan. He's always been very helpful when I call as well.

I have a PC 680 behind the copilot seat in a batt box, bolted to the box is both solonoids. I ran 1ot welding cable forward for the starter and direct ground to the Lyc, 2cables 1ot. the cables are heavy I will admit,they are flexible as a piece of rope due to the fine strand inside the insulation on the cable. I have worked around welding cable for years,dropped heavy objects on it,ran overit with heavy loaded forklifts, blown hot slag on it from cutting torches and plasma cutters and ran the AMPS on the hot box so high the cable was all but too hot to touch, and then continued to use them and they out last the welder itself. The Cables are a viable way to unload your battery into the starter when you trip the solinoid, of coarse this is just my opinion derived from 35 years experience with the bulky old welding cables, the cables I used on my plane are probably at least 20 years old and they are still tougher than boot leather........Da

Dan : You probably used that welding cable to hook up your electric blanket ! There are a few chairs in D.C. I would like to hook that cable up to !

RB

Yep, I will help you on that mission Rich got bout 12 ft of it left on the shelf and a couple of heafty cable end clamps.......Dan

12 FEET ! That's pretty close to ground zero when you throw the switch ! BOOM ! Mighty close to the Political Cliff on this topic ? Probably should return to Thorp Topics before the Administrator tops me nogin !

RB