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-   -   Firewall Passthrough (https://vansairforce.net/community/showthread.php?t=140476)

AviatorJ 08-06-2016 07:49 PM

Quote:

Originally Posted by Lynnb (Post 1100188)
I like those SPHERICAL FIREWALL FITTINGs, what size did you order for the three control cables?

Would also like to know this. I plan on working on my firewall a bit next and will be installing 3 eyelets.

steve murray 08-07-2016 05:29 AM

Quote:

Originally Posted by flion (Post 1100053)
However, I am using sealed CPCs for my passthrough

Sorry, can you educate me on what a sealed "CPC" is? I am probably 1 year + from working on firewall but trying to learn.

Thx

Steve

flion 08-07-2016 08:37 AM

Quote:

Originally Posted by steve murray (Post 1101194)
Sorry, can you educate me on what a sealed "CPC" is? I am probably 1 year + from working on firewall but trying to learn.

Thx

Steve

Try here: http://www.omega.com/pptst/MTC_CONN.html. Actually, CPC is a bit of a misnomer because they are not plastic; they have aluminum bodies and a bundle shell (about 3" long) that serve to protect the connection from flame and heat. The pins themselves are bedded in a flexible synthetic material that is supposed to be fluid-resistant.

Understand that they are not flame-proof. But they are way better than Circular Plastic Connectors and probably as good as many of the other pass-throughs in common use, where the weak link is burn through of the wire insulation being passed. The idea of such devices (shields and such) is to minimize the exposure and grant a little extra time (seconds?) to deal with a fire incident.

So why not just use one of the simpler and much less expensive solutions available? When I had my landing incident in my RV-6A, I had to replace the fire-wall and a couple of the stringers behind it. This meant that I had to undo connections to thermocouples and sensors, etc. and thread them all back through the firewall. The worst were the connectors for the Lightspeed ignitions, 25-pin soldered connectors on the cold side to the crank sensor circuit board (potted connections) on the hot side. It took some large penetrations and creative shielding but I managed it. I also decided that the automotive approach of a connector at pass through was the way to go. In the -10, if I need to remove the engine, I won't have to decouple each individual CHT, EGT, etc. Instead, I will just have to undo the starter cable, grounding strap, and two bundle connectors (not mentioning fuel and oil lines). If (gods forbid) I have an incident similar to the one I had before, replacing the firewall won't involve a lot of wiring work. And I carried the idea through the plane. Replace a rudder? Just wire the rear strobe and trim servo to a CPC in the bottom fairing and attach to the connector already routed from the fuselage.

The downside of connectors is connector reliability and maintenance (plus initial expense). But you can select good quality connectors with some research and maintenance is not difficult during inspection. Consider the reliability of the connectors already in use in lighting systems, for example. But, as with everything else in experimental aviation, it is individual choice and preference.

jwilbur 08-08-2016 04:14 PM

Quote:

Originally Posted by Lynnb (Post 1100188)
I like those SPHERICAL FIREWALL FITTINGs, what size did you order for the three control cables?

Sorry for the late reply to this question. I got the 0.260 size. They are installed on my firewall right now, but I haven't run the control cables yet. I determined the size by measuring the control cables I have - standard cables from Van's in the FWF kit. I did do a test fit before installing the fittings and they looked good.

Lynnb 08-10-2016 01:22 PM

FYI: After drilling this and working on this new hole for the P27 battery cable in the firewall I'd recommend doing something different than the wiring plans. If you do drill the hole, cut the end off the cable and crimp a new end. With the crimp size on the cable, it will not fit a 1/2 hole. I had to upsize to 5/8 and now I'm looking for a bushing. Had I give more thought I'd have just cut the end off the cable. My .02.

Lynn
Quote:

Originally Posted by Lynnb (Post 1100154)
fyi: If you look at the Van's wiring harness plans, they actually drill a different hole next to the skin to run the battery cable through.


Evolution10 08-10-2016 02:07 PM

If your looking for some of the best and safest, look at:

http://www.doubleteeproducts.com

They made the exact sizes I needed for all my pass-through needs.

Highly recommended!

AviatorJ 08-10-2016 02:49 PM

Putting together a BOM for my Firewall and Tunnel.

Fore the firewall the jist is I'm going to use Stainless Steel passthroughs and grommets, with sandwiched Fiberfrax and 0.002" stainless foil. I'll then use 3M Fire Barrier 2000 as both an adhesive for the Fiberfrax to the Firewall and the Foil to the Fiberfrax as well as any gaps.

I'll do something similar to the tunnel as well, but will be Fiberfrax, insulation and then the foil...

Anyone see any issues with this?

Also where can I source 0.002" stainless foil?

rocketman1988 08-10-2016 03:05 PM

Foil
 
McMaster Carr has it...

clutch22 08-10-2016 03:15 PM

Quote:

Putting together a BOM for my Firewall and Tunnel.
While you're at it, you may want to purchase one or two of those Airward tunnel access covers.

AviatorJ 08-10-2016 03:35 PM

Quote:

Originally Posted by rocketman1988 (Post 1102343)
McMaster Carr has it...

Thanks!

Quote:

Originally Posted by clutch22 (Post 1102350)
While you're at it, you may want to purchase one or two of those Airward tunnel access covers.

Done, installed one on the passenger side a few months ago.


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