What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Firewall Passthrough

ethand

Well Known Member
Where did you put your firewall pass through for wires, sensors wires etc and how big?

I plan on going with the SS kits from Spruce. After a search on line I found a few examples but looking to see where others put them and what size.

Thanks in advance

E
 
Timely Question

You're question is very timely, I was about to ask the same thing. I did buy two of the 1" SS pass threws, I was wondering if you just enlarge the two holes in the image below to be 1" or are these earmarked for something else, I looked through the plans and can't really see that these are for anything else:

byvXDWi5IDrnKGjw9MueK4quN4BLnjO14YKETnAHkmay-3D-pXi8s965_zbWyTnUdgNKDOVMTKAUx4-Fs_lH2hXN5-j1TAv3HKDsVVO_AuD1M5U0QtoIm_jf4jSOErOi7GvKNyCqJRfbYXg3RG2VLfknMi1A5xNfS-u51cIrUGsF8OSvVibaMVN6hMHVwFrR1gMtA_iKplVQ5KPLtJJK8LVIXcJuhLsq8mB2jKYzVmD3hlVf29GFgwZloLn5Gq4_aOSzPqzdaaWtVgQORRW45_HhqXZfCr1P991qkZu8u1zxAMQlF3k6xo-7bUQR3ZFPuWnxGIhiSaEkUmUO5dijOP82tgBcntkVz5zZDPGRrscasZzH1koGEjA3_X6vlJGt4kHgXG3ihuyyFCRiyTo2IjByTcZ3G2J_HabymB4OmAQZQZDPeUmfrX8Vm9wBUOjIJKS2ST2pGGn1txQVybOaDcuxdHkcdZA3RBBnNZM9ZKtMPIJZtBcJYlh7huNNM4RJXFGtF8kAPk_yXGmf4mDYduvr8v7uXet4Fv3-Q8uX0N0dor83PGpwz1Y3Ocq-0eqw8YgyFfPasAV54ezYfl2tKQAWu-QyvXGG=w515-h439-no
 
Last edited:
I can't see your image but if that is the roughly thumb-sized holes left and right on the firewall, that is indeed what they are intended for. However, I am using sealed CPCs for my passthrough and the extended sleeve (about 3 inches) would have interfered with the motor mount, so I covered the existing holes with riveted stainless steel covers and relocated my openings. My point is that you can relocate things as needed and appropriate for your installations.
 
Thanks, can other's not see my image? I have been having a hard time moving from picassa to goggle photos.
 
Not many people have chimed in. I'm also interested in what people have done. I've been stalling drilling mine, but I'm about finished with the avionics and will be riveting my panel substructure in soon and would rather install the passthrough prior.

I'm thinking I will use the existing LH hole for my battery cable, install a 1" firesleeve passthrough near the center, and use the RH passthrough hole only if I were to run out of room in the 1" hole. :confused:
 
Remember that the alternator wire carries a pretty large current and does have some ac ripple on it. In principle good avionics boxes will filter out any pickup, but I chose to use separate firewall holes for the alternator output, and for low level signals (EGT probes, etc). ymmv
 
Not many people have chimed in. I'm also interested in what people have done. I've been stalling drilling mine, but I'm about finished with the avionics and will be riveting my panel substructure in soon and would rather install the passthrough prior.

I'm thinking I will use the existing LH hole for my battery cable, install a 1" firesleeve passthrough near the center, and use the RH passthrough hole only if I were to run out of room in the 1" hole. :confused:

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.
 
4 on a 7

This is on an RV-7 - but for what its worth I used 4 for electrical. Top "corners" carry EGT/CHT and other engine sensor wires; one near the center top carries Electronic Ignition leads/ mag P-lead; large angled one on the right side carries all power wires.

I also used 3 additional passthroughs like these for the throttle, mixture and prop cables.

yNC-30WBjR9ftckJfQlB7cIO5njfb-es_q6essiTHRWAoNcbB-lygva7EgW7a656D7myQGCM3oG2SI2tQByoJTV-1EeDVQAaflmK7UB8MCGc-sUZtTnSUCeTUBCEYupplJwk3FuC1Gcjb2BaAwpCFThxkoPC1GEEsNGnFBy4NLvCA_RB4La5A72HdV8jsxAv3_tNo2pjV0fajxyIsWKw-n-I6FaMb1b8iOCduqsjCA8hDlUkC7lUcsbpFkxNOPKwzhDeMAH5d_PBDxI25ZE5FrbJ3kGApkwNTZlWunHJ7xCysaY09ZmKOWBbgm5YS78dQ7BntRYdqRC46hsD6_FK2AfY_g5ocZ2EYb75s0AapCvIpJFD85dJC66bX-rizvJu7viCOKsrV2h-XEh9xF2AVHt4VvmZYTxu26Oav19Rgtn7tyCahlEcgeMaifhzE4fRsy33T9VlYGfO5vpFjbNcltRViQi8kzW2FlFuMx5DiDV9zahDQQmkx4dVC4LLWmhpqoUiN3k-zwB2jkUb8KmHl_TIcKswf9oWXWmYoyOmTbXzku2FroRXDUB6Zz4WVVes28ZdGGRWxujpr06bSMVZVuSNIbAr59A=w1024-h647-no


K4DQ65_QA0wkjWIyr0E3CWlwpSeUIafsejn-gAkzjNMZqeRI5ATQbdIb3VkIsZgNOUkD_2uSlMbyO1YGckWu5j8CNG5OY7vj_XtbhnO4_Rb5d1Si4lZumfekuMB9uFQGo0-2OQJPpzlFa_7Prdzpmtzv0y-Lqmm7shvIKCzK3i1-olqtiNGJ5w_uysCB4VPG3AMMl9XnFpVYRa5jpi6TXrW2P70ak77WiAcT1i_IVO8LHahWlfV8VGgAmaNiiDWVpOlCVVn91uR-06feoZwORTfKWW4vcw9sxAflk72UED8PGwmLYc5hJC4n-D5IAdnYgB66_jYBg3ebp_CLvXVB1n5dTve2nRrC7hZAQ6RdP-dnP2GXkNPdNLqCt4BN3qUP_RdljbJTMHf6lQZX0I-vG_0SiGm7w8ADatWKV1zuj6XOeWLYQTYMvCvnNbPleyLgMG3nkxcSWCVhOliAgTujuZn-wDUqonu77STinIjnC8ftikf-4ExLjWoksHeHa-07A2i6IBXsgdBzkjNPelLhLkGpi_HvWZE_tgyks_cr-68UKx4NSjo1lYMtrVrDjCKCLan8h6_H-f7T6EzEfwN3OMDkRuWzWaU=w1024-h795-no
 
Last edited:
I can't see your image but if that is the roughly thumb-sized holes left and right on the firewall, that is indeed what they are intended for. However, I am using sealed CPCs for my passthrough and the extended sleeve (about 3 inches) would have interfered with the motor mount, so I covered the existing holes with riveted stainless steel covers and relocated my openings. My point is that you can relocate things as needed and appropriate for your installations.

I like the idea if CPCs but can you use them with the thermocouple wire for EGT and CHT?
 
I'm using the SS fire-sleeve pass throughs from ACS you've mentioned. I ended up with one of each size. The interior firesleeve eats up a lot of space. The #2 battery I bring through the existing hole which I enlarged for a bulkhead fitting. The smallest SS pass-through I've got on the top-left of the firewall and will be using for ignition related wires. The 3/4" pass-through I've got in the little slot designed for the heat boxes and alternate air door. The 1" pass-through I've got on the upper right for all the thermo-couple wires and various other engine monitor wires. Van's has you drill another hole for a bulkhead fitting if you position the manifold pressure sensor on the inside. The existing hole on the far right I probably could have used for the 1" SS pass-through but didn't, thinking I would use it for something else. I'm going to plug that one.

Also, if you happened to drill the holes in the stainless recess according to the plans (as I did), you'll find that most of the nice pass-throughs for prop/mixture/throttle cables won't fit because the holes are too close together. I found these on ACS which do fit. I installed them just the other day.

https://www.aircraftspruce.com/catalog/appages/6000metalgrommets.php
 
Last edited:
I like those SPHERICAL FIREWALL FITTINGs, what size did you order for the three control cables?

I'm using the SS fire-sleeve pass throughs from ACS you've mentioned. I ended up with one of each size. The interior firesleeve eats up a lot of space. The #2 battery I bring through the existing hole which I enlarged for a bulkhead fitting. The smallest SS pass-through I've got on the top-left of the firewall and will be using for ignition related wires. The 3/4" pass-through I've got in the little slot designed for the heat boxes and alternate air door. The 1" pass-through I've got on the upper left for all the thermo-couple wires and various other engine monitor wires. Van's has you drill another hole for a bulkhead fitting if you position the manifold pressure sensor on the inside. The existing hole on the far right I probably could have used for the 1" SS pass-through but didn't, thinking I would use it for something else. I'm going to plug that one.

Also, if you happened to drill the holes in the stainless recess according to the plans (as I did), you'll find that most of the nice pass-throughs for prop/mixture/throttle cables won't fit because the holes are too close together. I found these on ACS which do fit. I installed them just the other day.

https://www.aircraftspruce.com/catalog/appages/6000metalgrommets.php
 
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.

I noticed that, but is there a reason not to use this hole for the cable if I plan to add one or two separate passthru's elsewhere for the other wires?
 
This is on an RV-7 - but for what its worth I used 4 for electrical. Top "corners" carry EGT/CHT and other engine sensor wires; one near the center top carries Electronic Ignition leads/ mag P-lead; large angled one on the right side carries all power wires.

I also used 3 additional passthroughs like these for the throttle, mixture and prop cables.

0fD10V2DG-gUTYsaPBNKFy1_PyxF3WT-Nq6HBo7aRefKL0CtuHtAJd3hdf3gczNRlaTZdCRAO3r3KhKyxYZJVzFBlkFmvKWwiSpUi0N6Xq0pHo5Gg6a8TZS04sNWKAxJfwRQP3ZZSFR8CUO-36dXrHwwpNnplmS2le8_SuDvbT-O_lgi5lZz1N2PzwsDeeDsaWQDH4J0VpOarmC0k689NWapL8uzYD6ZQaDwjfM4XLeBYhm7j_1ySJWVei9KDuJoXlfl988liL03V5dekgN0vAi7lv6LS-7ldAy_iLqL1QPfPw3Alfr6Y9OeIPnwZytdqRI_rAuw8EmeEnrfG-fW0HQoQwy_F6-xtrC_scQCiA9vCrsT382hQ7bev-8fr4rBZ8a1rftUgFi1gm87xZJhnZ__Yc1efjxOaQfuwlm47PpxzH2LjSjBpi5s-M0zxqC6qD1ZUKAV_8PMvahu20k8X_Nr4XA87rGMzvGHcAXvJ2W-BktSDIVKps7K4ReexpNtanBskjip7HN2uYl1DSaSxWdExFGw802P0bwbVsPYxW5mVpY-p3-G5cExnpJmIts3njDLWt4mZPZXlu6b4JwXO8dl3M3oiBw=w1024-h647-no


_Qk07KObRwrn8SwaZJnuHvHNpYmd7bpzQMJt_nNb_Jd5NKsRZ9DhEil2QIgny5XRiWlkDi5z1rZOKdzJnF1aC5LSq3gwgnL_F3ZuTm9PtSSL1SG9xSTN35k2vGjHeax6ELD7qS4Xt1yyytEZ7by_Sjf6nLGi2FhcuchWSq5hg_72UAI9HE4AAF7rOw2PcF8KVYV-Uo41EiedGQsWsGeAdZouITQv0cNxSH8ia8LpEySDuitzPon4MtWdTPoFTrL4XLxT4_ehCfhZmLxJzBgtSB3HMo4VfJq9I40ZdIdfFZRrxAYkiXWtaen7t-s9NU0HcBQZsMSuI9EyR9t81r_yEwXIfpQQDJbYjwVp-Zd08TcZH2SUAHJAXbb3IEhW7ykdGz5uHoOR0OTBhImNPjb-fG0pRyB_S_f4DfFlRBPPQN5T7aGqBqqSRWDcosS6a4pp7Nujzp7HySUcY0bwltYVuYWVf8v_5Uj1Q7dcbxIlqc83cfq2y4j29Q_0stS6iupR1y2rI0kt2iT5Ic5YphcOwJl6YXsNfXXBKlEyjy1fTVsWRhzJegDgTBXWAykKB525OHYghhO4pc1LwtRgB0InWHhaM52KgwI=w1024-h795-no

Your photos are not coming thru. Just shows a dash.
 
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.
 
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.
 
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
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.
 
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?
 
Side question... Is it a bad idea to use the self adhesive foil? I don't want the glue/adhesive catching fire.

Update - The self adhesive doesn't come in 24 inch wide so never mind.
 
Last edited:
About to start on the Firewall and Tunnel with the materials I received today. Before I start punching holes in the firewall I wanted to check if I'm leaving anything off.

Firewall.jpg
 
About to start on the Firewall and Tunnel with the materials I received today. Before I start punching holes in the firewall I wanted to check if I'm leaving anything off.

Unless you're going to use the little slit for the alt-air and heat-box cables you might want another pass-through. I enlarged the little slit and put a 3/4" SS passthrough in that location for that purpose.
 
Unless you're going to use the little slit for the alt-air and heat-box cables you might want another pass-through. I enlarged the little slit and put a 3/4" SS passthrough in that location for that purpose.

Is that to the right of the manifold area?
 
Is that to the right of the manifold area?

yes. That little slit just below and to the right of the nutplate. I enlarged that and installed a 3/4 pass-through for the alt-air and heat-box control cables. Full disclosure. Although I have installed the pass-through, I have not yet installed the cables.
 
You probably want a separate pass-through for the battery cable. Keep power wires away from sensor wires. I didn't want to take a chance on the cable chafing and possibly arcing on the firewall, so I used a marine insulated firewall pass-through terminal.
 
.... so I used a marine insulated firewall pass-through terminal.

I did exactly the same thing, though I admit it is the weak point in my firewall. Every other pass-thru is stainless with fire-sleeve, etc. But this one is basically plastic. Don't remember exactly but I think it was rated to something like 350 degrees F. Not very much. I reasoned that the plans call for a snap-bushing so I'm at least better than that. Also, I positioned it as far outboard as I could and directly behind a mount tube so maybe some heat shielding from that. ... It's the one part of my firewall I'm not really happy with.
 
I assumed the battery/power line came through the 1" Pass through on the right. And the left one was for all other wires...
 
I assumed the battery/power line came through the 1" Pass through on the right. And the left one was for all other wires...

That will probably work for you, but you will have some other wires coming through on the right one in your picture. For example, mag wires and depending on how you wire things, a wire going back into the cabin to supply cabin-side power. But I think you'll be able to do it all through the 1" pass-thru you have planned.
 
Good deal, I actually made some solid progress on everything last night. Going to order another 3/4 inch pass-though for alt air/ and heater cables. Also need to order some Stainless Steel pull rivets to attach these passthroughs. Tried to use screws but the backside is really close to some brackets so pull rivets will work best.
 
Good deal, I actually made some solid progress on everything last night. Going to order another 3/4 inch pass-though for alt air/ and heater cables. Also need to order some Stainless Steel pull rivets to attach these passthroughs. Tried to use screws but the backside is really close to some brackets so pull rivets will work best.

Yep. I used CCP-32 rivets.
 
Yep. I used CCP-32 rivets.

Oh I ordered CCPQ-43 because I match drilled to 1/8th.

Two questions that I thought of, 1) can I put the engine mount on top of this sandwiched layer or should I cut out the spaces once I get to that point.
2) I used the 3M 2000+ as an adhesive, for the edges and seams how thick does it have to be, and is there an issue if it's too thick? I'm not the best chaulker in the business and it gets pretty messy....
 
Back
Top