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Old 12-05-2017, 04:21 PM
Brian Vickers Brian Vickers is offline
Join Date: Mar 2005
Location: Bainbridge Island, WA
Posts: 324
Default Lower firewall

I replaced the lower firewall and it's not that hard to do. If you drill out the rivets along the forward bottom of the fuselage side skin you can then roll it back and add the gusset shown in post #17. After you have removed the engine & mount, it all comes apart pretty fast. If the cowl cheek extensions remain on you will have a hard time riveting the firewall side flanges where they overlap. I think there are two rivets there. Maybe some other type of fastener (?). As I recall, the stainless steel lower firewall only cost about $26. The stock part fit very well and only required slight tweaking to fit with my existing upper f/w. Thin stainless is more forgiving then aluminum. Take everything out of the inside of the fuselage so you can put down some plywood and padding for lying down while working, bucking rivets, etc.

Sounds daunting but its not. In the process of reinstalling the engine I did a better job with all the accessory wires compared the first time around on the initial build a plus! Go for it.
Brian Vickers
Bainbridge Island, WA
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Old 12-05-2017, 05:13 PM
rv7charlie rv7charlie is offline
Join Date: May 2006
Location: Pocahontas MS
Posts: 3,351

Originally Posted by TIPSYNIPPER View Post
I have just noticed this wrinkle in my firewall, not exactly sure when it happened, but two possible occasions come to mind.
Has anyone replaced just the bottom 1/3 of the firewall? If I replace the whole firewall it will mean a respray, as the a/c is metallic painted, and blending it in won't be an option.
I am considering replacing the lower 1/3, and making the joint on the firewall.
Any tips/tricks/suggestions very gratefully received.
Are you doing it for cosmetic reasons? If so, that's your call. But the firewall is non-structural, according to Van's staff. If you can seal the cracks with something like
there should be no functional or safety issues.

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Old 12-06-2017, 05:13 AM
Join Date: Jan 2014
Location: Ardleigh, Essex, UK
Posts: 54

Yes, having spoken with Vans builder help desk they did confirm that is considered non-structural.....but if it is being bent it must be a load path.
I am more convinced having studied photos just now that a brace bar across the top must help stop the flexing of the firewall.
It would be for cosmetic reasons I suppose, but also a/c value when I come to sell it.

Last edited by TIPSYNIPPER : 12-06-2017 at 05:18 AM.
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Old 12-06-2017, 05:31 AM
Join Date: Jan 2014
Location: Ardleigh, Essex, UK
Posts: 54

When Steve built the a/c he did not anticipate engine removal with regard to the wiring loom to the engine. Thermocouples I can't cut, but putting a plug in-line would ease this and future engine removals. Can anyone suggest a good plug/socket system for the loom?
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Old 12-06-2017, 06:38 AM
Larry DeCamp's Avatar
Larry DeCamp Larry DeCamp is offline
Join Date: Apr 2010
Location: Clinton, Indiana
Posts: 715
Default RV8 gusset ?

Thanks to all for this heads up, my RV4 side skins are fitted but NOT riveted. So perfect timing to add the gusset in the pic. My vertical aluminum angle has two rivets in the WELDED steel corner fitting. There is no gap to flex the firewall under loads ? That said, does anyone have specs on the RV8 gusset and I will fab and install.
Larry DeCamp
RV-3B flying w/ carb & Pmags
RV-4 fastback w/ Superior EXP 0360 /AFP & CPI
Clinton, IN
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Old 12-06-2017, 12:16 PM
Sylvester Sylvester is offline
Join Date: Mar 2017
Location: Uk
Posts: 9
Default Firewall wrinkle

Hi Larry. I can't post pics, but pm me and I can email the 7 drawings.
The more I've crawled around mine, it's apparent that the flex is in the vertical 3/4" angles, since the undercarriage loads go up them to the top mount. The side skin doesn't take the load because it's not structurally supported between the two mounts; it's only held there by the 'non structural' firewall. The gusset stiffens it all up. I've seen pics with a gusset top and bottom. The 7 drawing shows top and bottom.
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Old 12-24-2017, 05:45 AM
Join Date: Jan 2014
Location: Ardleigh, Essex, UK
Posts: 54

Having trawled the web to find what I can this seems to be one of the best threads currently.
I am considering replacing the damaged section of the firewall, and adding the lower 1/4 gussets, BUT, not riveting them to the skin at the angled side skin longeron, but making a deeper gusset that goes all the way to the bottom stringer and bolting it on.
Cherrymax rivets to fasten it to the vertical....I think there may be room enough between the vertical and the skin to get the CM rivets in before setting them.
This way I will get the same reinforcement, but without disturbing the rivets on the fuselage skin.
Thoughts and comments welcome.
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Old 01-22-2018, 04:40 AM
Join Date: Jan 2014
Location: Ardleigh, Essex, UK
Posts: 54

Design and installation almost complete:
0.040 4130 gusset installed from the lower stringer to the vertical angle. Bolted to the lower stringer and solid rivets to the vertical alloy angle on the firewall. No need to disturb any rivets on the skins.
The match drilling of the gusset was achieved by drilling access holes in the fairings (non structural) and using a guide to drill pilot holes so the original holes were not enlarged. The access holes are covered by the u/c leg root fairings so do not require addressing.


Last edited by TIPSYNIPPER : 01-22-2018 at 04:42 AM.
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Old 01-22-2018, 06:22 AM
RogerG RogerG is offline
Join Date: Dec 2011
Location: Lubbock, TX
Posts: 61

Below is the RV-4 Firewall weldments:

Roger Graham
Lubbock TX
RV-4 Under Construction
VAF Dues Paid 2018
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Old 01-29-2018, 08:04 AM
Join Date: Jan 2014
Location: Ardleigh, Essex, UK
Posts: 54

Hi Guys,

An update on the firewall repair:

I have been in touch with Vans who have been very helpful.

The final repair has included gussets that fit to the lower stringers and to the upper firewall supports made from 0.040" 4130. To facilitate the repair I needed to match drill the gussets at the stringer attachment bolts, and as the fairings on the lower sides of the fuselage are not structural I drilled those to allow me to drill through the original holes using a guide for pilot drilling to ensure I did not open out the original holes. This has meant that I do not need to drill any rivets on the fuselage skins other than those hidden by the u/c fairing.

The replacement firewall section was relatively easy to fabricate.

If you follow the link below it will take you to other photos of the repair scheme.

Last edited by TIPSYNIPPER : 01-29-2018 at 12:51 PM.
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