What's new
Van's Air Force

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

Fastening Firewall Items using Fiberfrax, Foil Etc

romaja

Well Known Member
I plan on insulating my firewall using Fiberfrax, Foil, Tape, fire barrier that was spelled out in past threads ala Dan Horton. RV-14A. Trying to wrap my head around the items that use rivets instead or screws or bolts like the battery box, vent assemblies, cable brackets etc. This will require much longer rivets than specified due to the increased thickness of the new material between the item and firewall. For those that have accomplished this, were you able to find rivets long enough? Did you switch to screws and nut plates? Any pics you have would also be helpful. I dont want to focus on why insulate but how this was delt with.
I have attached a drawing to illustrate this.

Regards,
Jim
 

Attachments

  • IMG_2883.jpg
    IMG_2883.jpg
    381 KB · Views: 295
What I did:
- No FiberFrax sandwich under the engine mount to firewall connection.
- Anything that got mounted on the firewall with rivets was done before the Fiberfrax/SS sandwich.
- Anything that got mounted to the firewall with bolts was done before the Fiberfrax. After the FiberFrax was installed these mounting holes were back drilled from the cabin side, and the components mounted. This provided many of the Fiberfrax to firewall fastening.
- Per Dan's instructions, SS pop rivets where used where needed for the balance of the Fiberfrax fastening.

I'm thinking that rivets holding something to the firewall through the FiberFrax sandwich may not be mechanically up to the task. Here I'd be concerned that whatever was attached could move around enough to wear away the FiverFrax leaving the rivet loose.

Carl
 
easy

You simply rivet these items to the firewall as directed by the Vans instructions and cut the insulation around them. Other items that are screwed to the firewall can go on top of the insulation
IMG-0883.jpg
 
I'm thinking that rivets holding something to the firewall through the FiberFrax sandwich may not be mechanically up to the task. Here I'd be concerned that whatever was attached could move around enough to wear away the FiverFrax leaving the rivet loose.

I’m curious as to why this isn’t true for the bolts also?

I know you could technically check the torque of these every year but is that really going to happen? 🤣
 
I’m curious as to why this isn’t true for the bolts also?

I know you could technically check the torque of these every year but is that really going to happen? 🤣

You remove the insulation before bolting the heavy items to the firewall. But for things like cable clamps or voltage regulators (items which have low mass and/or mechanical stresses), you'll be fine bolting/screwing through the insulation.
 
On the belly of my RV-3B, I used 1/16" Fiberfrax under a .020 Titanium panel. I needed to rivet through the Titanium for the center stiffeners. I glued on .063 shims in those locations and cut the Fiberfrax around them. Then I simply riveted through the stack: Titanium, .063 shim, .040 belly panel.

This shows the shims before I added the Fiberfrax or the Titanium.

RH_Fwd_Side_2_Fwd_Belly_S.jpg


I might do this for the firewall, too.

Dave
 
Thanks everyone for the informative posts and pictures. I think I will hang the riveted items as the plans spell them out and cut the fiberfrax around them. The screws or bolts items, I will do after the firewall barrier is hung.
 
Firewall Insulation

Did mind similar to what been described in this thread. Frax & Titanium foil trimmed around engine mount so mount sits directly on the firewall. Lighter components were used to clamp the Frax & Foil in place. Where additional attachment was needed I used stainless pop rivets combined with stainless countersunk washers. I have a 2’ x 10’ roll of Frax left over that I will sell for a reasonable price. A 2’ x 5’ piece is plenty for one firewall.

Don Broussard
RV9 Rebuild in Progress
57 Pacer
 
Last edited:
Just a couple of additional comments.

First, make a pattern for your cutting. I used some old roofing paper because it was around, but you could use poster board. Fit the pattern onto the firewall and make the cutouts in that first. Then transfer the pattern to the foil. I used TI foil and it has a tendency to try and roll up. The foil doesn't need to fit perfectly around then edges since you are going to put hi temp caulking around there, it just needs to be close. I'd say within an 1/8" is probably good enough.

The second thing I did was buy 1/8" long SS spacers from McMaster. This approach is similar to what David did with his approach. I glued them in place then put the fasteners and sealed SS rivets through them. I didn't like the look of the puckered foil and this approach prevents most of it.
 

Attachments

  • firewall_foil_1.jpg
    firewall_foil_1.jpg
    353.9 KB · Views: 295
  • firewall_insulation_3.jpg
    firewall_insulation_3.jpg
    331.6 KB · Views: 276
Jim,

You're timing is good, I just finished mine last night about 9:00 CST.

For me this was a very difficult task. Although there's a lot of good information on this site, everybody does the job a little differently. Different materials, thicknesses, acceptable levels of craftsmanship, weight considerations, and models make gleaning the right information tough. In addition, the firewalls are different on different models. For example, in the case of the RV-14 and RV-14A, the motor mount is different which forces a change in the thickness of the fire protection material (I used Fiberfrax).

The most difficult part of the task was cutting the stainless steel neatly. Scissors easily cut the perimeter, but cutouts for other items was extremely difficult.

Please check your PMs for additional info.

Fred
 
Remember, an overlap seam down the center, covered with a strip of aluminum tape, has a purpose. It's a pressure release. The aluminum tape melts in the event of fire, allowing gasses from the organic binder in the fiberfrax to vent into the engine compartment, rather than potentially squeezing through firewall penetrations.
 
Back
Top