Firewall reinforcement

I plan on sandwiching my fiberglass tub firewall, with sheet metal. Both to support the brake booster/dual master and swinging pedals.

The question is, would 16ga be too stout or should I get 18ga? The brake setup can't be that much heavier than the heater that was there to start with without support but, I'd like your input to the matter. Thanks

 

Thanks Glenn! I guess that's why the preview post button is there? I realized what I said right after I posted haha

14ga might be a little more than I can work with in my little ol garage.

 

I guess that would depend on how beefy that fiberglass firewall is ? Lots of weight out front beyond the firewall with a Booster and a dual Master cylinder hanging out there and the same goes for the pedal set inside where you'll have opposing application forces.......average brake pedal applied force at the base of the pedal even for power is about 50 lbs of foot pressure...........as Glenn mentioned thicker is better as well as wider and covering more area of the firewall........I think even 16 gu will flex , but again that depends on how tough that firewall is.........most folks on metal bodies use at least a piece of metal at .125 thick to cover that job......the other option is to brace the inside from the pedal bracket up to the dash or cowl area.

 

My intent was to do both sides of the tub from just about the center of the tub over. That's from the top of the dash to the floor both sides. I'd weld the plates together to make the form but I'll have to bolt it together.

If I can use a brake at work the 14ga might be an option.

 

How thick is the Fiberglass firewall ? and how is it reinforced to where it attaches to the body? Fiberglass can be very strong but the biggest problem with glass and sheet metal over time is the weight of the Items attached will tend to wallow out or elongate the holes.......even if clamped tightly. That's why the structure should be the steel and the weight of that spread out over a larger area on the glass.........now if the glass is 1/2" thick with a piece of plywood in the middle that would help.

 

It's +/- 1/4" thick along the firewall. Thicker as it gets towards the sides where the fenders attach and about 1/2" at the top of the firewall where that lip is.

The entire tub front to back is fiberglass. It was a replacement tub that was installed in the early 70's.

Hopefully this image uploads, if not I'll direct link it to photobucket.

 

I wish I could afford a steel tub and just drop that in but, wish in one hand my grandmother always told me.

What if I did something like a piece of bar stock welded from the frame up the side of the firewall, and then around the bottom of that lip? Almost framing out what I'm going to cover in steel...and weld that together. Then the plate on the inside of the cab can be bolted into the bar to help solidify the two sides..

 

Aluminum sheet in 3/16" or 1/8" thicknesses isn't prohibitively expensive either, if you're concerned about weight/rust.

 

That tub is very thin and will flex , where you need the most strength. This is what I normally do with a Steel Tub................you can use the same method but only modified to accommodate the Glass Tub........just think more is better...........wider on the plate to get closer to where the body meets the firewall and then make a nice brace under the firewall cowl area to catch the end of the petal set.
Do it right once!

 

Thanks for the input and the pictures.

As much plate as I can work with, and as large as I can get it to distribute the weight.

 

If your going to do a Brace inside from the Pedal set to the cowl or dash area as I showed that will probably be fine..........although I would extend that plate up to include the radius above near the cowl where the strength is in that corner...........do a similar plate inside as backing and space 1/4" bolts or equivalent every 3 inches +/- around the perimeter.......or if you have a HD Rivet Huck Gun that would also work.........Once you gather up the Pedal set , master and booster you will come to appreciate how much weight that stuff is and be glad you took the extra time to reinforce everything........take your time and you should be fine.