818S - aluminum floor size question

[ben1272]

My aluminum floor's width matches the frame, but if I line up the rear edge just in front of the gas tank floor drain slots, the front edge is about 4-5 inches beyond the chassis square tube, and well into the steel floor area. The oil canning that my steel floor has is enough to either be tight with the aluminum or have as much as a 1/4" gap, depending on which direction it is oil canned.

Question is, can I trim my aluminum floor to be even with the front aquare tube, rather than overhanging into the steel floor area? I can still preserve the small 4" wide tab that runs forward from its leading edge.

My photo isn't great, but it shows how far past the center square tube the floor overhangs. I am thinking of cutting out red hatched area.....blue line shows new outline of floor. Anyone know why it is supplied this way? I don't want to cut it if its shape is important!


Thanks!


50098

50099

[DSR-3]

I'm at the same point in my build, and would like to know what the design-intent was from FFR.

[Mitch Wright]

I cut mine off but in hindsight I wish I would have installed the panel as is.

[TouchStone]

I thought it was to cover up the gaps where the steel panels (foot area and gas tank) are welded to the frame.

[billjr212]

I thought it was to cover up the gaps where the steel panels (foot area and gas tank) are welded to the frame.

Agreed. The intent by FFR is that you would cover the gaps both in the floor of the footwell and in the floor of the gas tank area. I think this is actually touched very briefly in the instruction manual as well, but it has been a long time since I picked that up now that I'm "done" with the car.

I trimmed mine down and covered neither. Don't plan on splashing through a lot of puddles so I don't expect any significant water coming up anyway and if I ever get caught in the rain with the top off, I want the water to get out (happened to me a few times in the C*bra).

[ben1272]

I thought the gaps around the perimeter of the fuel tank steel floor might be to allow leaking gas to drip OUT of the vehicle rather than stay trapped inside. I have read where the manual says to be sure to cover these slots. ???

FFR told me to leave the length and make sure to use silicone to bond the aluminum to the steel. Also said there was no particular reason that they are as long as they are. Was told also that the small square tab that protrudes forward is there to cover holes in the steel floor used by welders to pull frame from welding fixtures.

I think I am going to cut my overhang shorter, and silicone it carefully. Probably even clean surface with surface prep too, just to be certain silicone sticks well. I also plan to leave slots in fuel tank floor open/not covered, especially since I have already drilled my floor this way!! :)

Still would appreciate hearing from anyone else who knows something about this or has an opinion.

Thanks!

-Ben

[ben1272]

Oh, one more thing. If the aluminum floor WAS extended under and covered the slots in the fuel tank floor, any leaking fuel here could travel down through slot and onto aluminum floor and out under the seats.....seems like a bad idea. Draining to the ground seems wiser? I have no particular experience here, just trying to be logical. Am I missing something?

-Ben

[lance corsi]

I used the aluminum sheet scheduled for the floor as a rear bulkhead liner, since I relocated the gas tank. Then I removed the steel floor plate beneath the FFR gas tank location and added back a sheet of 11 gage steel stretching from the back of the front pan to the rear bulkhead. This should insure against cabin intrusion in the event of an accident. I know I've added weight but I'm willing to accept the trade off.

[DSR-3]

Agreed. The intent by FFR is that you would cover the gaps both in the floor of the footwell and in the floor of the gas tank area. I think this is actually touched very briefly in the instruction manual as well, but it has been a long time since I picked that up now that I'm "done" with the car.
If that's the intent- I'd like to hear it from FFR. My manual has no mention of covering any slots I can find (not a good design/solution anyway), and the 1 picture shows a panel that fits across the rails only- no overlap of the steel floors. I hope they can respond with an answer soon.

[lance corsi]

My opinion of the FFR supplied floor plate is not good. #1 there will be moisture at that level, which will eventually leas to galvanic corrosion. #2 the .040" aluminum offers no significant protection from cabin intrusion, #3 the piece supplied doesn't really fit, #4 if the FFR gas tank leaks, I wouldn't want to rely on the floor slots to evacuate the gas smell , #5 the front floor pans required some work to straighten out because of the oil canning effect after welding. So, I suggest to anyone who cares, exercise your builder's discretion on this and go with what makes you comfortable. Another piece of aluminum or steel to remedy these problems isn't really expensive and prolly won't be the cause of you exceeding your budget. Now is the time to fix this problem. IMO.

[ben1272]

It would be interesting to hear from Jesper or Jim with regard to why they did what they did so we could at least understand the design intent.

[billjr212]

Jim has already answered this question. Don't over think it.
http://thefactoryfiveforum.com/showthread.php?13371-Under-Seat-Alum-Orientation&p=139814&viewfull=1#post139814

[THE FURNACE]

I think a good alternative to silicone would be to use butyl tape. It comes in several widths and thicknesses. Less messy to use, and would keep a consistent gap between the aluminum and steel sheets. Galvanic corrosion might still occur at the rivets.