Floorpan sheetmetal thickness????

BlackGMC

New Member
Feb 6, 2007
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Well I have almost finished my subframes and all the bracing on my mustang. I am going to be making my own floorpans since the stockers will not fit. I was wondering what gauge thickness I should go with. With the new subframes, the actually floorpans will not be as much of a structual componet as they would be in stock form. I believe the stock floorpans are ~18gauge. I was thinking of using 20 gauge with beads rolled in them. Rolling beads in 20 gauge will be easier than rolling beads in 18 gauge. What do yall think, going with 20 gauge will offset a few pounds (~40 pounds).
 
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I would say your fine seeing as you have such a strong structural foundation, and that all the floor pans would really be doing is keeping your feet from scraping and Mcdonalds creamers and such within reach, it would be fine to do so.

Maybe you could add som ridges(for lack of tech. term) with a break to your floor pan for additonal strength and support forthe cars contentes weither its you welding another part of your car or just stuff.

Though I am not an engineer of any sorts.
 
I would not recommend it. The cars rely too much on the floor pans as a structural member even with sub frame connectors. I have seen these cars suffer structural damage from jacking them incorrectly. The existing sheet metal is a little on the thin side for the design. That is why most of us add the subframe connectors.

The only way that I would feel comfortable with something like this is if the car had a full cage and had a tubular subframe added in. Just my $0.02
 
Huh, two different answers. Well let me clarify a few things, probably should have added some pics before. The car will get a 4 point cage, I might add door bars.

Here are a few pics of the subframe I built, these are not off the shelf subframe connectors by any means. Off the shelf subframe connectors are using ~1/16 thick, these are 1/8. The rear torque boxes have been eliminated and replaced with a 2X4 crossmember. The front torque boxes will also be eliminated and replaced with 2X4 box. The firewall will be cut out and replaced with a flat sheet and reenforced with 1.25 square tubing runing across the entire firewall and down the sides tieing into the 2X4 tubing that is replacing the torque boxes. I can't think of anything else I could add or beef up, but IMO the car is solid.

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Based upon what you have done, I guess that beaded 20 gauge would work. (to keep your feet from dragging on the ground and dropping your keys on the ground)

Not knowing what you have planned for the car, well you are on your own...

I am sure that the different sanctioning bodies will have their own recomendations.

John
 
SnakeStang65, I really just plan to make this a street car with the ocassional drag down the strip. Do some sanctioning bodies have rules on floorpan thickness? I guess to be safe I will probably just use the 18 gauge, since that is what I think the factory thickness was, just to be safe. The replacement rear seat pans I bought were 18 gauge. Thanks for the advice, your welcome to give me some more or recommendations on what I should do.
 
Here is a picture its just a stock mustang floorpan, theses "ridges" create alot of rigidty. Try and bend a flat piece of 18 guage metal, the try to do the same thing with 18 guage that has the enhanced structural characteristics of these "ridges" and you can see how much it helps. This it why anything built with sheet metal normally has them. Though like I said I am not an engineer and truely don't know.


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SnakeStang65, I really just plan to make this a street car with the ocassional drag down the strip. Do some sanctioning bodies have rules on floorpan thickness? I guess to be safe I will probably just use the 18 gauge, since that is what I think the factory thickness was, just to be safe. The replacement rear seat pans I bought were 18 gauge. Thanks for the advice, your welcome to give me some more or recommendations on what I should do.

Not on the sheet metal for the floor, but you might get into issues with the frame, its connection to the rockers, and your cage. There may be restrictions on fire walls though. Of course, it all depends on how fast you plan on going... and who's track you are on...

If it is going to be mostly on the street, you should be fine with rolled 20 gauge and the supporting that you have established. If anything, I would consider connecting the rocker panels to the subframes (it looks like you are mostly there), and then you need to provide a cross connection between the sub frames (perfect for a drive shaft loop).

John
 
If anything, I would consider connecting the rocker panels to the subframes (it looks like you are mostly there), and then you need to provide a cross connection between the sub frames (perfect for a drive shaft loop).

John

John, thanks for the input. I am not quite finished, and I have not posted recent pics. I have connected both subframes to the rocker panels via a 1/8 plate welded to the rockerpanel. and I have already got the cross connections worked out, I am going to finish welding them in today. Thanks for the input.

Here is a picture its just a stock mustang floorpan, theses "ridges" create alot of rigidty. Try and bend a flat piece of 18 guage metal, the try to do the same thing with 18 guage that has the enhanced structural characteristics of these "ridges" and you can see how much it helps. This it why anything built with sheet metal normally has them. Though like I said I am not an engineer and truely don't know.

I don't have the tooling to be able to roll that size of ridges/beads. However I do have a bead roller and I plan on rolling in some beads. The bead roller I have can roll 1/4, 3/8 or 1/2 beads. I think when you refer to Ridges, you might actually mean beads.

Thanks for all the input guys. I posted this on a couple of forums and the responses I got, I am planning on going with 18 gauge.
 
Personally, if it were my car, I'd buy stock floorpans and make them work with the bracing. I guess it depends on how good you are with your sheet metal tools.:shrug: You can definitely make your own if you have the tools/skill. I made some pans out of salvage stock for a 65 chevy pickup once and when I was done they looked factory. That is, unless you looked at both sides at once - they didn't match.:eek: