Miata Flat Underbody
#1
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Join Date: Oct 2011
Location: The Race Track & St Pete FL
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Miata Flat Underbody
I know ThePass is just in the final testing of his Flat Underbody,
but I was going to do the same thing before I went to Afghanistan. ThePass: I read everything you had to say and all the input other people had on the topic. I also bought a few books: Aerodynamics Competition Car,
Suspension Competition Car and Composites Competition Car to give me
inspiration.
For the main throat I am going to have a 1 deg rake to provide the down
force and be held on by 16 Dzus Fasteners (8 on ea side). The rear
diffuser, of course, does not produce downforce, but the math i'm going
with is the front open area under the bumper plus 20%. The 20% added
will offset some of the air that comes in from the side of the car and
the rear tire.
I will add some pics here soon
but I was going to do the same thing before I went to Afghanistan. ThePass: I read everything you had to say and all the input other people had on the topic. I also bought a few books: Aerodynamics Competition Car,
Suspension Competition Car and Composites Competition Car to give me
inspiration.
For the main throat I am going to have a 1 deg rake to provide the down
force and be held on by 16 Dzus Fasteners (8 on ea side). The rear
diffuser, of course, does not produce downforce, but the math i'm going
with is the front open area under the bumper plus 20%. The 20% added
will offset some of the air that comes in from the side of the car and
the rear tire.
I will add some pics here soon
Last edited by 1993ka24det; 12-08-2012 at 05:29 PM.
#2
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Here are a couple of pics
These are the 16 Dzus fasteners that will be holding up the underbody, Plus there are 4 more to put up on the undertray/air dam
This diffuser is from 5 years ago for my 240sx project. This is not going to be the final piece, this is just to hold over until I have extra material to build another one. I had to shorten the width to fit on the Miata by about 8 in.
These are the 16 Dzus fasteners that will be holding up the underbody, Plus there are 4 more to put up on the undertray/air dam
This diffuser is from 5 years ago for my 240sx project. This is not going to be the final piece, this is just to hold over until I have extra material to build another one. I had to shorten the width to fit on the Miata by about 8 in.
Last edited by 1993ka24det; 12-08-2012 at 05:28 PM.
#5
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So here was my idea of keeping the Dzus fastener brackets in line and level. I took the slotted angle steel and drilled it with a step drill bit to match the taper on the fasteners. Attached 8 of them to the angled steel and welded them up after I ensured the car was level. I put a rake to the fastener brackets.
How I have the steel angle set up. I left the other 2 Dzus to show how big the holes had to be
Ground down the tar for weld prep
After welding and with a little bit of black paint
#10
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That's a purty big sheet of aluminum
What kind of thickness are you using?
Here's my version 2 flat bottom mid-section. Version one was mostly ABS, version 2 is more aluminum to resist heat:
What kind of thickness are you using?
Here's my version 2 flat bottom mid-section. Version one was mostly ABS, version 2 is more aluminum to resist heat:
#15
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+1 on the alloy. You already bought your sheet but for others a 5000 series aluminum is easier to bend and less likely to crack. At some point of thickness a 6061 sheet is hard/impossible to bend into sharp corners without cracking or at least making it weak, even with a proper sheet metal break.
0.063" may be OK. That's pretty thin. Or maybe you are not going to bend it at all.
0.063" may be OK. That's pretty thin. Or maybe you are not going to bend it at all.
#16
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I expect that that sheet at that thickness weighs 20 lbs, maybe a bit over. Curious if the OP can weigh it and find out. Then there's still the weight of hardware and additional brackets, etc. to add in.
#19
60 ft^2 x 144 in^2/ft^2 = 8640 in^2
8640 in^2 x 0.063in = 544.32 in^3
Density of 6061 T6 = 0.0975 lb/in^3
MatWeb - The Online Materials Information Resource
544.32 in^3 x 0.0975 lb/in^3 = 53.07 lb
We get our shipments of sheet aluminum by big trucks