[QUOTE]Originally posted by outoforder
I know that some airplanes use ducting around their radiators which
not only has low drag, it actually converts the heat dumped into a
small amount of forward thrust.

 

Plus route air to the engine compartment and brakes.

 

why not semi-permanently attach it to the underbody with bolts or something and create removable panels near the places where you need to service, i.e. oil, tranny, diff, etc.

 

It would have to be a single piece transfer the load. Bolts would create stress concentrations that CF is not good at handling. Piecemealing it would not accomplish the ultimate goal of transfering load. If it were velcroed, you could easily remove it during servicing. CF is flimsy and will easily bend. It will not take a bending load unless you separate it with some sort of spacer like honeycomb.

outoforder:
Is the rated shear load for the velcro for the adhesive or the hook/loop? If it is an adhesive issue, we could always use an epoxy-based adhesive.

Correct me if I'm wrong, but what you're envisioning is a link between the diagonal wheels like a giant x-brace?

 

• The bolts hang down from the bottom of the car, reducing ground clearance by more than a layer of velcro and a layer of carbon fiber.
  
  
• The clamping force of the bolt will tend to crush the carbon fiber sheet.
  
  
• The bolt + washer has an area of perhaps one square inch, assuming you engineer a shear transfer layer underneath the area covered by the washer. Thin sheets of carbon fiber aren't very strong in small areas, so to generate a lot of force from one suspension mount point to another, you would need to make the carbon fiber sheet fairly thick around the bolt attach points. This is going to exacerbate the first problem... and that shear transfer layer is going to look a lot like the velcro I'm thinking of.
  
  If you don't have a shear transfer layer, then you'll end up with the carbon fiber sheet getting shredded by the side of the bolt.
  
  
• Bolts just won't look as clean as a smooth flat bottom. Of course, that bottom will shortly be covered with stuck-on road debris, but until then, it'll look really good!

I've thought of another annoying problem. When you bonk a frame member on a speed bump that was just a little too big, you end up with a shiny spot on the bottom of the car. No biggie. The same mistake with this sheet installed would lead to a loud crunch, followed by a scrape, and if you looked under the car a few days afterwards you'd see something just like a fiberglass panel ripped in half hanging down. Drive down the freeway after such a mistake and you'd end up drizzling folks nearby with expensive bits of carbon fiber.

The bottom of the car is a lame place to put brittle objects. Of course, anyone with an aftermarket diffuser panel or rocker panel has got the same problem. And I wonder what the MTBF is for those undercar neon rigs?

 

The best way to create downforce from this panel would be to turn it up at the rear and mold Venturi's into the carbon itself to create a vacuum under the car. Hey it works for Ferrari. I cant for te life of me find a decent picture of this, a little help?

 

bbsilver,

Exactly: a giant X brace between all four wheels, but really thin.

Here's the page on dual-lock: http://www.3m.com/us/mfg_industrial/adhesi...0709-3869-4.pdf

Dynamic shear strength is 31.7 PSI, which is good. That's the shear for the engagement surface. The pressure-sensitive adhesive (300 LSE) is quite a bit stronger.

I'm having a little trouble understanding the static shear spec. They say it will hold 2 PSI in shear for a week... I think this stuff creeps, which means no static pretensioning of the sheet, which is unfortunate. Maybe I can use straight preformed ridges next to pads of dual-lock to handle pretensioning stress. Straight preformed ridges would give me quite a lot of misalignment flexibility at the attach point, which will be handy when the mechanic tries to reinstall the sheet on a hoist which bends the car differently than when it's on the ground.

There is no stress vs. strain curve, so no way to know how much compliance there is in the fastener.

The weight looks good: 0.31 grams/square inch. So 1000 square inches of the stuff will weigh less than a pound. And it's 2.7mm thick, which means I can probably lose less than a half inch of clearance under the car.

 

If it works it will be worth the effort put into it. Even if ti doesnt think of how delicious it will look with an entire CF underbelly. MMMMMM, CF underbelly.

 

I think the stock S2000 would not work well with an undertray, and would likely result in positive lift, the opposite of what you are shooting for. The S2000 would have to be extremely low and be equipped with an adequate splitter in order to not allow airflow from entering below the chassis. Much lower than I think most people could deal with. The underbody kits placed below race cars are also not completely flat, but have channels to create downforce resulting from the Bernoulli effect. You wouldn't want to recreate the Le Mans CLK-GTRs

-- Chris

 

maybe this is what you are looking for:

Cusco Reinforcement Bars