Yup, as I posted a while back, chassis stiffness is an important factor; helps in a number of ways, and gets more important as weight goes up to the 2.5k limit. As I described then, we're using a 1/2" balsa core that we laminate CF onto as a skin (top and bottom sides).JTMess wrote:Balsa Man, what thickness carbon fiber is your team using for the chassis and where did they find it? We have been having difficulties finding carbon fiber, which we may be using for states and we aren't sure which thickness will be rigid enough without holding it. Since the Lexan we considered wasn't rigid enough, we are now looking at other materials that will prevent deformation as the car reaches the bottom of the ramp.
The CF for the skin is a 0.014 " unidirectional laminate By itself, its quite flexible in two dimensions- you can roll a sheet piece into a tube. In the plane of the sheet, it's crazy stiff. It's important to understand, it's not just the 2 layers of CF skin that get you chassis plate stiffness- its the sandwich lam w/ the balsa core. When the CF is bonded, when you (try to) bend the plate, the forces go into the plane of the CF sheets on either side; one side goes into compression; tho other side into tension; the CF neither stretches nor compresses. The distance between the CF layers also affects sandwich stiffness- the thicker, the stiffer. The chassis plate also has CF strips around the edges- 1/2" x 0.030" When done, it's just ridiculously stiff- significantly stiffer than ....say, like a 1/2" piece of oak; maybe even a 3/4"; and at a fraction of the weight. Way stiffer than 1/8th T6061 aluminum, or even T7075T6. Lexan is great for some things (we have a number of Lexan bits), very tough, but sheet stiffness is not particularly good. Not too bad at 1/4", but nowhere near a CF/balsa sandwich, and you're talking significantly more weight. Our basic/bare chassis plate is less than 100 gr.
There are a number on on-line suppliers; the one we got ours from is here: http://www.cstsales.com/carbon_shapes_subpg.html
See Rectangular Carbon Fiber Laminates - a 12" x 36" piece for $27.55. It can be cut with a straight edge and razor blade; the blade will dull quickly, though.
Do be very careful about splinters when playing with CF, especially unidirectional sheet and strips - tiny and nasty. If cutting on a table saw, wear eye and respiratory protection; CF bits in eyes and lungs are not good for you....
