Hello, and thanks for any advice you can provide.
I am planning on making a floor tray for my superkart, by vacuum infusion with carbon and kevlar. The design and overall dimensions are shown in the attached photos.
This will be my first vacuum infusion and carbon/epoxy part. I have done wet layup of glass/polyester before, but I guess this is a totally different beast.
The floor is an aerodynamic aide to reduce drag. Top speed for the kart is about 180km/h, so the floor does provide a small amount of downforce, but it its main purpose is just to smooth the flow under the vehicle, so I consider the part to be “non-structural”.
The floor will be fixed to the frame by bolts (or zip-ties) in the 10 dimpled locations, hung with 4 straps fixed along the back edge, and zip-tied to the side intrusion bars in several locations. So support for the surface is fairly evenly distributed.
I plan on using kevlar for the bottom layer, since the kart does regularly scrape the ground on some of the rougher tracks, and driving in the pit area. Fiberglass floors regulary wear through completely in certain spots, so kevlar would be an advantage in this regard. I will use kevlar on the flat areas only, and not up the sides. i.e. I will trim the fabric to neatly fit the flat area, so I will not need to trim it after moulding.
On top of the kevlar, I will use 2 layers of 200gsm carbon, and 2 extra layers around the dimples and in the front section where my feet go. Some flexibility is desirable. If the floor is too rigid, it will cause problems with how the chassis functions.
For your understanding: in a kart, bending/torsion of the chassis is a major factor for balance and grip, and the bending/torsional rigidity is adjustable with removable stiffening tubes and struts. The floor also acts as a structural member, so the bolts can be replaced with zip ties in some areas to allow additional compliance. Hence why I don’t want it too stiff…
I will make the female mould directly from MDF, since it is mostly flat surfaces, and relatively easy to apply a decent uniform finish.
These are my questions:
- For the mould perimeter, should I extend the short vertical sides up further, and use the vertical surface as the flange for fixing the bag, or, can I go horizontally out from the sides, and have horizontal flanges on the mould ? Horizontal flanges will be far far easier, so this would be preferred method.
- In the case of the horizontal flanges, I will have to run the fabric from vertical wall, over the corner onto the horizontal surface, so is there a minimum radius that I have to use on that edge, or can I leave the edge square ?
- Where would you suggest I attach the feed and vacuum lines ? I can forsee a problem where the front section is much narrower, and also having extra layers of fabric, I assume the infusing will travel faster there ?
- I was thinking that I should feed into the middle of the part, and run several independent vacuum lines around the perimeter (for example, one for the front, one at each side, and one along the rear), and pinch off the vacuum lines in sequence as each starts to pick up the resin, which would allow the other areas to continue to pull resin.
- Do you think that the “sharp” internal corners (4mm radius) could cause problems ? Problems with racetracking or bridging ? I thought it would be easier the get the 2x 200gsm fabrics into the corners, rather than using a single heavier fabric. And since the part doesn’t have to look pretty, I am fine with cutting notches/slits in the fabric to get it to conform as best I can. Any other thoughts or suggestions ?
- I have read that one way to improve the ease of removal of the peel ply is to add a layer of perforated release film between the peel ply and the infusion mesh. Is this true ? Will this negatively affect the infusion process ?
- Any other thoughts or suggestions in general ?
Thanks for your assistance.
Sam