Under tray Thickness

I am still drafting on paper the design of my undertray combined with a front splitter and rear diffuser that I would like to make for my vehicle . What would be the right thickness for such things ? I am going to be making it out of aluminium and I was thinking of going 2 or 3m for the splitter/undertray and approx. 5mm for the rear diffuser .

In such cases how do you choose the thickness of such things ? Would it depend on the use of the car ? Circuit , drag etc. , top speeds ?

Thank you!

Hi, good question and this is difficult to answer without understanding the loads these parts will be under. I would say 3mm maximum for both front and back Aluminium splitters, the more folds and reinforcements mean that you can get away with a thinner, lighter and more rigid splitter. The ones I have made for my Hilux are 3mm, 5mm will be very heavy, although aluminium is light it is still very heavy in 5mm thickness.

Do you have any photos?

Thanks Nigel for the reply . At the moment I have no photos as I haven't even started making anything yet . My plan is to use the car as an all arounder so some stuff will be on off . Like I want to make a rear wing for when I hit the drag strip similar to the CCC rear wing that I can use when I hit the drag strip as well as rear diffusers and side skirt similar to the infamous (and one of my favourite cars) the Gringotegra Miles Kerr car .

But at the same time when there is a circuit event that I can take place I would like to switch to another set up if its more suitable etc. and so on . Since I am not trying to make any records and just having fun learning and expanding I am trying to take full advantage of the courses .

What type of reinforcements can be done in general ?

It is going to depend on how the parts are loaded, how large they are, how many mounting points there are and how they support the device.

This is one of the rare cases where 'monkey, see, monkey do' is a good starting point. Have a good look around and see what others are doing and theat should give a good start point - learn from their breakages.

The front lip, and rear wing, can be subject to neglible loads with a bad design to several hundred pounds/kgs with effective, large, agressive designs at high speeds, so may need to be substantially mounted, while a rear undertray is usually relatively lightly loaded because it is hard to get them to work well, especially if no undertray is used or there is a fair distance between it and the track surface.

Don't forget the importance of balancing the gains front to back - you do NOT want a forward bias to develope at speed, it can make the vehicle very difficult to control. There can also be a lot of interaction between all the earo' aspects - an change to one part can have a drastic change elsewhere, as can a device that goes into stall at speed.

While I have done some airflow studies a long time ago, I really don't feel comfortable advising on a unknown case - however, you should be able to find some good text books aimed for the motorsport enthusiast on AMAZON, or some other on-line book retailers. There are some that specialise in motorsport/engineering publications.