F1 car design in Catia V5 viii

Here's where we're at right now

I've got some nice reference pictures from my book, so I'm going to use my reference photos to shape the underside of the monocoque. Good luck finding pictures of the bottom of F1 cars. The flat bottom shouldn't be a problem, but images of diffusers and splitters in detail are hard to come by.

I'll start a new geometric set and put a point in at the height of the mating of the monocoque and floor.

Make a line from this point to the back of the car

And another line in the zx direction which is longer than the width of the car. Mirror this line in the dialog box so we can cut both sides at the same time.

Create a sweep using these lines

Define UNDERSIDE LOFT - SURFACES as the in work object. Join the Multi-Section Surfaces.

Cut the joined Multi-Section Surfaces with the newly created Sweep.

Hide the sweep and lines, turn the model over, and see what we've got

It's a lot rounder and wider that what I'm looking for

Unhide PROFILE 3.

Get a front view. We're going to tune this curve

That's more like it.

Except it's decidedly not a class A surface.

The problem is the transition that is occuring at PROFILE 2. This profile has curvature imposed on the bottom forcing it to be flat. That transition from flat to rounded is making a weird shape. Let's modify this profile and the associated guide, so that this profile isn't perfectly flat on the bottom, but still preserve the appearance of being mostly flat in the Multi-Sections Surface from the front up to this profile.

Delete the split, join, and multi-sections surfaces touching this profile.

If we just take away the curvature impositions, we get a bit of a mess

If we add the center point it's really not that much better.

What we need to do is raise these points up just a little bit, and tinker with the tangency tensions.

But to do that, we're going to have to alter the guides, otherwise the profile won't intersect with the guides anymore.

So first thing I'm going to do, is figure out how far I'm going to have to go up, to get this mostly flat on the bottom. Define PROFILE 2 - POINTS as the in work object. Add a point using the right point as a reference.

Apply symmetry to it.

Free the points

And contrain them to the new points

Tune the curves to get the points as low as possible, while maintaining the bottom line as straight and convex as possible.

That ought to do the trick, and it's only 4mm higher than before. Now I'm going to need to modify the guide, so that it intersects this profile.

Here is the guilty party

Split the guideline at PROFILE 3 of the NOSE UNDERSIDE reference line.

Project that point we created before which was 4mm above the old profile onto the zx plane.

Create a new 3d curve connecting the split line and the projected point. Make sure it is completely above the old guide.

Join it, and smooth it, freezing the split.

Go to the 3D GUIDES and replace the old side profile with the new one we just made.

This is what it looks like now

Alright, make the front Multi-Section Surface again using these guides.

And the multi-section surface connecting the two and tangent to them.

Hmm, looks like we just shifted the same problem forward. The green I'm satisfied with, the red I'd like to see smoother.

I'll have to think about this.