Final fitting of the tub


So, here is everything laid up as a reminder of where this started. I think it’s a good reminder of how far the tub has come, but at the same time it’s also making me think the duratec is photobombing everything in my garage.




Now, here it is in the car:

It’s pretty close to where I want it now, and I’m doing the final fettling. I made this with a positive mould, which has meant the outer surface (that fits to the chassis) isn’t perfectly flat. I’ve had to take it back a little at a time with the flap disk in the appropriate areas to be sure it fits. I developed a methodology to do this after I’d removed the obvious obstructions.

I go around the gap with a feeler gauge set to 0.7m, and look for areas it traps. When I find a trapped area, I set the gauge to 0.05 mm and see if that still sticks, and anywhere it does, I mark with tape (hence the packing tape on the tub at the back top) and take it back about 1mm with a flap disk. I deliberately only mark the jamming points rather than the tight points so I can avoid making gaps unnecessarily larger than they need to be.

Once everything is marked, I lift the tub out (it’s only 13kg, so two adults can easily lift it with fingertips) and do the sanding. When it goes back in it fits a little better. Everywhere is pretty much where I want it, apart from the back where it’s still a little high. Everytime I advance the fit, the back lowers down a bit. I have about 3-4mm left before it’s flush and I’m happy.

This one is a little more difficult to wrap your head around, but it’s the mating surface between the tub (carbon on the right, starting in the top right corner) and the chassis rail. As you can see, the gap is pretty uniform now, and I’m aiming for between 1 and 2mm.

It unfortunately means I’m doing to have to remove some of the powder coat with a flap disk.




Here is the birds eye view. You can just see the lip at the back. I don’t want to just sand it off – I think I can make the tub a better fir before I have to do that.

Then the final act before bonding it in is to have it lacquered and cured. Then I will have an awesome finished product.

5 thoughts on “Final fitting of the tub

    • Two different kinds of glues in two different places. There the fit is between 0.5 and 2mm I have a very slightly flexible epoxy, and where the gap is a little larger, a thickened epoxy mixed with glass fibre chopped strands. I’ve deliberately used glass not carbon for the adhesive to avoid any galvanic response issues.

  1. So this carbon tub slips in between the steel chassis?
    or Is this tub the centre section of chassis?
    Ive been following this for ages but now im lost.

    • Hi Dave – it’s a hybrid of that. I removed the top chassis rails that make up the top of the transmission tunnel, and the side rails between that ran laterally between the side rails of the space frame at the bottom, and the two longitudinal rails that would have formed the bottom of the transmission tunnel (I kept them). The tub then slots in from the top, and bonds on to the top and bottom rails, the bottom transmission tunnel rails, and the top lateral rail that the harness bolts onto.

      It’s fully structural, and is intended to replace the steel and aluminium with something lighter and stiffer.

Feed the attention-whore