Take a gander at the picture below – it shows the start of my new composite fuel tank. In this post I want to talk a bit about the motivations of what I’m doing and how I’m going to construct it.

BLUE – the three layers of kingspan that make up the back of the tank, stepped at an angle

GREEN – the tank shape in the transmission tunnel.

RED – the ATL fuel-cell sender going down the tank.

I’m making the composite tank for the following reasons:

1. the original tank was an MG Midget tank, and sat way out back and high, behind  the cross-member that the red arrow straddles. With a full tank this made polar moment of inertia less than ideal
2. the steel tank was rotting anyway
3. steel is heavy, well made composites are not
4. there’s a lot of dead space in the area where I want the new tank (i.e. where the red and blue arrows are, and above the prop-shaft where the green arrow is.
5. i can move mass down in the car
6. i can make the tank gated, preventing fuel from slopping around
7. I can move the tank inboard, protecting it from impacts
8. i can save weight, overall.
9. when sprinting, I will only fill the car as much as the transmission tunnel tank, but when I want range, I can fill the tank to the brim, getting extra capacity over the original tank
10. i’m going to fuel injection so needed a new tank anyway.

I’m going to make it from two layers of 300gsm aramid with a partial soric core for hard-points, with 2x 200g eglass on the other side of the core. There will be soric ribs for strength. the compartments will be three layers of e-glass, and everything will be epoxy resin infused.

It’s not a structural component, but should be very strong in itself. What you can’t see on the above photo (a teaser) is the tank going down to a point at the front in which the submerged in-tank fuel injection pump will reside. If done right this will also be the lowest point and will act as a sump to ensure the pump never starves. Gravity is my friend.