Started the composite fuel tank

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.

tank 1 with arrowsBLUE – 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.

6 thoughts on “Started the composite fuel tank

  1. It does – There’s a 2″ gap between the bottom of the tank and the prop. It’s an IRS setup so I’m not worried about the prop moving around. I’m also building prop-catchers into the transmission tunnel so the prop won’t be able to get to the tank.

    According to Warren’s rules of composites, every component should do at least two jobs. The prop-catcher top will be built into the tunnel as a longitudinal cross-brace as well, adding strength and rigidity to the already bonded in tunnel.

    I have to think really carefully about packaging because once the tunnel is in, it’s bonded in for ever.

  2. I’ve got loads of photos, and a lot to do on this one – and because I’m not after fantastic showroom quality surface finish I can move more quickly. Warren’s been helping me with the latter so it takes a little longer.

    I’ll keep a faithful diary on this one.

  3. Thank you, If I made a mold for a flat dash panel and paid for materials would consider showing me the process of resin infusion? I ask because there is a large set up cost and I want to find out if this is something I can do.

    • Hi
      I found it cost me £360 to get the resin infusion starter kit from Easy Composites, and then I bought cloth as well, which took my initial starting price to nearer £700, but I was going in deep and committing early.

      I suggest you watch their instructional videos on youtube – the series “how to copy a BMW Bonnet” is excellent, and takes you through all you need to know about infusion.

      I’ve found that making moulds is by far and away the most time consuming part. If this is just a one-off, your best bet is to make a pattern (a mock-up of the part) and then get someone like Warren from Carbon Copies to take the mould and pull you a part.

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