Mocking up the bonnet & Rookie Mistakes

Mocking-up Bonnet

Making the bonnet is going to be a huge challenge, so I decided to mock it up. There was still plenty of fabrication to finish on the inner wings, but I was out of gas and it was a Sunday.

I’d nearly finished the driver’s side inner wing, but that would have to wait for a while. The cut out around the radiator was unfinished and the front edge sat on the bench.

Mocking-up Bonnet

There are those out there that will read the following and think – Oh Dear, What a Rookie!

For the bonnet, I had the wooden buck and the wire-frame but I was wondering if there was any short-cuts I could take by re-profiling an old one. Doh!

I’m a novice at metal-fab and certain shapes worry me. Lots!

I was comfortable with fabricating the rear section off the bonnet, but the front nose was probably a little beyond my skills.

I had a ’50 Ford Prefect bonnet that wasn’t even close to the right shape and several from a ’39 Austin 8. One of which, although originally quite thick steel, was in pretty bad shape. When you held it up to the light, hundreds of light spots shone through. I think the back edge had spent several years in a river and was now mostly fibreglass and resin. 

Although less than 100 remain on the road, this Austin 8 bonnet had realistically seen better days. However, the front ‘nose’ portion could be my saviour.

I wrapped some 22awg steel around the side edge to see how far off the profile was.

It wasn’t looking too good.

There was over an inch gap between the bonnet and the steel sheet. I could try and re-bend the crusty steel but but the bend would make the embossed side ridge look odd. Physically, re-bending was easy, but the crunching sound wasn’t so encouraging.

Mocking up bonnet

The bonnet wasn’t a true U shape as the sides had a curve front to back. My crudely rolled edge was straight as I wanted to see if I could get away with a straight sides.

Nope, it looked wrong.

The bonnet was a little narrow for my needs, so I cut it up. – or should I say, snapped it into 3 with a pile of ancient filler for my efforts.

Mocking up bonnet

After I cleco’d in a pair of 2″ strips, I could stand back and see the vertical edge profile was too square. The edge of the nose would not flow into the grille and there would be a visual kink (yellow line).

After all this simple mocking up, I came to the conclusion that I need to bite the bullet and make a bonnet from scratch.

– I was dreading that

New tools needed

My buck is solid, so I’ll start by making an open version. I’ll also make a set of strips similar to ‘engineers sweeps‘, like these sold by Justin Baker. 

Not having a CNC laser cutter and a very small budget, my version of these sweeps are going to be time consuming to make. However, for a novice like me, they’ll be invaluable.

When I made the buck, I kept as many of the curves the same front to back, so 1 or 2 sweeps should hopefully see me through.

With these aids fabricated, I’ll have enough to make the internal strengthening ribs. The bonnet skin however, still might be beyond me.


……. no short-cuts, in fact all this mocking up had simply reinforced the enormity of the challenge I was facing.

If I hadn’t have run out of gas I’d be a lot more optimistic right now.

This is me mocking up the bonnet with the front 1.75″ lower than the rear. It gives the front a much more sleek & swept back look.