Making a Prototype Race Car Fit a Tall Driver

Our Nova Proto NP01 arrived from France in August. Before it turns a wheel in anger, it has to fit the person driving it — and at 6ft 2in with long legs, that was never going to be a bolt-in job.

This is how a prototype gets fitted to a big driver: a carbon seat shell cut in half and widened, a poured seat insert made around the driver's actual body, and a pedal box that still needs to move.

Most prototypes are built for small drivers

Start here, because it explains everything that follows.

A lot of prototype chassis are simply not made big enough for a large driver. They tend to be designed around smaller people, and if you are tall or broad you spend your career discovering which cars you physically do not fit in.

The NP01 is one of the few that works well for a driver our size. That is a large part of why we have stayed with this chassis rather than chasing something else. It gives us a starting point we can work from — but "works well" is not the same as "fits out of the box."

The factory shell was too narrow — and wrong in the legs

Two separate problems, and it is worth separating them because people assume seat fitment is only about width.

The shell was too narrow across the body. That much was obvious. But the leg area was also wrong for a tall driver — the shape simply did not suit long legs, and no amount of padding was going to fix geometry.

So both areas had to be modified.

Cutting a carbon seat shell in half

The method is blunter than people expect: the shell was cut in half and widened with carbon fibre.

The shell split and set up against an aluminium form, ready for layup.

With the shell separated, an aluminium sheet was used on one side as a form to lay up against — it gives you a clean, rigid surface to build the new section off and holds the geometry while the resin goes off. From there it is a wet carbon fibre and epoxy layup bridging the two halves at the new width.

Mechanically it is not exotic work. What it takes is patience: it went through multiple layups rather than one, and each one has to cure before the next. We were on a time crunch, and the shell is what delayed the seat pour.

It came out stronger than the factory part

This is the question everyone asks about cutting a structural composite part in half, so let us answer it directly.

The modified shell is stiffer than the original. While it was apart we added additional carbon, because the factory item was frankly a little flimsier than we thought it ought to be. The modification was an opportunity to fix that, not a compromise we had to live with.

Getting it back into its original mounting location is tedious, which is normal for this kind of work. The mounting points have to end up where they started even though the part between them is now a different shape.

You cannot buy a seat for a car like this

Before getting to the pour, it is worth explaining why a custom seat is not a luxury here.

There is no seat you can buy for this car. There is no real place to mount one. You are essentially sitting on the chassis itself, and there is barely any room to work with. Even if a suitable off-the-shelf seat existed, it would not solve the problem.

The upside of being forced into a custom seat is considerable. Because the insert is formed around your actual body and the whole assembly is effectively bolted to you, it is extremely comfortable and very safe. Loads spread across your whole back and hips instead of concentrating on a few contact points.

What a seat pour actually is

For this car we had Brian of BSF Seat Inserts come out and do the pour. We have worked with Brian for nearly eight years across a number of seats, which matters more than it sounds — someone who already knows how you like to sit saves a lot of the guesswork.

Here is the process, start to finish.

First, foam and position. Brian builds up a structure of foam around the driver in the car. He asks how much foam you want and uses it to set the seating position, checking as he goes that your arms can move the way they need to, that you are centred in the car, and that your reach to the pedals is right. Nothing is permanent yet — this stage is all adjustment.

Then the bag. Once he is happy with the foam layout, all of it goes into a bag. He mixes up the two-part chemical foam — a BSCI seat insert pour kit, which uses an SFI 45.2 approved foam — and pours it in where the driver is sitting, working it in around your legs and back.

That certification is worth pausing on, because "foam poured around a driver in a garage" does not immediately sound like a safety item. SFI 45.2 is a real specification, and the foam is tested against impact and flammability requirements to meet it. The finished insert also gets wrapped in a fire-resistant covering. A poured seat is not a comfort hack — done with the right materials it is certified safety equipment, and for many sanctioning bodies that certification is the point.

Then it grows. The foam slowly expands and fills every void around you, and Brian manipulates it as it goes to get it where he wants it.

Ten minutes that decide how you sit for years

The part nobody warns you about: you have to sit still in it while it cures, and it takes about ten minutes.

Two things make that harder than it sounds. The foam heats up as it cures — it is an exothermic reaction and you are wrapped in it. And it is pushing on you the whole time as it expands and hardens, so you have to actively apply pressure down to hold your position. Go soft for a moment and the seat sets around the wrong posture.

Once it is hard, it comes out and Brian trims it back and cuts the holes for the belts. The trimming is what you can see him doing in the photos above.

The finished insert on the bench, before it goes into the car.

Getting the position right is the whole point

Seating position and seat angle are set by the driver and by whoever is doing the pour. It helps enormously if the driver knows what they want — and it helps just as much to have someone experienced guiding it. We have had quite a few seats made over the years, so we came in knowing how we like to sit. For a driver who has not done this before, someone like Brian is worth a great deal.

What gets locked in at that moment is essentially permanent, which is why the hour of fiddling with foam beforehand matters more than the ten minutes of curing.

What we found once the seat was in

Honest assessment, because a build report that says everything is perfect is not worth reading.

The steering wheel is a bit too close. In our other car it sits further away and that suits us better. Moving it may mean modifying the steering shaft by cutting it, which we would rather not do — but it might be the only solution.

The wheel is also larger than the one on the old car. Combine a bigger wheel with a cockpit sized around the chassis and the result is elbows catching the chassis slightly on turn-in. Not dangerous, but not something you want to notice at hour three of an enduro.

The pedals: one hole left

The pedal box has four mounting positions. It arrived in the third, which leaves one more.

Moving to position four puts the pedals roughly two inches further from the driver. For legs as long as ours that is welcome, and it is the next change on the list.

It is worth appreciating that the position exists at all. A chassis that only offers a couple of pedal positions has quietly decided what size driver it is for. Four positions, with the fourth two inches out, is a designer acknowledging that tall people race cars too.

Why fit is worth this much trouble

All of this — a carbon shell cut in half, a resin pour, a pedal box that still needs moving — happens before the car has turned a single lap.

The reason is simple. A driver who does not fit the car is fighting it. You brace where you should be relaxed, you run out of travel where you need leverage, and in a long race you fatigue faster than the person next to you who is simply sitting comfortably. None of that shows up on a spec sheet, and all of it shows up in lap times at hour two.

Fitting the driver is not the finishing touch on a race car build. It is part of the build.

More on this car

• Importing a race car from France: what it takes
• Norma M20 FC engine development — the 2.3L stroker K20
• Endurance racing the number 03 Norma M20