What is the best way to make the ideal seat?

[J Chapman]

Hi. I've owned a Van Diemen RF03 which I've raced on / off in Mono 1800 then 1600 (following Kent conversion). But I've never been satisfied with the seats I've made. I find the two part expanding foam doesn't get under and around your hips and bum enough to give adequate support.

I tried Medina Motor Sports fibre glass seats which I found gives too much and moved around because my chassis is missing the mounting points

So I'm back to making a bag type seat. I like the idea of the Indi seat. But at 400 quid I cant help thinking there must be a cheaper DIY alternative out there. Any ideas guys??

[tristancliffe]

The 50 litre Indi-Seat kit is what is used for the majority of 'current' carbon tubbed cars, usually with fairly large cockpits and removable extraction shells. Depending on how much room there is in the cockpit of an RF03 (and how big you are) 'd imagine you might get away with a 40 litre kit, which is under £200. You often need the vacuum pump too, but can get away with a vacuum cleaner if needs be (especially if it isn't very powerful). A roll of TESA tape finishes them nicely (better than normal duct tape).

I haven't found an alternative between expanding foam (which I only use for drivers that aren't anticipating more than two days in a car) and a proper bead seat.

Expanding foam shrinks, cracks, turns to dust, goes hard, sticks to everything if it gets out of the bag, and often leaves voids... The bead seats don't shrink, stays supple to absorb crash energy rather than transferring it directly to your spine, can last several seasons without any noticeable degradation at all, and if done properly and carefully will not get in your hair, on your suit, on your belts or on your paintwork.

I know it sounds like I'm selling them, but I am just a fan of theirs (and I did spend a couple of years as one of the travelling fitting team on and off) and their product.

My personal opinion is don't bother with the Real Essential kit, which is effectively a clone of the Indi-Seat from about 2007, whilst Indi-Seat has moved on considerably (energy absorption, product life, ease of making, curing time etcetera).

[RobManser]

What width of TESA tape would you recommend Tristan?

[tristancliffe]

I've used 2 inch (50mm). You could use narrower for tricky areas around belt slots, but I tend to tear the 50 into 25mm as I need it.

One roll easily does a seat, probably two.

[RobManser]

Thanks Tristan. I couldn't find a seat fitter in the end, so the guy who rebuilt my car is helping me make one tomorrow. I'll order some tape now.

[RobManser]

A couple of questions if I may, and I'll ask on the forum as it may help others:

1) Am I supposed to remove (cut away) the vacuum bag before covering with the tape?

2) Is it normal for the thinner areas of the seat, i.e. the sides and the portion under my legs, to be flexible? The area under my back has set hard, but the thinner sections are still flexible. My garage is centrally heated so we did the entire mix and 24 hours of curing at 21.5 degrees C, halfway between the 20 and 23 degrees reccommended, and followed the instructions to the letter.

[RobManser]

By the way, if it helps J Chapman, I have a carbon tubbed F Renault, am 1.77m tall and weigh 70kg and needed 61L of beads to make the seat (a 70L kit with 9L removed). This was the same as the last kit I attempted for this car last year.

[tristancliffe]

Of the 61litres, how much had to be trimmed away to make room for seat belts, arms, gear levers etc? Because I usually find one be more efficient with the bag that you actually were - if you have 70 litres to play with you can be less vigilant than if you had 50 litres, but still make the same final seat. Not saying you're wrong though!!

Yes, I remove the bag where it's easy to do so as it doesn't stick to the beads terribly well, but where it's folded into the seat or doesn't want to come away I don't force it.

And it does stay a bit flexible, which is one of the reasons it absorbs energy. You could try reinforcing it with something (but not polyester resin, which eats the polystyrene beads), but make sure not to make it too solid. A layer of carbon fibre on the back? Cardboard? Or just extra layers of tape (my preferred method).

[RobManser]

The seat last year never cured properly, so we never got to find out how much needed to be trimmed. I'm trimming the second attempt today and it's not too much - perhaps a litre in total? The 50L was definitely way too small for me - we ordered one last year and had to send it back.

Thanks very much for the tips.

One thing I do find with these seats is it's very hard to make the seat follow the curve of your back, specifically the lumbar, where it needs to bulge out. The seat I've just made is great everywhere else, but my lower back has a considerable gap behind it. I was wondering about adding a small amount of expanding foam to fill the hole and then taping that on?

[tristancliffe]

If it never cures then that's 99% likely you got the ratio of resin to hardener wrong. Theoretically it could be a bad or old batch of resin, but I've not come across that before (first time for everything though).

It's very easy to miss the lumbar area. I've found you have to put way too much in the middle down there and gradually ease it out, but not by wriggling or rocking your hips - that tends to push beads away from the lumbar. It's insanely difficult, as a seat fitter, to stop pro and amateur drivers from wriggling and rocking because that's what they think they have to do.

Nothing to stop you casting a small two part foam infill for the lumbar, especially if it's quite a thick area of the energy absorbing beads. Or you can build up that area with thin layers of self adhesive foam, which might be easier and nicer.

It's very rare for a seat to be 100% perfect, so if you're happy with it apart from the small of your back then I'd take that as a success.

[RobManser]

Thanks - I've ordered some self adhesive foam and I'll use that for the lumbar area.

Lifting the seat in and out has caused some cracks and bits to fall off where it's thin, but I've taped it back together again so hopefully that's ok.

Thanks for your tips - I hope they're useful to others too.