Roof Chops, Proportions and Cockpit Sizes?

[RobinJI]

Hi guys, as some of you may be aware, I'm building a heavily modified Mini Clubman Estate. Well I say building, I'm on a break from it at the moment due to being several counties away at uni, but I've only got a few months left now, and I'm itching to get back and get on with it, so I've been going through plans and thinking about things more and more as the time to get on with it again approach's. However, there's something I've been unsure about since starting the build, which I'd really appreciate peoples input on.

I've taken a large amount of height out of the body, in the form of the new floor being mounted 90mm higher than the original one, allowing the car to sit 215mm lower than standard. This along with the massively raised arch positions is making me wonder about the cars proportions. I'm worried it might end up looking a little greenhouse like, with a high roof in relation to the waistline, which is making me think about a subtle roof chop.

I'd only be looking at removing ~40mm at the most, which would be found from the screen surround rather than the glass, while the side windows would be shortened the appropriate amount. I'd hope this will bring the proportions back in line a little looks wise, and then there's the bonus that I'm obsessed with low roof lines, and this would result in the cars overall height, from the ground to the top of the roof being just 1095mm!

Proportionally what do you guys think? These CAD models are far from perfect in terms of the bodywork, but they should give a general idea:

Without the roof chop:



With the roof chop:



And a mock up of it in real life:



Now ideally I think I'd like to do this, but there's one thing holding me back; Space in the cockpit. This car's being built to be used hard, and as such needs space for me to fit inside it with a helmet on. The usual solution in very low slung cars is to lye the seat right back, but I'm a bit limited in that respect, I need space for the engine in the back, and the fuel tank in the front, which leaves me with a total cockpit length of 1345mm and with the roof chop, a cockpit height of 965mm (1005 without).

I'm wondering if anyone out there with cars with a very low slung driving position could measure the cockpit space for me? From the furthest back part of the seat, to the furthest the pedals depress, and from the seat mounts, up to the roof above your head, even better if you've got a bucket seat, but a rough guess of how thick the backrest is would be ideal too, along with how tall you are and if you actually find the position comfy or not.


Thanks for any input guys, it's something I need to work out soon, as the roll cage is one of the next bits that needs doing when I get back to it, and I can't do it until I've decided the final roof height.

Cheers, Robin

[pantera2075]

This looks very obvious to me for a fix - I'm not trying to teach you to suck eggs:

You need more legroom - modify the bulkhead and pedal box to push them forwards.

[RobinJI]

Jan 18, 2012 22:09:51 GMT pantera2075 said:

This looks very obvious to me for a fix - I'm not trying to teach you to suck eggs:

You need more legroom - modify the bulkhead and pedal box to push them forwards.

Unfortunately there's not really anywhere to push the bulkhead forwards to. In the plans it's already further forwards and much more spacious than the original bulkhead, and the only way to gain more legroom would be to use a taller fuel tank, which is bad for the CofG, as well as giving very little room for the front suspension and the cooling systems. It's very much the last resort option at the moment.

You can see the lack of space front and rear here (the space in front of the fuel tank will contain the rad):

[speedy88]

As far as looks go, it doesn't look terrible with the standard roof height. With the lower roof it does sure look a little meaner and I can see what you're getting at. But I think you're probably over thinking it a bit, from eye level nobody would probably be able to tell the difference anyway.

But saying that the proportions are much better with the chop. I guess you should weigh up simply if it's worth it.

[ettorebugatti]

Cockpit length sounds good, height is indeed an issue
You could tilt the seat.

Take also in consideration your vision angles .

[RobinJI]

Thanks Mark, I think you're right about it not being obviously noticeable to someone looking at it, but I don't think that makes it any less important. I'm not really worried about doing the work, it's something I'd find enjoyable so I know I'd plow on with it quickly out of enthusiasm, and I'd find it interesting to do. The roof chop also reduces the frontal area, and rakes the screen back slightly, which is all good for aero.

But it all depends on if I'll fit, if people really don't think it'll make a difference to the looks, and it's going to make actually fitting in the car a pain in the backside, then I may well save my self the effort and leave it as is.

Jan 18, 2012 22:37:23 GMT ettorebugatti said:

You could tilt the seat.

That's the plan, but I'm trying to work out how far I can tilt it before cockpit length becomes an issue.

I'm not so worried about viewing angle, minis have nice big windows, even loosing 40mm it'll still be fine, and even with the seat bolted to the floor I'm actually sat no lower than a standard mini thanks to the raised floor.

Thanks for the input guys, keep it coming.

[sparkyt]

Are you going racing ? Some levels of motor sport won't let you cut the roof ..But if that's not a problem chop away mate I think it looks cool ..

[Mystery Machine]

I think the roofchop is an awesome idea. I've always loved the look of the car but the proportions above the waistline are a little awkward and slightly cumbersome. Lowering the roof will give it a much greater sense of proportion whilst exaggerating the wide stance you've already got.

Three suggestions from me which, if all used together, will probably get you back to optimum headroom with the least impact in any one area.

I'll got into more detail when I'm not on my phone, but I'd go with a bit of Richards suggestion of tilting the seat along with a slight floor notch at the back half of the seat base combined with a subtle Gurney hump in the roof should get you the headroom you need without too much compromise in any one area?

[bigkris]

Id say go for it aswell. Might sound silly but have you remembered that by the time you wear a crash helmet you will need even more room? Made that mistake myself!! lol

[Mystery Machine]

Jan 19, 2012 8:51:37 GMT bigkris said:

Might sound silly but have you remembered that by the time you wear a crash helmet you will need even more room? Made that mistake myself!! lol

Do pay attention at the back there Kris:

Jan 18, 2012 21:56:08 GMT RobinJI said:

....and as such needs space for me to fit inside it with a helmet on.

;D

[MrSpeedy]

Proportianally, it looks a lot better with the subtle roof chop.

It's not over the top which a lot of them can be, but it brings everything back into line.

Got a real 'Sillouette' vibe going on, and I'm liking it

[rob0r]

If it was me, I wouldn't bother. It just seems to be making things more difficult for aesthetic gains? It's not only the challenge of shortening the body height but then to still fit in it afterwards. I don't think it looks that out of proportion as it is, and either way the car is going to be gob smacking .

[markbognor]

Looks good full height to me - I actually like that it is a little out of proportion - just like a 70's siluette touring car.

[cobblers]

Keep it full height - It'll be less work, more practical and maintain the slightly strange but awesome look that those racing imps had.

[stealthstylz]

I prefer it with the chop, looks a bit like a Clubman version of a Minus.

Matt

[ben711200]

Jan 18, 2012 23:14:44 GMT sparkyt said:

Are you going racing ? Some levels of motor sport won't let you cut the roof ..But if that's not a problem chop away mate I think it looks cool ..

I'm not familiar with the MSA side of things, but legally speaking, as Robin is going to be BIVAing this, it wouldn't be a roofchop, it would be 'factory'

[RobinJI]

I know what people mean about the silhouette racer look, and I do quite like that my self, I guess I'm trying to decide what sort of style to go for visually, as I've been mostly concerned with the performance up to this point. I've just played with the roof chopped model a bit more and lengthened the rear windows a bit, so they're only shortened by 30mm instead of 40, and I think it helps the rear end quite a bit, and would help with the far from ideal rear viability a little.

I'm not really concerned about the extra work, like I've said, I'll enjoy doing it, and I'd like to flush mount the front screen anyway, so the A-pillars and screen surround would be getting chopped up a lot to do that anyway. The front doors are modified fiberglass ones, so it's no real effort to modify the hoops, in fact I should be able to get away with just mounting a new set of hoops lower in them. The rear doors will hopefully be carbon (budget depending) but if not, they'll be fiberglass, and still need making, it'll be easy enough to shorten them while I'm at it. So the only real additional work will be the B and C pillars, which are very simply shaped. The idea would be to rake the screen back and leave the roof standard size. I may need to slant the B and C pillars inwards slightly though, but that's easy enough. None of the bodywork is even slightly structural beyond keeping the rain out by the way.

I think, as people may have guessed, I'm siding with chopping the roof, but it does still rely on being able to actually fit in the thing! Any measurements of low slung cars people can get would be great

Trevor, I'm not planning on entering anything as a mini, I'm basically building it as a road legal race car, for the simple reason that I feel like it, I want a silly mini, and I enjoy building things. It'll also hopefully act as a rolling CV when I come to find work in the future, so the more modified it is, the more it shows off what I can do . It will basically be used for track days, and whatever racing events will let it enter. As Ben says, it wont be registered as a Mini, and I don't plan on trying to enter it in any events as such.

Bruce, I'll be interested to here your ideas in full sometime. A floor notch isn't really possible, as with the completely flat floor, your would become the lowest point of the car, not great for areo, and really not pleasant in the event of a sudden, unintentional grounding out at speed ! That said, I could gain some height by side mounting the seat between the box section making the floor structure, so the seats literally on the floor, this would gain me an inch, which is definitely worth while. The Gurney hump in the roof I'm not so keen on from a looks point of view, but the bigger issue is that I'm planning on fitting a carbon roof, which I don't own the mould for, so I couldn't modify it without messing up the weave of the carbon, and I cant go chopping about a mould that doesn't belong to me

Kris, Yeah, it's the helmet that's going to be the problem, I reckon I could fit in just fine without one, but with one I think it'll be tight, which is why I'm after measurements to confirm if it's possible or not.

Thanks guys, lots of good input so far, and it's good to hear that some people like it without the chop in case I can't do it.

[alolympic]

The roof chop looks better in profile definitely. You only have to look at a Mini Sprite to see how a small thing can make such a difference. I would say it's probably a lot of work for something that has no real engineering advantage.
Would I do it? hell yeah
You want to and that is in reason enough, and everytime you look at the car, you will know that you went the extra mile.

I'm sure you have gone down the route of fitting the thinnest bucket seat, that will mount direct to the floor? On the 2nd CAD Mock up, that looks like a fairly chunky seat. A Tillet type seat would give you the most room possible.
Sorry I can't help with any measurements. Maybe if you can get hold of an owner of a Lotus Europa, that is a fairly compromising cabin!
Nice CAD Drawings by the way!!

[barty]

I'm prob being daft but what if you do the chop, but make the roof sides slightly deeper, i know you said you don't own the moulds and i have no idea what else is involved but from the side the whole effect would give the appearance you were looking for. I'm not saying a great big slab side to the roof maybe just half an inch and if you use a really low slug seat you may gain maybe an inch or so, thus gaining maybe a inch and a half or two. Just a thought and I'm getting ready to be blasted for this idea lol

[ettorebugatti]

Marcos GT and GT40 have the most laidback sitting position.

Now some inspiration: