Right... bear with me whilst I try and explain what I'm trying to do!

The bodywork on my car will be a single piece epoxy resin structure (this includes the twin seat arrangement in the cockpit). I can lift it off the car 'as one' with my garage winch using 4 hook inserts

I want a single-piece tip-to-tail under-tray for my car with protruding front splitter, side skirts and rear diffuser.

Now - I don't want to use ali sheet as I HATE rivets and the hassle they cause for when the car needs stripped back for powder-coating as the years roll by.

My initial thoughts were to get a single piece of mild sheet steel and work from there. Shape the rear diffuser and weld it all on. Gives me a nice one-piece chassis that I can send to the powder-coaters with minimal prep fuss.

Problems... 1) weight.... 2) they don't do single sheets large enough (I need a 2 x 6 metre sheet ).

So, I got to thinking - I'm working with epoxy resins right now. Really quite enjoying it!

Why not go for a 2 x 6 piece of thin marine ply. Shape the diffuser element accordingly and laminate both sides thickly with top Epoxy Resin?

Weld in lugs at regular intervals on the chassis floor members and insert rivnuts in them so I can bolt the under-tray in place?

Got to be lighter than steel and still gives me the 'convenience removal factor' I'm looking for.

Obviously not as strong as thin sheet steel, but marine ply is pretty tough stuff and epoxy resins appear to be the biz for adding rigidity!

Just floating an idea... anyone care to comment?

PS - None of my bodywork is stressed.

quote:

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Originally posted by scootz
PS - None of my bodywork is stressed.

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How about fibreglass and core mat or aluminium honeycomb sandwich? (yum tasty) Then fix using the same method for your ply jobbie.

Do a search on google images and you will see what I mean.

Steve.

[Edited on 18/9/08 by Hammerhead]

cant you weld 3 off 2m x 2m mild steel?

what is it your building? I used ply wood for the Falcons floor, worked very well though I did paint it and then a coat of underseal on the bottom. At 1/2 inch thick it was not that light.

[Edited on 18/9/08 by Mr Whippy]

You can get liteply but I don't know what size sheets it goes up to. This is a ply with a balsa core which is light, stiff (and quite expensive)

Depending upon how thick it is, I would be concerned with stones flicking up... any why bother with the epoxy - it won't make a lot of difference to the stiffness?

dax fit a dished grp floor on some models (assume it will allow for taller drivers)

Hope that helps

Agriv8

Edited to Add - just checked on Dax Price list and its does not apear to be there - I am sure it used to be- Not sure Why.


[Edited on 18/9/08 by Agriv8]

The GTM coupe and libra have GRP monocoques. Use glass and kevlar for your floor in with your epoxy and it should be fine.

I would use a 5mm foam core with an epoxy/kevlar bottom layer and a glass top layer....

Why not have it built in overlapping sections anyway...would make life SO much easier!

What's wrong with a GRP/foam core/GRP sandwich. Boats use it all the time. Light, stiff and quite easy to do. And and make a complex shape, and if you really want to push the boat out go for vacuum infusion.

quote:

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Originally posted by Agriv8
dax fit a dished grp floor on some models (assume it will allow for taller drivers)

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I'm a bit confused, if you are building an ultima spider what do they say to use? I think 6 x 2 ply is nonexistant which means scarfing joints - a bit tricky too. I used ally glued onto marine ply on my last kit car - super strong but quite heavy.

This forum seems to have a completely irrational prejudice against wood for some unknown reason!! - it's fine for boats and planes but apparently not for cars! Personally I can't see a problem with your idea and it has been done before - as mentioned above aluminium honeycomb sandwich panels would probably be ideal in terms of stiffness and weight but going by the prices I got last time I looked into it you'd be looking at about a grand for the materials.

Ply sounds like a damn good idea to me, just be sure to use a good one. If you are going to coat it with epoxy then birch ply would be a good choice. For anything you are going to stand on then the thickness will depend on how far apart the supports are. I would suggest getting some 9mm and experimenting with it.

The advantage I would see over the fancier composite methods is that ply is very easy to work, cut, join etc. It's also very strong, and the cheapness (in this context) may also be welcome.

It may be that some people haven't experienced birch ply and are thinking of the cheap sh1t that they see in B&Q etc.

John

Steve Turner uses ply for the floor on the LMP.
very stiff for it weight...u2u tadltd and ask him scootz. He is based over on the west coast in weegieland

[Edited on 18-9-08 by mangogrooveworkshop]

Cheers for the positive responses guys!

The question was asked what "Ultima Recommends'.

The short answer is: The factory will give you short-shrift if you look at modifying ANY aspect of the car!

No Ultima Kit's are designed with a flat floor or diffuser. Then when you add the fact that I'm bonding a 3-part body-structure to make it one piece and incorporate moulded seats into that single piece bodywork, then you can see that I will get even shorter-shrift from the Factory!

Add into the equation that I'm using an Audi V8 and Audi Gearbox, then it get's worse.... Ultima endorses and sets it up for Chevy V8's and Porsche G50 boxes. They don't like 'change'... and I suppose I can see where they're coming from - they have a fairly strong brand to protect and don't want too many 'mongrels' out there possibly tarnishing the company name.

So, you're probably wondering why I'm doing all this 'weird' stuff. Well the simple answer is that the Spyder was discontinued almost 10 years ago and was replaced with the Can-Am (and from what I can see, it's just bodywork changes and a few minor chassis developments... which I'm incorporating into my build).

There were only ever 50 Spyders sold (probably only a dozen or so still in existence). They are now quite 'unfashionable' in Ultima circles, so when my unfinished kit was advertised for sale (some 8 years after it left the factory ), the bargain price I got it for meant that I could afford to 'fiddle' with it!

Not from a fiscal point of view - I'm skint like most of the rest of us, but from the point of view that I'm creating a frankenstein that's unlikely to ever be sold to an Ultima aficionado at the traditional 'Ultima pemium' because of it's quirkiness.

But then again, do I care? Do I hell. I'm building it for me and me alone!

Mind you - the kit came with a Porsche G50 box which I got very good money for (the Audi box was peanuts by comparison), so I scored there.

Lost out big time though as the (allegedly respected) kit car manufacturer - no I won't name them, but I will say it was NOT Ultima - sold me a "£4k motor" which pumped the price of the kit up a couple of thousand.

Turns out the "£4k motor' was a bag of nails inside - Kit Car Manufacturer man (again - not Ultima) wasn't interested in reaching a fair compromise on the matter, so I sold it on for £200 for spares to a bloke in Manchester.



Hey - ho... that's the world we live in. You win some, you lose some!

Is there any reason you can't rivnut an aluminium floor?

Could you use a tap to create a thread in the chassis and use bolts of some sort?

no photos of this thing then?????????????

Not taken many...

Here's ONE of the engine and box on the day both arrived. Obviously look much different now as I've stripped all the uneccesary bits of the engine.

Here's ANOTHER showing my initial interpretation of what i wanted the interior to look like. Again... this will change!

Yes - the ali / rivet approach is fine, but I have a hatred for drilling rivet holes and then fitting them, and then drilling them out to re-paint the chassis, then fitting them, then... Also, an ali floor wouldn't work with the shape / body-fitting technique I'm visualising.

[Edited on 18/9/08 by scootz]

More I read about QUALITY plywood, the more I like the sound of it!

High strength - easily shaped - can be resin coated and painted - reasonably priced - relatively light!

Now to choose the right supplier!

Marine ply with even a single sheet thickness of epoxied GRP either side can be super strong but a rough finish unless a lot of work is put in.

Russian birch ply, is lovely to work with and super strong, even the thin stuff.

Al


Originally posted by scootz
More I read about QUALITY plywood, the more I like the sound of it!

High strength - easily shaped - can be resin coated and painted - reasonably priced - relatively light!

Now to choose the right supplier!

quote:

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Originally posted by oldtimer
Marine ply with even a single sheet thickness of epoxied GRP either side can be super strong but a rough finish unless a lot of work is put in.

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Have a look at the thread I put on in the tool and techniques section, it would mean you would have to have the bodyshell upside down to achieve what you want but it works like a dream.
http://www.locostbuilders.co.uk/viewthread.php?tid=96845