Hi folks,
Some of you may have seen a thread I started a little while ago exploring the idea of making my own composite floor as part of a van fitout I’m doing.
Well I went ahead and did it! So I thought I would post some details here in case anyone is interested.
The requirements of the floor included:
[ul]
[li]Waterproof (the van fill be used in all weather conditions, loading and unloading wet equipment)
[/li][li]Durable (while there is nothing particularly worrying about the intended use, who wants to go to all this work in a fitout only to have to replace something in a couple of years time?)
[/li][li]Rotproof
[/li][li]Resistant to oil, fuel & chemicals
[/li][li]Lightweight (this was a secondary goal really, but less weight means higher payload capacity and improved fuel usage)
[/li][li]Single piece (another secondary goal, for ease of install and removal)
[/li][/ul]
The van previously had been lined with plywood, but it had already suffered some water damage from incidental usage. It was obvious that ply was a poor choice given my requirements.
There is a German company that makes composite flooring specifically for vans, but they have no distributor in Australia. For all the time and cost involved I would have preferred to buy a pre-made floor, but when nothing is available you’ve just gotta do it yourself! 
I investigated the possibility of using pre-glassed structural panels, but I thought I could do it cheaper myself. The other problem was that the pre-glassed panels had gelcoat on one side, which I didn’t think would be good for use as a floor. I also wasn’t sure if I could join all the panels securely enough, as they only come in 2400 x 1200mm sheets.
After some thought I decided on the following layup:
[ul]
[li]Epoxy surface coat with anti-slip additive
[/li][li]450gsm dual-bias woven fibreglass
[/li][li]300gsm dual-bias woven fibreglass
[/li][li]12mm structural foam core
[/li][li]300gsm dual-bias woven fibreglass
[/li][li]450gsm dual-bias woven fibreglass
[/li][/ul]
The job was completed with polyester resin due to cost considerations, and I didn’t see any reason not to use it. I would estimate that I went through 22kg of resin approximately - a fair bit more than I calculated (shows what I know) so it was good I had a 25kg drum to start with.
I had planned to use nylon spacers under the tie down points so as not to compress the floor panel, but thankfully a salesman at the plastic supplier asked what I was going to be doing and recommended that I use PVC as nylon and other plastics don’t bond well. So I cut down some pieces of 50mm PVC rod.
Onto the layup process:
Before I started anything I trimmed the foam to size and joined them with Sika 227 (just because I had some handy). I didn’t go overboard, I just wanted enough to help keep the foam in place. Once that was done I mixed up some polyester resin and talc to fill the gaps between the sheets, and also to level out a height difference between the foam (you can see this as a brown looking area in the photos below).
I cutout one section that wasn’t going to be needed in order to try and save some resin, but in hindsight I would leave this next time to give some more flexibility during the final trim.
First layer of 300gsm laminated.
Composite Floor by mugget, on Flickr
The next layer of 450gsm ready to go.
Composite Floor by mugget, on Flickr
You’ll notice that I left the join for both the 300 and 450gsm layers on the same side. This is because I wanted to keep the other side of the floor as level as possible as I’ll be installing a workbench in that area. (The underside had the fibreglass overlap spaced evenly, shown in the below pictures. Mainly so as not to introduce too much of a thickness difference/high point on the underside.)
Once the first side was done I simply flipped it over and laminated the 2nd side. No need for moulds or anything fancy and I think it came out quite well.
I had made a floor template using corflute (corrugated plastic sheet) and traced this onto the completed floor.
Composite Floor by mugget, on Flickr
Next up was the initial trimming. A jigsaw with a plastic/wood blade made easy work of this step.
Composite Floor by mugget, on Flickr
There was a fair bit of work required installing the floor in the van and making adjustments with more trimming, but now it fits just like a bought one. 
The process to align the tie down bolt holes for the PVC spacers was quite involved so I won’t go into that here. Just another tedious step with lots of measuring and double-checking.
Getting closer to completion I attached aluminium step trim using a structural marine adhesive. I still have to back fill the underside between the curved edge of the trim and the edge of the floor panel. I’ve never used an adhesive in this kind of application before so it’s a bit of a leap of faith. Time will tell (that my prep work was sufficient!)
One thing that had been worrying me was the final step to add an epoxy surface coat. I knew that I needed some kind of additive otherwise I would just end up with a nice glossy, slippery and dangerous surface! The local composite shop had some e-spheres that they gave me as a sample since I didn’t need too many. They were the largest size they had, so I mixed up a trial batch of resin, graphite powder (to give the darker appearance) and the e-spheres. It worked well so I went ahead with the actual floor.
That didn’t seem to go so well. I knew that the e-spheres would float to the surface in the mixing cup, which was not a problem. But I wound up putting the mixture on the floor, then scraping the excess off. Unfortunately it seemed like I removed the e-spheres with the excess mix. In the end I sprinkled them directly onto the surface, which is why there’s a random pattern all over the surface of the floor. It also didn’t help that this was all done outside and it was fairly windy.
Composite Floor by mugget, on Flickr
I’m still happy with how it came out. I’ll bet it’s hardly noticeable once installed in the van. When was the last time you looked at a van floor to check that it had a uniform surface? 
To finish things off, this afternoon I added some 5mm foam to the underside. The idea behind this is just to minimise any possible vibration between the floor panel and the actual van floor. The floor will be solidly bolted in place via the tie down points, but something made me think that it was a good idea to avoid a direct interface between two hard surfaces.
Composite Floor by mugget, on Flickr
I don’t have a tally of how many hours went into this, but it was a fair bit. Especially because it was the first time I’ve done anything remotely like this so I was just discovering things and learning as I went. I would estimate 5-6 hours for setup and lamination of each side (to give an idea). I did have some help, but it was still just two people working with brushes! I only mixed 1L of resin at a time so I could use it all, and it still seemed like I was working quite fast. I suppose it’s not an easy thing to wet out a fabric with the minimum of resin… as the job went on I started using more resin to move things along a bit quicker.
I haven’t worked out the total cost yet either (a bit scared to look at that actually! :blink: )
The final specs look like this:
size: 4,300 x 1780mm
weight: 41kg
It’s pretty easy for two people to fit into the van, not too heavy to carry which is good.
As a comparison, if the same area was lined with 12mm ply it would weigh about 56kg (minus a few kg for the cutout areas).