Hello fellow Mini Cooper owners! I finally completed a project today for my new Mini Cooper S Hardtop that may be of interest to you. I am fortunate to have finally replaced the Mini Cooper Clubman that I lost in a major fire some time back with this beautiful little machine.
This is the 2014 Mini Cooper S Hardtop. I absolutely love it but found one item lacking in the car that I had in my original Mini Cooper Clubman. In the Clubman when you folded the rear seats down you ended up with a completely flat deck from the rear bumper all the way to the front seats. Not the case in this new Mini.
This is what the rear of the new Mini looks like once you fold the seats down. I like all of the storage space but don't like the idea that there is no flat deck for hauling larger items. So I immediately went online to find a solution to this problem.
Here are a couple photos of the storage box that I could get from Mini. It looks great and does exactly what I want but I felt the cost of $260 was way more than I wanted to pay. So this project was born before I even took delivery of my new Mini and I knew I could do it for a lot less.
I did some preliminary design work on the storage box before the Mini arrived by taking measurements at my local dealership. These guys are great by the way and I am sure they will be very interested in this project as well.
These last two images were created using Inventor CAD software and then the computer files were brought into Blender 3D to get these great images. I wanted the computer model to be as close to the real thing as I could get so I could see where the project was heading. One thing that stood out in my mind first off was the top deck of the box once it was closed. It had to be strong enough to hold a good amount of weight. Not like I am going to haul concrete blocks in my Mini but I still wanted it to be solid. I also wanted the deck to be able to hold up over time. In these images I planned on painting the top deck. This I found out would not work well as it would easily be scuffed just by hauling groceries for my local market. So this was another issue that needed to be addressed.
Once my Mini was finally in my hands I was able to get accurate measurements and work out a plan of action to build the deck storage box. I started by creating the box out of foam core and packaging tape. This was an inexpensive, quick, easy way to create the box and make sure it fit into the car first time I tried it. Already at this point it looked to be a perfect fit. Another thing that needed to be addressed in the build was a vent system that is at the tail end of the car. I did some research as to why this vent is there in the first place. It allows air to escape out of the car when you are running the air conditioner. Like putting air into a balloon the air needs to escape to allow fresh air to continue to come in. I did not want to block these vents so this had to be considered while designing and building the storage box as well.
The deck storage box lids were made of Styrofoam then cut to size and shape using my CNC machine and it was quite a process to get both doors laid out properly for the project. Here I put the storage box back into the car with the seats up to check the clearances that I needed for the deck lids to open properly. Lots of checking and rechecking needed to be done to get everything to fit properly.
To work out the deck of the box I designed two lids that would be made of foam and fiber glass. These lids would be attached to an additional strip of foam that had hard mounts inserted into the pieces where hinges would be added later on.
The wooden blocks were bonded to the foam using an epoxy micro-balloon mixture to form a putty mixture and then pressed into place between the foam and the blocks.
The stainless steel hinges were then mounted to the wooden blocks. The doors and rear plate of the storage box deck were then aligned properly.
With the eighth inch thick foam core box already built at a cost of only $5.00 I was so pleased with the look that I decided that it would be simpler just to go ahead and fiber glass the box rather than make a new one out of thicker Styrofoam. In this photo all of the white that you see on the black faces of the box are what happened when I needed to remove the packaging tape that held the box together. The tape could not remain on the box as the fiber glass would not stick to it and when I removed the tape it peeled the black paper off of the foam core. This would not be a problem after the fiber glassing was completed as the box would be painted later on. I then puttied all of the inner joints of the box with fiber glass resin and micro-balloons to make a putty that would bond the box together permanently. Once the inside had cured I then repeated the process on the outside of the box. This made the box very strong and lightweight which is always a plus. I also removed the deck lids from the back mounting strip so this part could be fiber glassed into place on the storage box as well.
While the storage box was curing I went to work on the two deck lids. In the photo above you can see the parts that needed to be made using my 3D printer to mount aluminum tubing for the already fiber glassed deck lids. The larger oval shaped part that you see is the vent cover to allow air to flow to the rear vents in the Mini that I spoke about earlier. This will allow the air to flow back to these vents and not restrict air flow.
I puttied the vents in place like so many other parts on this project and then taped it off on the inside so that I could paint it black.
I masked of around the vent so that it would also be sprayed with black spray paint. The reason for the gap around the vent and the tape I will explain later in this post.
Here the vent has been sprayed and the rest of the deck lid was covered with paper to keep the paint where I wanted it to end up.
Earlier in this post I said that I had to figure out a way to give the deck of the storage box a protective cover rather than just painting it. I came across a company online named Sim Carbon that makes a vinyl wrap for cars that looks like carbon fiber. This was perfect. The price for the material I needed came to $42.50 delivered to my door. This gave me a piece of material that was four feet by five feet in size which was plenty to do this project and enough left over for a couple smaller projects. I then proceeded to wrap both deck lids with this material. It has a sticky back that you press down on to any surface using a squeegee. It took a little practice to get it to lay down the way I wanted but as you can see it turned out pretty well.
Here's a close up look of the air vent that I had puttied into place earlier in the project and now has been wrapped in carbon fiber vinyl. I completely covered over the air vent and then used an Exacto knife to trim around the vent. This gave me a nice clean look and the black paint I had sprayed earlier now matched up nicely with the carbon fiber.
The aluminum tubing used in this project is 1/2 inch in diameter that I bought at my local Menards home store. I took the tubing and polished it to a nice chrome like finish using a fine grade steel wool. The photo above show the difference of the polished piece (the one on the bottom) compared to the unpolished pieces above it.
Inside the storage box I mounted to 3D printed pieces to support the prop rods that would hold the deck lids open if I needed to. These were as usual bonded into place with the epoxy putty mixture.
Once all of the fiber glassing work had been completed it was time to take the project outside and prime the storage box. I was lucky to have a nice warm day so this was a quick and easy job.
After the primer had dried I then laid down a couple coats of gloss black paint. I turned the box upside down first and painted it. After it had dried I then rolled it right side up to finish the painting. Very little work needed to be done to the interior of the box as it was very smooth.
Here is a good shot of the Mini Cooper deck storage box in my kitchen. The aluminum tubing is held in place with end caps that have internal mounting nuts. Machine screws come through the underside of the deck into these nuts and hold everything in place. With the mounts being made this way there is no hardware showing when the deck lids are closed. Gives it a very clean look over all. The circular ring in the top of the deck lids are finger holes to help open up the storage box lids when it is placed in the Mini Cooper.
Here is a shot of one of the small prop rods for the deck lids. This is folded away when not it use and can be easily unfolded when needed. The prop rod has a plastic outer surface with a steel inner shaft to give it strength. The shaft is nothing more than threaded rod that is screwed into the upper 3D printed mount and a white plastic tip on the end. Makes for an easy assembly and the look is perfect.
Here is the finished deck cargo box installed into my Mini Cooper. It turned out very well I think. The look and fit in the car is exactly what I wanted. To finish off the inside of the storage box I laid in a foam piece in the bottom of both sections of the box to keep items from rattling around while I was driving. This material is normally used in tool boxes and was perfect for this project as well.
The plus side to all of this is the total cost to make the storage box was only around $100 compared to $260 that the dealership had wanted to order the factory box. Quite a savings to say the least and as usual to tell someone that I designed and built this great looking cargo box myself is always priceless. Enjoy the photos.