This post will show you how to build your own DIY roof rack cargo box.
Roof Rack kits are way overpriced. The companies who make them gouge your wallet by selling everything separately and for much more than they need to be. Even on ebay, used prices for rack kits are expensive (doable, but IMHO still expensive), and if one wants to go beyond just the typical roof rack, and add say a cargo box, the initial cost of doing so is almost $700 brand new!
So when my wife and I had our first child (boy, 6 lbs 5 oz. born nov 18th), we quickly realized that we needed more space in our car to carry the usual odds and sods that babies tend to need while out and about. So our dilemma was either to get a larger used car (10k etc.), or to get a rack system (sub 1k) and see how much space it would provide us. We opted to try the cheapest solution first.
I picked up a set of yakima crossbars, 6 lock cores, and Q-towers off craigslist, and purchased the correct Q-clips from rei and another sale off craigslist (to build the base system for my corolla, one needs crossbars, q-towers and q-clips). The total came out to be $190 for all of the above (new would be around $375), still expensive but acceptable. After initial installation and test drive, the next step was to stop the obnoxiously loud wind noise which was created by the crossbars while traveling faster than 35mph. A quick google search turned up that to do so cheaply (meaning not buying the $70 wind fairing), all one had to do was to take a thick nylon bungee cord ($2) and twist it around the bars (car manufacturers use this same principle on their radio antennas to alleviate wind noise as well). This worked beautifully, as all wind noise caused by wind running through the crossbars was eliminated.
After the base rack system was installed and all obnoxious side-effects minimized, it came time to “build” the cargo box which would hold some of the bulky objects one would pack for a weekend getaway. Fortunately, I found a suitable container at work. It was a used Abex pop-up exhibit travel case which was somewhat aerodynamic and made of durable plastic since it was made for shipping and travel. One can pick up similar shipping cases (which do not need to be abex branded) for pretty cheap off ebay, I did a search and found them for about $50-100 with shipping included (search ebay for ‘shipping case’).
I then purchased two 1″ x 1.5″ x 0.125″ T6061-T6 extruded aluminum tubes cut to 36″ long (my front crossbar distance from the rear crossbar is 32″) from onlinemetals.com ($30), and some U-bolt hardware, 2″ bolts, stop-nuts, and large fender washers from lowes ($16). I was pretty impressed that the U-bolts fit the yakima crossbars perfectly and snugly. I then measures and drilled 4 holes in the aluminum tubes to run the U-bolts through, did a test fit on the rack crossbars for fitment, and then proceeded to mount the aluminum tubes onto the cargo box.
I eyeballed the placement of the tubes onto the cargo box, and drilled two more holes for each aluminum tube. I then marked the centerpoint of those holes onto the cargo box and drilled four holes into the cargo box. These four holes would allow me to run the bolts through from the inside of the cargo box through the tubes, and allow them to be securely attached.
After the installation of the bolts, the cargo box needed to be weatherproofed a little. I used some door weather-stripping that i had laying around and lined the lip of the seam where the cover would butt against. After that, the cargo box was finished!
I have since taken a trip to Tahoe in the middle of heavy wind/rain/snow/freezing temperature storms and have yet to have the cargo box fail on me. The four bolts with large fender washers securely hold the box to the aluminum bars. The weather stripping keeps the water and snow out, and the box is aerodynamic enough to keep my gas mileage at 28mpg (without passengers/cargo I get about 30-31 mixed driving. The mpg hit might be because as I was carrying 5 passengers and their cargo as well). The wind noise is very acceptable, and just noticeable at speeds of 75mph.
Overall, for saving some money, this is a project that is well worth it (spent less than $250) . My sister in law even mentioned that she thought it didnt look any worse than commercially built cargo boxes and worked just as well!