Building your own custom full size roof rack?

[Erick Lihme]

I'm going to try to avoid a roof rack. Picked up an aluminum basket which slides into the receiver at Harbor Freight. We've seen these everywhere made of steel and which are nearly twice the size in width. The Aluminum basket type is much lighter and will hold a large strong plastic trunk and one 5 gal jerry can. Both were about $50.00 bucks.

The 2" tubing will be cut and welded and bolted so that the basket is raised to improve the approach or egress angle to that of the truck without the basket.
With the truck removed, and basket in place, the tailgate can then be let down, accessing the gear in the drawer beneath the platform. With the trunk in place, the shell can still be climb into easily for the night.

The tailgate down, trunk on the ground, or the empty basket provide flat surfaces serving as tables and chairs or whatever...The basket can also be slid into the front receiver....

Extra weight in the rear actually helps balance the heavy front winch bumper, it has easy access and no wind resistance. Of course one will have to be careful with backing and avoid trees. It should make good storage for a light weight kitchen.

Hopefully this thing won't fall apart on the trail.....it shouldn't, but it is untested.

Pat. pending...

 

[LaOutbackTrail]

Hello Andre,
Here are some of my ideas. The Yakima bars are great. I would keep them and incorporate an out hoop that gets welded to the yakima bars. Here is a photograph of my Jeep rack. I love the low profile of this rack. The cross bars are Yakima sized tubing(1 1/8 odd size). The outer rack is 1 1/4". The reason the outer is 1 1/4" is most fab shops do not have the odd size that Yakima requires. So I simple had them weld in some cross bars that meet Yakimas specs. With the Yakima I am then able to connect just about anything I would every want on top of this rack. I have used kayak, mtn. bike attachments and a Thule space case. I also use the Yakima quick clips to attach the aluminum panel on top. I would then skin the rack with a giant piece of aluminum just like I did. In Arizona this allowed me to run my AC on a #2 setting and because I have two roofs the interior would stay a lot cooler. I would say forget about the upper bars. Why do you need them. Anything you are going to put up there needs to be secured anyway. Just make some attachment points on the aluminum or better yet just run your strap under the aluminum and around the outer bar. Ok here are some photographs. Let me know if I need to explain any of my comments.

I'm brainstorming how I would do something like this on my Xterra.

I'm thinking a frame work similar to the painting below. (you'll get the idea). Then mount the plate aluminum to that. Of course, remove the stock cross bars. Maybe even put a hinge over the little compartment up front (behind the lights) to keep stuff under. Could remove the aluminum and use the bars for a kayak/bike etc.

I wonder if the blue bars would even be necessary? I would just need to know what thickness to get the aluminum so that it is sturdy and still lightweight and how far apart the crossbars should be to keep from denting the aluminum.

Mounting the spring attatchment points and having Ubolts for the shovel, axe, highlift on that.... clean and neat I would think.....

Ideas?

 

[Gear]

Pm sent

 

[ntsqd]

Found some pics, perhaps more helpful than a written description?

Late in the build, can see the mitered corner at the right:

Shortly b4 the rust monster claimed the truck:

 

[Grim Reaper]

I thought this was an interesting post in a different thread and related to this thread as well.

I'm far from being an Aerodynamicist, but I notice that a lot of people put their aero concerns on the entry & ignore the exit. I think this is bass-ackwards. The classic aero study case is a falling drop of water. The entry shape has the least surface area possible while the exit is 'soft & gentle.'

I had a '66 Econoline extended body van that I used to flat tow the dune buggy with. About as much of a aerodynamic brick as you could ask for. It got ~10 MPG whether I was towing or not. Sometimes, like in a headwind, it got better mileage towing than it did not towing. After some thot on that I concluded that one possible reason is that the dune buggy (as ugly aerodynamically as it was) "filled in the void" behind the van. It effectively made the van more aerodynamic.
Ever drafted a box trailer big rig? (They don't like it, so I'm not suggesting it.) When you get close enough you have to nearly take your foot of the throttle. That's how much vacuum they're pulling down the road.

Being a Suburban owner and K5 Owner like ntsqd this got me thinking this morning.

I have long known that GM made their trucks teardrop shaped. The highest point is the B-pillar. It tapers down from there. If you look at the last picture ntsqd posted of his burb you can see this. It always made me laugh how so many people thought that their K5 and Burban had a sagging rear on CK5.com. I would look at the pictures and see that the rocker was dead level. It was an optical allusion. The truck was MADE that way for better aerodynamics for the reasons ntsqd posted. Pisses me off sometimes because the floor to ceiling height on a Suburban back end is actually less then on a K5 then even worse if you have dual AC like my burb.

Anyway back to the point with the racks I think ntsqd is right and if you are trying to make a roof rack that is clean (as a rack can be) that you need to look at the whole package. As with a pickup truck it is better to have the tail gate closed because the air will form a bubble in the bed and clean up the air flow coming off the back of the cab. It effectively makes the aerodynamic signature a Tear drop shape from the side.

If you relate that to the rack as ntsqd did that makes some interesting thoughts for how you can make an improvement. The Xtera set up is pretty clean air flow wise when you think about it. The basket in the low spot above the front doors with the fairing creates a bubble over the aerodynamicly dirty basket. The shape of the tube is pretty clean aerodynamically in the rear when no cargo is in it so the roof comes back into play and you get that Tear Drop shape to the airflow.

Where we get into trouble with our roof racks is the floor. A solid floor leaves a rough exit on the rear. It is rough because it can pull the air from the sides and that creates turbulence.

Knowing this then the ideal setup unloaded up would be that you would have the front fairing and side skirts. Once you cut off the airflow from the sides a bubble will form and even without any sort of airdynic change in the rear it will form a air bubble and improve the flow of the back of the rack. Even my fibergrate floor will have improvement because the front fairing will kick the flow up at the front and get the bubble going and stall the airflow through the grating.

I think moving the rack forward some will also help. The reason being is you wont add to the overall height from ground to to rack deck at the very end of the vehicle creating more vacuum on the rear as was pointed out above. It will be lower to the natural roof line. It will allow the airflow to drop off the back of the rack and hit some of the roof and get back into the Aerodynamics the manufacture built into the vehicle body work. A fairing on the rear is not so practical because you would have to load over it but if you get it off the very end you keep the bubble going.


Down side is moving the rack forward will make loading more difficult. I know I stand on my tail gate to load the rack on my burb and that was the plan on the 4Runner as well so it is a trade off of how far you move it forward. 6-10 inches may make a HUGE difference.


Thoughts?

 

[Erick Lihme]

Agree we should become more aware of the aerodynamics. Your post prompted me to spend 30 min. googling around for solutions. After following how one fellow here improved his mpg 4+ gallons, mostly by removing his rack and doing a tire change, there is obviously a great deal to be gained. Not only did he improve the mpg, but likely his performance at hwy speeds as well as the load on the drive train. Improving mileage is certainly important on a rig which is also a daily driver, yet traveling to and from trail can be more affordable even with a dedicated rig.

Engineering is a series of compromises. I hit a deer the other night, the massive rack on the front did not budge. The added 150lbs on the front paid for itself, and I expect to hit many more deer. Fortunately the rack does not reduce mpg when cruising. It does decrease acceleration. It is also designed to be removed quickly with (6) #8 1/2' bolts, leaving the stock bumper in place and brackets for the winch. This set up gives me the option to easily reduce weight for cross county travel. Thoughtful design can add capability.

The inverse can also be true. Even if a roof rack weighs more as material is added to the front and sides, the improved aerodynamics can be worth while.
Having the ability to remove the roof rack easily can be another advantage if the vehicle is a daily driver.
Designing a roof rack including a few principles you've mentioned might save one 1-2 mpg offsetting the drag of those MT's, and adding extra umf for passing, or the ability to carry more weight in the bed returning the center of gravity lower to balance a roof rack of which any design disturbs.

The 'cool' factor shouldn't be underestimated, however, 'smart' is 'cool' too! Checking out a few sites one can glean a few ideas for a 'smart' roof rack. I'd consider at least an sloped front faring extending to the top of the shell cutting off the air under the rack, and built in road lights if needed (think Plexiglas). Clean sides front and rear to create a bubble which the air stream would see as a dead space, very much like the truck bed itself. Those fancy tear drop enclosed carrier things seen everywhere just might pay for themselves.

I don't have a roof rack at the moment, instead I'll try out rack in the back much like seen on jeeps. If someone comes up with an appealing roof roack design however, I just might steal it.

http://www.evworld.com/article.cfm?storyid=870
http://www.nrc-cnrc.gc.ca/highlights/2007/0705uplands_e.html
http://www.gassavers.org/showthread.php?p=51852

 

[dieselcruiserhead]

Cool, nice to be gone a few days and see so many killer comments..

I ended up welding the second rack to the rack of Brown Sugar (our '77 Ford camper) after starting this thread, so the good news is that I'll actually be starting from scratch again here.. Thanks again guys for all the killer comments...

Good call about the conduit too, I actually messed around with it last time a little and was worried it might be too thin, but I think its a good idea and I'll definitely start messing around with it!

Cheers,

 

[dieselcruiserhead]

Here's a neat looking one, in my opinion...
http://forum.ih8mud.com/showthread.php?t=158011

 

[akraven]

I just finished up one on my Rover from conduit. My other one on a Landcruise was from 1" square tubing. Once I figured out the rations for measureing the bends with the conduit bender it wasn't that hard. Good luck. akraven