DIY Prinsu Top Rack Made on Wood Router

I recently stumbled upon a thread where members were making their own Prinsu style top-rack for their topper out of aluminum extrusions and aluminum bar stock.

https://www.tacomaworld.com/threads/diy-prinsu-style-shell-rack.521186/

I thought this was a great idea since I felt that the $700 price tag of a Prinsu seemed steep for such a simple design. After watching the thread for a while, I started to realize that I wanted something a little more detailed looking then just the standard 3” aluminum bar for the side plates. There were a few members having their more detailed design cut by other companies, but the price of the cut side plates and shipping to me defeated the purpose of not buying a Prinsu in the first place. I had seen on YouTube people cutting aluminum using a standard wood router so I thought that might be a possibility. After seeing that @C0d3M0nk3y was able to make some similar side plates using a template that he 3D printed I figured I would give it a shot. My biggest hurdle was not having a 3D printer so I was forced to make my template by hand.


To start I designed the basic profile I was looking for in Sketchup. The Prinsu rack is only 65” long and other than the two ends, it is only 2” tall. When measuring my SnugTop Rebel 65” felt a little too short for my long bed. I elected to go with 68” length with 3” tall tie down points so the rack would appear to sit a little closer to the top.



After I was happy with a design, I printed a to-scale copy of the end profile and tie down profile. I then used some contact cement to adhere the paper to some scrap MDF wood and cut out both shapes on a band saw. You could do this with a jig saw but the band saw made quick work of it. A little fine sanding and the templates were ready to go.




The plan was to use the cut out profile as a template to duplicate the tie down profile multiple times so that each one was the exact same for my final template. I ripped down a few pieces of MDF to be 3” wide, layout out my shapes per my design, and traced them onto the 3” MDF scraps. I didn’t have a scrap long enough for the entire rack, so I used two scraps screwed together to construct my final template. I then used the band saw again to rough cut the shape, leaving about an 1/8” for the router to cut clean. This makes it a lot easier on the router. After the rough cuts, I attached the profile template to the rough cut MDF with some screws and used a flush trim bit to cut the MDF to shape. If you aren’t familiar with a flush trim router bit, it has a bearing that allows you to cut the exact shape of a template. I repeated this process for each tie down and the two ends. The result was the full 68” profile of the rack.





Now that I had a template for the profile of the side plates, the nest step was to transfer this to aluminum. I went to a local metal yard and picked up some 3/16”x3” 6061 Bar stock for around $35. Following a similar process as making the template, I covered the aluminum in masking tape, clamped the full size MDF template on top, and traced out the profile.



Rough cutting the aluminum was by far the worst part of this project. I used a jig saw with a fine-tooth blade and plenty of WD40 to roughly cut out the shape, once again leaving about 1/8”-1/16” of material for the router to cut. This step is messy and slow but very necessary to reduce the amount of material the router must cut.




After rough cutting one of the pieces of aluminum, I attached it to the MDF template using some counter sunk screws. I located the screws in places I knew would be cut out for the tie downs and cross bars later.



Once the template is attached, its time for the fun part. Using the same flush trim router bit, I slowly fed the aluminum in the opposite direction the bit is spinning. I found it easiest to take off very small amounts (1/32”) with each pass. Eventually making the last clean pass riding the bearing along the template. I noticed that if I spray a little WD40 on the surface before each pass, the cut was slightly cleaner. I did burn up one bearing for the bit so make sure to hit the bearing with some WD40 periodically to cool it down and lubricate it. Good thing the cheap Amazon bit set I bought came with 4!



I was pretty impressed with how clean the cuts ended up being on the router!



Here you can see one of the side plate profiles cut next to the uncut aluminum bar stock.



Now that one of the side plates is cut, I wanted the second to be the exact same profile. So, in the same fashion, I covered the un-cut aluminum in masking tape, traced the shape of the cut profile, and rough cut the aluminum with the jig saw and WD40. Like I said before, this part sucks. After the second aluminum plate had been rough cut, I attached the first side plate that was already cut on the router using some counter sunk machine screws to be the template. Here you can see the rough-cut aluminum under the nicely cut side plate ready to be cut on the router.



After the second side plate had been cut on the router, I was ready to start cutting the “slots” that the extruded cross bars will mount to. The proved to be a little more difficult than I had anticipated. The original way I planned to cut these did not work at all. Thankfully I did a practice cut on a scrap piece of aluminum because it did not go well. I ended up purchasing a ¼” plunge router bit. This bit, unlike the flush trim bit, has a cutting surface on the top and is designed to be plunged into the material similar to a standard drill bit. I set up a fence on my DIY router table so that the slots would cut nice and straight. I screwed in a few stops so that the cut would start and stop where I wanted and so that it could be repeated over and over consistently. I used the scrap MDF to dial in the jig and used different sized washers on the stops to fine tune the start and stop points. Once I had it cutting where I wanted, I set the router to only cut 1/32” and then ran the aluminum through in each location. On the next pass I raised it to cut another 1/32” and so forth until it cut all the way through. I did this same process but with a different set of stops for the longer slots. Here you can see the plunge bit poking through the aluminum.



The last thing that to cut was the holes for the tie downs. These were pretty easy but apparently I didn’t take any picture of the process.(I was pretty ready to be done at this point) I just cut a template out of the MDF, used the drill press to remove as much of the metal as possible, then used the flush trim bit to follow the template in the shape I wanted.



And just like that, the side plates were cut. I hit them both with my orbital sander to round over the sharp edges and sand out any imperfections. After that they were ready for some aluminum primer and bed liner.

For the mounting feet I decided to go with some 1” aluminum C channel I found lying around at the metal yard. I think it cost me $4. I cut these down to 2” lengths and drilled holes through the top to attach to the cross bars, and in the bottom to attach to the track on my topper. If I were to do these again, I would make them a little wider so you can offset the bolts. Having them line up made installing them a bitch. I bent the C channel because the tracks on my topper are angled. This way they sit nice and flat on the cross bars and on the track. No shims or washers needed.



I cut some 1/8” x 3/4” aluminum down and forced some carriage bolts through them to slide into the tracks in my topper.



I tired to paint he stainless steel locknuts for the feet but they got pretty scratched up when I installed the rack.



All said and done I am happy with how it turned out. I was looking for something as low profile as possible and I feel I achieved that. Other than the feet, the only thing I would do differently is use a slightly larger plunge bit for cutting the slots. After the layers of paint, the ¼” button head screws were very tight and don’t slide very freely. One thing I didn't consider when i was figuring the cost in my head before starting the project was the cost of all the stainless steel hardware, it really adds up. The final cost after the aluminum, feet, cross bars, all the hardware, and paint ended up $310 (excluding the tracks and ski racks) Not to shabby! I’m considering trying my hand at a custom access rack next but who knows.


Anyways I hope this helps someone! Here are some pictures of the finished product on the truck.







Here is a YouTube video that inspired me to cut aluminum on a router.
https://www.youtube.com/watch?v=EnSiq4sfzI4

Links to materials

1"x2" Black Aluminum Extruded Cross Bars

ASNOMY 4pcs Bearing Flush Trim Bit Set with 1/4" Shank，Top End Bearing Router Bit Set, 1/4" 5/16" 3/8" 1/2" Cutting Diameter Milling Bits for Woodworking Tool with Storage Bag

Flush Trim Router Bit 4 pack

$9 COMOK 2Pcs 1/4" Cutting Dia Double Flute Straight Router Bits with 1/4" Shank (Size:1/4 x 1/4)

1/4" Plunge Router Bit
Black Stainless Steel Button Head Screws
Black Stainless Steel Washers

1/4" - 20 X 1" (50 Pack) Stainless Carriage Bolts, 18-8 (304) Commercial Grade Stainless Steel, Corrosion Resistant, Heavy Duty Choose Size by Bolt Dropper

Stainless Steel 1/4-20 1" Carriage Bolts

1/4"- 20 Nylon Insert Hex Lock Nuts, (Elastic Stop Nuts) Stainless Steel 18-8, Plain Finish, Quantity 100 by Bridge Fasteners

Stainless 1/4-20 Nylon Lock Nuts

 

Nice work!

For the AC rack, if I ever go that route, I would follow in your footsteps.

The thing that had me stoked there are the Rhino Rack rails:
https://www.amazon.com/dp/B07MK7KD2V

They only make ones for DCs, but they are easy to adapt to ACs. There are a couple threads about it here.

 

Looks good!

 

Yeah those tracks would be perfect! I think making curved template would the toughest part of a cab rack. With the top rack everything was just straight. Getting a nice, smooth curve cut by hand would be challenging!

 

Thanks man!

 

Damn, just bought the top rack too.. Only thing is I don't have a plunge router, or an orbatal sander. This thing looks better than the Prinsu one to me. I think I would have made those eye-drop slots a bit thinner, but that's just me.

Also, the metal shavings!! I routed slots into some aluminum a few months ago to make some brackets for my cab rack and I'm STILL getting shavings in my fingers on occasion. How do you clean up the metal shavings?

 

Nice work!

 

After your excellent work, I think the large curve of the cab would be no big deal. Just start with a paper template, then go to wood. Or, just offset it and ignore the tapering gap?

For the most part, you could probably trace the Rhino Racks before installing?

 

Nice. fabricating your own stuff is great. I plan on building a similar rack out of Aluminum 0.25" plate I have left over from my skid plate build. I already built some rock sliders with my 2" tube bender and they came out super nice and aesthetic (love the 2" tube look)

For the roof mounting feet you used aluminum C brackets. I was probably going to use 1/8" or 3/16" steel tabs just for the brackets because they experience all the pressure / sheer. I think for the 4-6 brackets the weight cost is insignifiant. Let me know how the brackets hold up after tightening them all down.

 

Thanks! Yeah my router is an old craftsman one but it got the job done. But yes, there are metal shavings still coming out of the woodwork. I did rig up my shop vac to suck as many as possible during the cuts but they still ended up everywhere.

 

Very nice man!!!

 

Nice write-up. Thank you for sharing. I always like reading these type of threads. Gives me new ideas of things to do!

 

Yeah the feet are the only area I worry about. I decided to go with 6 instead of 4 and so far it feels pretty stout. I've put about 2000 miles with the rack on, most of which I had a snowboard and skis catching wind on the highway, and so far they appear to be holding up. I don't think that going with steel would be a bad idea at all especially if you plan to have a RTT or a lot of weight up there. I guess the only con would be rust. I will definitely update if they start giving me problems!

 

If you go the ditch track route drop the head liner to locate your drill locations, the airbag curtains are right there. They can be moved aside without disconnecting, just some 10mm bolts to remove. I also prebent the tracks a bit more since our AC roofs have more curve. Pics and suggestions in my build thread.

 

Fantastic custom build !!!

 

Great write up, I definitely learned some things reading through that

 

Thanks!

I would definitely pull the headliner to do it right and do Noico at the same time.

 

Fantastic. I am a woodworker and was thinking that it’s aluminum so all my tools would theoretically work to do something like this. Thanks for showing the way. Now I just need to wait for warmer weather to get started. Brilliant write up!

 

Thanks that's good tip. The airbags have been one of the reasons I haven't moved forward with the Prinsu Acesss rack. I didn't think about the fact that the ditch mount increases the number of locations you can mount, thus decreasing potential issues with the airbags. What rack did you install on your cab?

@tonered Definitely take the extra time to do some sound deadening. I've heard that the cab racks add a good amount of wind noise. The ACs are already pretty noisy ha

 

Beautiful...absolutely F'ing impressive. Nice work.