HOW TO: Kayak Rack (for under $35)

Discussion in 'Fabrication' started by Arizona KJ Carlos, Dec 5, 2007.

  1. Arizona KJ Carlos

    Arizona KJ Carlos Full Access Member

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    I recently saw a posting on this site on how to do a roof rack for a Jeep Liberty, so I decided to take some “poetic” freedom and create a similar kayak rack but one that would be made of more sturdy materials and would also look like a professionally made rack. This is the process that I followed to create this rack, all of the parts that I am using I got at The Home Depot and I am including the part number since there are a few parts that look similar but are not the correct one.

    The parts I used for this were:

    (2) Aluminum square tubes, 48” long part # 030699406203 $ 11.27 ea
    (1) pipe insulation strip of foam, part #718793150115 $1.38
    (4) 2” u-bolts, part #030699095360 $1.98
    (1) 35” rubber tie down, part # 734884853512 $1.98

    that is it…the total cost was only $33.82 plus tax!

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    The first thing I did was measure the perimeter of the roof rack that comes standard in my KJ. For you can use a strip of cable, string, anything…. Then I cut the 35” rubber tie down into four equal strips that are the same length as the perimeter of the roof rack.
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    These strips will be used to cushion the kayak rack on the roof rack. Next I sprayed painted the aluminum tubes with white primer (I know aluminum doesn’t rust), this makes the black paint stick better to the tubes and it also helps when marking the tubes.

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    Once they dried, I rested them on top of the roof rack and centered them so they have an equal amount of length sticking out on both sides. Then, I passed the u-bolt through the factory installed rack and make sure to center the bolt so I could mark where I need to drill the holes on the aluminum tube.
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    I then, did the same for the other three spots that will need to be drilled.

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    Once the holes were drilled I painted the aluminum in black so that it doesn’t stand out too much and to make it look like a professional rack. Once the paint dried I cut the pipe insulation in half and pass it through the aluminum tube.

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    The insulation pad had a cut down the middle and even though it wasn’t completely open I decided to add some tape to reinforce this foam…I could just see that padding coming off once I hit the freeway.
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    Once this is done, I placed the new bars back on top of the factory rack and used the u bolts to secure them and that was it. I tied them pretty hard but not TOO hard that they would damage the factory rack.

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    Let me know what you guys think…I cut the remaining parts of the u-bolts in the back, BUT on the front I am leaving them as I am planning on creating a detachable light rack that I can tie into those bolts when I need to use it and then take it off when I am done off roading…that would help with gas efficiency.
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  2. KJjeepster

    KJjeepster New Member

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    Beautiful-nice job(that's similar to my set up).
    In addition, I went to the Hardware store and got x4 rubber stops or tube ends (like the ones you see in metal table/chair legs)
    and closed off the tube'ends'.
     

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  3. Arizona KJ Carlos

    Arizona KJ Carlos Full Access Member

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    I actually went to Lowes yesterday but couldnt find them. I will look again...thanks for the idea. One quick question, did you also make your own cargo basket or is that a Thule one? I would be interested in making my own...
     
  4. BRASMAN

    BRASMAN New Member

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    Fantastic. I was just thinking the exact same thing but for snow boards and skis. All the set ups I have seen are going to be at least $300. You just showed me that this idea will work. Thanks. :D
     
  5. Arizona KJ Carlos

    Arizona KJ Carlos Full Access Member

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    Yep, to use this set up for skis just place the skis where the kayak would have sat on this rack, then use another pair of tube and insulation and place them on top to secure them. I have used butterfly nuts to secure them and that way I can take them off easily. I'll try to take a photo tomorrow to show you what I mean. I left the ubolts without cutting them on the front so I can secure other things such as skis, or even a light rack.

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  6. Arizona KJ Carlos

    Arizona KJ Carlos Full Access Member

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    Here is the photo with the light rack on top...it impacts the efficiency of the car, so I take it off when I dont need it. Pretty easy to make and very inexpensive. I think I must have payed about $25 for the whole thing...

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  7. desertkj

    desertkj Full Access Member

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    Very nice. I can't believe I did not see this write up when you posted it in December.
     
  8. ObiHann

    ObiHann Full Access Member

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    Great idea! Personally I would of marked and cut the bolts, and the trimmed the cross bars so they dont need to be exactly 4' long, but great idea! I'm gonna give this a shot once I get paid! I think I will eventually mount a real kayak rack on top of that, but that is the best cheap cross rail guide I've seen!
     
  9. ObiHann

    ObiHann Full Access Member

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    Was thinking this would be even stronger using all steel square tube, but seems to me that would rust out pretty fast, I wonder how much weight this aluminum can hold??
     
  10. snowsport

    snowsport Full Access Member

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    I've had square steel tubing up top for a couple of years and no rusting. I take them off each spring and repaint them. Also I plugged the ends so no moisture gets in to rust the insides.
     
  11. ObiHann

    ObiHann Full Access Member

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    What did you use to plug the insides? Seems to me that would be a strange item to buy at a hardware store... I like the idea of square steel though, I'm sure the added weight wouldn't be too big a issue, and the added strength and resistance to bend would be the most important factor!
     
  12. snowsport

    snowsport Full Access Member

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    I used 1 1/4" square steel tube, which are mega sturdy and not too heavy, just a few pounds each. For the ends, I cut some blocks out of Honduran mahogany and glued them in with waterproof glue. Then I painted the bars with black rust paint, including the ends of the plugs. I've got a pic around somewhere........
    Here it is:

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    The reason I used mahogany is because it's a good weathering wood, and I happened to have a chunk laying around. You could just rip a chunk of spruce or pine and tap in into place, and the waterproof glue will seal it up. Then just soak the end grain with paint to seal it.
     
    Last edited: Feb 19, 2009
  13. ObiHann

    ObiHann Full Access Member

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    I wonder if I can just find some rubber square plugs?
     
  14. snowsport

    snowsport Full Access Member

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    Yep, depending on the size of tubing you use, you could probably just hacksaw up a hockey puck or something and glue the cubes in the ends. If you use the expanding glue (polyurethane, like Elmer's Ultimate, etc) then it'll fill up any cracks. Might even find some chair leg plugs at the hardware store that'll do the job, or something along those lines.
     
  15. Boiler

    Boiler New Member

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    In an effort to avoid the "Steel is stronger" or "Aluminum is lighter" generalizations, I decided to bore you all with some numbers. Aluminumunder a load will deflect about 3x as far as the same exact shape of steel will. However, in my book, failure is usually yield, or the point where a permanent deformation is made. (i.e. the material does not spring back) If both tubes you are comparing have the same exact cross section, the one with the higher yeild strength would be the strongest. Yeild strengths of some common materials are:

    Steel A36: 36,000 psi
    Steel A500 tube: 46,000 psi
    Aluminum 6061-T6: 40,000 psi
    Aluminum 6063-T5: 27,000 psi

    Lets compare a couple common sizes of tube. Most readily available aluminum square or rectangular tubing has 1/8" thick wall. Typcial steel that I would put on the roof of my jeep would range between 16 ga. (0.06") to 3/16" thick.

    TUBE 1: 1-1/2" square x 1/8" thick aluminum 6061-T6
    - Yield strength: 40,000 psi
    - 0.8003 lbs. / ft
    - 0.291 in^3 section modulus (main factor in bending strength, based purely on size and wall thickness)

    TUBE 2: 1-1/2" square x 14ga thick (0.80") steel A500 tube
    - Yield strength: 46,000 psi
    - 1.6 lbs. / ft
    - S = 0.204 in^3 section modulus

    Rs = Stube2 / Stube1 = section ratio
    Ry = Ytube2 / Ytube 1 = yeild strength ratio

    In this case, Rs x Ry would tell you the bending strength of the steel tube in % of the bending strength of the aluminum (thicker) tube.

    Rs x Ry = 0.204/0.291 X 46,000/40,000 = 0.806

    In this application, the steel tube weighs twice as much but is only 80.6% as strong in bending as the aluminum. Remember though, the deflection in the aluminum will be larger. It is a similar comparison as I just showed, but instead of Section Modulus and yeild strength, you'd need to compare Modulus of Elasticity and Moment of Inertia.

    Note 1: This does not mean that steel is always twice as heavy and 4/5 as strong. Only after considering loading and cross section can ANY comparison be made between the two. In this case, it was true.

    Note 2: I know some people will come back and complain that I used a thicker aluminum tube, but its still 1/2 the weight of the steel!
     
    Last edited: Feb 19, 2009
  16. Ry' N Jen

    Ry' N Jen Banned

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    These look good guy's!
    If it wasn't for the fact that I have three complete Thule roof rack systems kicking around the house (Used to sell them and got quite a few free-bee's during the years!) I would of done the same thing. As far as the exposed threads showing from the "U" bolts, just slip some automotive vacuum caps over them so you damage your gear of yourself when accessing stuff up top.
     
  17. icarl

    icarl Full Access Member

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    ouch, my head hurts. :D Modulus of Elasticity, hmmm.... I think i forgot something like that from when i was in engineering. yep, you must be an engineer. ;)
     
  18. Boiler

    Boiler New Member

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    Sorry about that, and to the OP. Posts like that seem to kill threads...

    I shoulda just said "Aluminum is good too!" :)
     
  19. dr_love2112

    dr_love2112 New Member

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    i did it, just like the 1st post but i drive around the city and i get a humming sound, i took them off and it stopped.....its not loose nuts, and the bars where on good.....whats up with that???
     
  20. snowsport

    snowsport Full Access Member

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    Air passing under the bar and over the roof, like a wind instrument. The bars on top of my KJ moan at some speeds or if there's a headwind or crosswind. That reminds me, gotta take them off for the road trip Monday (don't need them and they just add wind resistance).