How strong is unistrut?

[Mitch502]

I'm looking at adding a rack for my RTT to my 5x8 utility trailer. I wanted something that I could mount the RTT on top of, fit bikes underneath in the future, as well as store things on the trailer itself of course.

I have a lead on 1-5/8 in. x 13/16 in. 14ga unistrut, but wasn't sure if it was strong enough? Is it strong enough for horizontal bracing and mounting points as well?

Thanks for in input in advance,
Mitch

 

[Mitch502]

If any engineer can explain this to me I'd appreciate it. These are unbraced weights, but I'm not sure if I should be increasing substantially for the shaking that will occur... Obviously would have bracing as well

 

[billiebob]

It is an industrial building product. Not ever designed for a dynamic load, Stick with tried and proven products like 1x1, 1x2 or bigger tubular steel.
And it is a bolt together product, I'd only use welded steel in a homebilt rack. I'll bet it is exponentially expense compared to welded steel tube.
Most of the uses for unistrut are frame works to hang things from. Rarely is it used ro support loads.
But if you must try it be sure to keep this thread updated.

 

[NatersXJ6]

It is subjectively very strong. The Unistrut catalog has all sorts of basic engineering data published in it. You can figure out the load supported at various spans at least. With proper triangular bracing at the corners, I wouldn’t hesitate to use it for a rack.

I’ve used it for rooftop tent crossmembers many times. Check the load charts, but IIRC the 48”
Span for 12 gauge is 800 lbs give or take. I would downgrade about 4x for dynamic loading.

One thing to beware of is that the fastening systems can slide down the strut if not well braced or fastened. It does take some thought to build with, and you might have to custom bend some joining pieces, or weld a few pieces here and there, but it can be good to build with.

I’ve thought about using it before, but realized that I would end up welding so many custom bits that it just seemed easier, lighter, and cheaper to work with bent tubing instead, but I already have the tools for that.

 

[VanWaLife]

Well the different K factors represent different bracing configurations, but it's probably going to be plenty strong as a column anyhow, it's the beam type loading where you could get in to trouble. But you probably won't, really depends on what it is connected to and how it is connected. You can use it bolted back to back, roughly doubles the strength, but makes connections trickier. I used it for stakes to build trailer sideboards. Works great, I made some little clips that work with the strut nuts to tie the corners together. But its strength in that configuration is pretty much moot, it's mostly the plywood sideboards the strut is connected to and the corner connections that make it a good system. You won't save much if you end up buying a lot of their prefab fittings, those things are expensive. I don't love the finish. Definitely vibration is a concern for any strut nuts; they don't make a nylock strut nuts so far as I know. You might find yourself in a square block, round hole type situation trying to make an entire rack out of it, but I can certainly see how it would be useful for mounting a bunch of stuff to the rack.

 

[outback97]

It’s worked great for my purposes but admittedly they’re shorter spans and lighter loads than a RTT.

In my application the appeal of it is the ability to make it customizable and bolt on whatever you need for a given trip. For something more permanently mounted just square or round tubing might make more sense, but I bet it’d be strong enough for your intended use.

Here’s my strut channel rack:

How To - Strut Channel Cross Bars / Roof Rack

This started off with my needing a solid and low profile way to mount Rotopax fuel cans to my roof. It has become for us a versatile crossbar / rack system that gets used on almost every trip. Using the channel strut crossbars we have carried all of the items below, sometimes multiple items at...

www.xterranation.org

 

[Alloy]

The 13/16 isn't the best size but you can put 2 back to back to increase the strength if weight isn't a concern.

 

[Mitch502]

Thanks for all the input! It's very helpful. I will report back when I get a chance to do the work!

 

[NatersXJ6]

Also consider that the commonly available home center stuff is electro plated, and it can be a real PITA to paint or powder coat. You can order raw steel from an electrical supply house if you’re going to be doing custom welding or paint/powder.

 

[NikonRon]

Also available in stainless steel and aluminum.

 

[outback97]

I have sourced most of mine for the roof rack projects from McMaster Carr.

McMaster-Carr

McMaster-Carr is the complete source for your plant with over 595,000 products. 98% of products ordered ship from stock and deliver same or next day.

www.mcmaster.com

When I last purchased a 6'8" stick of the low profile, solid, black powder coated in February of 2020 it was $24.00.... currently $74.40.

 

[Titan_Bow]

I’m not planning on a RTT, but I made a rack for my canoe and some solar panels with unistrut.


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[smike95]

I used some unistrut for my cross bars on my 4Runner. Love them so far, very strong and extremely versatile.

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