# Tritruss apex down or up



## taptotweet (Jan 3, 2014)

Hi all,

Just out of interest, for those of you who do stage rigging do you fly tri truss apex down or up?

The company I work for always rigs apex down, as it's much easier to hang movers from one pipe than two. 

Sam.


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## derekleffew (Jan 3, 2014)

Apex DN: one bottom chord in tension, two top chords in compression.
Apex UP: two bottom chords in tension, one top chord in compression.

Tension is weaker than compression (although with truss tube by a very small margin), thus it's better to help it out by doubling the number of chords in tension. (Except for very short runs, or not-heavy loads.)
Does that make sense?

On _This Old House_, when a plumber must drill a hole or notch a joist, Tommy says to make it in the upper third of the joist. Notching in the lower third effectively turns the 2x10 into a 2x6 or whatever.


taptotweet said:


> ... The company I work for always rigs apex down, as it's much easier to hang movers from one pipe than two. ...


 Point DN also gives one a flat area to lay cabling, but Point UP using cable hangers solves that.


http://www.citytheatrical.com/Products/cable-hooks# One commercial product, but not difficult to fabricate oneself. I'd at least add a safety cable to the above; when I built some years ago I drilled holes to accept a scaffold pin to capture the top chord.

Most movers' clamps can be positioned to use two chords of 12" truss. OR, stagger the fixtures, half on each chord.

I can't tell if you're using the term "tri truss" as a brand name or generic type. Read what the manufacturers' of triangular truss websites say, and follow their instructions. Some state that their truss is equally strong and can be used either way.


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## bclighting (Jan 4, 2014)

derekleffew said:


> On _This Old House_, when a plumber must drill a hole or notch a joist, Tommy says to make it in the upper third of the joist. Notching in the lower third effectively turns the 2x10 into a 2x6 or whatever.
> 
> I can't tell if you're using the term "tri truss" as a brand name or generic type. Read what the manufacturers' of triangular truss websites say, and follow their instructions. Some state that their truss is equally strong and can be used either way.



While I agree completely about the advice about following the manufacturer's spec on tri truss, something is very off about Tommy on "This Old House". Code is that you can't cut into the upper or lower thirds of a joist. All holes must be in the middle third. I know that's not related to anything here, I just found that funny


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