Spreader bar fabrication
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Hi,
I am looking for some details on the most cost effective way of fabricating the spreader bars.
Questions:
Aluminium scaffolding bars ok?
What diameter rod for eyelets?
How best to bend rod into eyelets?
What load can the eyelets withstand?
How best to stop corrosion when in seawater?
Life span of spreader bars?
How to stop chaffing between metal and lines?
Cheers,
Toby
BluGreens
@tobias_stevensfleming47 here's a post where @clifford_goudey answers a couple of your questions. Also take a look at the webinar he's mentioning - may be useful!
@jwhis Thanks!
@jwhis is the post the paper on cliffords report on kodial?
Whoops I forgot the link! It was from this community post @tobias_stevensfleming47
@jwhis Thanks!
@tobias_stevensfleming47 Hi, I have some experience with aluminum spreader bars for a 5 line array. Feel free to call and I can offer my opinions. Mike@pacificseafarms.com
@jwhis is the post the paper on cliffords report on kodial?
Whoops I forgot the link! It was from this community post @tobias_stevensfleming47
Toby @tobias_stevensfleming47 , you wrote:
Hi, I am looking for some details on the most cost effective way of fabricating the spreader bars.
I'll try to answer your questions in turn.
Questions: Aluminium scaffolding bars ok?
Aluminum is a good choice for its strength/weight ratio, corrosion resistance, and ease of fabrication. We sometimes build in steel, but unless it is Galvanized, it too-quickly rusts away. We typically use 1.5" to 3" sch 40 pipe in 6061 alloy (very common in marine applications). I do not know the diameter and type of aluminum used in scaffolding.
What diameter rod for eyelets?
We use 3/8" diameter round bar in 6063 alloy for the bails, as it is more easily bent without cracking. 6063 in this form has a typical tensile strength of 30,000 psi, so at 3/8" diameter the rod's tensile strength is around 3,300 pounds. A good welder can match that when welding it to the pipe, so the arrangement is compatible with rigs that use 3/8" to 1/2" growlines.
How best to bend rod into eyelets?What load can the eyelets withstand?
The above round bar can be bent 180˚ around a 3/4" mandrel without cracking.
How best to stop corrosion when in seawater?
Be careful not to bring any steel, stainless steel, or other higher-nobility metal in contact with the aluminum or it will corrode away just like an anode on a steel ship.
Life span of spreader bars?
I'm not sure. Unless they are overloaded or otherwise abused, they seem to last for as long as we've been making them.
How to stop chaffing between metal and lines?
As when making a line up to anything, make a connection that does not move around. Here is one of out growline extensions attached to a spreader bar bail. You start with a 6" to 8"eye splice and then loop it through the bail. This will cinch up tight over time.
If there is no splice, then a bend knot will work. Here is an angled bridle coming in to the end of a spreader bar with the bail purposely angled to accommodate.
I hope this insight is useful to you. Feel free to reach out with any further questions.
Cliff
@clifford_goudey thanks for all the info its just what i needed. Sorry for the delay in getting back to you. I saw a squirrel and was preoccupied for some time!
@clifford_goudey thanks for all the info its just what i needed. Sorry for the delay in getting back to you. I saw a squirrel and was preoccupied for some time!