Excavator lifting boom, part 2

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The boom is made out of 8mm steel and is 20cm x 14cm

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There are four 10mm steel plates supporting it.

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I will make some additional supports like pic related but as I'm not welding these myself I need to have my friend over. He is a welder, like 40h/week welder. Like that I can trust that the welds will be proper. The struts will be probably something around 10mm or more flat stock.

Any ideas about the strength of a thing like this? It has three extensions which of two are hydraulic but this first will be the one that will do the heavy lifting. Eventually this whole thing will dredge my shoreline. But that is after the house is finished.

>>1117130
The steel plates go up the boom for 40cm.
That leaves 180cm of boom without support (for now).

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>>1117133

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Here is the rest of the boom for those I te rested. Partly taken apart. One cylinder needs to be removed so I need to dismantle it first. Some bolts are stuck and I'm soaking them in 50/50 atf/diesel. Might be too thick for the current weather. I would need apropane+oxygen torch to heat them properly. Propane alone doesn't seem to do the job. Or LNG it is.

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Parts already loosened. I cut the support for the outermost cylinder as it is going to be moved inwards.

if its for lifting people add some sort of steel stopper in case the hydraulic seals fail which would make the entire excavator arm drop to the ground instantly

>>1120354
I'm not sure that is the biggest risk, a bursting hydraulic hose is more common. There are special valves that can be attached to the cylinder end of the hose that prevent the falling. And I don't think I'll lift people with it. The excavator has almost 23000 running hours and is from -81 or so...