How long of a box do I need, realistically.

[Reed Lukens]

Stainless
Gold high banker sluice

After looking at this mini highbanker It has about the same capacity of the Gold Cube for close to the same price. Go with the Cube if you want to go this route. I say this because from what I can see from the Colorado Gold Banker, it;s really basic as far as design so no big deal... The guy selling it wants to get as much of his money back as he can but personally I would think it's worth maybe $75 because I can get a new South Yuba SYuba exclusive products for about the same price.
Colorado Gold Buzzard Mini Highbanker 12 Volt Operation

 

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[joncutt87]

If I build from scratch, how deep should my sluice box be?

 

[Goodyguy]

If I build from scratch, how deep should my sluice box be?

My advice is 3-1/2" bare minimum to 5" maximum. I like to go with 5" on a highbanker sluice in case you ever wanted to go with 1" riffles and run it more aggressively with a deeper flow. Keene goes with 4-1/2" which should be plenty deep for most highbanker applications.

GG~