V mat home built sluice

[Foulwind]

Greeting all, been a while since i've posted. A while ago, I purchased a V mat roll 12 x 48" and built a quick 1/2" plywood sluice to set the mat in. I'm suppling water with an 1100 GPH bildge pump and a speed controller for it. Its been in use now since Nov 25' I can process a 5 gal bucket of sand now in just over an hours time, instead of 3 days like before running the same amount on my 3" x 48" clean up sluice.
During my todwys run of beach sand i was watching the V mat work as sand was washing down and clearing the mat, leaving black sand behind filling the troughs. The black sands and blonds in the grooves were "Dancing" and clearing. I noticed something a little odd today. I placed a finger on the mat over some black sand and water flow washed the top layer of black sand out exposing blonds (Sand) beneith. I can't say i've ever really noticed this before. I thought the black sand occupied the grove bottoms with the gold. SoI was a little surprized to see sand under the black sand. This brought up few questions. Why was there sand below the black sand? Am I running enough waterflow? I typicall run a low flow, with just enough volumn to wash small pebbles down the mat. Am I running the water flow too low? Maybe the mat isn't clearing properly? Just when I thought I had my process somewhat dialed in, I find this little issue. This does explain an excess of sand in pan after cleaning the mat now though.
Sorry for the long read, it helps me work out issues by going over them again while typing. In the mean time, I'll try adjusting my process, water flow, feed rate, feed amount, adding rocks in water stream. The sand at my local beach has been consistant in its gold with approximately 400-600 colors ( Just enough colors to make it hard to actually count them)0per 2 pans sluiced so I can do a little testing by changing up water flows and feed rates and amounts. I forgot to mention, i run my V mat sluice with a 12 degree angle. Im wondering now if I should flaten it some? Same water flow less angle, should help gold settle out of water colom but will it help with clearing out the grooves? Someting to ponder over and now loose sleep on.

Well, if ya got this far, thanks for reading.

 

[russau]

Good question ! I'd start with using a good level to check out your set up. Side to side then look at the matting itself to see if there is ANY blemish's in the rubber mat that may cause a disturbance in the water flow. once done with that I'd play with the sluices angle (slowly) and see if you could clear up your problem ! You may need to speed up your pump a little ! Also scrub that rubber mat clean of ANY chemicals from the making of the mat ! GOOD LUCK and thanks for posting this question !

 

[russau]

Well did you improve your sluice set up ?

 

[BoulderTroll]

That is some interesting observations.
The question I would like to ask is are you losing any gold?
Personally, I wouldn't mind having a few blonde sands as long as my loss rate is acceptable.

 

[coolfinie]

The deepest narrowest part of the vee grooves have less interchange than higher in the (wider parts of the) groove where current gets in more. I suspect that if you primed it with black sand, not much blond sand would get down there at all. But why bother? So long as the gold isn't walking down that mat everything's good!

 

[russau]

Starting your engine / pump WILL CAUSE fine gold to move down the sluice AND stopping your engine pump WILL ALSO CAUSE fine gold to move down the sluice. So it is important while running a High banker or a dredge to slowly raise or lower your engine speed to prevent this happening !

 

[Foulwind]

Well did you improve your sluice set up ?

Not yet. Sluice angle is 11 degrees, i make sure water flow off the end is even across its width before adding sand. I gauge the water flow by how I see the blond sand "Dancing" in the grooves and how much the sand walks across the grooves. I start the pump with a low flow the then feed small scoop of sand and watch how the sand flows down the mat. Is the sand moving down evenly? Is the sand congregating to one side? Middle? And make fine adjustments until the sand moves down evenly or as close to evely as i can get it. As the sand moves down mat, the mat changes color as the sand fills the grooves. Slowly the blonds get carried down and the shade of the mat gradually shifts from sand color to black. When the mat shows overall black, i fèed another scoop of raw sand and start all over.if the time it takes the shift in color fromtan to black seems be long I'll adjust my speed controller up a tine bit to increase water flow. I've timed this shift in color on my small gutter sluice to be about 15-20 seconds. Thats my process for washing my local beach sand at the moment.
Now, one thing thats been in my thoughts in regards to my pump is, my supply line from pump to my home made header box, pump outlet is 11/8"
Im using a "Garbage disposal" flex hose that has multiple rubber size openings to accommodate different outlets. The flex tube is i think only 3/4" ID
So the pump volumn at it outlet is accelerated and the header box side uses the 3/4" rubber end. I get plenty of volumn of water but its blasting into my header box then spilling out. I just wonder if I replaced the curent supply hose with a proper 1 1/8" X 6' hose, how the water flow down tne sluice will be affected.

 

[Gold:Au]

The deepest narrowest part of the vee grooves have less interchange than higher in the (wider parts of the) groove where current gets in more. I suspect that if you primed it with black sand, not much blond sand would get down there at all. But why bother? So long as the gold isn't walking down that mat everything's good!

This will be the reason.
The vortex that causes the sand to dance just doesn't get down into the bottom of the V, so the blond sand that settles there just doesn't get removed. I wouldn't worry about it, the V-matting is working as it should.

 

[russau]

One other thing I'd do is get a good sample of your "blond sand" and have it analyzed to make sure it is blond sand and NOT something else like a precious metal ??