Riffle spacing

Hi all
Ive just about finished building a couple of river sluices for my son and I and Im unsure on the spacing for the riffles Im running miners moss with expanded mesh over fine rib matting any advice would be much appreciated once Ive finished Ill post some photos.

Mate what are the width and length of the sluices? I'll just find that formula for you. I take it you are just doing a standard flat bar angled riffle? as it can vary with each style, Hungarian, Clarkson etc even Clarkson's have their own variations within the design.

If you have the ability I suggest you spend the time to knock up Hungarian or Clarkson riffles as flat bar riffles are substandard, they simply lose gold, if you even see a hint of light under a flat bar riffle ontop your expanded and moss you are losing gold. They really do not create an effective vortex or low-pressure areas. They ended up in weekend prospector's sluices mostly out of laziness because they are easy to knock up not because they are effective and quickly became the norm. They are more effective in large-scale mining where the bars are about 100mm width and used in the top run as nugget traps, then most people use hydraulic riffles after them.

3rd style over, Hungarian with a tail rather than the Lazy L, my favourite design. Clarkson are arguably even more efficient but are much more fiddly to setup correctly, angle of the sluice in water, the water flow and feed rate all have to be perfect for Clarkson, Hungarian much more forgiving and actually help break up the material you are feeding the sluice.

http://www.goldhog.com/riffle_study_science.htm

http://www.goldgold.com/the-size-of-riffles-2.html

http://nevada-outback-gems.com/prospect/Cal_dredge_trip/home_made_3_stage.htm

Mate it is around 9 wide 36 long 2.5 sides and the riffles are the same as the third one in your picture Hungarian with a tail

Just one more thing then, how high are the riffles? That determines the distance.

Are you thinking of starting the riffle at the very beginning of the run or maybe leaving some open v-mat like Keene/Jobe do

The riffles are 10 mm high 28 deg with 5mm lip do you think they will be big enough? I've got no idea what I'm doing just tried to put a photo on but it's to big will have to get my young fella to have a look

Thanks for the help AussieChris tried out the sluices yesterday recovered some small specks of gold but had a bit of a challenge trying to get the flow and angle right so as not to clog up the riffles but still learning will try again in a couple of weeks when on days off again cheers mate.