Constructing a mash tun

[prolix]

I bought a sheet of perferated stainless from RS 590cm by 50 cm and cut it to a circle using tin snips and use that as my FB. Hold it off the bottom with stainless screws.

You could just get a sheet to go over the centre part that drops down. you can get it on ebay as well. and just put some screws in to keep it located at the centre hole

 

[Springer]

Thanks P
Checked it out and it could be the way to go. I was thinking mesh and was worried out the edges fraying off but you are talking perferated.
S

 

[Springer]

Got a plan B now,
I have a piece of 8 mm polycarbonate big enough for a disc 370 mm diameter to be cut cut from it.
I recon I can cut slots radially to give a total length of 2500mm/ At a width of 1mm this will be 2500 mm or at 2mm obviously 5000 mm 2. A 15mm pipe is roughly 150mm 2.
So the question are? What width slots do I need and do I need this many? I seem to remember reading somewhere that slots were better than holes :?
I have abandoned the disc pictured high up the post, made for a boiler floor, because the holes were 3 mm dia and considered too big for a mash tun.
Comments very welcome. Apart from going out and buying some perforated stainless :lol:

 

[evanvine]

I understand MD's got a spare mash tun, save you all that effort :twisted:

 

[jamesb]

Got a plan B now,
I have a piece of 8 mm polycarbonate big enough for a disc 370 mm diameter to be cut cut from it.
I recon I can cut slots radially to give a total length of 2500mm/ At a width of 1mm this will be 2500 mm or at 2mm obviously 5000 mm 2. A 15mm pipe is roughly 150mm 2.
So the question are? What width slots do I need and do I need this many? I seem to remember reading somewhere that slots were better than holes :?
I have abandoned the disc pictured high up the post, made for a boiler floor, because the holes were 3 mm dia and considered too big for a mash tun.
Comments very welcome. Apart from going out and buying some perforated stainless :lol:

Most of us have slots the width of a hacksaw blade

I'd say 1mm would be fine. With a disc the size of your's, you won't need them as tightly spaced as we do with our copper manifolds. Why not try a slot every 25mm - you could always add more later.

The commercial boys (or the non-Porter equipment at least) have an interesting false bottom that's made up of lots of slots, but fabricated from lots of triangular shaped bars.

 

[Springer]

I understand MD's got a spare mash tun, save you all that effort

Nearly finished now and I like making stuff

Most of us have slots the width of a hacksaw blade

Thanks J
Not against the tube and hacksaw option, have this in my picnic box mash tun, works great. I thought in a pumped set up you had to have a floor arrangement, for the liquid to collect under it ready for pumping, rather than the pump sucking at the slots, near to the grain.
I am no expert, if a normal manifold will do, may go that way

 

[jamesb]

I understand MD's got a spare mash tun, save you all that effort

Nearly finished now and I like making stuff

[quote:qk6t5m05]Most of us have slots the width of a hacksaw blade

Thanks J
Not against the tube and hacksaw option, have this in my picnic box mash tun, works great. I thought in a pumped set up you had to have a floor arrangement, for the liquid to collect under it ready for pumping, rather than the pump sucking at the slots, near to the grain.
I am no expert, if a normal manifold will do, may go that way[/quote:qk6t5m05]

Vossy will know more, but that does make sense. I use an underback, as I haven't finished my false bottom yet.

My point was more about the width of the slots though, rather than the actual design used.

 

[Springer]

Vossy will know more, but that does make sense

Nice to know my thinking was along the right lines. Could go down in size to hacksaw blade width size, but don't want them to get blocked and too big will let grain though, like life its a compromise
Best wait for the Master to comment :)
Don't want to kipper up my polycarbonate, an old timer once taught me "think twice cut once" not the other way round. :lol:

 

[Aleman]

The best design for false bottoms with either slots or holes is to have the slots/holes wider on the bottom of the false bottom than the top . . . Easy with holes you just countersink them . . . slots are a bit more tricky as you have to counter mill them. I do have the recommended slot measurements (Length / width / spacing) at home, and will try and dig them out this afternoon.

The reason why you want the holes/slots bigger on the underside, is that if they get a particle stuck in it, it finds it easier to get through as its bigger . . . while this allows particles through, it prevents the FB from blocking . . . after all it is the mash bed that does the filtering NOT the False bottom/manifold.

I have a very nice Stainless tray from Tescos that I have been thinking I want to drill a load of 1.2mm holes in for a FB . . . . Then I thought about cutting slots in it using an angle grinder with a slitting disc . . . which are just about 1mm thick . . . much quicker and less risk of breaking drills . . . If that doesn't work I can put a Perforated FB in place instead

 

[Vossy1]

My mash tun fb has 1.5mm holes. Morebeer fb's holes are 2mm IIRC and they do let grain through, more grain than I liked, especially using a pump to recirc.
I think prolix posted he got his perforated sheet from RS, and having looked at it, the price is better than e-bay sellers.

Alemans advice is spot on regards the commercial fb's. I quite fancied doing the slots but was worried I'd make the fb weak with too many, and with fewer, I was concerned the perforated sheet may have more open area. I could have worked it out but plumped with what I new worked...cop out I know

 

[Aleman]

I do have the recommended slot measurements (Length / width / spacing) at home, and will try and dig them out this afternoon

Sorry for the delay . . . I've had to deal with a degraded RAID Array on the new PC.

The figures I have are for slots 2 1/2" long with 1/2" longitudinal gaps and an inch between 'rows' . . . Stagger every other row. Slot width 0.020" for Decoctions and 1/32" for infusion, opened out to 3/16 underneath

 

[Springer]

Thanks for the replies both.

My mash tun fb has 1.5mm holes. Morebeer fb's holes

You are right V its better to talk about fbs, false bottoms might get us all into trouble. :lol:
So it seems to me that we are down to 0.5 to .75 mm width for the slots. I will give it a go, they can always be made wider but its pretty hard to fill them in on polycarbonate :lol: (Much easier in mild steel)
I can see why the slot width is so much less than hole diameter. The opening up underneath is all about fb ( ) thickness. The thicker it is the more it will need to be opened up. I propose to just mill a channel under the slot to give a reduced thickness at the actual slot. :?
Think I will leave it at that for the moment, I was trying to be serious. :?

 

[Springer]

Well this is the finished result, didn't bother two much about spacing because I thought it might not work and the polycarbonate sheet already had some gashes in it .

Did a brew today and it worked well. The only stuff that got through, which collected under the floor was a thin layer about 3mm thick.This can't pass out because the mounting pillar has holes up from the bottom. I will drill a hole lower ,now that I know only a small layer collects, which will make draining easier.

So next step is to wire in the PID, I controlled HE manually for a trial run without too many complications :?
So I would be pleased if someone can tell me where I should be mounting the PT100 when it arrives :?

Was aiming to brew 28 litres, which is the minimum to cover the boiler element, but got confused and ended up with a about 33 litres in the boiler and about an extra 18 litres of wort still at 1010 in the mash tun. Read somewhere to throw this away when you have enough in the boiler, but it seems a waste to me . :? If I had stopped sparging earlier would I not have ended up with quite a few extra litres at a respectable gravity which would have made more beer. :? Plenty of room in the boiler for it.
Should have made 1050 but its still at 29 degrees so expect 1053 ,because I added some extra boiled water cos volume was down at 25 litresit was to wild for me , Will get the hang of new boiler soon.
Anyone know what quantity of boiled water you get away with adding without spoiling things ...... Should have let it cool but was in a hurry.
S