Domed False Bottoms - How Domed Is Too Domed?

[MHB]

That's the type of thing yes, there is also a 9" (200mm) version (quick search found it in both shops) that really is pretty good for most tuns and a couple of dollars cheaper, pictured in links are both American (I think More Beer) models, Keg King has a less expensive option, but on balance I would opt for either of the American made ones if the budget can be stretched as they are far stronger and have a much better connection to the outlet hose and as earlier it's a once in a lifetime outlay.

I would very specifically ask whoever you choose to buy from, which model you are getting as the delivered model has on occasion been a Chinese one rather than the anticipated American one, not having a shot at Ross or G&G, but ask the question whoever you choose.

Walling applies equally to any mash tun, if you are sparging, not for batch.

Mark

 

[manticle]

Yeah saw the 9". Figured it was for smaller tuns than I'm aiming for hence looking at the 12.

Neither outlay is excessive* so it comes mainly down to strength (as mentioned - I watched a perforated bottom get squashed under a double batch of rochefort 10 homage last year which has been my main hesitation behind the perforated model). If the US ones are sturdy, that might be the best option.

*Both less than 70, GG specifies it is US and if I buy new SS from a hospitality shop, it will probably be at least $40 -$50 for the item alone.

There's pleasure in building things myself and kind free offers from AHB members to consider as well - ultimately though it will come down to getting my new brewery set-up and running in the quickest possible time.

Cheers for the replies.

 

[QldKev]

Being in from the edge avoids channelling; it's just so much easier for the wort to travel down the wall than through the bed that it's worth making the wall path longer to compensate.

Mainly it's about Void Space, the total area available to filter wort through. Good Perforated Plate should be about -⅓ not there so a 20cm FB would be presenting a 7800 to 10,000 mm2 void and that's very evenly distributed, to get the same with a 1mm slit it would have to be 7.8 to 10 meters long. If you haven't done much metal (particularly Stainless) cutting it's a prick of a job.

If you were making cuts in a 200mm dome and you used 3 lengths for obvious reasons, the average length would be (say 80, 60 and 40mm long) 60mm that's 130 to 166 cuts or one starting in every 4-5mm around the circumference.

I really think the commercial domed ones work a lot better than any other option, you really notice the difference when you sparge (Fly but that's redundant) if you only ever want to batch sparging its pretty much irrelevant what you use.

Mark

Trying to fix formating
M

Trying to follow exactly what you said. My understanding is the term void space was used for the area contained under the false bottom, and not the surface area that is available for the filtering. Maybe this is a hang over of my knowledge from other fields where the void space is the area/cavity between outer and inner skins. Anyway more interested in the comment about the total cutout area for the false bottom in regards to filtering. As you see in my pic above I don't have a huge cutout area for filtering. I do have what I would call decent flow, and am hitting consistently 85% pre-boil efficiency. Do you think putting another slit in between the current ones would improve anything?

QldKev

 

[MHB]

I have always called the space under the false bottom Dead Space I doubt the world will end whatever term you choose and I have seen both, just find Dead more indicative of what the space is good for
How much void space you have is so open to discussion that, well so long as it is more than the area of the ID of your outlet you might not see a huge difference, when everything is going well.
The smaller the void, the faster wort has to flow through it, the more prone it is to blockage, the bigger the chance of a stuck sparge.
The more evenly the void is spread across the bottom the lower the chance of channelling
The deeper the bed the better the filtration, (within reason) the slower the flow of wort at any given point over the FB... the higher the suction...

If you have a look at any small commercial breweries the floor of choice is mostly wedge wire at 1/3-1/2 void and as the beds are usually 600-900 mm deep the wedge wire often extends to the edge. Bigger High Speed Lauters tend to have shallow (300-400mm) beds and floors that cost a bomb, I remember looking at the floor in the brewery at Malt Shovel (a thing of beauty) Chuk Hahn said it cost some ridiculous amount of money (around $50K IIRC from 10 years ago) just to have it slotted.
Im not saying its a right/wrong answer just that my first choice would be the best false bottom I could reasonably afford; and that to my mind that is a commercially made domed SS FB at $50-$60 is a good investment.

 

[jyo]

There's pleasure in building things myself...

Completely agree, so don't feel at all obliged to take the falsie, mate.

Cheers.

 

[hoppy2B]

A couple of pics showing the keg top I was talking about last night Manticle.
I cut a series of slots around the perimetre so as to make it possible to bend down the side wall which is sticking up at 90 degrees. I will need to hammer around the edge because the slots don't go all the way through and the metal will need to be stretched as it increases in circumference. I might drill some holes in the middle of the dome. Not sure yet.
I think most people just use a flat false bottom made from commercially perforated stainless with this sort of keg. Sits nicely on the recessed keg bottom.
This is taking ages to do especially as its a first time thing and I'm learning along the way. Also trying to do it neatly because I don't want it to look shit. :lol:

 

[Acasta]

Hey Manticle,
I've got a keg top cut-off also your welcome to have. Its about 25cm diameter, a bit more dome shaped then the above which may be more useful.
PM for deets.

 

[Muscovy_333]

The bowl would work, the only issue I can see is being tallish and fairly light you may bump it easily when stirring the mash and let too much grain underneath.

My false bottom is a domed keg bottom, with slots cut with a grinder using the finest cut off disk I could find. I love it, no issues with clarifying the wort and never had a stuck mash even with the march pump running with the valves fully open.

View attachment 56852

My pickup is through the side of the false bottom. Normally I would just go through the top using a 90 elbow and via a hose tail into some heavy duty silicone hose to the tap. Then for clean ups just pull the hose off the hose tail and remove the false bottom. Mine is through the side of the bottom as it houses a temp probe that sits directly above the concealed element (internal RIMS). I pull the entire assembly out the side using a compression fitting. Also I have kept some height around the false bottom to clear the concealed element, which you would not need to worry about.


I would jump at the offer from jyo.

edit: For size reference, my mash tun is 100L.


QldKev

Manticle, my falsy is exactly the same as Kevs. I cut the base out of old keg, cleaned it up so it would fit back inside the kegtun, hit it with a 10mm cutting blade in the configuration you speak of to drain and dropped in in as teh falsy.

I have inverted my keg and fit a tri-clover fitting through the sanke outlet. No dead space at all. It is a new set-up for me, but the first 2 brews on it have hit all the targets nicely. Happy camper.

 

[dicko]

If you are concerned about a FB collapsing you could fit the pick up pipe so that is just off the bottom of the mash tun. It would provide support if the weight of the grain is too heavy.

see pics



By fitting the pick up this way you also eliminate a lot of mash tun dead space. I have mine calculated at .5litre and that is generous.

Another option is to just use your existing manifold or make a new one from S/steel tube (not that expensive).

The FB in the pics above is an aussie 12 inch one from Beerbelly for about $55 and for that price I couldn't see the value in fu*ki*g about.

I do realize it is fun to make bits for a brewery so the choice is yours.

Cheers

 

[manticle]

A couple of pics showing the keg top I was talking about last night Manticle.
I cut a series of slots around the perimetre so as to make it possible to bend down the side wall which is sticking up at 90 degrees. I will need to hammer around the edge because the slots don't go all the way through and the metal will need to be stretched as it increases in circumference. I might drill some holes in the middle of the dome. Not sure yet.
I think most people just use a flat false bottom made from commercially perforated stainless with this sort of keg. Sits nicely on the recessed keg bottom.
This is taking ages to do especially as its a first time thing and I'm learning along the way. Also trying to do it neatly because I don't want it to look shit. :lol:

Hoppy: Couldn't you borrow an angle grinder and just cut the perimeter away (eg draw and cut a circle out of the middle?) That's how I cut the lid out of my keggle (which would have been a perfect false bottom if I'd had my brains attached at the time). Rather than try and bend it neatly and flat, just cut inside the vertical edge if that makes sense.

Cheers Acasta. Currently thinking that I'll grab your keg thingamy, have a crack at cutting some slots and if it doesn't work out, bite the bullet and buy one from GG.

Then I get the best of both worlds (eg feel like a frustrated dickhead AND spend money).

 

[pk.sax]

Almost exactly as per dicko.

 

[hoppy2B]

Nah if I cut away the verticle edge my false bottom wouldn't be wide enough. It needs to be at least approximately 38cm. The domed portion with the verticle cut away would only be about 28cm. Just won't work otherwise.

 

[manticle]

How wide is the vessel you're putting it in?

As mentioned above, it doesn't need to go all the way to the sides of the vessel and it's better if it doesn't. MHB earlier suggested 50-100mm all the way round

 

[hoppy2B]

Its not a flat bottomed vessel. I'm using the keg I cut if from and the bottom is recessed similar to the top.

 

[QldKev]

I have always called the space under the false bottom Dead Space I doubt the world will end whatever term you choose and I have seen both, just find Dead more indicative of what the space is good for
How much void space you have is so open to discussion that, well so long as it is more than the area of the ID of your outlet you might not see a huge difference, when everything is going well.
The smaller the void, the faster wort has to flow through it, the more prone it is to blockage, the bigger the chance of a stuck sparge.
The more evenly the void is spread across the bottom the lower the chance of channelling
The deeper the bed the better the filtration, (within reason) the slower the flow of wort at any given point over the FB... the higher the suction...

If you have a look at any small commercial breweries the floor of choice is mostly wedge wire at 1/3-1/2 void and as the beds are usually 600-900 mm deep the wedge wire often extends to the edge. Bigger High Speed Lauters tend to have shallow (300-400mm) beds and floors that cost a bomb, I remember looking at the floor in the brewery at Malt Shovel (a thing of beauty) Chuk Hahn said it cost some ridiculous amount of money (around $50K IIRC from 10 years ago) just to have it slotted.
Im not saying its a right/wrong answer just that my first choice would be the best false bottom I could reasonably afford; and that to my mind that is a commercially made domed SS FB at $50-$60 is a good investment.

Thanks for the info. Touch wood I've never had a stuck sparge since setting up this system, and never needed rice hulls. But as you've mentioned seeing as the big boys see it beneficial to ensure a uniform flow, I think I may cut a couple extra slots in the falsely. Fingers crossed it will allow more flow through the pump and help stabalise the mash bed temps faster during ramping.

QldKev

 

[The Village Idiot]

Gents,

I use a round cooler and a round domed false bottom with a short silicon hose between the falsy and the outlet. I have had problems with the falsy lifting or being knocked when stiring the mash. Pain in the ass and a messy fix when nothing comes out the bloody tap. Any suggestions on how to fix the falsy to the bottom of the round cooler?

Peter

 

[Acasta]

Cheers Acasta. Currently thinking that I'll grab your keg thingamy, have a crack at cutting some slots and if it doesn't work out, bite the bullet and buy one from GG.

Then I get the best of both worlds (eg feel like a frustrated dickhead AND spend money).

No worries, I got an angle grinder and a few tools so I could try giving you a hand.

 

[booargy]

If you are going to cut a keg top or dome use this pattern. this is the same pattern used in the 200L braumeister except it doesn't have full length slots. It originally had half the amount of slots and worked well. Now it has a piece of screen underneath it and works a lot better.

 

[hoppy2B]

If you are going to cut a keg top or dome use this pattern. this is the same pattern used in the 200L braumeister except it doesn't have full length slots. It originally had half the amount of slots and worked well. Now it has a piece of screen underneath it and works a lot better.
View attachment 56876

You seem to have captured the essence of 'I don't want it to look shit' pretty well there booargy.

lol, yeah just kidding. It took me 2 whole days of work with the hacksaw to get mine slotted around the perimetre. I'm hopping I can follow the lines if or when I go over it with the angle grinder.
I have an angle grinder Manticle. I wish I had a dremel like you. <_<

 

[booargy]

a dremel won't do the job
a 1mm disc is about $2.70 by say 6 discs = (12+4.2) 16.20 under $20
use the worn discs on the shorter cuts.
score the cut with the grinder before you start. for round holes score the cut and then gradually work the cut evenly through. as you cut leave tags like model parks to support the scrap. on a round cut you will use more discs