A PM question asked (flue curing chamber)

[AmaxB]

I claim nothing! But put this out for review...
A personal message with question asked and reply - the conversation:
Hello again, Brent.
Again I apologise for bothering you. From all your YouTube postings I see that you're quite a busy man - and a very versatile one, too. (I really am of the ethos whereby I don't ever expect anything for nothing. So, I don't mind paying for your intellectual property. Above all, I assure you that I PROBABLY won't keep molesting you).

I've PMed you because I wasn't sure whether or not the answer to my question is to be found in the FTT forum - and was trying not to look too stupid. I've read an awful lot and still haven't found it.

I have been studying your videos and threads pertaining to the construction and operation of your flu-curing chamber, hoping that somewhere I could find your actual plans for its construction. If they are indeed there somewhere I have been unable to find them. (They don't need to be actual plans - maybe there is a video showing all facets).

So, firstly I wanted to ask you if you are still successfully operating the unit. And is it doing the job intended for it?
Secondly, is there somewhere I can look at a comprehensive plan of it? I really do want to build one.

I live in New Zealand and it is not possible to buy and sell any form of tobacco (although it is perfectly legal to grow it for personal use). So, I cannot go out and purchase a bale of flue-cured Brightleaf like you guys can. I have to grow it - and cure it. I do want to grow Virginia, along with some air and sun-dried varieties.
I have built a kiln, modelled on the one that you developed. It has been great. I'm still using it as of this moment. I have thought about adapting it for flue-curing but think it might be best to construct a dedicated unit.
I think I have enough background (plus having a brother who has spent fifty years in the refrigeration and heating industry) to actually invent something like you have. However, having already seen yours it's like reinventing the wheel.
Can you direct me. And, once again, mate, sorry to bother you.
Ed[/QUOTE]

Hi Ed
No bother I do not mind helping if I can. I did post video on my chamber but not in great detail because most at the time had little faith in it's working. I myself did not know if it would turn out ok, it did.

If you intend to flue cure tobacco you must first understand the process. Many make it sound complex but at heart it is not, however there will be a hands on learning curve. I would suggest googling PDF files in regard to flue curing tobacco not on modern methods but pre 1930. This should give you a good grasp of how it was done. It will require some searching.

My chamber is more complex then need be so I will steer you to a more simple approach.

First determine how much flue cure tobacco you will grow. (a 2 year supply would be good, after curing and fermenting half can be consumed over a year. While the other half can continue to age after fermenting and yield great tobacco. The following year grow for 1 to 2 years.) This will determine the size of the chamber / house.

Second when placing a load for curing you do not want the leaves packed, you want hands of 3 to five leaves hung they can touch but not be compressed.

Third you want the leaves 3 to 4 feet above the heat source and about 2 feet open space above the leaves.

When I get to my new and final home I will build one like this - - The house:
Height 8 to 9 feet, width 4 to 5 feet, length 6 feet
Set 4" x 4" post 6 to 7 feet above grade with 2 feet in the ground forming a rectangle. Pour 3" to 4" concrete to and between the post. After concrete has cured lay block or stone 1 to 2 feet high leaving door opening. Frame a gabled roof. interior walls & roof 1/2" plywood sealing all cracks. Frame a door way. Insulate walls and roof, cover walls and roof with plywood. Seal cracks shingle roof and paint walls. Construct an insulated door with small window to fit door opening.
Cut a 3" x 3" opening at each gable near the ridge and create a sliding gate to cover the openings. Cut two more opening near center at the block on the long walls each with a sliding gate. Run power to the house and install 1 outlet to power one large griddle (this outlet could be controlled via temperature PID and thermal censor stopping the need to open the door).
Buy a wet bulb and dry bulb place at the window in the door (allowing you to eye temp and humidity.)
The 3" x 3" opening are to create draft.....
This will work but will need a little practice. To get practice try large leaf weeds if you have any around and save tobacco.
As with all tobacco processes you must understand what needs to be done and then do it to learn.
Hope this helps
Brent[/QUOTE]

Brent -
Thanks for your courtesy. Your advice is very useful.
As I understand it, then, you are suggesting a scaled-down old-school flue-curing barn.
I certainly understood the principle of your original 'flue-chamber' but it was the 'automatic' purging of humidity that I couldn't quite follow.
So, talking 'old-school', would you just monitor it closely and manually open and shut vents to maintain the desired humidity? Am I correct in assuming that you wouldn't have to artificially introduce moisture (from a humidifier of some sort) because all the moisture needed would come from the green leaves - and basically it's a matter of getting most of it OUT of the barn?

I realise you are dedicated to sharing things. I was going to ask my original question in the forum, but wasn't sure that it hadn't been already covered and I'd missed it. And, I didn't want to personally address you because it might've put you on the spot. However,f you think your answer to me (above) might be of value to other readers, I could ask the question again in the open forum and you could paste a modified reply, along the lines of the advice you've given me.
Let me know if you think this is worth doing.
Thanks very much.
Ed[/QUOTE]

Hi Ed
If you want to post my reply feel free (I may or may not comment).

Yes it is old school and the vents are to control humidity created by the leaves.
My chamber is controlled via Temperature PID with Thermal censor and Humidity PID with humidity censor.
The Temperature PID turns power on and off to control one blast gate (with Solenoid Valve) located near the out of the blower fan and four quarts heat emitters that are located in a heat box which is located on the out side of the chamber on a chamber side wall. This box has a thermal censor, and 3" duct pipe in is on the top of the box, out on the bottom of the box. The out pipe penetrates the chamber wall at the floor. The in pipe is connected to a blower fan located on top of the chamber.
The Humidity PID controls one Solenoid Valve that operates (open / close) one blast gate located in duct work.
....................A 3" duct pipe comes through the ceiling of the chamber with a manual gate inside at the opening. Out side at the top of the chamber this pipe is fitted with a 3" TEE. The tee faces front and back of the chamber. The front side of the tee has a short section of 3" pipe with a blast gate (controlled by PID & Solenoid Valve). The Back side of the tee connects to the air in side of the blower fan (air out goes to the heat box). The piping going to the heat box has a second blast gate (controlled by PID & Solenoid Valve) located about 18 inches from the blower fan.

The blast gates can be adjusted for how much they open allowing control of air flow. If the gate on the air out side of the blower is allowed to open just a little or not at all it creates a back pressure forcing unwanted humidity to be pushed out of the pipe at the front of the tee. The gate at the front of the tee controls how much humidity is pushed out by how much it is allowed to open.
So depending on what phase of the cure you are in determines how the gates are adjusted. To maintain humidity you do not allow the exhaust gate (front of tee) to open or open little. To get rid of humidity you allow it to open more. The gate located on the air out side of the blower fan controls how much air moves through the heat box to the chamber and is controlled by the temperature PID. Which also controls the quarts heat emitters.

The whole system is nothing more than an air flow loop with exhaust and heat capacity.

The Blower fan runs constant and is turned on or of via a breaker. Note: I have power from the wall going into a small panel box with breakers controlling branch circuits to lights, fan, pid/s, and etc.
The whole system must be tuned. All duct work and heat box must be insulated (heat box non-flammable / non-melting insulation). It gets complicated to build, run and can be costly. If you don't get it right you will get poor results.
This is why I suggested the old school mini barn approach. It is cheaper to build, requires less technical back ground to build, and will have a smaller learning cure to operate. Not to mention fewer things to malfunction.
In the old days a tender was needed to control the fire in the flue cure process as well as vents around the clock. Today the fire tender can be replaced with a temperature PID plus electric heat source. The vent control is periodic so one only needs to check and adjust every so many hours.

I want to say the whole point is the end product, the method is of no account. When I chose to go down this road I knew -0- today knowing what I know at considerable time and cost. I would not repeat the past,
I would go the way of a simple mini barn or chamber with modern twist.

Consider this it would be much better then what I built.
A structure with electric heat source controlled via Temperature PID and if you like vents controlled by Solenoid Valve/s via Humidity PID no air loop.

The whole Flue Curing process is nothing more than controlled drying of the leaf. What is really needed to do this? Don't let all the clutter on line cause you to do more then what is needed - keep it simple.
Once the process is truly understood the way becomes clear.
Hope I've helped
Brent

A link to my chamber build (an adventure indeed) http://fairtradetobacco.com/threads...rom-the-box-up-My-Build?highlight=flue+curing
When I move I will build a curing shed and a smoke house too.
here's to ya
Brent

 

[deluxestogie]

That was a big post.

I agree with Brent. Flue-curing is extremely simple in concept, and relatively simple in its required design elements. [Folks produced wonderful bright leaf with log barns, and wood fires built in brick ovens. The fanciest designs you'll see in the old (19th century) literature were by entrepreneurs hoping to hoodwink trusting tobacco farmers into parting with their money.]

Since flue-curing works best when all the leaf in a single run is of the same variety, and at the same point of maturation, the chamber need be no larger than what will accommodate about 3 leaves per plant. [Five days later, you'll prime again, and re-fill the chamber.] If you plan 100 plants, then you would need room for ~300 leaves at a time. Making a chamber substantially larger than you need will encourage filling it with leaf of differing maturity, and lead to disappointment in the results.

Minimum:

• a container of adequate size
• adequate insulation / sealing
• heat source capable of maintaining 170 degrees F within the chamber
• circulation fan
• adjustable vent
• thermostat
• some method of hanging the leaf inside

Since the temp and venting can be adequately adjusted every 12 hours, automation is merely a luxury.

Where will the chamber go? Will you need to subsequently move it? Will it fit through a doorway? Should it be assembled in a manner that allows it to be disassembled?

I would go simple, simple, simple. You can always add fancy digital controls, once the basic contraption works.

Bob

 

[AmaxB]

BoB fantastic reply! You seldom disappoint I feel you have done the perfect job of summing things up.

Some how in the begging I got the impression to get a great cure I needed ultra fine control and built my chamber with the idea of obtaining fantastic tobacco.
In the end after many hours of hands on and pages & pages of reading (leading to some confusion I'll add) I realize it need not be complex.

Folks do not try to build my chamber! We are not in the commercial arena read and reread what Bob has posted above. Study the process {Time / Heat / Humidity} not the method to work the process. The product can be easily reached if the process is well understood.

Keep it simple / simple / simple...

I wish great success to all
Thank You Bob
Brent

 

[Orson Carte]

Thanks, Brent and Bob for all the information. There is much here to digest.
Have I got this right (and please correct me if I'm misguided in any part) -

Fermenting and flue-curing are very similar processes, in that they both involve the controlled heat and humidity of an enclosed, but not absolutely air-tight space.
The main difference is; with fermenting a (more or less) steady temperature is constantly maintained and the air-space is HUMIDIFIED, and kept (more or less) constant.
With a flue-chamber the green leaf is subjected to a controlled and gradually increasing temperature (ending up with a temperature much hotter than in a fermenter) and throughout the process the air is gradually DEHUMIDIFIED. It's entirely a matter of removing moisture.
Have I got this right?
For the flue-chamber I'm trying to picture, I'm considering using a completely sealed 'chiller box' (made of six inch thick freezer panels and of the approximate dimensions suggested by Brent, above) and dehumidifying it with a refrigeration evaporator mounted on the inside, connected to a condensing unit on the outside. I am told by a brother of mine, with long experience with refrigeration, that this arrangement should work and can be preset to equalise to any desired relative humidity - it will also furnish some of the heat required. (There is no need for any venting whatsoever. Water will drip out of a discharge through the wall or make its way to the floor).
The maximum required heat, (up to 165 degrees) he tells me could be achieved and automatically maintained by a quite modest heater at the bottom of the chamber (with small circulating fan/s)
I am not thinking of trying to automate the steady variation of heat and humidity. Rather they will can be controlled within the parameters of whatever is set, daily.
(Initially, before I told him about the 165 degree maximum he said if it was a little less than this it could easily be done with a small home dehumidifier - but at 165 it wouldn't last long).
Am I misguided here? Has anyone else ever tried to make this work with a refrigeration unit?

 

[deluxestogie]

I don't know that anyone on the forum (or commercially) has used a dehumidifier. I suppose it might work, though I'm not sure.

The target relative humidity within a typical (home or commercial) flue-curing chamber is determined by the moisture content of the leaf, the ramping temperature and the venting. Green leaf contains a lot of water.

Bob

 

[Chicken]

This year I will be constructing a flue curing barn based on the design of the old timers..using a l.p. gas burner for a heat source..

Hitting 165 degrees is a hard thing to do with a normal congenital heater..last year I used a kerosene heater..and was lucky to hit the 120 degree mark...

I used a extra bedroom in my house about 13' x. 10'. All framed up for my 4' hanging sticks...

It did o.k. but that bedroom is no longer empty..so it's time to build a dedicated curing area.

 

[AmaxB]

This is pretty much what I will build for my Flue Curing Shed when I start living full time in Maine
It should hold up to two tiers of leaves (100 to 200 plants comfortably per priming)

+ Frame for and pour concrete
+ Frame structure (walls & Rafters)
+ After framing hang plywood on interior walls and gable ceiling. (Seal all cracks)
+ Insulate walls and roof R-19 Insulation
+ Hang plywood on exterior walls and deck roof (Seal all cracks)
+ Lay Tar Paper and lay Shingles
+ Cut Vents and place door to seal when closed
+ Paint interior High Gloss Oil
+ Paint exterior

See photos for framing etc.
See below rough materials cost (my total will be about $1300)

I will add two interior electrical outlets for griddle/s and fan
Note: Error concrete slab needs to be 7ft x 7ft
.
.. .. .. ... .. .. .... .. ..
.
Materials Base list & C0st Curing Shed
Concrete 38 80lb bags 4.05 ea. --------------------153.90
38 - 2"x6"x8' lumber 4.43 ea. ------------------------168.34
11 - 2"x6"x10' lumber 5.75 ea. -----------------------63.25
1/2 inch plywood 20 4x8 sheets 20.00 ea --------400.00
R-19 insulation 5 Rolls 20.00 ea. -------------------100.00
Tar Paper 1 Roll ----------------------------------------19.00
Shingles 3 Bundles 30.00 ea. ------------------------90.00

Total Base Cost ----------------------$993.59

I believe I can rotate my grows Flue cure 1st year, Burley 2nd year, and rest 3rd year using this one shed for all tobacco curing.

 

[Gavroche]

http://www.boxinnov.com/un-stock-de-200-containers-40-pieds-doccasion-a-prix-casse/

 

[DGBAMA]

There are several good builds on here. A dehumidifier is probably overcomplicating things . an understanding of the stages of the curing process is more important than a perfect chamber. It will take a few runs hands on to get a feel for it.

Here is my simple build:
http://fairtradetobacco.com/threads/3064-DGBAMA-Redneck-Curing-Chamber-Build?highlight=

I had all kinds of grandiose plans to automate and make fancy but bottom line is it is simply unnecessary. The leaf contains all moisture needed, if your box is well sealed. All that is needed is a vent and temperature control. The only addition I have made is a digital pid controller.

 

[AmaxB]

There are several different builds here I agree and your's DGBama is one of the simplest I watched your thread on it. If I recall you had good results, goes to prove it need not be high dollar or complicated.

 

[Orson Carte]

I am certainly a believer in the dictum that 'simplest is best'. I am also a true beginner and merely feeling my way. In no way do I want to appear authoritative - I'm simply looking around for ideas and advice.
The only reason I'm entertaining the possibility of using some apparatus to dehumidify is because (as far as I can see) the flue-curing process is essentially a matter of heat and the removal of moisture. (Unlike fermentation, which requires its introduction).
I appreciate that, at the beginning of the process, when the humidity is naturally high, the chamber/barn could be dehumidified by simply venting. However, towards the end of the curing (the last 48 hours of stem-drying) the graph prescribes a steady humidity of about 18%. This is fairly 'dry' air and far drier than the normal ambient humidity where I live. So, how (by merely opening vents) can I make the humidity in the chamber lower than the outside air being vented-in, unless I artificially dry it?

 

[ArizonaDave]

There are several different builds here I agree and your's DGBama is one of the simplest I watched your thread on it. If I recall you had good results, goes to prove it need not be high dollar or complicated.

i might use you shed idea AmaxB, currently look at putting in a shed now

 

[AmaxB]

i might use you shed idea AmaxB, currently look at putting in a shed now

Hi Dave the one I will build if not plain is meant to stay put and a round for awhile. He hee I am a jerk at times.... I plan on kicking the bucket at this patch of ground so making a permanent structure is fine. Am thinking of top vents something like 8" H x 12" W or make a steeple on the top with vents. I like building / making things so it will be fun!

 

[AmaxB]

Orson your humidity would need to be like that or greater then the Amazon (dripping)
Short Version --The moisture / humidity will go with the heat - up and out.

Long Version:
Is the idea of a well sealed environment and vents with sufficient heat source.
Correct me if I am wrong.
Much of the moisture in the leaf body will dissipate in the color stage not all but a fair amount.
If in this stage you do not have sufficient ability to maintain humidity level as needed you will have
condensation build up on walls & ceiling. Also as you move into setting color and the drying stages.

The need for proper venting is essential.
The adjustment and location of the venting plays a key part.
Location promotes draft and the ability to remove humidity.
The number or size of vents with ability to open or close in degrees allows control of heat / humidity losses.
Heat originates at ground or near ground level as it rises it draws moisture from the leaves carrying it up and out of the chamber.

As the leaves dry you will get less and less air humidity by the time you go into stem dry it should be low.
Because of temperature you will have little to no trouble from humidity in the air that may enter the chamber.

A well sealed / insulated chamber, box, or shed with decent venting will work.
Build one, place a heat source in side shut the door and see if you can hold 180 - 190F over a period of time.
If you can you have pretty much got it.



The chart shows humidity drop.....venting control makes it work - trouble dropping humidity open the top vent/s more and [FONT=&amp]increase[/FONT] heat to keep desired temp in the chamber / shed

 

[ArizonaDave]

Hi Dave the one I will build if not plain is meant to stay put and a round for awhile. He hee I am a jerk at times.... I plan on kicking the bucket at this patch of ground so making a permanent structure is fine. Am thinking of top vents something like 8" H x 12" W or make a steeple on the top with vents. I like building / making things so it will be fun!

`
i like that

 

[Chicken]

If I can remember..tonight I'll post some pics of old curing barns in my area..I've got lots of them..maybe new ideas will emerge..when u see them.

 

[deluxestogie]

Orson,
For many flue-curing chambers, the vents are fully closed by the time you get into stem kill. In fact, many chambers can't reach the required temp with an open vent. As Brent points out, if you just follow the temperature stepping graph, the leaf will be dry, dry, dry.

Bob

 

[AmaxB]

Hi Chicken how are ya...........your post caused me to google search images curing barns. Found a very good PDF file ref. flue curing (see link below) and many pics of barns.
I would recommend reading it for those new and are going to flue cure. The first 1st page gives a sort of step by step instruction.
Yet another chart - simple easy to follow.
.
Just tossing this out - My chamber is about 4feet x 4feet by 5 1/2 feet high (inside) with one small electric griddle I can maintain a 300F temperature it takes (empty) about
an hour to get there. Full of tobacco I can reach and hold 120F in 1 hour 20 minutes.

When I build my curing shed I'll have two electric outlets. These outlets will be controlled by means of a temperature PID. I will have two griddles their temperature control knobs will be turned to high and left there.
They in turn will be plugged into the outlets. The outlets will be energized or de-energized by the PID as it draws temperature readings from it's censor. The censor will be located about one foot center above the tobacco.
I push the used of griddles because I know through the use of one that they use little power in a well sealed / insulated environment and it is dry heat. I will also have a small fan on the floor to move the heated air
around below the tobacco leaves keeping heat even below them. The fan will turn on when the griddles turn on. I will also use a cheap second temperature PID with a second censor to counter check the first control
PID.

How a PID control works- it has on it's back side connection screws. Two or more for censor/s, two or more for power out (low voltage usually) and two for normal voltage AC or DC in. It may have more for other things.
The voltage out usually goes to an SSR relay the SSR relay will have four connection screws, one side low voltage connected to the PID, and two for normal AC / DC voltage this voltage would go to what it is
you want to turn on and off (automated). The SSR is a switch of sorts. A PID can cost as little as $15 or as much as $hundreds. An SSR can cost a few dollars or as much as $45. Thermal censors can cost as little as
$2.50 and up. Wire length and type will dictated cost at this link you can find many K type Thermal Couple Censors, extension wire, plastic couplers (connectors) thermometers etc.. Get one for air temp. not liquid.
http://www.ebay.com/sch/i.html?_from=R40&_sacat=0&_nkw=thermocouple+k&_pgn=4&_skc=150&rt=nc

PID temperature link http://www.ebay.com/sch/i.html?_fro...RS0&_nkw=temperature+controller+110v&_sacat=0

SSR relays link http://www.ebay.com/sch/i.html?_odk...A0.H0.XSSR+relay.TRS0&_nkw=SSR+relay&_sacat=0

Dave when you build your shed make a photo log let us see what you have done and how it works out for you...please.

The PDF File https://pubs.ext.vt.edu/436/436-048/PDF_61-64CuringTobacco.pdf

Brent

 

[Orson Carte]

Until I actually build it and try it I am only working from gut instinct. It's just that I thought that if you were trying to dry the leaf with wet air, being drawn in from outside it would be a little like trying to dry yourself off after a dip in the pool with a wet towel. As Brent implies, maybe the heat itself takes care of that.
I am still seriously entertaining the idea of using an (almost) airtight walk-in chiller and I don't think achieving 180 degrees will be a problem. It's the perfect size, all the insulation is already there and in the tobacco 'off-season' (which is most of the time) I can use it as a meat chiller. So, if I can maintain temp and humidity simply by using vents I'll be really happy.
The only other thing that I'm am wondering is whether or not a flat 'roof' (ie. the top of the chiller box) will somehow stop a venting working, as it might in a gabled roof. In other words, is the gabled roof part of the 'magic' or only there because it sheds the rain?

 

[DGBAMA]

The "magic" of reducing humidity, is physics of the temperature increase. Given a sealed box, humidity goes down as temperature goes up.

Humidity here where I am can be routinely 70% late summer during curing time, and with the high temp of flue curing, it is easy to reach 10% rh within the chamber by the end of the cycle with just heat and vent.