Wood burning efficiency

[Brent]

I have been heating our 4200 sq ft log home ( not especially the most efficient thermal construction ) for a few years now with one large high efficiency wood stove and along the way have learned a bit from some miscues. The efficiency difference between our eveaporator, a 2 x 6, and the wood stove in the house is astonishing. The wood we go through on the evaporator in 10 or so days of boiling, is roughly equal to what we burn to heat the house ... about 3 1/2 bush cords.

I recently found a document on this subject at the University of Missouri-Columbia that sheds a lot of light.

When I had a Half Pint we started just lighting the fire and letting it burn. Then with some ideas from Maple Trader I added a blower. It boiled a fair bit faster, but went through 3 x as much wood. Now with the beautiful Phaneuf evaporator and its deep flues, we're using the same amount of wood and boiling 3 x the sap.

But the woodstove we use has a solid fire brick bottom, no grate. Air comes in through jets at the top, and it heat the whole house. One wheel barrow of wood for 24 hours. On the evaporator I think its a wheebarrow full every 45 minutes or so.

So here's the key section from article from the Univ of Minn.

=======================
" The old technique of admitting room air under
the fire and letting it flow up through the fuel bed
and then into the chimney flue is inefficient. To heat
efficiently, combustible gases released during the
burning process must be mixed with ample oxygen at
a minimum temperature of 1,100 degrees.
For complete combustion of the wood gases, supply
about 80 percent of the air needed over and
around the fuel. The desirability of having air supplied
over the fire bed has led to the design of
“down-draft” combustion heating units. Such units
force combustible elements to pass along a circuitous
route where they are mixed with a current of hot air
and nearly all burned. In less-efficient units these elements
escape up the chimney or are deposited in the
flue in the form of soot and creosote."
==========================================
I have found that shops that sell fireplaces and woodstoves sell spares and I spied in one a stainless tube that is 25" long with a couple dozen holes. Perfect for a 2' wide arch. We will see what it does in a few weeks. I have more taps this year than last (first tubing going up now ) so I hope I will use the same wood and get more heat out of it.

The bottom line, pun intended, is don't blow the air in the bottom under the wood.

Here's a link to the full article

extension.missouri.edu/explorepdf/agguides/forestry/G05450.pdf

lots of interesting numbers on moisture content etc.

Enjoy

PS if you're intersted to see the stove we use in the house it is the Blaze King "King Classic"
http://www.blazeking.com/wood-stoves.html

[swierczt]

I found the same thing with my barrel evaporator....I added a blower under the fire, every year making more or bigger holes and higher rpm blowers. I did boil more sap, but used disproportionally more wood. I was thinking of trying a little of both techniques this year. A blower below the grates as well as one above, just below the pans to try to relight the gasses. I'm not sure of the ratio of air on the bottom to the top, but from your article, it looks like more above the fire is better...but I find it hard to believe that the nearly white-hot bed of coals that I see just above the grates and bottom blower is a bad thing!

[dano2840]

the difference between your stove and your evap is that your stove is considerably limiting its air intake, your evap give the fire all the air it could ever need, its like when your getting your fire going in your stove and you open the door about an inch to get the draft going, thats what your evap is doing all the time, if you left your door open for an 45 min you would probably burn through that barrow full of wood, or close to it, just another way of thinking about it. we just bought a new hearth stone stove which has a catilitic converter which re burns the gases and does an amazing job, puts out 2x the heat on the same amount of wood - the creosote

[Brent]

when I had the Half Pint going with a blower, boiling on the porch in the dark, the bottom 3' or so of the stack would glow cherry red. That heat did nothing but give Al Gore something to complain about. All up into the atmosphere.

I want and expect to get a really hot fire UNDER the pans, not up the stack.
The problem with most evaporators is that the wood gases do not get burned.

If you spend a lot of money and get arches with names like inferno or volcano, they inject air above the wood. Some through port at the tops of the doors, some through tubes at the top of the slope at the front edge of the flue pan.

This is the effect I'll try to create, I want heat with minimum draft. I don't want 1600 degrees in the stack ... that's no darned good up there.

[Brent]

swierczt

I'm thinking that a modest amount of air blown in at the right place ( wherever that is ) above the wood, may be light enough to not to cause any back draft out the front doors. Last year I got to 1300 degrees in the stack without a blower anywhere, but I had to have good wood and load a bit every few minutes to get that. A bit of wet wood and I was down to 1050 to 1100 in a hurry.

The first place I'm going to try is the top of the slope, just before the flue pan. Then I may move it to just above the door, blowing down into the flames, or maybe both. At some point its going to cause back draft. It will take some experimenting.

[802maple]

As the orignal designer and inventor of the Intens-O-Fire evaporator that CDL sells, it is interesting how close my numbers and University of Minnesota are.
My design called for 75% over the fire and 25% under the fire, which will give you an efficiency rating in the high 70's. Any turbulence that can be caused by fresh air over the fire will imcrease efficiency. That is why the air is added mostly to the back side of the fire box. For a wood fired evaporator to become much more efficient there will have to be a total redesign of the pan system, because to much heat is lost up the stack which is required to maintain a complete boil of the present design. The new pan design will have to recycle the lost heat that escapes us now.

Anybody that wants to build a efficient arch should look at a Intens-O-fire by CDL or a Hurricane by Lapierre as they are the most efficient out there. The others such as the Inferno rely on to much air under the grates.

[swierczt]

Brent, and 802maple

That's always been a concern of mine. I've read a few threads here about adding air into the firebox and everyone always says most people don't add enough. My concern is when is it too much and can this create a dangerous condition for a backdraft or something else?

[Amber Gold]

How do stack temps compare of oil fired vs. wood fired arches?

After this season I was thinking of taking those perforated tubes and running those along the top of my firebox and seeing how those effected my boil rate. I didn't realize you could get those tubes through your local hearth shop. Do you have an approximate cost for those?

[802maple]

With forced draft you should create somewhere between 3 and 5 inches of positive pressure anything beyond that and you start to push to much heat up your stack. The optimum temperature at the stack is 1000- 1100 degrees.

It will not cause a back draft, but you will need to close the air down some or all the way off while firing depending upon the stack size and amount of natural draft.

Many arches that have just bottom air have to put so much air to the grates to get a good fire that if you were to measure the amount of positive air flow it would most likely be in the area of 10 inches. thus blowing all your heat up the stack. With the proper amount of top air all you need for air under the grates is to maintain a fire and let the top air do the adding of air to burn all the gases. When all of the air is added underneath, it is all burnt up by the time it hits the gases and then you will have a ineffiecient burn.

[Jeff E]

What about the point about heating the air before it is released into the fire box, such as running the intake under the flue section of the arch so it is heated.

Would there be enough negative pressure from good natural draft to draw air into intake ports in the angled section of the arch without adding a blower?

[Brent]

Josh
the local shop is charging me $ 50. Maybe a bit stiff. We sell machine tools for a "day job" but finding a heat resistant allow, buying a short cut peice and messing around just was not worth it.

Here's link that could be helpful. The url says it all
www.stovepartsunlimited.com

[Brent]

802Maple

the lesson of turning off the blower before firing is one that gets learned real fast. I've got a neat little blower with a speed control so I can play around.
The natural draft with the door wide oper is awesome. Just step outside and watch what come out of the stack.

Reading that article I noted in the fist post here sheds light on how charcoal is made. Cook the wood without oxygen, using the captured gasses to cook the wood.

If you watch flames you see that they seldom originate right at the surface of the wood. They start 1/2 to 1" above the wood. So maybe the wood is really not "burning" but being roasted and giving up the wood gasses and it is these burning gasses that we see, and the end of the flame is where the Oxygen runs out. The wood does not really burn until it has given up most of the "wood gasses" and then we have coals that burn like charcoal.
Hmmmm. Maybe more than we really wanted to know or speculate about.
But it all makes sense to inject oxygen and mix it in a turbulence to get all the energy released under the pans and not blow it up the stack.

[nymapleguy607]

So I am also pondering the idea of using air above the fire but my only issue is how far below the pans do you put the air nozzles. It seems to me that unless you were preheating the incoming combustion air then you might have a problem with 1. getting a good mixing of the oxygen with the gases given off by the wood and 2. If the air nozzles were to high and you weren't preheating the air then you might have "cold spots" under your pan. These are my only concerns.

[Brent]

Jeff E and nymapleguy607 Jeff

you guys seem to have the same concern about injecting cold air. We have an expert in 802maple. From what he says you want to create turbulence to mix the fresh air ( oxygen ) into the hot gasses. So I am planning to point the jets essentially downward to make the mix. I think the tube will be very hot and by the time the air passes through it the temp will be up. I could well be that if we keep the bottom draft a bit restricted the natural vacuum from the stack, will be all we need.

[802maple]

You could get a certain amount of air thru natural draft but not enough to cause turbulence.
The outside air will burn the best as it has the most oxygen. I have made several archs and some people did not want to listen to the high pressure blowers that I installed in them, so they put them out doors after I recommended it and they were pleasantly surprised with the better fire.

It isn't necessary to buy special castings to make your air nozzles and such as you can wrap it with ceramic blanket. I use 3x3 x 1/4 inch thick square tube stock with 1/2 inch black pipe welded on for my nozzles and then I wrap with 2300 degree 6lb blanket. I weld 1/4 by 1 and 1/2 long stainless bolts on the tube and then use a stainless nut and fender washer to secure it. It is a lot cheaper then buying the pins from the maple equipment guys.



What about the point about heating the air before it is released into the fire box, such as running the intake under the flue section of the arch so it is heated.

Would there be enough negative pressure from good natural draft to draw air into intake ports in the angled section of the arch without adding a blower?

[Bucket Head]

Can anyone post some pictures of the injection pipes that are availiable?

How about some pictures of their arch showing where the air in coming in?

Does anyone have an an Intense-O-Fire arch that they could photograph for everyone?

I would love to see this type set-up. I have spent quite a bit of time modifying and enhancing my blower (under the grate style) for this season. I wish I could have seen this new type set-up sooner.

Steve

[Bucket Head]

802,

What direction were the nozzles pointing on your square tube manifold?

Also, a standard furnace blower (squirrel cage type) would not provide enough air for a manifold?

Steve

[WESTVIRGINIAMAPLER]

Jerry,

Also, how far below syrup pan should the air being injected over the fire and I am also curious how much angle the nozzles should have pointing down??

[802maple]

If you go to Breezy Lanes profile he has picture's of his arch I believe.

I bring the back air nozzles up as close as I can to the bottom of the flue pan, pointed forward and down at 10 degrees.

In the front I have a 3x3 tube that is part of the door frame accross the top with those nozzle pointed to the back and down at 10 degrees.

The nozzles in the door are pointed straight back.

Someone should have one close by as there has been a lot of them sold since I built the first one 13 years ago.

The hurricane arch by Lapierre is very similar

[802maple]

Ryans arch is built differently in the back because it is the newer design. The orignal arches were made more like the typical arch with galvanized or stainless sides and all of the ductwork was out of 3x3. This arch is made out of sheet steel and painted and the ductwork was made right into the arch. All of the seams are welded so as to make a totally airtight unit. You will notice that his grates are made out fire brick and drilled with 3 three quarter inch holes in each one. This is the least expensive by far and just as dependable way of making grates, I have done this for years and they do not break. and with fewer holes it will cut down on how much air is allowed under the fire.

Ryan opted to not have any stainless on it to reduce cost. The only thing stainless does on this arch is make it look pretty and he thought he would rather spend the additional $1100 in the woods.

[Gary R]

802Maple,

Thanks, as being new to this, I was unaware of your expertise. I should have asked more questions over the summer. My high efficiency wood burner has most of the flame at the ceiling also.

I wonder why the cataloge's call their grates wood savers. I built my air injection this summer with air under the grates only. I have only fired it for a few hour's. Sure it boiled better. But, I was chucking wood into it fast! I may not take the time to rework the air injection this season. I will work on it in the off season. I think in the last post you explained it very well as how to set up the nozzles.

Thanks again:)

[Bucket Head]

802,

I looked at breezy Lane's photos. Now I have more questions.

Air does not need to be injected at the sides of the fire?

How is the air plumbed to the door?

Are the rods on the side for controlling the air? What needs to be controlled, or directed?

What does the air source look like? A regular furnace blower would not supply enough air?

I would like to try this type forced draft, but I would like to see more photos if possible.

Thank you for the information you have supplied so far.

Steve

[802maple]

I will try to answer your questions

I have been thinking about the same thing as far as injecting air at the sides, but as of yet have not experimented with it.

The air in the doors comes thru the hinge box that is on the left side of the door, you will sse them in a couple pictures.

The rods on the side do control the air to the fire. One is for the bottom air and the other is for the the rest of the arch. It is all by the seat of the pants as to where air is controlled as diferrent wood burns differently. Dry wood doesn't need as much air to burn so you can cut down on bottom air and it doesn't create as much much smoke so you may not need as much top air either. Also local draft has an effect. Most sugarmakers find that there is setting that works best for them and they may never have to reset it.

The air source is a high pressure blower that I purchase from Grainger. High pressure blowers are required to feed this arch as regular furnace blowers do not work well trying to force air thru all the duct work that is in a Intens-O- Fire. You get very lazy air.

I will see what I can do about pictures, but I don't have much for pictures in the build stage so that you can see the process.



802,

I looked at breezy Lane's photos. Now I have more questions.

Air does not need to be injected at the sides of the fire?

How is the air plumbed to the door?

Are the rods on the side for controlling the air? What needs to be controlled, or directed?

What does the air source look like? A regular furnace blower would not supply enough air?

I would like to try this type forced draft, but I would like to see more photos if possible.

Thank you for the information you have supplied so far.

Steve

[Amber Gold]

I wish I had more time before the season started to do some modifications to my air system. At this point I'm stuck with the bottom air only.

$50 for those perforate tubes doesn't seem bad compared to the woodsave package which is about $1000. I was thinking of just taking some 1/2" steel pipe and taking my drill press to it.

The Bascom's catalogue claims something like 15% increase evaporation rate and 15% reduction in wood consumption. Not sure of the exact numbers, but it was something like that. Is this incorrect? Is it more like 15% increase evaporation rate with a 20% increase in wood consumption?

[Amber Gold]

What does Breezy Lane get for an evaporation rate? Also what's the approximate cost of an arch like that?

[802maple]

Getting much air thru a 1/2 inch tube will be very difficult. Alocal tried with 1 inch and didn't have much success.


Ryan gets about 100 plus gallons an hour with about as much wood as you see in the picture. He doesn't build a big fire as this keeps up nicely with his RO at that rate. If he really pushed he would be in the 120-30 an hour, not bad for 2.5 by 8.

He built this one with a little guidance from me for about 2500 complete of which there was a 600 dollar blower in that price.

[Amber Gold]

I just reread the thread about using the box section as your air tube. Makes sense. If only I had more time...

He does 100 gph with that little pile of wood in the firebox...amazing. I have a 2.5x8, imagine what I could do with over 100 gph...

Did he build it himself for that price or did someone build it for him? Can I modify my Grimm arch and get the same effect and comparable boiling rates?

[802maple]

He built it himself as he is a welder.

[nymapleguy607]

So I am just wondering what is the real advantage of using a high pressure blower over lets say a large squirrel cage blower. I looked at the Cfm's of the high pressure blower and I thought they were close to what a squirrel cage blower does. Can someone set me straight on this
Thanks

[Bucket Head]

Is the high pressure blower similar to the ones that are supplied with the "bubbler" pan injectors? The one I saw looked like a giant hair dryer.

I know some folks who built their own, and they used a good sized shop vac motor. The type that be reversed so you can either vacuum or, say, blow leaves with them.

802- I know squirrel cages move a lot of air, but they lack "power". The "lazy air" is a good description. I know it would not be high pressure, but what if a squirrel blower was ducted directly to the fire wood, just above the grate? Say equally on both sides of the fire, not front and rear? Just wondering out loud here.

I look forward to any pictures you could provide of your set-up, or ones you helped out with.

Steve

[802maple]

If you go to the Grainger site and search for the 4c129 blower, that is the one I would use on your evaporator.

Your idea might work, you certainly would want to put some kind of damper system in so that you could guage the air flow. All I can say is give it a try. This is how things are improved, if you saw my first evaporator prototype, it would only be something that only a mother could love.

Since I have sold my operation, it will be hard to get pictures of it, but I will see what I can find. If you look in a Maple Pro catalog, the intens-o-fire that they are now selling works on the same theory, they have just dressed it up so it is prettier then the orignal that we built for them. They like them to be shiney and expensive, I like them to work.
It is kind of like the stock car that I crewchief for, my driver wants it to be pretty, so he spends all of his money doing that, then he wonders why some cars have an advantage on us. My answer is well it is the prettiest 10th place car out there.

[Bucket Head]

802,

Keep looking for pictures! Ask the folks you know that have this style forced draft if they have some pictures they could share.

Unfortunately, I'm just finishing up my "new" air tight ash box and front, along with installing the blower duct I had made. I'll have to go with this set up for this season now.

I say unfortunately because I certainly would have done things differently after hearing what you and the others have said about air over the grates instead of under it.

It is food for thought though. Some pictures would help me get an idea going as to how I could modify mine to get air above the grates. The challenge will be getting the plumbing right.

Steve

[WESTVIRGINIAMAPLER]

I will have to say Jerry's idea of grates work great. I made up a set for my evaporator last year and they work great. My evaporator started out as a stock 2x8 and then I converted it to an inferno arch. My has the square sides and only difference between my an inferno is that is has a galvanized or stainless floor under the grates and mine has a 1" ceramic blanket floor. By converting over to this and the grates that I got from Jerry's idea he gave me, I have my 2x8 running 60 to 65 gph including startup and shutdown and would imagine there were plenty of hours during peak boil last year it was well over 70 gph as most of my boils are at least 8 hours or more.

I hope to add air to the sides and rear of the arch in the next year or two and redo my arch and hopefully increase the evap rate more. I am using about the same amount of wood per gph as I was when I was averaging 35gph, so this is a good tradeoff for me and after I add air over the fire, I hope to be at least double the 35gph rate I boiled at the first year it was stock. Since the stock evaporator, I also added a preheater, but I don't think it has increased the gph rate more than 10%.

You could probably count on 1 or 2 hands the number of guys in the entire industry with the wealth of knowledge and expertise that Jerry(802maple) has.

[802maple]

Thank you Brandon, you make me blush. It certainly wasn't because I was born that way. I have had some great sucesses but along with each success came a larger amount of failures. Most of that was due to never being satisfied and listening to whole bunch of sugarmakers that were alot smarter than me. I loved physics in High school and basically all sugaring is about is physics. I was also fortunate to be a fourth generation sugarmaker, with a wealth of knowledge above me. It was easy for me because of that, what really impresses me are guys like Mike Christian, Theron Pierce, Matt Roy, Brian Ryther and you Brandon, plus so many others on here that are taking the leap of faith and trying to better their operations. If I tried to mention everybody it would probably close the site down.

Tap on, boys, tap on and if I have an answer I will try to help and if not I will BS my way thru.

[nymapleguy607]

I found this site when I was looking for a high pressure blower for my 2x6 http://www.blowerwheel.com/blowers-pressure.htm I thought the 600CFM would be pelenty if not over kill for a 2x6 but I thought that If I try and add over fire air that the bigger the better Thankds

[Brent]

you sure will get a bigger faster hotter fire with a 1 Hp blower. But my gut feeling is that you will put most of the heat out the stack. It will be like a blow torch. You may double the rate of boil but you could use 4 times the wood. It's hard to put real numbers on this from anything I've seen. On a 2 x 6 I doubt you need much more than 1/4 Hp. and most of that should be injected above the fire.

[nymapleguy607]

Not talking motor hp but what would the range in CFM be for a 2x6. I agree that there would be alot of heat wasted up the stack with that big of a blower but I thought that it would feed under as well as over the fire without any trouble.

[Brent]

I suppose the first answer is to ask another question. What is the cost of your wood supply. Do you buy it or cut yourself, (like me and still resisting a hydraulic splitter) Cut the tree, cut to lengths, split, transport, stack and shelter etc.

For comparison I dug out the little blower that I used on the Leader Half Pint a couple years ago. It's a Fasco model 7021-10004 and the motor only draw 0.7 amps so it's smaller than the top one on the same page you linked, maybe 70 or 75 cmf. One the Half Pint it kicked up the evaporation rate quite a bit but the heat loss up the flue was astonishing. In the dark the bottom 5 feet of the stack glowed a dull cherry read. I just can't see that you need 10 times that. 4

If you don't put some special piping or ducting in the arch to get the air above the grates, your wood consuption will go up but the efficiency will not.

802Maple seems to have done a lot of testing and designed one of the most efficient wood fired arches around ( see his posts avove ) and he found you need 75% of the fresh air above the grates. The article I found from the University of Minn said 80% above. I'm putting two air injector tubes in, one above the door pointing more or less down and one at the top of the arch slope at the back, blowing downward as well. I don't think I'll need much more air than the little 60 CFM blower I had on the Half Pint. We'll see in a few weeks if the coming ice storm leaves the trees up.

[Acer]

http://www.uvm.edu/~pmrc/Combustion.pdf

Hey Admin, what about adding a library section for technical papers?


Dean

[802maple]

The main reason for using a larger high pressure blower is to create enough turbulence to make a true efficient flame. Because the blower is capable of putting out 600 cfm doesn't mean you are going to be using that much. If you wanted to you could use a 1200 cfm blower on a 2x6 and not blow the heat out the stack. That is why you control the air with dampers much like you control the air on a acetelyne torch. The main thing is you don't want lazy air, you want it to come out under equal pressure to all your injectors. If you can acheive that with a small blower then you have it made.

[TapME]

802; nice job on the design of the new type arches, always wondered who made the first one.
now the idea is to get total combustion and total use of that heat that is generated. The closest thing I can think of for an example of great combustion is the new pellet stoves that are out there. Most work with air injection but the twist is pulsating exhaust. This feature keeps some of the heat in and limites the exit of heat. Just something to think about. Thanks for letting a new bee share a thought.

[802maple]

What I find interesting is the new pellet evaporator that Dallaire has made, I understand that it is a super boiling evaporator. Seeing that I lost my design to them, I guess I am going have to do some more research in the pellet direction. But first I have one more woodfired design to test this summer, no wonder I am always broke, but it always makes for a good anchor if it doesn't work. LOL

[Jeff E]

Hey, any one simply add a smaller, pressure blower to inject turbulent air into a conventional draft system. I am thinking that the majority of the air would come through the draft/ash door, and the injected air would not have enough CFM to pressurize the arch, but specifically directed air to put turbulent O2 into the right spots to increase combustion.

[RileySugarbush]

802:

Are your nozzles just normal steel pipe?

[802maple]

Yes they are black iron pipe, protected with blanket insulation or High temp compactible refractorie cement.

The turbulent air needs to be over the fire.

[maple marc]

I know that to most of you guys a 2x4 is a toy, but it's my first baby. I'm learning a lot with it. Last year I made 24 gallons of syrup but burned 1.7 cords of wood--not very efficient. I realize that short evaporators just cannot be as efficient as your big units, but I'm wondering if tinkering around with this air injection idea might make my 2x4 burn less wood. A lot of heat goes up my 10" stack, and I generally must keep the draft door closed to prevent overheating. What if I modified the grates to allow only a small amount of air under the wood, and then ran some injectors behind the wood, pointing toward the door? How would this interact with a stack damper? How would this change my evaporation rate? On a good day I boil off about 18 gallons per hour.

Thanks for ideas. You guys are a brain trust!

[swierczt]

The main reason for using a larger high pressure blower is to create enough turbulence to make a true efficient flame. Because the blower is capable of putting out 600 cfm doesn't mean you are going to be using that much. If you wanted to you could use a 1200 cfm blower on a 2x6 and not blow the heat out the stack. That is why you control the air with dampers much like you control the air on a acetelyne torch. The main thing is you don't want lazy air, you want it to come out under equal pressure to all your injectors. If you can acheive that with a small blower then you have it made.

What problem does the lazy air create? Just curious...If you don't have enough pressure at the injector nozzles above the fire, will this take away from efficency?

[802maple]

What lazy air amounts to is just like your cutting torch when it isn't getting a good amount of oxygen. It is hot but not as hot as when you add a little more is about the best way to explain it.

[Old Farmer]

802Maple. Thanks for sharing your experience on these evaporators. I am currently using a 20" x 52" home made evaporator with flat pans. I cannot hope to get anywhere near the efficiency as the professional units do but I have been looking around for ideas to increase efficiency and boil rate when I ran across this thread. I also ran across a paper on the Proctor Maple Research Center site that might interest you. It has a lot of similar information and the authors obviously think along the same lines. I think that Acer put a link to it earlier on this thread. That paper talks about location of the nozzles in the combustion chamber and about preheating the intake air with a heat exchanger in the stack. It looks like an interesting thing to try. I don't know that I will try all of the ideas but I might try the nozzles in the fire box similar to what you have done.

The link to the paper is: http://www.uvm.edu/~pmrc/Combustion.pdf

Happy boiling
James

[danno]

I'm jumping in - hope I can get it fab'ed and installed in the next 10 days.

Just pulled my syrup pan and removed the last fire brick at the top of my slope. I'm gonna use a design similar to how my newer wood stove is set up.

Also, rebuilding the grates while I'm at it. The old ones were terribly warped with - I think - too much space for air and ash/wood to fall between. I'm going to try a fire brick bottom.

I pretty happy with my evap. rate, but burn wood like it's going out of style. Always pushed a ton of air under the wood.

Nothing like waiting till a week or two before the season starts to decide to re-design the arch;)

[KenWP]

I burnt out the motor for my air blower trying to figure out the wireing on it so will have to for go air this year. The stupid thing was on a heater and turned out that it was not 120 volts but used the left over power from the heat element to run it so full power fried the motor. owell live and learn. What I wonder is there a way to figure out how much of a opening I need for below the grate air intake for a 6 inch smoke stack to let if burn hot enough. I heat in the house with wood and to get it to start to burn hot enough I have to use the ash drawer door to get enough draft.

[Haynes Forest Products]

OH the old how big should the hole be....well every wood fired arch I ever saw had some rube golberg set up that held the door open depending on the wood the wind and the rate of boil that you wanted. Try a brick the come with 3 differant settings....ON END......ON ITS SIDE......LAYING FLAT

I have never hear of a motor that would be in series with a heat element. Is that just a CRAZY Canada thing? lets do a Autopsy.....did it stink and small and smoke? Growel and run slow? take of across the room and catch fire? Or did you do some arc welding with the wires.

[Smitty]

I'm jumping in - hope I can get it fab'ed and installed in the next 10 days.

Just pulled my syrup pan and removed the last fire brick at the top of my slope. I'm gonna use a design similar to how my newer wood stove is set up.

Also, rebuilding the grates while I'm at it. The old ones were terribly warped with - I think - too much space for air and ash/wood to fall between. I'm going to try a fire brick bottom.

I pretty happy with my evap. rate, but burn wood like it's going out of style. Always pushed a ton of air under the wood.

Nothing like waiting till a week or two before the season starts to decide to re-design the arch;)
I'm jumping in as well.The weather looks like it hold for atleast a week. I removed my pans last night, and drew up print on my new turbulant air system.
Had time at work this morning and fab'ed it up. Hope to install it on sunday.
Do'nt know what i'm thinking but after reding all the knolegde and theories on these post, i have'nt been able to sleep at nite thinking about it.

Thanks for all the thoughts and info.

[danno]

when you think of air in the firebox, make sure you think of air in the pans as well, to boost your evaporation rate. I was talking to someone about this today, and it could give you a 25% increase.

I always thought air in the syrup pan was about making lighter syrup, not increasing evaporation. Wait, I take that back. I guess if the sap is the same, the only way to make it lighter is to speed up processing time (ie. increasing evaporation rate). I have not heard much about "in pan" air lately, as darker syrups have become the rage.

[nymapleguy607]

I thought that they abanded the air injection for in the pans as most people felt it slowed thr boiling rate

[802maple]

It does not slow the boiling rate, I have seen this first hand. It does increase a wood fired arch especially if you don't keep a even fire as it keeps the sap rolling or a fake boil as I call it all the way back, all the time. I have seen steam coming off a oilfired evaporator that had been out for forty five minutes like it was in a full boil when he turned the bubbler on, and 3x12 woodfired Leader inferno that was evaporating at about a 150 gallons an hour increase to about 200 after he added the bubbler. A hard boiling oilfired evaporator or woodfired evaporator with a good firing technique will not get those kind of numbers, you might expect 5 to 10% if that. But a evaporator that doesn't boil hard all the way back will see an increase.

[Haynes Forest Products]

I have a LPHV Cambell Hausefeld paint sprayer that I dont use and Im thinking it would make a great air system for the flue pan. when it gets running for a while it pumps out hot air so it wont drag the temp down.
SETTLE DOWN FOLKS I check its a food grade paint sprayer.

[802maple]

Believe me any cold air that is pumped into a bubbler system will not be cold by the time it hits the sap. If you can heat the air than fine. This is nothing new as this technology has been used in Steamaways and Piggybacks for nearly 20 years and they evaporate sap and they very rarely get over 190 degrees

[jason grossman]

here's a question for you guys about a bubbler, we work so hard to keep are sap clean ie sap filters, syrup filters, hoods, food grade equipment, etc. why would you want to put dirty air in it??? i know they have filters on them, but have you ever seen duct work that is spotless and clean, just something to think about where is that inlet getting it's air??? and what's it being filtered with????

[jason grossman]

just thought i would pass this along. i was just listening to NPR news and they said a peanut plant in texas was shutdown, in part because they were pulling air into the factory from a crawl space above the plant that MAY have contributed to salmanilla. interesting!! food for thought!!

[birdmancf]

This question may be very naive, but I've been gleaning so much info from this site about upgrading my barrel evaporator. I was ready to put in a 3" pipe for air under the grate using a bathroom fan for a blower when I started reading this thread.

First off, would copper piping (or its soldier)for air be too "soft" and have too low a melting temp to be the delivery source for air? Second could I minimize the risk by drilling holes in the fire brick and only taking the piping part way through? And finally is adding some additional air to the flames better than doing nothing at all?

I understand the idea of turbulent flow under the pans and keeping it from racing up the stack. I believe our home pellet stove has the very same problem. All air is delivered from under the firepot, to keep the ash blown out, and not enough seems to be there for the flame unless the amount in the firepot is minimal.)
Any comments are appreciated. I know everyone is getting very busy right about now. We just had another 28" of snow on Monday so things are too slow for me, too much time to ponder and tinker.
Chris

[Haynes Forest Products]

Jason: Peanut butter is not pasturized so its important to be sterilel with everything. The commercial units filter the air with Charcoal filters.

[Smitty]

Does any one have any advice on what size tubing,hole diameter, and fan pressure (would the fan that 802 specified work) for a bubbler. And should there be one in every flue?

Thanks for thoughts.

[C.Wilcox]

Guys,

Being that this thread generated so much interest I thought I'd bring it back around again. My question is, did anyone follow through with adding high pressure air over their fire/under their pan as 802Maple described? If so, how did it work? Did you see the jump in wood consumption efficiency that you were looking for? What about using the firebrick grating? I believe I saw a thread where Danno said he had changed to a firebrick grating, but it didn't sound like he was terribly pleased with the results. If anyone did successfully make this work can we get pictures?

[Arctic Art]

A couple of years ago WB Mason rebuilt my 4x12 Leader drop flue arch front and made it air tight with a blower. We used the brick with holes for grates. My evaporation rate went from around 110 gph to 150-180gph depending on the quality of the wood available. I did, as has been noted in these posts, use much more wood after the upgrade. Next we're going to put some air on top to try and improve the efficiency as 802 has suggested. Here are some pictures of the first upgrade. Art

[Arctic Art]

Let's try the pictures again.

[Brent]

I lost track of this thread in the heat of the season and never reported back what happened.

At first I put a single pipe in the firebox about at the top of the slope going up to the flue pan. I had about a dozen holes in it and aimed them down about parallel to the slope. I placed small blower I had on a stand on the side and let it rip. The first thing I noticed was a change in the sound. There was a slight rumbling sound to the fire. After a couple nights I noticed that a large part of the air from the blower was not going in but espcaping around the slopping connection between the blower and the pipe, so I took it out and put more holes in it with bigger diameter. The noise of the fire got a bit louder. The stack temp was up a bit. I liked that so I put in a second pipe about 6" back from the firing doors. Both pipes were about 2" below the pans and pointing down into the firebox. With a second blower on the second pipe the fire had real rumble to it. The stack temps were up about 50 degrees and I can't quantify it but I'll swear I was using less wood. The time between firings went from about 5 minutes to 8 or so. The fire looked more white yellow than the yellow/gold that I was acustomed to.

I never had enough air pressure that I got any backdraft around the doors and rarely ever got a lick of a flame coming out when I fired.

If I read the comments of 802 correctly we want higher pressure through more and maybe smaller nozzels to get more turbulence.

On a 2 x 8 rig, what blower would you think I should try, without having to resort to airtight doors ??

[Gary R]

C Wilcox, That's a nice "new evaporator" you have in the other post. I made one just like it. I think mine has done well for the past 2 season's, but I'm always looking to improve.

I added air under last year. Boil rate went up some but wood consumption sky rocketed. I am in the process of adding air over fire right now. I am also changing my grates. The ones I made would plug up with ash and reduce air flow.

In this thread is a link to Univ. Vermont research paper on air over fire. I want to cast a raised floor using cone shaped holes in it. I had to go on the internet to find castable refractory cement. The problem is it will cost about $150. just for a couple of bags of this stuff. I have bricks and 1 1/2 X 1 1/2 X 3/8 angle sitting here. I will probably make the floor as Brandon (WV Mapler) has described today. I have already made the piping changes to get air under and over.

Good luck with your project!

[HazensNotchSugarShack]

I am planing to add a similiar system to my leader 4x10 But hear is my question? This is an old leader 4x10 drop flue 4X6 I am just setting it up and have no clue how much wood I will need? Approximately how many gallons of syrup per cord of hard wood slabs. Thanks I have 4 cord cut and stacked and hope to do 100 to 150 gals next season am I close?
Rick

[C.Wilcox]

Gary R- Thanks! I'm looking forward to getting started on that project. It's partially my reason for bringing this thread back around. I wanted to hear from others whether it was worth adding over fire air right from the get-go or if I should just make it a simple toss wood in type operation. How did you go about adding your air supply and what type of blower are you planning to use? Are you adding dampers to control the air so you can get 75% above and 25% below? Sorry about the loads of questions. Any pictures you have would be greatly appreciated.

Do you have a woodstove supply store anywhere near by? Or a fireplace contractor? Maybe they could get your refractory cement cheaper and a quart of syrup might be just the incentive they need. Personally I'm thinking I'm going to use firebricks with holes drilled in them.

Brent- I believe 802Maple recommended a particular blower from Grainger in an earlier posting in this thread.

[KenWP]

Hazen they figure 15 gallons of syrup to every cord of wood as a guide line. The more improvements you make the better it boils and you can cut that down a bit.
I have a couple of blowers hanging around and am considering adding one to mine if I get the other 2 pans added on to the thing. That way I can get the heat onto the bottom of the other two pans.

[Gary R]

C Wilcox, I would try figure out how many taps you might end up with. If you only have about 50, then maybe no fancy options. If you have a 100 or so maybe you want the fancy options. Hood, preheater, forced air. I have a thread named "new guys rig" in the homemade evaporator thread. There are some pictures there. I have not added any recent pictures though. I had a blower on last year. It is a 6" round duct booster (industrial). I have no idea how many CFM's, but it will push flames out my 12' stack. I have it mounted outside, under my shack. I have 6" 30ga. pipe coming in through the wall and under the back of the evaporator. I cut a hole in the bottom of the arch (oil tank) right behind the back wall of the fire box. I have 6" pipe going up into a 90 degree boot for a furnace register. I will need to transition to my stainless tubing that will carry the air around the fire box. On the 6" elbow under the arch I cut a hole in it and inserted a 3" 30ga. pipe. This goes to a hole located under the fire box. This will deliver air under my raised floor. I have a variable fan speed control on the wall and will place a damper in at least one of the pipes under the arch.

Any of the local stores only have refractory mortor or fire clay. These are not high strength and would probably break by tossing a few logs in. I already have the angle iron and bricks in , I only need to drill them.

Hazens, you might want 1 or 2 more cord for 500 taps. slabs will burn a little faster.

Brent, sorry, were moving away from your woodburner. We can move.

[danno]

I was not overly impressed with my "air above the wood" improvement. I ran a manifold at the top of the slope across the arch and put in 4 1" pipes that ran from the manifold, above the fire, all the way to the doors. The 1" pipes were drilled with a 3/16th bit every inch.

Saw no improvement with efficiency and the 1" pipe failed aber about 3 boils. So, pulled out the pipe and just blew air out the manifold (4 1" holes). Still no improvement.

I was running a 1100 cfm blower below the fire and 550 cfm above the fire - all lazy air as Jerry would say. Next year I'll switch and put the big air above the fire.

For my new grates, I used fire brick with 3 3/4" inch holes in each brick. Holes would clog every 45 minutes or so, limiting air from coming up. After I would rake the grates, holes would clear and the fire/boil would come back. Thinking of redrilling with 1" bit.

Overall, efficiency and wood usage remained the same. Only differance I saw was less ash in the ash pit - which is not a bad thing.

[maple maniac65]

I am getting about 45 gallons/cord of good dry high BTU hardwood. I am running a steamaway on a 30x8 Leader revolution 7 1/2 inch flues. Without the steamaway I ran about 30/cord

[Pat Trevor]

I have a Lopi free standing fire place in the center of my basement and it heats our 1650 sq ft house in northern Wisconsin in tempuratures down to 10 below. It has 3 small pipes inside on the top with holes in them for the fresh air. This seems to be simular to what your talking about. It throws allot of heat for a little wood stove.

[HazensNotchSugarShack]

Thanks Ken And Gary! I was thinking two more cords you confirmed it my production manager is not happy about this! LOL
Danno you need to run larger diameter pipe up top four 1" have way more friction and not enough volume. I would need to get my flow chart but one 3" pipe will deliver more air than four 1" pipes I am planning two 3" for my 4 ft wide evap. Just my lonely opinion. It's free and worth every penny!

[C.Wilcox]

C Wilcox, I would try figure out how many taps you might end up with. If you only have about 50, then maybe no fancy options. If you have a 100 or so maybe you want the fancy options. Hood, preheater, forced air. I have a thread named "new guys rig" in the homemade evaporator thread. There are some pictures there. I have not added any recent pictures though. I had a blower on last year. It is a 6" round duct booster (industrial). I have no idea how many CFM's, but it will push flames out my 12' stack. I have it mounted outside, under my shack. I have 6" 30ga. pipe coming in through the wall and under the back of the evaporator. I cut a hole in the bottom of the arch (oil tank) right behind the back wall of the fire box. I have 6" pipe going up into a 90 degree boot for a furnace register. I will need to transition to my stainless tubing that will carry the air around the fire box. On the 6" elbow under the arch I cut a hole in it and inserted a 3" 30ga. pipe. This goes to a hole located under the fire box. This will deliver air under my raised floor. I have a variable fan speed control on the wall and will place a damper in at least one of the pipes under the arch.



Gary R- Excellent advice, thanks. I think I will keep this version simple and forgoe the over the fire air upgrade until I get the opportunity to increase my number of taps.

[KenWP]

I plan on haveing some kind of flue pan or pans next year and most likley will add some kind of under the fire blower just to increase the flow of hot air to the flue pans. It took me a long time to boil 40 gallons of sap off useing a 2square foot pan and anything will be a improvement. I am hopeing to get up to 8 gallons a hour which will cut the boiling down a lot. 6 hours hopefully instead of 13 to 15 hours.

[3rdgen.maple]

Hazen are you using soft or hardwood? I had 6 cords of softwood stacked in the sugarhouse this past year and it was all gone after 35 gallons. It was all dry split small diameter softwood. I could not tell you how much more I burnt after that just kept chucking it in. I like burning softwood in the evaporator nice hot fire. Keeping up in the sugarhouse is hard enough work let alone running out of wood and cutting and splitting in the process. I would cut more, alot more If you have alot left hey your ahead of the game for next year and you will get a good feel for how much wood you will need for the following season. Just a little note though I am talking face cord 2'x4'x8'. Some guys go by full cords and then there are guys like us new yorkers who go by face cord.

[HazensNotchSugarShack]

3rdgen According to you New Yonkers I would have 4 face cords of softwood and 4 face cords of hard wood. As time permits I plan to stack 4 face cords of soft and 4 hard for next year and if i need them this year they will not be far away.
Do New Yonkers sell face Quarts of syrup? LOL

KewWP I will post a pic of last years homemade evap that boiled more than 25 per hour with very little fire. Tank is sunk into evap with preheater built around stack pipe flat pan 20 X 54.

[maple flats]

I get about 22-24 gal/full cord. I burn about 75% hard mixed with 25% soft. The only wood I cut to burn is hardwood but then I cut the slabwood from my sawmill for the softwood. The North american Maple Producers Manual says 25 gal/cord is typical. Back when i burned just hardwood I got about that with my pre heater and hood. I like to have what I think is a 2 year supply ahead, then if I have a super season I don't have to do more wood to keep going.

[3rdgen.maple]

Okay Hazen it is a New Yorker not a New Yonker. I was trying to help you out because I have seen alot of people not now the difference between a face cord and a full cord. I was just born here I did not come up with the face cord scam. I think it was probably our polititians trying another scam to rip off New Yorkers. Yep great idea some elderly person buys a load of wood at a set price and finds out after it is delivered it is half the amount they expected. So when people around here buy there wood now they are expecting a face cord of wood. Oh cannot personally confirm this but I am told that a New Yonker face quart of syrup is alot more valuable than a New Hampster full quart of syrup. I am guessing it is all about taste and quality. Sorry but had to do it!!!!:D

[KenWP]

I am more confused then I was before now. I was hopeing to expand my boiling capacity at least 3x by just useing 3 times the surface area. I am hopeing that inventing somekind of drop flue system will acheive that goal and if needed to supply some kind. of extra air to the fire box to do it . What I am hopeing is that the fire box under my 2 foot square pan now will supply enough heat to boil the other two pans. What size fire box would a half pint have for example or a 2x6 evaporator.

[3rdgen.maple]

I am more confused then I was before now. I was hopeing to expand my boiling capacity at least 3x by just useing 3 times the surface area. I am hopeing that inventing somekind of drop flue system will acheive that goal and if needed to supply some kind. of extra air to the fire box to do it . What I am hopeing is that the fire box under my 2 foot square pan now will supply enough heat to boil the other two pans. What size fire box would a half pint have for example or a 2x6 evaporator.

Ken If you add drop flues aor drop tubes like you are talking about you will increase your evaporation rate, and you will be amazed at the difference in the way the rig boils. My 2x6 fire box is about 24 inches in lenght before the ramp and Im guessing 30 inches wide. The arch tapers up to the pans at he firebox. How many pans are you adding flues too and what length are the other 2 pans?

[KenWP]

With those figures 3rdgen I should get away with it if I use drop tubes. I would have a total of 6 square ft of surface area. I am hopeing for 9 gallons a hour which should get me where I need to go.

[3rdgen.maple]

Ken after the firebox build a ramp to get the flames up to the bottom of the pans. Line that arch good to retain the heat I bet you will get that.

[HazensNotchSugarShack]

I am more confused then I was before now. I was hopeing to expand my boiling capacity at least 3x by just useing 3 times the surface area. I am hopeing that inventing somekind of drop flue system will acheive that goal and if needed to supply some kind. of extra air to the fire box to do it . What I am hopeing is that the fire box under my 2 foot square pan now will supply enough heat to boil the other two pans. What size fire box would a half pint have for example or a 2x6 evaporator.

Ken 3rdgen is correct that tapering a slope up to the pan, and insulating the arch increases eficiency. If you do drop flue make sure you have a drain to get the syrup out of the flues. To get plenty of air to mine I built a rebar grate for the bottom of the fire box and placed an ash tray 4 inches below to alow air to come up thru the fire. Here are the pics of this past years evap that was built in less than 8 hours. (That's why it's not finished yet) The preheat pan is welded ss (20 gal cap)with 2" insulation and galvy outer shell to contain insulation and would begin to boil. Arch had 1" insulation. Main pan is 20 X 54 from an old cold buffet table and is 10" deep and ran best with 4 "to 5" of sap in it. Best of luck! Rick
3rdgen I wouldn't know about NH syrup! I'm so screwed up I make Vermont Syrup! Going to be in New York area tomorrow thru sat. Lake George! I hadn't heard the term face cord in many years and it makes no sence to me.

[Brent]

Ken

you're on the right track. the size of the firebox is not the major factor in efficiency.

the firebox on a Leader Half Pint is aobut 28 x 24.
the surface area of the pan is about 1000 sq inches.

on my Phanuef 2 x 6 rig the firebox is 24 deep and only about 22" wide.
pretty much the same as the Leader Half Pint

the syrup pan is 24x24 = 576 sq in
but the flue pan has 11 flues about 9" deep and it roughly comes out
to 10,000 sq in.

Without blowers the Phaneuf uses the same amount of wood as the Half Pint did, but it will boil nearly 45 GHP. ( with a hood that is ) Most folks figure the hood and preheater add about 10%

So don't worry much about the firebox. Get lots of area on your flue design

[3rdgen.maple]

3rdgen I wouldn't know about NH syrup! I'm so screwed up I make Vermont Syrup! Going to be in New York area tomorrow thru sat. Lake George! I hadn't heard the term face cord in many years and it makes no sence to me.


Hazen thought you were from New Hampshire, That is what your location says. And I agree that whole face cord thing is stupid. Lake George is a beautiful area have fun out there.

[Brent]

If you think face cord doesn't make sense in New York

If you buy a face cord from most folks in Ontario you get 4 feet x 8 feet
of peices 16" long.

If you go into the Menonite community you get 4 feet x 8 feet but only 12" long. But their prices are lower and they let you stack them tight if you load it yourself.

[HazensNotchSugarShack]

3rdgen I am but my sugarbush and vacation (oxymoron for sure) home are in vermont.

[Teuchtar]

I'm thinking of the economics of adding surface area to an existing pan:

Option 1) Solder 1/2 coupling ($2) and fit an arrestor ($14 at McMaster). This provides 1-3/8" diameter, 6-1/2" long = 28 sq inches for $16, or $0.57 per Sq inch. You'd need 1172 added inches, or 41 arrestors, that would be $656
Pro: It sounds feasible, maybe tricky. Con: Nasty to clean inside, hard to brush off soot outside, would fall apart if you smoked the pan, and resale value ??

Option 2) Purchase 2 more 24 x 24 sugar pans at $295 D&G or $344 CDL or a single large flat pan.
Pro: Instant gratification, resale value of pans nearly same as purchase price.
Con: Need to add cost of extending arch. Ironwork is cheap, but would need $100 or more of archbrick. Archwork is easy and help available. Plus sell the pans when you upgrade to next size evaporator.

My own first homemade arch was 24x24 flat pan. I though about how to add flues, but opted in the end for the D&G rig. I held onto that original pan, and now it forms the pan for my homemade piggyback on my 2x6. These stainless pans can last forever !

[KenWP]

Man talk about a bucket of cold water on a guys plans. The arrestors do not exist in Canada anyways so I have to use copper pipe as copper tubeing dosn't exist in 1 inch size. I will figure out something yet just might take a little brain work to do it.
I am basically trying to use up more of the heat that goes up the chimney to boil faster.

[Teuchtar]

Ken
Sorry, I didn't mean to do spoil your thoughts. Just trying to share the little bit of knowlege thats been shared on the board already. I tried to make that work, but I gave up before I started drilling/soldering. If you can make that idea work, I think you should go for it, and share your experience.
The copper tube idea has been tried, but I've lost track of who'se done it and made it work, and whether they in fact did achieve the rate close to what a flue pan gives.

[RileySugarbush]

That was me. For better or worse, I have made three of those drop tube steam table pans!

First of all, they do work! and not a bad DIY project. The first pan used pipe and caps, no couplings. Flared and soldered into holes punched in the pan bottom. Next two used 1 inch arresters from Home Depot. No couplings, no caps. Cheaper and easier than pipe/caps and no where near $14 each. Easy to clean with a drill and a brush.

Another and much cheaper option is to just use thin wall copper pipe and pinch and solder them closed on the ends.



I estimate they trippled the evaporation rate per pan for me.

For what it's worth, these have gone on to a good new home ( where they are loved and cherished) and I now have a DG drop flue pan.

Check the construction photos out here:
http://web.mac.com/jabushey/iWeb/Riley%20Retreat/Maple%20Sugaring.html

[Mac]

NH regs do not recognize a face cord, The term ""cord'' when used in connection with wood intended for fuel purposes shall mean the amount of wood that is contained in a space of 128 cubic feet when the wood is ranked and well stowed, as defined in the National Institute of Standards and Technology Handbook 130 as revised and amended.
Source. 1985, 72:1. 1994, 100:2, eff. July 10, 1994 RSA 438:3

[whiteout]

Hi, I am adding over the fire air as outlined in uvm's "guidlines for improvement of combustion efficiency". Does anyone know were to buy the Max Bond air set plastic refractory cement? Also what is the model # of the draft gauge they are talking about? Thank you

[Gary R]

Are you looking to bond your bricks together or pour a fire box floor? I was going to do the poured floor thing. I called a manufacture of refractory cement and found the same thing they spec'd on ebay. The problem was each bag was going to cost about $80 because of shipping. I think it was around $30 a bag if you can find it at a retail store. I needed 3 bags just to do my little 2'X2' fire box floor. I went with a fire brick floor instead. I have about $15 in the whole thing.

[whiteout]

I was looking to form it around the air nozzles instead of cutting bricks.