Structural Slab for new WFO

[stonecutter]

Re: Structural Slab for new WFO

Hello Stonecutter,
If you are bandsawing and thickness planing, then you are working with dry wood.... right? I have to be missing something...oak is a great firewood...what is the cladding and shielding that will prevent it from spontaneously combusting?

You and Davids have been doing this for a while--working with WFO's....why would both of you use wood when at first glance, it would be assumed to be an inappropriate material?

Yeah, the wood is from oak skids...they are 3"x3"x8' and rock hard. As for the shielding, I'm not sure if I will do it. When I use a WFO, I try to control the fire so as not to depend of the door as a damper...that is to say, I won't be blocking off a raging fire with a wooden door. It's there more to slow down the draw (partially closing off the opening ) or to help store heat after all the coals are out of the oven itself.

I don't think wood makes a better fire blocker than a quality metal door, like the one Karangi Dude has. But, the right types of wood can and have been used around WFO's and fireplaces for centuries. I have restored dozens of beehive ovens in homes from the 17th,18th and 19th centuries and many of them had heavy oak or chestnut lintels directly above the firebox...still in good condition. A wood door will last as long as it's not treated like something fireproof, and it's hard to beat the character of a well made wooden door.

[david s]

Re: Structural Slab for new WFO

Hardwoods are generally more resistant to heat than softwoods. But of course being denser would not insulate as well presumably.i use Quilla which is a quality hardwood. To prevent it from charring I have 12 mm of bio (safe fibres) mill board. If my oven door is left in place for too long say three hours, then the door gets hot and is beginning to cook. But when baking or roasting it does not stay in for even that long usually. I could increase the thickness of the panel to improve the insulation but that will make the door more difficult to handle. Because my oven is small my door is small and I operate the door one handed which is very useful. Also because my oven is small it is no problem to kick in with abit of fire to bring up the temp the next day because it uses so little fuel. I have made the mistake of placing the door when the oven was really hot in an effort to save heat for the next day and found the door burnt through the next morning. A customer who hired my mobile version also did exactly the same thing. If my door is only used for roasting and baking then it's perfectly ok. Also ok to place it half way into the entry when hotter for short periods. I quite like the idea of knowing it's fragility and limitations.

[mikku]

Re: Structural Slab for new WFO

David s---hello!
On this topic, I know absolutely "zero" and zero would be boasting!

I have no idea that wooden doors have been used for centuries... Like I say,
I am just trying to figure out what works so that I do not waste a lot of time doing something and ending up with nothing---except the experience of failure!

So---wet? , Dry? How do you use a wooden door and not end up with a pile of ashes? What species of wood would be better?

Japan has oak...called Nara. I do not know what kind of oak it is, but usually used to propogate "shitaki mushroom", otherwise considered only good for firewood or to be chipped.

We also have sugi, sawara, and hinoke. Hinoke is also called Port Orford cedar and used for hot tubs etc. This is a very nice type of cedar.

Keiyaki (I do not know spelling) is a decidious tree and has beautiful graining--can be used in fine homes and furniture.

That is about it---for local woods, any suggestions on what would work for a good oven door? I can get chunks of wood from a variety of local sawmills. Even some of the stumps are used for tables etc...that is..if they have some very good character to the grains.

I mentioned in a different thread...I might have access to "ume wood", Japanese plum or apricot wood. For firewood. I do not know if there are any larger pieces available for making a door. This source is very preliminary right now.

[david s]

Re: Structural Slab for new WFO

Hello Stonecutter,
If you are bandsawing and thickness planing, then you are working with dry wood.... right? I have to be missing something...oak is a great firewood...what is the cladding and shielding that will prevent it from spontaneously combusting?

You and Davids have been doing this for a while--working with WFO's....why would both of you use wood when at first glance, it would be assumed to be an inappropriate material?

What material would you suggest as an alternative?
Wood is a pretty good insulator, looks good, easy to fabricate, cheap, relatively lightweight,was used for centuries for oven doors and so long as it does not get too hot will provide good service for quite a long time. An insulating panel can take the sting out of the radiant heat.

The most common alternative is steel. A poor insulator, can get dangerously hot, difficult and expensive to fabricate, heavy and unless made of stainless is subject to corrosion which is of course accelerated by heat.

Wood for me, but I'd love to be convinced of an alternative.

[mikku]

Re: Structural Slab for new WFO

Hello Stonecutter,
If you are bandsawing and thickness planing, then you are working with dry wood.... right? I have to be missing something...oak is a great firewood...what is the cladding and shielding that will prevent it from spontaneously combusting?

You and Davids have been doing this for a while--working with WFO's....why would both of you use wood when at first glance, it would be assumed to be an inappropriate material?

[stonecutter]

Re: Structural Slab for new WFO

I plan on making my door from thick white oak...I have a pile of 3"x3" that I will cut into planks on a bandsaw, then thickness plane them down for the door. I'll probably make them 2" thick. I haven't decided if I'm putting some kind of heat shield on it...probably will do something then clad it with copper...maybe.

[mikku]

Re: Structural Slab for new WFO

So, your oven door is made of wood?

From your experience and from other people you talk to, is that the norm for oven doors?

A project that has been on my mind for a while was making the door from light steel that would surround some kind of insulating material--Oya stone, Power board, Pericrete, or if somehow I could find some ceramic fiber. The whole thing fabricated then the seams welded to keep the insulation inside. Pipe sleeves where thru bolts to hold handles, same for where thermometer would be mounted. A lot of BS to make a cover.

If wood works best, that is the easy out--something I work with daily or chunks that could be cut off logs or stumps to fabricate a cover. I would imagine wet is better--same as for wooden sauna buckets--keep them wet, they will hold water.

I don't know about the fist in the oven method. There is a delay between when burning occurs and your body's ability to sense pain. Have gotten some pretty good burns while welding--after picking up things with unprotected hands.. the time it takes to say O-H! N-O! is more than enough to get some pretty good burns.

[david s]

Re: Structural Slab for new WFO

I wish we had this conversation a week ago! I have the IR unit and the oven door thermometer is on order--cannot be cancelled without making problems with my supplier.

I guess everything will come out in the wash....

As for the oven door thermometer, did you determine why you were getting lower readings? Could you have made the door differently--or after regular use, could you anticipate the difference in readings and still find it useful?

Hard to justify wasting money--when I have been careful most of the time on this build, I have used good materials but found them at really good prices or free. Now, the recent purchases are like pi--ing away hard earned money! Argh

Thanks for the insight!

No, I didn't determine why the readings were lower, but probably because a good part of the probe was surrounded by the wood of the door which is a pretty good insulator. I abandoned the door thermometer mainly because I could see it getting damaged if the door tipped over. Even if the readings are different it is still useful because you just adjust your cooking according to the readings you've got. You will find that the IR gives readings that are higher because it is taking the surface temp of whatever you are pointing it at. The air temp thermometer inside the oven reads somewhere between the other two.
You will find them all useful, at the start. Once you start cooking and getting to know your oven you will use your measuring equipment less and less. I love the traditional Italian method of placing your fist in the centre of the oven and time it for how many seconds you can hold it there.

[mikku]

Re: Structural Slab for new WFO

I wish we had this conversation a week ago! I have the IR unit and the oven door thermometer is on order--cannot be cancelled without making problems with my supplier.

I guess everything will come out in the wash....

As for the oven door thermometer, did you determine why you were getting lower readings? Could you have made the door differently--or after regular use, could you anticipate the difference in readings and still find it useful?

Hard to justify wasting money--when I have been careful most of the time on this build, I have used good materials but found them at really good prices or free. Now, the recent purchases are like pi--ing away hard earned money! Argh

Thanks for the insight!

[david s]

Re: Structural Slab for new WFO

I tried the thermometer in the door, but found it unsuitable as it gave an inaccurate (lower) reading in that position. It he probe sticking out is also a nuisance and subject to damage. The thermometer inside the oven is perfectly adequate but yes, you have to open the door to read it. At temps higher than 300C the soot burning off the dome can be your temp indicator. After you've fired your oven a dozen times you won't really need any fancy temperature measuring devices. I have kiln pyrometers thermometers with probes that go through the dome wall IR gun and the cheap thermometer like you have. Most of the time I never use any of them, but if I do it is usually the little cheap one that sits inside the oven (roasting or baking only)

[mikku]

Re: Structural Slab for new WFO

The one I have reads maximim 600 deg F. For most cooking that is more than adequate, but I still need something that reads higher for the original curing fires ... right?

That was the reasoning behind using the IR thermometer.

When I eventually have the thing cured, (WFO) probably the IR will just be another piece of junk to take up space somewhere...

As far as baking is concerned, don't you have a thermometer on your oven door? Or do you have a window in the door to see the interior temperature on the oven thermometer?

Would not take much to make a larger base for the little oven thermometer.

Have to start looking for some thicker stainless for making some oven tools. No where in my non-budget is there money available for store bought tools!

[david s]

Re: Structural Slab for new WFO

That little thermometer you have in the oven is exactly the type I use. They are cheap, accurate and you can read the temp where you need it. Do yourself a favour and pop rivet a larger base on it. When moving it around the oven with the existing base they fall over and are difficult to manouevre.

[mikku]

Re: Structural Slab for new WFO

Ran into a merry-go-round circle jerk this week.

Since I could not get the IR thermometer I wanted via Amazon--because of import restrictions, I ended up buying one threw my hardware store. Today when I got some commercials from Amazonjp, the product I had been looking for before was now available here at a competative price. Now I have an off-brand IR thermometer for more expensive than a brand unit!

I was able to locate a good quality oven door bi-metal thermometer and that is now on order.

Since there are a few things waiting to arrive--decided to add the rest of the pericrete insulation around the chimney sleave--that turned out being a lot of monkey business as well because it had to be stacked 16" high and it tapers from around 5" to 2" thickness at the top. Free style insulation--now the oven begins looking like some outer-space ant hill. This insulation was 5:1, perlite to portland--should be a little firm tomorrow, but fragile.

I looked at several different LP gas burning devices, ones that would be used for outdoor cooking (circular burner rings), replacement oven parts for commercial ovens, and weed burners. The weed burners are available with different tips, orifices, wands, and hoses. I decided that a nice item for starting the wood fires without newspaper--etc could be used maybe in my initial curing as well. I'll be ordering the smallest orifice size, using .4kg LP/hr. Should be able to throttle that down as well. I guess enough said on that subject, agree that I should be able to get controlled temperature curing with this process.

Attached are the chimney cover insulation--after the curing process, the entire thing will get a render and some type of final water/repellant coating.

The insulation around the chimney actually does more to insulate the landing area. The chimney doesn't need the insulation--it is already insulated; once the render is in place, it will give a lot of support for the chimney.

[david s]

Re: Structural Slab for new WFO

Be careful when using an IR thermometer. It reads the surface temp which will be higher than that which is deeper in the walls, hence the slow temp rise required. Water in the refractory will hold down the temp wherever it is present. You've reached the exciting part- FIRE !
Good Luck.

[mikku]

Re: Structural Slab for new WFO

I am at the point of ordering thermometers, both for the oven door and an IR thermometer to measure firing temperatures. I had the order all typed in and the items cannot be sent to Japan using amazon. If I search amazon, jp; I am having difficulty finding anything. Must be some restrictions on lazer or IR in this country. I'll have to try some other sourcing to see if I can find something somewhere.

I am trying to locate items that would allow me to do a more controlled firing, so far with no luck. There is no real rush to get this oven completed, it is more important at this point to do it right. So I will be taking my time more....

The place where I located the furnace cement was really surprised to see that someone in this area was actually building a workable pizza oven. Their business sells imported wood stoves, accessories, and chimneys. When I showed my pictures, people gathered around and asked questions for about an hour.... I was really surprised with the interest shown. A wood fired oven is called a "kamma" in this country!

The list is growing of people who want to see my oven in operation. This summer sometime will be the date to shoot for.

Thanks for the firing information and everything else!