base for flue crock

[Dagored154]

would there be a problem with building a form to create my own arched base for the flue crock. I was thinking of using the Heat Stop 50 mortar and some wire fence material inside a plywood form to make a base to set the flue on. I am thinking to make it 3" thick and of course with a 8 inch hole in the middle. would the mortar hold up or would it crumble? should I add some fire clay? or use concrete alone? Help!

[Laku]

Re: base for flue crock

Mortar won't work alone that thick, concrete can't handle the heat.

Your best bet is refractory castable if you don't wan't to use bricks.

[mrchipster]

Re: base for flue crock

Mortar won't work alone that thick, concrete can't handle the heat.

Your best bet is refractory castable if you don't wan't to use bricks.

In addition do not use chicken or fence wire, use stainless needles in the refractory castable for added strength, non-stainless steel or aluminum wire will degrade and cause future problems.

Chip

[GianniFocaccia]

Re: base for flue crock

If you are using the term flue crock to refer to the flue gallery, or vent, then yes, this is a viable way to go. Casting a vent allows for custom shapes and angles that would be more difficult to accomplish with bricks. Like Laku says, use castable.

These two FB builders successfully cast their vents:fxpose, drseward.

[Dagored154]

Re: base for flue crock

yes I am talking about the vent to set the 8" round by 24" flue crock on top of. I have a form all cut out and ready to put together. never heard of refractory castable so now I will search for that.
my other option is to stay square with the sides of the doorway/flue vent area, whatever you call it and then set a 1" thick piece of marble on top of the fire brick. I think I can cut a hole in the marble slab and then set the flue on top of that. this would give me a square smoke chamber, if you will, and I would expect the smoke to draft out the flue OK. What do you guys think of that idea?

[mrchipster]

Re: base for flue crock

I think I can cut a hole in the marble slab and then set the flue on top of that. this would give me a square smoke chamber, if you will, and I would expect the smoke to draft out the flue OK. What do you guys think of that idea?

Marble will not hold up to the heat, neither will Granite. Soapstone its the only stone recommended for that type of heat and it would need to be quite thick to hold up the flue. Soapstone is known for its veins and if one was in the wrong place it may also crack. So based on that I would not recommend it.

It is challenging to build the flue arch from brick but has been done by most who have these types of ovens, the brick can be cut to support the flue and a transition can be made to make it all work. I would hate to see you throw a bunch or work into something that is doomed to fail. The more complete the oven the more difficult it is to fix a broken internal component; so best to do it right the first time.

The castable is a great way to go as well as brick built, both are tried and true methods.

Chip

[Dagored154]

Re: base for flue crock

thanks so much for the great advice Chip. I will try cutting the brick and make the transition. I like the castable idea but one bag shipped here would be over $100. I can cut lots of brick for that amount of money. this is already costing a ton of cash. thanks again.

[Dagored154]

Re: base for flue crock

On page 47 of the Pompeii oven instructions it states "pour the vent, and allow 2-3 days for the concrete to dry before you remove the form." I have three bags of quickcrete mix on hand and I would need to order the refractory castable and pay over $100 when it is all said and done. I understand that the rc would be the best but why does the book say to use concrete? this is not the first time I have found discrepancies in the "bible". Is concrete OK or is it a total no-no?

[GianniFocaccia]

Re: base for flue crock

There are a number of items in the FB plans that are not optimum. One reason is that the plans originated a number of years ago, were intentionally simple, and the job of constantly updating them prohibitive. Another reason is that the evolution of the forum builders continues to redefine the standard for oven construction and design. And lastly, this forum exists to assist in the sales of ovens and all the related materials that go in and around them. The mere fact that builders share with others what they learn (good and bad) renders this a site of goodwill and cost-effective marketing.

Rather than take older plans as 'gospel', why not read up on the latest (free) techniques and designs and select those that fit your skills, timeframe and pocketbook?

[david s]

Re: base for flue crock

would there be a problem with building a form to create my own arched base for the flue crock. I was thinking of using the Heat Stop 50 mortar and some wire fence material inside a plywood form to make a base to set the flue on. I am thinking to make it 3" thick and of course with a 8 inch hole in the middle. would the mortar hold up or would it crumble? should I add some fire clay? or use concrete alone? Help!

Building a sand castle for the form and then trowelling over some castable refractory works really well and is simple and quick to do. 1.5" thick is enough, you can achieve compound curves easily and the stuff sets up really hard with or without ss needles. Also it only requires 24hr cure rather than a week like portland cement products. Downside is it's expensive.

[Dagored154]

Re: base for flue crock

Thanks so much for the reply. I now better understand the purpose of all this. I like the idea of the sand castle. I am using sand to build the dome and could easily make a mold for the castable as I have lots of sand. thanks

[david s]

Re: base for flue crock

Once you've created the form you want, cover it with wet newspaper strips before troweling the castable over it.

[Dagored154]

Re: base for flue crock

great idea. I am still having trouble finding castable locally in Harrisburg PA