New 36inch castable build in Brisbane

[mikku]

Re: New 36inch castable build in Brisbane

I'll be facing a similar situation in the not too distant future. My oven will be under a roof and I'll have to do the roof flashing. Roof penetrations is not very common here, a large percentage of people vent their wood burning devices through the wall then transition to vertical.

The wood stove shops want an arm and a leg for any of their parts so I have fabricated my own chimney and will do the same with the roof flashing and storm cover- similar to yours. I used spiral stainless ducting (inner 150mm and outer 200mm) capped the ends and filled the inside with loose perlite. You can still feel some heat, but it will not burn you. My roof will possibly be standing seam galvalume (maybe black) .035mm and the chimney flashing parts probably .05. I have a friend who is a sheet metal fabricator who lets me use his special tools for my own work (like running the standing seam panels).

It is nice to see how a nice build comes together. Now that this project is nearing completion---what is next on the list?

There is "stove gasket cement" that might also work for you. If you marked the finish location of the storm collar on the chimney, then applied the cement beneath the collar--when you slid the collar down to the proper place, you would only see a very narrow line of black from the gasket cement. When it dries, it is hard like a rock and should work for your max temperature range... just a thought if the silicone becomes a problem.

Even if some water did seep by--it would only be a few drops! No big deal anyway!

[brissie]

Re: New 36inch castable build in Brisbane

I have a friend who is a sheet metal fabricator who lets me use his special tools for my own work (like running the standing seam panels).

It is nice to see how a nice build comes together. Now that this project is nearing completion---what is next on the list?

There is "stove gasket cement" that might also work for you. If you marked the finish location of the storm collar on the chimney, then applied the cement beneath the collar--when you slid the collar down to the proper place, you would only see a very narrow line of black from the gasket cement. When it dries, it is hard like a rock and should work for your max temperature range... just a thought if the silicone becomes a problem.

Even if some water did seep by--it would only be a few drops! No big deal anyway!

You need the tools to do job properly. If you have access to sheet metal fabrication tools it makes it a lot easier, you just can't do tight bending or seaming, and waste a lot of time without them. Hope it goes well.

It's been great to work on the oven, it's been fun. I think I will shift into cooking mode, and start bread baking and other delicious food possible with a WFO. I have many interests, its probably time to get the veggie garden working again, and follow on with other projects not completed.

Gasket cement is an option, but I will wait and see what happens to the silicone. It might last a few years. I set up a temporary roof and roof penetration the had a half inch (15mm) gap all the way around the chimney. It did not leak much. Had a few drops of water after heavy rain come through. The tight fit of the SS transition will not let much water through.

[brissie]

Re: New 36inch castable build in Brisbane

Dam, have a hairline crack about a foot long (300mm) after firing up again. Cleared the dome and ran the fire for several hours.

Last night the oven walls where 320 c, when I put a hebel door on, this morning the oven is 250 c. It's warm on the outside towards the top, but not hot.

See the photo and crack at bottom right.

[david s]

Re: New 36inch castable build in Brisbane

Don't panic about it. The outer shell is only to keep the weather off. Keep giving it some more firings to see if any more cracks show up and to drive out all the moisture. Then get some of your Acratec and work it into the crack. I like to give my ovens around 10 decent firings before adding any waterproofing on the outer shell, that way any cracks show up and you are not locking the moisture in, which I think is your problem.

[brissie]

Re: New 36inch castable build in Brisbane

Don't panic about it. The outer shell is only to keep the weather off. Keep giving it some more firings to see if any more cracks show up and to drive out all the moisture. Then get some of your Acratec and work it into the crack. I like to give my ovens around 10 decent firings before adding any waterproofing on the outer shell, that way any cracks show up and you are not locking the moisture in, which I think is your problem.

Thanks David s,

I have sealed the domes last render layer. It was probably not a good idea. I will fire it up again. and see how it goes. I have not used Acratex but a clear acrylic sealer. If steam is exiting the crack I will fill the crack with no-more-gaps, and seal it again after several firings.

[david s]

Re: New 36inch castable build in Brisbane

I wouldn't use no more gaps, it is for internal use only. Use the acrylic product you used before, it will bond better to itself, but just hold off until you have had several more fires.

Out of interest, do you have a vent to your insulating space?

[mikku]

Re: New 36inch castable build in Brisbane

Thanks David s,

I have sealed the domes last render layer. It was probably not a good idea. I will fire it up again. and see how it goes. I have not used Acratex but a clear acrylic sealer. If steam is exiting the crack I will fill the crack with no-more-gaps, and seal it again after several firings.

I would recommend a more calm approach.

Do absolutely nothing with it for now. Fire your oven and use it normally for several months, even a year. If you have days that look like rain, then make sure that the oven is covered so that no moisture can migrate in via any of the hairline cracks. This is probably not the only crack that will show itself.

Putting any sealer of any type into the crack, I think is a pointless move because if steam is an issue, it will find it's way out there or somewhere else.

All cement products will crack to some extent. Normal is not the case with WFO's because of the temperature extremes we work with. The cast core has to expand and contract through the thermal cycles. But your ceramic fiber layer can also act as a cushion.

Mine is different--no ceramic fiber blanket, so when cracking occurs...it is more evident, the initial cracks to my pericrete layer occurred maybe after the first 8 firings, then they settled down.

So, in conclusion--enjoy your oven right now! Don't react, see what happens over a longer period of time. Really, there is nothing you can do right now anyway!

Oven looks great!

[brissie]

Re: New 36inch castable build in Brisbane

I wouldn't use no more gaps, it is for internal use only. Use the acrylic product you used before, it will bond better to itself, but just hold off until you have had several more fires.

Out of interest, do you have a vent to your insulating space?

Yes two, a vent on top of the dome, and the chimney is also vented.

[brissie]

Re: New 36inch castable build in Brisbane

I would recommend a more calm approach.

Do absolutely nothing with it for now. Fire your oven and use it normally for several months, even a year. If you have days that look like rain, then make sure that the oven is covered so that no moisture can migrate in via any of the hairline cracks. This is probably not the only crack that will show itself.

Putting any sealer of any type into the crack, I think is a pointless move because if steam is an issue, it will find it's way out there or somewhere else.

All cement products will crack to some extent. Normal is not the case with WFO's because of the temperature extremes we work with. The cast core has to expand and contract through the thermal cycles. But your ceramic fiber layer can also act as a cushion.

Mine is different--no ceramic fiber blanket, so when cracking occurs...it is more evident, the initial cracks to my pericrete layer occurred maybe after the first 8 firings, then they settled down.

So, in conclusion--enjoy your oven right now! Don't react, see what happens over a longer period of time. Really, there is nothing you can do right now anyway!

Oven looks great!

Yes, its time to enjoy the oven. I will be cooking Xmas dinner in it. Not much I can do but wait. So will continue to use the oven and see what happens.

Interesting that the hair line is invisable now. The sun is hitting the dome and I have a fire inside. The heat from the sun Is heating the external shell more then the oven.

In a few months I will reassess waterproofing.

[Lancer]

Re: New 36inch castable build in Brisbane

I must say it cooks really well. had to stop cooking to finish the render and some other bits and pieces. I will be cooking for Xmas, and have most of it completed.

Cheers,

Cooking for Christmas! Now that's the life. If I'm cooking for my birthday in April I'll be lucky. Enjoy the fruits of your labors. I'd say the problem you face is minimal at most, think about it after and bring us a Christmas story!

[brissie]

Re: New 36inch castable build in Brisbane

Thanks lancer, I agree the crack is a minimal issue. At least I get to cook a turkey and ham in the oven for Christmas. I will post some photos for sure.

Cheers,

Steve

[cobblerdave]

Re: New 36inch castable build in Brisbane

Gudday Steve
Hairline cracks in the render don't count for anything. Chase them out with a screwdriver, fill with paintable silastic and paint over it. I had a couple radiating from the chimney I treated them like that and they never came back
Regards dave

[oasiscdm]

Re: New 36inch castable build in Brisbane

Hey Dave don't they call that an expansion joint

[Lancer]

Re: New 36inch castable build in Brisbane

Hey Dave don't they call that an expansion joint

No, heck no! Its a crack in a certain light...

In the days of old when brave men set out on wooden sailing ships they always brought along an optimist for just this purpose...because he is usually right. :b:

[cobblerdave]

Re: New 36inch castable build in Brisbane

Hey Dave don't they call that an expansion joint

Gudday not at all. An Expansion joint is the two that live at both edges of the oven entrance. You can't find them cold. But they are there when the doors on and ovens hot. The entrance is angle iron and they start there and climb up the mortar joints into the chimney. Haven't cracked a brick or gone into the oven so we get along real fine.
Regards dave