VC Defiant 1975 rebuild question

[Logman402]

Hi everybody, first time posting. I am rebuilding my vermont castings defiant and I dont quite understand part of the instructions. I am trying to figure out the screen in the fireback between the secondary gas chamber. It to lay furnace cement and smooth it out with a putty knife. Am I sealing that rib off from the secondary gas chamber, or should there be a small gap for air to get to it. If its sealed what would be the purpose of the screen?

 

[fbelec]

welcome to the forum. the screen is shaped like a v with the top portion of the v to fit on the fireback on one side and the other to the back of the stove. the top of the v on both sides is about 3/8 of a inch wide. put a layer of cement in the v so that the fireback can move and the maybe not at the same time the back of the stove but keep the air in that channel for the secondary fire chamber only and that air is not to be mixed with the primary air. hope i explained that well enough the bourbon is still running in me.

 

[Logman402]

Okay, I think I understand. The screen should be completely sealed, but what would be the purpose of the screen? Why couldn't I just lay the furnace cement down and fill the gap?

 

[peakbagger]

The screen acts like rebar in concrete and keeps the mortar from cracking and acts as a form to keep the mortar out of the secondary air tube.

 

[Logman402]

Thank you so much! I have been scratching my head trying to figure out if it was just a "filler" and adds strength or if I was supposed to be leaving room for air. The last thing I want to do is put everything back together only to have to tear it back apart.

 

[peakbagger]

Just in case there is a misunderstanding, the channel to the secondary air port has to be kept open. The screen and mortar is to seal the gap between the back of the fireback and the secondary air channel I think the instruction mentions using a dowel to ensure that the channel is open from the left side of the stove to the right side air port.

 

[Logman402]

Yup I get the secondary air port needs to remain open. I wasn't sure if that was supposed to have air to or from the rest of the fireback though. Thank you so much for your help!