Baffle installation in Papa Bear.

[daveholl]

First, thanks to Coaly for his helpful Fisher info. Following his advice I bought a piece of 3/8" steel 10" x 16 3/4". But wasn't strong enough to lift it and manoeuver it in place. Changed to 1/4" and with some effort put that baffle in position. Us old guys don't have the strength we used to have.
The Jotul this stove is replacing developed 2 cracks. I've had the papa bear since the late 70's and it was fun cleaning, painting, firebricking to get it in shape.
Typically, here in Ohio, I burn 8-10 cords of ash annually. We have an old Findlay Bros. cook stove too.

Thanks again, coaly. you are a big asset to us Fisher lovers.
Dave

 

[coaly]

Thanks Dave, I always recommend 5/16 since that is the size that was used in later double doors, but the shorter span across the single doors should be fine with 1/4". To help get it in the larger Papa, I wedge wood across the stove tight to help hold it up until it's on top of the side support bricks. Papa is a long reach and the most difficult.
The added gasket material should not be needed if your door seal channel iron and back of door is wire wheeled clean for a good seal. It puts pressure on the hinges since there is no clearance for gasket material between door and seal. It does make it quieter closing, but a little leakage around the door also gives some needed oxygen above fire to allow smoke particles at baffle plate edge to ignite. Keep the hinge pins and draft cap threads greased and it should never wear out any moving parts.

 

[daveholl]

Thanks Dave, I always recommend 5/16 since that is the size that was used in later double doors, but the shorter span across the single doors should be fine with 1/4". To help get it in the larger Papa, I wedge wood across the stove tight to help hold it up until it's on top of the side support bricks. Papa is a long reach and the most difficult.
The added gasket material should not be needed if your door seal channel iron and back of door is wire wheeled clean for a good seal. It puts pressure on the hinges since there is no clearance for gasket material between door and seal. It does make it quieter closing, but a little leakage around the door also gives some needed oxygen above fire to allow smoke particles at baffle plate edge to ignite. Keep the hinge pins and draft cap threads greased and it should never wear out any moving parts.

I wanted 5/16" but the metal shop didn't have any. .On the unused 3/8" piece, I had welded 2 small rectangular pieces perpendicular to the baffle for brick support. That made it heavier yet. Didn't do that on the 1/4" piece. Good idea about wedging wood support for the baffle. I installed the gasket material before I read your info about not needing it. OK to try it that way for a season, or should I remove it now?
Dave

 

[coaly]

Older stoves were designed to have about 40% extra oxygen than required in the firebox to assure no starvation. That is what the air intake area is based on. (Jay Shelton, Woodburner's Encyclopedia) I don't know if door leakage was taken into consideration, but adding gasket certainly affects the air mixture since rough cast iron is not a machined sealing surface. That is my main reason to discourage gasket use.

Damage or stress depends on the door fit, hinge pin wear, gasket thickness and cement thickness.
The hinge plates are fitted with stove on its back, and door sitting centered on door seal. They are sometimes welded in place loose enough for flat gasket material to crush without undue stress. In rare instances it may be required. The test was if a piece of cardboard in the seal groove allowed door to shut and latch easily, there was enough room for gasket material to crush. Wear in the hinge plate holes and pins allows for more clearance. The channel iron makes contact on edges of channel and back of door. The center of channel iron makes contact with the raised portion on back of door, so there is no room for any gasket between the two pieces. When the door is latched, the space measured between door edge and stove face plate is the thickness of the channel iron web. Minimal flat gasket may be OK, but never round. The thickness of the gasket cement adds to the thickness. When an old gasket is replaced, the cement builds up and becomes a problem since people tend to add more cement and not wire wheel all the old cement off. It will bind at the hinge side and over tightening the door latch tends to bow the door. Compound the problem overheating the stove and you have a warped door. The gasket doesn't belong there unless you must. (Glass double doors DO use gasket material)

The rough texture of the cast door doesn't make a perfect seal, and the door drawings have a notation that machining is permissible removing no more than .050" from door sealing area.
If you want to get technical and really check the fit of machined surfaces, lay stove on its back and remove hinge pins. Dab valve grinding compound around edges where mating surfaces touch and work door in circles until you can see where surfaces touch. This is lapping two pieces to mate perfectly and is done on steam parts like flanges and seats. It will become gray where the two pieces match and when the same color all around, you have a perfect lapped joint. You can tell by the shade of gray. You will get 3 points of contact all the way around. It gives you better air control, but with baffle, the extra air from leakage can be beneficial for smoke particle combustion when all the oxygen that comes through intakes is used up low in the fire bed.