Simple Baffle Solution for your old FISHER ! More Heat Less Smoke under $25

[Piney]

You have the angle iron going longwise, did you do that to help with the warping?

Yes. But I have plenty of scrap and can weld up any design, even grid it, if I want - so messing around is no big deal. Not much matters, it seems, except bulk. Beefier bits don't warp as much, if at all, or rust very fast.

 

[Fat wood]

I would like to say thank you for the baffle specs. I found a mama bear on market place cheap. So i had a weilder cut the top and weild two brackets to support the baffle plate. Good thing, i can take the plate out if i desire. I used your exact measurements. I took out my epa stove because of cost of fire brick and combustion box. Now i have a life time stove. A shorter burn time, but cheaper to maintain!!

 

[Frankdozer]

Looks Great
FISH AWAY

 

[bacato]

I just picked up a Papa Bear. Looks like the baffle plate is limited to 17.5" wide by 14" deep. The limitation being the 14" deep because that's the diagnonal measurement of the door opening. Does this sound right? Just trial running this with a piece of cardboard, you must slide it in long ways, then rotate it inside the firebox before setting it in place. Angle this plate upwards towards the lower bend of the top, that leaves a smoke opening of roughly 4" x 17.5" -- that's more than twice the opening size of the 6" pipe. Mine does have the factory baffle welded to the back, roughly 4"x6" and sitting at an angle. I might be able to prop my 5/16" plate on that, what is the optimum angle up towards the lower bend of the top?

 

[coaly]

14 being the max works for Mama Bear. The deeper Papa Bear depends on the second course of side bricks when they are in the way, or rear/side vent that may or may not have the short plate below the outlet pipe you’re describing. That was normally flat, below pipe, that the new baffle can set on.

A square 8 inch call size flue is normally 7.5 square totaling close to 60, so I use a 14 in them. I have been able to cheat a baffle out toward the front and cover the opening in back with a brick on top. That brings it out to about 18 inches. They can only go up to the pipe, and don’t seal well, but the little that leaks past only adds a little get up the stack. The flow is forward.

I never had to make one larger than would fit through the door since everyone near me is too cheap to install a 6 inch liner and uses the original 8 inch existing flue.

 

[bacato]

Thanks Coaly. I'm guessing a baffle coming out 14 inches from the back on my papa bear would probably work though. I need to replace most all of the firebrick in there, right now I don't think there's even a second row in it. You do recommend the front of the baffle being higher than the back right?

 

[coaly]

Thanks Coaly. I'm guessing a baffle coming out 14 inches from the back on my papa bear would probably work though. I need to replace most all of the firebrick in there, right now I don't think there's even a second row in it. You do recommend the front of the baffle being higher than the back right?

Yes, aim it toward the lower bend in top.

 

[coaly]

Set baffle on sideways brick on rear wall. Make cardboard the inside width angled upward toward lower bend. Then wider at front the width of stove walls. If you set bricks on sides to support plate, you can bolt or weld angle iron to plate sides to prevent bricks from falling in, or drill holes at edges and insert long enough bolts pointing down to keep bricks against walls.

 

[bacato]

Here's my rendition in my Papa Bear.

 

[MCP]

Here's my rendition in my Papa Bear.

View attachment 330725

Looks good. What size plate did you end up using on the papa bear?

 

[bacato]

My baffle plate for the Papa Bear is 17" wide by 14" deep - I went with 5/16 plate. The 14" deep limitation being because that's the diagonal measurement of the door opening (that makes the front to rear direction). Across the inside is the 17" measurement. Could probably go a bit more than 17 but it makes it easier to turn around in there once you slip it inside. There's 1" on each side for it to sit on top of the fire bricks..

 

[MCP]

My baffle plate for the Papa Bear is 17" wide by 14" deep - I went with 5/16 plate. The 14" deep limitation being because that's the diagonal measurement of the door opening (that makes the front to rear direction). Across the inside is the 17" measurement. Could probably go a bit more than 17 but it makes it easier to turn around in there once you slip it inside. There's 1" on each side for it to sit on top of the fire bricks..

Thanks!

 

[cyclopsimages]

Glad I found this place! New to this forum and hopefully someone can help me out. Here goes:
I just purchased a rear vent fisher wood stove without the original angle brackets for the smoke shelf. That is not a problem for me to add. I know that the angle for the shelf should be approximately 30 degrees coming up towards the front. What I cannot seem to find are any original photos so I asked Chat GPT and it said that the Bob fisher original smoke shelves for a rear vent had a notch cut out because while the shelf went tight to the rear wall the shelf edge was 2" down from the top of the flue collar. Meaning most of the rear vent was in the fire area with only 2" up in the smoke shelf. Is this correct? Or did the smoke shelf go flush to the rear wall and have the entire rear vent up in the smoke shelf area? If anyone knows, please let me know. Thanks!

I have attached an extremely crude drawing of what I am referring. Shelf angle is wrong etc etc and my drawing ability is horrible but I believe it will suffice to see what I am talking about. Is it diagram 1 or 2 or sometimes either depending chimney config? Thanks in advance.

 

[coaly]

Below the vent opening so all exhaust rises up the plate and drops down. The corners that were notched are at the front.

 

[cyclopsimages]

Below the vent opening so all exhaust rises up the plate and drops down. The corners that were notched are at the front.

Thanks! I have seen the notched corners at the front. I assume that this was to allow more to get into the smoke shelf yeah?

 

[coaly]

Thanks! I have seen the notched corners at the front. I assume that this was to allow more to get into the smoke shelf yeah?

Allows more heat into front corners to prevent stagnation, for more even heating of surfaces.

 

[Frankdozer]

Allows more heat into front corners to prevent stagnation, for more even heating of surfaces.

Mines not notched …… should I ? Not notched for 10 years.

 

[coaly]

Mines not notched …… should I ? Not notched for 10 years.

Probably won’t notice a difference.

 

[danny_discus]

How does this look for a grandpa bear? Is the front of the plate in a good spot or does it have to be further back so it’s behind the stove top bend? This is a top vent model.

 

[coaly]

How does this look for a grandpa bear? Is the front of the plate in a good spot or does it have to be further back so it’s behind the stove top bend? This is a top vent model.

This is fine, of course depending on chimney.

 

[danny_discus]

Thanks coaly, the chimney setup is a 30 ft 8 in double walled insulated liner that goes up a brick chimney.

 

[ponderosa77]

So this year i finally took some time and built a baffle. Unfortunately I neglected to take pictures as i built the baffle only of the installed unit.
2 pieces of .25" plate 26.5"x8". Overlapped them by about an inch and welded some angle to the one so i could slip fit them together once they were in the fire box. Final plate worked out to be around 26.5"x15". I installed a 2nd row of firebrick in the back of the box to act as a shelf as seen in some other people's setups. Then I took my diamond wheel and cut 2 more bricks on an angle to allow the baffle to prop up inside the box. This leaves the ~2" spacing for proper exhaust venting for the 8" flue.

View attachment 81240View attachment 81241View attachment 81242

Seems to really do the trick!!

View attachment 81243View attachment 81244

Lots of heat pouring from the stove and LESS going up the flue!
So glad I took the time to build one this season!

I believe I have the Grandpa Bear.

Quick firebox measurements indicate 27 inches wide, so I believe a Grandpa Bear baffle would need to be 26.5 inches, correct?

Mine has an 8 inch rear outlet. I estimated a 13 inch depth but Lcj7 cut his to 15 inches.

A quick online search shows a cost of over $100 total to ship a 15x26.5 5/16 A-36 plate.

Before I look around, can someone check my measurements? (Measure 2x cut 1x)...

 

[ponderosa77]

I believe I have the Grandpa Bear.

Quick firebox measurements indicate 27 inches wide, so I believe a Grandpa Bear baffle would need to be 26.5 inches, correct?

Mine has an 8 inch rear outlet. I estimated a 13 inch depth but Lcj7 cut his to 15 inches.

A quick online search shows a cost of over $100 total to ship a 15x26.5 5/16 A-36 plate.

Before I look around, can someone check my measurements? (Measure 2x cut 1x)...

26.5 might be just a little too wide to fit. I have a cardboard template and will try a width of 26. A depth of 15 inches at a 30 degree angle will also not work in my stove. It looks like 12-13 inches in depth would be better.

 

[ponderosa77]

26.5 might be just a little too wide to fit. I have a cardboard template and will try a width of 26. A depth of 15 inches at a 30 degree angle will also not work in my stove. It looks like 12-13 inches in depth would be better.

Came across some junk angle and am starting a baffle cage with the idea of using it to hold firebricks. None of these are my welds. I just cut the scrap down to 26in x 12in. I will flip this over and lay the bricks into the framing.

 

[ponderosa77]

I ended up removing the legs and just propping the shelf up on bricks so I could fit it inside the stove.

Observations:

• This design may not do much in the way of reducing smoke output but one thing is clear immediately: there is more heat in the stove and less out the flue.
• I am actually astounded how quickly the stove reached 500 and how this baffle reduced the speed of flue temp rise. The simple explanation is it caused the stove temp to rise faster and the flue temp to rise slower. It feels safer this way.
• It seems to keep more heat on the fuel as well, which seems to make coals easier as opposed to just vaporizing the wood.
• I have not had to move the flue damper at all. I can leave it full open and only adjust the air caps.

Right now the stove is idling at 600 stove top and 400 flue temp.

I also took the time to re level the stove and improved the stove pipe sections, cleaned everything, and swapped 44 inches of stove pipe with a section of chimney that hangs below the ceiling box. Doesn't look as nice as black pipe but it performs nicely.

I also added some flat gasket tape to the stove channel to help seal the doors. Anything thicker than 1/8 would be too much but this reduced a lot of air leakage around the doors and made the stove safer to control through the air caps.

I don't expect the scrap steel to last very long but I'd say this is a successful experiment.