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

[coaly]

Welcome to the Forum,
I believe the stove pictured is a Papa Bear. (by the exposed area of side sheet around pipe) A good picture of the front will determine model for sure. But I'm betting on a Papa. (Mama takes up to 24 inch log, Papa takes 30 inch)

You already have a good design that prevents excessive loss.
A baffle will change the flow through the stove, so could still improve it some. (same design baffle as rear or top vent)
Depends on chimney. If you have a 6 inch insulated flue, yes I'd try it. If you have a larger flue, it's going to get dirty. Not excessive creosote, but will require more frequent cleaning.

Here's a picture of a side vented Mama. Notice the much smaller area around pipe on the side. The door will also cover the entire front of stove. Papa will have exposed front sheet at door sides between door and angle iron corners.

 

[Victy]

Hey Coaly, thanks for the info.. I am glad I found your forums. And much to my surprise.. I buy a Mama Bear and find out it is a Papa Bear.. And I see the difference on the front door you were telling me about.. Now I got to make her Pretty !

 

[coaly]

Now I got to make her Pretty !

Him !

 

[velvetfoot]

Hi. I don't have a Fisher, but I was wondering why not use a baffle made of ceramic material? It'd be lighter. I know that helped me when Quadrafire changed from a metal baffle. The 30 (or so) pound metal baffle was a bear to wriggle out and it had started twisting some on me.

 

[Victy]

View attachment 166452 Hey Coaly, thanks for the info.. I am glad I found your forums. And much to my surprise.. I buy a Mama Bear and find out it is a Papa Bear.. And I see the difference on the front door you were telling me about.. Now I got to make her Pretty !

Him !

Sorry, I drove a truck a called them all her! I will make (Him) Handsome

 

[coaly]

Hi. I don't have a Fisher, but I was wondering why not use a baffle made of ceramic material? It'd be lighter. I know that helped me when Quadrafire changed from a metal baffle. The 30 (or so) pound metal baffle was a bear to wriggle out and it had started twisting some on me.

The Fisher Creed;
Keep it simple.
Keep it cheap.
Make it last longer than you.

 

[Piney]

Coaly, In keeping it simple I just leave it alone. Our top vent Grandma heats our 1100 sq ft house fine configured as it was when it left the factory. Gases rise through a good 8' of single wall 8", then they 90 degree elbow into Class-A and exit through the wall through an insulated thimble arrangement into the T and head up 7 more feet. The shortness of the insulated pipe outside helps keep gasses hot but I certainly don't want to cool them anymore than I need to given that we have an outside chimney. So I'm a little afraid of a baffle. As much as we don't seem to get -60 much any more (Celsius) we do still dip into the -40s from time to time and it's -25 as I write this. The stove works great and I don't want to mess with it. I don't get a creosote build up.
I might put a baffle on the mama bear in the shop though and I thank you for the great info.

 

[coaly]

Grandma was made from 1976 to 1979 without a baffle.

They were improved in 1980 and supplied with factory baffle from 1980 to1988. The baffle was designed to reduce smoke from 60 grams to 6 for every kilogram of wood burned. The output was raised in manuals from heating 1500 square feet to 1750.
If you are closing a flue pipe damper at all, you're doing the same as restricting flow without taking advantage of other benefits of changing the flow in the firebox.

It does lower the flue temperature slightly, so there are going to be areas with warmer and colder temperatures that won't create enough draft, or cool to much due to extreme outdoor temps. You would benefit a lot with a 6 inch flue requiring much less heat, then be able to take advantage of the baffle.

Lowering the flue temperature is obviously going to create more creosote, with the same amount of particulate present. But the smoke particles that were present without baffle are greatly reduced by 10 times. So a slightly cooler flue does not necessarily mean more creosote when you are burning the excessive particulate.

For most of us in the lower 48, a stove without baffle allows too much heat to escape and changing the flow through firebox is a huge improvement.

 

[Piney]

Thanks Coaly.
That is food for thought. I knew about the 60/6g thing but never got to think about creosote formation being possibly promoted but with so much less particulates I might still end up being ahead on the deal. I'll give it a try. I've got some 3/4 plate laying around anyways. Nothing thinner handy. Thanks so very much for your thoughts.
I'd change the chimney but the 8" is paid for.
As far as flue dampers go, with a top exhaust like ours, has anyone ever lowered one really close to the stove top and claimed some baffle-like benefits came from that?

 

[coaly]

Dura-Vent kits supplied with some Fisher Stoves came with a short damper section (double wall about 4 inches long) that sat on the stove top. They are still available. A damper only adds resistance to flow. It doesn't hold heat back, or increase firebox temperature. It decreases it, since it slows what goes out, cooling chimney, affecting the stove by less draft. That makes the air pressure higher in the stove preventing the available atmospheric pressure from pushing in as much, no matter how far open the intakes.
Slowing the flow with flue damper through intakes also reduces turbulence needed for mixing oxygen with flammable gasses expelled from wood. The faster it moves through the intake, the better the mix. Position of wood pieces has a lot to do with it as well, which is why the deeper stoves that oxygen has to travel down between the logs burns with a different characteristic. More oil burner like with a roar in the stove when allowed to burn that hard.
That was the intent of this thread, to adapt the baffle used in the double doors to increase efficiency of the single door stoves.

The baffle reflects some heat downward causing higher firebox temperatures. That's #1 key to a cleaner burn. (the thicker the baffle, the more heat it absorbs like a colder spark plug, so thin is best, but warpage becomes an issue) It also keeps the hot gasses in the firebox longer, by giving it a longer route out. It adds turbulence, as explained above and directs all flame over the hot edge where smoke particles are ignited. (providing oxygen is not entirely used up through fire)
There is a lot more info about baffles in the Woodburners Encyclopedia.

 

[Piney]

Thanks. I'll chuck the 3/4 plate back on the material pile and find something thinner.

 

[coaly]

5/16 has been proven to stay flat and is the same thickness as your stove top.
You'll want to keep your smoke space larger than the minimum (50.24 square inches) since this exhaust opening is proven to work well with connector pipe and insulated chimney straight up off the stove. Your elbow, T and horizontal run all adds resistance that requires more heat left out to overcome. (cap and screen adds more) I'd start with a 3 inch space between plate and lower bend instead of 2 inch. Your lower temperatures may require more. I tested them with 6 feet connector pipe and 9 feet of insulated Class A 6 inch chimney. You will be leaving twice the amount of heat up the flue, so you see why I recommend 6 inch since it pays for itself in fuel usage over time. You won't get wide open throttle reduced to 6, but that is not a factor for us "Southerners" that only use our stoves 6 months out of the year.

 

[Piney]

Thanks! Good! I do have that 90 elbow and 3' of horizontal into the T to battle. If Grandma was further from the wall I would have used a couple 45s with a sloped rise just to make the flow easier instead of that 90 (grandma sits 18" in front of a proper cement board covered in radiant insulation heat shield - raised 2" off the floor and out from the wall 3" so convection air flow keeps all cool and safe). The spaced off cement board installed with connectors that don't go through into the combustibles would be enough but that reflective foil layer sure adds an amazing bit extra. Bottom line is there is no real room to eliminate the 90, which I would like as ease of flow matters).
I do run the Fisher hard sometimes hence the 8" chimney is a good thing for us. It's bright sun today and 10am but still -25 C. Our heating season is different for sure. Our stove is never let to go out for 7 months of the year and lit at least 1/3 of the other days for single burns in the early morning.
Grandma works hard.
I am going to have to get something made up in 5/16. I've been looking around the place and I've just got nothing other than maybe cutting and welding a bunch of leaf spring together. Or 4 layers of propane tank wall. But both would be curved. Though I could beat the tank layers flat before welding. This would still be better than nothing (for now) though. I could make the 'right thing' later when I get materials. Or I could load a generator and tools up on the sledge and use the snow machine to sled to an old sawmill and cut some sheet pieces out of abandoned equipment - that might work too. But strikes me as too annoying at the moment.
But I'll get it done.
You've got me motivated. I'll start at 3" as you recommend. Will get in the way of the bigger rounds I often burn, though.

 

[Northern Light]

I have a Fisher insert that has been converted into a free standing stove. it works great but does not have a internal baffle. I have measured for one and it needs to be 18 inches wide but i really don't know how long it needs to be. How far out to the front of the stove does it need to extend.,, Looks like 12 or 14 inches would work, What is your recomendation ? Also, I was wondering if there was any change in the amount of pipe creosote. My instillation wants to creosote in the last couple of feet of the chiminy, at the cap. If I put a baffle in I would expect the exaust to be cooler and that might make my creosote problem worse. Your thoughts please. David

 

[Northern Light]

Looks like mine. Did you install your baffle and what was the result? Do you operate the stove with the damper as before? Philippe

 

[WestM]

What a difference an bit of an angle makes.

I discovered this site about a week ago. Ive got a Polar Bear Insert. Bought new in 1983. At the time it came with a Cat Converter that closed into the flue, as it was attached to the damper handle. This was the "latest" improvement.

When the CAT became toast, I went back to the damper and the "baffle" plate that came with the insert. 4" x 18"(width of the firebox) with a 2" tab at the front.

Since then, I got a Steel Liner for a direct connect, so I don't spend BTUs heating up the hearth and creating creosote. And have been experimenting with smoke shelves/baffles inside the stove, using steel stock, firebricks and that 18x5 piece of 1/4" steel plate. Basically Flat..
SOOO, what did I know???

After reading Wots Wot here I improvised with what I had before running out and fabricating a steel baffle.

I angled the rear firebrick part of my "shelf" and wedged the front part - the Steel Plate about 25degrees....and as I said at the top...WHAT A DIFFERENCE a bit of ANGLE makes.

My only offering as for now is a Blower fan recommendation.

I have been using these since 1978...on an earlier Fisher GrandMa....How to make Heat from Stove Art will follow at some point WRAPped HEAT ART that I made for the GrandMa Bear.

The latest Dayton is inn the Blower I made for the Polar Bear Insert. I use the lower CFM for move air to the far from the stove room, tucked in the upper corner of the doorway jam.

Those 1978 fans are still working. I use the 55cfm and the 70 cfm. 1800 RPM/2000RPM. Low wattage - 13 and 11

Just a list...not a ToBuySite.
http://www.electricmotorwarehouse.com/square/

Thanks again from a much Warmer House. Youse got the angle...

 

[Willys wood]

I have been heating with Fisher stoves for thirty years and they are the best.I have two Pa Pa Bears,one in house and one in garage.House stove is late 1970s and the garage is 1980s.I just put a plate in the house stove and it works great.Thanks for the info.

 

[lhcb]

This 5 minute baffle plate install is the easiest way I've found to reduce smoke and prevent intense heating of the rear outlet elbow or pipe. (20 years late, but better late than never) And possibly the best solution for anyone who can't afford to upgrade to a new stove; Approximate cost under $25.

This pertains to a rear vent, but can be altered for a top vent as well. Simply measure across the inside of your stove width. Obtain a piece of steel plate 5/16 thick from a local steel fabricator or supplier 1/2 inch shorter than this measurement. I made mine (15 long X 8 inches wide for a Mama Bear. Mine cost 1.42 / lb. weighing 11 lbs. Cost $15.62) The only other materials required are 2 firebricks available at mason supply or stove retailer. (the type that line your stove 4 1/2 X 9 X 1 1/4 thick) Papa is the same height stove for brick supports, just a little longer plate to reach across the stove.

1). Simply set the firebrick on edge against the side walls on top of the first course a couple inches from the rear wall. Upright for a Mama or Papa works great, sideways for Baby.
2). Insert the plate through the door, tilt it sideways and rotate until it is between the side walls.
Raise it to the top, and set it on top of the firebrick.
3). By sliding it rearward, you can let it tip down in the back until it's at about a 45* angle in front of the rear vent. Many rear vented stoves have a short shelf under the outlet pipe to set it on as well.
4). Make sure the opening above the plate to stove top is an acceptable size opening.
This can be adjusted by moving the bricks fore and aft to change the angle and opening if required.

The only technical measurement is the opening above the baffle plate. This must be at least as large as the square inch area of your outlet. (6 inch round formula is pi X r squared or 3.14 X 9 =28.26" square inch opening. An 8 inch Grandma or Grandpa would be 3.14 X 16 or 50.24 square inch opening) This is about 2 inches from the top, all the way across any model Fisher Stove. You can adjust it to your exact size, but I find it doesn't make much difference making the opening exact.

I found once in place, this is quite solid and doesn't want to move. It also doesn't noticeably decrease firebox size.

The intense heat that normally would heat the rear outlet elbow now goes up the plate and burns the unburned smoke particles before they get to the outlet. This also directs the heat to the stove top instead of in the direction of the exhaust. (rearward) Huge reduction in smoke. (about 90% reduction as calculated in EPA testing with and without baffle) Nothing permanent is added to the stove. This would also be the perfect area to add a secondary burn tube to admit oxygen at this hottest area.


I was going to fabricate an angle iron frame to support a baffle plate, and realized I had some old firebrick laying around that the plate could set on instead. Much cheaper than angle iron, and some single door stoves use this second course of brick above the first at the rear anyway. I positioned the new baffle plate that cost a total of $16 and 2 bricks in the stove in less than 5 minutes. I expected to need to cut the corners of the bricks on angles, but the plate sat right on the full bricks in the Mama Bear shown below. Extremely simple !

 

[lhcb]

hello brother woodies Here is my question to throw out to you I have a mama bear The Front door has a pat pending in the casting .The handle is a metal spring that is not a tight wind spring. The legs are a straight angle iron design and I do have the silver colored feet. So my question is what year do you think she is ? Ihave looked under and around can't see any weld id The house was built in 76 so was thinking it was bought then. Next question I'am wondering about is the baffle both Coaly and Brother Bart have given good advise But looking into the stove I don't have the shelf under the exit just a 6" hole So but putting a brick on top of the course that is there what is the plate going to rest on in my case.I have seen plates sitting on angle iron leg frames

 

[coaly]

Easier to cut bricks to set the baffle on. You can drill holes and put nail or bolt through to hold in place as shown below in this recent picture inside an Insert;



It's better to not have the little shelf under outlet pipe so you can drop it a little more in the back and tilt upward until it touches outlet pipe. Making a cardboard template is the best to get it the right size. angle upward towards front leaving about 2 inches space to top. You can then slide side bricks fore and aft to adjust for chimney draft.
'76 would have a tight wound stainless spring. (if original)
Bear feet or chrome ball?
4 or 5 fin draft caps?

 

[begreen]

This is such good info it should be distilled into a wiki article. It is helpful info for many old stoves.

 

[lhcb]

Easier to cut bricks to set the baffle on. You can drill holes and put nail or bolt through to hold in place as shown below in this recent picture inside an Insert;

View attachment 172501

It's better to not have the little shelf under outlet pipe so you can drop it a little more in the back and tilt upward until it touches outlet pipe. Making a cardboard template is the best to get it the right size. angle upward towards front leaving about 2 inches space to top. You can then slide side bricks fore and aft to adjust for chimney draft.
'76 would have a tight wound stainless spring. (if original)
Bear feet or chrome ball?
4 or 5 fin draft caps?

Easier to cut bricks to set the baffle on. You can drill holes and put nail or bolt through to hold in place as shown below in this recent picture inside an Insert;

View attachment 172501

It's better to not have the little shelf under outlet pipe so you can drop it a little more in the back and tilt upward until it touches outlet pipe. Making a cardboard template is the best to get it the right size. angle upward towards front leaving about 2 inches space to top. You can then slide side bricks fore and aft to adjust for chimney draft.
'76 would have a tight wound stainless spring. (if original)
Bear feet or chrome ball?
4 or 5 fin draft caps?

thanks for the info My MaMa has a four fin draft caps and the spring on the handle in my guess isn't tight woven But to the shelf Ido see the placement of the nail or bolt to hold the bricks from falling in The Stove in the picture is a top vent and mine is a rear exhaust so the plate would sit about level resting on the bricks on the side and the one in the rear. There was a post about bending the edges on the plate any other opinion as to the reason other tha maybe holding bricks to the side I wasn't sure if there is a angle on the plate I did own a mama back in 77-78 and she had a welded plate that got the droops after a few years Lost her in a Big D

 

[coaly]

The picture is an Insert with flat top. The angle would be better with rear of plate resting on brick retainers. That tends to encroach on loading room, so some like to keep it higher. It does cut down the baffles effectiveness and flow. It increases flame impingement which absorbs more heat into plate decreasing burn zone temperature. The overall firebox temperature increase makes up for the detrimental factors the baffle creates.
Rear, side or top vent still angles the plate the same way. You don't want it level.
Keep the plate at rear against bottom of vent pipe.
Raise front to give proper smoke space. (measured between front edge of plate and bottom bend) This will approximate the 30* angle tested and used in later double door Fishers for smoke reduction.

 

[lhcb]

ok

The picture is an Insert with flat top. The angle would be better with rear of plate resting on brick retainers. That tends to encroach on loading room, so some like to keep it higher. It does cut down the baffles effectiveness and flow. It increases flame impingement which absorbs more heat into plate decreasing burn zone temperature. The overall firebox temperature increase makes up for the detrimental factors the baffle creates.
Rear, side or top vent still angles the plate the same way. You don't want it level.
Keep the plate at rear against bottom of vent pipe.
Raise front to give proper smoke space. (measured between front edge of plate and bottom bend) This will approximate the 30* angle tested and used in later double door Fishers for smoke reduction.

that helps clear it up mine doesn.t have a full rail for the brick just pieces welded every so often but as I see the rear brick will be cut so the plate will rest on the brick but just below the opening the front will be cut so to achieve the 30 degree angle

 

[coaly]

You got it.
Later stoves (Insert pictured was '79 up) use a solid length of angle iron for brick retainer on sides and back. They work the same and the older style with "clips" are positioned at the joint in bricks so each clip holds corners of 2 bricks. They can warp upwards but cause no harm.