Fire box to arch ratio?

[mol1jb]

Looking ahead to next year I will be constructing a 2x6 to compensate for increased taps. Just in the design phase now. In general what is a good ratio for firebox to arch? I would guess 1/3 firebox 2/3 arch based on what I have seen but that is just a guess. Anyone know?

[motowbrowne]

Looking ahead to next year I will be constructing a 2x6 to compensate for increased taps. Just in the design phase now. In general what is a good ratio for firebox to arch? I would guess 1/3 firebox 2/3 arch based on what I have seen but that is just a guess. Anyone know?

I think most 2x6 rigs have grates about 30" long. It's my opinion that a 2x6 evaporator wastes a lot of heat up the stack. There's just not a lot of pan between the firebox and the flue. I tell everyone who is in the market for a 2x6 to strongly consider a 2x8. A 2x8 will cook more sap faster, and more efficiently, and they don't take up much more room or cost much more. Just something to think about. Of course I'm currently running 360 taps and cooking on a 4x14. I also am very happy with a 20" bar on my 90cc chainsaw, just to give you some context for my advice. Perhaps a grain of salt is appropriate.

[RileySugarbush]

I just bumped up from a 2x6 to a 2x8 and have seen tremendously better efficiency. I second that recommendation.

[DocsMapleSyrup]

I agree many arches are built approximately 1/3 firebox to the entire arch. I built mine with AOF/AUF and extended the firebox on my 2x8 to have a 54" firebox. I did this to have 1/2 of my drop flue pan exposed to flames directly. I asked some questions as you are doing on the trader and opinions varied quite a bit. However, I decided because I had the AOF/AUF that I would stay with a bit larger firebox. There are many with AOF/AUF arches who have the firebox 1/3 the length of the arch that I believe work fine. I do like mine. If I were to do it over, I would consider bringing my firebox somewhere near 48". Not that mine doesn't work well, I just think I might be able to have gotten by with a little smaller firebox. I really don't run mine over 1000 degrees and usually am in the 750-900 range.

I do agree with Motowbrowne and RileySugarbush on going to a 2x8 arch for the reasons mentioned above. It cost me $500 to go to from 2x6 pans to 2x8 pans but am glad I did. It now gives me some room to grow and I think I am able to get better efficiency with the longer arch/pan set than if I would have purchased the 2x6 that I thought I was going to purchase.

Below is the thread I started of my arch build and there are a few photos showing the size of the ratio of firebox to arch.

http://mapletrader.com/community/showthread.php?26583-2x8-Arch-Build

[wiam]

My 2x6 had 24" grates. I don't think you would want 36" grates. Your wood needs to cover your grates length. I burned 18" wood in that and had problems with forced air not going through the wood until I layed a 6" wide piece of flat steel across the front of the grates. I also believe an 8 foot rig would be more efficient as my stack temps ran quite high.

[Robert K]

I agree , make better use of the same fire and go with a longer pan. Have you ever seen a 4x8 evaporator? No
Excessive heat up the stack could be put to better use boiling on a longer pan.
Just my 2 cents.

[mol1jb]

I think my main issue on a 2x8 would be having enough taps. I will be going from 60 this year on a 2x4 oil tank arch with buffet steam pans to 150 taps next year. I was thinking along the lines of 24 in deep firebox and aof.

[BAP]

Do you have more than 150 taps available so that you would be expanding again?

[mol1jb]

Also my max taps will be in the ballpark of 300. In feel that if I did need more effeciency I would go RO.

[Bruce L]

I agree , make better use of the same fire and go with a longer pan. Have you ever seen a 4x8 evaporator? No
Excessive heat up the stack could be put to better use boiling on a longer pan.
Just my 2 cents.
Actually Robert,a neighbor of ours has a 4 X 8 evaporator,boils like crazy,but I also thought when I observed it that you may as well have the stack directly over the fire for the amount of heat loss. I had a 2 X 6, extended it by 2 feet,but couldn't get it to boil for awhile,only because I hadn't moved the ramp back,once corrected it worked great. Our old natural draft evaporator was 3 X 16 ,current setup is 3 X 14, enough heat it could have probably been 4 feet longer. There is no doubt a formula, but I think narrow and long work better than wide and short,saves wood too

[motowbrowne]

Also my max taps will be in the ballpark of 300. In feel that if I did need more effeciency I would go RO.

300 taps on a 2x6 is a lot. Heck, 150 is kinda a lot. Of course you haven't told us if you're buying a flue pan, or flat pans. I ran 400 taps on my 2x10, and it was OK, but I had a lot of long boiling days. Now I think it's the cat's meow to cook a whole days worth of sap in 3 hours. A 2x8 really won't require that many more taps. If you were only gonna run 50 or 75, maybe a 2x8 would be too much cooker, but I don't think it's at all unreasonable to have a 2x8 for 150 taps. Again, it's mostly a question of efficiency. You have an opportunity right now to make a more efficient rig for not much more money. Obviously it's your call to make, just making sure you know what the choices are.

[motowbrowne]

Actually Robert,a neighbor of ours has a 4 X 8 evaporator,boils like crazy,but I also thought when I observed it that you may as well have the stack directly over the fire for the amount of heat loss. I had a 2 X 6, extended it by 2 feet,but couldn't get it to boil for awhile,only because I hadn't moved the ramp back,once corrected it worked great. Our old natural draft evaporator was 3 X 16 ,current setup is 3 X 14, enough heat it could have probably been 4 feet longer. There is no doubt a formula, but I think narrow and long work better than wide and short,saves wood too

A 4x8, that's just ridiculous. Does it have a 4' flue pan?

[Bruce L]

I believe it is a 4 foot flue pan,but I would have to take another look at it to be sure,could possibly be 6 foot with a 2 foot syrup pan,years since I have seen it

[mol1jb]

300 taps on a 2x6 is a lot. Heck, 150 is kinda a lot. Of course you haven't told us if you're buying a flue pan, or flat pans. I ran 400 taps on my 2x10, and it was OK, but I had a lot of long boiling days. Now I think it's the cat's meow to cook a whole days worth of sap in 3 hours. A 2x8 really won't require that many more taps. If you were only gonna run 50 or 75, maybe a 2x8 would be too much cooker, but I don't think it's at all unreasonable to have a 2x8 for 150 taps. Again, it's mostly a question of efficiency. You have an opportunity right now to make a more efficient rig for not much more money. Obviously it's your call to make, just making sure you know what the choices are.

Thats good info. I appreciate it. Currently a flue pan is not in the budget, unless I find a good deal on a used one. Hopefully in the future years it will be.

[blissville maples]

2 time world champion maple producer, lol what