How important is the ramp in an arch?

[turnerburner]

I’m in the process of building a 2x3 arch and am wondering how important it is to have a ramp from the firebox rather than just a 90 degree transition. The firebox is 24”x24” and I plan on leaving 5” below the pan after the transition. the flue will extend 10” beyond the 2’x3’ pan to make room for a warming pan. With such a small a small arch will it make a big difference?

[barnbc76]

I'm not sure how much it affects it but I figure it must be enough if that's how the experts build them. I think the theory is the ramp forces the fire directly under the pan sooner and therefore you gain more heat rather than focusing all the heat in the one spot. Mine is about the same size as yours, and my ramp does slope gradually. Is yours a fuel tank arch?

[psparr]

You should only have about an inch or two under the pan at the back. Keeping the heat pushed up against the pan.

[maple maniac65]

I built my son a 2x3 with just a 90 degree elbow. Installed a small blower directly in the middle blowing straight up on the pans. He made 1 1/2 pints an hour.

[maple flats]

The plans for a Leader Half Pint evaporator call for a wall from the back of the firebox area to 1" under the pans, behind the wall it drops down to exit the arch at the stack. The wall forces the heat up to the pan.
You don't go to a tapered ramp unless the arch is 4' or longer.

[eustis22]

Here's my wall on my 2X3 Mason:

http://mapletrader.com/community/attachment.php?attachmentid=16964&stc=1

I think I put it within 2-3 inches of the pan bottom and I don't drop back down after it.

[turnerburner]

I plan on running a 100 cfm blower. Should I make any adjustments to the space below the pan to allow for the increase in air flow?

[Super Sapper]

Your restriction on your air flow will be your stack diameter. For a flat pan, if you have a 6 inch stack you need only 1.1 inches under the pan so I would go 1 1/2 at the most and on an 8 inch stack you would go 2 inches under the pan. If your stack goes out the back drop down the last 6 inches to the level of the bottom of your stack pipe. A blower will not matter as you are restricted by the stack diameter.

[maple flats]

eustis22, I see 2 issues on your bricking. At the grates, the area should be open much wider to get better air distribution of combustion air, regardless of whether you have a blower or not (if your grate is not wider than that, find something to make grate extensions to help, , a couple of angles iron placed in a VV aspect on each side with a 1/4-3/8" space on each side and between would help), secondly, you will get a better boil if you bring the vertical wall up closer to the pan, just for that 1 brick width, then back down to the stack outlet. It would also help a little to go 1 brick lower at the outlet. At that point you will get a buildup of light fly ash, then clean it out every few boils, rather than force it to go out the stack or possibly partially restrict the stack at that point.

[eustis22]

Dave. I am having a hard time visualizing this: "if your grate is not wider than that, find something to make grate extensions to help, , a couple of angles iron placed in a VV aspect on each side with a 1/4-3/8" space on each side and between would help"

the grate width is the width of the hole in the bottom of the stove. How can I make it wider?

[barnbc76]

I believe what he means is remove the bricks on either side of the grate to give your fire box more room, if you put wood on top of those bricks that wood will not burn as well as if it had grate under it.
The angle iron can be bed frames, in a v pattern one next to the other, it works well I did part of mine like that.

[maple flats]

OK, if that is the widest possible, try putting a piece of stove pipe under the grate with 3 sets of holes (5/16" diameter), one row top center and one each facing toward the outer edge of the opening at the edge of the grate. Then put a blower on to feed the pipe. You likely want 250-350 CFM on a squirrel cage blower. Search the web to find the best deal for a blower unless you have one. I recently got an email from www.surpluscenter.com saying they have blowers on clearance. See what they offer compared to other sources. In each case, compared your delivered cost, some places are low on price and more than make it up on shipping (and Handling).
Getting more air to the whole fire will give you a faster boil.

[eustis22]

My Hobby XL came with a blower (150 cfm, I believe). There is nothing under the bricks but metal stove floor. I am not seeing anything gained by removing them. Can this be explained further?

[berkshires]

My Hobby XL came with a blower (150 cfm, I believe). There is nothing under the bricks but metal stove floor. I am not seeing anything gained by removing them. Can this be explained further?

Eustis, I think what people are saying is that the way your grate is set up, it's only providing AUF to a fraction of the logs. Your current setup is something like this:

16986

Where the red logs in the middle get air, but the blue ones on right and left are sitting directly on your bricks, and getting no air.

I think the simple solution is to make/add a new grate. It should provide space for the air to get to all the logs, sitting perhaps an inch or two above the current floor. Excuse the rudimentary picture, but something like this:
16987

Does that make sense?

[eustis22]

it does...thank you