AUF question

[RileySugarbush]

I use a row of firebrick just inside the door like William does. Also, make sure you distribute the wood evenly when firing so there are no open spots for the air to bypass the fuel.

[maple flats]

Wood distribution is likely the biggest cause of the air bypassing the fire. Don't have any voids for air to bypass thru. I haven't in the past, but I'll try adding a row of firebricks just inside the door to see if I get an even better boil rate, good idea I hadn't thought of yet.

[Ken Letcher]

I use to have a Leader Half Pint, we added a centrifugal fan to the draft door. Not ever sure how many CFM the fan was, stole it off our old wood burner in the shop. But we run an electric cord to a switch box that we left on the floor right next to front door of the evaporator and then wired to the fan, the switch box has an on/off switch for when you are firing, and it also is wired through a rheostat (a light dimmer dial) so that we can easily adjust the air flow based upon our needs. You will find that sometimes you need to change air flow quite often, based on wood quality, stack temp, boil, etc., so the rheostat is extremely handy, and you don't have to worry about restricting air flow.

[Mark B]

Actually stumbled onto something that I think will work for auf. I found my old spray paint blower... I forget the make (cheapie Graco I think). Anyway, I have a a.c. motor variable speed control that I have adapted to it. My 2x4 is custom built so I am planning to trade for a few modifications including an adapter to the auf vent. If it all works out, I will post video in a month or so. Right now I have to get my uncles place ready for a renter in a month.

[mspina14]

I made a barrel stove and rigged up a blower fan.

stove 2.jpg

stove blower.jpg

I used a flexible metal dryer vent tubing, some black pipe, and duct tape to connect it to the bung hole in the barrel stove lid.

The blower was 125 CFM, if I remember. I had it plugged into a cheap rheostat that allowed the speed of the fan to be adjusted as needed.

barrel evaporator 2-16.jpg

Worked great.

Mark

[Sugarmaker]

AUF: some air is way better than none, too much and you will know it. Some trial and error on that. But keep in mind that thousands of gallons of syrup have been made in the old days with no AUF. Just because it seems like everyone is doing it, you don't have too. A rig set up to have good draft will roar on its own with no AUF help. The amount you gain from wood savings and or increased boil rate is going to be hard to see and maybe hard to justify with no electric in the sugarhouse. Maybe a 5 to 15% improvement in efficiency????
Just my 2 cents. Have fun. Try it and let us know. Pictures are always helpful too!
Regards,
Chris

[berkshires]

I have some other improvements/fixes I need to make to my evaporator, and limited time (baby!) So I will at least start the season with the other improvements but without the AUF. If time allows, I may add it mid-season. That'll give me an apples-to-apples comparison of what kind of improvement just that makes in boil rate.

Gabe