Draft flow/top vent calculations...

[indaswamp]

Dave, do you think a diffuser plate/ baffle would help even out the flow of smoke and heat? I might have read about one on Widnelly and Donwne (spelling?). The one I saw was a large aluminum plate with holes drilled every square inch...think the holes were 3/8". Something like 1200 holes. The plate was situated about 6" above the smoke box on the burner. This evened the heat out uniformly across the entire smokehouse. I could very easily fabricate one as I have access to a MIG machine and scrap aluminum.

Whatcha think?

*edit to add link:
https://www.meatsandsausages.com/smokehouse-plans/smokehouse-baffles

*see bottom right pic. @ link above.

Also-I'm considering going to (2) 4" top vents for more draft when drying sausages if the smokehouse is full so I do not have to crack the chamber door. Of course I will fab up some aluminum vent covers too.

 

[daveomak]

Did you see the layer of "drain rock" on a wire screen... One member has used this method, that I know of, and says it's an awesome diffuser and heat stabilizer...

.. ..

 

[indaswamp]

Yea I saw that Dave. I would want it for safety as well. While smoking the 100# batch of sausages, I noticed quite a bit of drippings falling down to the bottom of the smokehouse. This would act as a good flame arrestor as well.

 

[indaswamp]

Yea, I imagine the rock is a great thermal heat sink to moderate temp spikes....

The hardi board does the same thing and once it heats up helps to moderate the temp. I thought about stacking fire brick along the inside bottom wall for a heat sink, might look at rock on a baffle now....or maybe coarse crushed fire brick???

 

[daveomak]

If you use it, have a drip pan so the rock doesn't get covered in grease.... The grease attracts mice and rats and.......

 

[indaswamp]

Alright... this afternoon I scoped out some of the modifications for the smokehouse. I located a 3" hole saw and will be drilling out the 2" holes to 3" holes. I only want 2 openings so I only have to be concerned with 2 vent covers instead of 4. I still have some aluminum plate left so I will be cutting donuts for inside the smoke house from that. I will also cut donuts for the outside with a tab. Turns out the roll of tape I found has a perfect 3" I.D. and 5" O.D. - awesome!

I will cut a 5" circle with a matching tab and this will be my vent cover. These will mount over the donuts above so the vent covers can slide on aluminum and not the wood siding of the smokehouse.

Worked on the corner brace to support the door as well...

Will stop by my buddy's shop tomorrow morning to have it welded up. I should have installed the hinges all the way at the top and bottom of the door, but I did not realize how heavy the door would be with the hardi board on it. This ought to fix it for good.

Gonna be in the top right corner. I have a ratchet strap holding tension on the opening to pull it plumb and square for installation tomorrow.

 

[indaswamp]

Dropped the pieces off to have them welded, picked them up at lunch. Knocked off around 3pm and rushed home to install. Took me about an hour buying hardware, lining everything up, drilling the holes, and bolting in place...

Door closes perfectly now! No sag! Diagonals measure within 1/16" of each other...close enough for me! Now to make the vents larger. Hope to get started on that tonight and finish up tomorrow....then a test run to check out the larger vents.

 

[daveomak]

Me likes the lining in the smoker body.. Yes me does..

 

[indaswamp]

Dave, You takin about the smoke deposits or the aluminum flashing over the hardi board?

 

[daveomak]

Yes, the aluminum flashing... That's a very nice lining and a good job installing it...

 

[indaswamp]

It was tedious and took a lot of time to install. Had to take my time and take good measurements to bend it. It is installed with aluminum nails so no zinc in the smokehouse.

 

[daveomak]

AND...... No electrolytic corrosion... You are two steps ahead of me...

 

[indaswamp]

Yep. I got that idea looking at ideas on the internet. I think the guy is an old member here on SMF, not sure if he posts any more though.

I'll tell ya Dave, I'm really impressed with that hardi-board...really moderates the temps once it heats up.

 

[daveomak]

It's hard to beat good thermal mass...

 

[indaswamp]

Yep. And it does not take too long to heat up like a cinder or brick smokehouse would. I like it a lot and glad I decided to go that route instead of just all wood.

 

[indaswamp]

Got the holes cut, but had to get creative and make a jig for the hole saw. I offset the 3" hole up and towards the front of the smokehouse. I did not want the center of the hole to be lower and needed more draft higher to clear stale smoke on the ceiling.

I had to draw a 2" circle and line that up from the inside with the jig on the outside, then screw the jig in place. and use the 3" hole saw cutting from the outside.

Once cut through the plywood, the jig held the hole saw in place to score the smokehouse wood plank.

Once it was scored about 1/8" deep, I no longer needed the jig and removed it for less friction on the hole saw.

Cut through the cypress plank and the hardiboard. I had to feather it once I got close to the aluminum flashing so as not to tear it.

Cleaned up the holes, vacuumed the dust, cut the flashing tube, wiped it down with acetone and put high temp silicone on it to install. Did you know a purina dog food can is exactly 2 15/16" in dia.? me neither until I started looking for the right size cylinder to hold the flashing tube in place for the silicone to stick and hold the shape...

Both sides are in place. I will let the silicone cure over night and finish it tomorrow. I have the aluminum disks and vent cover made, just got to clean them up and install and it's done.

 

[daveomak]

You dig pretty deep in that box of tricks, I see...

 

[indaswamp]

Thanks Dave. I come from a family of engineers; Dad was mechanical. Jut kinda how I grew up.

 

[indaswamp]

Finished up the vents today...

Plates cleaned up and prepped to install.

Tabs bent down, ready for high temp silicone...

Thought I snapped a picture of the inside after I installed the plate, guess not. Here is the outside plate and vent cover installed...

I used a metal roof screw with a neoprene washer for the vent to rotate on. I will need to find a small #10 spring steel washer and a small #10 2.5" long bolt for a permanent attachment point. This will do for now.

Whole Chickens are on sale...I'll be cranking her up tomorrow to see how this has changed the draft in the smokehouse.

 

[indaswamp]

I decided against the tab on the vent. Thought it might be prone to bend. Went with just the circle vent. I cut a 1/2" dia. round bar stock handle 3/4" long and then drilled a 3/8" hole where I wanted it installed. Had it welded from the back for a clean look. Just used a tiger disk to sand the weld down flat.