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questions on first insulated cabinet build
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OmahaRed
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PostPosted: Fri Aug 29 14 7:31 pm    Post subject: questions on first insulated cabinet build Reply with quote

I've made a few offset cookers over the last several years, and have now decided to make a fully insulated reverse-flow cooker. It's going to be a monster. Interior dimensions are roughly 3' deep 5'wide and 3.5' tall for the cooking chamber. The firebox shares the width and depth. My main question is how big do i need to make the channels for the hot air to get from the firebox to the cooking chamber? I've provisioned for 2 (one on either side of the cooking chamber) channels measuring 22" x 1.75" Is that enough? is it overkill? And with a cooker that big, is there a specific volume my exhaust stack needs to be? I've used the pit-building calculator for my other builds, but this is obviously not in keeping with the traditional offset calculations. Any input would be greatly appreciated fellas

Red
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Painless
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PostPosted: Sun Aug 31 14 12:49 pm    Post subject: Reply with quote

I am also looking to build something similar.
I would assume that normal pit ratios would still apply.
From what I have seen the big issue with these pits is getting the heat into the cooking chamber evenly - I have seen many that burn any food close to the FB opening. Im personally looking to use a perforated baffle plate so that the heat/smoke can come through into the CC as it moves upward.

I am very interested in anyone who has anything to comment about these pits or answers to the question above.
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Wreckless
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PostPosted: Sun Aug 31 14 8:31 pm    Post subject: Reply with quote

Painless wrote:
I am also looking to build something similar.
I would assume that normal pit ratios would still apply.
From what I have seen the big issue with these pits is getting the heat into the cooking chamber evenly - I have seen many that burn any food close to the FB opening. Im personally looking to use a perforated baffle plate so that the heat/smoke can come through into the CC as it moves upward.

I am very interested in anyone who has anything to comment about these pits or answers to the question above.

I stumbled across some perf plate for one of my first backyarder grill / smoker combos using the perf plate on the grill section and vertical smoker on the end. It worked awesome in doing exactly what you described, letting lots of good heat through and without direct flare up of flames on the grill section. The grill section being closer to what you will experience with the vertical cabinet, I think you are on to something there Painless. Cool
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k.a.m.
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PostPosted: Mon Sep 01 14 9:55 pm    Post subject: Reply with quote

OmahaRed, are you planning on a reverse flow type or just openings to feed the cooking chamber?
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Hotdog
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PostPosted: Wed Sep 03 14 8:56 am    Post subject: Reply with quote

Omahared....... Im building my 2nd R.F. cabinet smoker. Mine are smaller ....2 ft X 2 ft and 4 ft tall. My openings are the same size about 20" by 3". My first one had openings of about 15" x 2". I felt like it kinda forced the heat threw the openings. Im wanting more of a lazy heat flow this time.....we will see Laughing . I did have to use a water pan to even out the temp, but later found I liked the extra moisture in the cooking chamber. Id post pictures but not to computer savvy here. I am taking pictures and will have my son~in~law post them when my build is done. I would highly recommend painting between the inner and outer skins. good luck man!
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KCbbq
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PostPosted: Wed Sep 03 14 11:58 pm    Post subject: Reply with quote

[/quote]I would highly recommend painting between the inner and outer skins.[/quote]

out of curiosity, why this recommendation?
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Smokin Mike
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PostPosted: Thu Sep 04 14 12:30 am    Post subject: Reply with quote

KCbbq wrote:
Quote:
I would highly recommend painting between the inner and outer skins.


out of curiosity, why this recommendation?


Condensation that occurs between heating and cooling cycles results in rust.
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OmahaRed
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PostPosted: Fri Sep 05 14 9:17 am    Post subject: Reply with quote

Yeah, it's going to be a reverse flow style. Full separation between firebox and cooking chamber by water pan. heat "ducts" running up both sides of the cooking chamber. just wanted to know how big to make them. is 22x2 big enough if there's 2 of them? seems like it should be. not likely going to paint. at 1/4 inch plate coated in grease and smoke, i'm certain the walls will outlast my ability to cook.
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OmahaRed
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PostPosted: Sat Sep 06 14 11:26 am    Post subject: Reply with quote

Also, where is the best place to get hinges, slam latches and insulation?
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Smokin Mike
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PostPosted: Sat Sep 06 14 8:40 pm    Post subject: Reply with quote

OmahaRed wrote:
Also, where is the best place to get hinges, slam latches and insulation?


A lot of folks get those types of items from McMaster Carr; http://www.mcmaster.com/#

You can get bullet hinges and some spring handles also from; http://kck.com/

I got my slam latches here; http://www.amazon.com/gp/product/B00BQK7VBY/ref=oh_aui_detailpage_o05_s00?ie=UTF8&psc=1
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OmahaRed
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PostPosted: Sun Sep 07 14 12:05 pm    Post subject: Reply with quote

Holy cow. The slam latches i was looking at were 550 dollars EACH. that's a hell of a difference! Thanks
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OmahaRed
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PostPosted: Thu Sep 18 14 11:28 am    Post subject: Reply with quote

I'm planning for Three 2" ball valves for intakes for this smoker. Will this be sufficient? The cooking chamber is 60x40x30 and the firebox is 60x30x15.
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reeceb73
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PostPosted: Sat Sep 20 14 1:31 am    Post subject: Reply with quote

http://www.thesmokering.com/forum/viewtopic.php?t=60041&highlight=

Here is the one I built. I would do a few things different but it works great!
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SoEzzy
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PostPosted: Sat Sep 20 14 2:37 am    Post subject: Reply with quote

reeceb73 wrote:
http://www.thesmokering.com/forum/viewtopic.php?t=60041&highlight=

Here is the one I built. I would do a few things different but it works great!


Would you please expand on what you would do differently, (other than lighten the metal load), either on your original thread or on a new one?
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reeceb73
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PostPosted: Sat Sep 20 14 8:46 am    Post subject: Reply with quote

SoEzzy I posted the changes I would have made on my original thread.

For anyone interested, I used these plans as a loose guide on how to build a cabinet smoker. I just stretched and modified on the fly as I went.

https://www.dropbox.com/s/yn1y0qh74at6nqn/BBQ%20Grill.pdf
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Painless
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PostPosted: Tue Sep 23 14 6:55 pm    Post subject: Reply with quote

Thanks for the info. I have read and re-read it all.

I am learning Solid Works so have started putting my ideas into a design. I'm going to go about 3' wide by 2' deep and 5' tall.
Looking at using 1/2" thick for the fire box inside and 1/4" for the cook chamber. 2" of rock wool between. 1/2" baffle plate between FB and CC, with a 1/4" perforated baffle running up the back of the CC. Exhaust will be running up the middle between left and right shelves. 2 doors for CC - left and right.
One large door for FB with Stoker kit to control/log temp. 1/8 for exterior walls. (sorry bout the sizing I use metric so it would be 10mm, 6mm, 3mm plate steel).

Thanks for everyone discussion on this topic and thanks for the thread OmahaRed.
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OmahaRed
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PostPosted: Sat Oct 11 14 8:51 pm    Post subject: Reply with quote

I appreciate you guys keeping the thread alive. Back to the main topic, Does it look like I'm going to be able to get proper flow with the measurements I've listed?

Also, how does rockwool compare to spun ceramic blanket?

thanks again

Red
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Smokin Mike
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PostPosted: Sat Oct 11 14 11:02 pm    Post subject: Reply with quote

Insulation: McMaster Carr lists the mineral wool with a k-factor of .23. The rigid ceramic is .28. You should go to the site to check on the specific media that you're interested in.

http://www.mcmaster.com/#high-temperature-insulation/=u3tcrd

The mineral wool has a much better R value.

McMaster Carr wrote:
R-value measures the material's capacity to slow heat flow; the higher the R-value, the better the material insulates

K-factor measures the heat flow rate from one side of the insulation to the other; the lower the K-factor, the better the material insulates.

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OmahaRed
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PostPosted: Sat Oct 11 14 11:18 pm    Post subject: Reply with quote

I hadnt considered rigid ceramic. I figured spun ceramic blankets was the standard. But, if rockwool is better, I can definitely see using it. found some ROXUL for a decent price. does anyone have any experience with this?

http://www.lowes.com/pd_305816-1278-RXSS31525_0__?productId=3394032&cm_mmc=SCE_PLA-_-LumberAndBuildingMaterials-_-Insulation-_-3394032&CAWELAID=1205801014&kpid=3394032&CAGPSPN=pla&k_clickID=7f4043c0-a451-4178-9677-c7f0c22d061f&kpid=3394032
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OmahaRed
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PostPosted: Tue Nov 25 14 5:00 am    Post subject: Reply with quote

Is fiberglass insulation completely wrong?
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