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CtTradArcher 05-22-2013 11:35 AM

Offset Build Question
 
1 Attachment(s)
Hi All,

New member here, although I have been lurking in the shadows for quite some time enjoying the site and soaking up information from those in the know.

I am starting on an offset build and have a question that may spark some debate, but here goes anyway...

Looking for input on firebox to cooking chamber placement and stack placement. I have read and re-read several awesome builds on here and two in particular that impressed me, however they have different approaches.

One was along the Jambo approach and the other more like a Gator or Klose approach. Meaning firebox opening above or below the cooking grate. Stack opening pretty much appears to be the same, at grate level.

I am guessing the answer is partly preference, but it would seem that there should also be an aspect of fact on which produces a more even cooking environment.

Does pit size matter when deciding? Does one work better than the other on larger or smaller pits? And does an insulated firebox make a difference relative to approach? I know insulated is better overall, but does it contribute to the success of one design over the other?

After much effort, I was able to score a compressor tank, which I trailered home yesterday. It is 20" in diameter and 60" long. I don't believe I will have many opportunities to get another as reasonable as I got this one, so I want to try my best to get it right the first time...

Any input is much appreciated!

Regards,
Peter

buttburnersbbq 05-22-2013 05:30 PM

Scrape the offset and build a reverse flow. Once you have a RF you will not cook with anything else. There are pit calculators on line you can find to size your firebox, stack and opening fro firebox to pit.

dwfisk 05-22-2013 06:53 PM

Quote:

Originally Posted by buttburnersbbq (Post 2490152)
Scrape the offset and build a reverse flow. Once you have a RF you will not cook with anything else. There are pit calculators on line you can find to size your firebox, stack and opening fro firebox to pit.

^^^^^Agree. You will be very happy with RF performance and ease of cooking. If you go RF, by definition the firebox opening is well below the cooking grate and you count on the RF baffle to contribute radiant (very balanced) heat. I'm just guessing, but at 20" diameter and doing RF you will probably wind up with a single cooking grate (i.e., RF baffle about 6" above the bottom, cooking grate at center line or 6" above the RF baffle and about 6"-7" top clearance (maximize this!); add in the thickness of the baffle and cooking grate structure and you are pretty close to 20" ID). I would be tempted to extend the exhaust stack into the cook chamber about 1/2 way from the top to the coooking grate. Just my $0.02. Good luck and welcome to the forum.

NRA4Life 05-23-2013 05:59 AM

Can't go wrong with a reverse flow. This is my last build.

http://i929.photobucket.com/albums/a...psba14a187.jpg

CtTradArcher 05-23-2013 07:35 AM

Thanks for the replies! Seems reverse flow is pretty popular. I had considered RF, but figured less material, cost, and weight with a standard offset. Plus I have heard RF's can be fuel hogs, but I admittedly do not have personal experience.

Is it necessary to weld in the RF plate or can it just be set in so it can be removed for cleaning the pit?

NRA4Life 05-23-2013 07:55 AM

Both of mine are welded in. Never had a need to get below the RF baffle to do any cleaning, but I suppose you wouldn't have to weld it in if you were able to get a good seal all the way around.

dwfisk 05-23-2013 07:59 AM

Just some input.

RF or traditionsl offset: I built mine to do either with exhaust stacks on each end of the pit. My RF baffle is actually a series of 1/4" thick, 6"x17-1/2" plates that rest on 3/4" angle welded to the inside of the cook chamber (you can barely make them out in the pictures below). In the RF setup, I put the individual plates against each other to make a solid baffle. I have found cutting the individual plates on a shop shear gives you a good clean edge, they stack together tightly and seal up real good. In the traditional setup, I just space them out a little and use them as tuning plates. In reality, I almost always cook in RF mode and I'll probably renovate the pit this summer to just be RF.
Just a reference picture of my rig, note the 2 exhaust stacks.
http://i1311.photobucket.com/albums/...ps6ce9c2d4.jpg
Here is a picture with the plates pushed together in RF mode.
http://i1311.photobucket.com/albums/...ps22e301ec.jpg
Here is a picture with the plates staggered across the pit in more of a traditional offset mode.
http://i1311.photobucket.com/albums/...psb438d255.jpg
Fuel: I use kiln dried hickory splits (think of a 6"-8" chunk of tree, quartered) 16"-18" long. I'll use some kindlng and about 4-6 splits to get a good coal bed then ad 1-2 splits every hour or two depending of my target cook temp, weather, how full the pit is and a bunch of other variables. I don't think I use any less in a traditional offset mode cook, maybe more.

Just my $0.02. I'm gonna steam clean the pit this weekend, I can get you some more pics if that would help.

No matter what you decide, have fun, it will be a great experience and the Q will be great!

CtTradArcher 05-23-2013 09:50 AM

Those are some really nice builds!

Kevin, Was that a compressor tank? It looks very similar to mine. Is it close in dimension to mine (20" dia / 60" long)? If so, what did you settle on for firebox size?

Dave, Seems you have the best of both worlds. Good thought being able to switch. And yet being able to do so, you are finding RF to be preferable. Is your diameter 24"? I notice you have an upper rack.

Qbert60 05-23-2013 10:28 AM

I modeled mine after a jambo, but I have a 6 sided pit. The thing with the Jambo's, you have to have the deflector place above the opening of the firebox to the pit. I have a grate in the middle of the pit and above that grate, it can get around 400*. Great for chicken, sauces, glazing, and over all grilling without the direct heat. The main grate is even from 275*-300* adding a single split ever 1 to 1.5 hours. Insulated firebox as well.

dwfisk 05-23-2013 11:29 AM

Yep, 24"X72". Its a 1/4" wall propane tank. Door width is 54" as are the cooking grates; bottom grate is 23-1/2 deep, top grate is 18" deep. Grate spacing is a little bit of a trade-off, probably more so if you squeeze 2 into a 20" diameter. My top grate only has 4-1/2 inches of top clearance to the edge of the door opening, plenty for ribs, split chicken and medium briskets, not enough for butts, big briskets or whole chickents/turkeys, they go on the bottom grate and for really big stuff (whole hog) I just remove the top grate.
Yep, I find RF gives a very consistent temp range across the cook chamber, very consistent cooking and smoke and very predictable fire, fuel usage and cook times. But then, I've done a bunch of cooking on it. I suspect whatever you build, if you spend enough time getting to know it you will figure it out and get some great results.
QUOTE=CtTradArcher;2490954]Dave, Seems you have the best of both worlds. Good thought being able to switch. And yet being able to do so, you are finding RF to be preferable. Is your diameter 24"? I notice you have an upper rack.[/QUOTE]

CtTradArcher 05-23-2013 02:28 PM

I hope so. I have several grills/smokers now. Most I have figured out, like my UDS and my CG Akorn. But I have not had much luck with an old NB offset that I picked up and refurbished. Temps all over the place when trying to go it on wood alone.

I have been told that an offset (or RF) like a Lang, Klose, Gator, Jambo, etc are much more consistent. Really can't afford one of those at the moment. I am hoping to build one for not much more than what it would have cost me just for the shipping ($600 to Ct).

I bought a Hobart Handler 140 and a metal cutting skill saw. Along with other tools I already had, I think I have what I need. And at the end, I will have some pretty cool new tools too. Which I can use for my next build...

buttburnersbbq 05-24-2013 03:37 PM

Quote:

Originally Posted by CtTradArcher (Post 2490745)
Thanks for the replies! Seems reverse flow is pretty popular. I had considered RF, but figured less material, cost, and weight with a standard offset. Plus I have heard RF's can be fuel hogs, but I admittedly do not have personal experience.

Is it necessary to weld in the RF plate or can it just be set in so it can be removed for cleaning the pit?

My reverse flow I built out of a 250 gallon propane tank only needs one split per hour. I think that is pretty efficient.

NRA4Life 05-24-2013 03:58 PM

Quote:

Originally Posted by CtTradArcher (Post 2490954)
Those are some really nice builds!

Kevin, Was that a compressor tank? It looks very similar to mine. Is it close in dimension to mine (20" dia / 60" long)? If so, what did you settle on for firebox size?.

Yes, it was a vertical compressor tank. It was 24" dia./66" long. The firebox is oversize at 24x24x24. You could probably do 18" cube or 20" cube.


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