Rocket BBQ

[mannytheseacow]

Oops, yeah, sorry about that. If you find the area where you dig your soil from, click on the "AOI" button and draw a box around the general area you dig from. Then click on the "Soil Map" tab and it will show you "Map Unit Symbol" and "Map Unit Name".

This is an easy way to understand your soil information without getting too personal about your location. I think it's an awesome source of information but forget that I'm kind of a nerd and most people don't use this stuff as often as I do. No problem if you don't want to deal with it.

Anybody out there using earth as a core material, I'd be stoked to find out what soil types you are using, whether good or bad results.

[hpmer]

Here it is, though I'm not sure how accurate it is. "H2 - 5 to 21 inches: gravelly fine sandy loam" - Not hardly. That's the zone that holds my clay mine (cleverly disguised as a 36"w x 24"l x 24"d hole in the ground). It seems to me to be a pretty clean section of straight clay, though I'm hardly a soil expert and I don't understand most of what is listed. And, after a good rain, water will stay pooled in the mine for days.

Setting

Parent material: Till
Typical profile

H1 - 0 to 5 inches: gravelly fine sandy loam
H2 - 5 to 21 inches: gravelly fine sandy loam
H3 - 21 to 60 inches: loamy sand
Properties and qualities

Slope: 3 to 8 percent
Depth to restrictive feature: More than 80 inches
Natural drainage class: Well drained
Runoff class: Low
Capacity of the most limiting layer to transmit water (Ksat): High (2.00 to 6.00 in/hr)
Depth to water table: More than 80 inches
Frequency of flooding: None
Frequency of ponding: None
Available water storage in profile: Low (about 5.3 inches)
Interpretive groups

Land capability classification (irrigated): None specified
Land capability classification (nonirrigated): 2e
Hydrologic Soil Group: A
Minor Components

Udorthents

Percent of map unit: 5 percent
Walpole

Percent of map unit: 4 percent
Landform: Depressions
Scituate and newfields

Percent of map unit: 4 percent
Chatfield

Percent of map unit: 4 percent
Squamscott and scitico

Percent of map unit: 4 percent
Landform: Marine terraces
Boxford and eldridge

Percent of map unit: 4 percent

[mannytheseacow]

Oh well, it was worth a shot. The soil survey is a great resource but it sounds like you're accessing an isolated clay pocket, which is common in those gravely creek soils. Thanks for your effort.

[hpmer]

Firebox properly cobbed in. Trowel shown for reference. Oven is now gone, so I'll probably reuse the cob mix from that area.

[hpmer]

Manny,

Was it you that helped solve your fire creep / smoke back issue by building up the feed tube? If so, I'd be interested in hearing more about that. I'd have thought that increasing the height of the feed tube would reduce the ratio of that to the heat riser and have a dampening affect, but maybe there is something else going on.

My feed tube is 6" square and 9" deep, so the front edge is 3" of material forming the ceiling of the burn tunnel. The thing works ok, but doesn't suck all of the smoke down into the burn tunnel like I'd like so I was wondering about your mods. High high, how wide, etc. Matt suggested adding a collar around the feed tube so I'm willing to try that, but before I do I thought I'd ask about your experience.

[mannytheseacow]

Hi Hpmer,

Yes, increasing the feed height helped me a lot. I think there was a couple of things that changed about that same time that really helped the situation out too.

First, yes, I would recommend building the feed up. If your fuel is consistently cut to about the same length, try building the feed up to near that height. I know it throws the ratios off but I don't think the ratio is really that important, especially with a short running flue path. This is just my opinion, but I thing constricting the air flow around the fuel gets the air drawing faster down around the fuel, achieving what you are after.

A couple other comments, though...

These outdoor cookers are slightly more challenging in my opinion. I have my old maple syrup/barrel burner, which is kind of a joke, and then these natural cores that I've been playing with using your core mixture (ash/soil) for this community development project I've been working on. These are more of an Approvecho style open top/recessed cooker but with a J-shaped core. I've been building the feed up on these, too, which seems to help. For outdoor stoves, though, you really don't have that high temperature differential like you would with an indoor rocket (warmer air inside/cooler air outside) that really helps them draw without even having a fire going.

Then you also have to consider that you don't burn outdoor stoves nearly as often, so they take much longer to dry out, and you are usually firing it cold.

Building up the feed on my indoor J really helped, but around that same time the temps outsided started dropping considerably, and I think the core and mass were also starting to really dry out and function properly. So I believe all these factors came into play. Though, like I said, building the feed up to the level of your fuel height helps, in my limited experience.

[hpmer]

Thanks, Manny.

I think your observations on the challenges of outdoor stoves are spot on. I'll try building up the feed and see if it makes any difference. I'm running out of things to try as I've worked through most of the possible issues I listed earlier on in the thread. The bbq still maxes out around 350*, though the stove burns clean and is very usable as is.

You and I will have to compare notes once we get to maple syruping season. I have a pretty small operation but it sure is nice to get outside on a bright spring day and enjoy the fresh air. I'm going to (hopefully) build another stove to use as a pre-warmer for the cold sap and plan to document the build. On weekends I'm burning shredded paper for the ash as I find it makes a lot more of the stuff than does wood.

[mannytheseacow]

[hpmer]

I have not, in fact I've never even heard of that one before. I know that people in Alaska use birch since sugar maple doesn't grow up there. Sugar maple is supposed to have the highest percentage of sugar in the sap, which means less boiling time and better taste. I've also used red maple (aka swamp maple) and there are a few others that work as well.

I thought black walnut was prized for its furniture quality wood? If so, I sure wouldn't want to wreck a nice trunk with a bunch of holes. They'll fill in as the tree grows, but will leave evidence behind kind of like what a knot will.

I'll plan on documenting the whole process this year and post it to a thread under one of the other sections. It's pretty straightforward. Kind of like the inverse of moonshine. The difference is we want what's left over after the boilin' is done, where the shiners want what boils off. I actually had a passerby ask me once if I was making moonshine. Maybe I should try that next.

[mannytheseacow]

I'm looking forward to see your run down on syrup making. My method is pretty ghetto. I use plastic hose-barb fittings and tie an old milk-jug around the tree to catch what runs out. It works; low investment, probably low-results. Definitely a lot of boiling involved.

I've been planting sugar maples every year for a few years but only have a couple mature enough to tap. I usually tap silver maples and boxelders, very low in sugar, but it works.

Yes, black walnut is valuable wood. But, it grows like a weed and I've already got stacks of it sawn and stickered. After a while I just get sick of it. Not to mention, a lot of the timber where I tap trees is so steep that getting logs out isn't really feasible. I forget where I read that about tapping the walnuts for syrup, though. It was a university of something or other document.