Barrel meets cob questions

Dear fellow Rocket Scientists,

so far I've build all my rockets with a cut barrel manifold. So when the manifold barrel and the top barrel meet, there's a lip that I can put some gasket on and when I need or want to I can lift the top barrel off.

I have two questions:

1) Using a brick manifold, what does the barrel seal against? I've read wet cob that you imprint the barrel lip into and then put a gasket there?

2) If I partially cob around the barrel, for example to limit radiation towards an outside wall, how do I inspect the top of the riser? Do I then have to use a barrel that the top  can be lifted off? If so, how do you prepare the barrel in order to do that? How do I get a good seal? Wouldn't a lid that's not held in place tightly warp a lot?

Thanks in advance

Some barrels are solid, and some have a removable lid. You need one of the removable type to start with. These have an adjustable steel cupped band that holds the lid tight. There would be a watertight seal that would most likely need to be replaced with a noncombustible airtight seal.

Hey Glenn, thanks for the answer. I once bought two of those. But the lids still had the 2 openings that the oil drums have, so I didn't end up using them and decided against them for future projects.

Hey Ben;
As Glenn said, you would want a removable top barrel.
They usually have a plastic seal under the lid that you want to remove.
I have found that, with rocket use, you do not need to reseal the lid; it is cupped, and the band tightens it enough that I have never had a leak.
For setting the barrel on a masonry base. You can put cob down and seat the barrel on it, or I prefer to use a Superwool gasket apx 1/2" thick.
Tear the 1" in half; create a barrel-shaped gasket. Set the barrel in place and seal around the bottom with cob.

If you can not locate a removable top barrel, you can use a traditional full barrel.
If you have brought cob up on one side to protect the wall but not gone completely around the barrel (Other than the very bottom), your cob will form to the barrel, but your barrel can be broken free and lifted off. The short wall of cob on the back side should stay in place.

On my J-Tube builds if I used a Superwool riser or a brick riser, I never needed to get in and inspect the riser.
The area that needs inspection is the transition area and the pipes through the mass (If you used them).

I can show you how I make a barrel to cement seal…..