(This is the third of four posts detailing the mods that I have made to my CharGriller Smoker Pro.)
This mod insulates both the cooking chamber and the SFB using welding blanket material. Almost every square inch of the smoker is covered. For the SFB, 700F RTV gasket material is used to affix the blanket material and (because I don't trust the gasket material to act as a strong adhesive) #6 self drilling screws with washers secure the larger pieces. For the cooker, 500F RTV is used.
The welding blanket material came from 3 3'x3' Tillman O-PAN black felt blankets. I purchased them here: http://store.cyberweld.com/panfelwelbla.html because the were not available locally (and if ordered at a higher price). Cyberweld offers free shipping and a broad range of welding products. I have no affiliation with them.
I initially assumed that I would only insulate the cooker. During test burns it became obvious that I was losing much more heat from the SFB than the cooker itself.
The Tillman O-PAN black felt blankets are soft and smooth even after exposure to high temperatures. The working temperature is 1800F (max 3000F).
The result is attractive (IMHO) and effective.
This insulation process increased my test burn time by about 6 hours -- from 5.5 hours to more than 11 hours.
The Grill Fully Upholstered
The silvery points are the heads of the self drilling screws and washers.
One 3x3 blanket each was used for the SFB, the upper half and the lower half (3 3x3 blankets in total).
The process I followed was to locate a straight edge of the material and RTV it along an edge of the cooker or SFB. Then I followed that same edge with the screws to insure a solid mechanical bond.
I then folded the material back from the material it would cover and laid down a pattern of RTV in the large area exposed, and finally at the opposite edge.
Then I laid the material carefully on the fresh RTV and smoothed it from the secured edge to the new edge with a rounded object (one side of a 16' tape measure in my case). Once smooth from side to side I allowed the RTV to set for a few minutes and screwed down the new edge.
Finally, cut out any holes that should penetrate the insulation (chimney, bolt holes, thermometer holes, etc). An Exacto knife is just the thing.
At this point I trimmed around the edge with kitchen shears (it cuts easily). Then I screwed down any other edges.
Note: The bottom half of the barrel has the grease drain port. I cut a circle around both openings and removed the blanket there. Then, I built up a barrier of RTV at the edge of the insulation, forming a raised ring (from which the grease will drip.)
This is intended to prevent the grease from soaking into the insulation around the edge and creating a fire hazard as well as a nasty cleaning problem.
I repeated this process with each part (ends of the cooking chamber and the SFB), fitting scraps where required.
Where two edges meet at a corner, I came around at the end and squirted a bead of RTV between them and pinched them together to close the corners.
I performed the insulation in three stages (one blanket each). First I removed the SFB and insulated it. Then I removed the bottom and insulated it.
Since I had neglected to purchase a third blanket (assuming I would only do the upper and lower halves) I reassembled it at this point and did a test burn. The results were encouraging enough that I ordered the third blanket.
When it arrived, I insulated the top in-place on the cooker. If I had had all three blankets to start with, I would have done it disassembled, as with the other parts.
On the SFB, I insulated all the parts externally exposed, including the door and the ash box. You can see the copper colored 700F RTV better in the picture than in real life (for which I am grateful).
The SFB surface can exceed 700F, so one cannot depend too much on the RTV.
One side benefit of this process is that the danger of burns, especially to children are much reduced. There are still hot spots that would hurt, but there are no large areas that could cause catastrophic burns. Holding your hand on the insulated surface of the SFB is unpleasant, like a three second fire test.
Care must be taken, both on the SFB and the lower half of the cooker to keep the mating area between them clear of the insulating material. The outline is pretty clear, but I found a little extra trimming necessary when putting it back together.
Detail Right Side Upper Half
Edited to add note about grease drain handling.