MY NEW 42"OVEN BUILD.

[UtahBeehiver]

Calculate the area of a sphere (4 x Pi x radius squared) then use one half of the number PER layer will get you approximate square inches. Radius will be 21" plus wall thickness (most likely 4.5") of dome. You get to use your math skills. Need to factor in a little contingency for trimming.

[ivancito]

Happy thus far with my oven build progress, this project is very adictive. Its all í want to do all weekend is work on her. Also í need to learn how to use my cell phone camera as several pics are upside down.
Ivan

[ivancito]

Calculate the area of a sphere (4 x Pi x radius squared) then use one half of the number PER layer will get you approximate square inches. Radius will be 21" plus wall thickness (most likely 4.5") of dome. You get to use your math skills. Need to factor in a little contingency for trimming.

(4*3.141592654*25.5squared)=8171.28 divided by 2=4085.64 square " A roll is 1200square" 4085.64 divided by 1200= 3.4 rolls Russell does my math add up? thanks Ivan

[JRPizza]

Ivan, what are the dimensions of your rolls of insulation. A square foot is 144 square inches. A 1200 square inch roll a foot wide would only be 8.33 feet long, unless my math is messed up. A 50 foot long roll of 1 foot wide insulation would be 50 ft^2 which would be 7200 in^2. Did you mean 7200?

[UtahBeehiver]

Ivan, first part looks fine area of your oven surface, like JR says just need to know how wide the 50 foot rolls are to calc square inches. remember the area required is per layer.

[ivancito]

Ivan, what are the dimensions of your rolls of insulation. A square foot is 144 square inches. A 1200 square inch roll a foot wide would only be 8.33 feet long, unless my math is messed up. A 50 foot long roll of 1 foot wide insulation would be 50 ft^2 which would be 7200 in^2. Did you mean 7200?

Ok JR the rolls are 50feet by 2ft wide. Not sure where my math went wrong, I think I feel a stress crack in the back of my head, thanks Russell.
Will a single box give me the 3inch layer I need?

[RandyJ]

Ivan my guess is that it is a standard box witch is 2 feet wide by 25 feet long for a grand total of 50 square feet per box. It would be a really heavy box if it was 2 feet by 50 feet and hard to handle. On my 40" oven I used 3 boxes of ceramic blanket. If you are worried then go for 4 boxes but my guess is 3 would probably be enough if you are careful how you put it on.

Randy

[UtahBeehiver]

50 feet x 2 feet = 100 sq ft times 144 sq in per sq foot = 14400 sq inches your need is 4085 sq inches per layer x 3 so I let you figure the rest.............

[ivancito]

Awesome, thanks guys for chiming in and your valuable time and suggestions. I will pick up 2 boxes of 25ft rolls and make that work. I'm still a week away from needing it but wanted to be prepared.
thanks again.
Ivan

[UtahBeehiver]

Be sure to wear a Niosh 95 mask, eye protection, junk clothes or disposable coveralls. It is really nasty stuff to handle and cut. Kind of like fiberglass insulation but worst.

[RandyJ]

I second that. I wore my work clothes and eye protection and a respirator. After I was done I was very itchy, and I thought I was prepared. You can't be to safe with the stuff. It does cut nicely with a very sharp razor blade. Don't be afraid to change the blade if it starts to not cut well.

Randy

[ivancito]

Thanks Randy and Russell for the heads up, I will def get suited up for that operation. I will have to borrow the respirator from my job to be on the safe side. Does the blanket need to be precisely fitted to the dome where the strips overlap each other? Does it matter if I lay the strips onto the dome horizontally or vertically, probably both dumb questions just don't want to screw it up now.
thanks everyone.
ivan

[RandyJ]

As for how precise you need to be when putting on tge insulation it kind of depends on if you are doing a igloo or enclosure. There have been a few lately the got everything to fit nice and tight and round so the igloo was easier to make round. When I did mine I wrapped a layer around the base then 2 strip over the top for each layer. It was a little lumpy but it didn't matter as you would never see it. Also I am guessing that you will need 3 boxes of insulation to get your 3" layer. It will take most of a box per layer unless you are trying to fit everything very tightly. If you can easily get a extremely box at the last minute then don't worry about it. Just a thought from me. Keep up the good work.

Randy

[JRPizza]

I agree with Randy, my 39" oven took two boxes plus about 8 feet of a third box. Mine sits on 5" of insulating board and I brought the blanket all the way to the slab, so I might have been able to make due with 2 boxes but I think it would have been tight. Since I believe you are planning on an enclosure, I'd be tempted to buy 3 boxes, save enough blanket to build at least one insulated door (maybe enough to build two, and you are going to probably want at least 3" in the door), and pile all the extra on top of your dome. I would have put my remaining on my dome but since I built an igloo didn't want it to be lumpy, but for heat retention I might have been better off.

[Larry P]

If you don't mind me fixing up your math:
layer 1, r = 25.5"
layer 2, r = 26.5"
layer 3, r = 27.5"

Surface area of a hemisphere = 2πr²

area layer 1 = 4086in² = 28.4ft²
area layer 2 = 4412in² = 30.6ft²
area layer 3 = 4752in² = 33.0ft²

total = 92ft²

1 roll = 2ft x25ft = 50ft²

So, theoretically you need 1.84 rolls, with 7% waste. I'd be really surprised if you are able to do that, and I think your last layer would be almost all piecing together from scraps = total pita. I'd suggest 3 rolls. I used almost all of 2 rolls doing 2 layers on my 36" oven, but it's a low dome and I piled a lot or scraps on top to bring it to more of a hemispherical shape.

BTW nice looking build. Beautiful brickwork and I really like the flared entry. Something about the proportions of the whole thing, I find really balanced and aesthetically pleasing.