Keystone Size

[K79]

Is it ok to have a final keystone that is about 1/2" at the base and 3/4" at the top. Do you need mortar for a keystone of that size?

[brickie in oz]

Re: Keystone Size

Is it ok to have a final keystone that is about 1/2" at the base and 3/4" at the top. Do you need mortar for a keystone of that size?

It will crack, adjust you arch to work bricks either with slightly larger joints or a flatter arch.
You should work it out prior to laying the arch.

[K79]

Re: Keystone Size

What should be the minimum area of the small side of my keystone? Any pointers as to what I should do? What would the ideal keystone be?

[K79]

Re: Keystone Size

I have a design now where my keysotone will be as round as I can make it. The top of my keystone would have a radius of 2.5" and the bottom 2.18". Do these dimensions look sound?

[brickie in oz]

Re: Keystone Size

Sounds fine to me, you won't really know until you get there.
The only thing I would say is make sure it is not to tight a fit you wan't it to be a snug fit.

I think they are talking about the front arch, not the top of dame.

[brickie in oz]

Re: Keystone Size

Ok my bad, I saw a graphic of an arch with a whopping great gap at the top so I assumed it was for the arch.
Here.
http://www.fornobravo.com/forum/f8/m...tml#post146703

[brickie in oz]

Re: Keystone Size

I was using my bestest Inspector Clouseau accent.......

[K79]

Re: Keystone Size

Ok, my keystone changed (on my plans) due to the change in brick dimensions. Does this look ok overall? My firebrick is 9x4 7/16x2 5/16.

[deejayoh]

Re: Keystone Size

As an aspiration, that looks great. But just be prepared to make adjustments along the way! Your oven is not going to come out precisely as you draw it. My keystone turned out pretty small (relative to many), but I really only started to plan it when I got to the last three courses.



My $0.02 is that you might want to plan for the plug to be a little bigger than what you have now, because your mortar joints are more likely to be too big than too small, eating up any wiggle room you have.

[K79]

Re: Keystone Size

If your keystone is multiple pieces should you put them together dry and slide them in place with no mortar? Same goes for one piece if you can. Should you slide that in without mortar too?

[ATK406]

Re: Keystone Size

No harm in using mortar to seal it up and lock everything in place. The rest of the construction uses mortar, no reason to stop on the last piece.

[deejayoh]

Re: Keystone Size

Yeah, you want to use mortar on the keystone just like the rest of the dome. That's what holds the bricks apart to give your dome structural integrity. Plus, it keeps the smoke and heat inside, which is kinda nice

[K79]

Re: Keystone Size

Ok guys running into sort of a dilema designing my vent. Since my oven is 40" dia. I need an 8" dia. steel chimney. Well I'ld like to make mine out of clay flue liner which is 8"x 12". I was told that the 8"x12" has the same draw as an 8" dia. steel chimney. Others I believe have taken the 8x12's and cut them to be 8x8??? Is that enough size for correct draw?

[Tscarborough]

Re: Keystone Size

Square/rectangular flues are measured o.d., while round ones are measured i.d., FYI.

8x8 is a common size for clay flue liners, with 30.58 SqIn of draw: 6.25 (i.d.)/2 gives a radius of 3.12, 3.1416x(3.12x3.12)=30.58. When calculating draw you draw the largest circle(s) that will fit in the area and use that dimension. The area of the flue should be around 15% of the size of the inner opening, and more is better up to a limit.

(the floor size doesn't really matter for draw)

[K79]

Re: Keystone Size

Square/rectangular flues are measured o.d., while round ones are measured i.d., FYI.

8x8 is a common size for clay flue liners, with 30.58 SqIn of draw: 6.25 (i.d.)/2 gives a radius of 3.12, 3.1416x(3.12x3.12)=30.58. When calculating draw you draw the largest circle(s) that will fit in the area and use that dimension. The area of the flue should be around 15% of the size of the inner opening, and more is better up to a limit.

(the floor size doesn't really matter for draw)

Ok, so an 8x8 clay flue liner will work. So I need to reach at least 30.58 SqIn for my vent opening as well? A little confusing when most try and reach somewhere between 40 and 50 sq in.