dome construction HELP

[irishlad]

Ok I need help on this. Ive gone through all of the sites construction process but nowhere did I find the thickness of the shims that are needed to form the dome Im building a 42 inch oven but to create the dome I need to know the thickness of the shims to form it, any advice would be greatly appreciated
Thanks

[dmun]

Re: dome construction HELP

The thickness of your shims depends on the width of your brick, as well as the diameter. Rather than going mad with math or cad, the best way is to draw the interior ark you want on a piece of plywood, or chalk it on your base. Laying the bricks around the arch will show you exactly the width of shim you want for your particular application.

[irishlad]

Re: dome construction HELP

Great stuff I never thought of that way to determine the shims
as a carpenter by trade and a halfast brick layer that never ocurred in my thinking process
Thanks

[boccu]

Re: dome construction HELP

hi there irish - by no means do i consider myself as an authority on oven building - but I am just building my own now and have reached the sixth ring so I can at least share my own experience. I got all the way up to ring six without using any shims and with only one vane as a form. I determined the angle for each brick by laying it against the vane. The mortar i used (3:1:1:1 sand/portland/lime/clay) worked extremely well to keep the brick in place and to the thickness that I set it without the need for any shims at all. As Dmun said this angle will not only depend on the thickness of your particular bricks, but will also vary according to how accurately you lay the lower bricks. As i said i have just reached the sixth ring and lost my nerve so I have now put in a sand form to continue to the top. I was VERY pleasantly surprised to find my oven still perfectly level at the top of the 6th ring, so somehow not having any shims has done the trick well enough for me!! I'll be off for a ten days holiday and then will finish off the oven later.

Happy building!
cheers!
John

[jahysea]

Re: dome construction HELP

Irish, I agree with John's comments, as I relied more on vanes for correct angle than support. 1 or 2 vanes sounds great in retrospect. I used shims sometimes, but more for ease than necessity. I only made 2 shims.

If you do use shims.. Cut them long so that they stick way out and draw a line or make a notch to tell you how far to insert them. I made mine from scrap plywood cut into long thin triangles.

[maver]

Re: dome construction HELP

and just to add to the shim experience - I made my oven with different shims for each ring and used no vanes or forms. As a new bricklayer, I was surprised how level the final product was. My shims were the length of a full firebrick with the width of the shim based on the gap between each of two full firebricks used to lay out the arc. This gave enough of a handle as mentioned in the previous post. I don't think the line is needed (and could even be misleading if the half bricks are not cut with precision). Just line the narrow tip of the shim up with the top of the lower brick.

[Eddie4]

Re: dome construction HELP

Boccu,
I've been to Palmy North, beautiful place.
Do you know a Rachael and Al Lowery? They live on a farm there on the edge of town.
Eddie