Author Topic: Constructing WFO - why is garden hose used in this design?  (Read 500 times)

0 Members and 1 Guest are viewing this topic.

Offline dylandylan

  • Supporting Member
  • *
  • Posts: 374
  • Location: Dunedin, New Zealand
Constructing WFO - why is garden hose used in this design?
« on: October 15, 2013, 04:08:30 PM »
Hi all, down here in New Zealand there has been a recent magazine article on WFO construction.  Really the article is an "advertorial" but that's beside the point.  Several friends know me as being pizza-obessed and have pointed me to the article.   You can see the article from about page 70 in this PDF:
http://www.resene.co.nz/homeown/habitat/pdf/Habitat_19.pdf  (it's just over 14mb)

My question is: what is the purpose of the pieces of garden hose used in the arch?

I initially supposed they might be temporary spacers, but I see they've used brick wedges as spacers too.  Any ideas?   I'd love to know.


Offline TXCraig1

  • Registered User
  • Posts: 10620
  • Location: Houston, TX
Re: Constructing WFO - why is garden hose used in this design?
« Reply #1 on: October 15, 2013, 04:37:07 PM »
They also redesigned the inner arch from the first to second pictures.
I love pigs. They convert vegetables into bacon.

Online stonecutter

  • Registered User
  • Posts: 273
  • Location: SC
    • Old World Stone & Garden
Re: Constructing WFO - why is garden hose used in this design?
« Reply #2 on: October 15, 2013, 07:41:46 PM »
Looks like they used the hose sections to establish the space off the back of the firebrick.
http://oldworldstoneandgarden.com/

Look at a stone cutter hammering away at his rock, perhaps a hundred times without as much as a crack showing in it. Yet at the hundred-and-first blow it will split in two, and I know it was not the last blow that did it, but all that had gone before.
Jacob August Riis

Offline wotavidone

  • Registered User
  • Posts: 31
  • Location: South Australia
Re: Constructing WFO - why is garden hose used in this design?
« Reply #3 on: October 22, 2013, 03:55:44 AM »
I have a theory about spacers. I haven't bothered to post it before, because I expect that as soon as I do I will see a flurry of protest that I don't know what I'm talking about, "my oven hasn't cracked, you're an idiot, etc."
However, here it is, in all its glory: I believe brick spacers increase the risk of cracks. This comment is based on personal experience.
Think about it. A lot of people mix a little clay in their mortar. About 1/6 of the mix if you use a very common homebrew much discussed on the internet.
Clay shrinks. Mortar made with clay also shrinks a little. Two bricks wedged apart by a little piece of brick can't move towards each other as the mortar shrinks. So, there is a sort of internal stress created in the joint, increasing the risk of cracking.
I reckon if you use spacers, pull them out when the mortar has set but is still wet. Just sayin'......... :P
« Last Edit: October 22, 2013, 03:58:00 AM by wotavidone »

Offline Tscarborough

  • Lifetime Member
  • Global Moderator
  • *
  • Posts: 3062
  • Location: Austin, TX
    • Pizza Anarchy
Re: Constructing WFO - why is garden hose used in this design?
« Reply #4 on: October 22, 2013, 08:28:53 AM »
Portland mortar shrinks and lime mortar shrinks so a combination including fire clay will also certainly shrink. There is also something to the idea of a wedged joint causing cracking, this is why there are specified maximum aggregate sizes in proportion to the size of the joint.

This is also an issue (aggregate size) with a typical oven.  Refractory applications normally specify a joint of 1/8" or less, so a premix refractory cement will have the aggregate sized on that basis.  You will often see recommended "fine silica sand" for home brew, but it is not really suitable for the typical joints in a round oven.  Ideally, you would use the fine silica sand ("sugar sand" or "filter sand" are common designations) on the face mortar, and one with a typical sieve per ASTM C-144 (mortar sand) for the mortar on the backside of the brick.

This can be done by laying the brick with the fine sand mortar and using wedges, then pulling the wedges and filling in with mortar using the larger aggregate on the backside.

Just my thoughts.

Offline dineomite

  • Registered User
  • Posts: 125
  • Location: Cleveland, OH
Re: Constructing WFO - why is garden hose used in this design?
« Reply #5 on: October 22, 2013, 01:00:33 PM »
Those are some monster sized joints (both end and bed). I'm assuming because it's a kit (finite number of brinck), that explains the reasoning behind not keystoning the sides of the brick.


 

pizzapan