Gaging how much raw materials will be needed to build a cob dragon head.

Hi. Newbie here. I own a  home child care and have a very ambition project coming up. We are building a cob dragon head and tail that will flank four half burried tires ( the body) for the students to play on. I have sooooo many unanswered questions !!
1) materials list : I’m guesstimating a head roughly 5x5x5 (feet) , and a tail 1.5x3x.5.
2) solid cob vs gabion center
3) calculating man hours
Any and all suggestions, directions pointed, clarifications etc are warmly welcomed and highly appreciated!!!  I’m just a grandma that loves kids and has big dreams to show our community how fantastic eco ideas are and help open dialogues to encourage others to be brave and creative!!! We are getting a work party of several families that have come through my child care program. None of us have experience, but we are all ready to roll up our sleeves to get it done. I’ve been looking up some tutorials. They deal in material percentage, but not volume calculations and I will soon be ordering supplies.
Thank you!!!

Personally I would avoid the tires because of their potential toxic component.

Hi Marla; Welcome to Permies!
A question to start)  Is this under a roof ? If your answer is Yes then your golden.
If the answer is no, then did you have a plan for weather proofing ?  
Cob and rain do not play well.

Now on to your questions.
#1) My clay was very pure , so I needed 3 times as much sand as I did clay. I'm thinking a pickup load of clay to a small dump truck load of sand.
#2) Gabion center for sure.
#3) Oh my , cob has to dry as you go. So more partial days will be needed than you think.  Making cob can be hard physical labor, folks will get tired. Employ child labor for that part of the job.

I know I didn't give you the specific answers you were hoping for, but its a step in the right direction.

thomas rubino wrote:Hi Marla; Welcome to Permies!
A question to start)  Is this under a roof ? If your answer is Yes then your golden.
If the answer is no, then did you have a plan for weather proofing ?  
Cob and rain do not play well.

Now on to your questions.
#1) My clay was very pure , so I needed 3 times as much sand as I did clay. I'm thinking a pickup load of clay to a small dump truck load of sand.
#2) Gabion center for sure.
#3) Oh my , cob has to dry as you go. So more partial days will be needed than you think.  Making cob can be hard physical labor, folks will get tired. Employ child labor for that part of the job.

I know I didn't give you the specific answers you were hoping for, but its a step in the right direction.

Initially, we were just planning an awning type roof like you use for camping , while it cured. I wanted to do linseed oil finish once it had cured, to help it withstand some of the elements. A more permanent covering not out of the question.
How thick can one layer of cob be whilst still maintaining its integrity?

Excellent news on planning for a roof. I think you will want one after all your hard work to get your dragon sculpted .

I would say it depends the consistency of the cob and the application, location (horizontal/vertical ). Lets say 2-3" vertical and 6" + on the flat.
Be mentally prepared... cob will crack... more sand will help and using straw as a binder will help as well.

Cob can also be dyed with natural colors.  Red and black are found with the concrete products.  Other natural primary colors are avalable online.