This is our second pass through Year 1 and tomorrow we are going to measure the ark again as it was one of the projects we really remember. The size of the ark is not something you get until you see it.
I thought I'd pass on what we are going to do since it is different than what Tapestry suggests. To be honest, maybe too much so, I'm glad I did not try to do what Tapestry suggest and have each child have a cubit piece of string and count up to 300 with those. This might work with a large co-op where each child had to only measure several times, but both times our group has been under 10 children. I think having to keep track of up to 30+ measures for each child would be very difficult (although I do think it would certainly add perspective since Noah took 100 years to build the ark ).
Instead I went to the hardware store and got a roll of twine. For around $3 to $5 you should be able to get a roll of 500 feet. Measure off 50 feet and you've got the length of one side left on the roll (450 feet). Add a pencil to use as the roll out device and you are set to measure. The short side is 75 feet so you can use that remaining piece to measure 1 1/2 times to get that measurement. Then chop off five feet, add a helium balloon and you have the height of 45 feet. Put a bucket or trash can or one of those sports orange cones at each corner and you can see those. (We are going to use these utility posts because we own them and I bought extra string so we can have a balloon at each corner and one in the middle).
Be prepared to talk with strangers and everyone wants to know what you are doing.