On Saturday, October 22, the weather was good. We were able to cause charring and smoldering in a 1-2 foot wide swath along much of the boat's length. After three passes over the boat, the hull was penetrated and a small open flame was achieved. This burning area was self-sustaining and, about 2 hours after the test had ended, it was still burning with intermittent flame and had created a roughly 10 inch diameter hole in the hull of the boat.

We did not, however, achieve a large flash ignition as we did in the MIT test. We believe that this was due to the high moisture content of the boat that was used as a target. In my view, it is an open question as to whether the boat was representative of a seaworthy Roman ship... but at least this boat should not be considered as too easy a target!

A more detailed description of what happened follows.

The test employed 300, 1 foot square, bronze mirror tiles (510 phosphor bronze alloy). The number of mirrors was determined using the first MIT test as a benchmark and accounting for the different mirror material, along with the different conditions in San Francisco.

The tiles were polished using Brasso by the MythBuster and MIT team. The polish was quite high on most mirrors. About 30% of the mirrors had a variety of flatness defects that would reduce their performance to some degree.

The tiles were aimed in a manner similar to the MIT test, with the exception that there were 4 tiers of mirrors instead of just two rows. The mirror array was about 110 feet long, similar to the MIT test. The goal was to make an array that was big enough to start a fire, but small enough to implement within reasonable budgetary and time constraints (my guesstimate is ~3-4 person weeks, mostly spent on polishing the bronze).

Our understanding was that the target boat was a 30 foot, 1924 wooden fishing boat. It was purchased from its prior owner after it had sunk and then been retrieved and brought back to port. We were told that it was much lower in the water before the engine and other heavy items were removed a few days before the test.

It is believed that the boat planks were made of douglas fir. The planking was estimated to be 2-3 inches thick, dependent upon location. The boat had been partially stripped of paint and then coated with pitch.

The test began at roughly 12:15 and the 300 bronze mirrors took 10 minutes to aim (14 people working in pairs) using an aiming process similar to the MIT experiment. The aiming mirror was initially pointed at the stern of the boat since the motion of the the earth around the sun caused the point projected by the fixed mirrors to move towards the bow of the boat over time.

Adam was an awesome mirror aiming machine.

Almost immediately after uncovering the mirrors, a considerable amount of smoke was visible. Black charring was visible on the side of the boat in a few minutes. The bright spot was estimated to be 4-5 feet in diameter... not as tightly focused as we had anticipated based on preliminary tests, but not terrible either.

As the sun spot moved along the side of the boat (at about 9 inches per minute), it created a roughly 1-2 foot wide charred band along the side of the boat, but without open flame. We believe that a significant amount of moisture was being boiled out of the wood.

At this point, we decided to bring the boat closer for one last attempt to achieve open flames. The rationale was that, at a shorter distance, we would be able to more tightly focus the beam. The boat was brought to a distance of 75 feet. The time was roughly 2:00 PM.

In hindsight, this was a poor decision on my behalf. It would have been better to use the time to just make another pass over the boat since, as became apparent later, the coals were on the verge of reaching an open flame (the glowing coals can be seen right under Jamie's feet in the picture at left, which was taken while the boat was being repositioned).

Regardless, we brought the boat to a distance of 75 feet and began the aiming process once again, starting from the stern using the silver mirrors. However, while the beam was still near the stern, a modest open flame broke out mostly on the inside of the hull at midship, near a scupper hole. The sea breeze was really picking up and presumably fanned the burning embers to obtain an open flame.

The open flame was caused by the efforts at 150 feet since the beam at the closer distance had not yet reached this point on the boat (Jamie pointed this out to us when the flame broke out). It is not clear if the switch to silver mirrors was necessary. My opinion is that the switch was not required.

Before the closer range beam reached the burning area on the boat, a substantial wind gust blew over several of the mirrors, creating a rather spectacular effect and ending the experiment. We had modeled that this would occur when the winds reached 14-15 knots. We did not have the instrumentation needed to obtain a wind speed measurement. Thus, we could not make a comparison with our estimated value. We had planned to finish before 2 PM and thereby avoid the afternoon period when the sea breeze becomes quite strong.

The fire at midship continued to smolder with glowing embers and also intermittently burn with open flame. Open flame appeared to be dependent on fanning by the wind. In the picture on the right you can see a very small flame (you may want to look at the large image).