Well...I think this will go down as the best day of the competition, and perhaps in UW History?...

We left off with the end of Day 3, plagued by a submarine crash at the finish line.  It put a damper on the team's spirits, even though we had broken 5 knots just an hour or so prior.  A detail that was not noted in our last post was a broken part of our main hatch latch.  After working to repair the hatch after returning to the hotel, it was determined that the design would have to be designed to make it more reliable.  A trip was made to Home Depot to pick up the proper tools and material (and we thought we had brought everything!), and it was planned to repair the hatch properly in the morning.  The controls system also awaited fixing. 

We arrived on base bright and early again this morning at 7:30am, and got an early start on the work required to race again.  The lower rudder shaft was bent back to its original condition (therefore preventing us from scuffing up another rudder paint job on our backups), and we began steadily working on the latch modification.  As mentioned before, we began shifting weights in the submarine to account for the propeller torque yesterday.  After seven race attempts, it became apparent that our biggest limitation to speed was how much we could torque the submarine and still proceed at an even keel.  The problem is that we had already shifted all of our ballast weight from port to starboard.  As true engineers in nerd form, we whipped out our calculators and came up with a solution.  If we wanted to move more weight around, we would have to make the submarine lighter.

Fortunately, the submarine has an inherent variable ballast: the pilot's scuba tank.  If we raced with less air, we could add more weight to the submarine.  A scuba tank is full at 3000 psi, and is becomes unsafe at 2000 psi.  So our thought was: if we bleed a tank to 2000 psi, how much steel ballast weight could we add to the starboard side? Well it turns out that gives us the chance to add two of our 1 lb steel ballast plates, and actually come out slightly positive in buoyancy.  So we ran the submarine's tank down to 2000, and added two weights.  We also found that taking the tank down to 1500 psi would allow the addition of one more steel plate (just planning ahead, of course).

With the controls, latch, and submarine ballast all adjusted, Dubs' Sub was ready for another day of racing.  The day looked ready to be our day at the races.  The dive team entered the water at 10:00am, to find the David Taylor Model Basin packed with submarines. Some were racing, some were still working to get their submarines operational.  We quickly got our chance to come to the start line, and lock and load.  By this time, the race setup for Dubs' Sub was like clockwork.  The newly developed list from the ballast weight was a bit unnerving.  When we allowed the submarine to sit in equilibrium at the surface, it listed nearly 45 degrees to starboard; not the sort of submarine you want to get into to race.  We hoped it would pay off during racing though.

When given the signal to "GO GO GO" at the start line, the pilot began cranking at a steady, hard pace.  The submarine still wanted to list starboard, so the pilot's effort increased even more.  Our ballasting fix was forcing our pilot to work harder right at the very beginning of the race! Controls were easy to handle with the newly established racing stability, and Dubs' Sub quickly advanced to the 45-55 meter time gate.  At this point, the pilot ramped up his exertion to 100%.  The race became strenuous as the submarine entered the final third of the course, and the pilot was sure this would surpass the previous attempts.

Well, of course, this race couldn't go THAT WELL. At about the 80th meter, both of the pilot's cycling shoes unclipped from the cranks simultaneously, and the submarine went in to a coast.  The pilot immediately pointed the elevators upward in hope to avoid another bottom crash.  Sure enough, the quick input to the elevator linkages caused a small component of the elevator control to break, leaving the submarine completely in the hands of its due course.  Luckily, the submarine slid across the finish line, just before surfacing.  Had the combination foot release/linkage failure occurred any earlier in the race, the submarine would have drifted to the tank bottom, waiting for rescue from the Navy divers.  It was safely recovered at the surface though, and the pilot was removed.

What seemed to be the perfect run ended with a decelerating drift across the finish line.  Dubs' Sub had to exit the water before racing again to make repairs, but did not want to leave the racing queue.  So we quickly exited the basin without feeling the need to tell the race coordinator we might not return in time for our next race.  We brought our boat out of the water, and quickly inspected the damage.  It was claimed by a team member the previous day that the controls' ball linkages had MAYBE two to three more runs in them.  That was four runs ago.  In preparation for such an event, though, we had been working on more durable aluminum linkages to replace the existing nylon parts.  The parts were switched out.  At the same time, the crank clip-ons were inspected, and adjusted to put a tighter fit on the cycling shoes.  Within an hour, the submarine was ready to return to the water.  Just before getting back in, we discovered that our middle portion of the previous run had clocked a speed of 5.27 knots.  This would be fantastic news, but the submarine had crossed the finish line out side of the timing camera's view, and the race was ruled incomplete!  The next race attempt would have to proceed without flaw.

Before we got in the water, we wanted to give ourselves a little extra boost.  The submarine tank's pressure had decreased to 1800 psi, and it was time to add one last steel ballast weight to the starboard side.  It would be up to the pilot now to pedal hard enough to keep the submarine upright and controllable.

At noon, Dubs' Sub and its support diver crew entered the basin with determination.  So many submarines were in the queue for racing, that we returned just as our name was being called to standby for racing.  We were then told to lock and load, and were more ready to race than ever.

At depth, the adjustments to the clip-on shoes were checked to ensure the pilot could safely remove himself from the submarine if necessary.  The submarine was also positioned about 10 feet back to provide a slightly longer run up to the 100 meter course. A team diver returned to the surface to inform the race coordinator that "Dubs' Sub is ready to race!" The underwater signal was given, and the pilot started pedaling furiously from the start.  The submarine passed over the start line at an unprecedented speed, and worked to approach the time gate.  As a quick sidenote, the course is marked by an underwater lighted strip.  The start and finish line, and the start and end of the time gates are indicated by light strips going left and right from the course center lights.  About 15 meters prior to the first end of the time gate, another light strip goes right from the course center lights.  As the diver passed over this other line, he mistook it for the first end of the time gate, and ramped up his maximum exertion early.  He quickly realized his mistake (and fortune) when actually reaching the time gate.  By the team he entered the last 45 meters, Dubs' Sub was blazing through the water.  A straight course was held, and the pilot kept pedaling until he was sure the entire submarine length crossed the finish line.  There was excitement in the pilot, amongst the surface support crew, and amongst UW's support divers back at the start line.  We recovered the submarine from the water, exited through the drydock, and awaited the release of recent performances.

During that run, Dubs' Sub clocked a velocity of 5.650 knots.  Let's say that again, because it just sounds so good. 5.650 knots.  This smashes the old UW top speed by 1/2 a knot!...which is greater than it sounds...

Two years following an ISR in which UW only attempted, and aborted, one race, we set the new school record for speed!

Given this success, it was time to get another diver some good practice in the submarine.  The dive crew geared back up, with a different member in cycling shoes.  The new pilot had not once entered the submarine before today, so there was a new nervousness about the fate of Dubs' Sub.  The team requested an area in the tank to test the new pilot, and check that he could pedal comfortably and control the rudders and elevators.  The new pilot has much larger feet than the other, and requires larger clip-on shoes.  Sure enough though, the pilot accommodated for the small submarine clearances, and could produce a smooth cycling cadence.  Once buoyancy was double checked with a new diver. 

The crew immediately requested to be put in to the race queue, and was back at the start line 30 minutes later.  The new pilot was given the signal to go, and began pedaling rapidly.  He had been instructed to proceed cautiously to ensure that the course could be navigated safely, but adrenaline must have kicked in.  The dive crew watched the submarine disappeared into the basin murk quickly. 

By the time the dive crew surfaced, Dubs' Sub had already completed another race, and behind new legs!  The pilot returned to simply say "That was really sketchy."  Sketchy or not, we completed another race successfully.  Dubs' Sub has now reached the finish line in 9 of its 10 races; a record that may only be rivaled by the United States Naval Academy (to be subtle, they are pretty good at what they do, breaking and re-breaking world records each day we've been here).  We also put a second pilot in the water, and have started building crucial experience for the next UW team.

We will move forward tomorrow morning with giving the pilot another couple of runs, and hopefully increase his speed.  Racing wraps up at 3:00pm, and we hope to have a calmer, celebratory day at Carderock.  For everyone that stuck around for this entire post, I apologize for its length. We are just very excited!

There should be some great race pictures and hopefully a video or two available tomorrow.  Thanks for tuning in!

Also, please forgive any typos or grammatical errors; I have spent a lot of time underwater this week.