So I was a bit concerned that Javier seemed to have such a short amount of time on his battery pack, so I did some searching.  Apparently considering his price, this shouldn't be a huge surprise;)  Upon closer examination, his battery pack is only rated at 9.6 volts for 500 mA hours.  Thats not a lot at all.  Hes got 8 double a cells in series and each therfore is only rated for 500 mA hours.  The double A's I have in my camera are good for 2500 mA hours, or fully 5 times what we were using...  a quick web search found what I think is the sight I used to go to for batteries:

NiMH Batteries
Bottom line: 16 pack for $45, or $22 for what would be in the boat at one time.  That would have 2700 mA hours , or 2.4 times the total power we had in one of Kenny's big old c cell based battery packs (almost his total power :-!).
25.92 watt hours for 8.
weight: 26*8 = 208 grams total

Or these are even better for ~$18 for enough for our needs: Nickel Zinc Link.  Cheaper per unit energy, 30% lighter and less volume (only need 6 instead of 8)
24 watt hours for 6. 
weight: 156 grams total

A completely different option would be to use Lipo that are crazy light and powerful: LiPo Link.
24 dollars for 7.2 volts*2000 mA hours. 
14.4 watt hours for 1. 
weight:110 Grams total

Another LiPo option:11.1 V * 1500 mAhr
16.65 watt hours for 1
weight 142g

Hmmm, Thats less than incredible compared to the high end ni based rechargables.  Also, they are not as durable as the others should we completely discharge them accidentally. Looks like the NiZn for about $18 above are the best bet.

Just got out of our first communications committee meeting...  It seemed pretty straight forward.  We were a little unclear though on if and why we needed to know who our team mates were.  Other than that, communications to our own devices will be handled by us, and communications otherwise ae pretty much just sending and receiving the atoll captured messages...

So I've been thinking about general design ideas while I went to SPDL and discovered the communication committee meeting got pushed back an hour.

One major thought:  our Illustrious coach mentioned the other day that there was no requirement to actually make the boat from scratch!  He said that about half the people from his year used existing boat hulls and modified them to suit their needs, and the other half started from scratch.  He also said that some of the guys that built from scratch had a major disadvantage in that they didn't have anything to test till late in the game.  Perhaps it would be a good idea to get Javier working fine first off, while we work on a boat, and should the worst happen, its no biggy.

Second thought:  Instead of speed, there is a decent chance we will be more limited by a need for agility as we maneuver around the tight quarters of the atoll trying desperately to make the RFID Cards line up and read.  We have to be literally within inches, which may not sound that bad, but its in every axis, and I would imagine may be even more sensitive to out of alignment errors.

The propellers are really nice as they are easy to implement and really fast, but we might still want to keep in mind a dual paddle differential  wheel design as well.  I would imagine it would be more agile.  The obvious trouble is the increased mechanical complexity.  A couple of things are good here though:  I think perhaps the load on the motor is not actually as bad as it sounded at the beginning.  Since its a boat, and not wheels, it wont have to carry its own weight on the motor shaft.  If we extend the motors into the area of the paddle wheels, it may not be impossible to center the load in such a way that its largely just sheer on the shaft.  The goal would obviously be to make these things as light as humanly possible, so the weight of the wheel shouldn't be huge, and then if its made of foam (more on that in a minute) then it might actually end up being at least partially buoyant.

At first I was thinking about using like acrylic or something for the paddle wheels, and then I remembered how incredibly light my helicopters are, with a surprising amount of strength.  what if we used closed cell Styrofoam, as the structure and then laminated the outsides with a layer of waterproof aluminum foil tape??  They sell it on mcmaster, and it looks like it might actually be legit.  I've used regular aluminum foil tape before, and the ahem, "stuff" is ahem "freaking" fantastic! Super stiff and strong, the styrofoam is just there to give it a distance on 2 layers apart.  I'm not saying this is the way to go, but it might be worth a quick prototype.  If we can get the weight down, paddle wheels might be really useful in tight quarters.
found a video of a dual paddle bot. completely random art design, and worst paddle design ever, but still looks pretty dang agile and simple:

http://www.societyofrobots.com/robot_thai_boat.shtml

Also, Hoff from class got a little 3 axis accel from spark fun.  Seems pretty surprisingly simple.  analog out for each axis, and we have analog in on the pic.  Might be an ok option for one of our sensing modes.

Ok, thats all I have for now...
-D

David went out and bought a cheap RC boat at Fry's.  We drove it around the Halo fountain today, in and out of the falls and over the lights, until the battery (we think / we hope) gave up on us.

We received the project today.  We started thinking about and researching what sort of propulsion mechanisms our vehicle could take.

Some boat and underwater ideas, from YouTube research.
 - Can DC motors go underwater?  Yes, if they are brushless.
 - Might a paddle wheel work?  Sure, but maybe slowly.
 - Something crazy?  Swamp boat!