Watch me build my autonomous solar 20-footer...

One of the new anti-fouling coatings might help in the above.
We are seeing two year and greater service on the Prop-Speed product.

They perhaps would desire the advertising provided by your autonomous boat.

 

I sat down this weekend with an experienced sailor who's made the SF-Hawaii trip 7 times. His comments were

a) my solar panels are going to get torn off

b) my prop, even a folding one, is going to get fouled. In fact he said on two trips a folding prop got fouled so badly as to require going overboard to free it by hand. Obviously thats not an option.

To solve a), which I'd always worried about, I figure I'll just have to bite the bullet and glass the cells to the deck instead of using commercial panels. This will require a heat exchanger to keep the cells cool, but thats a second order failure mode compared to the threat of the panels getting ripped right off.

To solve b)... well, I dunno. I think I'm going to have to put a screen/basket/cage around the prop. I'm sure this will suck from an efficiency standpoint, but I guess I'm not trying to win any races.

Other ideas are welcome. The propeller is a non-redundant system, hard to escape the problem.

 

a) Aluminium inserts in deck

b) http://www.streamdancer.com/

Rick W

 

a) The concern is that, since I left space beneath the panels for airflow and the curvature of the deck, that when the boat rolls they'll be torn off. The other problem would their unsupported middle getting crushed. My plan was to build steel frames to attach them through the deck right to a bulkhead, but that doesn't really mitigate the second problem.

b) Hmm. Is that you telling me that you think a shroud and screen of some type will be so inefficient as to be infeasible? I can't say I'm excited about developing and testing a screw like that, that'd be a significant unknown...?

 

Aluminium gives good heat transfer. So you can build a shroud around the panels using aluminium to give less obstruction for green water. Alternatively make the deck flush with the panels and epoxy aluminium plates in the deck to imptove heat transfer into the body of the hull.

The auger is a suggestion to beat fouling. It will be low efficiency compared with an unfouled prop but significantly better than a prop fouled.

Flapping foils can be made better than 80% efficiency. It would be shaped like a fish tail with round steel rod supporting a flexible rubber centre. Something similar to a dolphin tail. Needs to have a pivot arm and a driving rod. Have you seen the Hobie flappers. It would be a variation of this. Some development work.

I think a folding prop behind an aft raking skeg would be almost immune to permanent fouling. You can set up a fouling sensor based on water speed, wind speed and motor power. Cycle between forward and reverse a few times until it is freed.

Another method is a tilting outboard leg that allows the prop to be elevated from the water and spun at high speed in air. This tends to get rid of weed.

Fishing line can damage shaft seals when it wraps around the shaft.

I have knife sharp trailing edges on my props so they cut stuff up when I reverse. Possibly a little hazardous.

Rick W

 

Andrew
I like what you have done with the belt box:
http://blog.lonelybot.com/

Also I am impressed with the servo table on your little mill. Did you make this or is it something that is supplied off the shelf with the machine?

Rick W

 

Thanks! Believe it or not I've been paused on the belt box because the 90T timing belt pulleys I ordered were designed incorrectly! - belts fit, but not without undue tension because the leading edge of the teeth are too wide. The replacements should be arriving soon and then I can get back to it - the bearings are fairly tight, so I plan to run the box nonstop for a few days to run everything in and see how the drag current evolves.

I'll be making a post on it in the future, but the entire system is going to run on a serial bus, so the motor controllers I built will report the system voltage, current, and RPM in realtime to a PC. I'll be able to plot the drag torque as it runs in, I think it'll be interesting.

As for my wee milling machine, thats all homebrew. I built it, gee, maybe 8-or-so years ago now and have slowly upgraded it with new motors, bearings, power supplies, etc along the way. The interface board is off-the-shelf from hobbycnc.com, the steppers were ebay surplus, and the 42V psu came out of some crazy koi pond equipment. My engineering skills have evolved with time, so if you'll forgive me for being a young and inexperienced when I built it, there are some details at my old old website here: http://www.sci-spot.com/Mechanical/cnc.htm

 

I'm not dead!!

The hull is largely complete, as is the gearbox and propulsion control tray. This weekend Lonelybot is heading up to the "Maker Faire" in San Fran to drum up some interest.

 

Andrew
Look forward to the feedback. It seems a shame that you will set that off on its own voyage.

Rick W

 

Aww cmon Rick, gotta break some eggs....

Working on installing running gear and then I'll ballast it with some concrete and do a "lake trial" to measure the propulsion efficiency.

 

At long last I got the motors and belt box running - I'm drawing about 5A with no load at 1500 prop RPM. I'm going to set it up with a power supply and let it run for a month or so, see if it calms down a bit. The main shaft is on large greasable pillow block bearings - I have known these to be a bit stiff while the grease redistributes itself. I also think the toothed belts could use a bit of wearing-in.

Anyone (Rick?) have a number for the reduction-box losses on their electric boats so I can compare?

http://blog.lonelybot.com/2010/08/propulsion-interface-completed.html

 

Do let us know when you are about to launch - I will await just over the horizon to pick up this neat little boat with lots of good electronic gear, a pc and batteries with my crab pot lifting gear

 

I've just crossed you off my list of possible Australians to ask to meet up with my boat...

 

haha - yes, lucky I was wearing a mask when I wrote that. Actually, the thought just occurred to me, you are probably going to run foul of customs. Other threads - eg "concrete submarine", had links to lots of youtube videos about semi autonomous vessels used to run contraband. mostly drugs.

I know that australia is paranoid about manned vessels approaching the coast, I bet an unmanned vessel would get lots of attention - especially if you get near south america.

Have you thought about using an Automatic Identification System (AIS) to identify the craft, so it doesnt get run down, or picked up by customs ?

I would be tempted to get some kind of video feed through a satelite link, so you might be able to watch and identify any approaching vessels or people, so you have an idea who stole the whole boat.

While I have my black hat on, have you investigated your legal liabilty in case of damage to others (boats or people) ? You may get summoned by a Japanese fishing boat for damage to its nets or fishing gear when it pulls up your boat. Even down to the boat getting beached, and someone losing a finger when the exposed prop whizzes into life. Gee - letting my imaginatin run wild - your boat strays into the path of a jet ski, or a swimming only area etc etc.

food for late night thought !