Solar boat

[philSweet]

I goofed on the weight of the driveline. I quadrupled the weight of the 100AH battery instead of the 50Ah battery. 250 pounds ought to do it.

[michael pierzga]

Those 12v electric trolling motors draw about one amp for every lbs of thrust produced. A 50flb thrust unit draws nearly 50 amps.

4 solar panels produce a total of 12 amps ? so I guess this mean max thrust avaible would be 12lbs.

[kengt]

Thank you all for your helpful input. It is alittle too technical for us so if it is possible to keep it sort of simple to understand if possible. We have inserted a link to the website for the regatta. Please note that if you read any of the rules that there are changes in the rules and the sponsers have not yet up-reved the rules. And yes this is the first time for this regatta so the rules maybe in conflict and we are all trying to sort it out. Our goal here is to assist a 6th grade(11 years) class to design and build a solar boat. This project is very difficult for students of this age group, so I am trying to help them distill available knowledge and designs into a good starting point for their first solar boat. The hope is to be competitive and allow the student to become familiar with the design process a young age. The focus of the team leader(teacher) is the get help on the design and the student execute the design and competition.

I will be trying to digest all of your input.
Best Regards,
Ken and Jennifer(pilot of the solar boat-75lbs)

https://www.smud.org/en/about-smud/e...ar-regatta.htm

[Boston]

75lbs Hmmmm, I'm betting there's bound to be a kid in the 50lb range in that class somewhere. each pound is going to make a huge difference in this race.

a 12v 100 amp battery wont actually deliver 100 amps in 1 hour, it will get hot and its efficiency will go down. So you might think of some way to cool it off, something like dry ice or whatever's light. Actually for the 200 yard dash you might think of packing the battery with dry ice just before you start. What do you think guys, is it worth the effort ?? to cool the battery

you also might consider a used electric trolling motor, Lots of them are designed to run off just one 12v battery. This will simplify the issue for the kids. Rather than mess with controllers and what not. The trolling motors have them all built in.

another consideration is if the rules mention you can swap out motors for each part of the race. If so then get one trolling motor with maximum potential for each of the individual conditions specified for each race. One that will run best just off the panels and one that runs best off both the panels + battery.

I'd use the light weight one for the regatta and save your battery life. Anything which isn't a speed event, go with the smaller motor. Also the device to orientate the panels I predict will be the tough part. Thing to remember on that one is that any shadow that falls across the panel reduces its efficiency, so your going to need a frame that holds them all from bellow. From there use a gimbol system of arches should keep it simple, but now how to orient the system. It would be a lot for one kid to handle but you don't want to increase the weight and have two kids. So some kinda automated system will be needed. Hmmmmmmm

Anyone got a solution to that one ????????

[kengt]

Has anybody had a chance to read the spec?

[kengt]

does anyone have any comments?

[michael pierzga]

I only had a quick look...race time is High Noon. Sun at max elevation so good power available. .. I didn't calculate sun azimuth and declination for your location to get an idea of what solar panel placement may look like.

Personally I don't like high tech competition involving young people, the winner will always be the one with the deepest pockets.

I would attack from a different angle and create a boat in which your daughter has more fun and laughter than anyone else in the fleet. A simple boat, a simple power plant created to be fun and make memories . For example if your daughter likes frogs, create a paper mache frog covering over a simple putt putt rig , then steam down the course laughing and giggling.

It would be wothwhile if the race committee choose an off the shelf powerplant...one of those electric trolling motors ...and just like specifing the panel type, battery type , they made life easy for competitors by specifying a stock powerplant. The object of the competition is to teach kids about solar power and boats. Drive train development is beyond family fun .

[philSweet]

Yes, agree with Michael. The rules for this comp basically fail at the most important aspect of this kind of an event- Creating a well balanced goal that has a high success rate but also will distinguish good from less good competitors. It is very difficult to get it right the first time. If a company develops a power craft, the first edition is usually underpowered in order to work out the kinks. A 26Ah 12V scooter battery would make a good spec for a first run. As it is now, you need to carry between 120A and 200A at 12 volts for the endurance run. That suggests four of the these- http://www.sunelec.com/5-foot-invert...awg-p-136.html . Two to get to the throttle, and two to get from the throttle to the motor. That's more than $280 for wire in order to keep losses below 2%. I just don't think that should be what determines the winner. A $100 scooter battery (top of the line) could be wired for about one tenth as much. They need to create the environment for success, and they haven't done a very good job of that. There have been dozens of solar challenges all over the world, why don't the sponsor's copy one and get some experience before they get creative.

[michael pierzga]

Fun and fantasy are also important to the image of an event.

I think id go with a simple plastic kayak then with blocks of foam graft a swordfish onto it , paint her up, support the panels between the dorsal fin and tail, power by some off the shelf trolling motor and let kids HAVE FUN.

[philSweet]

Also, I am not aware of any commercial kill switches that will directly and positively break 200 amps. You would have to scavenge an outboard switch or a treadmill switch and use it to deenergize a contactor. Suitable contactors aren't cheap. Or build an actuator cam for tripping a 200A breaker.

[kengt]

Thanks all, we will get a swordfish and go have fun

[kengt]

In my past experience with forums, it has been a colaborative experience. If you see a problem with the rules then please help us understand how they could be re-written to even the playing field. it is a waste of time to just ridicule them. I know this is the first Regatta, but will your knowledgable input we may be able to make it great. Thanks

[philSweet]

some ideas from a couple very well run cardboard canoe races.

1. In addition to the main event races, there should be some shore side judged events such as a boat presentation where a team member explains the boat to the audience. A team cheer and a team flag are additional possibilities. This gets more people involved in the team.

2. Piggyback off another event rather than be a stand alone event. Can it be tied in to a local fair or some district wide school event? This gives you an audience and makes for good photo ops for the local paper.

3. Control the most important aspect of the race very closely. In the cardboard races, teams are usually issued a rather small roll of colored duct tape. Each team gets a different color. The race committee seems to already be doing this with the PV panels, But I think it would be appropriate to issue the battery as well. This would be done after a visual inspection by the judges and a float test. The battery would then be "presented" to the team. The battery should be secured to a mount provided in the boat.

4. The entire event needs to be kept on track and on schedule. The cardboard races were conducted by a couple who did it for a living. They had done literally hundreds of them. Get a first rate MC. The person with the microphone WILL make or break the event.

5. Figure out how to get the lead time down. You shouldn't need a month to prepare for a kids regatta. Ok for the open division, but the kid's races should be able to be done with one weekend of prep at the most.

The wire sizes and types could also be specified. I would suggest you require that all teams use a commercial trolling motor for propulsion. Or have two divisions, a junior division with less tech and an open division for college and technical competitors. As I mentioned earlier, for kids, it is desirable to have more than one in the boat. The second one could aim the PVs??

I found the requirements regarding safety a bit puzzling to the point I wouldn't know where to begin to comply with them and have a boat that works. Perhaps you could get some better advise from an electric boat maker such as Duffy or from an NMEA rep.

[JosephT]

At first glance I would take a light solo racing/recreational canoe and add the required gear. Solo boats can be operated & remain well balanced by one person. You want a combo racing/rec model because you want both speed & maneuverability in the slalom. Something like the model below would be a good choice.

http://www.clippercanoes.com/boat_sp...p?model_id=140



Below is a write-up on the hull which reinforces my point:

"The Freedom has a shallow arch hull and soft chines, all adding up to great stability. This canoe tracks well and is easy to maneuver when leaned offside to execute a tight turn. The seat is adjustable to three different heights and also slides fore and aft for maximum versatility in various water conditions."

Also suggest storing the batteries just forward of center so the bow is down slightly...this helps increase speed.

With a light, fast & nimble boat like this you'll give the competition a run for their money.

[Boston]

great Idea Michael, I was struggling myself to keep up with some of the more technical suggestions and I can only imagine how tough it might be for the kids.

Keep it simple and have a great time. If you win great, if you have fun, fantastic.

Best of luck
B