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[Gaffers]

Hi guys,

This post is more about my second hobby which is sailing and, recently, building boats.  I am building a 11 foot dinghy at the moment which I hope to use as both a sailing boat AND a fishing boat.

I am also eco-aware when it comes to the sea (dont get me started on rubbish on the beach) which obviously means I will be getting an electric trolling engine run off a 12V battery.  Even with the latest motors one 12V battery may not do the trick and if I am on a fishing weekend covering some large distance on the English south or German coastlines I will have to recharge it at some point.

I have thought about a bank of batteries but looking at the design I would not be able to fit more than 2 and then the electrics can get ... well...interesting....  Besides I would feel safer if I had a hydrocarbon backup system as well as my obvious sails to fall back on.

I am looking at using a very small 25-50cc engine rigged up with an alternator that I can use for recharging the battery.

Has anyone seen/done this before?  Got any thoughts?  Will a 50cc be big enough to turn the alternator at sufficient speed? before I start getting things pointlessly welded...?

ttfn
Gaffers

[zippo]

Hi guys,

This post is more about my second hobby which is sailing and, recently, building boats.  I am building a 11 foot dinghy at the moment which I hope to use as both a sailing boat AND a fishing boat.

I am also eco-aware when it comes to the sea (dont get me started on rubbish on the beach) which obviously means I will be getting an electric trolling engine run off a 12V battery.  Even with the latest motors one 12V battery may not do the trick and if I am on a fishing weekend covering some large distance on the English south or German coastlines I will have to recharge it at some point.

I have thought about a bank of batteries but looking at the design I would not be able to fit more than 2 and then the electrics can get ... well...interesting....  Besides I would feel safer if I had a hydrocarbon backup system as well as my obvious sails to fall back on.

I am looking at using a very small 25-50cc engine rigged up with an alternator that I can use for recharging the battery.

Has anyone seen/done this before?  Got any thoughts?  Will a 50cc be big enough to turn the alternator at sufficient speed? before I start getting things pointlessly welded...?

ttfn
Gaffers

wouldn't a red blue or yellow top battery do the job. Like the type used on a 4x4 (to power winch &lights)
blue 75 ah
red50ah
yellow55ah
and some sort kind of solar charger all eco friendly only a thought or have i missed the point
 darren

[Gaffers]

I had thought about it but would the solar panel create enough juice for me cruise continuously on the battery?

I have seen some solar cellsthat generate 10W+ but I am not sure if I would be left up the creek without a paddle....or any juice !


Gaffers

[x25xe]

I doubt that even a 10+watt panel will do what you require.  Besides which they are ruinously expensive!

What you propose could work, but you would need to know how fast the alternator needs to spin in order for it to generate useful power.  You would then need to know how fast the engine you propose to use turns and sort the gearing.

Alternatively, some of the smaller generators have a 12 V tap on the alternator so you can use them for charging batteries.  If you had one of these, you would have the useful benefit of have 240V as well.

Hope this helps

[Entwood]

There are numerous small generators available for less than £100 that would probably do what you want, and at that price is it worth the hassle of building a bespoke system ??

http://www.screwfix.com/prods/89480/Power-Tools/Generators/Sumo-2-Stroke-Generator-650W;jsessionid=KLBPMWL0XPIDECSTHZPCFFQ

or

http://www.tvepowertools.co.uk/wolf-power-generator-2-stroke-720w-wlfwp980-659-p.asp

and I'm sure you'll find loads of others if you google ...

[Kevin Wood]

My father recently bought an 800 watt 2 stroke generator for 50 quid brand new. OK, the voltage is wrong but for that money it hardly seems worth messing about, as said (if you just want to charge the battery). The output was dirty as hell, by the way, so don't anyone buy one of these to power anything sensitive! You'd need something to take this down to 12 volts, of course. I'd probabl;y have a look for a substantial 12 v switched mode DC supply,  but that would cost you more then the generator unless it came out of a junk box somewhere.

If your plan is to run the outboard and / or charge the battery from the generator then you would be better off with a vehicle alternator IMHO. Have a look at your pulleys and guesstimate the ratio of drive to the alternator. I would take a guess that they need to run at around 5,000 - 10,000 RPM which might allow you to direct drive it from some 2 strokes. Alternatively a 4 stroke lawn mower engine typically runs at 3,000 RPM or so and would need gearing up a little.

They do need the "battery light" circuit wired up to a 12v supply via a bulb to provide a little current to "self-excite" the alternator at start-up.

Regarding power, let's say you got a 100 amp alternator. 100 amps output at 14.4 volts is just over 2hp. The alternator won't be 100% efficient, of course, but clearly a 3HP mower engine would be ample. 100 amps will charge the battery and run the outboard with output to spare!

Sounds like a fun project.

Kevin

[Golfbuddy]

If you're building a sailing dinghy, and you want this to power your auxillary motor which is to run off the batteries. Wouldn't it be possible to use a wind powered generator, which could recharge the batteries whilst under sail or when at anchor for fishing.

I have no idea if this would be feasible or cost effective but, seeing as one of your motivators for an electric motor is environmental, this would seem the most environmentally sensitive way forward.

 

[Gaffers]

I have looked at the wind and solar alternatives but I dont think they would produce nearly enough power if I was constantly using the motor, besides they cost a fortune!  More than the boat is costing me to build inc sails!

I think I can get one built up as long as I find out the speeds required for the alternator and step up the gearing accordingly.  I wonder if it can be done?!  We'll see.

Gaffers

[zippo]

sorry mate not got a clue

[zippo]

excuse my ignorance  but whats the difference sail/dinghy boat
Darren