Notice. New forum software under development. It's going to miss a few functions and look a bit ugly for a while, but I'm working on it full time now as the old forum was too unstable. Couple days, all good. If you notice any issues, please contact me.
Hi, I am new to the forum. I am planning to build a generator for my sailing yacht, charged by a propeller which I will tow on a long line. There are commercially available models, very expensive. So, in contrast to the usual thrust against the unit, this would put load away from the unit. Can anyone tell me is the F & P suitable for this? Also, which model F & P is best for generator purposes generally? And further, what do you do for a regulator on systems, including the wind generator? Thanks
MacGyver Guru Joined: 12/05/2009 Location: United StatesPosts: 1329
Posted: 04:53am 31 Jul 2009
Copy link to clipboard
Print this post
Just an idea:
How about manufacturing a small Savonius rotor that could be placed
between the genoa and the main sail in a long reach (like night sailing) to
take advantage of the concentrated air stream between the two sails? It
could be direct-coupled to a stepper motor and generate electricity to be
stored in batteries.
If you kept the rotor close enough to the main mast, you'd be less likely
to foul it in the jib or genoa when you came about. It could even be
made so you could shift its position to port or starboard, thus taking full
advantage of your apparent wind.
If I were going to manufacture my own towed yacht generator, I think I
would use two pontoons and a paddle wheel and tow the thing in close to
the transom. I like to keep things super simple.
Towing a propeller on a shaft at the end of a submerged line reminds me
of using a sea anchor, not to mention fouling the line in a hard about like
a man overboard; no thanks! I suppose such a thing could serve a dual
purpose, namely, with a plastic bottle tied near the end to act as an
overboard safety line as well.
Just a thought.
Nothing difficult is ever easy!
Perhaps better stated in the words of Morgan Freeman,
"Where there is no struggle, there is no progress!"
Copeville, Texas
Well, ideas. The ondeck idea probably has merit, but I already have a wind generator on deck. Problem is, if sailing downwind, as most trade wind sailing is done, the apparent wind drops away. In daylight I have solar panels, but at night power consumption is up, with lights, radar, etc., and a water driven generator would fill the gap. Thanks for the input.
Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904
Posted: 01:14pm 31 Jul 2009
Copy link to clipboard
Print this post
kimiki, I too have a sailboat and have considered your ideas in the past.
The F&P is, IMO too large for a rail mounted towing generator. Also, the propeller might spin too slow at average sailboat speeds to suit the F&P. You would have to complicate the issue with gears. It might be easier to try towing an electric (Minncota?)motor which has already the propeller, this needs a tow line that prevents rotation or the separation of motor & propeller.
You would have to fit some means of disconnecting the batteries from the generator if they are fully charged, The propeller only spins as fast as the relevant boat speed so free wheeling should be no problem.
With a wind generator you must NOT allow it to free spin by removing the load. Since you cannot do anything about the wind speed there is a real risk that the thing over spins and self destructs. There are dedicated wind generator regulators around, most switch to a dummy load once the battery is full.
On my boat (26') there are 4 solar panels, adding up to 140W if all get the sun on them, rarely possible while sailing. I also carry a small Honda battery charger which puts out 15 or 30A for 12V battery charging. My boat is too small for a permanently fitted wind generator, unfortunately.Klaus
readyakira Senior Member Joined: 17/07/2008 Location: United StatesPosts: 114
Posted: 02:57pm 31 Jul 2009
Copy link to clipboard
Print this post
I think the paddle boat style is a pretty good idea, but definatly you would need some sort of gearing. The blades I would think need to be of a decent size to overcome gearing and load. With that you could easily come up with some sort of disconnect for the gearing to put the mill in neutral and allow only the blades to turn. I would think with water having a much higher density(?) then air it would take a smaller size blade for the same torque but the gearing is going to drive the torque requirements higher anyways. I would think to use a F&P you would need a floating style as it would be easiest to build if it did not need to be so waterproof and only water resistant.Don't you think Free/Renewable energy should be mandatory in new buildings?
04 Marine Newbie Joined: 20/11/2009 Location: United StatesPosts: 4
Posted: 08:19am 20 Nov 2009
Copy link to clipboard
Print this post
Hi Folks,
I'm also a new guy to the forum but closer to being a fossil age wise. I was researching towed and shaft powered marine generators when I discovered your forum. Wow, what a find.
I work mainly in CNC metal art as my retired stay busy activity. My entire shop is CNC powered, plasma table, lathe and mill. However, I'm light on electrical terminology, so please excuse the keep it simple requests.
I'm am currently fitting out my Ingrid 38 sailboat with the intent of taking a shot at a solo non-stop circumnavigation in the fall of 2012. The amount of planning, preparation and boat modification is astronomical so that gives me two years to finish the boat, a year of sea and body trials and then I off.
Thanks for letting this old Marine be a part of the forum.Life is an adventure!
Age is only an indicator of experience Gained!
Attitude is the fuel that takes us from one adventure to the next!
One site I have found that looks at towed generators is http://www.tradeaboat.co.nz/View/Article/Build-your-own-wind trolling-generator/662.aspx?Ne=0&N=0&No=270. Hope this helps.
04 Marine Newbie Joined: 20/11/2009 Location: United StatesPosts: 4
Posted: 07:15pm 21 Nov 2009
Copy link to clipboard
Print this post
Kimiki,
Thanks, that is a great article. It will definately help.
Glen Life is an adventure!
Age is only an indicator of experience Gained!
Attitude is the fuel that takes us from one adventure to the next!
Also go to http://ssca.org/phpBB3/viewtopic.php?f=6&t=5801&start=15
KiwiJohn Guru Joined: 01/12/2005 Location: New ZealandPosts: 691
Posted: 07:08am 23 Nov 2009
Copy link to clipboard
Print this post
Hi Kimiki, I have a little experience of blue water sailing including one Pacific crossing and I can see the attraction of a towed generator.
I think a F&P would be ideal for the job as it outputs useful power at quite low revs, it is an open construction and maybe easy to protect with suitable paint etc and of course they are cheap!
We used a very simple Sturmy Archer bicycle hub generator which was connected by chain to the prop shaft which turned quite briskly in good sailing conditions. We only got a few watts from that, just enough to run a small cabin light at night but I am sure a F&P would do much better than that though I doubt our small propeller would have driven a F&P.
Do you have ideas about the towed propeller? I think you should be prepared to loose a couple. I never got around to making one but I did think that a suitable prop to tow would be some simple blades screwed to a few feet of broom stick and towed with a solid wire, say 12 gauge single strand fence wire. Just my idea at the time.
I do not think regulation would be a big issue as I presume the rpm of the towed device would be a lot steadier than a wind generator. Because the F&P is so open in construction you can connect the coils to get a voltage suitable for charging batteries just by changing connections and only the most simple of regulator would be required, if any.
Remember you cannot troll any fishing lines at the same time!
Edited by KiwiJohn 2009-11-24
04 Marine Newbie Joined: 20/11/2009 Location: United StatesPosts: 4
Posted: 07:58am 23 Nov 2009
Copy link to clipboard
Print this post
Hi Guys,
Excuse my lack of knowledge, what is and F&P?
My Ingrid 38 weighs in at 27,000 pounds and has a 3 blade 16" 12" pitch propeller. I'm looking at both towed and shaft generation posibilities.
Many thanks for the great responses and support.
GlenLife is an adventure!
Age is only an indicator of experience Gained!
Attitude is the fuel that takes us from one adventure to the next!
KiwiJohn Guru Joined: 01/12/2005 Location: New ZealandPosts: 691
Posted: 07:18pm 23 Nov 2009
Copy link to clipboard
Print this post
Hi Glen
F&P is 'Fisher and Paykel' a company that makes home appliances and the product we are interested in here is the motors from their Smartdrive range of washing machines. You will see a lot of references to these motors on this website especially under the windmills topics.Edited by KiwiJohn 2009-11-25
Re the shaft, as far as I have heard from other cruisers who have made or seen them, typical is a length of stainless steel shaft, about one metre in length, with a prop from about a 6-8 hp outboard motor, being towed with a double braided, fairly stiff line, about 25 metres in length. I suppose it would pay to have some sort of breakable (but not too easily) link in the towed arrangement, should it be snagged by something big - or taken by a big fish. Although it would take a BIG load to break line about 12mm thick, and the shaft and prop are basically indestructible. My original query re the F & P motor was regarding its suitability for the task. They are readily available, but the ones I have seen are more suitable for the thrust load of a wind driven prop, rather than the pull load of the towed prop assembly. Any ideas? Thanks.
04 Marine Newbie Joined: 20/11/2009 Location: United StatesPosts: 4
Posted: 04:27am 24 Nov 2009
Copy link to clipboard
Print this post
Kimiki,
One area where I have some experience is building things out of metal. I would consider an idler arm set up with a thrust bearng. The idler arm tension could be adjusted to keep the belt taunt. This would take any load off of the generator portion except for belt loading. It would also allow for a quick change out of the generator by reducing belt tension, unbolt the generator and pulley, replace and re-tension the belt. The entire unit could be enclosed within a small containment system with nothing more than the eye for the attachment of the line exposed.
Glen
Life is an adventure!
Age is only an indicator of experience Gained!
Attitude is the fuel that takes us from one adventure to the next!
KiwiJohn Guru Joined: 01/12/2005 Location: New ZealandPosts: 691
Posted: 05:17am 24 Nov 2009
Copy link to clipboard
Print this post
As it is mounted in the washing machine the stator is bolted to a hollow aluminium extrusion which is imbeded in the plastic of the washing machine bowl. It is important when parting out the washing machine to get this bit as it includes two quite common ball bearings on a stainless steel shaft of almost 1" diameter (I think it is 22mm). I cannot imagine that the stress of a towing cable on the end of that shaft would be much more than that of 10kg of wet clothes spinning at 1000RPM! The rotor is outside the stator and is made of a plastic that needs to be painted to protect against UV damage from the sun, the internal of the rotor carries the magnet faces and I assume they should be protected against marine environment by paint. The stator is mostly plastic but it does have iron laminations that would need to be protected.
I could not suggest that the F&P is ideal for a marine environment but on the other hand I am confident that sensibly painted and protected with expoxy or some such it would have a somewhat useful lifetime.
Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904
Posted: 03:43pm 24 Nov 2009
Copy link to clipboard
Print this post
KiwiJohn, I beg to differ. As I understand it, the F&P bowl 'floats' in its plastic outer housing so there would be little axial stress on the shaft during the washing machine cycle.
Towing a propeller at 5kn plus speeds does put a considerable strain on the bearings via the large nut on the F&P shaft.
While I agree with you that the F&P does make a good low speed generator I disagree with its salt water environment usefulness, even for a shortish trip.
As a sailor I only know too well that it takes only one drop of the brine to slowly eat its way through copper and the many coils of the F&P & exposed iron poles are difficult to seal or house in a suitable waterproof case unless one is making a special F/G housing for it.
Besides, The F&P is rather a large diameter beast to clamp to the rail, I would be happier with something half its diameter if I wanted to tow a generator from the cockpit of my yacht. Klaus
KiwiJohn Guru Joined: 01/12/2005 Location: New ZealandPosts: 691
Posted: 05:54pm 24 Nov 2009
Copy link to clipboard
Print this post
Klaus, you would be right about the stress in the washing machine but I still think the basic machine is plenty strong enough to handle a towed propeller.
Like I said, it is not ideal for a marine environment and neither is the shape and size optimum for that use.
If I was still sailing I am sure I would have tried one but I am not so all I can offer is an opinion.Edited by KiwiJohn 2009-11-26
One suggestion I have had is using the electric motor which is commonly used on hard drives in big computers. Must be very big. Apparently they run out at about 40 volts, so put out more useable voltage at lower revs. My friend had seen one in action, on a yacht, apparently worked well, and its owner had found the motor at a scrap metal place. You would have to be lucky to do the same. So, how to come by one, and how expensive? This dialogue is useful, I had put the project on the backburner, but am getting interested again. Thanks, Kimiki.
KiwiJohn Guru Joined: 01/12/2005 Location: New ZealandPosts: 691
Posted: 01:07am 25 Nov 2009
Copy link to clipboard
Print this post
Kimiki, I think that old computer motor would be one from an old mainframe computer's tape drive. I actually have a couple in my garage but I 'saved' them almost 20 years ago and I can not imagine there are many around now. They are not made of really marine suitable materials but they are of a more convenient size and shape and would, maybe, be easily protected in a piece of plastic drain pipe with end fittings. They are about the shape and size of a quart bottle.
What you need is any low voltage, permanent magnet motor and with the increasing availability of really good magnets there does seem to be more of these motors around in all sorts of things including electric bicycles. If you can find any salvage or surplus place with motors and stuff on sale you can easily test suitability. First, test that the motor spins freely without any graunching bearings or obvious loose bits inside then twist the wires together and it should be much harder to turn using fingers alone, the harder it is to turn the more likely it is to be an effective low RPM generator.
Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904
Posted: 01:51pm 25 Nov 2009
Copy link to clipboard
Print this post
Yes, and a ready made PM motor would be the one used in electric small boat propulsion, Minnkota I think is a common brand.
These have the propeller already in place, all that's required is to have a bracket of sorts to clamp it to the gunnel with the propeller facing forward to take the thrust load while being towed.
I have not tested this idea but think it has merit. There should be units around with a faulty controller but good underwater unit to try, maybe a dealership has some junked ones to offload.
If successful, this would be the easiest way to generate electricity via a towed propeller. Klaus
Notice. New forum software under development. It's going to miss a few functions and look a bit ugly for a while, but I'm working on it full time now as the old forum was too unstable. Couple days, all good. If you notice any issues, please contact me.
Print this post
