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SailingJackson 01-25-2013 08:37 PM

Towed Generator that We Really Need
 
Similar recent thread talks much about trying to hack a trolling motor into a hydrogenerator. Reviewing that thread, it's clear that there are a lot of creative and resourcful people with interesting ideas. It's also clear that most of them don't understand the fluid dynamics involved and few of the ideas would have a chance of working.

Trolling motors are cheap things designed for lightweight use, running fishing boats around at slow speed. On the other hand the Torqeedo Electric Outboard is a much more powerful device and better designed for exposure in the marine environment.

Having been a product design engineer for 30 years, doing both mechanical and electrical design, I am highly suspect about the success of a hacked system. On the other hand, it certainly seems to me that the smart guys who designed Torqeedo could develop a similar version that could clamp on the transom as a hydrogenerator, with it's power electronics doing a controlled system charge. The same device could then be unclamped from the transom, clamped onto your dinghy. A quick prop change (yes towing is different than motoring), add the battery pack, and your ready to zip around the harbor. This seems a realistic goal for a product. It might cost 50% more than a regular Torqeedo, perhaps even twice. Even if it cost as much as a Watt & Sea generator, the Watt & Sea is only a generator. An outboard/generator would serve dual purpose for a typical cruiser.

Marine Industry: Are you listening?

G.J.

bobmcgov 01-26-2013 01:39 PM

Re: Towed Generator that We Really Need
 
I am onboard with this idea, GJ. Really. My only immediate critique would be the Torqueedo runs at higher RPM than most trollers, IIRC. That's one way it gets its HP boost. You need an alternator optimized for low speed output for most hydrogenerators to work. Not sure where a Torqueedo is on its power curve at 400 RPM.

But otherwise, I think the basic electric outboard/hydro-gen idea is feasible, whether hacked or purpose-built. Would to see the output of a basic troller in gen mode -- might be as high as 4A, even with the standard prop. But purpose-built could be better. You'd need to sell a few thousand a year to pay for development, tho. On a related tangent, a bunch of us brainstormed the possibility of decentralizing power distribution on sailboats. Instead of the current design -- big 12VDC battery bank, single breaker panel, fat wires run everywhere -- a system using a single 'spinal cord' down the center of the boat, or several smaller batteries (probably LiIon) was discussed. Also, higher DC voltages. Your Torqueedo battery could plug into a socket in the forepeak, to run a windlass or bow-thruster. It recharges via smaller diameter wires. When you need the dink, you un-dock the battery, plug it into your outboard, and off you go.

Stumble 01-26-2013 06:30 PM

Re: Towed Generator that We Really Need
 
The problem with this type of combined system is that it would entail pretty significant compromises as either an outboard or a towed generator, or both. And frankly both systems independently are only moderately successful. Towed generators create a lot of drag and reduce speed significantly on cruising boats already, ough they do provide a lot of power when working. And electric outboards... Well the best I have heard an owner say about one was "meh" they work but aren't stellar performers.

I am afraid you would wind up with a system that is the same price as the two combined, but didn't perform half as well as the other options.



Bob,

On the distributed power... There are, and have been systems that do that on the market for years. The problem is it really takes a full rewire to justify it as a refit, and builders are slow adopters.

bobmcgov 01-26-2013 07:31 PM

Re: Towed Generator that We Really Need
 
Quote:

Originally Posted by Stumble (Post 981542)
The problem with this type of combined system is that it would entail pretty significant compromises as either an outboard or a towed generator, or both. And frankly both systems independently are only moderately successful. Towed generators create a lot of drag and reduce speed significantly on cruising boats already, ough they do provide a lot of power when working. And electric outboards... Well the best I have heard an owner say about one was "meh" they work but aren't stellar performers.

I am afraid you would wind up with a system that is the same price as the two combined, but didn't perform half as well as the other options.



Bob,

On the distributed power... There are, and have been systems that do that on the market for years. The problem is it really takes a full rewire to justify it as a refit, and builders are slow adopters.

Correct on both points, Greg. Tho people will continue looking for alternatives to the gasoline outboard as long as those keep letting people down so often.;)

Some European custom builders are using more sensible wiring architecture -- not least because copper has gotten so bloody expensive. You can't be running 60' of 2/0 hither and yon. And some bow thrusters are already working off their own dedicated battery. It is a good solution for high-amp loads used in short bursts, with plenty recharge time in between. Like a windlass, or a thruster. If you only need an outboard to run your dink to and from shore -- versus exploring up river, or visiting dive sites two coves away -- an electric outboard is an okay solution. (But then, so is a pair of oars....) In which case, having a spare battery pack is handy. In which case, why not double its utility as the windlass batt?

Right now, I'd faint with gratitude if the industry would finally admit 12V is a stupid idea and upgrade to 24 or 36V. I'm told 48V starts getting too close to lethal for boat use, but sheesh. Who is gonna move first -- manufacturers? Electronics makers? Alternator builders? Europe is again ahead of the US here, but wiring boats to 12V is as dumb as wiring tractors to 6V was. We WILL be completely rewiring our boat, but too many systems are still clinging to 12V for us to mess with converters. Unless something changes radically in the next 2 years, we are stuck rewiring to 12V.:(

ebs001 01-27-2013 02:13 AM

Re: Towed Generator that We Really Need
 
Bob, you make a good point. There are a number of items available now in 24 volts, some electronics lighting and wind generators to name some but as to a complete switchover that will be a long time coming if ever. The whole auto industry, RV industry and almost any other commodity using DC power are all geared to 12 volt.
It is feasable to use a hyrid 12v/24v system wiring some things 12 and others 24 off the same battery bank.

Stumble 01-27-2013 02:15 AM

Re: Towed Generator that We Really Need
 
If you really planned it out from the ground up, I would be willing to bet you could go all 24v, or very close to it right now. It may take some creative options when it comes to equipment, but a lot of things that used to be 12V only are starting to show up in 24.

Trying to go to 48v right now would probably be close to impossible unless you were willing to take major restrictions on parts options.

JonEisberg 01-27-2013 08:06 AM

Re: Towed Generator that We Really Need
 
Quote:

Originally Posted by Stumble (Post 981542)
The problem with this type of combined system is that it would entail pretty significant compromises as either an outboard or a towed generator, or both. And frankly both systems independently are only moderately successful. Towed generators create a lot of drag and reduce speed significantly on cruising boats already, ough they do provide a lot of power when working. And electric outboards... Well the best I have heard an owner say about one was "meh" they work but aren't stellar performers.

I am afraid you would wind up with a system that is the same price as the two combined, but didn't perform half as well as the other options.

I think the issue of drag with a towed generator is often overstated, it certainly hasn't been significant for me, and I sail a boat only 25 feet on the waterline... On a larger boat of 40' or so, loaded for cruising, I would expect it would be barely noticeable in the bigger picture...

It's certainly an intriguing idea, but the main problem as I see it, is that the potential market for such a system is likely to be pitifully small... Two of the most notable trends I'm seeing these days, are the proliferation of portable Honda generators, and ever-larger SUV dinghies powered by 15-25 HP engines... I don't think I've EVER seen a Torqueedo in a place like the Bahamas, for example - they simply won't satisfy the demand that many of today's cruisers have to go far, and fast, in their tenders...

The only way for such a hybrid system to make sense, is when used in conjunction with a minimalist approach to energy consumption on board... Unfortunately, the modern trends are quite the opposite, with today's boats being fitted out with a wide array of power-hungry gear - bow thrusters, electric winches, full-time use of laptops for navigation, and so on...

And, bottom line, many people also spend a considerable amount of their time underway, under power, anyway... A LOT of people simply don't routinely use their boats in a way that really justifies such a system, seems to me...

http://i268.photobucket.com/albums/j.../SUVdinghy.jpg

dacap06 01-27-2013 08:20 AM

Re: Towed Generator that We Really Need
 
Quote:

Originally Posted by Stumble (Post 981684)
If you really planned it out from the ground up, I would be willing to bet you could go all 24v, or very close to it right now. It may take some creative options when it comes to equipment, but a lot of things that used to be 12V only are starting to show up in 24.

Trying to go to 48v right now would probably be close to impossible unless you were willing to take major restrictions on parts options.

Weren't a lot of power boats from the '60s wired for 24 volts?

Anyway, count me in with Greg. Adding point voltage regulators for things like your LED lights should cost next to nothing. 12v regulation can be had on a single chip!

Tom

bobmcgov 01-27-2013 01:51 PM

Re: Towed Generator that We Really Need
 
Quote:

Originally Posted by JonEisberg (Post 981720)
I think the issue of drag with a towed generator is often overstated, it certainly hasn't been significant for me, and I sail a boat only 25 feet on the waterline... On a larger boat of 40' or so, loaded for cruising, I would expect it would be barely noticeable in the bigger picture...

It's certainly an intriguing idea, but the main problem as I see it, is that the potential market for such a system is likely to be pitifully small... Two of the most notable trends I'm seeing these days, are the proliferation of portable Honda generators, and ever-larger SUV dinghies powered by 15-25 HP engines... I don't think I've EVER seen a Torqueedo in a place like the Bahamas, for example - they simply won't satisfy the demand that many of today's cruisers have to go far, and fast, in their tenders...

The only way for such a hybrid system to make sense, is when used in conjunction with a minimalist approach to energy consumption on board... Unfortunately, the modern trends are quite the opposite, with today's boats being fitted out with a wide array of power-hungry gear - bow thrusters, electric winches, full-time use of laptops for navigation, and so on...

And, bottom line, many people also spend a considerable amount of their time underway, under power, anyway... A LOT of people simply don't routinely use their boats in a way that really justifies such a system, seems to me...

http://i268.photobucket.com/albums/j.../SUVdinghy.jpg

Good points all, Jon. With the average cruising boat moving north of 40', the popularity of RIBs and high-pressure dinks (which can take 15hp outboards, so why not buy one?), nearly ubiquitous refrigeration, two hot showers a day, etc.... There's no demand for 'elegant' or 'clever.' Brute force suffices -- it solves nearly all problems. Or rather, it creates its own set of problems but those are broadly within the scope of the owner's competence.

Running the engine/genset two hours a day requires big tanks; s'okay, we got a big boat. Heavy electric use requires big batteries; see above. Or shore power -- we like marinas. Gasoline gennies need fuel; we have a thirsty gasoline outboard, so we carry 30 gallons anyhow. Easy. Running the engine to charge batteries shortens its life; but as you note, the majority of sailors motor rather than sail the majority of the time anyhow, so the electrical loads are not a determining factor in engine life. *shrug* It's how we live today. Not judging anyone's choices.

We, OTOH, just bought a small 30'er. Very small, compared to today's boats. Our refit budget is limited, stowage and tankage space is very hard to find, the engine is forty years old, and we chose this boat for its sailing qualities. Also, we expect to cruise in places where gasoline, diesel, water, and provisions may be hard to come by. Unlike, for instance, the Exumas -- where you can get anything, if your chequebook is large enuf.:p

So for us, elegance and cleverness still rate. We need gear that serves many functions. We need to minimize power and water consumption. The engine must be babied. And because we intend to sail the boat rather than motor, we need to take care that 'improvements' don't hinder its sailing ability -- hats, rather than full bimini. If we could finagle a hydro-gen/electric outboard combo, that would really work for our intended lifestyle. It would be a hugely attractive package. But such an item would not be easy to engineer, nor cheap.

(One advantage we have -- if you want to call it such -- is we live off the electric grid in the wilds of Wyoming. We drink rainwater and can deal with solitude and isolation. It's very hard for people coming from cities or suburbs to transition to a low-stimulation, minimalist lifestyle. Tho Chicky is going to want her some Internets, for sure.;))

hellosailor 01-27-2013 02:57 PM

Re: Towed Generator that We Really Need
 
All of these things (motors, generators) require a shaft seal to keep water from entering the assembly as the shaft rotates. And shaft seals are typically something like a heavy graphite or other polished ring, pressing against a felt or similar seal. I'd be concerned that the seal in whatever unit you are adapting is designed to seal against thrust, rather than drag, so it is designed to seal with pressure "this way" not "that way". And then it is going to break down and leak in much shorter order, if it is being pushed the opposite way to what it was designed for.

But as long as whatever you are using seems to have a seal that will still work properly, th eonly other question should be figuring out how to efficiently prop it.


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