Monday, February 29, 2016

Re: [Electric Boats] Re: Efficiency

 

Oh! And that reminds me. Anyone fitted a continuously variable transmission (CVT) (also known as a single-speed transmission, stepless transmission, variable pulley transmission, yet? Or indeed controllable (not variable) pitch prop? Hook it up to a NEMA 2000 and torque control function in the controller - could be interesting?

Personally beyond my pay grade or requirement but it does make me wonder where EP is going next. Which also makes me think we need the cost of Lithium/kWh to come down. Maybe some companies could offer lease or finance for them, as they are certainly cost effective over time even at today's capital cost compared to AGM.

Enough of my musings, today is Monday and work to be done to keep my boat afloat!

John R.

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Sunday, February 28, 2016

Re: [Electric Boats] Re: Efficiency

 

Well worded James. At least you understand why I went direct drive. The compromises of physics. I have to say at low power the serial efficiency equation; once one actually runs the numbers from known efficiencys based on measurement begin to show the differential in actual Ah consumed and you can quantify the costs involved. I have to say in my case 2 X 12.8 V nominal batteries or 12V as they were in the beginning means less overall system weight and cost, one of my project goals. Having said that once folk start to hit around 1kW continuous cruise, it is time in my view to go geared.

And whilst on that subject and even though I'm a DIY'er and not an Electroprop customer you can save yourself a lot of grief and money by buying James'es book.

http://electroprop.com/the-electric-boat-book/

It's the distillation of a lot of hard earned knowledge. Whilst that info was free in the earlier days, it is now a negligible cost for great information and by reading it you'll save James and Mike and other professional vendors a lot of their valuable commercial time. Many thanks though for such people taking their valuable time to help us folk on this list.

Long live EP evangelists!

John R.

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Re: [Electric Boats] Re: Efficiency

 

When a motor runs on current it gets hot.   Fans need to be strategically mounted and ducted to be effective.   Ambient temperature can be changed by introducing air from another part of the boat.   Ducting is necessary to draw air out of the inside of the motor.   Motors have omnidirectional fans which  by their nature a compromise.   Accentuating the cooling system increases power and efficiency.   Electroprops have incredible cooling systems with fan(s), ducting, and some with radiators and pumps.    

To make power you need to make high RPM.   To make efficiency you ned to make low propeller RPM, hence the need for reduction.     Without reduction the motor needs to be significantly oversized for the application, but it can be done.   Up to 48 volts is a bargain.   Going to 72 volts adds thousands of dollars but at higher power levels is desirable for simplicity.    

James Lambden
Electroprop
6 Harbor Way #226
Santa Barbara, CA
93109


On Feb 28, 2016, at 3:24 PM, William Grace jwsys@iconz.Co.Nz [electricboats] <electricboats@yahoogroups.com> wrote:

 

It is easy enough to fabricate and install an additional small fan to provide cooling air to a slow turning motor generating high torque. Probably cheaper than a reduction gearbox; certainly easier. Computer cooling fans use negligible power and may be adequate.

Cheers

Bill Grace
Wellington
New Zealand.

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[Electric Boats] Re: Efficiency

 

It is easy enough to fabricate and install an additional small fan to provide cooling air to a slow turning motor generating high torque. Probably cheaper than a reduction gearbox; certainly easier. Computer cooling fans use negligible power and may be adequate.

Cheers

Bill Grace
Wellington
New Zealand.

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[Electric Boats] Re: Partial Sea Trial, E/V Mr. Wiggles

 

Cal,

Well, as I say I've made a few changes so won't know for sure till back in the water in a month or so.

John R.

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[Electric Boats] Re: Partial Sea Trial, E/V Mr. Wiggles

 

wow are you sure about those numbers? Thats less than half what I spend to make 4kt!

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[Electric Boats] Re: Partial Sea Trial, E/V Mr. Wiggles

 

Cal,

Funny that. I actually wondered if it was a sailboat turned motorboat. Not sure if your displacement is as built or laden or LWL, but anyhow mine is about 8,000 lbs laden, 21.25 ft LWL and uses around 800 Watts at 4 knots. I want to check that again though as monitoring upgraded and switched back from the 3 blade I was messing with which used around a 1,000 Watts to my old 2 blade. Also a different rpm/volt and torque/amp motor - so I'm looking forward to testing again this year.

Like you I started simple as little cash but over the last 3 years have managed upgrades. Great fun being a modular type build. Beats faffing with diesels!

Enjoy...

John R.

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Re: [Electric Boats] Re: Efficiency

 

I should have added at a price I can afford.

Richard


------ Original message------

From: Carter Quillen twowheelinguy@yahoo...

Date: Sun, Feb 28, 2016 2:06 PM

To: electricboats@yahoogroups.com;

Subject:Re: [Electric Boats] Re: Efficiency


 

You've lived long enough to see it. All day electric boat travel has been around for a while now and numerous people besides me have been doing it. 

Capt. Carter 
On Saturday, February 27, 2016 6:10 PM, "fullkeel2000@yahoo.ca fullkeel2000@yahoo.ca [electricboats]" > wrote:




All the good ideas may have been tried but new ideas will keep coming. I am propably too old to see it but all day electric travel with our boats with Battery and solar are coming. The rate of progress is exponential.
Look what Tesla has done for cars in just a few years


------ Original message------
From: king_of_neworleans
Date: Sat, Feb 27, 2016 3:25 PM
Subject:[Electric Boats] Re: Efficiency

 
I'm no engineer but I agree. with commonly available motors, higher voltage and lower current, higher motor speeds and a reduction gear turning a larger prop, are going to be noticeably more efficient in spite of modest mechanical losses in the gearing. Going 24v rather than 48 does not allow use of half as big a bank. To get the same work done with half the voltage, requires twice the current and equal capacity. So comparing a 48v system with 4 12v batts in series with a 24v system with 12v batteries, they must be twice as big or be in parallel/series. Still need the same total v/ah to get the same work done, more or less. Cost of the reduction gear installation is almost trivial. You can homebrew a belt drive system with parts from McMaster Carr for probably $300. Salvaged junk, even cheaper. Small reduction gearboxes are cheap enough. Mine cost about $450 and is sealed, no maintenance and no additional parts needed and actually simplified installation because I did not have to fabricate anything for mounting a thrust bearing. That is not to say that direct drive doesnt work or doesnt have its place, becasue a motor can certainly be built that will work better in a direct drive system than what most of us are now using. I am thinking axial flow BLDC with about 4x the typical poles, large-ish diameter rotor and stator, and integral thrust bearing. Would this be significantly more efficient? Maybe, but maybe not. If there is one thing I have learned in putting my system together, it is that there is no free lunch. And all the great ideas have already been tried.




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[Electric Boats] Re: Partial Sea Trial, E/V Mr. Wiggles

 

Yes, it is a motorboat now. Used to be a sailboat. I use a lot of power to go fast. I use a little power to go slow. Not sure but I think my power expendiure is reasonable for the size boat.

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RE: [Electric Boats] Foiling electric catamaran

 

This page should give some ideas:

http://www.human-powered-hydrofoils.com/hydrofoils/

It seems that a high performance model airplane motor driving the right prop and with minimal battery, electronics and flexible solar onboard could yield an impressive speeds for at least short ranges.  Hydrofoil speeds exceeded 70mph even at the beginning of the 20th century: http://www.human-powered-hydrofoils.com/history/ .  Human power hydrofoils are impressively fast with the world speed record set in 1991 by Mark Drela of MIT at 18.5knots over a 100 meter course.

http://www.foils.org/linksout.htm

 

Delft University team has already built a solar hydrofoil that simply kicks…

https://www.youtube.com/watch?v=Uigdqj94pZ8

Here's a link which notes 30knots on solar:

http://gizmodo.com/393139/worlds-first-solar-speedboat-does-30-knots-gas-free

 

Wonder how soon we'll see a solar-electric racer win the Wye-Island race?

 

-MT

 

From: electricboats@yahoogroups.com [mailto:electricboats@yahoogroups.com] On Behalf Of downintheblue
Sent: Sunday, February 28, 2016 1:56 AM
To: electricboats@yahoogroups.com
Subject: [Electric Boats] Foiling electric catamaran

 

 

Is it possible to make a foiling catamaran, 100% electric? Going 40 knots in sprints if required?

 

Only a generator as absolute last resort emergency, otherwise have the entire hull plastered in the most efficient solar panels, should be possible with 20-25 kW peak on a 50' cat.

 

And plenty of batteries.

 

I am just thinking, as soon as you are planing on the foils, the drag goes down. You can choose a shorter but faster run while planing, or keeping it slow for long range, even infinite, cruise.

 

I am thinking something like this one, but with electric engines:

 

MV 1060 :: Q-West

MV 1060 :: Q-West

Q-West Boat Builders Ltd aspire to be New Zealand's pre-eminent boat builder, crafting all manner of pleasure craft, catamarans, fishing and charter craft,...

Preview by Yahoo

 

2 x 250 kW electric, 100 kWh battery, 25 kW peak solar panels?

 

Sure batteries are expensive, but the price is coming down. And consider all the items you DON'T need for cooling systems and other diesel expenses - put it into batteries and solar panels instead. 7000 liters fuel tank, that's about 5 tons when full of diesel. For that equivalent weight, you could have 500 kWh hours of Tesla style batteries. Even 10X more if using a better (but 4x as expensive) battery type. And the electric motors would also weight a lot LESS than equivalent diesels.

 

Thoughts?

 

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Re: [Electric Boats] Re: Efficiency

 

You've lived long enough to see it. All day electric boat travel has been around for a while now and numerous people besides me have been doing it. 

Capt. Carter 
www.shipofimagination.com

On Saturday, February 27, 2016 6:10 PM, "fullkeel2000@yahoo.ca fullkeel2000@yahoo.ca [electricboats]" <electricboats@yahoogroups.com> wrote:




All the good ideas may have been tried but new ideas will keep coming. I am propably too old to see it but all day electric travel with our boats with Battery and solar are coming. The rate of progress is exponential.
Look what Tesla has done for cars in just a few years


------ Original message------
From: king_of_neworleans
Date: Sat, Feb 27, 2016 3:25 PM
Subject:[Electric Boats] Re: Efficiency

 
I'm no engineer but I agree. with commonly available motors, higher voltage and lower current, higher motor speeds and a reduction gear turning a larger prop, are going to be noticeably more efficient in spite of modest mechanical losses in the gearing. Going 24v rather than 48 does not allow use of half as big a bank. To get the same work done with half the voltage, requires twice the current and equal capacity. So comparing a 48v system with 4 12v batts in series with a 24v system with 12v batteries, they must be twice as big or be in parallel/series. Still need the same total v/ah to get the same work done, more or less. Cost of the reduction gear installation is almost trivial. You can homebrew a belt drive system with parts from McMaster Carr for probably $300. Salvaged junk, even cheaper. Small reduction gearboxes are cheap enough. Mine cost about $450 and is sealed, no maintenance and no additional parts needed and actually simplified installation because I did not have to fabricate anything for mounting a thrust bearing. That is not to say that direct drive doesnt work or doesnt have its place, becasue a motor can certainly be built that will work better in a direct drive system than what most of us are now using. I am thinking axial flow BLDC with about 4x the typical poles, large-ish diameter rotor and stator, and integral thrust bearing. Would this be significantly more efficient? Maybe, but maybe not. If there is one thing I have learned in putting my system together, it is that there is no free lunch. And all the great ideas have already been tried.




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[Electric Boats] Re: Partial Sea Trial, E/V Mr. Wiggles

 

Cal,

Seems like a lot of power you are using. Is this a motor boat you have?

John R

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[Electric Boats] Re: Efficiency

 

Hi Bruce,

Not sure who you are addressing. Are you asking me? If so the choice is yours in my proposition.

John R.

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