Re: [electricboats] Time to re-power

The answer to your question is yes, If l can move my very inefficient and heavy boat with a small generator then you can do even better with a sail boat. I crossed the Gulf of Mexico from Carrabelle to the Tampa area on a very foggy two and a half days.  120nm trip,  the trip was completely under electric motors.  As there was no sun for most of the trip I did run a 3000 watt generator to keep the batteries full. I was being pretty cowardly given it was my first large open water trip, so averaged 2.5 knots. I probably could have probably done 3 or 3.5 knots and arrived with half empty batteries.  If there had been more sun I probably would have been bolder, the Fog made me extra paranoid.  The next over night trip I do I'll push the boat a little harder and see if I can average above 3 knots. 

http://www.deny.org/Escape_the_American_Dream/Work_Blog/Entries/2020/1/18_Open_Water%2C_in_the_fog..html

On May 22, 2020, at 6:02 PM, Lee Chrystal <lee@marshspecialtyhvac.com> wrote:



Thank you Eric!

So for small displacement boats like my Balboa 27 ft swing keel,4900 lbs disp, 23 ft on waterline 8 ft beam, 13RH11 prop i guess regen is not going to happen except in some marketing ploy. Shattering news but now accepted!

 

This brings me to my new issue, What size, brand of small generator will keep me moving at 3 kts, or is that also unlikely/impossible. Seems as I have the space now without the Yanmar.

 

I will supplement with solar but space is quite limited and when I am not sailing in the gulf of Thailand it sometimes just wont shine!

I was all gung ho, I ripped out the Yanmar package and now cannot seem to get this moving forward with any confidence.

 

I believe the gent at Thunderstruck said I should get about 60 miles, with their 5KW-48 V system at about 3 kts. Hopefully that's accurate,

Let me know your opinions on that statement please.

 

Normally 60 miles is surely enough, It's a sailboat but I want to go around Vancouver Island next summer and feel 60 might not be sufficient in a dilemma. Dismasted or other distress situations for example.

 

How many watts to generate enough power to just keep moving forward using the Thunderstruck 5KW in a o-crap situation albeit slowly? In reasonable sea states at least. Should a 2200 watt gen keep me moving at about 2.5-3 Kts?

 

I don't mention an outboard and I will have a small one also but I have been on many small sailboats when its prop was just not underwater ½ the time.

Any advice is appreciated.

Thanks.

Lee Chrystal

Marsh Specialty HVAC LTD

Box 5061 STN Main

Leduc Alberta T9E-6L5

Cell: (780) 975-6801

 

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From: electricboats@groups.io <electricboats@groups.io> On Behalf Of Eric via groups.io
Sent: May 22, 2020 2:56 PM
To: electricboats@groups.io
Subject: Re: [electricboats] Time to re-power

 

And you asked about regen.  Here's something that I wrote back in 2011:

"Regen is a funny thing.  I have yet to hear any substantiated report of anyone hydro-generating more than 100W at 6 knots.  That's including regular cruising sailors with towed systems.   It's really a limitation of physics.  If you can sail consistantly at speeds greater than about 8kts (large racing monohulls, big catamarans, etc.) then regen becomes a reasonable power source.  But for boats like mine, under the best of conditions, regen might suffice to replenish house loads, or maybe not.  Regen will not put any significant charge into a traction battery bank on passages of less than a week.  It just that at 6kts, we're at the really flat part of the logorithmic power curve.   As it is, I have seen peak regen of around 1.4A (70W) while sailing around 6kts but the 5 minute average was probably closer to .7A (35W).   So any regen power that I get is just a gift, certainly nothing that I would count on.  If I wanted to optimize my regen, I believe that a towed log is most effective, but that would still not generate any significant power at the limited speed of my 30' ketch."  

These limitations still appear to be true, even with the dedicated, $10k, technologically advanced, Watt & Sea hydrogenerators.  If they can't generate 100W at 6kts with a specialized and optimized hydrogenration system, the power collected by for your re-purposed drive system will be less.

Fair winds and following seas,
Eric
1964 Cheoy Lee Bermuda 30, 5.5kW drive, 8kWh LiFePO4 battery bank
Marina del Rey, Ca