27' Owens Full Electric Conversion Feasibility

Not disagreeing with the numbers but fixed the units. I have a problem of getting annoyed when wrong units or terms like power, torque or energy are mixed . cheers

Besides that I think that the 12v LifePo units are probably not the most economical as the one you pointed out comes to 1.2kwh of storage /$1200.

In the link I provided bulk 'cells only' are ~$400/kwh and I think bit over $500/kwh gets you DIY packs with management system.

 

these are designs probably not common in the US but other can maybe pick ideas of similar boats stateside. Anyway the following are types of hull speed boats that very economical from around here (Finland):

Fiskari:
https://www.google.com/search?q=fis...n4ASJ1YGoBw&ved=0CAoQ_AUoAQ&biw=1389&bih=1047

or more broadly retkivene (translation would be 'trip boat' or 'camping boat' - doesn't exactly translate well)
https://www.google.com/search?q=fis...4,d.bGE&fp=a89aa29977b7a97b&biw=1389&bih=1047

 

What you would be looking for would be a small trawler. I don't have a lot of experience with these, but look for powerboats in the 30' range with no more than a 50hp engine. Trawler tugs would also come to mind.

It's going to be a hard search, since few boats are built for economy, but there may be some out there. I know Tad Roberts (he posts here) has designed some long range cruisers similar to what you are looking for, but I don't think they will be easy to find.

Alternatively you may want to consider looking at a sail assisted power boat. Like http://www.tadroberts.ca/services/new-design/power/northcoast34 from Tad. Even a small amount of power generated from sails could make a huge difference in range.


If I were building a test boat I would start with an old sailboat, and modify it. Assuming you could get everything to work, you could then move the entire power plant to a new hull. While working with a pretty disposable hull that could be acquired cheap (a few grand at most) and wouldn't hurt your feelings if you had to modify with a chain saw to get things to fit.

 

Kerosene,

The advantage of being a lawyer not an engineer... I typically don't have to run my own numbers. But thanks for the correction.

 

According to calculations made by a forum member (Rick Willoughby) in 2009 for my boat, 3 KW at the prop shaft is sufficient to obtain 6 knots. Waterline length and hull shape are very similar to the Owen 27. He presented his findings in graphs that were reasonably accurate for higher speeds because his predictions correlated with the actual fuel consumption.

Assuming his graph is also not far off in the low speed area, a storage battery of 20 KW would meet the OP's requirements. Such capacities are common in modern electric vehicles.

 

I love this forum! Tons of great and practical feedback. Have been busy contemplating this lately and thanks to your feedback I am considering seeking out a Vashon pocket trawler(I almost bought one last year) or perhaps the more plentiful Albin 25. I'm not exactly in love with the Albin design from an aesthetics standpoint but the hulls are more suitable to what I'm seeking to do. (Reminding myself that all boats are first and foremost compromises) Careful paint color selection can do wonders to accentuate a design.

A good friend of mine has communicated that the original engine in the Albin 25 was 22 HP. That seems like an extremely good of a fit for a project like mine.

CDK, may I ask what kind of boat do you have that is similar in design? 3 KW is far under the 15 KW I have been thinking would be needed for the Owens. 3 KW is also a real game changer for me while contemplating size of the battery bank. Is it too bold for me to ask to see the graph data if you still have it?

Stumble, I really like your idea too for a possible sail assist. I enjoy out of the box ideas if this thread hasn't proven that already. I've been researching kite assist a little and while fine downwind they don't seem too promising for my particular current application. I also like your sailboat donor hull idea for proof of concept and vetting out the electrics. Worn out sailboats are literally a dime a dozen in my area. I've had 2 given to me recently I kept the 12 footer and gave the 20' away 2 months ago to a friend.

Once again, I truly appreciate all of your great contributions.

 

Telein, the boat is a Norwegian Draco 2500 twincab with a home brew transom extension.
Here is the old thread with Rick Willoughby's contributions. He was kicked from the forum later because of an exchange of niceties in the "pedal powered boats" thread, so his posts are listed as "Guest xxxxx".

http://www.boatdesign.net/forums/boat-design/tunnel-drive-performance-issue-23715.html