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Old 01-19-2019, 08:25 AM   #41
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You might consider a boat that more resembles a European canal boat. While I would stay closer to the 3:1 ratio of length to beam, the hull should probably be full displacement with the batteries being your ballast. The other advantage of the European canal boat style would be a lot of cabin rooftop for solar panels.

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Old 01-19-2019, 08:32 AM   #42
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Thank you all for your opinion and knowledge, however, i am in research mod on this because i want to build one in the rang of 20 to 28 feet. Reason being is I've never seen one the way i want it so i have to build it. Having said that my boat will have features of three kinds of boats in one based on a trawler vs a cabin cruiser. Speed is good but sometimes over rated. I don't mine going slow if it means getting the job done. It will be a heavy boat for its size but if it will do the loop with ease im happy. A boat that size i don't think is good for ocean crossing. Thats ok the USA has lots to offer a boater so im not in a rush. Thank you all again for reading a dream of mine and allowing me to see through your eyes and minds.
Have you looked at all the production boats in that size range that might suit for electric propulsion?

Ranger (no relation ), Rosborough, C-Dory (?), probably 8-10 others?

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Old 01-19-2019, 08:42 AM   #43
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This guy turned a Compact 16 sailboat into an econo long range trawler. There was a company doing them but I can't find their pics or website.




Compac 16 Pilothouse Build


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Old 01-19-2019, 10:42 AM   #44
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This guy turned a Compact 16 sailboat into an econo long range trawler. There was a company doing them but I can't find their pics or website.




Compac 16 Pilothouse Build


Nice and very nice!
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Old 01-19-2019, 01:26 PM   #45
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How are you going to produce enough electric power to recharge the batteries that power two 15 hp motors (or even a fraction of that power) underway? The only way I know is with a big diesel genset.


A diesel genset that produces electric power that drives a couple of electric motors is less efficient than a diesel engine driving the props directly.


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Old 01-19-2019, 03:46 PM   #46
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How are you going to produce enough electric power to recharge the batteries that power two 15 hp motors (or even a fraction of that power) underway? The only way I know is with a big diesel genset.


A diesel genset that produces electric power that drives a couple of electric motors is less efficient than a diesel engine driving the props directly.


David
You may be right because land test will give different reading. However, one 12hp motor can do the work of a 40hp/cb engine. Having said that i always have a backup for even my back. You cant forget im experimenting so i don't have all the answers and worse case ill put an outboard on it and call it a day and still have the boat i want.
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Old 01-21-2019, 11:02 AM   #47
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I'm converting a 26' USCG motor whaleboat to a "trawler" using an 18hp diesel. At 8000 pounds it requires 11hp to attain hull speed. Most but not all full displacement hulls will use a bit less horsepower than a semi-displacement hull and are more efficient. As a long time commercial "trawlerman" I define a trawler different than some but it's just a name that's gotten bastardized over the years which is fine. I wouldn't really call my boat a trawler although it has some characteristics of one. In the UK and elsewhere there are lots of fishing trawlers that are as small as 20' and are correctly called trawlers because they tow a "trawl" behind the boat to catch various species of seafood. The name came from the type of net not the vessel towing it so really any boat towing a trawl net can rightfully be called a trawler.Click image for larger version

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Old 01-21-2019, 11:23 AM   #48
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Yes displacement hulls are almost always more efficient than semi-displacement hulls. A good rule of thumb is that it takes 1.5 hp per thousand pounds of displacement to push a displacement hull to it's hull speed. According to that rule, your boat will take 12 hp which is very close to your 11 hp value.


Pulling 11-12 hp continuously from a non turbocharged diesel rated at 18 hp should be no problem. You could even run it at wot occasionally when bucking a current or whatever with no harm.


But if you have any concerns about its hull type I would go bigger. My Cape Dory 28, weighing the same as yours pulled about 20 hp to get to hull speed. It was a semi-displacement downeaster hull which typically aren't very efficient.


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Old 01-21-2019, 11:41 AM   #49
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Yes displacement hulls are almost always more efficient than semi-displacement hulls. A good rule of thumb is that it takes 1.5 hp per thousand pounds of displacement to push a displacement hull to it's hull speed. According to that rule, your boat will take 12 hp which is very close to your 11 hp value.


Pulling 11-12 hp continuously from a non turbocharged diesel rated at 18 hp should be no problem. You could even run it at wot occasionally when bucking a current or whatever with no harm.


But if you have any concerns about its hull type I would go bigger. My Cape Dory 28, weighing the same as yours pulled about 20 hp to get to hull speed. It was a semi-displacement downeaster hull which typically aren't very efficient.


David
I have no reservations about my hull type, I used to own this boat twenty years ago when it had it's original Perkins 4-108 which was far too much horsepower but it's a very able boat for it's size. I've owned a number of lobster style boats a BHM 32, Sisu 26 and a Duffy 35, all used for fishing. I also used to have a Cape Dory 38 trawler and I have a Cape Dory 28 sailboat now along with my project boat. My goal is having a simple, economical boat that I can fish with and do some cruising. I've towed nets at 2.5 to 4kts for so many years 5 or 6kts is fine with me.
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Old 01-21-2019, 09:46 PM   #50
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You may be right because land test will give different reading. However, one 12hp motor can do the work of a 40hp/cb engine. Having said that i always have a backup for even my back. You cant forget im experimenting so i don't have all the answers and worse case ill put an outboard on it and call it a day and still have the boat i want.
Also, just so you know dave dirty fuel trains of today are in fact dirty fuel over electric and it is this combination which allows it to haul cars ranging miles long. Because electric motors have full torque at any range of power input. However, in my build i aime to break the rules in boat powering. Sail boats already have half the answers. So don't lose sleep because im not saying how im going to do it. I said i want to be the first and i will. Listen to what i was just told from someone who has run trawlers for year in a way of which make his living.
A trawler goes not need lots of hp and look at the the weight they come to sure with! There will always be a way to do something. Things have been built many years ago and yet today those who says things cant be done can't figure out how cities were built long ago without using what we use today to build with. Don't limit yourself to a box and forget about the rest of the world. The Ra is still out there running on one motor because one broke and the Ra is doing it all on solar power. So your skills knowledge and grit are your only limits. If your not being gang stalked of course and even then you can sill get things done with grit.

All along I've been giving clues about this build. This boat will kill me or help my life and am ok either way because ive done a great many things in my life that many cant say the same. At leat if this boat kills me i will have died doing doing what i wanted to do and happy doing it. That in itself is worth doing if for nothing else then to look at it and say damn i build this with my own hands. Again not many can say this and this is not my fist boat build but my first all electric. Thank you and have a nice day sir.
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Old 01-21-2019, 10:40 PM   #51
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My boat is a C-Dory 22. I (and anybody else I can think of) don't call it a trawler. However, we use it for some of the same things that others users of this site do with their boats. We also stay on it for (IMO) extended periods (up to 2 weeks).

Just because my boat is not a trawler doesn't mean that I can't learn things from this site.
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