Making a diesel electric trawler for coastal/loop

[valhalla360]

Originally Posted by KTP

A diesel engine is what, 40% efficient at best? So a gallon of diesel, with 40kwh of energy will only provide 16kwh to the prop through the engine (this is if the transmission is 100% efficient).

Running 1hp for an hour is 746 watt-hr. Thus a gallon of diesel can provide at best about 21 hp for one hour.

A 250hp engine then, running flat out is going to consume about 12 gallons of diesel an hour!

A 8 hour day of running like this and you consume 96 gallons of diesel.

Kind of eye opening. Fortunately, most people I guess don't actually run their 250hp engine at 250hp for any long length of time. Or they have very large tanks. I guess I have seen a trawler with a 800 gallon tank...

Assuming you are putting that 250hp output into say a 28' planing boat, it may use 96gal but it's also likely doing 160miles. If you are talking about displacement speeds, if you need 250hp, you are probably north of a 70' boat.

Assuming a typical displacement vessel using maybe 1/2gal per hour at 6mph, you need to run for 27hrs. You'll burn a lot less fuel but if you slow the 250hp boat down to similar speed, you won't burn anything close to 96 gal.

How about this for eye opening: We put in a bit over 7000miles doing the loop. At 3kts, that works out to 7hr run time 7 days a week every day 365 days to complete the loop in a year (remember it's a weather dependent trip as you have to be out of the north in the winter and have to be out of the south for hurricane season). That is assuming no mechanical breakdowns nor weather delays.

[valhalla360]

Monohull doesn't work well in your scenario.
- Monohulls often become unstable without the mast. The mast and the sails are critical to stability.
- With the mast installed, you seriously diminish the opportunity to install solar as shading will kill your output.

[a64pilot]

Drop the mast on a mono and it actually becomes super stable.
So stable that it’s rolling moment is very quick, add a mast and you greatly slow that moment down due to the length and inertia of the mast.

However just how much wave action is there on the ICW? I’m in it now and for most of it it seems more like river travel than anything, of course there are open parts, but they don’t seem to be that many of them.
I have never been on a mastless sailboat, but sure see a lot of them, so it can’t be all that bad.

[valhalla360]

Originally Posted by a64pilot

Drop the mast on a mono and it actually becomes super stable.
So stable that it’s rolling moment is very quick, add a mast and you greatly slow that moment down due to the length and inertia of the mast.

However just how much wave action is there on the ICW? I’m in it now and for most of it it seems more like river travel than anything, of course there are open parts, but they don’t seem to be that many of them.
I have never been on a mastless sailboat, but sure see a lot of them, so it can’t be all that bad.

No it's less stable. The keel may pull it back upright more readily as it doesn't have to pull the mast back up but it's less stable.

On the river system it's not too bad, though a 6' wake of a tow boat up river on the Mississippi gets your attention.

You do have to run large sections of the Great Lakes including the entire length of Lake Michigan, armpit of Florida, Chesapeake, offshore at New Jersey and lots of large bays. A big part of the issue is it doesn't take big waves to get a mast-less monohull rocking and rolling horribly. If the waves get in sync with the roll period of the boat, it can get bad. Even some of the bodies like Kentucky Lake can get 3-4' waves going on windy days and you are often confined to a narrow channel.

Most sailboats that run the loop have the mast up for the bulk of the open water sections, so the associated issues are less of a problem.

If you wait for good weather, it can be done but this goes back to my other comment about speed...if you are doing 3kts, you don't have time for weather delays, you need to put in 7hrs a day every day...or start doing some really long slogs to make up distance.

PS: that got me thinking, for most loopers, the armpit of florida (about 120miles Carabell to Cedar Key) is the only run that exceeds what can be done during daylight (and if you are shallow draft, there is a way around that). But at such slow speeds, some other runs push the limits of what can be done during daylight. The OP needs to review this independently as all the guides and online resources are going to assume a more reasonable cruising speed where a 50 mile between port/anchorages is easily doable:
- On the Mississippi, there is one run where you need to make 70 miles in a day. At 5mph + 2mph current, that's a long 10hr day. But at 3mph + 2mph current, that's a 14hr day. Doable if it's not too late in the season but a long stressful day.
- Clifton to Pickwick lake is only about 25mile but you are fighting a decent current most of the way. I have notes that we were netting 4.5mpg SOG with a STW of 6.0mph. If the OP is netting 1.5mph over ground, that's marginal to do in a day and there isn't much in the way of anchoring spots.
- The south end of the Tombigbee has some long stretches without anchoring spots.
- Mackinaw to Petosky is 50 miles.

[lensming]

KTP, here is someone who has done what you're talking about. Below is a copy of one of his posts on the AGLCA forum:

Just a bit different, a Totally Electric Powered Solar TEPStm boat.....

0. Air draft of 8 feet and water draft of 18 inches in a forty foot boat.
1. No diesel, actually no anything fossil fuelwise. Of course you can add a 225hp Yamaha or a hybrid system.
2. Just good old fashioned lead acid batteries. If you want to spend $$$ use some Li batteries.
3. Stern drives are not the way I feel money gets saved. But the boat does have two skegs and sits level on the beach.
4. I like electric outboard motors but works just as well using inboards. Electric is instant, quiet and very maneuverable.

So here is what I propose....

This is a Totally Electric Powered Solar (TEPS)tm boat. It is a 40 foot length MOG Canal Boat, a privately funded. completely solar electric prototype. It saves up power for rainy days in the battery banks. Power for the fridge, microwave and even the AC.

Some of the background info is available on the web and blog sites. After about 30 years
there is so much info, it is hard to keep track.

The previous two electric 10hp converted motors are shown here with a gasoline auxiliary
engine in the up (not running) position. The gasoline engine has now been removed.

https://www.youtube.com/watch?v=LI2n...ature=youtu.be

The MOG Canal Boat is shown here in its natural environment. The water at high tide is only about two feet deep when we get to the back side of the Atlantic Ocean beaches of North Carolina. Just a walk of a few hundred feet and we swim in the ocean. Our boat is a totally self sufficient condo 'on the beach'. We can stay as long as we want, then exit on the next high tide.
https://youtu.be/h92dWykE_Xo

Mog Canal Boat – Just another WordPress site

Mog Blog

We use it and have great fun (with no noise, smell or costs of fossil fuel), it seems the world is almost ready for such a craft. The time is coming for the TEPStm boat to be a truly sun bright, in vogue, affordable, traveling beach condo. It takes rough waters quite well because of its time proven Chesapeake & North Carolina skipjack, sharpie, garvey smack type hull forms.
One of our tasks is trying to warn and wave off other boats from following our 40 foot boat of 18 inch draft, into very shallow coastal estuaries and across sand bars. A top perk is the smile from the kayaker who gets a cold soda from our refrigerator. Kinda evens things out a little bit.

In the meantime, we solar-sail the boat in the east cost’s IntraCoastal Waterway (ICW), always creating a low key stir of disbelief and curiosity.?

Just thought the above items might broaden an already crowded decision horizon. At least you now know that something does exist out there that offers an alternative concept to the conventional selection. Good luck.

FREE FUEL (Sun), no Oil, no smell, minimal maint. with A/C on the ALGEMAC II a MOG Canal Boat. Totally Electric Powered (TEPS) Solar 40' boat, Wilm, NC at Cape Fear Marina-BBY, Mog Canal Boat – Just another WordPress site

http://s3.amazonaws.com/ClubExpressC...h_to_right.jpg

Good luck, and don't let the naysayers hold you back!

[skipmac]

Originally Posted by valhalla360

No it's less stable. The keel may pull it back upright more readily as it doesn't have to pull the mast back up but it's less stable.

A mastless sailboat will be more stable and less stable. Depends on what kind of stability you're thinking about.

Without a mast the center of gravity is lower so the boat will have increased resistance to rollover IE increased righting moment, so more stable in that regard. However the initial resistance to rolling will decrease dramatically without the damping effect of the mast making the boat less stable in that regard.

Fortunately have never been in this situation but have read a number of reports from sailboats that lost the mast and in all cases the motion on the boat got so bad that in really rough seas it was almost impossible to work on deck to clear the wreckage and seasoned hands suffered seasickness.

[KTP]

Originally Posted by boat_alexandra

Finally I realized that a sculling oar made of wood is far more efficient in many respects. I traded my solar panels, and batteries. I can maintain 1.5 knots for up to 3 miles. It keeps me warm when I need to break through ice.

there is nearly always some wind, despite what is claimed. I'm sure it's possible to make the great loop with sail alone.

Even if a sculling oar is 100% efficient (it probably is close to that) the human body can only put out about 100 watts sustained (Lance Armstrong was said to be able to pull off 200 watts sustained).

Thus just one 270 watt solar panel + about any electric motor would beat a sculling oar.

[Dockhead]

Originally Posted by skipmac

A mastless sailboat will be more stable and less stable. Depends on what kind of stability you're thinking about.

Without a mast the center of gravity is lower so the boat will have increased resistance to rollover IE increased righting moment, so more stable in that regard. However the initial resistance to rolling will decrease dramatically without the damping effect of the mast making the boat less stable in that regard.

Fortunately have never been in this situation but have read a number of reports from sailboats that lost the mast and in all cases the motion on the boat got so bad that in really rough seas it was almost impossible to work on deck to clear the wreckage and seasoned hands suffered seasickness.

If we're using the terms in their technical, naval architecture meaning, there is only one kind of stable, and a mastless sailboat is MORE stable -- CG is lower, righting moment is increased -- that is stability.

MOTION COMFORT is not stability. Motion comfort is reduced drastically without a mast because of the factors mentioned by Skipmac.


"The term vessel stability implies the tendency of a floating vessel to return to its original upright position of equilibrium after being tipped by the forces of wind and sea."

https://definitions.uslegal.com/v/vessel-stability/

[a64pilot]

So buy a boat with a bolt on keel with a stub keel and drop the keel, or a swing keel Boat.
It’s all answerable, and all doable, there are no breakthroughs or new designs needed, it’s just bolting on available parts, just takes time, money and the desire to do it.
It will work, just not as well as a Diesel boat.

[john61ct]

"It will work"

IMO only in a very limited set of conditions, which most people would consider unrealistic.

Aside from the crazy expense for such lower functionality.

[skipmac]

Originally Posted by Dockhead

If we're using the terms in their technical, naval architecture meaning, there is only one kind of stable, and a mastless sailboat is MORE stable -- CG is lower, righting moment is increased -- that is stability.

MOTION COMFORT is not stability. Motion comfort is reduced drastically without a mast because of the factors mentioned by Skipmac.


"The term vessel stability implies the tendency of a floating vessel to return to its original upright position of equilibrium after being tipped by the forces of wind and sea."

https://definitions.uslegal.com/v/vessel-stability/

Thanks for clarifying the technical definition of stability in the nautical context. The word obviously has a number of definitions in a general sense which obviously creates confusion.

To confuse things further in structural engineering there is also a technical definition of stability.

[Colin A]

I have some data from a project I know about. 36' trawler around 20,000 lbs displacement electric drive was 3 knots was a 2.7KW draw. 3.5 knots was 3.8 KW. I think this one (which was a proof of concept) topped out just under 5 knots at 7KW draw. Now this was not the most efficient hull design so this could be improved but it shows where your at. The answer is yes you can do it but the battery bank and solar required my not make it the most practical.

Also you can read alot about efficiency of propulsion in back issues of proboat in a series written By Calder.
I don't remember all the issues but I know issue # 148 and 145 and a few others from the time period go into his testing results.
Professional BoatBuilder Back Issue Archive
Basically because a propulsion load is so consistent on a boat the diesel usually came out on top over diesel electric with the exception of being able to quick charge from a large solar array or shore side power.

[seandepagnier]

Originally Posted by KTP

Even if a sculling oar is 100% efficient (it probably is close to that)

It's about 80-85% efficient.

the human body can only put out about 100 watts sustained (Lance Armstrong was said to be able to pull off 200 watts sustained).

Thus just one 270 watt solar panel + about any electric motor would beat a sculling oar.

This is wrong for a number of reasons, I tried this.

1) 270 watt solar very rarely outputs 270 watts. You are lucky to get 200 watts, provided you can get it in full sun without any shade.

2) "about any electric motor" !!!

You should research this before you convert anything to electric. Typical trolling motors like what I used are around 20% efficient. The brushed motor itself may be 70% efficient, but the tiny propellor it spins spoils it. For this reason, I get the same speed with the sculling oar, as 250-300 watts of power. The sculling oar is 6ft long, and moves a lot of water slowly.

More efficient motors use a larger propeller turning slower. Some brushless motors geared down running the propeller below 500rpm can get nearly 50% efficiency. If you had an exceptionally large propeller, nearly the width of the boat, or better, two counter rotating propellers, you might get up near 80% efficiency. For a trawler, this means two propellers 4ft in diameter, but your draft probably limits this somewhat. If you got 60% efficiency it would be exceptional.

Consider most cargo ships, the propeller diameter is limited by draft, and some new supertankers now have dual propellers just as I outlined above.

People think they can replace an inboard with electric and get good efficiency, but they fail to realize that the drive system in most boats is terribly inefficient, compensated for by having a large engine and burning more fuel which has incredible energy, but it's wasteful.

Trawlers are awful designs for so many reasons, we should recycle them. You are better off getting a trimaran that can sail efficiently in light wind. Keep it light. Now you will make the great loop much faster without any propellers than you could on a "solar trawler"

At this point, if you want to add solar propulsion, you have a lot of deck area, and you can use panels that you can stand on. The trimaran is also very efficient to push with motors, and you can drop large diameter propellers between the hulls for efficiency, but pull them up when sailing.

[KTP]

I used an older Torqueedo 1003 on our 17 foot sailboat (about 2500 pounds displacement loaded with 2 of us in it). This is a geared down brushless motor turning a fairly large prop. It had a 300 watt-hr battery.

I could get 2 hours or so of run time doing about 3 to 3.5 knots.

This is why I was saying even a small solar system could beat a sculling oar. My personal experience. Maybe not "any" electric motor/drive, but something like that Torqueedo system.

[mako]

Originally Posted by Dockhead

If you buy a trawler with a broken 200 hp engine, you are not going to be either safe or happy with 20hp. You might not need 200 hp if you are willing to live with a lower top speed, but you need to have enough power to get out of tough situation (for example, get off a lee shore), which will sooner or later arise.

Good point but a displacement cruiser is comfortable at 3 hp per long ton. Even as low as 2 if operational speed is low like V/L=1.0