Using the TT35 as a solar-electric trawler

[Blissboat]

Performance graphs that I have seen indicate that power catamarans operating at "displacement" speeds, i.e., 7.5 to 8 knots, also make efficient use of energy. Confess that I lack data to support that, but it has been my anecdotal experience.

 

[twistedtree]

Hi TwistedTree. I found your quote below on another thread.





Yes, I agree. This is an excellent analysis. The best I have ever seen. And this is why electric is not the future for trawlers. However, one thing has changed since you wrote this, the cost of LiFePO4 batteries.

The sixteen 280Ah cells I purchased cost me $1720 including shipping and customs from china. Add another $1000 for a bms, fuse, contactors, bus bars and extra thermal sensors. And that is for the good stuff (Orion and Blue Seas). This comes to $2720 for 14.5 KWh (I used 52 volts average instead of 48 volts nominal) or $187.50 per KWh instead of the $500 per kWhr as you calculated.

So if you are willing to DIY, (which I think results in a better battery with better components and an expanded knowledge of what happened when things go wrong), you can do it for 1/3 the price.

Still expensive though (and it doesn't change the weight, room, range and fill up time factors, all important points as you mentioned above), but cheap enough to get it to fit within my budget.


__________________

I totally agree about the cost, and it's a key part in expanding use of LFP (LIP in your terms) batteries. I just missed a big price reduction on the batteries I bought, so I'm painfully aware of the dropping costs.


But there remains the "size of the tank" limitation, which will constrain applications. Your "tank" gives you a range of 120 miles, which is very, very small compared to a diesel powered boat. But it's workable for a lot of cruising like marina hopping from here to there. But LFP will never replace the capability of a 500 or 1000 gal diesel tank.


Were I think LF really shines today is for house bank applications. It works soooo much better than lead acid for a boat that anchors out, and that's worth a premium. And the cost difference between LFP and lead acid continues to close, even ignoring the significant difference in cycle life.

 

[Scott Harris]

It is hard to for me to wrap my mind around the amount of energy stored in a 1000 gallon diesel tank. I imagine with the right type of boat you could travel between Seattle and Juneau without stopping once. I am trying to make that trip on 120KWh, stopping at every power pedestal along the way.

 

[Scott Harris]

Which type of hull performs best in rough seas?

Is the SD hull safer since it can possibly outrun bad weather?

 

[DavidM]

How are yo going to outrun the weather with your limited battery capacity? You base your electric consumption on a speed to length ratio of about 1, but to outrun any weather you probably need to get up to 2 or more. That probably triples electricity consumption per mile.

David

 

[twistedtree]

It is hard to for me to wrap my mind around the amount of energy stored in a 1000 gallon diesel tank. I imagine with the right type of boat you could travel between Seattle and Juneau without stopping once. I am trying to make that trip on 120KWh, stopping at every power pedestal along the way.

Another way of looking at it, assuming my numbers in that other post are correct , is that a full cycle of your batter bank will be about the same as 10 gal of diesel. So a 1000 gal of diesel is about 100 of your battery banks. I imagine that's a good bit bigger than the entire boat.





We probably could have run Seattle to Juneau and back (and every detour along the way) on a single fill up, but we did top up in Juneau so we wouldn't have to worry.

 

[Nomad Willy]

We could make the run from Seattle to Juneau on one tank-up. Would require (by my calc) to reduce speed to 5.5 knots and running straight through. Store 50 gal. On deck and I may be able to anchor and run a bit faster.

 

[Scott Harris]

How are yo going to outrun the weather with your limited battery capacity?


Well I am not, unless the leg was a very short one and I had lots of energy to spare. That would not be often though. This is why I am reconsidering. I am looking into using a displacement hull and going 6 knots instead of 7. So, I have started asking questions about FD hulls.

 

[Scott Harris]

So a 1000 gal of diesel is about 100 of your battery banks. I imagine that's a good bit bigger than the entire boat.

Yep. And each bank would weigh 950 lbs. Almost 50 tons of battery. That's not happening.

 

[twistedtree]

How are yo going to outrun the weather with your limited battery capacity?


Well I am not, unless the leg was a very short one and I had lots of energy to spare. That would not be often though. This is why I am reconsidering. I am looking into using a displacement hull and going 6 knots instead of 7. So, I have started asking questions about FD hulls.

Maybe a Willard? Whatever you pick, I'd plan on building an awning-like frame for the solar panels. I doubt you'll find a boat that already has a house suitable fro all the solar you want, and requiring it will significantly reduce you choice of boats. But adding a solar awning probably wouldn't be too hard.

 

[RedRascal]

Not sure if I'd worry too much about the need to out run bad weather given your float plan. If you are in the cruising grounds south of the northern tip of Vancouver Island you have limited exposure of getting into long stretches with no protection if the weather turns bad. Some of the straits and channels are no joke because they can get a steep nasty 6' chop going but with weather data you can usually avoid it. Plus in theory time is on your side and you won't need to "push it" on iffy days. Even if you do get out there and things go sour maybe you have to turn around and head back where you came from. Maybe you have an uncomfortable ride for an hour or two. That's not the end of the world if you are prepared for it. You and your crew all need to be on the same page that an uncomfortable ride is not the end of the world and neither is spray on the windshield or stuffing the bow into a wave now and then. You only have a couple oceans hops on the way to Alaska, in theory you wait for good weather and have an enjoyable crossing. If you were trying to run from Seattle to Mexico then I'd say worry about being able to outrun weather or have a boat that can deal with weather.

Here is a boat that has some space for panels
https://www.yachtworld.com/boats/1983/sundowner-tug-30-3728927/
Also look at Nomad Willy's avatar, a Willard 30 would give you a pretty slippery hull and some space for panels.

On youtube Sailing Uma has an electric motor and they talk about their conversion. Beau and Brandy also run an electric motor. You may be able to glean some real world performance data from their videos.

 

[DavidM]

That is a cute little tug, but probably a SD hull. And it may be just as heavy as a TT35 but with less room for solar panels. At low speeds power required is mostly related to hull type and displacement so it will probably take just as much power to push it to a given speed as the TT35.

Scott needs a light, long, full displacement boat. Not many of those out there.

David

 

[OldDan1943]

The pioneers are the ones with the arrows in their back.
Good luck with your project.

 

[RedRascal]

That is a cute little tug, but probably a SD hull. And it may be just as heavy as a TT35 but with less room for solar panels. At low speeds power required is mostly related to hull type and displacement so it will probably take just as much power to push it to a given speed as the TT35.

Scott needs a light, long, full displacement boat. Not many of those out there.

David

Yep I am pretty sure the Sundowner would be classified as an SD hull. There are thousands of light, long and full displacement hulls out there however they are sailboats. It's almost an oxymoron for a trawler to be light, long and full displacement.

Other ideas:
-Catamarans have already been mentioned but here is a link to Silent who seems to be getting some things to work. https://www.silent-yachts.com/
-To balance out just buying a Silent on the opposite side of the cost spectrum could be a Bayliner 3818 or 3888. The foredecks could be used for panels and with the flybridge removed and a hard top over the cockpit it would provide a lot of surface space for panels. Flybridges on those boats where made to come off easily for transport on semi trucks. Ditch the diesels for an electric solution. You could probably find one of these for >50k that had a little engine trouble but with a good hull.
-At anchor or when it's calm deploy more solar panels on a floating platform or tender. This sounds like a hassle to setup and take down but extra effort will probably be in cards of going all solar. https://www.amazon.com/Solstice-Swimline-Inflatable-Floating-Dock/dp/B00WXEH1OY?ref_=ast_sto_dp Yes I could see a strong gust of wind flipping one of these so weights or flopper stoppers may be needed for piece of mind if gust winds are in play.
-Not sure if wind would be considered cheating but maybe that would be an alternative option for another kilowatt on cloudy days.

After thinking about the youtubers Beau and Brandy I believe their solar setup up allows them to motor at 1.5-2 knots under the power of the sun without drawing from the battery bank. I think they have about 12 hours of juice to power the motor with no sun. They may be close to being able to achieve your mission if they tweaked their solar, batteries and motor. I believe their solar solution is 3 or more years old so newer equipment would probably gain them some performance improvements.

Scott, maybe you need to fire up the solar folks and get together with the Race to Alaska org for a solar only class. The race to Alaska org has a second event called the Seventy 48 which is a human only powered event. 72 miles in 48 hours in the Puget Sound of Washington State and does not go into Canada. Given the thinking of that group a solar event may be right in their wheelhouse.

 

[OldDan1943]

For the foreseeable future, may I suggest the boat should have a generator onboard to charge the batteries as a safety measure.
If there is a lengthy solar powered race, the generator can be sealed in someway, reserved for emergencies.
For the recreational boater, nothing will mess with the the enjoyment than flat batteries.

 

[Scott Harris]

Thanks RedRascal

That Sundowner looks like a really nice boat. Lots of room for panels, especially if I put an extended rack on the that nice flat roof. But I am nervous about the 110hp engine. Even if I just need half the power to maintain cruise that is 55hp which is (maybe) 22.5 KW of power for the electric motor. My energy budget for traction is a maximum of 120 KWh. This would give me less than 6 hours of cruising. So I need a smaller or more efficient boat.

I noticed Willy's profile the first time Eric posted on this thread. Fortunately for me, Eric has reached out and has shared a lot of info about the Willard 30 Nomad. He informed me that it takes 18hp to reach his desired cruise speed of 6.15 knots. That would be about 9KW (I'm having the inboard motor manufacturer check on that now) for 6.15 knots. Not as good as 7 knots for 7,000 watts as TT35 estimated, but maybe just doable.

But both are just estimates at this point. I am hoping to test the TT35 number this spring. Being an outboard I could possibly do it at little cost, especially if Torqeedo loans me a motor for the test. The Willard Nomad test is more problematic. I would have to buy one and do the conversion in order to do the test. It is sort of like the story of the chicken and the pig discussing who is more committed to providing the farmer a bacon and eggs breakfast.



So now I am looking into electric inboards. Any advice on inboard vs outboard will be most appreciated.

Thanks

 

[Scott Harris]

For the foreseeable future, may I suggest the boat should have a generator onboard to charge the batteries as a safety measure.
If there is a lengthy solar powered race, the generator can be sealed in someway, reserved for emergencies.
For the recreational boater, nothing will mess with the the enjoyment than flat batteries.

Yes, that is a wise and prudent decision. But my goal is to go solar-electric not hybrid-electric.

When I use the boat by myself it will be mostly in the Puget Sound where there is always a 50 amp plug quite close.

Going to Juneau is a different matter. I don't plan to go by myself though. I plan to go with a group like the Slow Boat Flotilla. Of course, in order for them to accept me I would have to first prove that my boat has a very high probability that it can make it without bumming electricity from their generators (I would consider this a fail). But I would think they would be there for me in an emergency.

 

[Scott Harris]

Scott needs a light, long, full displacement boat. Not many of those out there.

David

If any know about one please pass the info along.

 

[cardinaltlee]

I have been thinking about a solar trawler that would use a towed solar array of panels that would be deployed in good weather and stowed on the boat in bad weather. Seems like you could have a lot more solar panels that way.

 

[Scott Harris]

I have been thinking about a solar trawler that would use a towed solar array of panels that would be deployed in good weather and stowed on the boat in bad weather. Seems like you could have a lot more solar panels that way.

I have considered that too. But I think the towing would be problematic and that the saltwater would quickly destroy the panels, the junction box electronics, and the connectors.

Maybe if you built a platform for your dingy and towed the dingy it could work. Not sure about the energy tradeoff though (energy to tow vs energy acquired). Sure would be a hassle deploying them. So I am not keen on the idea initially. But if you ever hear about someone being successful with this method I sure would like to know about it.

 

[Miz Trom]

Tt35

Hi Scott:

Hubby and I own a TT35. However, we call it an American BoatWorks because we prefer to not give anyone the impression that we endorse Ken Fickett's business practices.

There are many things we love about our boat, but it really is not a good platform as an e-boat because of its planing hull.

I'm so glad you have realized that your electric motor(s) and batteries will be much more suited to a full displacement hull. I think that your cruising grounds are more suited to a displacement hull, too.

We are delighted with our outboards, so I can understand why an outboard-based propulsion system appealed to you. But IMHO, outboards may be more suitable for our particular cruising grounds (from Knoxville to the Keys) than yours.

You should check out Cruiser's Forum for lots of info from sailboaters who have converted to electric motors. Wealth of information there.

I love your dream! When you find the right displacement vessel for your project, please start a new thread and keep us all updated on your progress. I want to know more about this battery system you are building.

I've been looking into doing something similar on a day boat for us and our dogs, a pontoon boat with two Torqeedos, to be exact. I really like the Firefly batteries because they can be drawn down to 20%. Therefore, fewer batteries, more available power, and less weight than comparable AGMs or lead-acid.

Warm Regards,
Mrs. Trombley

 

[tom hudson]

You might reach out to George McNeir in Wilmington, NC. I don't have his contact info, but you may be able to find him using Google or social media. George has built a fully electric cruising boat, and is pretty up on technologies, costs, and such. At the very least, he'd be a good one to share ideas with.

Don't neglect the idea of a solar/electric motorsailer. After all, winds are created by the sun, so using sails really wouldn't be "cheating."

 

[RedRascal]

This is probably a good start to find out more about George's boat. Mog Canal Boat – Just another WordPress site

 

[Scott Harris]

The MOG boat is very interesting. It was surely way ahead of its time. It looks like a boat more suited to a lake or a canal than open waters, yet they have taken it many places.

 

[Scott Harris]

Hi Miz Trom,

I like your boat. Where did you get that fly bridge?

I was first attracted to the TT35 because of its large flat roof that could hold a lot of solar panels. As I did more research into the trip I realized that the size of the battery bank and the efficiency of the boat would be the most important factors. Even though I have recently learned that the TT35 does not have the best hull for the PNW, I continue to consider it because of the hope that it may obtain 7 knots using only 7 KW of power. I would need to test this out before giving it further consideration though.

How is the efficiency of your boat?

 

[Nomad Willy]

How are yo going to outrun the weather with your limited battery capacity? You base your electric consumption on a speed to length ratio of about 1, but to outrun any weather you probably need to get up to 2 or more. That probably triples electricity consumption per mile.

David

David,
I’ve argued this forever but I want to argue it again as it’s so applicable here w a boat even slower than Willy.

The weather information is plentiful. Even 15 tears ago (about 2006) we basically had the info we needed. HaHa but we crossed Johnstone Strait to anchor in Allyson Harbour where it blew 50 knots. OK we shouldn’t have been there and I don’t remember the exact forecast but it was close to what we needed. But in electronics 10-15 years later (now) as electronic navigation for small boats is light years ahead of where we were in 06. And the north end of Johnstone Strait is pretty far out in the wilderness despite what Murray says.

To me outrunning weather is and always been a stupid concept. No one needs to out run weather. If one dosn’t have good nautical skills sufficient for the occasion one shouldn’t be there. Skills include judgement. My premise 10 or more years ago was that one should be able to reach safe harbor or at least in the lee of an island for expected winds.

But out running weather is not something that should be expected for a given skipper in a given geographical area w a given boat.
But now one does not NEED to be able to outrun weather. There’s much much more that just a weather radio on most trawlers. At this point I see being able to outrun weather in a trawler is the stuff of Alice in Wonderland.

 

[twistedtree]

....I continue to consider it because of the hope that it may obtain 7 knots using only 7 KW of power. I would need to test this out before giving it further consideration though.

I think you will find very little difference from hull to hull in the power required to reach any given speed. And I think 7kw to move 7kts is highly optimistic, if not fanciful.


If you haven't come across boatdiesel.com, I'd suggest checking out their calculators. You may need to join to get the required access, but it's worth it. I just ran the numbers to figure the required power to move a 34' LWL displacement boat 7kts, and it's 10-11kw. 7kw will get you about 6kts. You can play around with different hull forms, lengths, displacements, etc. to see what the sensitivities are. I think it will help a lot in figuring out what's realistic.


In general, I think power/fuel & speed for a boat is much like MPG for a car - everyone exaggerates what their boat/car can do.

 

[Nomad Willy]

Twisted Tree wrote;
“In general, I think power/fuel & speed for a boat is much like MPG for a car - everyone exaggerates what their boat/car can do.”

Indeed some are believable or at least possible but others ???

 

[KnotYet]

Hi Miz Trom,
I like your boat. Where did you get that fly bridge?

I was first attracted to the TT35 because of its large flat roof that could hold a lot of solar panels. As I did more research into the trip I realized that the size of the battery bank and the efficiency of the boat would be the most important factors. Even though I have recently learned that the TT35 does not have the best hull for the PNW, I continue to consider it because of the hope that it may obtain 7 knots using only 7 KW of power. I would need to test this out before giving it further consideration though.
How is the efficiency of your boat?

7 kW is barely 9 HP. I know of no boat that size capable of 7 Kt with only 9 HP.
If you add in efficiency loss from the motor it will be more like <7 HP.

 

[OldDan1943]

I think we need to take baby steps. Figure your battery weight and capacity then the solar panels to charge the batteries and finally install a small generator, just incase. Once you get everything right, you wont need to use the generator.
Starting with a hybrid is a good first step.