Designing & Building Hammerhead

[twistedtree]

A boat that's powered to its top speed will see an equal number of engine hp and prop hp. Anything lower will see (usually huge) differences between the number of hp the engine puts out, and the (much lower) hp the prop puts in the water.

When you say "engine hp" am I correct that you mean the max engine hp? Because of course at all times the HP coming out of the engine equals the HP the prop puts into the water, ignoring drive line losses.

If you cruise at - say - 1800 rpm, instead of at the max 2,500 rpm, you can prop to optimize (equalize) for 1800 rpm. In such a way that - at that rpm - the prop performs best and has an equal engine hp and prop hp number.

Let me state this a bit differently, and tell me if it's still what you are saying. You are comparing to an engine propped conventionally where it just makes max HP & max power output. Then assume that propped like that the boat's 10 kt cruise RPM is 2500, and power output is something less that the rated max of the engine. Now re-prop so you load the engine to the same HP at 1800 rpm instead of 2500 rpm. It's producing the same HP so the boat goes the same speed. You have a lower shaft speed, so need more pitch and/or more diameter.

Given prop losses at lower rpm can easily be 30%, potentially a 30% efficiency gain could be accomplished.

Regards, Edwin.

I'm confused by this. If you as saying what I think you are saying, the prop sill be turning slower, not faster. But at the same time, I think slower is better for efficiency, or at least that's what I have always read. Bigger diameter and slower turning are best for efficiency. So somehow I'm not following here.

 

[O C Diver]

There are more moving parts to this discussion. As an example, my 4045 JD cruises at 1,300 rpm. Fuel burn is 1.5 GPH for my boat setup. The Computer tells me at this RPM and fuel burn the engine is producing 40% of its available HP. So theoretically, it could consume over 3.5 GPH at 1,300 RPM. The question then becomes for that specific RPM, what is the consumption rate that produces the most HP per gallon. Keep in mind the air consumption is static while the ratio of fuel to air changes dramatically. While measuring exhaust gas temperature may help, it's not telling you at a given RPM what fuel burn produces the most HP per gallon.

Ted

 

[twistedtree]

There are more moving parts to this discussion. As an example, my 4045 JD cruises at 1,300 rpm. Fuel burn is 1.5 GPH for my boat setup. The Computer tells me at this RPM and fuel burn the engine is producing 40% of its available HP. So theoretically, it could consume over 3.5 GPH at 1,300 RPM. The question then becomes for that specific RPM, what is the consumption rate that produces the most HP per gallon. Keep in mind the air consumption is static while the ratio of fuel to air changes dramatically. While measuring exhaust gas temperature may help, it's not telling you at a given RPM what fuel burn produces the most HP per gallon.

Ted

Exactly. That's the elusive Brake Specific Fuel Consumption that measures gal per hp-hr or similar units. grams per kwh is commonly used. Complete characterization of an engine will include a 3D "map" of BSFC across the full range of RPM and torque. In other words, it shows fuel consumption per HP at every load point. The Deere datasheets that I posted earlier show it along the prop curve. But that's not the whole map.

 

[Scooby5959]

Maybe you can answer a question

There are more moving parts to this discussion. As an example, my 4045 JD cruises at 1,300 rpm. Fuel burn is 1.5 GPH for my boat setup. The Computer tells me at this RPM and fuel burn the engine is producing 40% of its available HP. So theoretically, it could consume over 3.5 GPH at 1,300 RPM. The question then becomes for that specific RPM, what is the consumption rate that produces the most HP per gallon. Keep in mind the air consumption is static while the ratio of fuel to air changes dramatically. While measuring exhaust gas temperature may help, it's not telling you at a given RPM what fuel burn produces the most HP per gallon.

Ted

We’re in a diesel engines power band ,hp and torque curve does that engine give you the biggest bang for the buck ,another words convert fuel to energy at its most efficient rate ,answer that one I will go to the next step

 

[Scooby5959]

Here’s another example ,C 15 caterpillar TwinTurbo one of the most inefficient engines ever built , got horrendous fuel economy, what engine can you think of that is the most efficient ,that will give you your answer, some people say it’s an engine that starts with a G

 

[Salty Pelican]

Isn't the cpp doing exactly what we are discussing? Changing pitch to optimize needed power output with rpm?

A standard prop, optimized for a certain cruising speed, is exactly that. Like a "slice" of cpp, only not continuously optimizable, but only in the small power band that the foreseen cruising speed takes place.

Regards, Edwin.

 

[Scooby5959]

I’m not sure what we’re talking about anymore actually, no offense to anybody I get easily confused, I’m not doing a very good job of explaining my point , The reason a CPP is needed for my scenario is to make It possible to use a larger engine I propose to use , A much larger engine , I believe you should pick an engine based on its torque curve where it gets the best fuel economy ,I believe that to be somewhere between 1000 and 1400 RPM depending on things like bore and stroke , the longer the stroke the more torque kind of like a motorcycle for climbing hills , a Harley engine with its large stroke works much better than a higher RPM two-stroke , I will try to research some particular motors and make my point better later, I appreciate you hanging in there with me so I can figure out how to make my point, I also need to know what the hull speed of the boat your building is , it would need to be 10 1/2 knots , For this to work , with your 10 not cruise you’re looking for ,I’ll get back with you , The CPP propeller would be needed to make a larger engine usable at low RPMs you don’t want to be going seven knots at idle ,now you’re going to think I’m completely crazy,

 

[Scooby5959]

The most fuel-efficient engine in the world is a diesel engine that turns less than 1000 RPMs ,it’s also the size of a house , there is a reason they use slow turning engines for freighters ,A freighter also has a high hull speed due to its length ,kind of what I’m talking about here , A slow spinning high torque engine is the most fuel-efficient type of engine, much much more fuel efficient, I will dig up some real numbers and get back with you

 

[O C Diver]

We’re in a diesel engines power band ,hp and torque curve does that engine give you the biggest bang for the buck ,another words convert fuel to energy at its most efficient rate ,answer that one I will go to the next step

As Twistedtree alluded to, the fuel map gives you the best answer.

The general rule of thumb was to be near the peak of the torque curve as far as RPM. At or above the point where the normal operating oil pressure, oil temperature, and coolant temperatures were reached for that RPM and generally below 70% of the value for that RPM on the maximum HP or fuel consumption curves.

Unfortunately we can't always get where we want to be with respect to the above, plus speed, and being able to attain WOT. In my situation, a 4:1 transmission, 1,600 RPM cruise, and reprogramming the engine computer to M1 104 HP at 2,400 RPM would be the answer. Unfortunately the transmission doesn't exist.

Ted

 

[Mako]

Here’s another example ,C 15 caterpillar TwinTurbo one of the most inefficient engines ever built , got horrendous fuel economy, what engine can you think of that is the most efficient ,that will give you your answer, some people say it’s an engine that starts with a G

Focusing on mechanical engines, the most efficient ones I've come across which are still in production are the Deutz by Weichai. SPF of about 193-195 gram/kw-hr. They also have medium speeds achieving 188 gm/kw-hr.

Gardners are legendary and beautiful to look at, but sourcing parts and support is limited.

However, IMO as a general statement, anyone here of "normal" means who embarks on a worldwide bluewater journey will likely equip himself with the skills and parts inventory to repair and overhaul his own engine, so perhaps having access to technicians and repair centers is quite a minor consideration.

I don't think any of my comments above apply to an electronic engines. I think before embarking across the ocean with your Tier4 it's best just to start crying, because you'll be writing checks of $10k multiples to fly factory techs to Bora Bora to troubleshoot your micro-brain.

 

[Scooby5959]

I was told by a factory trained caterpillar tech that rebuilds engines every day day in day out ,he will rebuild an engine and replace those parts necessary that don’t meet factory specs , if they meet factory specs leave them alone , that’s pretty much the way an in frame rebuild is done ,if the cam needs work , the engine is usually pulled and replaced with a reconditioned unit , because machining is required and that Has to be done in the shop .that same mechanic told me if you want to judge the Condition of a used engine look at the amount of fuel that engine has burned .,the computers keep track of how much fuel they used ,don’t look at hours , they look at fuel burn ,that will tell you how many times those pistons have gone up and down hours don’t tell you as much because you don’t know what speed the engine was running at most of the time ,if it was operated by somebody like me it was run at 1200 RPMs most of his life . That’s where I run excavators, just above idle, Day after day month after month year after year ,that machine will live four times longer than a-machine run near 2200 rpm , don’t care what you say been there done it works ,Never hurt the engine, not even slightly those people that say you need to run engine at higher RPMs are entitled to her opinion ,I don’t agree ,Chances are those people also didn’t rely on those engines to make their living .if that engine fails, that means I can’t feed my family slow equals long

 

[Salty Pelican]

Thanks all for chiming in. In general, an engine creates torque. How fast it can do that is where the horsepowers come in. With all of you that focus on torque instead of hp. Hey, this is a LONG range expedition yacht we are designing ...

On torque: making it costs fuel. Bigger engines produce more torque and may be slightly more efficient at it, but in the end creating torque means burning fuel.

I love low rpm, so no 3,000 rpm engine for me. The m1 status and 2,300 rpm of the JD4540 is great. A lot of torque. Due to the high displacement relative to more leisure boat engine designes like Fiat Marine. And the turbo helps too.

Learning about engine maintenance and repairs is a must. I agree. It is a field I need further education and experience in and I have two years to prep. Shouldn't be too difficult, given my parents had a car garage/dealership and both of my brothers are engine mechanics.

On the big old luggers and sorts. You gotta love those old slow-goers! But we'll go for a new and modern one. Functionality over sentiment. And a big old engine would add weight as well.

Regards, Edwin & Veronika.

 

[Mako]

@Salty you might want to check into EU emissions requirements again. I believe if your engine is 176hp or less then you only need an IMO2 engine, which can be achieved with a mechanical engine.

 

[Salty Pelican]

It's 160 bhp, Mako!

Regards, Edwin.

 

[Mako]

Great. What speed can you achieve with 160hp? Have you considered this or do you wish to stick with an electronic engine?

 

[Scooby5959]

I’m pretty good with a wrench and a welder, my communication skills are lacking ,if I was building your boat , I would make sure it had a hull speed of 10 1/2 knots or more , anything less fuel economy will suffer that being said , I would select an engine that supplied needed horsepower just above idle , I know whatever , the three engines I might consider caterpillar Cummings Detroit, I think I would have to choose the cummings n14 natural Aspirated , that would give you the horsepower you needed just above idle ,coupled with a CPP will enable you to use the entire RPM curve ,if that’s what you want to call it, the Detroit series 60 is another very good engine ,parts everywhere they built a couple million of them, I think the n14 is a little better, if I had a designer/engineer recommend a high rpm turbocharged after cooled engine ,I would fire him ,but you would probably fire me too, I’m very confident that this would give you the best fuel economy , very confident ,this is all I’m going to say on the subject ,40 years of making my living around diesel engines gives me the confidence to say this ,but I don’t care to repeat it anymore

 

[Scooby5959]

Oh good luck with your project I wish you the best

 

[Salty Pelican]

Thanks Scooby!

Mako, she'll do up to 12 knots depending on load.

Regards, Edwin.

 

[dannc]

..
I don't think any of my comments above apply to an electronic engines. I think before embarking across the ocean with your Tier4 it's best just to start crying, because you'll be writing checks of $10k multiples to fly factory techs to Bora Bora to troubleshoot your micro-brain.

Unless the US EPA regulations have changed, boats only need to use Tier 3 engines. Though, to be fair, Tier 3 seems to be only slightly less complicated than a Tier 4. At least Tier 3 does not have to use DEF.

One of the Diesel Ducks had engine trouble in Tarawa and it was ugly. Not the builders or engine makers fault but owner caused. The builder did greatly help out the owner but getting parts and tools was a time consuming effort.

Later,
Dan

 

[Salty Pelican]

Let me be more specific:
- 12 knots at light load;
- 11.5 knots at medium load;
- 11 knots at full load.

 

[Salty Pelican]

More renderings!

Last serie of renderings. Updated for a more realistic alu-look and -feel, as well as the additional solar panels above the salon. And then some ...

She is 20 meters long, 5 meters wide, 25t empty, 35t fully loaded. Propellor window goes 1m25 into the water.

Regards, Edwin & Veronika.

 

[Salty Pelican]

Pictures/renderings with background!

Edwin & Veronika

 

[dannc]

Is there a boat under all of those solar panels?

That many solar panels is a game changer for power production and usage on a boat. Running the numbers on a potential PV configuration for a boat has been an eye opener, especially, with LiFePo batteries.

Later,
Dan

 

[Mako]

Ed I really like that slight reverse rake on the bow. Sorta retro like an old rum runner. I hope you keep it

 

[Salty Pelican]

Its a keeper for sure, Mako, the reverse bow!

Solar is enough to power the whole boat. Stabs will be 48v electric, for instance. Cooking is electric too.

There'll be an electric engine on the prop shaft so we can use additional electrical power to help move the boat.

Regard, Edwin.

 

[Salty Pelican]

So, just a short update and another rendering. Our NA is working on the exact engine placement and shaft lay-out. His staff is working on the main room and the aft deck.

The engine is mounted a little lower in the boat, meaning that the shaft angle is further reduced by another 0.5%. That's 0.5% pure efficiency gain. Love these small, incremental gains. Especially since - if you have enough of 'm - they add up. On themselves and as one little gain here also gives another little boost to another win somewhere else. Virtuous cycles.

The outside steering position on the aft deck is now completely center line. The banks and furniture and kitchen follow the shape of the boat, which makes for an overall nicer look. Again, little things adding up to bigger overall gains. A lot of storage under the outside cooking and sitting area. One cannot have enough storage space on a ship, right? Well, as long as hull lines and water management aren't compromised, of course.

By the way, our ship has the ability to beach. She'll sit at a 2 degree forward angle, when beached. That should be okay. Especially if we beach on ... a beach, which always slopes upwards.

Regards, Edwin & Veronika.

 

[Mako]

Solar is enough to power the whole boat. Stabs will be 48v electric, for instance. Cooking is electric too.

There'll be an electric engine on the prop shaft so we can use additional electrical power to help move the boat.

I like the idea of a get-home drive being linked to the main shaft, as opposed to a small additional shaft/folding prop. However you're not going to power that from 48VDC with any significant range. So assuming you have a 12kW genset, you're wanting to pull about 15-16 hp out of it. May be best to utilize a 240VAC motor on your main shaft (with a removable chain) or better yet a 3-phase controlled by a VFD

 

[O C Diver]

There'll be an electric engine on the prop shaft so we can use additional electrical power to help move the boat.

Regard, Edwin.

I'm assuming you are referring to using surplus solar energy to supplement the diesel propulsion. I'm curious as to how many actual HP could be expected from absorption and conversion to electric motor output.

Ted

 

[Xlantic]

Edwin, I also built a solar-panel roof above the fly-bridge. I added a front "visor" with a similar angular look to the front of the fly-bridge and house which also adds strength and rigidity to the roof.

I have also built but not yet installed a mirror visor or hood for the aft end.

 

[Salty Pelican]

Looking good, Xlantic! Thanks for sharing.

OC, Mako,

The electrical engine on the shaft provides multiple benefits. It acts as back-up propulsion. And as back-up generator. There will be a generator (12 kWh) that's the de facto back-up engine. The electric engine will be 400v, three phase. Battery power, for instance solar generated, can be used to help propel the ship forward.

I calculated that it can run an hour to two hours a day on electric power. At about 6 knots. I think, in practice, the additional electrical power, solar generated, will be used to help the main engine for a much longer time, but at a lower power setting. For instance 3 to 5 hours at 4 kWh, thus further limiting diesel consumption.

The JD 4540 is the main engine. The electrical engine will be back-up propulsion. Solar energy will provide enough electrical power for the house-banks ... and then some. The generator will serve as a back-up to the solar power generation AND serve as the back-up for the main engine, providing electricity to the electrical motor. Solar panels and generator electricity will be stored in a Lithium/ion battery pack that will power the electrical engine. Or the other way around, where the electric engine draws in power from the shaft/main engine and serves as the back-up to the generator.

Triple redundancy. And basically what in a car would be called a hybrid system, that also helps to manoever the ship in-harbor on electric power only (electrical motor for propulsion forward or backward and electric bow and stern thrusters).

Regards, Edwin.