Designing & Building Hammerhead

Yeah, even some semi-displacement boats have 'm. Like Deep Water Yachts and Elling. If the weather is good and they go fast, the hull shape creates stability. When they (need to) slow down to displacement speeds, they benefit from the Magnus Master stabilizers.

This system is - given its working range of up to 12 knots - primarily aimed at displacement boats. Small boats up until 20 tons (metric) can do with one system. Boats up to 40 tons (metric) use a double set-up, like we have on "Moonshine". Bigger boats can be equipped with four or six or even eight units.

I wouldn't be surprised to see some other brands switch to this type of stabilizer in the near future.

Here's the voyage of Astra. A 24 meter trawler that sails around the world. I think she's equipped with 4 Magnus Master rotors, provided by DMS Holland.

https://www.mby.com/features/around...s6A8NQDPCys2qi0EReQ4vnn3Nab4S-A8owQK1mDPzfOog

Regards, Edwin.

Amazing blog. 24m and RTW. Wow!!!

What's RTW?

Round the world. Common sailor short hand like BWB blue water boat. Sorry. I’m thinking your build would warrant both descriptions. Your’s could “do the clock”. (Another way to say RTW)

Thanks for clarifying!

English is not my native tongue.

Regards, Edwin.

Underwater-ship design of the LM65h

Back to the topic of us designing our own passagemaker. Here are two pictures of the underwater-ship design:

Regards, Edwin & Veronika

Good day compatriot.

A whole story with a lot of ambition.
We have already met you a few times, I recognize the Bruijs cutter.
I am very curious about the end result so keep following this thread.
What brand of equipment do you think you have in mind for the new ship?
For autopilot I would choose Simrad (old Roberson) AP 80, great pilot in all conditions!
Why this comment, as the autopilot is one of the most important parts on board on the long hauls.

Greeting

Pascal and Sigrid.

Hi Pascal and Sigrid,

Thank you for posting. Detailed design is all but ready. Doing minor tweaks on it, given for instance the quick developments in electro motors and regeneration options.

We agree the autopilot is amazingly important for long trips. In fact, it even makes shorter trips so much easier. Like having an extra crew member, that does all the steering while underway, making the trip more about oversight and management than directly physically piloting the vessel.

Our Bruijs, which is for sale, has autopilot and we love it. Our current Jetten 50 MPC weirdly enough does not. So we are having it installed, together with new screens, radar, etc.

We are currently talking to people interested in our yacht and expect a first sale in 2023. Our own boat hasn't started being build yet, because of severe family health issues, that puts us in a care-giver position, and some other stuff that's going on.

Regards, Edwin & Veronika.

Those few words in that last sentence tell so much, wished strength.

Greeting,

Pascal.

Update on "Moonshine" at the shipyard!

So ... with Salty Pelican all but sold and work on the all-new LM65h not yet started ... allow me to update you on our current motor-yacht "Moonshine".

Moonshine currently sits at the shipyard for extensive upgrades. Turned out more things needed to be done. Not just the antifauling, some minor repairs, and a complete suite of new plotters, radar, AIS, and autopilot. Bit more, as it turns out.

There was some slack on the propellor shaft. We expected the bearing closest to the prop to be in need of being replaced, but as the shaft was taken out, it turned out that all three bearings were worn out. At the lower end. Further investigation informed us that the thrust bearing was installed like a centimeter and a half (half an inch) too low, lowering the shaft, and allowing it to eat away at the bearings.

Solution? Reinstall the thrust bearing on its proper location, change all three shaft bearings. And we added a rope cutter in the process. But that was already planned. Pics of rope cutter and spent shaft bearings underneath.

Okay, "buy a boat and work till death", right? In my case the warf does the work, but I have to work to pay for their labor. But this was the easy part. The shaft was the additional work that didn't cost a ton.

What did? Well, having to replace the whole electrical system. That did cost a ton. Or will. What happened? As we sailed the boat from our harbor to the shipyard - like 5 NM's only - I noticed our housebank dropped to 98%, then 96%, then 94%. It does drop, but it never dropped with the engine on. We have two alternators. One of 55 amps (24v) for the engine start batteries. Another one of 70 amps (at 24v) for the housebank and the two additional batteries (one for the bow-thruster and one for the stern-thruster).

Should be enough, right? Even with 2 stove electrical cooking and freshly installed electrical MagnusMaster stabilizers. Only it wasn't. The housebank (a 10.3 kWh traction battery) supposedly died on that small trip from our harbor to the shipyard.

And that was the least of our problems, as it turned out. I mean, we could smell the gas and I decided for once NOT to fire-up a cigar, which probably saved our lives. But more sh*t happened as a result of the housebank/traction battery failing.

It turns out that one management system (there must be a better word) was managing both the housebank and the batteries for the bow- and stern-thrusters. As the housebank died, the management system didn't get any feedback and decided that the logical choice was to now put all the power from the 70 amp alternator into the thruster batteries. And as those were underpowered, that basically blowed them up ... and destroyed quite a bit of the wiring and the converters, etc.

Oxyhydrogen ... hope that is the right word ... formed during our last sail. Normally I smoke a cigar after mooring in a new marine. Somehow, that felt "off" that day. It basically saved us. Had I lighted that cigar, the ship would have probably blown up. And had the batteries not been in a relatively sealed container, the wire burning (with oxygen present) would have resulted in a full-out fire.

All right. We survived. And the two most obvious outcomes didn't come to fruition. Good for us! Now, what's the solution?

We'll get rid of the spent traction battery housebank. The 10.3 kWh unit will be replaced by a 23 kWh LiIon battery bank. The engine starter batteries are fine and will stay. The bow- and stern-thruster batteries will be replaced by much sturdier ones, that are tailored to peak discharge rate ... 'cause that what the (oversized) thrusters need. Each thruster gets 6 optima yellow top batteries.

"Moonshine" will also get a generator. WhisperPower, 12 kW. The generator and batteries are under a management system (yes, one per battery) that will basically be tuned according to our needs. For example, we can tune it like this: if the battery capacity is only 20% remaining, the generator automatically starts and fills the LiIon bank up to 85%. Or: if the system "sees" we are running the stabilizers and cooking stove and airco, it will pre-emptively start to work and deliver additional electricity. Or: if we feel we don't want the generator to kick-in at night, we can push it to charge NOW.

What's more? Well, new, bigger, thicker, sturdier electrical wiring. And - where the 55 amp alternator for the engine start batteries stays - the 70 amp housebank unit will be replaced with a 200 amp version. We want to be able to run most functions - if need be - right from the engine and that's what the 200 amp alternator brings to the party.

Final touch? Four solar panels. Yeah, doesn't really make the ship go around the globe ... but it will allow for the ship to be powered even without shore-power like forever.

Quite the write-up. Hope you enjoy reading about our endeavors and adventures - harbor bound though they might currently be.

Regards, Edwin & Veronika.

Wow, that's quite the list of upgrades.


By the way, what's the status of LH65?

All the drawings (2d and 3d) are ready. Shipyard is ready to start building. Looking to find a first customer, as we ourselves are currently preoccupied with family affairs that take up a lot of time & energy.

Regards, Edwin.

Salty are you planning on starting construing your prototype or do you need to wait until the first customer contracts with you?

Ideally we'd start it ourselves, but currently - given our family circumstances - that is not an opportunity. Maybe in a year things will be different, but health has changed goals, unfortunately.

Regards, Edwin.

S/L- and D/L-ratio's and more ...

With our current motorboat "Moonshine" at the shipyard and the LM65h project on hold for now, I did some calculations on S/L and D/L ratio's for both ships. See the picture attached.

Moonshine has a D/L-ratio of 246. I'd say that makes her an average weight boat, not a heavy or light weight one. The LM65h will be build out of aluminium instead of steal. Weight is pretty close to Moonshine's, but her LOW is much longer, resulting in a D/L-ratio of 111-ish. Now, that's definately light weight category.

Moonshine has a S/L-ratio of just 1.0 when we sail her at a cruising speed of 7 knots. The uses 9 liters per hour, or about 2.2 gallon per hour at that speed. Engine turns 1,500 rpm out of a maximum of 2,500.

On longer passages over sea, I'd like to go a bit quicker. Preferably 7.5 to 8 knots, instead of only 7. That would bring the S/L-ratio to 1.1 to 1.15. Fuel consumption does go up significantly though to 13 to 14 liters per hour. That's 3.2 to 3.5 gallons per hour, compromising total range, since she carries 2250 liters of diesel (550 gallons) total.

We are considering changing the current fixed prop to a Brunton's Autoprop for more efficiency at half load / cruising speeds. Should allow for a faster cruise without compromising on range.

Regards, Edwin.

Salty Pelican said:

We are considering changing the current fixed prop to a Brunton's Autoprop for more efficiency at half load / cruising speeds. Should allow for a faster cruise without compromising on range.

Regards, Edwin.

Click to expand...

Presumably the goal is to shift engine operation to a different rpm/torque combination that has better bsfc (fuel burn per hp or kw of power developed)? What engine(s) do you have, and do you have access to a reliable fuel burn map? They seem very elusive for many manufacturers.

Fixed props are designed to operate at one explicite speed/rpm. Optimized for any boat, that's usually top speed, because: 1. That's where power is needed; 2. If you optimize for lower cruising speeds, if you go faster you over rev the prop, damaging it prematurely.

Now, a normal motorboat would have a 60% efficiency at that top speed, with the prop performing optimally, but if you look at "hp in the water charts", it is easy to establish that at anything lower than top speed, efficiency easily halfs, resulting in 30 to 40% efficiency only.

Since we run Moonshine at cruising speeds, and I want to both increase the cruising speed and the range, here's what the autoprop does: it automatically - based on rpm, water pressure, and torque - adapts pitch and diameter. It thus optimizes (with careful selection of the right autoprop) efficiency at any speed. Gain at top speed is neglegable, but at lower cruising speeds a 30 to 40% gain should be obtainable. Even at 1500 rpm and a 9 liter per hour fuel burn, the efficiency will now be closer to 60% instead of the 35-40%-ish, that we get now. This efficiency gain can be used for higher cruising speeds and/or longer range.

Here's an evaluation from some years ago:

http://mayrik.com/images/ArticleAutopropPM.pdf

Moonshine has a 6.1 liter Vetus Deutz 6 cylinder. M3/4-rating. Turbocharged. 170 hp at 2500 rpm.

Regards, Edwin.

Salty Pelican said:

Fixed props are designed to operate at one explicite speed/rpm. Optimized for any boat, that's usually top speed, because: 1. That's where power is needed; 2. If you optimize for lower cruising speeds, if you go faster you over rev the prop, damaging it prematurely.

Now, a normal motorboat would have a 60% efficiency at that top speed, with the prop performing optimally, but if you look at "hp in the water charts", it is easy to establish that at anything lower than top speed, efficiency easily halfs, resulting in 30 to 40% efficiency only.

Since we run Moonshine at cruising speeds, and I want to both increase the cruising speed and the range, here's what the autoprop does: it automatically - based on rpm, water pressure, and torque - adapts pitch and diameter. It thus optimizes (with careful selection of the right autoprop) efficiency at any speed. Gain at top speed is neglegable, but at lower cruising speeds a 30 to 40% gain should be obtainable. Even at 1500 rpm and a 9 liter per hour fuel burn, the efficiency will now be closer to 60% instead of the 35-40%-ish, that we get now. This efficiency gain can be used for higher cruising speeds and/or longer range.

Moonshine has a 6.1 liter Vetus Deutz 6 cylinder. M3/4-rating. Turbocharged. 170 hp at 2500 rpm.

Regards, Edwin.

Click to expand...

Thanks. So you are talking strictly about the efficiency of the prop itself? I guess a ratio of shaft HP to thrust? I would have expected prop efficiency to drop at higher revs, not increase, so this is quite interesting to me.

It is! No, boats are more efficient at lower speeds, but the engine (or better: fuel burn translated into actual hp in the water) becomes much less efficient and looses up to 50% of its hp (delivered in the water) at cruising speeds. That's why the autoprop is such a great option for longer range cruisers: at the lower speeds we cruise at friction etc. are pretty low, now if we can almost double the prop efficiency ... that's like cutting fuel burn in half ...



Edwin.

If I understand it correctly, a Variable Pitch Prop allows you to run higher pitch at lower rpm’s to allow the prop curve to get closer to the HP curve allowing more speed (prop rpm)at the same rpm or same speed at lower rpm (but more actual HP input). Allows the engine to operate more efficiently. At WOT the pitch reduces to what would on a fixed pitch prop be the closest to max rpm and HP/prop curves meet. It’s all about loading the engine more efficiently through its operating range.

James

Any thoughts on how this translates to parallel hybrid propulsion? Understand how the Autoprop is an advance over a fixed prop but accept a true CPP gives yet another gain in efficiency. So the question is although there’s a clear benefit with either a Autoprop or CPP for internal combustion is there any benefit for electric motors?

I think your description is adequate, James. And the better load at lower rpm does not only result in a faster cruising speed and/or lower fuel burn, but - indeed - also loads the engine at lower rpm. Better for the engine and no need to do a 20 minute per 24h full throttle to burn the engine clean.

Hypo, I'd say the engine does not matter. Electric engines also have a power range and rpm and thus a prop that's tailored to the upper end.

I'd add to that that it - the autoprop - might even be more beneficial if the electric engine - as a hybrid - drives the main shaft. Usually in a "electric/hybrid/back-up"-situation, the electrical engine is much smaller in power / torque output than the main diesel. For that small back-up to push that big prop with big pitch through the water is less than optimal. Given the wide "spread" of the autoprop, it could be of tremendous help here.

On CCP's: the consensus seems to be that is an even better system, but it needs a lot of constant tweaking and is pretty darn expensive. Personally, I like the "auto" bit of the autoprop solution.

As an update, we just visited the shipyard. We decided to go for two 16 inch plotters instead of the two 12 inchers originally planned. Looks amazing, I won't have to use my reading glasses, and the dashboard is made for it.

The through-holes for the generator (10 kW) are put in place, as is most of the tubing. Generator itself comes end of February.

The Diesel Dipper is installed. It syphons water and sh*t from the very bottom of the tank, and - via a labyrinth - separates it from the diesel, thus preventing filter and/or engine contamination.

AIS is installed, as is the radar reflector. The Raymarine Doppler radar is also installed.

Two small dents in the underwater-ship have been pushed out and repaired. New (bigger!) batteries for bow and stern thrusters are in. The original traction house battery bank will be replaced by a 23 kW LiIon package.

The airconditioning unit is in, but still needs to be installed. The Dockmate (remote control for anchor, bow and stern thruster and main engine, for single-handed docking) is almost fully installed.

We are still considering an electric or other solution to help lower the mast. Might be something we do next year (if at all).

On the autoprop: it fits in the propellor window, so that's the good news. The less good news is that the prop window needs to be enlarged at the cost of a little bit of keel and rudder, that would need to be removed. Makes the operation a bit more costly than expected, especially since the autoprop is not cheap.

Next step is an upgraded calculation of the true gains we will achieve with the autoprop, so we can offset it with the investment. Hope that makes sense.

Plans? In May we'll leave for a few months of cruising in Scandinavia. From Holland to the top of Denmark, then starboard to Sweden. Return trip via the Danish archipelago and the Kieler Canal in Germany. End of August and beginning of September we'll join a flotilla that'll sail over the North Sea and Channel via Belgium to France (the Seine mouth, to be precise), and back.

Regards, Edwin & Veronika

I've heard of maintenance challenges with the autoprops with relatively minor issues leading to significant vibrations. This is with smaller, saildrive mounted units but I was not impressed.

Thanks for sharing. There is more maintenance involved, for sure. It needs greasing once a year and a re-assembly every 2,000 hours.

Personally, I am not anxious of damaging the prop, as our ship has a "enclosed" propellor window: the keel continues under the prop, the rudder is held in place from the top and from the bottom.

Regards, Edwin.

MacPhid said:

If I understand it correctly, a Variable Pitch Prop allows you to run higher pitch at lower rpm’s to allow the prop curve to get closer to the HP curve allowing more speed (prop rpm)at the same rpm or same speed at lower rpm (but more actual HP input). Allows the engine to operate more efficiently. At WOT the pitch reduces to what would on a fixed pitch prop be the closest to max rpm and HP/prop curves meet. It’s all about loading the engine more efficiently through its operating range.

James

Click to expand...

Well said, and a bscf "map" will show this plotted for rpm vs torque across the engine's operating range.


The theory is that you are moving operation from one point on the fuel map to a more efficient point on the fuel map. But that's theory, and the actual fuel map for the engine is reality. I'm wondering if this is being done with a fuel map in hand knowing what results to expect. In my experience, these fuel maps are very hard to come buy, so it's nearly impossible to quantify the expected gains - something I'd personally want to do before spending a bunch of money to change propping. Scania published the bsfc numbers for my engine, but it's only along the prop load curve. The bscf is nearly flat across the whole normal operating range, suggesting there isn't much to gain by moving around on the map. But it's map a full map, so still leaves you guessing.

Salty Pelican said:

Thanks for sharing. There is more maintenance involved, for sure. It needs greasing once a year and a re-assembly every 2,000 hours.

Personally, I am not anxious of damaging the prop, as our ship has a "enclosed" propellor window: the keel continues under the prop, the rudder is held in place from the top and from the bottom.

Regards, Edwin.

Click to expand...

It wasn't an issue from being struck, it was just low tolerance to factors of wear or growth. What I heard of as problematic was the blades becoming loose on their individual shafts, either due to bearing wear or improper tension (assembly) and this in turn causing a vibration. The other issue was barnacle growth making a much more significant challenge to balancing due to their self pitching nature, if the foil shapes of each blade are no longer matched, the prop will vibrate significantly.

More info, numbers, and calculations on the autoprop

First calculations on the autoprop are in. Fresh from Brunton's HQ. That's for our current motor yacht "Moonshine", a 50 feet steel water displacer with CE-A certification, build by Jetten in the North of the Netherlands. With a Vetus Deutz 170 hp inline six diesel.

At 7 knots, we might be able to save 37.5% in fuel, resulting in, well, 37,5% more range. That's pretty impressive. At 8 knots the calculations estimate savings above 40%, relative to our current use case. A cruising rpm of 1,500, that we often use, results in an increased speed of 7.75 knots vs. the current 7 knots.

I am having all the numbers re-evaluated as we speak, by the way. I know the calculations are no guaranty, but I want to understand the info behind it (fuel map, prop info, ship's weight, LOW, average draft of canoe body, practical info, etc.). If we can get the current fixed prop calculations as close to where they are in practicality, that'll result in a better prediction model.

So far, the first indications show a range increase of 3000 to slightly above 4000 kilometers. Fuel burn at 7 knots - for longer crossings - would become an estimated 2 Nm per gallon.

MVTanglewood: yes, we have the actual fuel maps. I feel they are essential to make predictions that actually make sense and that can be expected to translate into real life gains.

More technical info on how the autoprop works its magic:


Regards, Edwin.

The Autoprop sounds intriguing, although the marketing mostly appears to be targeting sailboats. From a realistic perspective however, cost is usually a big factor with boat owners. I see online that a 22" model costs about $6500. However, for most "trawlers" we'd be looking for something in the 36" to 48" diameter range. So if the cost is (guessing) about $20k to $25k, then that is a important thing to consider. Twenty grand does buy alot of fuel, or even a variable pitch prop, which is a well-known and proven option.

Appreciate if you could share some actual numbers for your new build. Thanks

Hemisphere Dancer, a powerboat that cruised South-America, has changed to autoprops and is very happy with the results and outcomes. Here's the read of their experiences & learnings:

http://mayrik.com/images/ArticleAutopropPM.pdf

Hi Mako, I agree that it is a hefty investment that needs to be offset with how much fuel it will save. But that's just one of the metrics. The other one, which is quite important to us, is the added range. This allows us more use-cases for our boat.

Anyhow, the autoprop we need costs EUR 8.000,- ex taxes. That'll be around 10k including taxes in North-America.

Regards, Edwin.

Update on "Moonshine's" big overhaul!

With the wish of splashing the ship in March and going on an extensive cruise to Scandinavia in April, we decided to postpone some projects on "Moonshine". Which one? The autoprop and hullvane and added swimming platform. There's more than enough new kit on the boat we need to test out before we can make better informed follow-up decisions. That, and we don't want to compromise on our time on the water. We'd rather be in sooner and sail her than have her on the hard and loose part of the spring/summer/early autumn season.

Yeah, we visited the SBM Shipyard today and discussed the above and more. The other work is progressing well. New batteries, new alternators, completely new electrical wiring, new radar, autopilot, plotter(s) and dockmate ...

The yard has started building-in the airconditioning. The anchor chain will be upgraded from 30 meters (100 feet) to 50 meters (160 feet). We added four solar pannels. And the underwater-ship got a double coat of antifauling.

The yard will put the boat back in the water in the first week of March. The electrician then needs an additional 3 weeks to install and test various systems. Last week of March will see both calibration of the Raymarine systems as well as the dockmate and a three day test sail by the yard.

We'll first sail "Moonshine" again ourselves first week of April. Near the yard, testing out all systems. Second week we'll take family on a 4-day inland cruise. Third week'll see more testing. Final week of April will see us leave for Northern Denmark. 41 to 48 hours out on the North Sea. After that the Lymford Fjord across Denmark and over to Sweden, back down to Denmark and Germany, and back through the Kieler Kanal to the North of the Netherlands. Total trip will take a month and a bit!

Very exciting times ahead! Pictures of the "current state of affairs" underneath!

Regards, Edwin & Veronika.