Semi-displacement and Full Displacement Hulls

Hello all,

I just joined the forum and this is my first post. I am not trying to start a fast boat/slow boat debate here, these are three real questions I have.

I sold my 2012 Beneteau Swift Trawler 34 last month, after two years of limited cruising, and I am planning for what will probably be my last boat. My wife and I have enjoyed several weekend trips, one with 4 teenagers, as well as day cruises, and we realized the Swift Trawler3 4 would not be the retirement boat we thought it would be (it had a number of craftsmanship issues, too). I homeport on the Delaware River in New Jersey.

I have been looking at the Grand Banks 43 EU with it's semi-displacement hull, and the Kady-Krogen 44 AE and Norhavn 43, both with full displacement hulls. All three are beautiful boats, but I realize I am mixing one apple with two oranges.

Here are my three questions: (1) Why don't I see many Grand Banks style boats doing the Big U type of cruises from Maine to Alaska? (2) Is the semi-displacement hull that bad for cutting across the Caribbean and coastal cruising? (3) Is the large flying bride and wrap-around bench seating of the Grand Banks not very important to the cruising couples that spend weeks and months aboard their boats?

I like the idea of a pilot house, which the Krogen and Norhavn boats both have, but I like the dual Zeus drive engines with the joystick docking better than a single engine with bow and stern thrusters and a kicker.

I spent most of my underway time up on the Swift Trawler's flying bridge with friends around the bench seat and table, either on the Delaware or in the Chesapeake. To my eye, the optional flying bridge of the Norhavn is too small, and I can't get past the Krogen having only one head, with an option for another 1/2 head. I am leaning towards the Grand Banks since inter-coastal cruising is the type I will do probably do most, and the ocean crossing capabilities of the Krogen and Norhavn are not needed. I'm just wondering why the vast majority of boats I see in magazines and on the Internet that are up in Alaska or doing the Big U are of the Krogen/Norhavn style. Those are also cruises I would like to consider.


Thanks for your time,
Sam

Sam,
Grand Banks builds great boats, and they are perfectly suited to coastal and ICW cruising in a hurry. But GB's and probably all other semi-D boats can not stand up to breaking seas; the lovely picture windows won't take it. You won't want to get more than a day or two away from a good weather forecast on such a boat.

Most retirees find that the extra expense of a faster semi-d boat is a poor trade for them. Larger engines cost more, take more space, cost more to maintain and always burn more fuel at any speed. I think faster boats are great for the poor unfortunates who need to get back to the office on Monday morning.

Mark Richter. Winnie the Pooh, 46' troller
Ortona, FL on the Okeechobee Waterway

You sound like a go fast, semi-displacement kind of guy with some Carribean ambitions. You like comfort, convenience, ease of handling. Go with a GB with the Zeus drives that you like.

It will go slow, but it will burn more fuel at the same speed as its equivalent full displacement sister. No big deal. If you can afford a GB 48 Euro, you can afford the extra fuel.

As others have said, stay within a couple of days of a bail out port. The GB can do the Carribean just fine, but you are going to have to take the "Thorny Path" (Bahamas, Turks and Caikos, N shore of Dominican Republic then across the Mona Passage to Puerto Rico) rather than the blue water passagemakers route- east until about Bermuda longitude then south to the first island.

But you will see more Krogens and Nordhavns in the Caribbean just like in Alaskan waters. For good reason- they can go anywhere, almost any time. With the GB you can only go where there is a bail out port nearby and only in decent weather.

David

First off, I have no experiences on East Coast waters, only the PNW. I think the numbers of GB's far exceed the total of Nordhavens and Krogens combined that cruise the waters out this way. I personally feel boating whenever is not necessarily the best idea as weather is THE determining factor on comfort levels in most boats. In the PNW "Bail out ports" are really not too far off. I can only think of a couple of crossings such as the The Queen Charlottes and the Gulf of Alaska that particularly demand attention to weather windows. But even short crossings such as the Strait of Georgia are weather dependent, you do not want to cross in a bad mix of wind and tides.

Which boat is better? Cannot answer that. We love our GB and all the interior and exterior options it affords and it is only a 36. Good luck in your search.

Well, first, to correct one misconception. You will not see more Nordhavn's and KK's in Alaska than Grand Banks. Grand Banks have great popularity in the PNW. Now when you get to crossing the Gulf in Alaska and running outside, yes fewer Grand Banks. But much of Alaskan boating is the inside route to the southern regions.

As to the Great U, you don't seen many GB doing that, but not a tremendous number of any boat. For a GB it's a long run and many who do it are looking for better fuel economy plus greater range. I'd expect more Nordhavn's and KK's transiting the Panama Canal, but GB's also do it on occasion. Also a GB would certainly have to choose weather windows a bit more carefully but then most Nordhavn and KK pleasure boaters also choose carefully. From Texas to California would be the most challenging area.

As to what you see in magazines, GB has done a poor job of promotion the last few years so you see them less in general. Nordhavn may have the best promotions department of any builder.

Going back to your needs. First it's what is best for 90-95% of my usage. Then will it accommodate the remaining part even if not as well as some might.

I'd step back a second from brands to specific needs and requirements.

You're not the first Swift Trawler customer to be disappointed, although they also have happy owners. I think in your case there were two issues. First, the annoying quality control issues. Second though the size and design of the boat vs. your family and needs. Now you're looking in a range that seems slightly larger but, in fact, has nearly double the volume. The boats you're looking at are all significantly heavier and are all better able to handle rougher waters.

So step back and define your needs carefully, then select to meet them. How much speed to you need? Desire? How many cabins and heads? Galley up or down? Bridge? Then I think you get into some real "ride comfort" issues. This isn't just handling rough water. Where do you like to be while underway? Do you need upper and lower helms? And then the issue of stabilization. You'll see many here adding paravanes. Well, 43 foot boats are large enough to consider stabilizers too, especially on a new build. I can tell you if it was my "last boat" which we hear all the time and then people have another "last boat", but assuming it is, I would have stablization both for rest and underway. It changes so much. Makes anchoring more pleasant. Makes cruising more as well. Yes, expensive and requires maintenance, but for me it's an absolute. Then a question of whether the space is designed for your needs. Finally, docking and handling. Personally, Zeus drive does nothing for me, but it might for you. However, I do have twins with thrusters and with joysticks for docking and love them. Still docking is to me not a reason to go to twins. A single with thrusters and a joystick (although it isn't necessary just something I like) can be docked easily. I personally would want bow and stern thrusters on a single but not a necessity by any means. My reason though for choosing twins has nothing to do with docking.

As to the Zeus drives, well consider your cruising areas and maintenance. I've chosen traditional drive systems that every mechanic at every yard is familiar with and knowledgeable about. But then I do Bahamas and other areas a lot. We admit to being a bit of the non traditional trawler types and many here would call us traitors to true trawlers. But for us, we like the speed that a GB would give you. That really becomes a consideration. Are you happy with a single engine KK or Nordhavn or other that will give you the best economy and cruise at 8-10 knots. Or by comparison, a 43 GB Heritage with twin Cummins that will cruise at 20 knots. Now the GB will also go at 8-10 knots and get excellent fuel economy at those speeds but not equal to a single Nordhavn or KK. There is a trade-off. A 43 GB is probably going to give a little over 1 nmpg at 8 knots and 1.5 or better at 6 knots.

There are also factors of maintenance and upkeep to consider. Part of the beauty of GB is all the teak. Part of the pain of GB is all the teak.

Are you looking at a new build, a late model, or an older boat?

Have you seen any Selene? GB is OK for whatever you want to do but crossing oceans.

Gee, I've cruised SE Alaska a half-dozen times on cruise ships. Rarely see a recreational vessel outside immediate areas of harbors, but then the area is so large. Did spot this one far from any harbor:



A bit more typical scene (people got to make a living):

Mark is the pic w the Fisher near Wrangell?

manyboats said:

Mark is the pic w the Fisher near Wrangell?

Click to expand...

For the first picture, it's in Tracy Arm, heading in the direction of the glacier (toward east).



The second is near the entrance of Glacier Bay, boats heading west.

Don't by anything right now. That's my advice. There is a big difference between a Beneteau fast trawler and a GB, and then again between a GB and a Nordhavn. As a KK owner, I can say there is a big difference between a KK and a Nordhavn. Spend the money on some bare boat charters instead for the time being and get a feel for what you really want.

I like the KK. The pilothouse is much bigger than Nordhavns of equivalent length. I found the Nordhavn 43 cramped in comparison with the KK42, and certainly would be in comparison with the KK44. As for the flying bridge, we never use ours. All the electronics are in the Pilothouse. We just open windows when the weather is fair.

It took us a while, but we really felt we had found the boat we wanted when we finally found her. You will know too,


Jim
Sent from my iPad using Trawler Forum

I'm for a full displacement hull, hence the reason why I purchased the Gulfstar 36. Not in the same boating class as the 3 mentioned above but I'm happy with her so far.
Bill

Your not going get 8-10 knots out of a 43 Nordy, more like 7.0-8.0. We average 7.2 on our 47.

N4712 said:

Your not going get 8-10 knots out of a 43 Nordy, more like 7.0-8.0. We average 7.2 on our 47.

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True. Just found a review and it gave a 43 a cruise speed of 7 knows and a maximum speed of 8.5 knots with a Lugger L1066T which produces 170 hp at high output and 135 continuous.

As others have said take the process slow and really think out how you will use the boat prior to making a final decision. That being said you also need to consider the few times you will be outside and in open waters for an extended period of time and what you are willing to put up with. Having owned two Nordies with stabilizers and now a smaller N35 w/o stabilization our next boat will likely be with stabilizers. Last month we took the N35 "outside" in small 2'-3' mixed swells and 15 knot breeze and got bounced around a little more then the first mate was willing to tolerate. She could see the difference of making a gourmet lunch on the stabilized boat in worse conditions then this to holding on and looking back at land. While the boat was fine and I was actually enjoying the ride taking a little spray over the bow it would have become uncomfortable if we were going anywhere for 10 hours+.

I guess we are a little spoiled but we look at stabilizers as an added safety factor since it reduces fatigue. Even if you do not plan to cross an ocean but do plan to spend some serious time cruising I would look at the KK or Nordhavn's a second time. No boat is perfect and there are compromises you will have to make along way but getting the safest boat you can afford is the most important step you can take.

John

As is obvious I have a Krogen so I am biased on the full versus semi-displacement, but also I have been in the Caribbean since 2008. Excluding local boats I have yet to see/recognize a semi-displacement boat with the exception of a large Nordic Tug kept in the BVIs which every year or so comes down to the northern Windward islands.

Very good cruising conditions are 5 to 6 foot waves on the beam with 15 kt winds. Almost always on the beam. You and the boat must be ready for this.

Grand Banks are great boats and for coastal cruising they are very safe and comfortable. With twin engines they are even easy to dock. For use in the ICW or Chesapeake the semi-displacement boat would be fine, perhaps the preferred boat. On the north coast of the Dominican Republic (island hopping) with the swell from the north even stabilized full displacement hulls were less than comfortable.

Then again your next boat does not have to be your last boat. Perhaps cruise for a while with the Grand Banks, do the Great Loop, and then if you are still interested in going to the Caribbean/ Alaska get a full displacement hull.

Bay Pelican said:

Grand Banks are great boats and for coastal cruising they are very safe and comfortable. With twin engines they are even easy to dock. For use in the ICW or Chesapeake the semi-displacement boat would be fine, perhaps the preferred boat. On the north coast of the Dominican Republic (island hopping) with the swell from the north even stabilized full displacement hulls were less than comfortable.

Then again your next boat does not have to be your last boat. Perhaps cruise for a while with the Grand Banks, do the Great Loop, and then if you are still interested in going to the Caribbean/ Alaska get a full displacement hull.

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I wonder if there's really that huge a difference between a stabilized full-displacement hull and a stabilized semi-displacement hull. Measurable? If so, how much delta is due to hull form, and how much due to the stabilization system?

And then would it be better to just buy whatever boat suits your living requirements -- the one you like -- and just "get over" any differences in roll? Pick decent weather windows for transits?

Our yard does most of the powerwashing for the next door and on-site Fleming fleet, most are stabilized. I've seen pictures of Hatteras and Viking MYs that are stabilized. Presumably there are some stabilized GBs, too...

-Chris

What Chris said, expecially regarding picking your weather. There must be a wave size beyond which stabilizers cant do any more. I wonder what the makers specs say about that.

Keep in mind that wide hard chine boats and/or just wide boats w little dead rise are hard to stabilize. The stabilizers are fighting against the very high righting moment of the boat that gives the boat it's very high initial stability. A GB will make stabilizers work very hard whereas a KK with her narrower and more barrel shaped hull will not require much input from her stabilizers to achieve a good ride.

These pics are of the Dixie II, a fish boat in Alaska and she's a good example of a good hull to stabilize. As can be seen she is paravane stabilized and the stabilizers are needed to safely work 12 to 15hrs a day on deck in open water. The fish are 20 miles out now so they practically live 25 miles offshore in SE Alaska.

With a hull this deep and round the righting moment is very low and not much force is required to keep her from rolling. Not much weight on the gunn'l is required to drop the gunn'l either. Step onto the gunn'l of a GB and most likely nothing perceivable will happen .. or just barely so. Step onto the gunn'l of Dixie II and nothing instantly happens but in a moment she moves under your feet. And when the movement stops you could depress the gunn'l an inch. You're amazed just your weight moved the big boat that much. A full disp trawler hull like a KK or a 40' Willard will be a stiff boat compared to the fish boat in the pics here but still much closer to the fish boat than the Nordhavn or GB trawler yacht. So to be very effective the stabilizers on the later must be large, heavy and expensive. And won't even come close to stabilizing as well as the fish boat.

This thread is about the differences between the FD and SD hulls and their ability to be comfortable and safe at sea for their owner and his family and friends (I assume). The yacht hulls will never be as stable as this fish boat but will be very acceptable compared to the yacht w/o stabilizers. But in 4 or 5' seas the yacht can be very comfortable to violently rolling depending on one's course relative to the seas or other considerations like where you are in the boat fore and aft or up or down. So a little seamanship can go a long way but some confused seas hardly respond to course changes at all and you've just gotta go for the ride.

But there's no argument that when the waves get big a stabilized FD hull is best.

Picking a weather window is a great rule, one should always follow. However, in December, January and February in the eastern Caribbean (the height of the season) that means going when the waves on the beam are slightly less than 2 meters and that is not frequent.

ranger42c said:

I wonder if there's really that huge a difference between a stabilized full-displacement hull and a stabilized semi-displacement hull. Measurable? If so, how much delta is due to hull form, and how much due to the stabilization system?

And then would it be better to just buy whatever boat suits your living requirements -- the one you like -- and just "get over" any differences in roll? Pick decent weather windows for transits?

Our yard does most of the powerwashing for the next door and on-site Fleming fleet, most are stabilized. I've seen pictures of Hatteras and Viking MYs that are stabilized. Presumably there are some stabilized GBs, too...

-Chris

Click to expand...

If the stabilizer companies just sold stabilizers to folks with Full Displacement hulls, they would soon be out of business.

Everybody with a FD hull is going to say the only acceptable boat for any area is a FD hull. Thats just how people are.

Everybody is going to say their waves are bigger, or more constant than other areas waves. Thats again just how people are.

The fact is that actual real cruisers can, have, and will continue to cruise in the open ocean in all sorts of boats, and they have a good time doing it.

Just this last weekend I posted here on TF while I was in a actual bouy measured 6.2' beam sea. The dominant wave period was 10 seconds, and the average wave period was 6 seconds. I was in my BAYLINER. Not a "blue water" boat by any measure. Yet, I was there and did a 40NM open ocean crossing. I was comfortable because I used my Semi Displacement hull to its advantage. I used my large engines to their advantage. A little throttle and I got the ass end of the boat pushed down a bit and the ride settled out just fine for me, the admrial and our dogs. I surfed the net, and she watched a movie. No big deal.

Think of this. There are a series of books written by Melanie Wood that document her and her husbands accounts in their 38' Bayliner. They started in Canada and are now in Honduras. Nobody would dream of arguing that a 38' Bayliner is a great open ocean boat, yet these people did it, and had a great time.

So, my advice is that the actual boat is MUCH less important than we think here sitting behind our keyboards. Pick a boat you're comfortable with. Pick a boat you can afford. Pick a boat that doesn't delay your date to start cruising because it requires you to work later in life to pay for. Then GO CRUISING.

If you want, and can afford stabilizers, get them. You'll be more comfortable. If the 50K for stabilizers will delay your departure, forget about them and set sail. You will not stop the clock of life, and I guarantee you'll be happier cruising in the boat you can afford than sitting at your desk at work for several more years paying for the optimum boat.

ksanders said:

If the stabilizer companies just sold stabilizers to folks with Full Displacement hulls, they would soon be out of business.

Everybody with a FD hull is going to say the only acceptable boat for any area is a FD hull. Thats just how people are.

Everybody is going to say their waves are bigger, or more constant than other areas waves. Thats again just how people are.

The fact is that actual real cruisers can, have, and will continue to cruise in the open ocean in all sorts of boats, and they have a good time doing it.

Think of this. There are a series of books written by Melanie Wood that document her and her husbands accounts in their 38' Bayliner. They started in Canada and are now in Honduras. Nobody would dream of arguing that a 38' Bayliner is a great open ocean boat, yet these people did it, and had a great time.

So, my advice is that the actual boat is MUCH less important than we think here sitting behind our keyboards. Pick a boat you're comfortable with. Pick a boat you can afford. Pick a boat that doesn't delay your date to start cruising because it requires you to work later in life to pay for. Then GO CRUISING.

If you want, and can afford stabilizers, get them. You'll be more comfortable. If the 50K for stabilizers will delay your departure, forget about them and set sail. You will not stop the clock of life, and I guarantee you'll be happier cruising in the boat you can afford than sitting at your desk at work for several more years paying for the optimum boat.

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ksanders wrote;
"Everybody with a FD hull is going to say the only acceptable boat for any area is a FD hull. Thats just how people are."

Is that the reason passagemakers are all or almost all FD boats?

I think we people here on TF are a LOT more objective than your quote above says. FD is far better at sea but I suppose what I say is meaningless since I have a FD boat. Hmmm.

manyboats said:

ksanders wrote;
"Everybody with a FD hull is going to say the only acceptable boat for any area is a FD hull. Thats just how people are."

Is that the reason passagemakers are all or almost all FD boats?

I think we people here on TF are a LOT more objective than your quote above says. FD is far better at sea but I suppose what I say is meaningless since I have a FD boat. Hmmm.

Click to expand...

Eric

What you personally say is not meaningless. I spoke in generalities about people, and I stand behind my comments. People with FD hulls in general make comments that indicate their belief that you cannot cruise in the open ocean unless you have a FD hull. Those beliefs and those comments are factually incorrect.

To answer your question, passagemakers are almost all FD boats because of two reasons.

1. A FD boat has better fuel economy, and in general can carry the fuel necessary for crossing oceans.

2. A FD boat can in general withstand seas of a larger magnitude than a SD boat. This is necessary for passagemaking because our current technology only allows for an approx 72 hour firm weather forecast duration. Therefore a passagemaker must be able to operate in whatever sea state might happen.

We all need to remember and take note that cruising anywhere along a coastline, or between islands is not passagemaking. It does not require the fuel range or the seaworthiness that crossing open oceans requires. Therefore it does not require a FD boat, or a boat capable of crossing oceans.

I guess being one of the lesser objective people here on TF...

All one has to do is a quick perusal of general info to see as boats get larger..especially above the 65 range to see passage-making semi-displacement is not only more common but a desirable trait.

Pure numbers show that the smaller the vessel, the more of the total weight has to be reserved for fuel, food and water. In the constant trade off to keep the size small, room and weight attributed to the basics forces the boat further towards the pure displacement design.

But pure displacement has very little to do with absolute seaworthiness...just capacity. The more a boater is willing to forgo certain amenities the better the chance that a smaller hull could easily be a semi-displacement passagemaker.

Lot's of "record setters" have crossed in all kinds of vessels...it's just a matter of what you are willing to do without or how small you want to stay.

psneeld said:

I guess being one of the lesser objective people here on TF...

All one has to do is a quick perusal of general info to see as boats get larger..especially above the 65 range to see passage-making semi-displacement is not only more common but a desirable trait.

Pure numbers show that the smaller the vessel, the more of the total weight has to be reserved for fuel, food and water. In the constant trade off to keep the size small, room and weight attributed to the basics forces the boat further towards the pure displacement design.

But pure displacement has very little to do with absolute seaworthiness...just capacity. The more a boater is willing to forgo certain amenities the better the chance that a smaller hull could easily be a semi-displacement passagemaker.

Lot's of "record setters" have crossed in all kinds of vessels...it's just a matter of what you are willing to do without or how small you want to stay.

Click to expand...

I would further this discussion and your comments by saying that a Semi Displacement hull, coupled with engines of adequate size are often more desirable than a FD hull for island hopping and coastal cruising.

A SD hull and large engines means you can get somewhere much quicker. This can be a real advantage in island hopping and coastal cruising.

Just this last weekend we did a 40 mile open ocean crossing. At 14 knots we made that crossing in three hours. At 7 knots it would have been 6 hours.

The concept here is that you could make the argument either way for island hopping and coastal cruising.

The bigger point is that people need to realize that if they keep dreaming of the larger or more capable boat they might never actually leave port.

We could all trade working years for a larger or more capable boat. But how many years do we have to trade?

ksanders said:

I would further this discussion and your comments by saying that a Semi Displacement hull, coupled with engines of adequate size are often more desirable than a FD hull for island hopping and coastal cruising.

A SD hull and large engines means you can get somewhere much quicker. This can be a real advantage in island hopping and coastal cruising.

Just this last weekend we did a 40 mile open ocean crossing. At 14 knots we made that crossing in three hours. At 7 knots it would have been 6 hours.

Click to expand...

I was just addressing the myth of SD/FD and passage making.

My friend just came over from sail and bought a 49 Meridian.

He could have bought a Nordhavn or Fleming ...probably for cash and would have had plenty to cruise on. He's not going to Europe or even probably all the way down island in the Caribbean...wise choice for him...for a lot of reasons.

Certainly with the right features built in, and as long as they work as advertised, it really doesn't matter what hull form crosses an ocean...as long as the skipper/crew is up to it also.

But I'm not so naïve to say for the typical 35-45 foot range many of us are in...FD is probably an easier choice to outfit for serious long range cruising ....beyond just coastal cruising.

Ranger42c wrote
"I wonder if there's really that huge a difference between a stabilized full-displacement hull and a stabilized semi-displacement hull. Measurable? If so, how much delta is due to hull form, and how much due to the stabilization system?

If the system (active fin) is part of the design and called for a NA the system would be much more effective and/or smaller on the FD boat. Much less stabilization will take place on a low deadrise hard chine boat for a given size system. So yes to your question is there is a very noticeable difference and the difference will vary a lot because the differences in hulls and what people think a FD hull is. Our archives will show that is not clear.

Kevin I do agree w your post#23.
I could have crossed the Cascade Mountains w my ultralight. And I can ride a motor scooter on the freeway too. Dosn't mean either is a good idea. Many people have rowed a boat to SE AK. And paddled kayaks. Or run jet skis. None of these vehicles were meant to do those things but the risks vary more by whose doing it that the vehicles themselves .... As psneeld said or implied.

Good advice Kevin though most wont believe you.

manyboats said:

Keep in mind that wide hard chine boats and/or just wide boats w little dead rise are hard to stabilize.

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I'm not sure if agree with that. The majority of stabilized non-commercial boats are hard chine I'd say. And the stabilizers work just fine.

And considering the way a full displacement boat would behave roll wise in a beam sea you could say it would cause the stabilizers to work harder to dampen its rolls.

Where as a hard chined boat is stiffer and resist roll so the stabilizers may not work as hard at least initially.

Yup everyone has to have a passage maker though they will never cross oceans.

IMO the best boat less than 100' for crossing oceans is a sailboat.