Semi-displacement Ocean Crossing

[fgarriso]

Hi everyone. Searched and found a few things but not exactly i guess.

Are there any semi displacement trawler brands that can safely cross oceans?

I understand the benefits of full displacement for long distance but can you cross oceans with a Fleming, Selene, etc by regulating speed? Can it sip fuel for long distances? Will a semi displacement hull sacrifice safety for speed?

I am a huge Nordhavn, Diesel Duck and Bering fan and want to make long passages when I finally purchase a boat capable of these crossings. I also realize that ocean crossings will be a relatively small amount of my boating life. The rest of the time I wouldn't mind going a little faster than 8 knots.
Thanks

Stability.....Stability....... Stability !!!

 

[bpgt3]

The longest leg of the southern route across the Atlantic is roughly 2200 miles...Bermuda to the Azores. At displacement speed if feel the Flemings and Selene's have the range to do that.

A big BUT is the weather window. Research is essential in learning trends, prevailing winds and currents, etc. Guys that do the crossing in 6 foot boats are nuts but by controlling the variables you can and reducing the impact of the ones you can't, it can be done in a 6 foot boat.

Another question with the differences in FD and SD is the ability to right itself if knocked down by a wave. Because of the ballast in FD it would seem to make sense it would recover more consistently than a SD hull.

 

[Sailor of Fortune]

I saw a documentary that the commercial intrigued me with the trailer. A Surgeon turned yacht capt was going to take his large yacht from the Med to east coast US.... Turns out it was on a yacht transport ship....WTF? They made the drama though, storm outside of harbor....before the ship loaded the yachts..Foolishness

 

[FWT]

Go up and read the tagline below post of Caltexflanc

"There's the Right Way, the Wrong Way, and what some guy says he's gotten away with"

That applies perfectly to this topic.

Slocum circumnavigated in a 20-something sailboat ill-suited to the trip. The man had serious skills. His head was a bucket. His provisions were a bag of dried beans and a sack of onions. But if you are going to do that, ask WHY? Few cross the Atlantic in a trawler. Very few. If you have something to prove, then fine.

Maybe you will be the guy to get away with it.

 

[bpgt3]

Not sure if these graphs worked but they show the fuel burn and range of the Fleming 65. At roughly 7.5 knots the range is 2500 miles. That's in a vacuum. Weather, currents and wind play a huge role.

Bring the speed down to roughly 7 knots the range goes up to 3000 nm.

 

[MurrayM]

The Elling E6 is self righting...think Columbia River bar or west coast of Vancouver Island rescue boats with ocean crossing potential. Serious inherent stability and if you add a gyro stabilizer you should be able to knock more than a few days off. Just one option...

 

[AusCan]

I’m far from an expert on the subject of hull design but I wold think that an FD hull is inherently safer in angry sea conditions.
I’m not saying that an SD boat can’t cross oceans relatively safely but a FD boat would be safer with all other factors being equal.

Look at how many 30 - 40 ft FD boats do it. Mostly sailboats but not all. If the SHTF they can lay ahull. I certainly would want to try that with a 30 ft SD boat regardless of how solid it is built.
In big following seas the upswept stern will lift an FD boat in a much more controlled manner. Without a doubt, this has to be an advantage.

The only advantage I see with a SD hull is the option of more speed prior to the seas getting really bad. Whe the sea gets crazy then that option is limited and possibly more dangerous.

 

[MurrayM]

Found a reference that said the Elling E6 could cross the Atlantic "if speed was reduced to single digits".

Moving from 7.5 to 9 knots takes about 2 days off a 2500 mile crossing and 8.5 knots would take one day off. Does that matter? Depends, I guess.

 

[dirtdoc1]

Hi everyone. Searched and found a few things but not exactly i guess.

Are there any semi displacement trawler brands that can safely cross oceans?

I understand the benefits of full displacement for long distance but can you cross oceans with a Fleming, Selene, etc by regulating speed? Can it sip fuel for long distances? Will a semi displacement hull sacrifice safety for speed?

I am a huge Nordhavn, Diesel Duck and Bering fan and want to make long passages when I finally purchase a boat capable of these crossings. I also realize that ocean crossings will be a relatively small amount of my boating life. The rest of the time I wouldn't mind going a little faster than 8 knots.
Thanks[/QUOT

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I think that you need to include size with that question. Trawlers with full displacement hulls have ballast and because of that they are self righting. I don't think semi-displacement boats are self righting because they don't have ballast. I'm not talking about a few lead bricks in the bilge for trim.

Cheers!

 

[psneeld]

Beam vs Ballast for Stability


Whether they are displacement types, semi-displacement types, or planing types, if given sufficiently strong superstructure with robust windows, with hatches and doors having adequate WT seals, most power boats will have an enormous range of positive stability. A large portion of those power boats will actually be fully self righting, which is much more than can be said for the majority of sail boats.
The key is to keep the water out...

 

[Lepke]

Any powerboat that can cross oceans is going to be big and long for a decent hull speed. It has to be big to carry enough fuel. And it's probably going to be single screw. If you're on a strict budget, you should look at converted fishing boats. They have the tanks, usually single screw, made for the ocean and heavier built than most yachts. They spend their life on the ocean and the bad designs are on the bottom somewhere.
Crossing from San Diego to Hawaii in my boat takes about 10 days @10kts and 2000 gallons. And I carry 500 more gallons in case I have to dodge a storm. In ten days a lot can happen in weather. It's a lot cheaper to fly and stay at a hotel. Most people get terribly bored on an ocean crossing.

 

[bpgt3]

Go up and read the tagline below post of Caltexflanc

"There's the Right Way, the Wrong Way, and what some guy says he's gotten away with"

That applies perfectly to this topic.

Slocum circumnavigated in a 20-something sailboat ill-suited to the trip. The man had serious skills. His head was a bucket. His provisions were a bag of dried beans and a sack of onions. But if you are going to do that, ask WHY? Few cross the Atlantic in a trawler. Very few. If you have something to prove, then fine.

Maybe you will be the guy to get away with it.

Pretty sure I have nothing to prove. The idea of crossing oceans has fascinated me my whole life. I have asked WHY several times. WHY would i want to cross oceans. Probably because thats one way I can get my boat to the other side. I wouldn't do it in a 6 foot boat or even a 20 foot boat. I'm Also relatively sure I'll have a few more provisions than a few onions and beans.

Not sure why motives are a question in this discussion.

And I'm not trying to get away with anything. Just curious.

 

[hollywood8118]

And I thought I had big cajones!
I have swam mid ocean between Mexico and the Marquesas but I cannot imagine attempting a prop swap mid ocean.
Better have a big bag of spare nuts and keys... and another prop too.
Hollywood

 

[Nomad Willy]

Why single screw Lepke?

 

[hollywood8118]

A popular whale watch boat in the PNW had a previous life as a live aboard dive boat in Hawaii. She motored to Washington on her own bottom alternating engines with 55g. Drums on deck for additional tankage.
This is a light 70' cored planing hull that runs around here now at 18kts all day long. So it can be done, but its a bit sketchy for sure.
Hollywood

 

[FWT]

Beam vs Ballast for Stability


Whether they are displacement types, semi-displacement types, or planing types, if given sufficiently strong superstructure with robust windows, with hatches and doors having adequate WT seals, most power boats will have an enormous range of positive stability. A large portion of those power boats will actually be fully self righting, which is much more than can be said for the majority of sail boats.
The key is to keep the water out...

Excellent piece in the link. Saved

 

[FWT]

On the topic of rolling and self-righting:

What comes to mind to me is, what then?

Assuming the boat rights after a roll, it will have spent a minute or so upside down. Does anyone know what happens with a running diesel turned upside down for a minute or so? I don't.

Fuel tanks are unlikely to have been bolted down with the thought the bolts need to support the weight of full tanks, inverted. If those tanks come loose its real trouble.

But ditto for water. Even blackwater.

Batteries coming loose and yanking wires.

What will be damaged from batteries and tanks tumbling around?

Pots and pans spilled out are no issue, but galley equipment? Propane stoves? Will the propane tanks themselves break away?

Seems like you should count on losing the dingy, when you might need it most.

Lots of factors to consider.

 

[caltexflanc]

Some of the, perhaps the most seaworthy blue water boats of all are the purpose built sportfisherman. But they aren't geared to crossing oceans, they are geared to get out to the fishing grounds and back ASAP, which requires incredibly strong structural integrity. But throttled down to hull speed, they'll go from tournaments in the Bahamas to one in North Carolina to Bermuda, each leg non-stop, with aplomb.

Per Psneeld's point, among other things they, minimize points of water ingress such as forward facing windows (none) and port lights (few). They can plow through, unscathed, at 25 knots or more what a mighty Nordhavn will be doing at 7 or 8.

 

[rslifkin]

When it comes to things like engines, you have 2 levels of self righting. One involves possibly needing to kill the engines, taking a few minutes to check fluids and sort things out before continuing. Basically the boat will survive the roll, but it's still a big deal The other level has engines with dry sump oiling, etc and is meant to roll and come up running like nothing happened (think USCG 47 MLB).

 

[FWT]

Pretty sure I have nothing to prove. The idea of crossing oceans has fascinated me my whole life. I have asked WHY several times. WHY would i want to cross oceans. Probably because thats one way I can get my boat to the other side. I wouldn't do it in a 6 foot boat or even a 20 foot boat. I'm Also relatively sure I'll have a few more provisions than a few onions and beans.

Not sure why motives are a question in this discussion.

And I'm not trying to get away with anything. Just curious.

I understand that feeling. I once had it too.

 

[Peter Swanson]

Nordhavn's new line

The new line of Nordhavns can do it, and they are semi-displacement, whether you accept the category or not.

 

[garychurch]

There are a number of EU Class A SD vessels that could make a 2500 nm crossing. Problem on all is fuel capacity and fuel range.

For example, to get a 2000 nm range I would have to run at 6-6.5 knots on a boat capable of 20 knots without unfavorable wind of seas. I carry 2300 gals of diesel but it’s not enough. Can I put another 1,000 gals in bladders on bow and stern? That’s about 7,000 pounds of addition weight that would affect stability. Probably no problem on favorable seas on a 120,000 pound boat. But could be a problem if conditions were not good.

Best alternative .... ship the boat on a carrier.

 

[Nomad Willy]

The new line of Nordhavns can do it, and they are semi-displacement, whether you accept the category or not.

What’s your theory Peter?
QBBL, aspect ratio, hull form/shape, speed length ratio, immersed transom area ....?
What feature on what nordhavans makes them SD?

Exclude the N46 as anybody would class it as FD.

 

[Nomad Willy]

There are a number of EU Class A SD vessels that could make a 2500 nm crossing. Problem on all is fuel capacity and fuel range.

For example, to get a 2000 nm range I would have to run at 6-6.5 knots on a boat capable of 20 knots without unfavorable wind of seas. I carry 2300 gals of diesel but it’s not enough. Can I put another 1,000 gals in bladders on bow and stern? That’s about 7,000 pounds of addition weight that would affect stability. Probably no problem on favorable seas on a 120,000 pound boat. But could be a problem if conditions were not good.

Best alternative .... ship the boat on a carrier.

Only one boat type can do it well ... FD

 

[bpgt3]

What’s your theory Peter?
QBBL, aspect ratio, hull form/shape, speed length ratio, immersed transom area ....?
What feature on what nordhavans makes them SD?

Exclude the N46 as anybody would class it as FD.

He may be referring to the new(er) 59 Coastal.

 

[Nightflyer]

This couple gas fine tuned long distance ocean crossing.

The offer a lot of information on their site.

The extensive list of videos is very interesting also.


https://youtube.com/user/DashewOffshore

 

[DDW]

DDW, it’s about stability (already mentioned). Directional stab, roll stab, pitch stab and range range range and even comfort.

There is no inherent stability advantage in what we think of here as a FD hull form vs. SD. In fact probably the opposite. Many racing sailboats are now much closer to our idea of SD than FD (chines, very low deadrise, flat run). Ultimate stability has a lot to do with superstructure and CG. The superstructure of many trawlers, SD and FD, is suspect in heavy weather. But certainly you can build (and there have been built) SD with strong superstructure. CG can be lowered by ballast, but also by taking the top two layers off the 4 layer cake that many of these designs resemble, lowering the tanks, engine, and batteries, etc. Purpose built, an SD hull could be water ballasted for transoceanic stability, then pumped out - that is the way ships do it. I'll stick to my point - there is no inherent difference between the two hull forms WRT seaworthiness.

Look at how many 30 - 40 ft FD boats do it. Mostly sailboats but not all. If the SHTF they can lay ahull. I certainly would want to try that with a 30 ft SD boat regardless of how solid it is built.
In big following seas the upswept stern will lift an FD boat in a much more controlled manner. Without a doubt, this has to be an advantage.

Modern sailboat sterns look an awful lot like SD trawlers. They cross oceans routinely. More than a few modern sailboats are planing hull forms - nearly all the racing ones are. Lying ahull used to be something people would do but it has greatly fallen out of favor due to a large body of experience (and tank testing) suggesting it is a bad idea - regardless of hull form. At Southhampton University they proved that a boat abeam to seas can be capsized by a breaking wave equal to (or a bit less than) its beam - and hull form made no difference. The explanation is in breaking wave dynamics which make stability almost a don't care at a certain wave size. A much better passive storm survival tactic is to lay to a parachute sea anchor or Jordan series drogue. Active tactics are better as long as you can stay awake, the problem here with most trawlers is they steer poorly due to small rudders (compared to sailboats).

 

[FWT]

Great points. All of them.

That answers hulls. But many coastal cruiser SD's don't have window strength, and so forth.

 

[Caballero II]

My DeFever 48 LRC is considered SD by some but when you take a closer look at her hull I’d say she’s FD. Either way she has transatlantic range and capability no doubt. I’d definitely add fish to keep the crew happy though.

OK, we are throwing around these abbreviations (SD vs FD) quite liberally here. Let's have a quick redefinition of the terms, OK? Are we talking about displacement vs. semi-planing vs. planing hulls. I've kind of lost track.

 

[Nightflyer]

There is no inherent stability advantage in what we think of here as a FD hull form vs. SD. In fact probably the opposite. Many racing sailboats are now much closer to our idea of SD than FD (chines, very low deadrise, flat run). Ultimate stability has a lot to do with superstructure and CG. The superstructure of many trawlers, SD and FD, is suspect in heavy weather. But certainly you can build (and there have been built) SD with strong superstructure. CG can be lowered by ballast, but also by taking the top two layers off the 4 layer cake that many of these designs resemble, lowering the tanks, engine, and batteries, etc. Purpose built, an SD hull could be water ballasted for transoceanic stability, then pumped out - that is the way ships do it. I'll stick to my point - there is no inherent difference between the two hull forms WRT seaworthiness.


Modern sailboat sterns look an awful lot like SD trawlers. They cross oceans routinely. More than a few modern sailboats are planing hull forms - nearly all the racing ones are. Lying ahull used to be something people would do but it has greatly fallen out of favor due to a large body of experience (and tank testing) suggesting it is a bad idea - regardless of hull form. At Southhampton University they proved that a boat abeam to seas can be capsized by a breaking wave equal to (or a bit less than) its beam - and hull form made no difference. The explanation is in breaking wave dynamics which make stability almost a don't care at a certain wave size. A much better passive storm survival tactic is to lay to a parachute sea anchor or Jordan series drogue. Active tactics are better as long as you can stay awake, the problem here with most trawlers is they steer poorly due to small rudders (compared to sailboats).

Some example of boats rolling on waves about as big as their beam.

https://youtu.be/ENHn2hZ4vmI.

https://youtu.be/6dXrLkzuwBc