Trawler vs CPMY re: Seaworthiness

[Open-d]

Hello,

I am trying to get an assessment of the seaworthiness of something like a Hatteras, 61 CPMY with a typical true trawler-style yacht.

Assuming same Masters and crew and same weather conditions, how much less seaworthy would be the CPMY be than the average true, full-displacement trawler, or, perhaps the Hatteras 65 or 58 LRC.

The scope of the comparison would be long ocean-crossing passages. Ignore, for now, fuel/range considerations.

I know a definite answer can't be given, but same for same, what sort of difference would you feel exists.

Some sort of percentage would be appreciated, such as "the CPMY would be ??% less capable".

Thanks

 

[rslifkin]

If you're looking at specific models, it would be possible to judge the differences. But there's not really a good generalization to make there. There are semi-displacement and planing boats that are very seaworthy and there are full displacement boats that have significant weak points.

It matters how sturdy and solid the overall hull is, but things like strength of windows, placement of vents, motion comfort, etc. all matter. One of the biggest concerns with long trips on a faster boat is how the motion changes when you slow down. In some cases, being forced to go slow for fuel range can be limiting, as certain conditions are far more pleasant at a higher speed.

In general, the older Hatteras builds have a good reputation for putting up with a lot and riding pretty well when it's rough.

Do you have a sense of where you'd want to take the boat (and therefore what demands may be placed on it)?

 

[caltexflanc]

Our Hatteras 56MY (the 61CPMY without the cockpit) was extremely seaworthy and cruised in rough conditions in company with many "trawlers" over the years, including a Hatteras 58 LRC. In either case you want stabilizers.

There is a current member here Woodland Hills, that has a 63CPMY so I'm sure he will check in.

I originally was looking for a 61CPMY, but couldn't find one at the time that was in the condition I wanted. We personally did not like the layout of the 58 or 65 LRC for our full time live aboard use, but that is a very personal decision; friends with them love it.

 

[Open-d]

Our Hatteras 56MY (the 61CPMY without the cockpit) was extremely seaworthy and cruised in rough conditions in company with many "trawlers" over the years, including a Hatteras 58 LRC. In either case you want stabilizers.

There is a current member here Woodland Hills, that has a 63CPMY so I'm sure he will check in.

I originally was looking for a 61CPMY, but couldn't find one at the time that was in the condition I wanted. We personally did not like the layout of the 58 or 65 LRC for our full time live aboard use, but that is a very personal decision; friends with them love it.

Would you feel comfortable on a trans-Atlantic passage in one?

 

[READY]

I have owned many boats including a stabilized Hatteras 58 MY. These boats are not made for deep ocean cruising. As was pointed out there are many considerations before taking on a transatlantic trip. In the case of Hatt MY they don't meet some of the most critical such as range and window strength.

 

[mvweebles]

Rslifkin: "One of the biggest concerns with long trips on a faster boat is how the motion changes when you slow down."

This is key. Using the Beaufort scale, pretty much either boat is seaworthy in Force 4 conditions (seas 3-5, sustained wind in mid-teens across open water with at least several hundred miles of fetch). A 60-footer of any class will do just fine due to its sheer heft and size compared to the sea state.

At Force 5 and above, a well prepared/built boat starts to differentiate itself. Notice I say boat, not trawler vs MY. Its not always easy to tell the difference between them beneath the water.

At Force 5 (6-8 foot seas, wind in low/mid 20s), it starts to get pretty uncomfortable, especially since the boat will need to be slowed down. This is where the MY will start to roll because their stabilizers are overwhelmed because they were designed for faster speed. Important to note that according to David Gerr who has written extensively on the subject, stabilizers do not change a boats stability, but do make it more comfortable. Also, because the rudders on a MY are smaller, slower speed also means the autopilot will not work as well - you will need to adjust it at the very least. A standard home style fridge is unusable. Cooking is difficult. Sleeping is on the sole of the aft part of the boat. This is where you wish your cabinets had positive catches.

At Force 6 (upper 20s and 9-12 foot seas), the spray will be constant if headed into weather. If running, the boat will corkscrew badly (beginning form of a broach) from time to time . If your windows are not watertight, the boats interior will experience water intrusion and subsequent damage. Anything that is not well secured (and some things that are) will begin to part and shift. Chances are your autopilot will not work well, and you may need to work the throttles for some waves to increase flow over the rudders. Assuming the engines don't fail, this is not life threatening but there's a decent chance you will put the boat for sale and buy an RV when you finally reach Port.

At force 7 (near gale - wind in low/mid 30s with seas to 6 meters), you will feel you are in survival mode doing all you can to keep the bow into the seas if possible (they will be confused). This will mean frequently interrupting the A/P to hand steer and use throttles. You will likely get rolled to 45 degrees or a bit more from time to time. A MY with its high CG will be more susceptible, roll more deeply, and be slower to recover. Assuming the engines don't quit and steering doesn't break, you'll make it through, but beyond Force 7, luck starts to play more of a role in your destiny than you'd like.

Beaufort Scale goes to 12.

The Pilot Charts give historical weather for the world's oceans, measured in Beaufort Scale. You can decide for yourself it a 60 foot MY qualifies for the trip. A lot will depend on how much you believe the Pilot Charts - if you want to prepare for weather well in excess, then a MY design will fall off due to high CG, small rudders, and stabilization designed for calmer conditions.

Peter

 

[caltexflanc]

Would you feel comfortable on a trans-Atlantic passage in one?

The MY series is not designed for that, range-wise. The LRC's are. The former has the capability of going well over hull speed, the other of going far.

 

[rslifkin]

As mvweebles pointed out, smaller rudders on the faster boat become a handling concern when heading down wind. This is where the speed vs range vs handling problem comes in the worst, I think. Going downwind even in pretty bad conditions can be made pleasant in the MY type boat (often more comfortable than the FD boat) provided you can just go whatever speed works best (which will usually be the speed of the waves if they're big). When you're forced to go slower than that to conserve fuel, then things can get a lot more challenging and less comfortable.

 

[Mako]

I am trying to get an assessment of the seaworthiness of something like a Hatteras, 61 CPMY with a typical true trawler-style yacht.

Mr. Open, are you specifically interested in Hatteras' or is this a general question? As a general answer I would say there is no comparison between the two when it comes to open-ocean, bluewater, cruising. However that may not necessarily be your long term interest.

If you'll be circumnavigating and spending a big percentage of your time out in the open, then compromises that lean more heavily towards seaworthiness outweigh luxury. However I'd bet that 99.999% of boat owners do not fall into that category.

I owned a bluewater boat which crossed the Pacific, but it had a cockpit. Stupidest thing to have. In heavy following seas I was generally dragging 1 or 2 tons of water along while being constantly pooped. Thank God for watertight steel bulkheads and laminated glass windows. Was prepping to oversize the rudders as well but then decided to sell.

 

[Woodland Hills]

Would you feel comfortable on a trans-Atlantic passage in one?

I would not be comfortable crossing the Atlantic in anything smaller than 200’. This is why airplanes were invented!

 

[Hippocampus]

Contemplating doing the North Atlantic gyre. Expect to go west east via northern route in season. Then down across bay of biscay . Then azores to windwards. From conversations with those who’ve done it and are much more knowledgeable than I as long as you’re willing to take 2 years to capture the best portions of the seasons it’s commonly the coastal run down France and Portugal that can be the most problematic.
All boats corkscrew. Believe this is the most unpleasant motion for carrying out activities of daily living. Believe sometimes just a small change in angle to the wave train often improves motion and that angle varies boat to boat. Similar pitching and pounding is sensitive to angle. From past experience we’ve traveled much farther then the rhumb line just to improve the ride. Similarly Allander Coles advice of decades ago still holds true. Both running and beating there’s a right and wrong way to deal with waves. Especially across the crest and on descent.
Reading the above think about two things. Passive and active strategies for dealing with weather. Not discussed above is passive strategies. From virtually all the SD and MV recreational boats we've been looking at warps, drogues and our favorite the JSD isn’t a viable choice due to down flooding risk. So one would be limited to sea anchors. Have not deployed a sea anchor in anger in above 7 but been told on a small boat with a small crew this can be quite an undertaking. Been told retrieval can be so hard that people just cut them lose after unsuccessful attempts at retrieval.
So now you’re betting on everything going right. Spot on weather predictions and no significant mechanical failures.
Not interested in doing that on anything but a purpose built boat. Think purpose built is as if not more important than size .

 

[Nomad Willy]

Size matters.
But it dosn’t make a watermelon into anything you want.
Magic is for the movies.

 

[Open-d]

Mr. Open, are you specifically interested in Hatteras' or is this a general question? As a general answer I would say there is no comparison between the two when it comes to open-ocean, bluewater, cruising. However that may not necessarily be your long term interest.

If you'll be circumnavigating and spending a big percentage of your time out in the open, then compromises that lean more heavily towards seaworthiness outweigh luxury. However I'd bet that 99.999% of boat owners do not fall into that category.

I owned a bluewater boat which crossed the Pacific, but it had a cockpit. Stupidest thing to have. In heavy following seas I was generally dragging 1 or 2 tons of water along while being constantly pooped. Thank God for watertight steel bulkheads and laminated glass windows. Was prepping to oversize the rudders as well but then decided to sell.

For some combination of reasons, I tend to gravitate towards them, especially the LRC-series.

Cross the Atlantic, cruise down France and Portugal and into Med. Around the med, spend time in Madeira and either stay there, or back to US. If I bought a boat in Europe, would only need to cross Atlantic on way back, assuming I didn't stay in Madeira. I certainly won't be circumnavigating or the like, but a long passage or two would be on the horizon. Not a loop candidate or ICW cruiser, for sure.

 

[Open-d]

I would not be comfortable crossing the Atlantic in anything smaller than 200’. This is why airplanes were invented!

I can't afford an ocean-cross airplane.....yet!

 

[O C Diver]

I would not be comfortable crossing the Atlantic in anything smaller than 200’. This is why airplanes were invented!

For the difference between a very nice coastal cruiser and a passage maker you can buy a lot of tickets for your coastal cruiser to cross the ocean on a purpose built freighter.

Ted

 

[Hippocampus]

Kinda want the experience and stop offs in Iceland,Ireland,England and Portugal hold great interest. Did research on machado Joseph’s disease. Have met several of the source families for that genetic disease on a invite from the Portuguese government (went by airplane(s) and inter island). Very much want to spend time in the azores. Already been on many of those islands but not Pico and for several reasons it’s on the list.

Seems ever time this comes up some have no interest but some do. Whatever floats your boat is just fine.

 

[Woodland Hills]

If what you want is a coastal and near-offshore (Bahamas, not Bermuda) cruiser then a Hatteras CPMY is very well suited for that purpose, not least because of the price. You can get an awful lot of boat for a very reasonable price compared to a bluewater boat of similar LOA.
But if you intend to actually cross oceans then it is unsuited at any price.

 

[mvweebles]

......
All boats corkscrew. Believe this is the most unpleasant motion for carrying out activities of daily living. Believe sometimes just a small change in angle to the wave train often improves motion and that angle varies boat to boat. Similar pitching and pounding is sensitive to angle.

Yes, all boats will corkscrew. And as Eric/Nomad Willy states, size matters. What happens is the stern gets lifted, steering is neutralized, the stern goes sideways, and, if the wave big enough, the boat trips over its chine or keel. . Design parameters such as A/B ratio, AVS, and roll-period determine her desire to right herself. Stout windows and fast drainage determine her ability.

But we're talking pretty big seas which take some time to develop. Modern forecasting is reducing the surprise factor.

Peter

 

[rslifkin]

Pretty much the only way to prevent corkscrewing is to go faster so the waves aren't overtaking you (either pace them or run over the tops and go surfing). Problem is, unless you've got a really big boat, you can't do that on a long ocean passage no matter how fast the boat can go. Anything reasonably sized just won't have the fuel capacity to allow speeding up that much on a long run.

 

[Jeff F]

I think the last couple of comments get to the vulnerability of the CPMY. A big part of its capability comes from its ability to operate at higher speeds, and you lose that on long offshore trips.

I can't think of anything worse than trying to deal with heavy following seas while using a small fraction of available power. You've got rudders sized for high cruise that are far less effective at economy speeds and the broaching situation Peter describes is likely to happen far sooner than in a trawler if you're traveling at trawler speeds.

Just an armchair POV...

 

[Open-d]

For the difference between a very nice coastal cruiser and a passage maker you can buy a lot of tickets for your coastal cruiser to cross the ocean on a purpose built freighter.

Ted

That's an interesting thought. I have my eye on a 65 Hatt LRC in the Med-side of France. $300K and change. 6-71s.

 

[O C Diver]

That's an interesting thought. I have my eye on a 65 Hatt LRC in the Med-side of France. $300K and change. 6-71s.

In the financial collapse of 2008 - 2010, a large number of boats left the USA on freighters destined for countries less effected that were willing to snap up a bargain. Certainly no reason why a good boat at an extremely attractive price, shouldn't be imported back into the USA.

Ted

 

[KnotYet]

Pretty much the only way to prevent corkscrewing is to go faster so the waves aren't overtaking you (either pace them or run over the tops and go surfing). Problem is, unless you've got a really big boat, you can't do that on a long ocean passage no matter how fast the boat can go. Anything reasonably sized just won't have the fuel capacity to allow speeding up that much on a long run.

Any time I've been offshore the wave periods seemed pretty long - greater than 7 secs.
That translates to a wave speed greater than 25 k. Pretty fast for any cruiser.

 

[rslifkin]

Any time I've been offshore the wave periods seemed pretty long - greater than 7 secs.
That translates to a wave speed greater than 25 k. Pretty fast for any cruiser.

Yeah, the waves can definitely end up faster than you can go. But even if they're overtaking you with you only doing, say 18 kts, it's still a nicer ride than going slow. With the amount of thrust required to run at that speed you've got a ton of propwash over the rudders, so the overtaking wave doesn't hurt your ability to steer nearly as much. Which means the autopilot will be able to hold course more precisely, giving less corkscrew motion and a more comfortable ride.

 

[Hippocampus]

Tell me if my thinking is wrong.
Sailboats are pulled by the difference between pressure in front of the foil (negative) and pressure behind the foil (positive) when reaching or beating. Water flow across the appendages (rudder(s) and keels) is the difference between speed of water flow and speed of the boat.
On a sufficient broad reach or run sailboats are pushed along. Apparent wind speed decreases so motive force decreases. Helm becomes progressively less effective and eventually ineffective when boat speed matches water speed.
On power craft speed of the jet of water coming off the prop is well in excess of water speed and boat speed. If the rudder is close to the prop and directly in that flow a steering force will be maintained. Water flow from astern will decrease that effect to some degree but not eliminate it.
Corkscrewing is more the result of the fore and aft oscillation of unbalanced forces across the center of lateral resistance and the oscillation of wetted surface and involvement of reserve buoyancy. This is influenced by hull design, appendages, distribution of weight and amount of weight. So you oscillate between the stern being pushed up and more laterally (topsides to leeward) then the forward sections . Then the bow rises and stern swings back as it falls. This gives you the harmonic of simultaneously pitching and rolling.
Although at its extreme a broach can result you can corkscrew at non threatening degrees of motion. Some boats will corkscrew more or less at different speeds or angles. Sometimes changing the angle just a small bit helps. Sometimes speed. As regards speed have experience sometimes going slower might actually help.
Not everything is about survival or severe weather. Moderate conditions are much more common. It’s in those conditions that corkscrewing is more common and truly annoying. My experience is limited but to date light boats with unbalanced ends seem more prone to corkscrew. Heavy boats with slack bilges and more balanced ends seem to do it but to less of a degree.
Now rip this post apart.

 

[O C Diver]

Tell me if my thinking is wrong.
Sailboats are pulled by the difference between pressure in front of the foil (negative) and pressure behind the foil (positive) when reaching or beating. Water flow across the appendages (rudder(s) and keels) is the difference between speed of water flow and speed of the boat.
On a sufficient broad reach or run sailboats are pushed along. Apparent wind speed decreases so motive force decreases. Helm becomes progressively less effective and eventually ineffective when boat speed matches water speed.
On power craft speed of the jet of water coming off the prop is well in excess of water speed and boat speed. If the rudder is close to the prop and directly in that flow a steering force will be maintained. Water flow from astern will decrease that effect to some degree but not eliminate it.
Corkscrewing is more the result of the fore and aft oscillation of unbalanced forces across the center of lateral resistance and the oscillation of wetted surface and involvement of reserve buoyancy. This is influenced by hull design, appendages, distribution of weight and amount of weight. So you oscillate between the stern being pushed up and more laterally (topsides to leeward) then the forward sections . Then the bow rises and stern swings back as it falls. This gives you the harmonic of simultaneously pitching and rolling.
Although at its extreme a broach can result you can corkscrew at non threatening degrees of motion. Some boats will corkscrew more or less at different speeds or angles. Sometimes changing the angle just a small bit helps. Sometimes speed. As regards speed have experience sometimes going slower might actually help.
Not everything is about survival or severe weather. Moderate conditions are much more common. It’s in those conditions that corkscrewing is more common and truly annoying. My experience is limited but to date light boats with unbalanced ends seem more prone to corkscrew. Heavy boats with slack bilges and more balanced ends seem to do it but to less of a degree.
Now rip this post apart.

I don't have enough knowledge to comment one way or the other on the other on your theories and observations. However, in the few times I been out in 15'+ seas under size rudders nearly did us in. A big rudder(s) is all the difference in the world, just like steering at idle speed.

The other factor in heavy weather is how fast you can turn the rudder. While my boat does well in 4 to 5' following seas because of it's huge foil rudder, the autopilot pump needs to be faster moving the rudder. Part of responding to the bow falling off course has to be how quickly you can effect rudder angle change as it's easier earlier to correct boat heading.

Ted

 

[Hippocampus]

Ted totally agree rudder size, if its balanced, if its flat or foil, whether there's end plate effects or tip vortexes and how far back it is are all important.

Maybe I'm out of synch with you guys. Think you can corkscrew when still. Some of the most annoying in the past has been bottom fishing when in a outboard deep-V.

 

[O C Diver]

As your speed increases rudder balance becomes more important. Here is a factoid most of you will likely never use:

"For a typical rectangular rudder, the area in front of the pivot point needs to be 25 to 28% of what's behind the pivot point. As the shape of the rudder changes from a rectangle, a taller trailing edge adds more pressure, requiring the area in front of the pivot point to be increased by percentage."

I collaborated with a friend to build the rudder on my charter boat. It's amazing how much easier it is to steer with a balanced rudder.

Ted

 

[Hippocampus]

Virtually all manufacturers have switched to balanced spade NASA foil rudders for blue water sailboats some time ago. Now with foiling boats the addition of various techniques to eliminate or at least decrease tip vortex have been employed.