Trawler Design and Performance Parameters

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And some of us fell off the wagon… :rolleyes:



Sailing again, but envisioning something like a Helmsman 38E in the future. :flowers:
I had a plan to do both, but my sailboats have largely been collecting dust the last couple of years.
 
I'm making the transition from sailboats to trawlers. From my sailing days I know there are parameters used to describe a sailboats design and performance: displacement / waterline length; ballast / displacement; comfort ratio; capsize screening rating; PERF speed rating; and probably more.

Are there parameters typically used to describe trawler design and performance?


Given how unpopular the following comments will be, I may get disappeared here.....

I still am confused if you are considering inshore or offshore but my view is that for inshore, speed, comfort, and aesthetics that stir your heart are likely the major criteria. As a previous sailor, a good sea trial on a 'trawler' type vessel will likely be very informative for you. For inshore, if you find yourself in building conditions you can escape easily in most cases.
Now for the heresy. If you are serious about offshore, I deeply respect the suggestion to read Beebe and Beuhler. BUT, to suggest this can be the end of your research is akin to suggesting that reading Wilbur and Orville's handwritten notes is all there is to say about aeronautics and flying.

If you are serious, read/watch Dashew, Vripack Design Studio, Malcom Tennant (power and sail) and surely some others as well. These folks will not stutter when you inquire about stability specs and other important hull design ratios. They live by them, are proud of them, and happy to share both theoretical, sea trial, and incline test numbers.
While there are some very skilled vested interests perpetuating the idea that heavy and slow is all there is, as Loretta Lynne would say, "we've come a long way, baby".
BTW. I own a heavy and slow and I really like that boat.
 
Unfortunately Malcolm Tennant was lost to the the boating fraternity some time ago, and way too soon. For a time his family and some staff (incl. Tony Stanton) maintained his website and you could buy plans for his designs. Not sure of current situation.

For those wanting to get into the weeds, the information in the attachment was posted on boatdesign.net quite a few years ago. Eric has been retired for a while now as far as I know. It is a very readable primer.
 

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Given how unpopular the following comments will be, I may get disappeared here.....

I still am confused if you are considering inshore or offshore but my view is that for inshore, speed, comfort, and aesthetics that stir your heart are likely the major criteria. As a previous sailor, a good sea trial on a 'trawler' type vessel will likely be very informative for you. For inshore, if you find yourself in building conditions you can escape easily in most cases.
Now for the heresy. If you are serious about offshore, I deeply respect the suggestion to read Beebe and Beuhler. BUT, to suggest this can be the end of your research is akin to suggesting that reading Wilbur and Orville's handwritten notes is all there is to say about aeronautics and flying.

If you are serious, read/watch Dashew, Vripack Design Studio, Malcom Tennant (power and sail) and surely some others as well. These folks will not stutter when you inquire about stability specs and other important hull design ratios. They live by them, are proud of them, and happy to share both theoretical, sea trial, and incline test numbers.
While there are some very skilled vested interests perpetuating the idea that heavy and slow is all there is, as Loretta Lynne would say, "we've come a long way, baby".
BTW. I own a heavy and slow and I really like that boat.

Well, if you read Beebe as updated by Nordhavn's Leishman, the conclusion will be you need (surprise) a Nordhavn. If you read Dashew, the end-of-the-rainbow will be (surprise) a long skinny boat. And I'd guess that if you read Tennant, you will be convinced you need (surprise) a multi-hull. Reminiscent of the parable of five blind men feeling different parts of an elephant "it is like a snake" said the one who felt the tail. And so on. Dont get me wrong, all strong boats with impressive resumes, just that purposes of the OP's question of a consistent rating approach, well, there are many ways to skin that cat.......if you're looking a passagemaking capabilities.

But most are not looking at passagemaking capabilities. I think Hippocampus said it best: You’re unlikely to even see 6’. Boarding seas from your beam are equally unlikely. Use your common sense and accept the limitations of recreational trawlers except the very rare ones built from scratch for that service. If the OP is looking to cross oceans, different kettle of fish.

Peter
 
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Unfortunately Malcolm Tennant was lost to the the boating fraternity some time ago, and way too soon. For a time his family and some staff (incl. Tony Stanton) maintained his website and you could buy plans for his designs. Not sure of current situation.

For those wanting to get into the weeds, the information in the attachment was posted on boatdesign.net quite a few years ago. Eric has been retired for a while now as far as I know. It is a very readable primer.

Yes, great loss. He did leave some good work behind. I was able to chat with Tony a few times during diligence for DOMINO. The folks I bought her from had worked with Tennant directly during the build.
 
Looks like you purchased the right vessel for the job. Sharp looking too.


Have to say, the exterior styling is the LEAST attractive part about our current boat... but I just grit my teeth and try to ignore it... since it checked all the other boxes.

<sigh>...

-Chris
 
Problem with the EU system is it’s a statement as to the capabilities at time of initial launch. And only at initial launch.

Depending upon components used, design and execution of construction how long the vessel is really capable at the initial designation may vary widely. Knowing if the vessel was built to ABYC, Lloyd’s, Veritas or other class criteria may help in judging long term durability but a EU classification tells you little about construction details that may come up during your time of ownership imho. STIX maybe more meaningful but again doesn’t address durability.

So you can be on a boat with the same rating as another boat and the two be no where close to each other as to capabilities or behavior in a seaway.

Hi, you are right, the stability changes when the boat is equipped later vs the basic boat.

When NT wanted to expand to Europe, they had to order a Naval architect to calculate different parameters, do physical tests, etc.

Some changes were made and then NT 34-37-44 got CE-B certificate.

The factory did not agree to tell the GZ curves, it would have been interesting to see where the theoretical angle of tilt is, which cannot be exceeded without falling over, I know that the water enters the machine at an angle of 43-45° when the boat tilts sideways.

More info
http://www.glantoa.net/nordic_tugs_stability.pdf

NBs
 
Would also look at Gerr, Irons, Vripack, and so many others who have explored designs beyond the classic heavy, full displacement form. Boat design makes for a fun site to follow.

The unfortunate truth is regardless of paradigm the needs of a blue water boat aren’t the needs of a coastal boat. In sail they say a motorsailer is a boat that can sail or power but can’t do either very well. It’s the same with blue water v coastal power. As an example my little SD hull can scoot by TTs gorgeous brick house vessel. I can go 1200nm if I powerback but can’t cross oceans. His weather planning even when coastal is much less restrictive than mine. But it’s a rare bridge I can’t get under.
Same with FD v SD v multi v LDL. All have their inherent limitations. You’re right the usual stuff we look at in sail isn’t easily available if it’s available at all. Wish to thank North for his link but it doesn’t tell me my AVS nor a Gz. Rather all I know my boat is a B at launch. Since then it has a thousand pounds of SeaKeeper. Then more weight with tools, stores and spares. But I run the boat well below the limits stated by B. I had a AVS of 130 degrees in the last sailboat and very little areas in th Gz curve under null. My current AVS is maybe 35-40 degrees. It’s changed how I cruise. TT and many here have A boats and have paid attention to keep them that way. They have a level of freedom I don’t have. But it comes with a penalty. Not only in expense but also in speed and draft. Others have gotten around the draft issue with LDL but have the limitations of large LOA for available space and payload. No free lunch with boats.
So before even looking at boats decide use patterns. This includes details. I knew I commonly pick a direction and go. Now a days you can’t assume there will be an open mooring ball or slip when you want to stop. You may need to go well above hull speed to get to a good place to anchor or find a berth. This is particularly true if you need >50’. So decided under 50’ and SD. I know I’m willing to pay less attention to tides and currents in order to have more freedom in timing of transits. So SD preferred over FD. Also I’m commonly in areas of a lot of traffic so safer in SD. I like skinny water and like to fish. But as long as I’m under 5’ I can go most places and if necessary fish off the dinghy. We spend 99% of the time as mom and pop. But after living aboard for a decade know for us having two heads is a huge thing for quality of life. Each has their own. Can take two showers or brush our teeth at the same time and of course two toilets lowers stress. Of course with another couple aboard one head is a major hassle. We’ve been stuck in a aft cockpit sailboat. Being on a flybridge makes docking easier, gives you a view, lets you see into the water and lets you turn off the AC. So that was on the must have list. It’s all those little things that add up to which boat is good for you.

Your wants and use patterns will be different than mine. But it’s those things that are the key determinants of what type of boat to look for. Only then can you parse differences in principle dimensions, engines, accouterments, layout, efficiency, and layout. But the biggest step is to accept it isn’t a sailboat.
 
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Given how unpopular the following comments will be, I may get disappeared here.....

I still am confused if you are considering inshore or offshore but my view is that for inshore, speed, comfort, and aesthetics that stir your heart are likely the major criteria. As a previous sailor, a good sea trial on a 'trawler' type vessel will likely be very informative for you. For inshore, if you find yourself in building conditions you can escape easily in most cases.
Now for the heresy. If you are serious about offshore, I deeply respect the suggestion to read Beebe and Beuhler. BUT, to suggest this can be the end of your research is akin to suggesting that reading Wilbur and Orville's handwritten notes is all there is to say about aeronautics and flying.

If you are serious, read/watch Dashew, Vripack Design Studio, Malcom Tennant (power and sail) and surely some others as well. These folks will not stutter when you inquire about stability specs and other important hull design ratios. They live by them, are proud of them, and happy to share both theoretical, sea trial, and incline test numbers.
While there are some very skilled vested interests perpetuating the idea that heavy and slow is all there is, as Loretta Lynne would say, "we've come a long way, baby".
BTW. I own a heavy and slow and I really like that boat.

You should not be disappeared for saying the truth. :D

Well, if you read Beebe as updated by Nordhavn's Leishman, the conclusion will be you need (surprise) a Nordhavn. If you read Dashew, the end-of-the-rainbow will be (surprise) a long skinny boat. And I'd guess that if you read Tennant, you will be convinced you need (surprise) a multi-hull. Reminiscent of the parable of five blind men feeling different parts of an elephant "it is like a snake" said the one who felt the tail. And so on. Dont get me wrong, all strong boats with impressive resumes, just that purposes of the OP's question of a consistent rating approach, well, there are many ways to skin that cat.......if you're looking a passagemaking capabilities.

But most are not looking at passagemaking capabilities. I think Hippocampus said it best: You’re unlikely to even see 6’. Boarding seas from your beam are equally unlikely. Use your common sense and accept the limitations of recreational trawlers except the very rare ones built from scratch for that service. If the OP is looking to cross oceans, different kettle of fish.

Peter

One should read Beebe, Buehler, the Dashews, Colvin, etc. They all have different viewpoints, and reasons supporting their view, which is why one reads them. One hopefully becomes educated enough to see which of the view points best matches the goals one is trying to achieve with a boat. There is not A Right Answer, in fact, there are often Many Right Answers, not to mention Good Enough Answers. :D

Since boats are so designed constrained, one really needs to focus on what one will do, as opposed to wants to do, to get what is needed to do.

Decades ago, when the seeds for the crazy boat idea were sprouting, I read Buehler and Kasten. Kasten's has a great website for technical information on boat building but I don't like the looks of his boats, mostly the interiors. Buehler's interiors were not that good, and my impression was that he like to design the structure and exterior of a boat, the interior, not so much. :)

We seriously looked at Diesel Ducks, met George and traveled to China to see the boat yards. But it was too soon for us to have a boat for a variety of reasons and one of our big concerns about having a boat built in China, is now reality. At the same time the FPB and LRC boats were arriving and were, and are, very interesting. The FPB is just too expense, the LRC was a bit too small space wise and too new.

Fast forward to today, the FPB is still too expensive,:D but the LRC has matured and has a new model that seems to be about right. For Us. Some of the advantages of the LRC is range, speed, low draft, low air height, ability to dry out, sized to fit many of the European canals, and huge solar power production. However, to get these attributes, one is giving up living space. The pesky design constraints can't be escaped.

Reading my every growing library of boat books to get different viewpoints, spending time on boats, visiting boat yards, seriously looking at places we want to visit, and thinking about which boat characteristics are most important, back to the books, has really helped focus on what is most important to us. But it all started with the websites and the books.

Later,
Dan
 
Dann when I

....is range, speed, low draft, low air height, ability to dry out, is range, speed, low draft, low air height, ability to dry out, sized to fit many of the European, and huge solar power production....
Later,
Dan


read that I thinking you describe our former boat ! :)
except for " , sized to fit many of the European"

because our was designed to even cross one of the smallest French canal "le canal du midi" ok sometime we was near the stone of the bridge :):angel::lol:
 

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We, like many others here, have made the sail to power transition. We went around the world in a Swan 57, raced for 25 years on OPB, and then switched to Fintry and now Morning Light.



Not mentioned above, I think, is the simple fact that most production sailboats are raced -- some in a very few places and some all over the world. Most intelligent race organizers demand design numbers both because they would like to do their best to insure safety and because they need them for handicapping.


I submit that such numbers are largely irrelevant unless you propose to do passagemaking of more than 48 hours offshore. Weather forecasting is good enough, so you simply don't leave home if the forecast calls for nastiness. If you do plan such trips, there are very few stock boats with windows that I would take far offshore. Fintry's windows are 1/2" tempered glass, so we were comfortable crossing the Atlantic in her. As an ex-Royal Navy vessel, she has a complete stability book.


So, rather than spend time trying to find a lot of data that won't really be helpful, I suggest you spend more time refining the other search parameters discussed above.


Jim


Sweetwater -- Swan 57 sloop on which we circumnavigated 1995-98
Fintry -- x Royal Navy Fleet Tender -- owned 2003-2022, 20,000 miles including trans-Atlantic
Morning Light -- Webbers Cove 42 single screw trawler 2021- ?
 
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