Trawler Rocking, Rolling and Stability

[Don L]

As I look at trawlers they all seem to have 3.5-4' draft (a plus to someone who has been cruising around on 6'4" draft). I have to wonder about the rocking, rolling and stability of these. They are low draft and high windage with nothing really to stabilize it. Let me tell some observations so you know how I view it (all I can currently base it on whether right/wrong):

My first trip across to Bahamas we were sailing and in sight of a trawler in front of us most of the trip. We watched this boat for hours just rolling back and forth in what we considered pretty mild open water seas. We later asked the guy how his crossing was and he said "It SUCKED"

Last week at an anchorage I met up with some ex-sailors on a 44' DeFever that they had "fitted" out for "comfort". It had a 6' draft and stabilizers (the ones on poles that have the plates, don't know what those are called). At anchor they rolled around just as much as us. A few days ago they were next to us in what turned out to be a terrible anchorage for rolling due to the surge. They were rolling just a much as all the sailboats and like me were pulling up anchor a first light to get out.

So what should I look at far as type and design to reduce this issue in a trawler? It didn't seem to me that the 6' draft made any difference at anchor. Are those pole type stabilizers and trawler sails really of use?

I am sure I am asking a loaded question because far as trawler go I don't enough to ask a more specific one.

Or is this just something you have to put up with and try to plan around?

thanks

[rslifkin]

Stabilizers (either paravanes, fin stabilizers, gyros, etc.) are all a very viable option to reduce rolling. Beyond that, the hull shape and weight distribution within the hull will affect how the boat rolls, just like with a sailboat (both in terms of how much roll and how comfortable the motion is). And no matter what boat you've got, there's always a point where the conditions are just uncomfortable.

In terms of behavior in mild seas, sometimes you just find a sea state that's exactly wrong for the boat you're on (in terms of wave period and your direction of travel). I've had days where we're sitting there thinking "why the heck does this ride suck so badly, it's not bad out here and that other guy looks comfortable?" But at the same time, there are other days where the ride seems fine to us and you see a different boat that seems to be getting the snot beaten out of them.

[DavidM]

“Trawlers” typically have two types of hulls: most are semi-displacement designs while a fer like the KK are full displacement designs. The SD types usually have high initial stability due to the hard chine, flatter bottom design, but have poor ultimate stability. The FD types usually are ballasted so they may roll more initially but have ultimate stability.

I don’t know what type of boat you followed to the Bahamas, but the Defever is a SD type. The pole type stabilizers only work underway since it takes the dynamic moving water forced on the fish to provide righting force.

If roll stability is very important to you, I would look for a SD trawler with hydraulic fin stabilizers or maybe a gyro type that will also provide stability while anchored, but you will have to run a generator to keep it powered.

Or maybe a motor sailor where you have ballast, keel and sails to stabilize you.

David

[mvweebles]

Given the background you've given of yourself in this and other threads, you will not be happy with a boat that doesn't have some form of active stabilization while underway - hydraulic fins, paravanes (the poles that stick-out the side for use underway - more on this in a moment), Seakeeper gyros, etc. Unless approaching size of motorsailor, stabilizing sails are a myth in my opinion. Active stabilization is an expensive option and limits the boats you can consider, but you will not be sorry you held-out for a stabilized boat. I promise.

BTW - according to respected naval architect Michael Kasten (or was it David Gerr?), stabilizers do not change the stability metrics of a boat - that's a function of design and load. What stabilizers do is purely a comfort thing.

At-anchor stabilization. There are two choices. Seakeeper gyro which requires the generator be running (and being a fairly new option, is only found on newer, more expensive boats likely out of your budget). Or "Flopper Stoppers." These are outrigger poles that look like Paravanes but are much less robust because they are only used at anchor, not underway. Paravane rig can be used as flopper stoppers, but not vice versa. Forespar makes a nifty flopper-stopper setup - my boat had spinnaker poles originally that I replaced with the Forespar poles. I have them on both sides of my boat.

Defever 44 - I like this boat, but they are indeed tall and tender. When they get rocking, they can really develop some motion. Most have hydraulic fins, but sounds like you saw one with paravanes. It probably needs fairly long poles which it may not have had- possibly due to air-draft issues and the ICW but that's only a guess.

Peter

EDIT - stock photo from Forespar of their Flopper Stopper (at-anchor only) poles - same as I used. About $1.5k for each pole and plate, plus rigging. They really work well.

[rslifkin]

Originally Posted by mvweebles

Defever 44 - I like this boat, but they are indeed tall and tender. When they get rocking, they can really develop some motion. Most have hydraulic fins, but sounds like you saw one with paravanes. It probably needs fairly long poles which it may not have had- possibly due to air-draft issues and the ICW but that's only a guess.

On that note, I've always wondered about low-profile paravane poles. Maybe something that retracts against the side of the hull instead of straight up in the air.

[O C Diver]

Originally Posted by Don L

So what should I look at far as type and design to reduce this issue in a trawler? It didn't seem to me that the 6' draft made any difference at anchor. Are those pole type stabilizers and trawler sails really of use?

IMO,

Staterooms significantly higher than the waterline will be uncomfortable in sloppy anchorages.

Vessels with lots of windage (structure or enclosures) can be uncomfortable when wind and current are from different directions.

Boats that hunt at anchor (pivot based on shallow draft in the forward 20 to 30% of the hull) aren't comfortable in seas at anchor. Mine does this. There are techniques to reduce it but not eliminate it.

While you may want to pick the best riding boat with stability accessories for anchoring, that's generally not going to be the number one reason you pick a boat. For me, the best solution is to optimize the boat you choose for anchoring and pick better anchorages.

Ted

[Don L]

Originally Posted by mvweebles

Defever 44 - I like this boat, but they are indeed tall and tender. When they get rocking, they can really develop some motion. Most have hydraulic fins, but sounds like you saw one with paravanes. It probably needs fairly long poles which it may not have had- possibly due to air-draft issues and the ICW but that's only a guess.

maybe as they were proud on it being a "short" boat that if they dropped the sail pole could Do the Loop

[Don L]

So in the trawler world; is there really much difference of a 3.5-4' draft and a 6'?

Do most trawlers even have ballast or is it all engine and tankage?

[rslifkin]

Originally Posted by Don L

So in the trawler world; is there really much difference of a 3.5-4' draft and a 6'?

Do most trawlers even have ballast or is it all engine and tankage?

Draft doesn't necessarily tell you a lot about how comfortable the ride will be, although a deeper draft at the same size will likely be a little more stable (ultimate stability, not ride comfort) due to weight lower in the boat.

As far as ballast, full displacement trawlers will typically have some ballast, although typically not anywhere near as much as a sailboat. Semi-displacement trawlers may or may not have ballast, and anything that's a fast semi-displacement or planing is likely to have no ballast beyond what's provided by any equipment mounted down low like batteries and engines.

[jleonard]

Some, like the 40 Albin I had, have cement filled keels. That helps I'm sure, but it could still get rocking on bad days and bad wakes.

[mvweebles]

Vast majority of trawlers and motoryachts in the 35-50 foot range have about 4.0-4.5 draft.

From memory, KK42 and the Nordhavn 46 carried around 10% ballast. Many of the Defevers are full displacement but I have no idea about ballast. Need to differentiate between pure ballast and trim ballast.

The Willards seem to be the most heavily ballasted production trawler out there. My W36 for example was spec'd at 26k lbs displacement with 6k lbs ballast. The W40 was spec'd at 32k lbs displacement with 7k lbs ballast. Both weigh in quite a bit heavier than spec. Both boats, being round bottomed, are a bit tender at first but stiffen quickly. In open water swells, I liken the ride to a 1957 Buick Roadmaster on a country road. I run my stabilizers about 40% of the time. I think most boats with stabilizers run them 100% of the time, but my W36 is extremely low to the water (A/B ratio) which also has weaknesses - forward visibility isn't great and getting a proper exhaust install is challenging.

Peter

[dannc]

If one had a paravane setup on the boat, one could use fish while underway, and then switch them out for flopper stoppers in an anchorage.

Later,
Dan

[Don L]

Originally Posted by dannc

If one had a paravane setup on the boat, one could use fish while underway, and then switch them out for flopper stoppers in an anchorage.

Later,
Dan

Yes and it would be great to hear from a trawler owner who does this as to results.

[cafesport]

So just to add to the confusion trawlers like sailboats come in bluewater and coastal flavors. They are as similar as baseballs are to bocce balls.

Mitigating roll is a large part of both hulls design parameters and the other part is in the rigging kit.

Our old bluewater sailboat rarely needed anything but hanging a dinghy from the main boom in some of the “ rolly” anchorages.

On our trawler we’ve only needed a single flopper stopper which seems to always attract the dinghy’s of the rolling sailboats around us.

Finally if a boats rolling motion is paramount you might broaden your search to include a few catamarans.

[Shrew]

Originally Posted by Don L

Yes and it would be great to hear from a trawler owner who does this as to results.

Most trawlers are NOT stabilized. Most do Not have flopper stoppers. Most people either pick the days when they travel or deal with it.

You're focused on a problem that doesn't really exist for most people. Rolling underway, and a little roll in a rough anchorage along with 'wagging' on anchor aren't really problems to be solved.

[mvweebles]

Originally Posted by Shrew

You're focused on a problem that doesn't really exist for most people. Rolling underway, and a little roll in a rough anchorage along with 'wagging' on anchor aren't really problems to be solved.

Problem may not exist for some, but for those who cruise, open roadstead anchorages (much of pacific coast) are an occasional fact of life. Or conditions where wind and swell are cross. Or an anchorage near a ferry landing. I wouldn't be without some sort of at-anchor stabilization. Relatively cheap and very effective.

As far as underway stabilization, all I can say is the people who have it will never return to an unstabilized boat. It's really that good.

Peter

[dannc]

Originally Posted by Don L

Yes and it would be great to hear from a trawler owner who does this as to results.

Kasten's stabilization article, Roll Attenuation and Bilge Keels, discusses paravanes, among other options. His comments about effectiveness are what people who use paravanes report.

* Paravanes: Per published data from various sources, roll attenuation can be on the order of 40% to 60%. Vessel speed does not appear to be important to roll damping benefit. There is some speed and efficiency loss due to drag of the usual types of paravanes. Drag can be substantially mitigated by use of low-drag paravane design (see below). Loss of one paravane is likely to degrade stability should the vessel be caught in a beam sea with the one remaining paravane to leeward (per research published in Marine Technology). Paravanes are relatively easy to retro-fit. Relatively inexpensive. Medium complexity in use.

Most, if not all, of the Seahorse built Diesel Ducks used paravanes and my understanding is they work as expected and as Kasten states.

The latest I have read is from Mobius, https://mobius.world/taxing-mbius-update-jan-1-15-2023/ in their Atlantic crossing. I think he has a later post thinking the behavior is better than in this quote:

We have not ever had a boat with active stabilisers so we don’t have any experience to compare the performance to. However I know enough from reading and talking with those who do have active fin stabilisers that they tend to reduce the rolling by about 80-85%. Based on our limited experience with Paravanes so far and in talking with others who have them, the estimate for more like 60-65% reduction.

Mobius has paravane conversations on his website and this site.

There are prior discussions on this forum discussing paravanes including those who installed them on their boats. Richard on Dauntless did so and he crossed the Atlantic twice, crossed the Panama canal to the Pacific and went up to Alaska using paravanes. His discussions are on the forums.

Later,
Dan

[Don L]

Originally Posted by Shrew

You're focused on a problem that doesn't really exist for most people. Rolling underway, and a little roll in a rough anchorage along with 'wagging' on anchor aren't really problems to be solved.

Well I am NOT most people and it isn't my first day cruising! But thanks for the wisdom.

[catalinajack]

Originally Posted by DavidM

“Trawlers” typically have two types of hulls: most are semi-displacement designs while a fer like the KK are full displacement designs. The SD types usually have high initial stability due to the hard chine, flatter bottom design, but have poor ultimate stability. The FD types usually are ballasted so they may roll more initially but have ultimate stability.

I don’t know what type of boat you followed to the Bahamas, but the Defever is a SD type. The pole type stabilizers only work underway since it takes the dynamic moving water forced on the fish to provide righting force.

If roll stability is very important to you, I would look for a SD trawler with hydraulic fin stabilizers or maybe a gyro type that will also provide stability while anchored, but you will have to run a generator to keep it powered.

Or maybe a motor sailor where you have ballast, keel and sails to stabilize you.

David

David, perhaps DeFevers longer than 50 feet are semi-displacment but I can assure you that a DeFever 44 is full-displacement. With its Naiad fin stabilzers, it takes a lot of beam action to make the ride uncomfortable. When asked if I want a slow pass on the ICW, I always respond with "maintain course and speed".

[catalinajack]

Originally Posted by Shrew

Most trawlers are NOT stabilized. Most do Not have flopper stoppers. Most people either pick the days when they travel or deal with it.



You're focused on a problem that doesn't really exist for most people. Rolling underway, and a little roll in a rough anchorage along with 'wagging' on anchor aren't really problems to be solved.

Most are not stabilized? Perhaps. But, most DeFever 44s are, indeed, stabilzed. Without stabilization, they roll like a pig. I would not buy one that is not stabilized.