Stabilizers: A Must for Passage-Making?

[Simi 60]

If commercial trawlers are using them, guys who are often out in shite conditions earning a living when most others are cowering under a bed, I tend to think it must be pretty good.
.
Cost and reliability will of course sway the commercial guys decision as well.
They can't afford to be sitting in port waiting for repairs

Have seen them with paravanes, batwings, rolling chocks even a combination
Can't say I've heard of any with active fins or seakeeper

 

[Hippocampus]

Appreciate Peter’s point of view. There are statistics that have been generated as regards effectiveness for some of the systems. Some are fairly fixed in design. This much displacement use this SeaKeeper, this size boat operating at this speed range use this square footage of Humphrees, but others aren’t as defined. In actual use there’s too marked variability in execution to draw conclusions. However, the manufacturers of ABS, Humphrees, SeaKeeper, Magnus, Quicke and all the others have done computor modeling of the effects of their designs and engineering. At least at the ship size the same for ARTs. Some systems act only on roll. Others effect the other axises of motion as well. If the end goal is comfort all axises of motion are important not just roll. So unfortunately although there is data sets and comparisons available they are fraught with difficulties in interpretation. You are right I personally have little experience. But have been an avid reader of this literature. I would suggest as we do in both science, engineering and medicine we approach this with the understanding there’s a hierarchy of proof with antidotal reports the lowest, correlations next and controlled comparisons the highest. Given controlled comparisons aren’t feasible suggest we ae dependent upon modeling, tank testing,and rarely collected field data tempered by reported experience.
SeaKeeper used my actual boat to measure oscillation in the transverse plane as a physical realty not just a computer model. However although this is a good data set it’s marred by
Only looking at one axis
Being done by the manufacturer hence subject to potential bias
Applicable to my boat with my boats characteristics.
Yes the results were impressive. 85% reduction. Supposedly better than other technologies for “stabilization”. But this must be taken with a grain of salt. Testing was done in the mild to moderate conditions one would see in a coastal setting. It was published as part of their promo literature.
So Peter your points are well taken but one would think the level of data is just not there. One should look at it with a jaundiced eye. Perhaps accept that once there’s a commercial involvement more information is available but possibly open to bias so pay attention to the totality of information.
MF makes an excellent point as well. Given this can we discuss the comparisons while accepting what makes the best sense in a blue water setting may not for the coastal cruiser. As a starting point I would suggest in the coastal setting available information suggests gyros are most effective in roll attenuation in non planing boats with the recent advancements in fins and Magnus effect devices second. ARTs, rolling chocks, fish aren’t nearly as effective. In the open ocean setting in extreme conditions fins and Magnus maybe the safest choices. They continue to work unlike gyros when they reach the end of their ability to have precession. They do not effect static stability like ARTs. They do not carry the risks of fish nor put weight aloft. The above is posted as a starting point for discussion. Defer to others with more knowledge to point out holes in this formulation.

 

[mvweebles]

Appreciate Peter’s point of view. There are statistics that have been generated as regards effectiveness for some of the systems. Some are fairly fixed in design. This much displacement use this SeaKeeper, this size boat operating at this speed range use this square footage of Humphrees, but others aren’t as defined. In actual use there’s too marked variability in execution to draw conclusions. However, the manufacturers of ABS, Humphrees, SeaKeeper, Magnus, Quicke and all the others have done computor modeling of the effects of their designs and engineering. At least at the ship size the same for ARTs. Some systems act only on roll. Others effect the other axises of motion as well. If the end goal is comfort all axises of motion are important not just roll. So unfortunately although there is data sets and comparisons available they are fraught with difficulties in interpretation. You are right I personally have little experience. But have been an avid reader of this literature. I would suggest as we do in both science, engineering and medicine we approach this with the understanding there’s a hierarchy of proof with antidotal reports the lowest, correlations next and controlled comparisons the highest. Given controlled comparisons aren’t feasible suggest we ae dependent upon modeling, tank testing,and rarely collected field data tempered by reported experience.
SeaKeeper used my actual boat to measure oscillation in the transverse plane as a physical realty not just a computer model. However although this is a good data set it’s marred by
Only looking at one axis
Being done by the manufacturer hence subject to potential bias
Applicable to my boat with my boats characteristics.
Yes the results were impressive. 85% reduction. Supposedly better than other technologies for “stabilization”. But this must be taken with a grain of salt. Testing was done in the mild to moderate conditions one would see in a coastal setting. It was published as part of their promo literature.
So Peter your points are well taken but one would think the level of data is just not there. One should look at it with a jaundiced eye. Perhaps accept that once there’s a commercial involvement more information is available but possibly open to bias so pay attention to the totality of information.
MF makes an excellent point as well. Given this can we discuss the comparisons while accepting what makes the best sense in a blue water setting may not for the coastal cruiser. As a starting point I would suggest in the coastal setting available information suggests gyros are most effective in roll attenuation in non planing boats with the recent advancements in fins and Magnus effect devices second. ARTs, rolling chocks, fish aren’t nearly as effective. In the open ocean setting in extreme conditions fins and Magnus maybe the safest choices. They continue to work unlike gyros when they reach the end of their ability to have precession. They do not effect static stability like ARTs. They do not carry the risks of fish nor put weight aloft. The above is posted as a starting point for discussion. Defer to others with more knowledge to point out holes in this formulation.

Buried is one really good point that is rarely brought-up about gyros: they most likely are very effective at controlling pitch in addition to yaw and roll. New technology in fins improve on pitch, but a properly sized spinning gyro has to be better.

Hippocampus, I know of no one who researches more thoroughly than you. I have enjoyed reading your voyage of discovery from sail to power. I had never heard of Magnus or Humphees prior to your bringing it up (among other items).

I won't argue the (uncited) data you post, but how do you reconcile it with the many, many users of fish and fins who like their systems and chose them over and over again? Many of whom are extremely experienced cruisers. Luck? Ignorance? Or is it possible - just maybe possible - that the data only applies at the extreme margins of a table-top exercise, several standard-deviations out? How did Monk, Defever, Garden, and others get it so right long before CE Ratings that drive a study-for-the-exam culture amongst builders?

Or is it possible the data is largely sponsored by manufacturers with a dog-in-the-fight similar to the grand claims of magical anchors we've all seen over the years (or, at the extreme, Algae-X magnets to purify your fuel)? Just seems like the predictions of looming catastrophy of fish and fins comes from the gyro-Koolaid crowd. There are strong reasons to consider gyros, but dangers of fins and fish are wildly exaggerated. If that factored much into a buyer's selection, the buyer was sold Meteorite Insurance and paid dearly for it. Nothing wrong with gyros and they definitely have their use-case (guessing the center-console fishermen crowd are slurping them up).

In closing - is stabilization needed (per the OP)? Yep - universal YES!! Okay, maybe 'needed' is a grand statement, but like others, I wouldn't cruise an unstabilized boat. Which flavor of stabilization is best? There are scenarios where each excel, and some where they don't, so use-case is the real question. Do fins and fish impose risk? You have to really clip, crop, and manipulate data and context to make that argument with a straight face.

Peter

 

[DDW]

Instrumented measurements are flawed from the point of view that duplicating conditions is impossible outside of tank testing. I tried to do this myself (to justify my modest cost of rolling chocks). It isn't hard to measure roll pitch and yaw (I have a device installed that has continuously recorded this for 2 years). But comparing roll control using that data has the large confounding problem: what exactly were the conditions?

However comparison testing is relatively easy, and cheap. A production boat is built with stabilizers. Run it alongside a sistership without. This has been done of course, and a reasonable simulation of it is to disable the stabilizers and compare. To compare two systems requires two sisterships with those systems. Again for popular production boats this can be done as there are examples with those systems. You just need to charter those two boats and go out for an afternoon. The Quebec study is the only one I know of that did this.

Manufacturers could do this, but I think may be reluctant to actually know the answer. Also as this thread has proven, it isn't a straightforward answer. Depends on the boat, the goal, the budget, the tolerance for labor, and maintenance.

 

[Muirgen Afloat]

A paravane is a heavy weight swinging on the end of a line or chain. Under difficult conditions one could put holes in you or the boat or knock you overboard. If you handle them carefully, they should be OK, but "should" is always a difficult word in boating. If any part of the rig fails, you could have a serious problem.


Jim

Theoretically I can see this, if I'm out in really crazy waves. With the paravanes we have and the depth they are when we travel, I think we'd have to be out in 40' ft waves before they could swing anywhere near the boat. In a risk assessment with the potential severity of occurrence happening I'd say it's almost nil on our type of cruising. But I would be interested in hearing actual true stories of this being an issue in pleasure craft.

 

[Marco Flamingo]

but dangers of fins and fish are wildly exaggerated

You forgot to include the exaggerated dangers of an ART. Somebody who had skin in the game was the owner of the Swan Song, the 58' Monk with an ART. Here is an old post where the owner talked about real-world passage making with an ART.

We had looked into these units (gyroscopic stabilizers) when Swan Song was earlier in the stage of re-construction. At the time, according to the factory man in Japan, we'd need two of the mid-sized units to keep Swan Song from rolling less than 25 degree each side. If a sea state was at the level that we were rolling this much the power required to keep them both spinning was just over 8 KW. This all according to them. In a really nasty sea state they would need to be turned off as if they hit the stops often and with too much force they might self destruct. Suffering and surviving a knockdown wasn't in their vocabulary! All in all we opted not to go in that direction as the predictability of sea state isn't within our ability in making a passage.

As most of you know we went the route that few have taken and for the life of me I don't know why. An Anti-roll tank, ART, is our only roll reducing system on Swan Song. A totally passive device with no maintenance to date, 5 years, and only one moving part, water.

I wish I could say exactly what the numbers are for roll reduction but I can't. What I can say is that in 15,000 odd nm we have never rolled more than 30 degree and perhaps on 20-25. This includes a tough patch coming into Hawaii last year in waves that were occasionally in the 30' range. We can sit with no way on in 8-10 ft. seas with very little movement. So little that you can work on things and not be chasing tools all over the place. This is a very comforting fact especially when you have to shut down the engine for daily checks at sea.

For some reason Naval Architects hate them. They are afraid that they will somehow encourage a capsize or something similar. We have found all of this is bunk. Swan Song is stiff and has a high righting moment but it is round bilged and likes to roll and once started would go on for 12-15 rolls as a minimum. We tested all of this with full inclination tests, etc. Our boat parameters were fed into the computers that Dr Bass up in Newfoundland runs with his software and came up with the design tuned to our boat. $10,000 later it was constructed and put in place on top of Swan Song's Pilothouse. 1500 lbs. of water over our heads ;-)

Everyone who has ever been aboard either on the hook or underway is astounded by how Swan Song behaves in the water. At first they are puzzled and then as they watch other boats nearby whether they are sailboats with the masts waving in the sky or power boats showing lots of bottom paint they realized that Swan Song doesn't hear the music that the other boats are dancing to. As Seahorse John (now departed) once said in Bequia (St. Vincent and Grenadines) after an evening on board with the ferryboats passing 50' away without spilling the wine, "I thought you must be aground as you aren't rolling like the others". Then as he watched us round the point heading north out of the harbor the next day waiting for the first African tradewind swell to pin us down Swan Song just went on her merry way. "**** I got to get that system".

Bob Phillips, Another Asylum, has the same system done by Dr Bass. He is the one that sold me on it. Check with Bob as I think he'll compliment just about everything I've said.

I can't compare if paravanes would be as good but I don't think so especially at slow speeds, stopped or in shallow water plus they do require effort. Active fins are nothing but trouble long term and because of our size, propensity to roll, and slow speed the size of a system for Swan Song is large and in the order of $75K with all the attendant maintenance over the years. We would already be due for an overhaul. So for us the option was the paravanes or ART. Glad we made the choice we did and have never looked back.

Also as to significant wave height measurement, significant wave height is the average of the highest 1/3 of the wave. The actual wave height can be as much as 3 times that on occasion and from my experience usually is. Our height of eye is 12' off the water sitting in the pilothouse and beam waves up to this height aren't comfortable but offer no problem on the beam. Even an occasional crest coming aboard just tosses you sideways. Bigger waves that this and we are either taking them further forward or further aft. Dead down we are fine even in that 30' stuff near Hawaii. 20-30 degrees off our stern is our weak point. We get both the pitch and a roll so the corkscrew motion gets uncomfortable pretty quickly

Dave & Nancy
Swan Song
Roughwater 58​

Interesting that he also talked about why he chose ART over a gyro system. I'm not sure how much money was a factor, as he seems mainly concerned with effectiveness and simplicity of operation. It sounds like the research cost of Swan Song's ART was $10K. What was installation cost? The installation of stabilizing fins at the time was $75K. Who knows what a gyro(s) would have been. I'm curious as to how Swan Song's ART is doing today and any maintenance costs over the decades. Need new water?

I haven't read where anybody else talks about what happens with a gyro in really rough conditions, like what Swan Song experienced in 30 foot seas (the same seas that causes the anti-ART crowd to wet their pants). It seems the gyro system can be overwhelmed, break its mounts, and turn into a Tasmanian Devil in the lazarette (seen in this scientific re-creation at :35). Maybe the video is also an exaggeration.

 

[mvweebles]

You forgot to include the exaggerated dangers of an ART. Somebody who had skin in the game was the owner of the Swan Song, the 58' Monk with an ART. Here is an old post where the owner talked about real-world passage making with an ART.

Thanks for resurrecting this old post. I agree - it's a persuasive post.

I've been aboard a Roughwater 58, though only in-harbor. She's a really, really tender boat as Swan Song's owner insinuates. Impressive that they managed such roll reduction.

BTW - at least 3-4 Willard 40s have had roll-chocks installed. As moderator of Willard Boat Owners for almost 25 years, I have come to 'know' the owners and in my opinion, given their straightforward style, experience, and modest claims of noticeable roll attenuation (words chosen carefully) have the ring-of-truth. I would not hesitate to give them a try, at least on a displacement boat. Cost is modest ($5k). As Swan Song mentions, once the boat gets rockng, it keeps oscillating for a while. Reportedly, roll chocks reduce the ongoing cycle of rocking and quiet the boat down quickly.

Peter

 

[Hippocampus]

Peter think I’ve been temperate in my comments. I’ve repetitively said for the size boat I would use for voyaging a gyro would not be my first choice but then again neither would a Nordie or KK be but rather something long, lean, light and fast. Rather would probably spec Humphrees with interceptors given current offerings.
However there’s possibly a fault in your argument. That being the use of gyros in large commercial and military vessels. With the later cost maybe no object but probably not true for the former. As stated they’ve been around a long time but recent advances in bearings and engineering have made them more appealing. Especially in mission critical applications. We are lucky to have so many choices now and improvements in prior choices. As you and others say it’s a case by case decision. I only wished that reality was taken to heart and more objective views of the subject where people shift opinion not on hearsay but rather on the basis of what information is actually available.

 

[rslifkin]

As far as gyros in big commercial boats, powering a gyro is less of a big deal for them. They typically have big gensets running 24/7 for various stuff anyway, so what's a few extra kilowatts for a gyro?

 

[Fletcher500]

I only wished that reality was taken to heart and more objective views of the subject where people shift opinion not on hearsay but rather on the basis of what information is actually available.

Hmmmm.

 

[Mako]

I've been aboard a Roughwater 58, though only in-harbor. She's a really, really tender boat as Swan Song's owner insinuates. Impressive that they managed such roll reduction.

That tenderness was a result of her bottom and her beam. That was a major item that turned me off from really pushing for a closing on our contract - that it was very narrow. Don't remember exactly, but perhaps 13ft on an LOA of about 60ft. My intention was to moor it, so marina fees weren't a major factor playing into it, but the livability was limited considering its size.

 

[Hippocampus]

Generic problem. Increase efficiency by going narrow=increased tenderness. Important to distinguish tender from stable. At least on sail initial tenderness doesn’t equate to poor AVS. But life on a slant has definite drawbacks. Perhaps not relevant to the OP but think there’s no question for the newer designs going long, light and lean some form of stabilization is necessary even in a coastal setting.

 

[Marco Flamingo]

Now that we have answered the OP's original question; Stabilizers: A Must for Passage-Making? ("No" for some, "Yes" for others, "Depends" for the rest) I looked at the Monk 58 and the posts here about that boat's "tenderness." I also agree that it isn't stability, it's comfort that is being discussed (i.e., not stabilizers, but comforters?)

In addition to the tenderness of the hull effecting comfort, it is also one's relation to the hull. And by "one's relation," that generally means who is at the helm or sometimes the location of the crew when underway. My most vivid experience with this was as crew on the NOAA ship Discoverer. My berth was well below the working deck, at about waterline aft of mid-ship. The berth had a bar to keep one from rolling out, but I never used it, even in rough seas. The bridge, however, was 35 feet above waterline. Rough weather there was a challenge, but I was young and agile and had a wheel to hold on to. The conning tower was 30 feet higher than the bridge, straight up a ladder though a tube to a ride scarier than anything at the county fair. I believe the quartermaster kept access locked, and for a good reason. Had my bunk been up there, I'm not sure a bar would have kept me in bed. The point is, one's position relative to the hull makes a big difference in perceived comfort.

A picture of the Monk 58 (like Swan Song)* shows that the helm is raised, not uncommon for this sized vessel. But compare that to an older Monk design like the sedan cruisers (generally not ocean going vessels). My 32' is pictured below. It had a V-drive, so the engine was under the rear cockpit and one took three steps down to enter the cabin and get to the helm. When standing at the helm, my feet were at or close to the waterline and center of roll.

From a comfort point of view, having one's feet "on the surface" of the water was nice. There was none of that "clinging to the masthead" feel from being well above water level. Granted that there probably aren't any ocean going passage makers with a helm this low, but the height of the helm/living quarters is another "depends" factor.

* Not sure how old this for sale advertisement is or where Swan Song is now. The ad has lots of pictures, including its anti-roll tank. It does illustrate one of the criticisms of an ART. When retrofitted, they can be unsightly. They are certainly not as attractive as a fake smoke stack, now the de rigueur ornament above the helm. I would think that an original equipment ART could be merged with the pilot house so that it would disappear. Too bad Mr. Monk isn't around to figure that one out.

 

[long-cours.62]

Few day

Generic problem. Increase efficiency by going narrow=increased tenderness. Important to distinguish tender from stable. At least on sail initial tenderness doesn’t equate to poor AVS. But life on a slant has definite drawbacks. Perhaps not relevant to the OP but think there’s no question for the newer designs going long, light and lean some form of stabilization is necessary even in a coastal setting.

ago we was near a San Lorenzo 76 ....very large hull but very hight cabin

and VERY poor stability !
The crew said without stabiliser they CAN'T manage a 0.8m sea on the beam and they precised not for the cobfort but for the security ...
Even some time they must activate the stab ...in Marinas !?

 

[DDW]

The height of the pilothouse does not seem to be considered by many designers. One of the reasons a seaway is more comfortably tolerated in a sailboat is that the cockpit is aft, and not high. This is where the motion is less. Slightly aft of amidships and low is where the motion is least. Something even like a Nordhavn 40 has a pilothouse equivalent to half way up the mast on a 40' sailboat.

ART retrofit on top, like Swan Song, seems like the least desirable alternative. Built in and considered in the design from a blank page, it would have little effect on appearance, accommodation, or static stability.

 

[rslifkin]

The height of the pilothouse does not seem to be considered by many designers. One of the reasons a seaway is more comfortably tolerated in a sailboat is that the cockpit is aft, and not high. This is where the motion is less. Slightly aft of amidships and low is where the motion is least. Something even like a Nordhavn 40 has a pilothouse equivalent to half way up the mast on a 40' sailboat.

That's one reason aft pilothouses are typically more comfortable than forward. It's a better placement and makes pitching motion much more tolerable. Of course, you're typically still up high, so rolling motion is rather noticeable.

 

[Hippocampus]

People forget boats move in three axises. Discussion above of pitch appreciated. Most stabilization techniques only effect roll. Heave and pitch are unchanged. Those with heavy displacement for LOA tend to pitch slower as there’s more boat in the water and there’s a latency until reserve buoyancy at the ends (especially bow) starts to have an effect. Light boats such as some catamarans tend to pitch more. Had one Bermuda race on a multi when the wind died to light air but we were beating into a short period chop. It was unpleasant and you had to hold on to cups and even plates as they went airborne on the fall.
In terms of comfort personally find heavy boats have a better ride most of the time. But when taking seas on the aft quarter tend to set up a rhythm of corkscrewing which can be unpleasant. Sometimes to the degree it’s worthwhile to change course a bit. There’s three groups of people. Those more sensitive to low frequency motions. Those to high. Those to both. Threshold where it becomes a problem varies between people. Light boats and those dependent upon form stability tend to give high frequency motion. Narrow boats tend to roll more. Wife has never gotten seasick and can sleep through anything. Still she doesn’t like heave or corkscrewing. Finds it makes it harder to move around.
Seems this discussion has been aimed at roll not the other vectors of movement. Perhaps because we’ve been talking about boats not ships that’s all that is practical. But the other movements are equally important to comfort. It has been tangentially mentioned. Such as SD boats going on plane or near plane when pitch decreases. Or use of interceptors. But features such as bow configuration, length to beam ratio, displacement, rocker, chines and other hull characteristics are important as well. Be interesting to expand this thread to include more than just roll.

 

[rslifkin]

Personally I find that corkscrewing is the most unpleasant motion with rolling next in line (especially a snappy, fast roll). Pitching generally doesn't bother me unless it's particularly violent where sitting at the helm can feel like I'm being whipped forward and back.

The same motion can feel very different from a different part of the boat too. On one ride with some annoying rolling and corkscrewing, I went down to the forward head. From up there, the ride felt much better than it did from the helm, as the sideways motion of the corkscrewing was far less noticeable further forward on the boat.

 

[mvweebles]

People forget boats move in three axises. Discussion above of pitch appreciated. Most stabilization techniques only effect roll. Heave and pitch are unchanged. Be interesting to expand this thread to include more than just roll.

It must have been lost, but I mentioned way upthread (twice) that while newer fin technology combat pitch and yaw, gyros are likely the most effective defense.

But the topic does deserve some attention. Just comparing gyros to find - my sense is because fish are placed abaft the beam and trail behind the boat, they potentially accentuate pitch, not reduce it.

Classic west coast trawlers (Monk, Defever, Garden) have modest reserve buoyancy in the bow. These tend to go through vs over head seas. Yes, wetter ride, but less pitch. .

Related question becomes what happens when a boat doesn't pitch or yaw? Are there undesirable consequential reactions? I'd guess that a lot of the motion attributed to pitch is deceleration from hitting a wave, not just the up/down movement of the bow. An appropriately designed bow mitigages (Hippocampus' N42 with its plumb bow is a good example - GBs are another). But let's consider a boat with a lot of bow flare - would attenuating pitch drive the bow further into a wave thereby increasing deceleration? Would pitch-attenuation actually result in a worse ride due to deceleration forces? Likely only when head seas are above a certain size relative to the boat.

I could never get my head around corkscrewing (yaw). It's a problem entering harbors along the west coast as the swell and seas are almost always abaft the beam. Counter-steering too quickly seems to have negative results. To some extent, delaying helm response for several seconds seems to be best as the boat often regains its footing once the wave passes. I struggle to guess what would happen if the movement were attenuated - would there be unintended consequences?

Good sub-topic

Peter

 

[rslifkin]

It must have been lost, but I mentioned way upthread (twice) that while newer fin technology combat pitch and yaw, gyros are likely the most effective defense.

But the topic does deserve some attention. My sense is because fish are placed abaft the beam and trail behind the boat, they potentially accentuate pitch.

Classic west coast trawlers (Monk, Defever, Garden) have modest reserve buoyancy in the bow. These tend to go through vs over head seas. Yes, wetter ride, but less pitch. .

Related question becomes what happens when a boat doesn't pitch or yaw? Are there consequential actions?

Returning to pitch, I'd guess that a lot of the motion attributed to pitch is deceleration from hitting a wave, not just the up/down movement of the bow. An appropriately designed bow mitigages (Hippocampus' N42 with its plumb bow is a good example - GBs are another). But let's consider a boat with a lot of bow flare - would attenuating pitch drive the bow further into a wave thereby increasing deceleration?

I could never get my head around corkscrewing (yaw). It's a problem entering harbors along the west coast as the swell and seas are almost always abaft the beam. Counter-steering too quickly seems to have negative results. To some extent, delaying helm response for several seconds seems to be best as the boat often regains its footing once the wave passes. I struggle to guess what would happen if the movement were attenuated - would there be unintended consequences?

Good sub-topic

Peter

Pitch is an interesting one. On my boat (fairly full bow and quite a bit of flare forward) dropping the trim tabs a bit at lower speeds makes the pitching motion significantly more comfortable (and reduces it a bit). It does push the bow a little bit deeper into the waves (and can make the ride slightly wetter), but it greatly reduces the most violent of the motions.

The worst is when the bow comes into a wave, gets tossed up quickly and significantly, then comes down in the trough, leading to a large, rapid pitch. By applying some force to hold the bow down (the effect of the tabs increases as the bow comes up and the angle of the boat changes) the bow tends to follow the water more and with a better damped motion rather than the boat over-reacting in pitch.

 

[mvweebles]

Pitch is an interesting one. On my boat (fairly full bow and quite a bit of flare forward) dropping the trim tabs a bit at lower speeds makes the pitching motion significantly more comfortable (and reduces it a bit). It does push the bow a little bit deeper into the waves (and can make the ride slightly wetter), but it greatly reduces the most violent of the motions.



The worst is when the bow comes into a wave, gets tossed up quickly and significantly, then comes down in the trough, leading to a large, rapid pitch. By applying some force to hold the bow down (the effect of the tabs increases as the bow comes up and the angle of the boat changes) the bow tends to follow the water more and with a better damped motion rather than the boat over-reacting in pitch.

Interesting sidebar. Before the Carter-era Luxury Tax crushed the US boat building scene, sailboat design in California was probably the hotspot of innovation. A designer/builder out of Santa Cruz - Bill Lee - had the motto "Fast is fun." He designed and built "Merlin," a 52 foot sled with a very fine bow designed to pierce waves. A legendary boat that set and held TransPac records for decades (California to Hawaii). The design became a production boat that, along with larger J-Boats, essentially created the Racer/Cruiser class of boats that likely influenced Steve Dashew to leave his Columbia 50 behind and build his Sundancer line of boats.....design attributes that greatly influenced his FPB boats. Concept being of course that rather than endure weather, why not improve your odds by spending less time in it.

Peter

 

[koliver]

I can't explain why people think 300# of liquid in a tank on the FB is dangerous but 1,000 pounds of paravane rigging/equipment high aloft isn't. Or maybe those with undeployed paravanes notice the exacerbated roll and significantly reduced stability but stay silent.

The roll dampening of a sailing mast, without paravanes attached, is significant. A sailboat with its mast removed turns into an extremely rolly boat.
Once deployed, a paravane system has both the roll damping action of the weight aloft and the fish in the water.

In an earlier life I was on a Salmon Troller for a summer, so saw firsthand the handy effects of both weight aloft and fish in the water. The rounded, FD hull had a natural roll, but when fishing, hang the Paravane fish from the trolling poles and the roll changed significantly. We were used to staying out until the hooks flying around would be the reason to stop, well beyond conditions that would send pleasure boaters running for cover.

 

[Marco Flamingo]

Just got back (I was towed, but that's another story) from a 3-day shakedown cruise to make sure all systems were go before heading to Canada. Obviously not. But I did get a chance to monitor my "pillow tank" ART.

I anchored in Rich Passage where the Washington State Ferry and the Kitsap Fast Foot Ferry throw out considerable wakes in order to examine roll (Puget Sound being surprisingly calm right now). As to pitch, my wife said that roll was obviously dampened, but there was more pitch. I understood what she was saying, but my inclinometer showed that, with roll dampened, pitch simply became more noticeable, not more pronounced.

Still, what was odd was that upon returning to the marina (towed) and going up to the flying bridge, the pillow tank had rolled completely over (it isn't secured fore and aft and is only held in place between the FB outer coaming because of the tank's length).

The picture below shows it behind and against the single athwartship seat box on my FB. That seat box is a giant cooler installed by the PO. Apparently, its purpose is to save one from constantly staggering down the FB ladder to get more beer. But once modified it would be the perfect place for an ART, hence my interest in playing around with this. The pillow tank had flipped over and back such that the fill on the right side of the tank was now on the bottom. Strange as I don't remember any pitch that would have caused it to roll over and back.

It seems like stabilization may be a bit like whack-a-mole. Reduce one motion and another seems to pop up. Still, pitch isn't as likely to suddenly slide things off the stove when at anchor, so roll will remain the primary target.

 

[Hippocampus]

Have raced and sailed various sleds. Big enemies to fast is fun is weight and the other old saw of that era “flat is fast”. To increase righting arm while decreasing wetted surface very high aspect, deep bulbed fin keels were necessary. Not a viable option for power. Other technique to keep the boat floating on the water instead of in it beyond having an ultralight was to have an optimal gyradius with virtually no weight in the ends. End result was a hull that reached or ran like a scalded cat but wasn’t as good beating to weather and on a
beat had a lousy ride.
Next step was wave piercing bows and slice of pizza hulls. Sometimes done with a hard chine. Now performance at all points of sail improved but at the expense of ride quality compared to a balanced hull with some rocker fore and aft. Some, like John, at attainable adventures, say a balanced hull is preferred for the cruiser. That hull is more comfortable and forgiving in serious weather. Some current powerboat designs have taken up the current thinking about efficiency going long, light and lean. Even putting on minute bow bulbs. Not so much as in the mode of ship construction to move the bow wave but rather the hydrodynamics of wave entry. The side benefit of the LLL hull is its relative resistance to pitching but at the expense of lack of form stability to resist roll.
When you lose a stick the ride becomes miserable but your static stability improves dramatically. Cut it away and everyone lies down on the sole amidships with a bucket waiting for the storm to pass. Any weight aloft decreases stability. The higher up the worst the effect. People spend fortunes for carbon to eliminate weight aloft.
My current hull is a mix of weight related righting arm and form stability but with a poor prismatic coefficient as are most recreational trawlers. As with but not as extreme as with Nordhavns there’s a great amount of reserve buoyancy at the bow. Nordhavns and similar designs have such high bows not only to achieve a dry boat but also to have that reserve. With that bow and their considerable weight pitching is less. Ride more comfortable. One tends to think about the bow when contemplating pitch. But remember for the bow to go up the stern must come down. Having reserve buoyancy aft should also decrease amplitude of the motion. Boats with the engines or other weight near the stern and little reserve buoyancy maybe less comfortable. On plane once you dig out of the hole you pitch less. You have lift in your stern.
MF your wife maybe right. (My wife always is-lol). Think of a pendulum like the bird sipping at the cup toy you had as a kid. One could think there’s an initial inertia to movement in the fore and aft plane but once started that weight will want to continue in that direction as per Newton. So having that weight high up could increase pitch. Once the wave has pasted under you the reverse happens. After a few cycles the effect is noticeable. Would need a recording of the oscillations with the ART full and empty in the same conditions to judge.
That effect would be much less in sail as the propulsive vector is always forward so would be greater than the effect from the weight of the mast. BTW my impression has been sailboats pitch more under power with the sails down.

 

[mvweebles]

... One tends to think about the bow when contemplating pitch. But remember for the bow to go up the stern must come down. Having reserve buoyancy aft should also decrease amplitude of the motion. Boats with the engines or other weight near the stern and little reserve buoyancy maybe less comfortable. On plane once you dig out of the hole you pitch less. You have lift in your stern.

So.....one N46 I delivered from Dana Point to Blaine WA had particularly heavy head-seas, so I thought a LOT about the bow on that trip. The owner had a newer copy of Voyaging Under Power, the version updated by PAE's Jim Lieshman. He discusses the design...and what he would do differently. One item was to extend the waterline by a foot by making the bow less fine. From my perspective, the fuel tanks were too far aft and since I'd filled them prior to departing, still had a LOT of fuel aboard. The combination of the bow design and the full tanks made for a pretty active ride, too active (Hobby Horse comes to mind). The next couple N46s I delivered north, I did not top-off tanks. Helped quite a bit. BTW - the boat had both fish and fins (circa 2000). No effect on pitch.

Peter

As a side-note, I would think that paravanes would attenuate corkscrewing. The newer style of fins should help too, but would think Gyros would be most effective.

 

[mvweebles]

Next step was wave piercing bows and slice of pizza hulls. Sometimes done with a hard chine. Now performance at all points of sail improved but at the expense of ride quality compared to a balanced hull with some rocker fore and aft. Some, like John, at attainable adventures, say a balanced hull is preferred for the cruiser.

I was once aboard Merlin at dock. A far cry from the SC52 cruise/race layout (https://sailingmagazine.net/article-permalink-2293.html), she was a hollow tube with a Wilcox Critenden Skipper head in the middle, right above the keel bolts. There were a few pipe-bunks, and something that passed as a galley. Everything else was a sail-loft. Clearly, every possible compromise for performance had been made.

Apparently, she is still competitive. In April 2019, she set a course record for St Petersburg to Isla Mujeres MX on it's 50th Anniversary of the race.

Peter

 

[socalrider]

Just comparing gyros to find - my sense is because fish are placed abaft the beam and trail behind the boat, they potentially accentuate pitch, not reduce it.

I did not know this - why are fish placed abaft the beam and not on center? To avoid stuffing the bow?

 

[Jeff F]

A designer/builder out of Santa Cruz - Bill Lee - had the motto "Fast is fun."

I've always been a fan of his boats, and have had a few high performance sailboats < 35' that followed that motto.

I recently attempted to buy a MacGregor 65 pilothouse sailboat as a replacement for Escapade. Part of me is relieved that the deal didn't happen, but I'm still drawn to long, light and lean, and to sail vs power for extended offshore use.



Sent from my moto g play (2021) using Trawler Forum mobile app

 

[mvweebles]

I did not know this - why are fish placed abaft the beam and not on center? To avoid stuffing the bow?

From memory, Beebe discusses optimal placement being 1/3rd of the boat's length forward of the transom. I'm sure he has an explanation (could be as you suggest), but suffice to say, they are recommended to be aft of the bow/transom centerline. Has the benefit of making them a bit easier to launch and retrieve. But I may have this wrong - memory isn't what it was before a mis-spent youth.

Peter

 

[Mako]

I anchored in Rich Passage where the Washington State Ferry and the Kitsap Fast Foot Ferry throw out considerable wakes in order to examine roll (Puget Sound being surprisingly calm right now). As to pitch, my wife said that roll was obviously dampened, but there was more pitch. I understood what she was saying, but my inclinometer showed that, with roll dampened, pitch simply became more noticeable, not more pronounced.

So what were your measurements?