Single Screw Handling in Following Seas

[gaston]

Another 32 'IG owner with a single 330hp Cummings Im extremely glad the original owner opted for the 330hp upgrade over the standard 220hp when there is a big wave chasing me

[markpierce]

Not aware of any autopilot that anticipates following waves. If significant waves, I go manual and pay attention to my pants seat.

[Al]

Originally Posted by markpierce

Not aware of any autopilot that anticipates following waves. If significant waves, I go manual and pay attention to my pants seat.

Point taken!!

[Al]

Originally Posted by GFC

Every had one of those AHA moments? I did today after reading through this thread. It got me thinking about a trip we were on in June, 2016 where we ran into some big waves on the Columbia. I had a thread about our experiences here: http://www.trawlerforum.com/forums/s...lor-26868.html


What I wondered about was why, after we had turned around and had the big waves on our stern, the boat did not display any of the characteristic "wave pushing on the stern causing the bow to swing to one side or another" that can lead to a broach.


So I looked at some of the pics I had taken when we were getting the boat ready for shipping out west. I found this picture and enlarged it. It shows how the stern is not flat but rather slopes downward. There isn't a flat surface for a wave to push against until it gets below the water level (shown on the picture with the arrow) and at that it's only a few inches tall. Not much there to push against so nothing to cause the boat to broach.

So there's my AHA moment. Thanks guys!

There you have it. Look at your stern from the aspect of a 'Fan Tail' stern of older both pleasure and commercial boats (1930's) designed to have the following seas roll under the stern, not against the stern. I suspect your boat reacts more favorable than say, my more square stern, at equally low speed of around 5-6 knots. Really slow for you and 3/4 fast for us.
Question: How does the river flow current figure into your traveling with following waves as you describe? I have seen photos where the water is rough and seemingly the waves are going up stream. The Columbia River can be as rough as any water around the Inside Passage I would imagine.

Al-Ketchikan

[Apollo32]

Originally Posted by Shrew

How fast were you actually going when this occurred? In following and quartering seas my stern gets pushed around a lot. I posted on it earlier this year asking a similar question.

I've found a lot has to done with anticipation. start turning earlier when the stern starts coming around. you'll find you may need to start straightening back out earlier as well or oversteering starts to make the issue worse.

In some cases I need to give it a little throttle if I end up hitting the steering locks.

A little squirt of throttle to get more flow over the rudder helps at times. The more I read, I am assuming that it happened because of my flat stern and too slow a speed. This has been a wealth of insight and advice!

[Shrew]

Originally Posted by markpierce

Not aware of any autopilot that anticipates following waves. If significant waves, I go manual and pay attention to my pants seat.

It can, however get the rudder from lock to lock before a human can a quarter turn in. Anticipation, no. But with a fraction of the reaction time, it should help.

[csugg]

I used to have a 26' Pacemaker with a single 350 gas engine. The thing would broach at the drop of a hat if any 2' wave hit the stern. Everybody said "stay on the back of the wave" Didn't have enough power to do that coming in a inlet. I finally starting coming in dead slow and letting waves go under me and had enough throttle left to give a burst of power to straighten the stern if required.

Ches

[Chrisjs]

The swim platform can "catch" waves, especially on a square ended vessel, and increase boat motion. The bigger the platform, the bigger the problem.

[kapnd]

Most if not all modern autopilots claim to have some capability of "learning" how a particular vessel reacts in various conditions, and reacting appropriately.
A test of a Raymarine unit in Salt Water Sportsman from 2013 says:
"The EV core is a nine axis heading sensor that monitors boat movement in all directions ,
Essentially a 3-d sensor. It's driven by a set of sophisticated motion-analysis algorithms , Evolution A1, designed by parent company FLIR's motion control engineers.
The basic technology is aerospace derived, and it has recently seen a lot of success as the key guidance system in autonomous vehicles, which most of us know as drones."
So they're gathering data about boat motion and sea conditions and instantly adapting that to efficiently steer the boat.
It's a far cry from the old compass card controls, and it does work well, especially if you operate in nasty conditions on a regular basis.
Mine works well in big following seas, never feels like it is going to broach, however it is a 50' boat, and LWL has much to do with how a boat reacts to perpendicular seas in either direction.

[GFC]

Originally Posted by Al

There you have it. Look at your stern from the aspect of a 'Fan Tail' stern of older both pleasure and commercial boats (1930's) designed to have the following seas roll under the stern, not against the stern. I suspect your boat reacts more favorable than say, my more square stern, at equally low speed of around 5-6 knots. Really slow for you and 3/4 fast for us.

Question: How does the river flow current figure into your traveling with following waves as you describe? I have seen photos where the water is rough and seemingly the waves are going up stream. The Columbia River can be as rough as any water around the Inside Passage I would imagine.
Al-Ketchikan

Al, 5-6kts on my boat is at dead idle and around 600 rpm's. If I'm in a no wake zone I have to be in and out of gear to minimize the wake, and that's a PITA. I have tried doing it on one engine (the other in neutral) and that's better, but I still have to be in and out of gear. Sea Ray made this boat with a trolling valve on the transmission but my boat wasn't built with that. I wish it had been because when it's engaged it slows the boat to about 3-4kts. BTW, don't ask me how that trolling valve works. I don't know. I've heard of it but have no clue how the thing works.


It's VERY unusual to find waves like we encountered in that video I was shooting when we took green water over the fly bridge. That day was kind of the "perfect storm" of bad conditions. There was a several knot current running opposed to about a 30kt wind. The waves were short duration and steep.


They're not really going upstream, but give the illusion of that because of the wind. Take a look at this video below, look at the whitecaps. They're breaking upriver, against the current. That's what gives the illusion of them going upstream. It's an odd combination of a fairly strong current and high winds that gives them that appearance.

https://www.youtube.com/watch?v=OtfsjCKmzRk

Strong currents are fairly common on the Snake and Columbia rivers, especially in the spring. I've seen 8-10kt currents on the Snake, 5-6kts on the Columbia.


Makes for some interesting boating at times.

[caltexflanc]

I'm with the crowd saying that throttle management is 80% of the game with following seas. Then a modern auto pilot can do its thing much more effectively. However, if you are dealing with highly confused seas rather than a regular period set from one direction, it's pretty hard for either human or machine to steer perfectly when there is no way to "anticipate" anything with high accuracy.

[kapnd]

Originally Posted by caltexflanc

I'm with the crowd saying that throttle management is 80% of the game with following seas. Then a modern auto pilot can do its thing much more effectively. However, if you are dealing with highly confused seas rather than a regular period set from one direction, it's pretty hard for either human or machine to steer perfectly when there is no way to "anticipate" anything with high accuracy.

Yes, that's why the ocean racing boats have a steersman and a throttle man.
It's just too much for one man to do alone!
BTW they don't appear to be using any autopilot.

[Shrew]

Originally Posted by kapnd

Yes, that's why the ocean racing boats have a steersman and a throttle man.
It's just too much for one man to do alone!
BTW they don't appear to be using any autopilot.

Kind of an apples and oranges analogy. A boat doing 100 kts ins't going to have its stern pushed around in an 8 kt following sea.

[Fletcher500]

Interesting. Our past boats had P hulls, so we zipped across them at high speed. The AP had no issues on big swell days, even at lower speeds come to think of it. When entering a channel down here that is known for big swells in the Winter (Mission Bay), I was able to stay behind the wave in front by cranking up the speed to match it.

The single engine SD trawler will be new to us, but with that said, I have spent alot of time on vessels of varying size since I was young and I don't recall ever experiencing the severity noted by the OP. IE, a "32 ft. vessel doing a 180 on 2 - 2.5 ft. swells". I am not saying it didn't happen, and others are validating it, just surprised to hear this.

[AusCan]

I'm also surprised that a 32 foot boat is at risk in 2 foot waves. It would certainly limit the weather windows for boating.

I just checked the local weather. The forecast does not predict the waves to be 2 feet or less any time over the next week. 17 feet predicted on Monday. That will toss a boat around.

https://www.seabreeze.com.au/weather...ecast/adelaide

[psneeld]

2 foot breaking ocean waves and 2 foot curlers in an inlet are 2 different animals.

[caltexflanc]

Originally Posted by psneeld

2 foot breaking ocean waves and 2 foot curlers in an inlet are 2 different animals.

On the ebb no less.
Yep, speed and steepness are the whole game. Like the difference between running into a 2' brick wall or over a 6 foot wide 2' berm.

[AusCan]

It seems to help having minimal flat surfaces other than a large rudder.

[Al]

[QUOTE

[/COLOR]It's VERY unusual to find waves like we encountered in that video I was shooting when we took green water over the fly bridge. That day was kind of the "perfect storm" of bad conditions. There was a several knot current running opposed to about a 30kt wind. The waves were short duration and steep.


[COLOR=black] They're not really going upstream, but give the illusion of that because of the wind. Take a look at this video below, look at the whitecaps. They're breaking upriver, against the current. That's what gives the illusion of them going upstream. It's an odd combination of a fairly strong current and high winds that gives them that appearance.
Makes for some interesting boating at times.[/QUOTE]

In total the view of that water resembles our normal 2-3 foot water. Short waves with white caps. Bucking them is not the most comfortable ride in our 28 foot boat, but as stable as it is now, it is really more a hobby horse issue, not a wild frolicing side to side ride. Those same waves on the stern do cause us to whip yet we can anticipate to the degree that while tiring, not that uncomfortable. Never a sensation of broaching. just a unaware juke if caught off guard.
Thanks for the video
Al-Ketchikan

[C lectric]

If you are using an autopilot increase the response rate if the A.P. allows that. If it is set for a slow response then it cannot react fast enough.
When mine worked I used to crank up the response rate.
Granted it can only react but the rate of reaction should be adjustable. Use it if not done yet.