Faster or slower in a following sea?

Hi, This is my first post as a TF member. For background, I have a Mainship '08 34T. I cruise in PNW and dislike having to cross or go NS in Georgia Strait! 3'+ chop with short wave length is all too common.

The 08 Mainship34T has a very large fly bridge which makes it perhaps more top heavy than many other trawlers and hence not great in rougher seas. It is also known to have a small rudder.

If you end up in a following or quartering sea, which speed gives you a safer and more comfortable ride? From some reading, there are two potential capsize mechanisms. First is broaching if the following wave spins you around and then rolls you over and second is "bow diving" where you could surf down one wave and bow dive into the one ahead which then also spins you around as the bow slows rapidly and the stern keeps surfing.

If you go slower (5-8 knots), the rudder is less effective so maintaining control is harder and getting spun around is easier. Plus it will take longer to get to your destination and hence more chances for something going wrong.

If you go faster (8-12 knots) then you can end up going faster than the wave speed leading to surfing and possible bow dive. But you get to your destination faster and the rudder is more effecive.

So what are the opinions and experience of TF folks in this regard? Has anyone actually capsized in rough waters? Of course, the best strategy is to avoid quartering and following seas...

Many folks say that Mainships (and I sure other boats as well) can take much more than you think, but I am in late 60's and my risk tolerance goes down every year!

Welcome aboard. There are probably several things influencing the boat with a following sea. The shape of the hull and transom will effect the handling. The small rudder will come into play too. I would give it a try to change heading and see if that helps. You may have to tack like a sailboat to get to your destination. Just give each thing and see what helps. Probably changing heading will make quite a bit of difference. Speed may help also, give it a try and see what happens. Good luck.

With a wide, flat transom there comes a point where you have to speed up just to get enough rudder response. Running with the waves at about their speed is usually quite comfy. Running faster and going over the tops depends on the boat. If you can keep the bow up enough to not stuff and broach, the boat is controllable while surfing, and the boat doesn't try to sit on top and just mush around before pitching down and surfing, then you can run over the tops faster than the waves.

Wider wave spacing or taking them at an angle helps too, at it makes it easier to keep the bow from getting stuffed into a wave while the stern is being lifted by another one.

For me, I have the best luck & best ride when I try to match the speed of the waves. This isn't an exact science and if it's REALLY rough, I sometimes have to constantly fiddle with the throttle to stay in the optimal place. I have a small rudder and semi-displacement hull, with not much aft "exposure" to the water.

The key is to be running the boat at the speed of the seas, typically on the back of the wave ahead. Adjusting throttle can be a full time job.

I highly recommend you consider this book. While it's written primarily for sailors, there's a power boat chapter in it and most of the other chapters still have some relevance for power boaters: Drogues, meteorology, waves, seeking refuge, real-life experiences, etc.

Heavy Weather Sailing - Peter Bruce

https://www.amazon.com/Heavy-Weathe...s=heavy+weather+sailing&qid=1593884191&sr=8-1

I took my first surfing lesson in Johnstone Narrows and have tried very hard to avoid further lessons ever since.

There are plenty of boats that can't run at the same speed as the waves. You have to let some go by. The speed of the waves can depend on what is causing them. In Johnstone Narrows, Straight of Georgia, etc., the nastiest waves are often caused by the current running against the wind. In those conditions the waves can be more of a "standing wave" that is going slow (7 knots). It might be possible to keep in the trough on those BUT sooner or later one likely will pass you by.

What often seems to happen is that the wave in front seems to disappear only to reappear directly under you. Now you are going to be on a crest. Time to quickly throttle back and let that one creep towards the bow before hitting the throttle again.

Don't even think about autopilot. When you feel the transom rise because a following wave is going to pass you, you need to make a steering correction long before the AP will register that you are off course. I steer down the wave, much like turning into a skid when driving on snow. Correct the helm for a second, reduce the throttle, and hopefully have an uneventful push from behind before hitting the throttle and trying to stay in the next trough for as long as possible. If the waves are running 8 knots, I just have to expect more than a thrill a minute.

Probably the two most important things about challenging seas are to watch the weather and avoid them and stow everything really good. Nothing like broken plates and stuff on the floor to add to the experience.

People that deal with following seas often, like commercial fisherman, usually have oversize rudders. About 3-4x more rudder area. The larger rudder doesn't cause noticeable drag. Speed, faster or slower depends on the vessel and how steep the waves are. Sometimes you can't go fast enough. I once made 22 knots while making turns for 7 in big following seas. Sometimes the waves get too big and too steep so you have to turn around or lose control.

We were crossing Lake Ontario in about 6’ following seas off the starboard quarter. The auto pilot would swing about 30 degrees back and forth. But it was much less work than me steering all the time so I just accepted the swing. It wasn’t dangerous but rather a bit uncomfortable.

Like you, Comodave, my autopilot doesn’t do a very efficient job in moderate following seas. Nevertheless, I still use it when I safely can. It’s a lot of work to steer in these conditions very long. I try to avoid looking at my wake too often. Too embarrassing!.

I figured that the autopilot was doing about as good a job as I could have done so why not let it work instead of me. It was about 4 hours if I remember correctly and I would have been worn out.

Pocket,
It depends on your hull, rudder, achievable boat speeds (so HP, semi-displacement, etc.) and the wave conditions existing at the time. I know, not a very definitive answer.
What we have found works best most of the time in Georgia Strait (Salish Sea) with our boat is to try our best to match wave speed by usually "speeding up" compared to our normal cruise speed of 7 knots. Between adjusting to match wave speed and trying various course adjustments (often small angle changes), we can achieve the best ride for those conditions.
However, as stated, best avoid the worst conditions of wind over tide!

Another factor I should have mentioned is that if your boat has trim tabs, make sure they are all the way up.

Mentioned are some good tips, I will add tacking may become necessary at some point.

There are many answers that all or some may apply under certain situations....

What may work for an hour or two may change for various reasons.

Peoples biggest mistake is thinking only one method will work all the time.

I prefer to run as fast as I can without being too uncomfy. Usually in the open ocean, stuffing the bow from running too fast is rare the way I see it. Some deep vee boats can run wave top to wave top and have a decent ride. Others may bury the bow in certain conditions at darn near any safe speed. So playing around is all you can do and sometimes the trade off is longer trips but more comfy rides.....

Breaking waves are a different story....and I am not talking whitecaps or a few feet of foam even on big waves... I am talking surf like waves with very steep or curling faces. Again there is no right answer but danger is the key element here. So playing around isn't much of an option, and if you dont have a good feel for dealing with this kind of survival situation.....best to be asking for assistance or avoiding this situation at all costs....until you have the experience and feel confident.

In my Mainship 400, I prefer to go faster, as others have said, running at the speed, or just faster than the speed of the waves. It's one of the big advantages of having twins and the additional speed they provide in the 400.


Aout the worst following seas I have seen in this boat for an extended time was when we came from the Berrys up to Little Harbor cut in the Abacos a few years back and had 6-7 footers with a short period following us from Hole in the Wall all the way to LH, which is about 35 miles. I ran at about 12 to 13 knots, but with TONS of throttle adjustments, and a real workout on the steering.



I try to slow down a bit as the wave crests underneath me, just before I go down the face, then speed back up on the back of the next one. You have to anticipate the steering as well. It's not super easy. I've run my flats boat in pretty big following seas a lot, and I use the same method. It is much faster and more responsive, so it has helped me learn.

Thanks all for the useful replies. It gives me ideas to try. I have tried riding the back of the wave in front. When it works its great. But as mentioned its a lot of work, possibly more in some boats than others. On balance, I guess the quartering sea is worse since any spinning effects are exaggerated and to follow the seas you need to go faster. Avoidance is still the best for me! Thanks again.

This might be useful.

https://www.trawlerforum.com/forums/s59/boat-handling-following-seas-26939.html

Don't be this guy.....

Frankly I can't really answer this question.

It's just a feel thing.

Coming in through some of the east coast inlets is like surfing with a paddle board sometimes. I really can't "remember" how I handled the boat, I just go on manual and use the wheel and throttles (but mostly throttles) to keep her on a heading perpendicular with the waves. In fact I can remember at least one time coming in through Fort Pierce Inlet with a strong outgoing tide versus an easterly wind and I had to go into reverse on an engine a couple of times.

Just get to know your boat over time and how she reacts in different conditions - though also understand you will face new conditions from time to time.

Good luck.

Reflecting back on my following sea experience I think the only time when I had a real preference was when the seas were breaking.
And when seas are big slower is good as you don’t spend a lot of time laboring slowly up the backside of the wave in front of you.
Otherwise it dosn’t make much difference.


Looks like the boat in post #18 burried her bow and gave control to the sea.

Marco Flamingo said:

I took my first surfing lesson in Johnstone Narrows and have tried very hard to avoid further lessons ever since.

There are plenty of boats that can't run at the same speed as the waves. You have to let some go by. The speed of the waves can depend on what is causing them. In Johnstone Narrows, Straight of Georgia, etc., the nastiest waves are often caused by the current running against the wind. In those conditions the waves can be more of a "standing wave" that is going slow (7 knots). It might be possible to keep in the trough on those BUT sooner or later one likely will pass you by.

What often seems to happen is that the wave in front seems to disappear only to reappear directly under you. Now you are going to be on a crest. Time to quickly throttle back and let that one creep towards the bow before hitting the throttle again.

Don't even think about autopilot. When you feel the transom rise because a following wave is going to pass you, you need to make a steering correction long before the AP will register that you are off course. I steer down the wave, much like turning into a skid when driving on snow. Correct the helm for a second, reduce the throttle, and hopefully have an uneventful push from behind before hitting the throttle and trying to stay in the next trough for as long as possible. If the waves are running 8 knots, I just have to expect more than a thrill a minute.

Probably the two most important things about challenging seas are to watch the weather and avoid them and stow everything really good. Nothing like broken plates and stuff on the floor to add to the experience.

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Did you mean Seymour Narrows? There is Johnstone Straits, but don't know of a Narrows by that name. Or are you talking about some other area?

Too many variables for one simple rule. When in a following sea situation, just experiment with different speeds (and headings) and see what works. On my light planing hull I usually have to add power to get good rudder effect, but not too much or you get bow-steer. Got to play with it. And there are times you have to continually work the throttle. Ugggh.

Not much chance to experiment when coming in a rough inlet. Pucker factor there!!

As Ski just pointed out, it's hard to set rules about this one. My heavier planing hull behaves very differently than his. Going too slow does need power added for rudder effectiveness, but going faster doesn't cause bow steer on my boat. My hull is heavily dependent on the trim tabs for stern lift, so it's easy to keep the bow up enough to avoid bow steer. In 3 footers, I usually still have a little tab in if I'm running fast enough to be fully on plane, as no tab puts the bow a good bit higher than needed for good handling.

Some also say they back off on the crests if they're running faster than the seas. Personally, with my boat I haven't found anything big enough to need to do that. I usually just let it climb up, steer it over the top (you'll get some yaw coming over the top unless perfectly aligned with the waves). Then it's surfing time. The bow drops, you hear the engines unload, speed climbs a couple of kts, water noise increases and you feel the boat kinda drop into a groove as you surf down the face. Hit the bottom, engine load comes back up a little, then they load up more as you start to climb the next one. If the waves are spaced so that stuffing the bow isn't a concern and it's not bow steering coming into the troughs, I typically trim so that we end up at close to best speed trim when the bow drops into a surf. Having it higher than that doesn't improve the ride if we're not bow steering and it just costs speed and fuel, plus the deck angle can get almost uncomfortably high while climbing the waves.

For the most part, the best answer is to go out on a day that's not too rough and experiment a bit to see how the boat reacts. As long as you've got at least 2 footers behind you, you'll start to feel how they push on the boat, etc and can figure out what the hull likes. Then you can scale it up a bit if the waves get bigger.

78puget-trawler said:

Did you mean Seymour Narrows? There is Johnstone Straits, but don't know of a Narrows by that name. Or are you talking about some other area?

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That's the area. We ended up going into Kelsey Bay to hide and had to take a couple on the beam to get in past the breakwater. The Harbormaster said that she had one spot left in the jam packed marina, rafted to a commercial fishing boat, before she left for the day (it was late). We talked her into giving us a lift to the first tavern. We got to the tavern and a few minutes later it caught on fire. Drank my beer in the parking lot watching the Fire Department do its thing. A memorable day/night.

Another thing that you might experiment with is timing how fast you can make a 180 degree turn. A single engine will turn one direction faster than the other depending on the hand of the prop. I've never tried to spin a twin engine around between crests. You will likely take one on the beam, so watch and pick a small one.

3' chop won't broach your boat. 15' breaker will. Simple solution, stay out of 15' breakers. But... you might find yourself in a situation where you're in the middle of 10 footers and need to get through. Trawlers are pigs for speed so it's difficult to stay on the back of a wave.

For me the solution is anticipation. I keep my focus astern, and if a see a comber coming that will knock my stern to port, I will steer a little to port first so when the wave throws my stern I end up back on course. I don't just follow the majenta line or steer a compass course.

It takes many hours of helm work before you can anticipate the degree of correction required for each wave but eventually you learn to snake through the water rather than attempting to keep a straight course.

So get out there in the 3-5's and figure out how much your stern is tossed around. Then just put your stern in the right place before the wave hits. If you end up in 8-10's put your lifejackets on.

I agree w SoWhat.

Here in South Florida we have to deal with entering narrow inlets. The seas in the inlet can get pretty steep.

I try to keep my bow on the back of the wave ahead of me and just ride it in. You have to be very quick with the throttle to avoid going over the top of the wave ahead of you or be pooped by the following wave. It’s a real test of your boat handling ability.

Nomad Willy said:

I agree w SoWhat.

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I agree with what Eric agreed with.


There seems to be a lot of Mainship 34 owners posting similar questions about boat handling in following seas. With the small rudder and flat transom, you will always be pushed around by following seas. Watch the swell coming and anticipate, but there is no perfect solution.

As part of our training, we practiced in the Gulf of Mexico in 6'+ conditions and we ran with the waves, against them, and with them hitting us from the side. You develop a feel for the boat you're running and how it reacts in those conditions. The tendency was to think slowing down was the solution but it was the opposite. We practiced surfing as conditions changed and the speed that worked perfectly 30 minutes ago was too slow now. We were lucky that we never needed more speed than we had, but with many boats that is an issue.

Then every inlet, every day will be new and different and you won't handle it just like the one yesterday but the comfort you will develop with your boat will allow you to adjust each time.

I wish I had following seas. Usually, they are coming from some general direction abaft the beam but seem to be coming from all sorts of directions. Trial and error. Slow down. Speed up. Bear off to starboard. Bear off to port. Throttle bursts. Whatever. Sometimes it's just a sh#&show.

No rules apply. Prophylactic dose of meclazine helps.

Peter