Semi displacement and quartering seas

[Legend]

There seems to be only one handling characteristic of my Halvorsen that I dislike. It is when I find myself in quartering seas. They lift up a corner of the transom and with the semi displacement deep forefoot she will catch an upcoming wave at an angle creating bow steer. This makes her roll a bit and can be unnerving for passengers. My only solution to that other than a new course is to raise the bow as high as I can to try and avoid bow steer. Any suggestions from other semi displacement boat owners?

 

[caltexflanc]

You don't want to tab it up in a following sea as that will push you around even more. Adjusting the throttles to match the seas is the best way to mitigate the effect. The "roll" you are experiencing is typically more of a combination of pitch and yaw; it is indeed an uncomfortable motion.

 

[Legend]

You don't want to tab it up in a following sea as that will push you around even more. Adjusting the throttles to match the seas is the best way to mitigate the effect. The "roll" you are experiencing is typically more of a combination of pitch and yaw; it is indeed an uncomfortable motion.

Thank you. I will try that approach.

 

[caltexflanc]

You're welcome. Look at the big fat butt on that Hatt; I feel your pain. And remember I said "mitigate" not "cure"!

 

[dwhatty]

Been there, done that in our Halvorsen. Can be truly scary.

 

[markpierce]

This occurs with full-displacement boats too. Experienced it a lot on sailboats. Steering with a tiller provided instant tactile information to apply quick rudder adjustment to minimize effect, although we did experience some knockdowns carrying a spinnaker. With wheel steering, making timely rudder adjustments is more challenging but can be done.

 

[Nomad Willy]

Nothing like a big rudder.

Good fore and aft weight ballance will help too. I have two 50 gal water tanks far aft in my 30' boat and I like to have them fairly full especially when I'm on following seas.

Mark is on the mark as FD boats have some trouble w following seas too .... just far less.

 

[Moonstruck]

Nathan, you got spoiled running your Sabre. The V hull tracks and plenty of power to push you through. The flatter areas of the Halversen's bottom near the stern coupled with the flat transom and small rudders means trouble in a quartering sea. Add to that the steep, close chop of the Chesapeake, and it can get quite uncomfortable.

Like George said take the tabs off to sink the stern. Regulate the speed for the most comfortable ride. This should provide some stability.

 

[BandB]

You don't want to tab it up in a following sea as that will push you around even more. Adjusting the throttles to match the seas is the best way to mitigate the effect. The "roll" you are experiencing is typically more of a combination of pitch and yaw; it is indeed an uncomfortable motion.

The human tendency is that when things get rough to go very slow. Yet, this is a great example of situations where a bit more speed is far more comfortable. It takes a lot of time to learn all the characteristics of a boat in as many different sea conditions as possible.

 

[Al]

BandB has it.

We endured a following sea voyage early this week. While I didn't slow down to meet conditions as the boat was doing well other than the slewing about which being as slow as we are would not have resulted in much more that more time with the issue, During these struggles, a slightly larger simi-dis boat with sufficient power was running on step. Unlike a lightly constructed 'Go Fast' hull, rather a heavy built boat, was not having near the challenge we were under. It was with admiration watching this boat eat up the following seas.

During the past year I have been increasing the amount of lead ballast in our boat. The last installment was an additional 104# in two ingots. The beauty of these ingots is the ability to shift the weight around the bilge. This has allowed us to decrease the slewing effect. We now have a total of 1250# of lead in the bilge plus 400# of additional engine/gear weight with a recent engine replacement. In short, we have a completely different boat from what we bought.

Al-Ketchikan

 

[Nomad Willy]

Al I hope your lead is secure as a big heavy pice of lead slamming about in a boat in conditions where it hard to stand up in is not good.

 

[Scary]

Tendency to broach

This what you are describing. This can get you in trouble as the seas get large enough to cause the boat to surf. With a fast powerful boat surfing can be fun, with a slower boat it can be uncomfortable and potentially dangerous. Small rudders and hard chines make it more difficult to keep your boat tracking straight. If you have trim tabs don't run them in the down position, this make it worse, The 4788 bayliner has a warning label at the tab controls against this. if you can run at the speed of the waves this will help, keep your boat on the back side of the waves as much as possible. This uses more fuel but provides better tracking. If you can, try and run as square to the waves as possible, this may mean holding a course other than rumb line. Be careful not to end up having to finish your approach with beam seas. This condition is common on south runs on the west coast. What I do is take advantage of the smaller waves to move the boat back towards my track, sort of a controlled s shaped course ridding the back of the larger waves and working toward my track on the smaller ones. You will actively have to drive your boat in these conditions. A good Auto Pilot will get you there but it won't be pretty or comfortable. I've been on boats that Yaw as much as 40 deg. I've also been on boats like 48 lrc that track like there on rails.

 

[BandB]

Tack like a sailboat if you can't find a comfortable speed. Lengthens the trip but makes it more comfortable.

 

[Al]

Scary, You have just described our voyage. While speed was not a factor in this case, all of the other identifiers with a displacement hull are confirmed.


Eric- The lead is in ingot form, like gold bars. They are stowed in the keel alleyway on top of the inlayed 1500# of original build secured under a fiberglass floor. These additional ingots are layed end to end two ingots high and are in effect 'jammed' into place requiring a screwdriver tip to jack one up should that be required. Others of the ingots are layed alongside the engine bed and secured with 'Gorilla' tape in both directions. Used the widest width of tape and double taped the parameter of the ingots. Appears to be satisfactory to this point.
Having the ability to move the ingots has allowed me to find a friendly ballasting in terms of ending the severe 'hobby horse bucking into seas and for sure, having a most comfortable minimum angle in beam seas allowing the boat to remain on even keel in those 'almost' beam sea conditions.

Don't I have a memories of you saying you have 3000# total of dedicated ballast in your boat? If that is correct, then my 2700# of dedicated ballast is close.
From the first post made regarding the horrid sea actions of this boat upon first exposure to our SE waters to now has been a story. Now Eric, the bitching about slewing in a quarter following sea represents the only quadrant of discomfort while underway, all others are so much improved.
regards,
Al-Ketchikan

 

[Rustybarge]

This what you are describing. This can get you in trouble as the seas get large enough to cause the boat to surf. With a fast powerful boat surfing can be fun, with a slower boat it can be uncomfortable and potentially dangerous. Small rudders and hard chines make it more difficult to keep your boat tracking straight. If you have trim tabs don't run them in the down position, this make it worse, The 4788 bayliner has a warning label at the tab controls against this. if you can run at the speed of the waves this will help, keep your boat on the back side of the waves as much as possible. This uses more fuel but provides better tracking. If you can, try and run as square to the waves as possible, this may mean holding a course other than rumb line. Be careful not to end up having to finish your approach with beam seas. This condition is common on south runs on the west coast. What I do is take advantage of the smaller waves to move the boat back towards my track, sort of a controlled s shaped course ridding the back of the larger waves and working toward my track on the smaller ones. You will actively have to drive your boat in these conditions. A good Auto Pilot will get you there but it won't be pretty or comfortable. I've been on boats that Yaw as much as 40 deg. I've also been on boats like 48 lrc that track like there on rails.

Very interesting; why is the Hatt so good at tracking....what's different about the transom?

I notice there's some deadrise, does this help?

 

[caltexflanc]

If you have trim tabs don't run them in the down position, this make it worse, The 4788 bayliner has a warning label at the tab controls against this.

Thanks for the important clarification. So does the Hatteras. I think my post may have been confusing, by "tab it up" I meant using tabs to raise the stern like you do when planing. The tabs themselves need to be fully up. When they are down, thats more surface to get pushed around and, more dangerously, guiding the bow down into the seas.

As for tacking, that's fine in open water and helps some. The most pucker-inducing situations are coming into an inlet in mediocre conditions. In poor or bad conditions, just don't do it.

FD boats with canoe sterns do much better in following seas. Some of the issues in quartering is the very deep keel something like a sail boat has will cause the boat to track more determinedly in the direction it gets pointed after being moved by the sea, requiring vigourous helmsmanship. The Hatteras (ours in this case) also has a modestly deep keel, and that's when having the ability to go faster is a real bonus.

 

[Codger2]

"You don't want to tab it up in a following sea as that will push you around even more." .

George, I've been thinking about that remark ever since you posted it. I've interpreted it to mean that you never want to trim the trim tabs to a "bow up" configuration in a following sea." I've been taught just the opposite! By trimming to "bow up", you minimize the boat trying to bury its bow when on the front side of a wave. Of course, manipulating the throttles to match the sea conditions is a given. I wish more on TF would add their 2 cents to this question.

 

[BandB]

George, I've been thinking about that remark ever since you posted it. I've interpreted it to mean that you never want to trim the trim tabs to a "bow up" configuration in a following sea." I've been taught just the opposite! By trimming to "bow up", you minimize the boat trying to bury its bow when on the front side of a wave. Of course, manipulating the throttles to match the sea conditions is a given. I wish more on TF would add their 2 cents to this question.

George clarified and meant exactly what you say. My understanding is the same. Put another way, "Don't bury the bow."

When you're "practicing" that's something else to work on is the proper and best use of your trim tabs. "Practicing", you ask. Yes. Find space where you won't put yourself in harm's way as you would in an inlet. Don't learn when you have no way out. When you're out cruising, take time occasionally in different conditions to see how your boat behaves and how you can handle it. When we were first learning we were put through hours of practice in the gulf in rough conditions and trying with the waves coming from every possible different direction. That's where we learned the way to match speed to conditions, the impact of the various levels of tab. By the time our "teacher" said to let's go in, we knew what we needed to do for the inlet. Not only had our knowledge and skill changed, our instincts had. Our first and most natural thoughts were different.

As Caltex states too if you can't find a safe means of handling the inlet with conditions and your specific boat, then wait or find somewhere else or somehow rethink things. Perhaps ask the CG for suggestions or options, check forecasts. If opportunity to observe others presents itself then do so. We had a Gray's Harbor for Dummies course just observing all the charter fishing boats. It was our first time ever to see 10'+ swells, but they faced them regularly.

Also, give yourself all the room for error you possibly can so if you do get pushed off track you have the time and space to recover.

 

[Nomad Willy]

Can anyone think of a positive reason to use trim tabs in following seas or while running an inlet?
In such conditions I'd raise the tabs and forget about them. But I've never had tabs so I may be missing something.

There's talk of "why is the Hatt so good at tracking". Is it?
Any twin will be able to power steer and drag steer (w one prop at idle speed).
A high LB ratio may help.
The drag of a deeply submerged transom will help.

But why would a Hatt track better than the average boat of her type?
Not much keel.
Not much deadrise aft.
Small rudders.

Is lots of beam carried far fwd? As in wide chines fwd?
She has a very nice forefoot much like a FD hull. Could this be an advantage? I don't see it myself but for a SD/Cruiser hull having a sharp forefoot and the rudders well aft would definitely help tracking most of the time.

Codger I fully agree re bow up.

 

[caltexflanc]

Can anyone think of a positive reason to use trim tabs in following seas or while running an inlet?
In such conditions I'd raise the tabs and forget about them. But I've never had tabs so I may be missing something.

Nope, missing nothing, you are exactly right . That's why boat manufacturers like Hatteras and Bayliner mentioned above actually put warning labels next to the tab controls.

 

[Codger2]

Can anyone think of a positive reason to use trim tabs in following seas or while running an inlet?

As has been posted...Trim for "bow up" in a following sea. Also, trimming in a quartering sea really helps with the ride.

 

[Scary]

The Hatteras has an interesting hull shape

Very interesting; why is the Hatt so good at tracking....what's different about the transom?

I notice there's some deadrise, does this help?

If you look at the LRC hull it has a fairly flat aft section, however the bulk of the hull is very rounded. The flat aft section is large enough to provide primary stability to the hull at rest and to prevent the stern from squatting at hull speed. The large keel and rudders plus the 66,000lbs with fuel probably is as large a component. Active fins help as well. When the following wave lifts the stern boats heel in the opposite direction as the broach, the fins try to correct that heel forcing the boat to try to run straight. Years ago when I raced dingy's we would induce surfing by hiking hard on the top of the wave counteracting the dingy's attempt to broach, the boat would squirt off the top of the wave and plane. These big displacement boats don't plane but the fins act like we did when we were hiking out and keep the boat tracking straight.

 

[Marin]

Steering successfully in a quartering aft sea is simply a matter of timing. The trick is to anticipate the next wave and put the steering correction in before the boat starts to yaw. Then take it out before the boat starts to yaw back the other way. Waiting until something happens to take action will cause you to continuously be behind the curve and you'll be chasing the boat forever.

We learned this early on with our 30,000 pound flat-transomed PNW cabin cruiser and today we find it very easy to maintain a nearly connstant heading even in three and four foot aft quartering seas. It keeps you busy at the wheel but we find it a rather enjoyable challenge. It's all about knowing the reaction characteristics of the boat, understanding its inertia, and timing.

We used to be a bit fearful of aft quartering seas. Today they're just another thing that keeps boating from getting boring.

 

[BandB]

Can anyone think of a positive reason to use trim tabs in following seas or while running an inlet?
In such conditions I'd raise the tabs and forget about them. But I've never had tabs so I may be missing something.

Ther are boats in which raising tabs all the way up leads to other issues, including lack of tracking and/or porpoising even. While this wouldn't likely be an issue in a Hatteras or Bayliner it might in other boats, especially sport or performance boats.

 

[caltexflanc]

Yeah right. Anticipate this:

 

[Rustybarge]

If you look at the LRC hull it has a fairly flat aft section, however the bulk of the hull is very rounded. The flat aft section is large enough to provide primary stability to the hull at rest and to prevent the stern from squatting at hull speed. The large keel and rudders plus the 66,000lbs with fuel probably is as large a component. Active fins help as well. When the following wave lifts the stern boats heel in the opposite direction as the broach, the fins try to correct that heel forcing the boat to try to run straight. Years ago when I raced dingy's we would induce surfing by hiking hard on the top of the wave counteracting the dingy's attempt to broach, the boat would squirt off the top of the wave and plane. These big displacement boats don't plane but the fins act like we did when we were hiking out and keep the boat tracking straight.

Thanks. I hadn't considered the righting actions of the stabs giving directional stability.

 

[Nomad Willy]

Something else that occurred to me re tracking.

The keel dosn't extend very far aft and the rudders are rather small. But the sides of the aft quarter between the chines and the water line provide a surface on each side of the boat that probably acts much like the feathers on an arrow. Any yawing would need to overcome the flat submersed hull sides. Also at or near hull speed the returning bow wave will be pushing inboard on both sides of the hull aft. The above combination could result in strong tracking. I might add that lots of other trawlers would benefit from this too. The IG comes to mind.

 

[Rustybarge]

The Corvette 320 manufactured in England, but now owned by Fleming, has a very strange hull shape; its like two canoes glue down each side of the keel.

https://en.m.wikipedia.org/wiki/Corvette_Motoryacht

Its got a good reputation for straight tracking and virtually no roll with 13' beam; surprisingly enough the hull does not suffer from slamming at 20kts.

Is hull design based on dumb luck?

 

[Nomad Willy]

No it's certianly not dumb luck. Some creative designer just had the guts to get out of the box. And it's not new. Just new with this size and type of boat. Many sit-on-top kayaks employ the same hull displayed in the Corvette.

 

[Rustybarge]

Many sit-on-top kayaks employ the same hull displayed in the Corvette.

My son paddled from Nice in France to Rome in Italy in a sea kayak in some very variable weather; always felt the kayak was capable of taking everything in its stride.

IMO most boats are seaworthy, but the handling chararistics can vary enormously .

Even modern trawler designs like the Beneteau swift 34' suffer from ' bow steer' in a following sea, according to a MBM test I read; and Beneteau even advertised in the mag so it must have been quite bad to warrent a mention. ( now defunct).

Someone on the mbm forum is refitting a Corvette 320 , so I will ask about sea handling in a following sea....