Is there a rule of thumb you use for rough seas?

[Chinookie]

First, I possess little knowledge of seamanship. Eight years ago I ventured out with my son in a Northriver Seahawk, leaving La Push in a easterly wind. Midway to a halibut spot I had never been to a Coast guard rescue craft flew by me with lights flashing. I decided to turn back, as that looked to be a bad omen. Immediately two things happened. First, we began taking green waves over the bow, and then the bilge pump chose that exact moment to die. I quickly learned, with no prior knowledge, how to throttle back so as not to stuff the bow quite so bad. I never took that boat to the ocean again, because those tiny drain ports on the bow are useless with a stuffed bow.
Now I own a Grady 228, a very different boat, but a small boat nonetheless. I would like to know if there is a simple formula I can use to keep myself alive when planning. Something like wind waves plus swell never more than X1 when period is Y1 and X2 when period is Y2. Even if you don't own a 228 I could benefit from your personal maximums.
I have begun to study some, and last nights read was on the perils of following seas, and how to stay on the wave with throttle mgmt, but I have much to learn. Especially on the matter of knowing when it's better to go out to sea to stay alive when trying to go back.

The best seamanship is to plan not to be on rough water, but sometimes nature makes new plans. If anyone knows of some good on line reference material I will be grateful.

 

[Late Again Grady]

Wave period three times wave height or more. Not familiar with the west coast but that rule should keep ya safe. Anything over three feet in height, I'd stay nearshore.

 

[Mustang65fbk]

I mean... my personal thoughts on the matter, and without any sort of mathematics into the equation, would be... "am I going to be able to fish by myself? and is this going to be fun?" As mentioned, I typically go out fishing alone, or maybe with one or two other people at the most, but if the winds are 15+ mph or more, it's going to make for some rough fishing with downriggers and trolling for salmon, etc. In which I usually look out at the water from my beach cabin and ask myself the two questions I asked above of "am I going to be able to fish by myself? and is this going to be fun?" If the answer to either of those questions is "no", then I'll typically just go back to bed for a couple of hours, wait until later on in the afternoon to see if the conditions change, as I don't want to be out in them especially if it's going to potentially get worse, etc.

 

[Chinookie]

Thanks for your reply. This is where I get confused. There can be wind waves that are typically short spaced, and then there are swells, which are also spaced, sometimes long sometimes short. I think there can be both at the same time, no? If so, how do I apply the period rule of 3 and does it apply to the waves or the swell, or both? Am I making this too hard?

 

[kirk a]

Rules of thumb are a starting point. Combine those with local experience, and you'll quickly figure it out.

For swells, I like the ratio to be at least 2-1. So for a 3'sea, I'm looking for at least a 6 second period.

Wind chop is different. I boat in a location notorious for wind against tide - Buzzards Bay MA. A NE or SW wind over 15 can be problematic or even deadly with the wrong tide. Even in a 33, fishing in 15kt wind is not fun and relaxing when the fetch is long.

 

[Ekea]

im a 1:2 crowd. if the wave height in feet is half or less than the period in seconds, its good enough. a long ground swell shouldnt bother you too much. if the swells get steep enough to break, you dont want to be out for that.

 

[luckydude]

Wave period three times wave height or more. Not familiar with the west coast but that rule should keep ya safe. Anything over three feet in height, I'd stay nearshore.

Well, your 3 feet thing doesn't work here. I fish 6' @ 9s, it's not pleasant, but you can fish it. The worst I've been out in was 10' @ 12s, that was horrible, never again (I wasn't captain, in a friends boat, he's tougher than I am). 5@9 is getting there, 4@9 is quite pleasant.

In my opinion, swells can be fine if they are spaced far enough apart. X @ 2X is fine for pretty much any value of X. X @ X sucks for any value of X.
Where the math starts to go away is when you have wind chop on top of the swells. 6 @ 9 with no chop is fishable, 6@9 with chop really isn't for me, other people fish it but they are masochists, I'm not.

Getting back to OP's question, it feels like s/he doesn't have instincts on engine trim and trim tabs. Not a judgement, I was like that when I started as well. First learned engine trim, all the way forward to push the bow down, trim it back when you are going into head seas and you are worried about stuffing the bow (that's instinctive for me, I don't even know when I do it, I hear the waves hitting the underside of the bow pulpit and I immediately trim back).

Trim tabs? First of all, the stock ones on a 228, at least on my 2020, are 9x12 and are half the size they need to be. Replace them with 12x18 and it is a completely different ride. With stock tabs, I had to get off the throttle at the top of each swell or the boat would launch. With the bigger tabs, I find the right speed and the right amount of tabs and the boat rolls over the top of the swell rather than launching. Does it make my boat ride like a 27 foot Canyon? No, but it is much, much closer. 90% of the time I can just sit there and never touch the throttle.

In a head sea, where they are spaced close enough that you might stuff, I will lose the tabs and trim the engine back to lift the bow. Watch the Haulover Inlet videos on youtube, you can find examples of people stuffing and also examples of people doing it right. Those doing it right look silly with their bow way up but that's what you have to do. Usually you are a displacement hull at that point, hard to get on plane, not impossible but my experience is when you need to do this, things are sporty enough that being on plane isn't easy. Especially in a 228, mine really needs around 20mph (not knots) to keep it on plane and that is too fast when things are this sporty.

Keep playing with it, the engine trim is easier to figure out, you'll get that quickly. Trim tabs need the upgrade, don't waste your time with those little tabs. Trim tabs are harder to figure out but you will. It helps to point the boat in a straight line and then try to steer with the tabs. When one is down far enough that it will turn the boat, sort of memorize that feel, you will learn to feel it dragging. Once you have that, put them all the way up and then push both down at the same time. Watch the bow vs the horizon, you'll see the tabs push the bow down. If you really feel the drag, that's a little too much, come up a tad.

You can also adjust watching the MPG. If you are too far down, you'll see a .1 mpg drop, or maybe more. That's too much, you want to optimize balancing bow down vs. mpg. There is a sweet spot.

 

[enfish]

I think 2 to 1 ratio of period to seas is a decent rule of thumb, depending on your comfort level. My anecdotal story for the seaworthiness of these hulls is one time I got stuck making the 30 mile crossing from Catalina Island to Dana Point CA is a small craft advisory that was not forecasted. Winds were 25-30 knots, 10-12 foot seas at 8 seconds. We were quartering down swell and had to back the throttle off almost all the way to idle when we hit the crest of a wave to avoid burying the bow on the next one. Then we would have to go almost full throttle to get up the next wave. We were still taking a lot of water over the bow, but the scuppers shed it very quickly and I never felt unsafe in the boat. I remember thinking if the seas got too much worse we might consider turning around and keeping the bow pointed into the waves, but it would have been very dangerous trying to turn the boat around.