Trim Tabs 101:

magicalbill

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For Divajean and any others interested in Trim Tab application and results.

They are like Microwave Ovens; Once you use them you'll wonder how you ever managed beforehand.

To the new Grady Owner unfamiliar with them, they seem counter-intuitive at first; press the starboard toggle switch, the port tab drops and vice-versa. It clears up when you realize what the tabs do.

To start with the bare-bones analysis, you push the toggle switches, the tabs go down and raise the stern, thereby lowering the bow. Right off the boat, they are ineffective at idle speeds. Retract them when not on plane; they just create drag unless your trolling or need to slow the boat waay down underway.

USES:
1.) Load-Leveling Underway:

Deploying for example, the port tab (via the stbd toggle switch), it will raise the stern on the port side, thereby lowering the bow on the stbd side. Cause And Effect also raises the bow on the port side as the stbd bow lowers. Follow? Put your hand in front of you and tilt it to the right and forward. That's what your boat does when you drop the port tab. Most toggle switches have an LED light display, depicting how far down the tab has been dropped.

This is handy when your partner packs 200 lbs of ice in the port livewell and the boat has a resulting list to port on plane. Hit the stbd toggle, lower the port tab, the stbd bow lowers, the port bow comes up and she flies level.

Any deep V hull will lean into a quartering wind on the bow. Gradys are no exception. Correct the lean with whatever tab is required, depending on whether the wind hits you on the port or stbd quarter using the procedure I outlined above. It will fix it no prob.

They also save relationships:

Scenario: Husband & Wife take a day cruise: She's pissed because she's gained a few and no longer looks good in her outfits. The Grady planes off, she's in the passenger seat in a bad mood, the boat is listing to port because of you-know-what. The Husband unobtrusively lowers the port tab, the boat levels and he tells her "You look great..What do you mean, the boats tilting?? It's your imagination!

Marriage Saved; all because of Trim Tabs....

2.) Improving Ride:

Lucky Dude and I have been discussing this concept. Most Gradys after 1992 have the now-famous SeaV2 variable deadrise hull. It starts with an approx 50 degree deadrise in the bow and gradually flattens as you look aft. In a head or quartering sea of significant height and steepness, Gradys tend to pound and slam. This is solved to a degree with your tabs.

Deploy both tabs and the bow will lower as the tabs raise the stern. The idea is to put the bow down so that Point Of Entry where the water hits the hull is as far forward as possible. You want the sharp entry of the bow to split the waves instead of the waves getting a crack at the flatter surface astern. If the Point Of Entry contacts the hull further aft in the flatter section, you will experience pounding and the helmsman will be especially uncomfortable as it will be slapping the hull directly underneath him or her.

Realize that the boat will not stay perfectly level as you depress both toggles to lower the tabs simultaneously. You will have to adjust one tab then the other to fine-tune the process and keep the boat level as you drop the nose. It will become intuitive after a short time.

As the very wise Doc Stressor has said, it's not an efficient running attitude when you have both tabs deployed. As mentioned, the whole idea is to lower the bow for a smoother ride and the trade-off is putting more hull in contact with the water underway, creating more drag. You get a smoother ride, but less MPG. Life is a trade off....

Engine trim also helps with lowering the bow and smoothing out the ride, but not to the degree the tabs do. I will not go into that concept in detail here otherwise our very cool Moderator, Seafarer 228G will Ban me for hogging the system. In my humble opinion, 2 to maybe 3 bars on your trim gauge is a good running angle for the engine if you plan to utilize the tabs to lower the bow.

I consider this VERY IMPORTANT if not ESSENTIAL to your tab education:

1.) When you first start out to learn them, find a stretch of calm, or relatively calm water like a bay or river where you can run for an extended period on plane. It is much easier to learn how the tabs work when your not fighting a rough sea and the boats pitching.
Many people press the toggles, nothing happens immediately, they keep pushing down, and all of a sudden the boat is leaning like crazy to one side and they get startled. Deploy the tabs in short bursts, then pause and wait for the result. It will be a delayed reaction and you won't be over-correcting constantly.

Take your time! Stay in that bay or river until you are thoroughly familiar with how the tabs effect your boats handling and attitude. As you get to know them, they have the potential to become your New Best Friends.

As Columbo says, "One More Thing." Most newer Gradys have an auto-retract feature that fully retracts the tabs when the ignition is shut off. if your does not, be certain to retract them BEFORE you have your Grady fork-lifted out of the water. If the forks happen to contact the tabs when the driver lifts the boat up, the resulting weight on the tabs could damage them. Same procedure when cranking the Grady onto a trailer; make sure the tabs are fully retracted.

Thanks for reading; I was hoping to make this shorter, but I can't seem to, and it's so hard to change Late In Life.....
 

Doc Stressor

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Good info!

Just to expand on the tabs vs trim angle point: The most efficient engine trim position for most hulls is that which puts the anti-ventilation plate in parallel with the keel of the boat. Trimming in any further just creates unnecessary drag if you have tabs. You are pushing the anti-ventilation plate into the flow of water if you trim in too much. As majicalbill said, get the engine in a mid trim position and use the tabs to bring the bow down. You can check for alignment with the keel of the boat while it is out of the water. Note the number of bars or the %trim shown on your gauge. Try not to trim in any more than that.

As far as engine mounting height goes, yours seems to be in the stock position. In water that is not too rough, have someone else take the helm and take a look at your anti-ventilation plate while the boat is cleanly on plane. There should be very little water running over the top of the plate. If there is, try moving your engine up to the #3 hole. Quite a few 228 owners have had good luck with this. It will help your fuel economy, give you a few more mpg, and maybe change the running angle of the boat.
 
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luckydude

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Good info!

Just to expand on the tabs vs trim angle point: The most efficient engine trim position for most hulls is that which puts the anti-ventilation plate in parallel with the keel of the boat. Trimming in any further just creates unnecessary drag if you have tabs. You are pushing the anti-ventilation plate into the flow of water if you trim in too much.

But isn't that exactly what the trim tabs are doing? It's a flat surface angled down so it lifts the stern. Trim tabs are more adjustable to level the boat but I don't get why they are magic and the anti-ventilation plate is "bad"? Seems like you could use both.

And sorry, don't want to sound like I'm arguing, I'm an engineer, I like understanding stuff.
 

Doc Stressor

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If you use the tabs to lift the stern, the anti-ventilation plate is still in line with the keel if you have the engine trimmed properly.
 

magicalbill

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Doc said it better than I did on my Private Message to you. I feel there's little to be gained by full negative trim along with tab deployment due to the inefficient engine running angle, as stated before. The tabs are doing the work. To me, trimming up a bit eliminates that bit of drag from the lower unit angle being all the way tucked in while the tabs keep the bow down.

(To touch on the other topic, the engine may well be working equally as hard with tabs down as with full negative trim. However, I think any wear-and-tear will be minimal, if any, over time and not be realized during your ownership period.)

I would suggest the procedure below to put it in perspective.

When you do your calm water experimenting, run comparisons with the tabs fully deployed. Make one pass with the engine trim on 2-3 bars. Observe the bow angle and study the boats handling tendencies at that setting. Then make another pass (at the same speed) with full negative trim and compare & contrast the difference. If there is no noticeable difference, trim the engine out a bit and decrease your drag. If negative trim gives you noticeably more drop in the bow, and the boat just feels better to you, use it.


I use full negative trim when I put my Marlin on plane, then trim up as she goes "over the hump." Otherwise, the wheels cavitate as the boat picks up speed. That's really the only time I trim all the way down.
 

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Several people have said 2 or 3 trim bars, so I wonder what gauges you are using. I run the gauge below, and that 8 bars is where I run most of the time. And no, I am not one of those boaters running around with the bow pointing to the sky, I am slightly bow up, with the bow wake breaking in front of the windshield. I don't get there by looking at the trim gauge, I am always trimming to get the best number on the fuel flow gauge. It seems logical to me that the most efficient running angle also happens to be the most comfortable. I use trim tabs in moderation, to level the boat, or to match sea conditions. I always try to raise one, instead of lowering the other. If that gets the desired result, it's less drag in the water.
If I had to run negative trim, or full tabs down, it would mean that I got caught in some unexpected conditions, and I would be trying to get back inside the inlet, not going out to fish.1599438258042.png
 
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magicalbill

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Bars are different on our gauges. My 2018 Yam 350's run most efficiently at between 4-5 bars. (I was suggesting 2-3 bars for moderate trim with tabs down as per our discussion, outlined above.)

My input was assuming Lucky Dude's trim gauge is the same as mine. You have the older style gauges, my '07 F200's had that cluster.
 

Divajean

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Several people have said 2 or 3 trim bars, so I wonder what gauges you are using. I run the gauge below, and that 8 bars is where I run most of the time. And no, I am not one of those boaters running around with the bow pointing to the sky, I am slightly bow up, with the bow wake breaking in front of the windshield. I don't get there by looking at the trim gauge, I am always trimming to get the best number on the fuel flow gauge. It seems logical to me that the most efficient running angle also happens to be the most comfortable. I use trim tabs in moderation, to level the boat, or to match sea conditions. I always try to raise one, instead of lowering the other. If that gets the desired result, it's less drag in the water.
If I had to run negative trim, or full tabs down, it would mean that I got caught in some unexpected conditions, and I would be trying to get back inside the inlet, not going out to fish.View attachment 15826
Now I'm understanding thecocept,gonna see where my trim gauge is when the plate is leveled to keep keel tomorrow, then I can learn the tab effect thanks to everyone for the info
 
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Blaugrana

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Thanks for all the helpful information here....

So, I feel like I have figured out the trim tabs on the everyday chop in my bay. However, I went out in some 20-30mph sustained winds one day and wasn’t really sure if I should slow down, stay on plane, raise the bow, etc.

When the waves are closer together, I’m good as I feel like the boat never drops off and can glide from one wave to the next. The boat feels like it is always on 2 waves at a time. On that one day, there were 3ft waves close together but every once in a while there would be a gap long enough that made me indecisive and it felt like I would ride down the wave before the next one would hit the hull. I found myself slowing down to raise the bow but then I got off plane.

What’s the thoughts on the tabs in relation to choppier waters? Do you still want to have the bow cut the waves or take further back? Where do you draw the line from cutting the waves vs stuffing the bow?

I am planning on heading out my inlet and into the ocean for the striper runs this fall but still unsure of how best to use the tabs in more adverse/ different wave conditions/ style.
 

glacierbaze

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"I am planning on heading out my inlet and into the ocean for the striper runs this fall but still unsure of how best to use the tabs in more adverse/ different wave conditions/ style. "

Just remember that if you are running with a following sea, which will happen often coming back to an inlet, keep the tabs all the way UP, and the bow up. When you start over a crest, power up and get off the face before it can build on your transom, and treat you like a surfboard. That's not the time to be timid.
 

wrxhoon

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Good info!

Just to expand on the tabs vs trim angle point: The most efficient engine trim position for most hulls is that which puts the anti-ventilation plate in parallel with the keel of the boat. Trimming in any further just creates unnecessary drag if you have tabs.
Agreed when you have the engine hanging on the transom, totally different when you have a 3 foot bracket, like the late model 228's have . As a rough guide you go up one inch every foot . In any case when on the plane you should get very little water over the anti ventilation plate .
 

SeanC

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”To the new Grady Owner unfamiliar with them, they seem counter-intuitive at first; press the starboard toggle switch, the port tab drops and vice-versa. It clears up when you realize what the tabs do.“

But when I think of what tabs do, they lift. I think of lifting the stern rather than bow down. So if you are listing to port you need to lift the port side, then port tab down which in my world, should be the port button. I suppose the “normal” way is all about down. Bow down, starboard side down, port side down While I’m thinking of lift/up. I’ve had the boat for awhile now but if I’m not thinking I still use the port button to operate the port tab and wonder why the list is getting worse. Maybe my brain is wired differently. I could always swap the connections I suppose.
 
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wireline

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All you guys are very helpful ! I have been boating for many years , never had trim tabs until we bought our Voyager. Yes sure was a tricky thing to learn. I received advice like you guys are putting up here and still working on best ways to use them. So it does not matter how long were on the water, we can always learn more.
Thanks & have a great Holiday
 

seasick

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The interaction of different hulls, motors and tabs can be complex. On My Other Boat the biggest mistake I can make and did at first was to deploy too much tab. When in that situation the hull would all of a sudden steer to that direction aggressively and create a severe list. I was barely able to steer out of the turning.
The second aspect I learned after many mistakes is that you have to be patient. Holding the tab switch for less that 3 seconds doesn't really work well. My tabs do not have indicators so I have learned to feel and listen to the water swooshing by. I also learned that when I make a tab change, I have to wait 3 to 6 seconds for the changes to take effect. In the early days of learning, I would trim, not see what I wanted and trim again without letting the hull completely adjust.
The response times I assume vary a lot depending on hull weight, tab size and sea conditions.
One final fact for that hull is that the optimal trim settings are related to tab settings and visa versa. It just takes time to learn and to listen to the boat.
 

magicalbill

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Thanks for all the helpful information here....

So, I feel like I have figured out the trim tabs on the everyday chop in my bay. However, I went out in some 20-30mph sustained winds one day and wasn’t really sure if I should slow down, stay on plane, raise the bow, etc.

When the waves are closer together, I’m good as I feel like the boat never drops off and can glide from one wave to the next. The boat feels like it is always on 2 waves at a time. On that one day, there were 3ft waves close together but every once in a while there would be a gap long enough that made me indecisive and it felt like I would ride down the wave before the next one would hit the hull. I found myself slowing down to raise the bow but then I got off plane.

What’s the thoughts on the tabs in relation to choppier waters? Do you still want to have the bow cut the waves or take further back? Where do you draw the line from cutting the waves vs stuffing the bow?

I am planning on heading out my inlet and into the ocean for the striper runs this fall but still unsure of how best to use the tabs in more adverse/ different wave conditions/ style.

Hi amamola:

RE: Tabs In Relation To Choppier Waters:

Once it gets too rough for a 22 footer offshore, tabs won't help.. In following seas they can hurt.

That said, in a head or quartering sea when it's really rough and assuming your still in safe conditions, keep the bow down until you feel like the possibility of stuffing it presents itself. If you head into a wave and the spray arcs off the port & starboard quarters, that's fine, as long as it's not on the verge of coming over the bow. Common sense is big here.

RE: Where Do You Draw The Line Between Cutting The Waves And Stuffing The Bow?

If your underway and your significantly climbing head seas and dropping into the troughs, or valleys between waves, that's the time to tab up and head back. Once your Seafarer starts climbing the seas instead of slicing thru them, that's when you draw your line.

If you choose to stay out, whether it's a head or following sea, the bow must climb the wave in front of it and having the tabs deployed down will hinder that, especially in following seas. Captain's Judgement is critical at this point. If you tab up and are going over wave after wave and it feels okay, then, fine. If you start taking excessive spray and your not in danger, but starting to feel weird about it, go in. It's a 22 ft boat in the Ocean. Take no chances. There's always another day. Remember, if it feels like it's too rough to you, it probably is.

As glacierbaze said, don't be timid when the seas are on your stern as your going back in. This section isn't Tab-Related, but discusses handling concepts to consider while offshore. When your no longer wavetop-to-wavetop, your dropping into the troughs, as mentioned. If you hesitate, or the bow runs into the wave in front of you, the effect in either case is the boat slows down. Then, the wave behind you could overtake the boat, lift the stern and possibly flip you sideways and forward as the bow is wedged in the front wave. This is celled "Pitch Poling" and the results are never good. This is an extreme case, but not beyond the realm of possibility in rough conditions, or in an inlet with an outgoing tide. Keep the boat moving steadily, don't fly off the face of the wave in front of you into Outer Space, but don't let the wave on your stern catch you.

if you watch the "Haulover Inlet" videos on YouTube you can witness equal amounts of Expert Handling and Idiocy all in one clip. They shoot the footage from the South Breakwater during outgoing tides and incoming seas. What To Do and What Not To Do is on display in HD Quality.

LuckyDude and I have talked about these concepts relating to long-period Pacific groundswell, which is not what your boating conditions are, from what you tell me. If you are in long-period swell, sprung from a distant storm, you have much more operational latitude regarding what the boat will do because of wider intervals. He can operate differently, because of different circumstances.

I had a Seafarer for 10 years. 2 footers was my limit in a wind driven sea. The boat wasn't unsafe, but it wasn't fun, and I don't fish. When my fun stops, I'm outta there.

What I said above are my best recommendations and I will close with a neat quote I've always believed.

"The Best Display Of Seamanship Is To Avoid Getting Into Situations Where You Have To Use it."
 
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Doc Stressor

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That's why it's impossible to give a general recommendation about the use of tabs. Every hull is different. You have to mess around with your own boat under different conditions in order to learn how to trim the boat correctly. Trim gauges are notoriously inaccurate. You need to learn what the bars or %trim mean on your own boat.

But the recommendation not to use tabs with a following sea, particularly when running an inlet, cannot be overemphasized. A little tab may seem to help until you hit a wave wrong and bury the bow.

The SV2 hull is quirky. Not as bad as a Fountain or other step hulled gofast boats. But it takes a while to figure out how to them right. The older Grady hulls were much more forgiving though they don't ride as well.
 

magicalbill

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The interaction of different hulls, motors and tabs can be complex. On My Other Boat the biggest mistake I can make and did at first was to deploy too much tab. When in that situation the hull would all of a sudden steer to that direction aggressively and create a severe list. I was barely able to steer out of the turning.
The second aspect I learned after many mistakes is that you have to be patient. Holding the tab switch for less that 3 seconds doesn't really work well. My tabs do not have indicators so I have learned to feel and listen to the water swooshing by. I also learned that when I make a tab change, I have to wait 3 to 6 seconds for the changes to take effect. In the early days of learning, I would trim, not see what I wanted and trim again without letting the hull completely adjust.
The response times I assume vary a lot depending on hull weight, tab size and sea conditions.
One final fact for that hull is that the optimal trim settings are related to tab settings and visa versa. It just takes time to learn and to listen to the boat.

The things that Seasick mentions are all relevant, and are best perfected on calm waters before heading offshore where you should already have a grasp on them.

That's why I stressed learning the ropes inshore rather than poking out the inlet, encountering 3-4 footers and pressing toggles in panic mode, having no idea what they will do, and in some cases, regretting the result.

Start At The Beginning! Like so many Things Boating, it's a learning process.
 

magicalbill

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That's why it's impossible to give a general recommendation about the use of tabs. Every hull is different. You have to mess around with your own boat under different conditions in order to learn how to trim the boat correctly. Trim gauges are notoriously inaccurate. You need to learn what the bars or %trim mean on your own boat.

But the recommendation not to use tabs with a following sea, particularly when running an inlet, cannot be overemphasized. A little tab may seem to help until you hit a wave wrong and bury the bow.

The SV2 hull is quirky. Not as bad as a Fountain or other step hulled gofast boats. But it takes a while to figure out how to them right. The older Grady hulls were much more forgiving though they don't ride as well.

Ladies & Gentlemen, The Doctor Is In The House...

Always good advice from Doc Stressor....
 

glacierbaze

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Seasick, I've never had the kind of delayed reaction you describe for tabs. I've had hydraulic Bennetts, from 12 t0 18 inches wide, on all my boats for decades. Never had an indicator. If I'm on plane, and I press a tab for one second, the effect is immediate. 3 seconds would be a dramatic change, full range is probably 5 seconds.