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Old 05-23-2019, 12:56 PM   #1
witchboat
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Default Trim up or Trim down

When piloting may boat in heavy chop or whitecaps
I will usually trim up and slow down and keep the bow high.
I recently went for a test drive and the pilot kept the trim down and pushed thru the waves it seemed to ride smooth
This had me questioning my methods and thought I would ask the Forum what they do.
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Old 05-23-2019, 01:00 PM   #2
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Trim down and plow through waves. Trim up to do top speed runs or to save fuel when on plane and conditions are smooth.


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Old 05-23-2019, 01:03 PM   #3
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Depends so much on speed, size of waves / wakes, type of boat, on plane or off plane, etc...?
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Old 05-23-2019, 01:06 PM   #4
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In heavy chop...”trim down, slow down”

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Old 05-23-2019, 01:07 PM   #5
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Quote:
Originally Posted by witchboat View Post
When piloting may boat in heavy chop or whitecaps
I will usually trim up and slow down and keep the bow high.
I recently went for a test drive and the pilot kept the trim down and pushed thru the waves it seemed to ride smooth
This had me questioning my methods and thought I would ask the Forum what they do.
Trim down and keep as much of the "V Hull" in the water as possible to cut the chop and give you a smoother ride, but be careful you do not want to snuff the bow. The less bow in the water the more banging you will have.
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Old 05-23-2019, 01:33 PM   #6
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Depends a lot on the size/style of the boat and some on wind direction relative to course. If you're quartering you might want to trim one side up a little to minimize spray. The naval architect who designed the boat thinks it runs well at a certain speed without trim tabs, and tabs are used to adjust for variations in load (weight & balance). For whatever reasons, I see more GFBL's go by trimmed bow up which makes them spank or slap. I agree with Ishoot308 that generally as it gets rougher, bow up, slow down. With more sophisticated electronics, you can see variations in speed and fuel flow when you tickle the tabs.
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Old 05-23-2019, 01:39 PM   #7
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I agree with Ishoot308 that generally as it gets rougher, bow up, slow down.
Nope...just the opposite..."Bow Down (trim down), Slow Down". There is no sense exposing the bottom hull of your boat to oncoming smashing waves. With the bow down you hull is doing what it was designed to do...displace the oncoming waves with the V nose of the hull... Unless of course your in a pontoon boat then things are totally different!

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Old 05-23-2019, 01:41 PM   #8
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Witchboat --

Think of it this way -- when you trim up, your bow rises and thus you "slap" the waves more making for an uncomfortable BANG, BANG, BANGING ride.


Put the trim down and you have a greater likelihood to "Cut Through" the waves making for a smoother ride.


The larger/heavier the boat the better this system works --- if you have a pontoon boat -- then simply head home cuz none of this will help.
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Old 05-23-2019, 03:52 PM   #9
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Originally Posted by ishoot308 View Post
Nope...just the opposite..."Bow Down (trim down), Slow Down". There is no sense exposing the bottom hull of your boat to oncoming smashing waves. With the bow down you hull is doing what it was designed to do...displace the oncoming waves with the V nose of the hull... Unless of course your in a pontoon boat then things are totally different!

Dan
Yeah. I hear what you're saying. There is a fine line here. Depends on the wave heights, I guess. I rarely go much above planing speed (24' Sea Ray, 2800 rpm) so If I slow down and come off plane because it is rough, the tabs don't do anything anyway. But, if I let the bow up just a little, there is considerably less banging. If slow down means drop from 4000 rpm to 3500, I was never there in the first place. One of the best riding boats I ever had was a 26' Lyman, deep forefoot, cut the waves as you suggest, no trim tabs.
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Old 05-23-2019, 05:01 PM   #10
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Default Trims

There are two types of adjustable trims. drive trims and transom trims. All boats except inboards have drive trims. Performance boats and some inboards have transom trims.

Drive trims are used to provide the 'attitude' of the bow. When the drive is down the bow is down, drive up, bow up.

Transom trims are use mainly to help level the boat from port to starboard or vice versa. On ski boats, with the trim down, there is less wake, trim up there is more.

On performance boats the throttle man usually use the transom trims to adjust the stern attitude along with the drive trims adjustment to provide a nice 'tude at speed and chops.

Technically on a semi V or flat bottom boat, you would want the bow down (trim down) in choppy weather to 'plow thru the waves. At speed you will trim up until the rpm rises, tap back down. At times a boat will porpoise or chine walk before rpm increases, tap it back down.

Deep Vs especially heavy ones you would want the trim horizontal to the hull in chops. You would want to ride through the waves than plow into them.

One of the most memorable experience using trims is the dancing from one swell to the next at the Cigarette Top Gun School in Aventura FL!
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Old 05-23-2019, 06:58 PM   #11
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Quote:
Originally Posted by ishoot308 View Post
Nope...just the opposite..."Bow Down (trim down), Slow Down". There is no sense exposing the bottom hull of your boat to oncoming smashing waves. With the bow down you hull is doing what it was designed to do...displace the oncoming waves with the V nose of the hull... Unless of course your in a pontoon boat then things are totally different!

Dan
Yup...coming under the Gov Is bridge yesterday into what must have been 15-20 knot winds, the rollers were blowing in from Meredith. Iím my tritoon I trim up to bring the bow(s) up and maintain 10 mph for a smooth ride with no splash.
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Old 05-23-2019, 07:09 PM   #12
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Yup...coming under the Gov Is bridge yesterday into what must have been 15-20 knot winds, the rollers were blowing in from Meredith. I’m my tritoon I trim up to bring the bow(s) up and maintain 10 mph for a smooth ride with no splash.
Exactly! I also move passengers to the stern on my Tritoon when it’s rough...
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Old 05-23-2019, 07:14 PM   #13
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IMHO it all depends on how your boat is handling the water you are in at the time. There are a lot of variables to take into consideration. Wind and current, size of boat, weight of boat, hull design, and the direction you are going in all play a role. My rule of thumb is if you can trim down and get up on plane and get up and over the chop without beating yourself, (and the boat!) up, then do it. If it's just to rough and the boat is taking a beating and/or water is coming over the bow, then I slow down, trim up, (get the bow up in the air), and "plow" through it. People's "opinions" vary, (needless to say). One guy's way of getting up on plane and flying over the chop while the boat takes a pounding may be his way of doing things, while another guy would never do that to his boat. Money always plays a factor too. If money is no object, then you can "beat" on the boat all you want, where other's will treat it like a baby and try to be conserveative. All kinds of "factors" that play into people's behavior, and how they "run" their boats.

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Old 05-23-2019, 08:23 PM   #14
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Exactly! I also move passengers to the stern on my Tritoon when itís rough...
Yes! Unless they want a cool shower...
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Old 05-23-2019, 10:07 PM   #15
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Quote:
Originally Posted by BroadHopper View Post
There are two types of adjustable trims. drive trims and transom trims. All boats except inboards have drive trims. Performance boats and some inboards have transom trims.

Drive trims are used to provide the 'attitude' of the bow. When the drive is down the bow is down, drive up, bow up.

Transom trims are use mainly to help level the boat from port to starboard or vice versa. On ski boats, with the trim down, there is less wake, trim up there is more.

On performance boats the throttle man usually use the transom trims to adjust the stern attitude along with the drive trims adjustment to provide a nice 'tude at speed and chops.

Technically on a semi V or flat bottom boat, you would want the bow down (trim down) in choppy weather to 'plow thru the waves. At speed you will trim up until the rpm rises, tap back down. At times a boat will porpoise or chine walk before rpm increases, tap it back down.

Deep Vs especially heavy ones you would want the trim horizontal to the hull in chops. You would want to ride through the waves than plow into them.

One of the most memorable experience using trims is the dancing from one swell to the next at the Cigarette Top Gun School in Aventura FL!
Good post. Thank you.
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Old 05-28-2019, 05:41 PM   #16
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Yes! Unless they want a cool shower...
Yeah, on a 'toon the math is;
trim down + big waves = everyone's going home to change clothes.
trim down + low speed + trough = someone is buying new front panels (Hint: Bennington charges ~$360 for the front port panel, ask me how I know)
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