Best Motor(s) Angle(s) & Trim Tab Settings for Heavy Sea

[Dory Denny]

I just purchased a C-Dory 25 with twin 90s. Would someone please advise on me the "Best Motor(s) Angle(s) & Trim Tab Settings for Heavy Seas." Thanks in advance!

Sincerely, Gerry

 

[NORO LIM]

I don't think you'll find any one setting. First of all, are those heavy seas coming or going? You definitely will not want the same setting when you are running with waves and when you are running across or against them. I'll let those with the same boat as yours advise you on what may work in various conditions. But as a general observation, I think static balance is important before you start messing with dynamic trim, especially in heavy seas. That is, distribute load in the boat at rest to the extent you can so that you don't have to do more than necessary with tabs or engine trim to get the up or down bow attitude you're after. Heavy seas means slower speeds. Slower speeds means less trim tab or engine trim effect.

 

[jennykatz]

We find running a 23 venture (cape cruiser) that we use some tabs and engine down going into a headsea to get the bow down to handle the oncoming waves . Going into an inlet or a following sea I usually have tabs neutral and eng up a little to ride over the waves This is a lot of trial and error with tabs and eng trim.

 

[matt_unique]

I just purchased a C-Dory 25 with twin 90s. Would someone please advise on me the "Best Motor(s) Angle(s) & Trim Tab Settings for Heavy Seas." Thanks in advance!

Sincerely, Gerry

Engines trimmed all the way up and out of the water safely at the marina until the heavy weather subsides

Beware of get home itus. (We've all danced with that devil).

I'm sure you're looking for something specific from the C-25 owners but it will boil down to keeping your bow up, ideally approaching head seas at an angle to avoid a head on slam, and keeping your hand on the throttle to minimize jumping off the top of waves or surfing down the backside and broaching.

It may also help to have you describe what you mean by heavy seas. That is very relative of course.

Welcome to the club by the way.

 

[Dory Denny]

Thank you for your insightful responses! Also, thanks for the welcome Capt. Matt

"Heavy seas," for me, would be 4ft waves or greater and not rollers; 4ft probably wouldn't seem like much for many of you.

NORO LIM and jennykatz made a lot of sense when they suggested no one setting and depends on whether running against or with...

Also, Matt's point about avoiding jumping off the top of waves by angle and throttle makes alot of sense.

Questions:
(1) Still not sure whether bow should be down or up?
(2) Should large waves ever be taken head on?

Gerry

 

[Dory Denny]

NORO LIM,

Thanks also for you recommendation to adjust static balance (load distribution) before tabs and engine trim. Questions: (1) What is best weight distribution? Even? More distributed in bow (v-berth)? (2) Also, would you please elaborate on, "Slower speeds means less trim tab or engine trim effect." Thank you for explaining. I am very new to this.

Sincerely, Gerry

 

[starcrafttom]

Hi, I got her late but I will give it a shot. What ever feels good. :wink: No really its about how the boat feels in the conditions your in. Its just not as simple as a set angle or amount of trim on the tabs. Its a seat of your pants thing. You have to be able to feel and anticipate how the boat is handling.

I constantly adjust the trip with accordance to the wave height, power, direction, spacing and load. My boat need a vastly different trim angle going into the waves with a full gas and water tank than with a full water but empty fuel tank.

my point that you have to know what these different factors will do to the handling of your boat and what trim and tab will do to your boat. Hey the are both just buttons- press them and press them often.

My great aunt did not like to drive at night. Not because she could not see or was a bad driver, but because she did not want to wear out the head lights????

 

[NORO LIM]

NORO LIM,

Thanks also for you recommendation to adjust static balance (load distribution) before tabs and engine trim. Questions: (1) What is best weight distribution? Even? More distributed in bow (v-berth)? (2) Also, would you please elaborate on, "Slower speeds means less trim tab or engine trim effect." Thank you for explaining. I am very new to this.

Sincerely, Gerry

Gerry,

As Tom and others have pointed out, "correct" is a relative term. If I am anticipating heading into significant chop, and I have a boat heavy in the stern with fuel and a cockpit full of stuff for a month-long cruise, I will move things into the V-berth to help hold the bow down. I actually pack for long trips with this in mind. I have a couple of large duffel bags full of gear that I throw around as conditions and loading dictate. I also move my little generator forward and aft. When I've got the weight where I want it (generally more forward under these conditions), then I adjust the engine angle a little at a time until I reach the right combination of comfort and efficiency. Sometimes, making the ride a lot more comfortable also makes it a lot more expensive - what you choose depends on whether you want to bounce on a full wallet, or glide on an empty one.

Riding with the waves, you definitely want the weight back and the bow up. You'll just have to experiment a little to find the right speed and angle settings for the conditions. As others have noted, you really, really, really, do not want to be going at any speed with you're engines trimmed way up (i.e., bow down) in following seas. Broaching is a serious threat for the unwary. These boats are great in following seas if you don't counteract their innate characteristics by burying the bow in one wave while another one is trying to pick you up from astern.

I try to keep level across the beam at all times and switch fuel tanks regularly. I have even been known to speak brusquely to the First Mate about staying in the First Mate's seat when the water gets all up and down.

Incidentally, I have twin engines with Permatrim foils, but I have no trim tabs, so all mechanical (i.e., non-load distributing) adjustments to pitch and roll are done with engine angle. Just remember, however effective your trim tabs and engine angle adjustments are at controlling your boat at 20 MPH, they will do next to nothing for you at very slow speeds. If your boat is sitting at the dock with the bow down and tilted badly to one side, your trim tabs and engine angle adjustment have no effect at all. You have to be moving before tabs and props do anything. The faster you move, the greater the effect. In fact, at WOT ("Wide Open Throttle"), sudden adjustments can be downright dangerous. So, if you are unbalanced at the dock, but you can "correct" the balance at 20 MPH with trim tabs, what happens if conditions require you to slow down to 5MPH? You're unbalanced again, just when you don't want to be. Loading matters.

And 4-footers are nothing to sneeze at. If steep enough and close enough together, they can be serious business. 8-foot rollers can be a barrel of fun. 4-foot "confused seas" can be Hell.

Enjoy your boat!

Bill

 

[JamesTXSD]

As everyone is telling you... it depends. As a generality, I have the trim tabs up and motor neutral (perpendicular to the water) in following seas. Going into the seas depends on how big AND close the waves are. If the waves are close together and steep, I will probably be running at displacement speed (6 - 7 knots) and trying not to pound. In that case, the trim tabs are less effective at slow speeds, so they'll probably be up again; motor trim to keep the bow where it is the most comfortable ride. I am NEVER in such a hurry that I am willing to let the boat pound... uncomfortable for the ride and rough on the equipment. If the waves are widely spaced, push the throttle forward to whatever speed works, adjust trim tabs and motor trim for best ride, most efficient fuel burn. If the waves are small chop (2 feet or <), I will generally trim for a bow down ride, so the boat doesn't pound, and throttle set to best fuel burn for the conditions.

It really comes down to what the conditions are and what speed you want to run. At planing speeds, we are generally trimming the bow down (our 25 tends to ride bow high above displacement speed), motor again usually perpendicular to the water, and trim tabs for level running. There really is no: this always works settings that I've found.

Run the boat, try different settings, see what gives you the most comfortable ride and most efficient fuel burn for the conditions.

Enjoy the boat!

Best wishes,
Jim B.

 

[matt_unique]

Thank you for your insightful responses! Also, thanks for the welcome Capt. Matt

"Heavy seas," for me, would be 4ft waves or greater and not rollers; 4ft probably wouldn't seem like much for many of you.

NORO LIM and jennykatz made a lot of sense when they suggested no one setting and depends on whether running against or with...

Also, Matt's point about avoiding jumping off the top of waves by angle and throttle makes alot of sense.

Questions:
(1) Still not sure whether bow should be down or up?
(2) Should large waves ever be taken head on?

Gerry

Hi Gerry,
You want to control your boat such that you don't take water over the side - any side - whether it's the bow, stern, or sides. It's prudent to balance the weight on your boat under any circumstances.

If heading into seas you would want to have your bow trimmed up sufficiently to avoid taking water over the bow. I would have tabs all the way up and engine trimmed up to get the bow high enough for the waves. Your speed would depend on a lot of factors but most importantly the steepness of the wave. If steep you need to go slow - just fast enough to maintain directional control. Taking a wave dead on straight will result in the most violent movement for you and the vessel. It's better to turn away a bit from the head on wave so you hit it at an angle. For example if heading straight into a wave and you turn a little bit to the right your front left goes up the wave first, then the middle of the vessel, and finally the rear right portion of the boat goes over. Does this make sense? This is a better way to disperse the energy. Turning a little to the left would make the front right go over the wave first, then the middle, then the rear left.

The maneuver above may not support where it is you are trying to go (temporarily) but it's important to absorb the waves energy without causing danger then get back on course. I would hesitate to say never on a boat - if at all possible - don't take a large wave head on.

 

[Dory Denny]

Hi Starcrafttom, I have "felt" the differences, e.g., changes in smoothness, handling that resulted from changes in trim tabs and eng angle.

I also felt the tremendous impact/slamming of the whole boat after jumping off the third wave of a series (wake from cargo ship. Hope I didn't damge the boat that did a big bellyflop. I believe this is what "jennykatz" warns about in above message.

I will follow your advice to try the buttons often. Love the part about your great aunt..."she didn't want to wear out the headlights." Great lesson!

 

[Dory Denny]

Matt, Thanks for the great advice/explanation. I especially like making not taking on water a priority. The second of my three times ever, on my new/used boat, something must have been wrong with the combination of tab, eng angle, weight balance, speed, etc...water was rooster-tailing up into the cockpit and covering the top of my port-side engine.

 

[Dory Denny]

Thanks, Jim.

I am very grateful to you, and the others who have commented, for your EXCELLENT advice!

Can't wait to get back on the water to put some what I've learned into practice.

Sincerely,
Gerry

 

[Dory Denny]

Hi Bill,

Thank you for your VERY valuable perspective!

I intend to save and print your message, as well as all of the others, so that my wife and sons can read them...and also to have them available for review on board.

Sincerely,
Gerry

 

[thataway]

In the rare occasion that we had 4 foot chop--and that is very significant--we found a larger boat going the same way, and fell in right off his stern!

We had a single 130, and both trim tabs and a Permatrim. We did not move any luggage around, but did put the bow down into seas. Bow up too much will cause the boat to pound. Of course you have to slow way down going into heavy seas.

Going down wind/wave, the bow is trimmed up--and stay on the backs of the seas. Do not overtake the seas--you run the risk of bow steering and broaching.

 

[hardee]

Thank you for your insightful responses! Also, thanks for the welcome Capt. Matt

"Heavy seas," for me, would be 4ft waves or greater and not rollers; 4ft probably wouldn't seem like much for many of you.

NORO LIM and jennykatz made a lot of sense when they suggested no one setting and depends on whether running against or with...

Also, Matt's point about avoiding jumping off the top of waves by angle and throttle makes alot of sense.

Questions:
(1) Still not sure whether bow should be down or up?
(2) Should large waves ever be taken head on?

Gerry

Hi Gerry,
You want to control your boat such that you don't take water over the side - any side - whether it's the bow, stern, or sides. It's prudent to balance the weight on your boat under any circumstances.

If heading into seas you would want to have your bow trimmed up sufficiently to avoid taking water over the bow. I would have tabs all the way up and engine trimmed up to get the bow high enough for the waves. Your speed would depend on a lot of factors but most importantly the steepness of the wave. If steep you need to go slow - just fast enough to maintain directional control. Taking a wave dead on straight will result in the most violent movement for you and the vessel. It's better to turn away a bit from the head on wave so you hit it at an angle. For example if heading straight into a wave and you turn a little bit to the right your front left goes up the wave first, then the middle of the vessel, and finally the rear right portion of the boat goes over. Does this make sense? This is a better way to disperse the energy. Turning a little to the left would make the front right go over the wave first, then the middle, then the rear left.

The maneuver above may not support where it is you are trying to go (temporarily) but it's important to absorb the waves energy without causing danger then get back on course. I would hesitate to say never on a boat - if at all possible - don't take a large wave head on.

I think this is what is called the "Jog and Slog". It takes time, probably not direct to where you want to go, but much easier on you and the boat, gear and the passengers, and safer than running in the trough in big beam seas. Might be a good time to rethink --> do I really need to be here NOW?

Harvey
SleepyC :moon

 

[hardee]

Matt, Thanks for the great advice/explanation. I especially like making not taking on water a priority. The second of my three times ever, on my new/used boat, something must have been wrong with the combination of tab, eng angle, weight balance, speed, etc...water was rooster-tailing up into the cockpit and covering the top of my port-side engine.

"....water rooster tailing up into the cockpit..."

Sounds like something is dragging, Hummm---fenders still out? or a single tab way down. Sounds more like a fender. A rooster tail would come up behind anything moving in the water. I would think of a midship fender. Maybe you already did?

Harvey
SleepyC :moon