Yet more trim tab questions

B

BillE

New member
Yes or No:

1. Fully retracted trim tabs are the same or very close to having no trim tabs at all?

2. The only effect of trim tabs is to add lift to the stern, which in turn lowers the bow? And that raising the bow---pressing Bow UP--- is simply removing the tabs effect? OR, do tabs also actively raise the bow?
 
BillE,
1. yes

2. nah, the engine trim alone would do that. The main use of trim tabs on trailer boats is to correct the port/std lean at cruise that occurs when Fatso moves from one side of the boat to the other, or when heavier stuff is on one side.

Start your learning with tabs full up (no effect) and with experience you'll appreciate the side to side corrections the 2 tabs can help with when a center engine can not. IE, you will use the TWO tab switches quite independently to correct sideways lean mainly, and engine trim for forward/aft trim for best planing attitude in various conditions. Some will dicker.

Offer a Sea Tow or other captain $100 cash for an hour or two of his best tips (an official Power Boat Instructor costs more) and it may be the best 10% of a boat unit you'll spend, is my bet. Don't worry so much, if you set everything wrong the worst you get is a big wake, bad gas mileage and other boaters throwing their empty beer cans at you.
Have Fun!
John
I
 
The boats run best with both trim tabs and a foil: (Permatrim) which will increase the effect of trim of the motor.

The trim tabs are also used with bow up and bow down attitude. As john says, experiment--get the boat at one level plane, then slowly experiment with the tabs and engine trim. Basically the most efficient will be when the RPM does not increase any more for with minor adjustments for the trim tabs and engine trim.

Also going into chop, you want bow down--and both trim tabs will help with this, as well as the engine trim. But going down waves and seas, you want the bow up more--and do want to avoid "Bow steer" and a potential broach.

If the boat has a fuel flow meter, it also will help to get the best speed, and MPG as you work the trim tabs and engine trim.
 
BillE":37ieow1t said:
Yes or No:

1. Fully retracted trim tabs are the same or very close to having no trim tabs at all?

2. The only effect of trim tabs is to add lift to the stern, which in turn lowers the bow? And that raising the bow---pressing Bow UP--- is simply removing the tabs effect? OR, do tabs also actively raise the bow?
Click to expand...

It really depends on what the actual position of the tabs are when they are "UP".

Depending how they are installed, the UP position may actually have the tab at a down angle.

On my boat UP is only slightly above "flat", so my tabs are likely doing something even when fully up. If nothing else, they may be adding some lift to the back of the boat.
 
Yes or No:

1. Fully retracted trim tabs are the same or very close to having no trim tabs at all?

2. The only effect of trim tabs is to add lift to the stern, which in turn lowers the bow? And that raising the bow---pressing Bow UP--- is simply removing the tabs effect? OR, do tabs also actively raise the bow?
Click to expand...

1. Yes

2. No. Trim tabs are for lateral control. Ie. the listing of your boat depending upon load.
 
In my experience with the CD25 the trim tabs have a big effect on the bow attitude, and are more effective for smoothing chop than motor trim alone.

Think of it this way: The motor trim forces the bow (along with most of the hull) down into the water and the trim tabs raise the stern allowing the bow to drop down into the water. I find the that using the motor trim to push the bow down causes more wallowing and bow steer while reducing speed and fuel economy considerably.

Using a hydrofoil such as the Permatrim increases the effects of motor trim significantly and acts somewhat as a third trim tab affecting stern lift. I had a Permatrim on my Honda 130 for several years and found that is helped me quite a bit. With the new Suzuki 200 I haven't seen the need for one.

What I have found over the years is that when cruising on plane, the best way to find the ideal trim tab position is to have the motor trim set so the prop shaft is parallel to the water surface and the tabs set so the boat is level side to side. Then adjust both tabs up or down until the greatest speed is obtained without changing the throttle position. The RPMs may go up slightly without moving the throttle when the ideal cruise attitude is reached, and at that point you should have the most efficient and economical ride. If the water is choppy and I need to bring the bow down to smooth it out I use the trim tabs to do so, sacrificing a little speed and fuel economy.

As everyone agrees, the effect of trim tabs is most appreciated for leveling the boat side to side and is least appreciated in following seas. But you can do a lot with them to help speed, comfort and economy.
 
The way my boat is typically loaded, I am usually running with the motor trim pretty much all the way in and then use the trim tabs to adjust the hull angle for the best ride in the current conditions.

The trim tabs are good for lateral trim. My boat is heaviest on the starboard side. The driver, batteries, and main storage space (under the sink and stove) are all on that side.
 
OK, thanks to all for the replies. So it does seem that the action of the tabs is to provide lift to the stern, whether to trim the bow or the side to side, and that was my question as to just what was going on.
The "dummy" switches Bow Up and Bow Down are handy for function but I would like to know where each tab is at any given time. I would like to know a "percentage of trim" or have some numerical or graphical reference, but I can work with starting with full retraction and adding trim as needed.
My 25 is equipped with Boat Leveler tabs, which I do not seem to hear much about but do seem to be working fine.
 
BillE":2tgxcuk4 said:
...The "dummy" switches Bow Up and Bow Down are handy for function but I would like to know where each tab is at any given time. I would like to know a "percentage of trim" or have some numerical or graphical reference,....
Click to expand...

You can get a tab position indicator for the Bennett trim tabs. It can either be just the position indicator or an indicator/switch combo.

For example: https://www.westmarine.com/buy/bennett- ... r--6885255
 
You can get a tab position indicator for the Bennett trim tabs.
Click to expand...
I have a similar indicator device on my CD25. Frankly, I can't imagine having trim tabs without it. It seems to me that without it one would need to "fool around" with the trim tab switches a lot to figure out if they were in the right position. I suppose port vs starboard trim would not be so hard to set without an indicator, but even level trim would be prone to setting wrong (that is, one could get beam trim done at many settings of the trim tabs, not just the minimal -- e.g., starboard at 0%, port at 20%, but starboard at 30% and port at 40 or 50% might *look* just the same in terms of being level)
 
smckean (Tosca)":140xrgui said:
You can get a tab position indicator for the Bennett trim tabs.
Click to expand...
I have a similar indicator device on my CD25. Frankly, I can't imagine having trim tabs without it. It seems to me that without it one would need to "fool around" with the trim tab switches a lot to figure out if they were in the right position. I suppose port vs starboard trim would not be so hard to set without an indicator, but even level trim would be prone to setting wrong (that is, one could get beam trim done at many settings of the trim tabs, not just the minimal -- e.g., starboard at 0%, port at 20%, but starboard at 30% and port at 40 or 50% might *look* just the same in terms of being level)
Click to expand...

I only use the indicator when I set the tab position when first setting out for a trip. After that the tabs are set by feel based on how the boat rides. I have disabled the auto stow feature so I don't have to reset the tabs each time I restart the engine. My boat sits on the trailer such that there is no interference with the tabs if I forget to retract them when retrieving the boat.
 
The good news is that "Boat Leveler" is still in business and you can get all of the parts. The BAD news is that the "insta-Trim" position gauge is available but costs somewhere about $330. I have had Boat Leveler Trim tabs on my 2003 C Dory 25, and they worked fine. I didn't feel it was worth the $$ for the trim gauges. My current boat has Benett, and the indicators--nice but not essential. After you have run the boat awhile, you have reflex knowledge of what needs to be done. If our boats are in at all choppy water, I have my hand on the throttle, and thus on the motor trim--and next move, is to move the trim tabs up and down, as needed. In the offshore racing boats, there is one person who is assigned as "throttle and trim" person, another steering and a 3rd navigator/engineer.

I believe that "insta-Trim" and "Boat Leveler" parts are the same.
 
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