Re: Any advice on new trim tab setup?
Vicman;
For all of you who have not received prompt response to your email I must apologize. Our server was 'hacked' and we were receiving 4000 plus emails (junk) every few days. I think it is better now.
Addressing the issue of listing - Tabs or no Tabs.
Except for load imbalance "listing to port" is nearly always a result of prop torque and/or resistance. The prop rotates clockwise which causes the boat to try rotating counter-clockwise.
When the bottom of the boat is completely flat (which it never is these days) the hull resists the list.
When the hull is 'V' shaped the list is likely to show up. However, when the 'V' bottom boat is underway (cruising) the water pressure on the hull is usually enough to resist the prop torque and keep the boat level.
When a list occurs at cruising speed, what is the cause? To answer this question we need to make some assumptions, such as:
The prop is a standard three blade.
There are no other planing devices on the boat (ie: Hydrofoils)
Load is even.
Under the above criteria, the answer would likely be that the "motor trim" is too far down (close to the transom). With the motor trim down the prop is pushing the boat UP on the stern and down on the bow. The front or bow end of the boat is where the hull has the most severe 'V' and has less ability to resist the torque of the prop. Trimming out usually helps minimize the list if not remove it entirely. Excessive stern lift is not good!
Notice that lifting the stern and pushing the bow down increases the sensitivity for a list.
What else lifts the stern? Hydrofoils, Trim Tabs, and some props.
Hydrofoils by their design, lift the stern and do so more and more as the boat increases in speed, so that the boat runs bow down on the sharper portion of the 'V' hull.
Some props are designed to create lift, but these are usually specialty props.
However, cupped, four,and five bladed props have increased resistance and make it harder for the hull to resist the listing.
Smart Tabs (Trim Tabs) can cause cause a list when:
A) they are set with too much lift (adjustment issue)
B) when the Actuator is too strong for the application (exchange actuators)
C) when the motor is not trimmed out to vertical.
PLEASE NOTE: If the boat does NOT list without the trim tabs (or the other devices) then the list is being caused by excessive lift from the tabs (or the other devices), AND ADJUSTING THE TABS STRONGER ON ONE SIDE (PORT) THAN THE OTHER IS NOT LIKELY TO CORRECT THE PROBLEM WITHOUT CAUSING ANOTHER HANDLING PROBLEM.
The solution is to reduce the lift (adjustment) or exchange the actuators if necessary.
IN SUMMARY: A list to port is most often caused by lifting the stern and driving the bow down when at cruising speeds. Hydrofoils, aggressive props, and any stationary lifting device, can cause the boat to be prone to a list. Smart Tabs can also cause a list when adjusted too strong or when the actuator is too strong.
As A Side Note: Most boat operators are reluctant to trim the motor out because the boat may porpoise, but when the Smart Tabs are installed, they will control the porpoising.
