Most boats are designed to plane at
a particular speed and weight distribution. However, as weight increases (due to
additional fuel, passengers, or gear) and/or speed decreases, the stern settles
down creating an inefficient, untrimmed condition. As the boat pushes forward,
it creates a "hill of water." In this bow-high position visibility is limited
and the hull bottom is pounded. In addition, due to significant hull drag and
extreme prop angle, fuel economy is poor. Properly sized Bennett Trim Tabs
enable your boat to overcome this "hill" and plane at speeds slower than
designed planing speed.
As the helm control is pressed, the stern rises, lowering the bow. Without touching the throttle, speed increases and optimum attitude is achieved regardless of speed or weight distribution.
Bennett Trim Tabs reposition the boat's bow to cut through the water reducing pounding, drag, and engine laboring. Repositioning the bow creates greater visibility which increases safety. Reduced pounding means greater comfort. Less drag and engine laboring translate into increased performance, greater speed, and reduced fuel consumption.
With all the advantages and efficiencies created, Bennett Trim Tabs virtually pay for themselves.
THE PRINCIPLE OF
BENNETT TRIM TABS
Bennett Trim Tabs are two independent, stainless steel, adjustable afterplanes attached to the bottom edge of the transom. As the helm control is pressed, the trim tabs move into position.
Water-force on the trim tab surface creates upward pressure, thereby raising the stern and lowering the bow. The principle is simple. The results are impressive.
Increase Speed • Reduce Pounding • Correct Listing • Eliminate Porpoising • Offset Prop Torque
Reduce Fuel Consumption • Reduce Engine Laboring • Eliminate Squatting
Improve Visibility • Reduce Wake • Improve Handling • Reduce Hull Stress
How to Use Trim Tabs
The key to obtaining optimal results from trim tabs is to operate them in short “bursts” and let the boat react before making another adjustment. The amount of time between corrections is influenced by the size of the trim tabs and the boat’s speed. This will help avoid overtrimming or ending up with one tab too far down when correcting lateral trim. You will quickly become acquainted with a boat’s particular traits.
Properly sized trim tabs can significantly reduce the time needed to get up on plane. They also allow a boat to keep its bow down and stay on plane at lower speeds. As the throttle is advanced the stern of the boat begins to squat, lifting the bow. As the boat accelerates, push the bow down position of the helm control in short bursts. The boat reacts by the stern lifting, the bow coming down, speed increasing, and reduced engine laboring. If you over do it and deflect the tabs too far the boat will end up overtrimmed. When over trimmed, the steering becomes “over sensitive” and wants to pull off course to port or starboard. If this occurs, operate the control “bow up" until the desired attitude is established.
CORRECTING A LISTING
As a result of uneven weight distribution, prop torque or wind, a boat runs with a list. Deep "V" hulls are particularly vulnerable to this condition. Running with a list is uncomfortable, as well as unsafe. Bennett Trim Tabs operate independently for effective list correction. To correct for list, lower the trim tab on the side of the boat that you are listing to. This will bring the boat level.
TRIM TABS AND
It is a common misconception that if a boat has power trim on the outboard or outdrive it does not need trim tabs. Power trim can be used to adjust the boat's attitude, but it is highly inefficient. A propeller is designed to force the boat forward. When trimming the boat with the prop, the prop must not only push the boat forward but raise the stern as well. In this situation, prop slippage is greatly increased thereby wasting R.P.M.'s. Power trim cannot correct listing, and is ineffective at slower speeds. Bennett Trim Tabs, in combination with power trim, enable both the hull and prop to be trimmed independently. The trim tabs trim the hull, while the power trim adjusts the prop. The result is optimum performance and efficiency not attainable by the use of power trim alone.
To acheive maximum performance, first adjust
the trim tabs to achieve the desired running attitude. Next, use the power trim
to position the propeller thrust parallel to the water flow. If necessary,
re-adjust the trim tabs to fine tune the attitude. By observing the boat’s speed
and engine RPMs the best combination of trim tabs and power trim will be
apparent. Trim tab angle indicators and a power trim angle indicator are
particularly useful in duplicating effective settings.
TRIMMING TO SEA CONDITIONS
When running into a head sea you want to trim the bow down so the sharp forward sections of the boat do their work cleaving the waves. This provides the most comfortable ride and minimizes stress on the boat (and passengers). In a following sea the tabs should be fully retracted for maximum steering response.
Operate the tabs in very short bursts of about half a second. Continue until porpoising subsides. The objective is to have only a very slight amount of tab deflection, just the amount needed to cure the up and down motion of the bow.