KEEPING IT ON THE LEVEL
THE COMPLETE GUIDE TO TRIM TABS AND INTERCEPTORS
Trim tabs are an essential component for many powerboats offering improved performance, comfort, efficiency and safety on the water. This comprehensive guide explores the purpose, functionality, benefits, and proper use of trim tab systems for powerboaters.
In the past, trim tabs were predominantly seen on cabin cruisers and sport fishers larger than 7 meters, generally called upon to assist with boat performance for vessels with top-heavy weight distribution and boats prone to windage. Nowadays, they are increasingly common on boats ranging from 5 to 6.5 meters. Trim tabs are now found on various types of boats, including open tiller steers, bowriders, ski boats, as well as cabin and hardtop models. Despite some beliefs that trim tabs are less crucial for smaller boats, the opposite is true. They significantly enhance the handling and comfort of smaller boats, compared to larger ones which are less sensitive to weight distribution.
A minor adjustment of the trim tab or interceptor can swiftly correct the fore and aft or lateral trim angles of a small boat, thereby improving its ride quality. Properly adjusted trim tabs or interceptors result in a smoother and more comfortable experience on the water. Over decades of use, it has been established that all boats, regardless of size, benefit from trim tabs or interceptors for similar reasons: enhancing planing efficiency, and to a degree improving fuel efficiency, while addressing issues of uneven weight distribution, enhancing speed, safety, and overall boat performance.
What are Trim tabs and how do they work?
Trim tabs are adjustable plates attached to the transom of a boat, just above where the hull meets the water. They are typically made of stainless steel or aluminium and are controlled by hydraulic or electric actuators. When deployed, trim tabs deflect water flow to alter the boat’s running attitude, allowing the operator to fine-tune the vessel’s performance in various conditions.
Trim tabs operate on a principle of “reverse psychology” in relation to water flow. When lowered, they create resistance against the water moving along the boat’s hull, effectively lifting that section of the stern. This action, in turn, lowers the bow on the opposite side.
By adjusting the trim tabs independently, a skipper can control both the fore-and-aft pitch and side-to-side roll of their vessel. A complete trim tab system typically includes:
- A pair of hinged metal plates attached to the transom
- Electric or hydraulic actuators to control the angle of the plates
- A hydraulic reservoir or control box
- A wiring harness for each tab
- A 12-volt switch at the helm for independent control of each tab
What are Interceptors and how do they work?
Interceptors on boats are specialised devices designed to improve the vessel’s stability and performance in varying sea conditions. They are typically mounted on the hull’s transom and can be adjusted to change the angle at which the hull meets the water. Like trim tabs, Interceptors help in controlling the trim (foreand-aft angle) and list (side-to-side angle) of the boat. By adjusting the interceptors, boat operators can optimise performance, fuel efficiency, and comfort for passengers.
Interceptors can be adjusted continuously and independently on each side of the hull. This allows for finer control over the boat’s behaviour in different sea conditions. Interceptors work by deploying downward into the water to create lift or reduce drag on the transom. This lift or reduction in drag helps to level the boat, improve planing efficiency, and reduce fuel consumption.
Like some trim tab systems, modern interceptors often come with automatic control systems that adjust the position of the interceptors based on the boat’s speed, sea state, and user preferences. This automation makes them userfriendly and ensures optimal performance without constant manual adjustment. They are particularly beneficial for larger boats where stability and comfort are critical.
Benefits of Trim systems
Trim tabs and interceptors both offer numerous advantages for powerboat owners in diverse marine environments. Properly adjusted they can significantly enhance a boat’s performance – reduced bow rise during acceleration, faster time to plane, increased top speed, improved fuel efficiency and better handling in various sea conditions.
Both trim tabs and interceptor technologies are now widely recognised as a safety feature, particularly in New Zealand’s sometimes challenging coastal waters allowing boats to run flatter and faster in bigger seas, thus reducing the risk of bow rise and potential “blowover” at high speeds. They can also assist in correcting “chine walking” in racing applications. By optimising the boat’s running attitude, trim tabs and interceptors can greatly improve onboard comfort offering a smoother ride in choppy conditions. They can reduce spray and water over the bow and minimise porpoising (bouncing) at higher speeds. Both systems allow boaties to adapt to changing conditions and loads compensating for uneven weight distribution, adjusting for varying passenger loads and optimising performance with different engine configurations.
When and how to use Trim tabs and Interceptor systems:
Understanding when and how to use Trim tabs / Interceptors is crucial for maximising their benefits:
Getting Underway:
Start with the Trim tabs / Interceptors fully retracted. As you accelerate, use short bursts of downward tab adjustment to reduce bow rise and get on the plane faster. Once on the plane, fine-tune the Trim tabs / Interceptors for optimal running attitude.
Trim tabs can also be utilised for a faster holeshot when getting underway. This is achieved by deploying both tabs/interceptors to create lift at the stern of the boat, allowing the boat to get “out of the hole” faster.
Cruising:
Adjust the system in small increments, allowing time for the boat to react between adjustments. Aim for a level running attitude, with the bow slightly up for best efficiency. Use Trim tabs / Interceptors in conjunction with engine trim for optimal performance.
Compensating for Weight Distribution:
To correct a list (lean to one side), lower the Trim tab / Interceptor on the side that’s riding low. For a bow-heavy condition, raise both Trim tabs / Interceptors equally to lift the stern. For a stern-heavy condition, lower or deploy both Trim tabs / Interceptors to allow the bow to drop slightly.
Handling Different Sea Conditions:
In a head sea, lower both Trim tabs / Interceptors slightly to keep the bow down and cut through waves. In a following sea, raise the Trim tabs / Interceptors to keep the bow up and prevent stuffing. In a beam sea, lower the windward Trim tabs / Interceptors to level the boat and improve comfort.
Trim tabs / Interceptors and Engine Trim:
It’s important to understand the relationship between Trim tabs / Interceptors and engine trim. Both Trim tabs and Interceptors primarily affect the hull’s attitude. Engine trim adjusts the propeller’s angle of attack. Used together, they allow for precise control of the boat’s running angle. For optimal performance, use Trim tabs / Interceptors to achieve the desired planing attitude. Adjust the engine trim to position the propeller path parallel to the water flow. Fine-tune with Trim tabs / Interceptors as needed.
Choosing the Right Trim tabs / Interceptors:
Selecting the appropriate Trim tabs / Interceptors for your boat depends on several factors:
• Boat length and beam
• Hull design (deep-V, semi-V, catamaran, etc.)
• Typical operating conditions
• Power and weight of the engine(s)
Consult with marine equipment specialists to determine the best size and type of Trim tabs / Interceptors for your specific vessel and needs.
Several types of Trim tabs / Interceptors are available for boat owners looking to improve their vessel’s performance and handling.
Construction types:
Stainless Steel Trim Tabs: These are the most common type, made from high-quality stainless steel plates strategically installed on the boat’s transom.
Composite Trim Tabs: Also known as “blades,” these are constructed from materials like fibreglass or carbon fibre, offering a lightweight alternative to stainless steel.
Controls and Mechanics:
Electric Trim Tabs: These are electric motors connected to the tabs that control their movement.
Hydraulic Trim Tabs: When the operator presses the control button, the hydraulic pump sends fluid to the actuators.
Spring Loaded-Self Levelling Trim Tabs: These are quick and easy to install with nothing to do inside the boat – particularly suitable for smaller boats.Trim tabs come in different mounting configurations and trim tab cylinder lengths to suit various boat designs – Standard Mount, Pocket Mount and Edge Mount. They are available in various sizes to accommodate different boat lengths, hull and transom designs and can be equipped with different control types, such as electronic indicator control, switch pad or simpler manual systems.
Interceptors:
Interceptor-style boat trim systems have gained popularity in recent years as an alternative to traditional trim tabs. Again these systems are designed to improve a boat’s performance, fuel efficiency, and overall ride quality. Several brands now produce interceptor systems, offering various sizes, shapes, and power options to suit different boat types and sizes in manual or automated options.
Interceptors come in different sizes to accommodate boats of various lengths from 6m to 30 m. Interceptors in some instances can be straight, V-shaped, chine-adapted, or designed for tunnel hulls.
POWER SYSTEMS
Electric: Many modern interceptor systems, use electric actuators for quick and precise control.
Hydraulic: Some systems, particularly those designed for larger vessels, may use hydraulic power for operation.
Pneumatic: Some systems use an independent air unit to control the interceptors.
Installation Considerations
While professional installation is recommended, some key points to consider include:
• Proper placement on the transom
• Ensuring watertight seals
• Correct wiring and/or hydraulic connections
• Appropriate mounting of control switches at the helm.
Maintenance and Care
To ensure the long-term reliability of your trim tab/interceptor system:
• Regularly inspect trim tab/interceptor and actuators for damage or corrosion.
• Check and clean electrical connections.
• For hydraulic systems, maintain proper fluid levels.
• In saltwater environments, use zinc anodes to prevent electrolysis
Safety Precautions
When using trim tabs/interceptors, keep these safety considerations in mind:
• Avoid over-trimming, especially at high speeds.
• Make gradual adjustments and allow the boat to respond.
• Be cautious when using significant tab trim tab/interceptor deflection in turns.
• Fully retract trim tabs/interceptors when running inlets or in following seas.
The Future of Trim Tab and Interceptor Technologies:
As boat design and technology continue to evolve, so too will these systems. Some emerging trends include automated trim systems that adjust based on speed and sea conditions, integration with digital control systems and displays, more efficient and durable actuator designs and the use of lightweight, corrosion-resistant materials.
Conclusion
When choosing trim tabs, it’s essential to consider factors like the size of your boat, the speed of your boat, the desired level of control and what kind of electronics you have on board, which will be compatible with new-age technologies available on these systems and lastly your budget. Whether you’re cruising the waterways, fishing off the coast, or competing in local powerboat races, mastering the use of Trim tabs and Interceptors will contribute to more enjoyable and efficient boating.
As with any aspect of boating, practice and experience will help you develop a feel for your boat’s optimal trim in various situations. Remember that Trim tabs and Interceptors are just one tool in the boatie’s arsenal. Used in conjunction with proper loading, engine trim, and good driving practices, they can significantly enhance your time on our beautiful waters. Always prioritise safety, be aware of your surroundings, and enjoy the improved performance and comfort a well-adjusted Trim tab or Interceptor system can provide.
Trim tabs and Interceptors are a valuable addition to many powerboats in New Zealand and Australia offering improved performance, safety, and comfort across a wide range of conditions.
By understanding how to properly use and maintain whatever your choice of system, you’ll enhance your on-water experience and get the most out of your boat.
There are quite a few brands available on the market to suit a variety of boat sizes and styles. Some of the examples of tabs and interceptors from leading brands on the market today include Bennett, Humphree, Hydrotab, Lectrotab, Lenco, Quick Intercepta, Dometic, SeaStar – Dometic, Ultraflex and Zipwake, available through various marine equipment retailers.
BENNETT TRIM TABS:
Bennett Marine is a well-known manufacturer of trim tab systems. Their trim tabs come in various sizes and configurations, including hydraulic and electric actuators. Bennett Marine also offers several trim tab accessories that will enhance the performance of your system. Their patented Auto Tab Retractor automatically retracts the trim tabs when the ignition is turned off. Trim Tab Indicators are now commonplace with most systems, but some are a little more sophisticated and precise than others. Bennett Marine offers three kinds of indication. One of them, the Electronic Indicator Control, includes the Auto Tab Retractor and connects easily to the Auto Tab Control. The only thing better than a performance-enhancing trim tab system is one that runs itself! Auto Tab Control (ATC) does exactly what it says it does – it automatically adjusts your trim tabs to changing conditions and maintains the optimum running attitude for your boat.
HUMPHREE INTERCEPTOR TRIM TABS:
Humphree Interceptor Tabs are advanced marine stabilization devices designed to enhance the performance and safety of vessels. These interceptors are mounted on the transom of the boat and use
fast-acting, vertically mounted plates to control the pitch and roll of the vessel. By adjusting the position of these plates, Humphree Interceptor Tabs can provide instant and precise trim adjustments, improving fuel efficiency, reducing drag, and ensuring a smoother ride even in rough waters.
One of the key advantages of Humphree Interceptor Tabs is their ability to automatically adjust in response to changing sea conditions and vessel dynamics. This automated functionality allows for optimal trim and stability without constant manual input from the operator. Additionally, these tabs are known for their reliability and low maintenance requirements, making them a preferred choice for both commercial and recreational marine applications. The advanced technology behind Humphree Interceptor Tabs includes a user-friendly interface and integration with existing onboard systems, allowing for seamless operation and monitoring. Whether for improving speed, reducing fuel consumption, or enhancing overall ride comfort.
HYDROTAB:
Hydrotab interceptor trim systems have been designed with simplicity in mind. By applying pressure to the hull, Hydrotab controls pitch and trim quickly and effectively. This creates a more effective lift directly under the hull rather than on a set of plates beyond the hull line. They are also more compact on the transom and protected from damage caused by beach launching or storing in a dry stack. There is something for every size of boat and every budget. The top-of-the-line control systems feature a glass bridge design and full automation of the entire trim system, complete with built-in gyro and GPS that manages both pitch and roll. Options include composite modular systems, Inox straight line and tunnel versions. Custom options are also available. The entry-level system comes with just four manual button controls and LED indicators, yet still gives the skipper complete control of both fore and aft and sideways trim.
lusty-blundell.co.nz
LECTROTAB:
Lectrotab uses an electromechanical trim tab system, with non-hydraulic actuators. The unit ensures very accurate tab positioning, provides maximum lift force, and is self-contained for easy installation. An internally designed friction brake prevents unwanted tab retraction when underway or backing down. The actuator assembly is packaged in a non-metallic permanently sealed housing. No components need to be installed inside the boat. Most importantly, unlike hydraulic trim tabs, there is no oil to leak out. The actuators incorporate either a standard or low-profile transom mounting bracket and is available in 12V and 24V DC with standard, short or heavy-duty style housings.
advancetrident.com
SEASTAR – DOMETIC:
Dometic Standard Trim Tab Kit – When it comes to a basic trim tab system, Dometic has redefined ease of use and practicality. Featuring an intuitive dial controller, adjusting the pitch and roll is simple to get your boat on the plane quickly and efficiently. A programmable favourites button makes for effortless operation. While an innovative, rugged design and auto-retract feature, ensure reliability and safety on the water, whatever the conditions. Features include:-
• Favourite planed position
• Push and hold start button
• Intuitive dial controller
• Easy user interface
• Intelligent actuator system
• LED position indicators
LENCO TRIM TABS:
Lenco Marine, a Navico Group Brand, offers a range of trim tabs, known for their electric actuators and durable construction. They provide options for both retrofitting and new installations. Lenco has the Auto Glide Boat Control System, which controls your trim tabs from the time you leave your shore until you come home again! The Auto Glide uses engine data and GPS data to drive your boat to the most efficient running angle by adjusting the trim tabs as needed. This optimum running angle is determined during the set-up process upon the installation of the Auto Glide system. They also offer a range of trim indicators, including the older style in-line rocker switch with trim motor and switch the load directly without any controller. The Lenco up/down switch panel with LED Indicators is supplied with waterproof connection plugs and includes an electronic controller and switch panel.
ULTRAFLEX TRIM TABS:
The innovative joystick by Ultraflex takes all the guesswork out of realigning the boat. Both trim actuators move simultaneously in opposite directions when pushing the joystick to port or starboard. This means the realignment of the boat occurs very quickly and with optimal tab positioning in terms of efficiency. UFLEX trim tab systems are available in 2 versions. The Ultraflex Trim Tab plates are high-performance polished or non-polished tabs and are stainless with mirror electro-polished blades. They are not designed for use in racing applications.
QUICK INTERCEPTA:
These interceptor trim tabs, are a complete ‘plug&play’ system. The central unit reads and predicts the dynamics of the boat to coordinate the movement of the trim tab based on the sea and navigation conditions. Intercepta is powered by a 10-30V motor and engineered with a completely integrated electric actuator and easy installation on every transom. Besides eliminating pitch underway, Intercepta by Quick improves the boat’s steering, consumption and dynamics. The range includes five models: IN30, IN45, IN60, IN75, IN100 for boats from 20’ to 130’, which can be combined up to a maximum of six units. These are expected to be on sale in New Zealand in early 2025.
ZIPWAKE:
A Swedish company, Zipwake offer smaller units for trailer boats as well as larger cruisers. The Zipwake, Dynamic Trim Control System (DTCS) comes in four model sizes, suitable for planning and semi-planning boats from 6m to 18m. One unique feature of Zipwake is that it offers two alternatives for the cable through the transom, either above the waterline or concealed through the hull. The above waterline option is an important factor to consider when retrofitting the units to trailer boats with moulded or glassed-in cockpit floors, making access difficult. Each Zipwake control panel is fitted with an internal GPS and equipped to read additional GPS source information (NMEA2000 and NMEA0183). The Zipwake Dynamic Trim Control System will automatically use the source with the best information to trim the boat. While the system is fully automatic, it will also let the operator manually adjust the pitch and roll settings to compensate for variations in different conditions, such as load.
