Marine Trim Systems & Performance Enhancers
How to Plane a Boat A Better Ride for Small Boats Article courtesy of Bennett Marine
Small boats from 10 to 20 feet have many of the same planing challenges as larger boats but may not need adjustable tabs to correct these issues. In less than an hour you could improve your hole shot and reduce the speed you need to get on plane.
The Right Attitude
Your boat achieves its best possible running attitude at or near full speed and lightly loaded. The trouble is, as you know, most of the time you are not operating your boat this way. As the boat slows from maximum speed, it begins to settle at the stern or "squat," creating an inefficient, untrimmed condition. At this attitude you use more fuel to drive the boat.
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. Also because of significant hull drag and extreme prop angle, fuel economy is poor.
Trim tabs reposition the boat's bow to cut through the water. Keeping the sharp forward sections of the bow down in the water, cleaving the oncoming chop, is what results in a smoother ride.
Whenever possible, installing remotely adjustable trim tabs will give the best possible control over the broadest range of conditions. But for some smaller boats that need help getting on plane faster and staying on plane at lower speeds, trim tabs that adjust due to the water pressure under the trim planes are an option.
These self-leveling trim tabs will help you: Plane at lower speeds Improve fuel efficiency Reduce pounding Improve your hole shot Reduce engine laboring Eliminate porpoising and chine walking
The "Plane" Truth
Just like adjustable trim tabs, self-leveling tabs like Bennett's SLT keep the boat running at its most efficient attitude over a broader range of speed, weight and water conditions. The SLT reacts instantly to boat speed and water pressure by adding trim when it's needed. At slower speeds, when the boat is trying to get on plane, the actuators hold the trim tabs down, which lifts the stern and simultaneously puts the boat at planing attitude. On plane, and as the boat's speed increases, water pressure pushes the tabs up.
Planing at lower speeds gives you several advantages: Less drag and engine laboring, which translate into increased performance, greater speed and reduced fuel consumption Reduced pounding, which means greater comfort Greater visibility, which increases safety
Of course, visibility is a much bigger issue in smaller boats. With trim tabs installed, giving you far less bow rise, you will be able to see where you're going without having to stand up.
Also, on smaller shallow water fishing boats with limited electrical capacity and a desire to keep things simple, trim tabs that retract under water pressure will allow these boats to take off in skinny water without increasing their draft due to stern squat. They can also plane at much lower speeds (again with a shallower draft) without compromising high speed performance.
Planing at lower speeds also has benefits for watersports. You can get a skier out of the water faster with less strain, and it's great for teaching kids to water ski (no big scary wakes to contend with) as well as pulling the young ones around in a tube.
Unlike adjustable trim tabs, self–leveling tabs cannot compensate for side-to-side changes in weight distribution "on the fly." However, they can be adjusted for "permanent" side–to–side conditions such as propeller torque, or a single weight location of a driver. Correcting both of these conditions can be extremely helpful in a small boat.
Lastly, often on tiller steered outboard boats operators will use an extension handle on the tiller to get their weight forward to hold the bow down. But this makes it harder to reach the shift lever as well as maneuver the boat while docking. By adding incremental lift at the stern, the self–leveling tabs will usually eliminate the need for the extension.
Small is the New Big
Again, if you have a small boat you may not need an adjustable trim tab system to boost your boat's performance. Self-leveling tabs can correct your planing problems at a fraction of the price, and with less installation time – so you can spend more time out on the water. Article courtesy of Bennett Marine, the largest manufacturer of trim tabs in the world. Check out the selection and special pricing for Bennett trim tabs for small boats.
How Do Trim Tabs Work?
How Do Trim Tabs Work? Article courtesy of Bennett Marine
So you're convinced of the benefits of trim tabs: a better ride, fuel savings, greater visibility; and now you just need to select the right tab for your boat. This decision will actually have a major effect on the effectiveness of your new tabs. When sizing for your tabs, "Bigger Is Better".
Installing undersized trim tabs is one of the more common mistakes for new trim tab owners. A tab that is too small will have to be deflected more in order to create sufficient lift and could actually create more drag than the lifting benefit. The larger the trim tab, the more lift it will produce with the least amount of drag.
Remember this guideline: When making a choice between trim tab sizes, the largest trim tabs that will comfortably fit on the transom will be the most efficient.
As a rule, choose at least one inch of trim tab span (per side) for every foot of boat length. (Examples: 22-foot boat = no less than 22" x 9", 36-foot boat = no less than 36" x 9".)
To understand sizing, you have to know how trim tabs work. Trim tabs improve the performance of your boat in a much wider range of weight, weather and water conditions. The purpose of trim tabs is to recreate your ideal running attitude, even on a rough day. Much like ailerons and elevators on an airplane, trim tabs provide lift to compensate for changing conditions.
Three variables combine to affect lift: Size of the trim tab surface Angle of deflection Water-flow under the tab (caused by speed of the boat) When they are deflected downward, the water force on the trim tab surface creates upward pressure, raising the stern and lowering the bow.
As you can see, surface area plays a big role.
Trim tabs are described by their span and chord measurements:
Span = side to side measurement Chord = fore to aft measurement
The span of the trim tab has more of an effect on the amount of lift. However, a longer chord can be used effectively, and there are situations where you may need to use a longer chord. Such as for boats with limited transom space that limit trim tab span. And for slower boats (less than 15 mph), semi-displacement hulls, boats over 50 feet or boats with any other feature that increases the need for lift aft.
Make sure the trim tabs will fit your transom using the diagrams below as a guideline. When measuring, disregard the strakes and follow the Vee of the hull.
Trim tabs should follow the Vee at the junction of the transom and the bottom of the boat. For maximum side-to-side control, trim tabs are generally mounted 3-4" from the chine and run towards the keel.
In case of inboards, the complete run from chine to keel may be utilized if it is an unbroken span of the same angle. Protrusions, such as strakes, may be bridged provided there is no change in angle on both sides.
On boats powered by inboard/outboards (I/O) or outboards it is necessary that the trim tabs not be placed too close (8" minimum) to the lower unit(s) to avoid disturbing the water flow to the propeller.
Trim Tab Mounting
Two types of mounting hinges are available:
Transom Mount - This hinge style fits to the boat's transom and is used in the majority of applications. The transom mount includes three parts - a backing plate mounted against the transom, a trim plane and a hinge plate.
Bottom Mount - For vessels that have curvature in the transom. It can only be used if a flat section of the hull bottom is available to accommodate the hinge.
After decades of use on the water, it's been proven that all boats, large and small, benefit from trim tabs. However, having the right size tab will make all the difference in just how much your boat's performance improves. Article courtesy of Bennett Marine, the largest manufacturer of trim tabs in the world. Take a look at the wide selection of Bennett trim tabs for your boat type, size and boating use at iboats.com.