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Trim Tabs explained

THE PRINCIPLE OF TRIM TABSConvenience 
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
.

Trim tabs - Stainless steel suggested

Actuators - Upper hinge material (part #A1103) made of flexible nylon.  Remainder of actuator made of high impact fiberglass filled nylon.

Hydraulic Power Unit (HPU) - HPU draws a maximum 18 amps (broken-in) and operates on 12 volts DC (except 24 and 32 volt HPUs).  Approximately 22 ounces of ANY TYPE AUTOMATIC TRANSMISSION FLUID (ATF) is required to fill the reservoir to proper level for single actuator installations.  With the trim tabs fully retracted, proper fluid level is about 2" from the bottom of the reservoir. 

The HPU forces both trim tabs full-up to full-down in 9-10 seconds, individually in 4-5 seconds.  (Trim tab travel on dual actuator systems takes twice as long.)

Helm Control - Controls on 12 volt systems use 20 amp in-line fuse.  (24 and 32 volt use proportionally smaller.)   

Hydraulic Tubing - Tubing has 1/4" outside diameter and 1800 lb. burst pressure.

Wire harness - Wire colors and their functions:

    Red wire                                  Port solenoid valve
    Green wire                              Starboard solenoid valve
    Blue wire                                 Motor forward (pump pressure)
    Yellow wire                              Motor reverse (pump retract)
    Black on HPU                         Ground
    Orange on helm control         Positive

diagram.jpg

 

Diagram Number

Description

Part Number

1

Fluid reservoir

VP1139

2

#10 x 1" screw

H1180

3

Filler Stack

--------

4

Filler Plug

VP1140

5

Mounting bracket for HPU

H1179

6

Lexan cover

VP1138

7

Type 25 thread cutting screw

VP1154

8

Motor strap

VP1142

9

Solenoid valve

VP1135-R
VP1135-G

10

Faceplate for HPU

VP1144

11

1/8" pipe to 1/4" tube connector

VP1146

12

Hex retainer

VP1141

13

Nut with ferrule

T1127

14

Hydraulic tubing (20' unless otherwise specified)

H1171

15

Tube bending clip

H1173

16

Female elbow

H1172

17

Pipe nipple (3" unless otherwise specified)

H1171

18

Upper hinge

A1103

19

#14 x 1-1/2" screw

H1174

20

Cylinder body

A1105

21

Piston with o-ring

A1109

22

Lower hinge pin

A1115

23

Lower hinge

A1113

 

25

Backing plate

varies with size

27

Hinge plate

varies with size

28

#10 x 1-1/4" screw

EH1071

29

Trim tab only

varies with size

30

1/4-20 x 3/4" machine screw

H1175

31

Wire harness (22' unless otherwise specified)

WH1000

32

Quick-disconnect plug

VP1143

33

Nylon hanger

H1177

34

Single lever control

VC1000

35

20 amp fuse (12 volt system)

H1176

36

Fuse holder

H1178

37

Racing type control

RT1000

38

Rocker switch control

RS1000

Trim Tab System Information and Troubleshooting

1. If trim tabs do nothing...no movement...no sound from HPU -
  
- Inspect for blown 20 amp in-line fuse in helm control's orange wire.
    - Inspect for disconnected or corroded connections on HPU ground wire, orange positive wire from helm control, and quick disconnect plug.

2. If HPU runs but trim tabs do not move -
   - Inspect for disconnected or corroded red and green valve wire connections at helm control and quick-disconnect plug.
    - The following test can be used to help isolate the malfunction.

Remove wires from helm control and touch together as follows:

Operation

Reaction

Orange (+), blue, red

Port trim tab down

Orange (+), blue, green

Starboard trim tab down

Orange (+), blue, red, green

Both trim tabs down

Orange (+), yellow, red

Port trim tab up

Orange (+), yellow, green

Starboard trim tab up

Orange (+), yellow, red, green

Both trim tabs up

    - If the tabs function properly in each of the above combinations, check the helm control.  If during this test the trim tabs continue to malfunction, inspect the HPU.

3. If one trim tab operates and the other does not -
    
- Inspect for disconnected or corroded red or green valve wire connections at helm control and quick disconnect plug.  (Red wire operates port trim tab; green wire operates starboard trim tab.)
     - Reverse the hydraulic tubing at front of HPU to determine if malfunction is in HPU or actuator / hydraulic connections.  If ,after reversing lines, the symptom shifts to other trim tab, a malfunction may exist in HPU.  If the symptom remains on the same side, a malfunction may exist with the actuator / hydraulic connections.

4. If trim tabs go down but will not retract -
     - Inspect for low voltage of the batter.  Check battery voltage while HPU (or another accessory) is running.  If voltage is less than 10 volts, valves will not open.
     - Inspect for disconnected or corroded connections on helm control and at quick disconnect plug.

Maintenance

- Periodically, check fluid level in HPU.  With trim tabs fully retracted, fluid level should be about 2" from bottom of reservoir (approximately 22 ounces).  To refill, remove the lexan cover and filler plug located on the front left hand corner of the reservoir.  FILL WITH ANY TYPE OF AUTOMATIC TRANSMISSION FLUID (ATF) ONLY.  Brands or types of ATF can be mixed.  Running the HPU with excess or lack of fluid will not cause damage.

- Periodically, check for clean electrical connections on the back of the control, HPU ground wire and quick disconnect plug. 

- Cold temperatures do not affect the trim tab system.   No winterization is necessary.

- SALTWATER ONLY - To deter electrolysis, a zinc anode should be attached to the top of each trim tab.  The zinc must make direct contact with the stainless steel.  In the case of trim tabs installed on the boat as original equipment by the builder, a bonding system may be utilized for your particular model.

- We suggest using anti-fouling paint to help protect the trim tabs from marine growth.  The secret to getting anti-fouling paint to adhere to your trim tabs is proper priming, and the best people to tell you what to do are the experts at the company that makes your anti-fouling paint.  We strongly suggest that you contact the paint manufacturer and tell them you are painting "304 stainless steel" trim tabs, then follow their recommendations to the letter!  Remember don't paint under the zincs.

- Unpainted trim tabs may acquire an orange discoloration.  THIS OXIDATION OF SURFACE CARBON MOLECULES IS NORMAL.  Orange coating can be cleaned off, but will eventually return.  Note: this discoloration should not be confused with the pitting and corrosion of electrolysis.

 

How to Use Trim Tabs

GETTING STARTED
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.

TAKE OFF comp.jpg (17506 bytes)
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 CONDITION coml.jpg (17480 bytes)
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 POWER TRIM
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.

Trimmed2.gif (18076 bytes)Untrimmed


 

 

 




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
.

CORRECTION OF PORPOISING
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.

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