Trim tabs

I have never owned a boat with trim tabs before this one. Not sure, how they are to be used. In what condition would you want the bow down.
As always thanks for the advice.

Henry
Linda Lee.

depending to you seep hull and type of hull.

Hugues

Start with the tabs all the way up, neutral effect. Use them to put the boat on an even keel underway to start, they can offset wind and loading conditions once you get going. Then experiment with the throttle fixed and watch for changes in speed. Depending on the vessel and conditions you may pick up a little speed. If you find yourself pounding into a sea, putting the bow down may smooth out the ride.

A start

hfmckevitt said:

I have never owned a boat with trim tabs before this one. Not sure, how they are to be used. In what condition would you want the bow down.
As always thanks for the advice.

Henry
Linda Lee.

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I know nothing but just bought a boat with trim tabs. The utility of them and how they are used will depend to a large degree on the type of hull you have. Here is the thread where I asked the same question.

and never forget to put you flap up before going reverse (you can kill all !!!)

Trim tabs are useful on semi-displacement hulls at higher speeds. When I push my throttle up the bow comes up and it accelerates. Then I add trim tab and the bow comes down and the boat accelerates another couple of knots.


I suspect that virtually all semi-displacement hulls need full trim tab to comfortably go over 10 kts.


I recently added drop fins to my Bennett tabs to increase planning performance. I will let you know how that works in a few weeks.


David

Come in handiest on a planing boat. Or if you have a slight list to one side.
Leave them up in a following sea regardless.

Thanks to all

101TUG said:

and never forget to put you flap up before going reverse (you can kill all !!!)

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I've never raised my trim tabs before reversing and I've had them on many boats including some that would go 50 knots. How have you experienced a problem? Or heard of it?

A good thing to do is observe the tab operation from the dock in clear water.
Some boats are set up differently. For example, pushing the Port BOW DOWN button may either lower the STARBOARD tab (what I'm used to) or the PORT tab. That's something that is checked out when the boat was new or tabs were installed. Some PO's then change the setup to their liking.
Too much tab can be bad for economy by creating excessive drag. When in doubt, start with tabs full up, drop the tabs a little and WAIT for the boat to respond. It takes a while!

some seem easily damaged while others not by backing down....most likely a result of install and max down angle attained.

The other use of tabs is unbalanced load side to side. With the quantity of fuel and water carried as well as people just adjusting for load, fore and aft, port and starboard, as you go though various states of load makes them very valuable. On the lake on fast boats, typically it was tabs down to get out of the hole quickly and then raise them and for speed it was raising them to the maximum level without causing porpoising. On a light and fast boat their impact was huge.

On my 7 knot boat I find tabs quite usefull.
When we bought the boat I questioned the tabs but I found:

They can knock down a large rolling wave reducing the wake.
You can hear the engine unload a bit.
They can be used to trim the boat side to side.
When in a good size following sea I retract them fully to reduce the bow being shoved into the trough and back of the next wave.
As fuel burns off and water is used I retract the tabs a bit to account for the trim change when running..

Even on many slow boats they can have a very usefull effect. I'm sure some vessels will see little or no effect but if you have them try them out and see what happens. You may find they have a noticeable effect to the good.

C lectric said:

On my 7 knot boat I find tabs quite usefull.
When we bought the boat I questioned the tabs but I found:

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I have them and don't know yet how to use them. I run at typically 7 knots. I have used them to get rid of a list from one water tank being full and the other empty, but other than that I need to just experiment.

You will have to play with them. The effects will be boat specific although some generalities can be offered.
One my previous boats I had much larger tabs but they were full out planing boats and the tabs could actually cause some unwanted handling effects if overused.

I suspect that won;t be the case for you. I suspect the primary uses will be to affect beam trim, knock down a large wake and help fore/aft trim.
That large wake knock down will reduce fuel use but in most cases so little that you will not really see the effects.

But I will caution that when in a big following sea , retract them. They will raise the stern effectively pushing the bow into the water which you do not want.

Capt.Bill11 said:

How Do I Use My Trim Tabs? - Bennett Marine

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Great link. Bennett was the leading innovator in the world of trim tabs. They're the only brand I knew of for most of my life.

I am going to lengthen the chord from 9 to 12 inches on my 42 inch long tabs.
Plan to weld on some 304 SS and also add some down dropping winglets.

Also plan to coat them with POR 15, that will help them survive corrosion, I figure.
Less exposed metal surface to the water after POR15 seals them. POR15 also good for sealing up small corrosion holes. Somewhere I read POR 15 Silver color was better than other colors??

Ah yes, POR15 Silver has the metal fillers. So it can fill holes. I talked with some people who have repaired damaged Tabs with POR 15 Silver.

http://www.por15.com/POR-15-FAQS_ep_61.html

Silver contains metal filler and should be used in badly rusted, pitted areas. It will fill in holes better than black or clear. Black is generally used on frames, underside of fenders, etc. because that's the usual color

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Another option is use FG cloth on top of the SS to seal the Tabs.

CAN POR-15 BE USED WITH FIBERGLASS?
Absolutely. POR-15 is fully compatible with fiberglass and can be used to repair cracks in gelcoat. It will adhere better than polyester resin and has greater strength. Use also with fiberglass cloth to make super-strong surfaces in rusted-out areas. But be aware that POR-15 doesn't contain styrene and thus cannot melt fiberglass cloth like polyester resin does.

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Tabs are protected with zinc anodes, but zincs do melt away. Less metal exposed means zincs should last a much long time. Tabs when zincs are gone will quickly corrode, pits and odd channels run through the SS. Too bad they did not use 316 SS to make tabs.

Bennett trim tabs are the most reliable brand of tabs available. This is especially true for non trailered boats. The other two brands of US hydraulic tabs, Boat Leveler and Trim Master are essentially unavailable. The two main brands of electric trim tabs, Lenco and Letro Tab have repair/replace issues for larger boats in the water.

Almost all Bennett repairs can be accomplished in the vessel. A very high percentage of problems with these systems is electrical or control in nature, or a pump issue. There is only one moving part on the transom, the piston ram, an extremely simple and robust component.

Electric tab failures tend to be in the electric motor actuators (rams) and unless the upper portion of the ram is above the water line and accessible the vessel needs to be hauled to replace.

I have seen Bennett systems 10 and even 20 years old that still work fine, very few products on a boat can make that claim, and Bennett's customer service sets the bar for customer satisfaction.

I do not work for Bennett About Us - Bennett Marine

BandB said:

Great link. Bennett was the leading innovator in the world of trim tabs. They're the only brand I knew of for most of my life.

Click to expand...

Keysdisease said:

I have seen Bennett systems 10 and even 20 years old that still work fine, very few products on a boat can make that claim, and Bennett's customer service sets the bar for customer satisfaction.

I do not work for Bennett About Us - Bennett Marine

Click to expand...

In over 20 years of use of Bennett, I've never encountered any problems with them.