Trim tab performance

[JCG]

I have a 46 ft 1975 Hatteras Sport fisher with Bennett trim tabs. The units don't work and I am considering fixing them. How important are they for this boat with a cruise of about 18 knots? Would it make sense to just lock them in a fixed position for best cruise performance, or do you really need to balance the boat (port/starboard) out while underway?

 

[Boss Lady]

I think they are important to maintain a more level ride and efficient cruise. You can get new parts on ebay for cheap to fix them.

 

[Trojan]

FIX THEM! They are one of the most important things for performance. They enhance, control, speed, ride, attitude, fuel use and handling. Your boat is forever changing in its ride. There a cheap fix, an easy fix and well worth it.
Who knows fix them and maybe you can reach 20 knots. I set the throttles then the the trim tabs for max speed or ride. Depending on conditions.


BILL

 

[yachtsmanbill]

I agree, not only for trim, but for "attitude" or is that "HATTITUDE" ? ws

 

[Boatsb]

Hei I own the hattitude and it has no tabs. Someone did a nice 1" rise in the stern across the whole transom though and she rides great . Just cant adjust side to side. For fishing tabs can be in the way. For cruising they are great.

 

[REBrueckner]

I've never been personally sure that trim tabs do much except raise or lower the stern (and bow angle) of my boat at higher speeds. But maybe they do. Since Hatteras installed them, I figure they must accomplish something, as posted above. If my boat is listing I balance it via fuel tank usage so its level at rest. How well does a "better" run angle offset the extra drag of tabs??

On my 48 YF I can't tell if speed changes; I don't see any difference on my GPS speed, but that changes due to varying currents encountered anyway....angle of running is flattened when the tabs are down. When I lower my tabs to "bring the bow down", I can see a change in the bow spray and wave so there is a difference. I'd personally prefer wedges permanently affixed at the stern. But tabs are great for growing barnacles!

If anyone has ever compared speeds at different tab settings I'd sure be interested...if it's 0.1knot or closer to 1.0 knot (which I doubt).

In any case, there are basically four components to the system: motor (pump) and wiring; hoses;cylinders; and fluid. Plus the flat tabs. Each has to be checked...

As a minor note: The bridgedeck windshield motor (used to open and close the center windshield window on my 48 ft YF) IS a Bennett trim tab motor

 

[Bill Allen]

On my 43 I can't hardly plain without tabs, of course I have 6-71n's. Of course at hull speed it doesn't really matter and I usually retract them thinking i'm saving fuel (it's the scotch in me). On the dive boat it can make as much as 3kts difference due to the heavy load. I would think a s.f. would be much the same with all the ice, bait and passangers. Plus the ability to trim side to side can also add up to a kt. Bill

 

[garyd]

I believe this is a must have item. I'm not sure where you are located but Marine Surplus in Bradenton, FL. has some parts at a decent price. Call over there and ask for Tony.

The only way I wouldn't have tabs on any power boat if it only cruised at 6-8 kts. When you cruise above 20 kts you cannot do without them.

Have fun boating garyd

 

[34Hatt]

The only way I wouldn't have tabs on any power boat if it only cruised at 6-8 kts. When you cruise above 20 kts you cannot do without them.

I found it too be the other way. When I had the old motors cruise was 14kts tabs all the way down. With out them 12.5 kts. Now new motors cruise 22-24kts tabs all the way up as I put them down my speed goes down. I lost a tab in August ran rest of season with no big deal a little lean to one side sometimes. But they will be fixed before hitting the water I still feel they are a must have

 

[garyd]

You are correct on most boats the faster you go the tabs come up. I was really just talking about leaning. If you get a good cross wind the boat will almost lean on it. That 5-10 degree list drives me nuts. So I gotta trim it up/out. Course I also straighten out crooked pictures on anybodies wall. LOL

Have fun boating garyd

 

[waymaker]

I find the trim tabs very useful for getting on top and also balance. While at cruising speeds I can decrease the tabs ever so slightly and the bow rises significantly, reducing my cruise speed. So I keep them down while cruising. I think that is from the bow high attitude of a Sportfish. Not sure how sensitive they are on other models such as Yacht Fish etc.

 

[Boss Lady]

The tabs on my YF made a 2 kts difference at cruise with the old motors, we will see what happens with the new engines. The angle of thrust from the props greatly affects the efficiency of forward movement. The bow high attitude just wastes forward thrust and tries to lift the boat instead of pushing it. They are called "Trim" tabs for a reason. A lot of old boats had a fixed wedge tab added after they were designed to get the bow attitude corrected. Modern designs use adjustable tabs, because you can adjust in real time for the speed and conditions. The fixed wedge was set for one speed. Typically the slower the speed the more tab you need, since we don't get full skim board effect with heavy boats, we use a lot of tab all the time, so I our point of view is skewed a bit when it comes to the use of tabs. It is not an earth shattering experience to go from zero tab to full tab in a Hat, however, do that on my Fountain and you can see "huge" differences how they affect the boat. One of the main reasons we need tabs is the shaft angles on our boats causes the bow to lift since the thrust is trying to lift the boat as well as push it forward. The tabs counter act this lifting force. Full tabs will help you get on plane quicker too.

The use of prop tunnels tries to maximize thrust by putting the props at zero degrees, versus the downward angle we all have on our boats which causes a huge loss of forward thrust efficiency.

 

[garyd]

I would not try the no tab to full tab while cruising at 26+ kts. And I absolutely wouldn't do it at WOT 33KTS.

On my 41C the less tab the further back she sits and the faster she cruises. Typically you like to get the CP ceter of pressure as far back as possible for performance. Of course we could go into a complete discussion on that subject but it would take volumes.

There is a CG center of gravity and a CP. Trim tabs are not going to change the CG but can have an effect on CP. This effect can be good and can be bad. You have to know what you are doing with trim tabs. As the speed increases they can save your butt or burn it! LOL

have fun boating garyd

 

[Dodger]

Tabs don't work? Call Bennett at 954-427-1400. They have an awesome customer service reputation.

Explain the prob to the rep. Chances are they will diaognos over the phone and send you a replacement part free regardless of your warantee status,

That's what they did for me

 

[Will]

Count me in with those who believe trim tabs are worth while. They make the difference between 12 kts (tabs up) and 14 kts (tabs down) at normal cruising on my 43' with 6-71 TIs. In view of current fuel prices, they make a difference in operating costs over time.

However, they should not be fixed in the down position since they create drag at slow speeds and can cause problems by forcing the bow down in heavy following seas.

I'd repair them.

Will

 

[34Hatt]

garyd You are correct on most boats the faster you go the tabs come up. I was really just talking about leaning. If you get a good cross wind the boat will almost lean on it. That 5-10 degree list drives me nuts. So I gotta trim it up/out. Course I also straighten out crooked pictures on anybodies wall. LOL

O.K we are on the same page and that 5 degrees is what I had to live with for 2 1/2 months. And those crooked pictures drives me NUTS also can't figure out how they live with them like that.

 

[labrador]

On my 40aft cabin I can only get 16.5 with no tabs, fully down 20kts. Huge difference

 

[jim rosenthal]

The hull was designed for trim tabs. While Hatteras hulls are generally quite well-designed and perform well, the naval architect has very little control over what happens after the boat leaves the plant and people begin climbing aboard, so the tabs provide the ability to adjust the boat's running angle....

Early 36Cs like mine have BoatLeveler tabs. The company is great about repair and helping you get the best performance out of them. The tabs themselves are somewhat trouble-prone. I keep a lot of spare parts on board. That said, the quality of what they sell as spares continues to improve- they are still refining the design.

There have been so many posts about Bennett and the level of their customer service that frankly I wish they built a sports car. Or a complete boat. Or a computer. Or a motorcycle. Then again, maybe they are as good as they are because they know what they do and stick to that. Regardless, you should get your tabs working as they are supposed to, and if they are Bennetts they will give you a lot of help.

For a while, I was all keen to get Lencos, which are electrically-driven screw-jack units that are not hydraulic. Then I began hearing that they leak, and stop working. So I have stayed with BL.

 

[REBrueckner]

labrador: are your tabs under the hull or do they stick out aft? It would seem they'd have more leverage astern. I've always wondered if there was much difference between the two locations.

Even a 1/2 knot change, say at 15 knots is significant...over 3% and if even close to 2 knots or roughly 13%, tha's huge!!...well worth the cost...

 

[Nick]

I had Bennett tabs on my last boat. The customer service is incredible as others stated above. I needed a replacement hyraulic pump. Bennett sent me a new one for real cheap as long as I sent the old unit back! The old unit was original and about 20 years old. Bennett also sent me the seals and hinge pins for the tab pistons free.

The tabs are a must in my opinion based on various weather conditions, sea conditions and speeds. Least needed in fair weather at fast cruise.

Did we beat this horse to death?

Have a great Holiday!

Merry Christmas