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Running with only one trim tab?

Discussion in 'Stabs, Tabs & Gyros' started by RichV, Mar 14, 2021.

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  1. RichV

    RichV Member

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    I have a 1990 Ocean Yachts 48' MY with a rattle over 1500 rpm at the stern/rudder area which is also on the port side. My boat is currently hauled at Lamb's Yacht Center in Jacksonville FL. They were not able to track down the rattle and are guessing it is the trim tab. I don't believe that is the problem. The trim tab is just a thin sheet riveted to the hull with a hydraulic piston that moves it 3" max, and I don't use it on the port side because the boat lists to the port. My question if I remove that tab altogether (to eliminate that possible rattle source) and leave the starboard one how would that effect the boat running underway? The reason I am considering it is that I plan on installing the Zipwake system and I feel the current system is almost useless.

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  2. Pascal

    Pascal Senior Member

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    I ve never heard of a trim tab rattling... yours look a little unusual as I don’t see a hinge and it seem to be inserted in a gap in the hull. Or is it something with the picture.

    with the amount of pressure caused by water I don’t see how it can rattle. But I ve seen weirder things in boats

    does the noise change when you move the tab down ?

    only down side to removing it is that you won’t be able to adjust running angles.
  3. RichV

    RichV Member

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    The tab in the picture is disconnected from the piston while it was painted and you can see it's at it's maximum travel position. It's attached to the hull with 14 Phillips head screws. I've never seen a setup like that before.

    Not sure if having only one will affect the water flow under the boat.
  4. NYCAP123

    NYCAP123 Senior Member

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    "My question if I remove that tab altogether (to eliminate that possible rattle source) and leave the starboard one how would that effect the boat running underway?"
    Do you especially enjoy right turns? Btw, you shouldn't have so much list that it makes a trim tab useless. Check your weight distribution. If you ever lose your steering you'll need your trim tabs to steer... both of them.
    Btw, when I hear the term "rattle" and not vibration I think a sound coming from the exhaust.
    Last edited: Mar 14, 2021
  5. SeaEric

    SeaEric YF Historian

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    We sea trialed a 53' Ocean MY with only one tab working - one was all the way down and the other all the way up. At WOT the boat leaned over and wanted to nose dive. It scared the H&!! out of everyone aboard. That model and the 48 are only marginal in stability underway anyway. I would make sure that the tabs are BOTH working properly.
  6. Capt Ralph

    Capt Ralph Senior Member

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    That's Lambs; If you don't know (the usual), make something up and sell it..

    Out of the water, tabs are cheap to fix.
    Get both sides working before you splash.
    Get-er-done.
  7. Capt J

    Capt J Senior Member

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    NO, you cannot remove the trim tab. It's part of the running surface.

    IF your boat is listing that much to port, it is most likely the source of your vibration. The prop and running gear are under more load. You need to move (preferably or add) weight to starboard to remedy the list. I would also take a deep seated look at your stringers and bulkheads. You most likely are using your port trim tab to correct the list and it's wired to the starboard trim tab buttons as starboard tab would make the list even worse on plane, a lot of times they are wired opposite. You need to get an expert in to look at things and not throw money into the ocean fixing guesses.
  8. NYCAP123

    NYCAP123 Senior Member

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    Heard of a guy who got fancy and put a granite counter top in his boat's galley. Leaned right over. Had to go. Since the boat's not built to list I'd look for something that's been added on the port side. Dinghy, davit, ice maker, heavy gear, granite, tile? I'd rather find something to move or remove than add ballast on the up side.
  9. RichV

    RichV Member

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    I thought it was a crazy idea to remove a trim tab and I'm not going to do it. They do work but just don't do much. I'd like to learn more about how a "rattle" could be from the exhaust.

    As far as the listing goes, I don't understand why the boat was designed the way it is. Just about everything is on the port side; washer, dryer, fridge, fresh water tank, two beds, most of the closets. Even the dinghy engine is on the port side plus the water heater that was installed 2 owners ago. I'm thinking about adding another fresh water tank on the starboard side, where the old water heater is. I assume that it's not being used, but I just purchased the boat, and probably shouldn't assume anything.
  10. Capt Ralph

    Capt Ralph Senior Member

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    After we purchased our boat, I had always assumed it was a spare shaft that caused our stb list.
    I started placing spares and tools to port.
    When we finally got the boat on the hill and opened the transom spare shaft access cover, found it empty and dry.

    Fuel tanks are center line. Potable and black tanks do not effect the list either. Batteries (lots of them) are center line.
    The only thing to stb is our galley with full sized appliances and half of our queen sized stateroom bed.
    Across from the galley (down) is the port stateroom with queen sized bed.

    Currently both new gen-sets mounted to port. One water maker mounted to port, the second RO mounted center line. All heavy spares secured to port.
    She is level now

    When we do feel rich & famous and open the old girl up, she stays level (P&S) and the only tab used (both equally) is to help keep the bow down and tab use greatly reduced as speed increases.
    Still level at speed with no tabs.

    I gave up trying to figure the list out and just gave in; Our Bert dresses right.
  11. NYCAP123

    NYCAP123 Senior Member

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    Can't imagine why they would have added a water heater on the port side and left the old one in place, but if possible move it back. If it's a 40 gal. tank that's about 300 lbs. I'd do that rather than add a water tank whose weight will vary greatly depending how much it's holding at any given time. I'd also reverse the dink so it's motor is to starboard. Those 2 things could account for the list. If the washer and drier is stacked you could cut probably another 100 lbs. by converting to a combination unit. I don't see much else on that list that can be easily changed, but that could be enough. I've been on several boats, especially FBMYs where the trim tabs have minimal effect, but they still help some and they're there for if you ever need them to steer with IF the boat is otherwise balanced. Right now you're continually fighting the boat's weight distribution trying to make the boat turn left and that stbd. tab trying to turn it right. Sort of like having one person pull you left while another is pulling you right. Your boat doesn't like that any more than you would.
    A rattle in the exhaust could be caused by anything from something lose anywhere in the line to an anomaly in the sound of a cylinder firing. Other than tightening things along the line I wouldn't worry much about it. Just if it is from there you can end your search elsewhere. If it's coming from your running gear I'd expect you to feel a vibration with your feet when you stand on the main deck above or behind the position of your motors.
  12. cleanslate

    cleanslate Senior Member

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    Ocean did most of there boats tabs this way. Mine are the same . They make up there own tab out of stock 316 sheet metal and fab the size the need for each particular model. Then throw their hydraulic piston off the Stern lower transom pocket to the tab .
    It’s only 18 gauge sheet and they just screw it to the hole without a hinge it just flexes under pressure because it’s only a two or 3 inch travel.
    Yup don’t remove it and that is not causing your rattle whatsoever. Yes like the other said get them working.


    As To the running gear. Do you have a short shaft and a coupler, do you have loose props are the prop seated on the shaft properly are the struts snug...etc, etc.
    Start at the gear coupler and work your way to the end of the shaft inspecting everything in between till it’s found .
    Pull the props have them inspected at a good prop shop and gone over.
  13. NYCAP123

    NYCAP123 Senior Member

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    That's an interesting (and IMHO bad) way to do tabs, and could account for them having minimal affect. If that's the case for the OP I'd recommend investing in a set of Bennet's. I remember coming into Ocean City, Md. in the 43 Ocean and his tabs were needed to keep me off the jetty. I never inspected his tabs but I suspect they weren't as you describe.
    Agree a prop/ forward inspection of the running gear on this boat when he next hauls would be a good idea, but attending to that list would be my first priority. Lots of perceived problems may disappear once that's corrected.
  14. d_meister

    d_meister Senior Member

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    I ran a 68' aluminum Roamer for a few years, and the thing would always list to port at the dock unless the fuel tanks were jugged. I finally found out that any little bit of list would cause the bilge tanks to equalize through the crossover and increase the list, but it would never flow back to even out. I started to close the crossover after fueling, and the list never returned.
    Thought I would mention that because your Bert shares some design DNA, I think.
  15. NYCAP123

    NYCAP123 Senior Member

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    You should have checked your vents. Once the list begins it's hard for the liquid to flow back, especially if there's not enough air flow to replace it. Liquid seeks its own level but it can attain that by listing the boat. Then gravity takes over and it's hard to push the liquid up hill, especially if there's a near vacuum behind it.
  16. d_meister

    d_meister Senior Member

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    There was never a reason to suspect vents on that boat. The fills were higher than the vents, and even the inverted "J" hook of the vent hose. The vents burped diesel so reliably, that I taped a dust pan ( the kind that clips to a broom handle) to the hull with 2" blue tape and placed a bucket under it. Worked great for catching the overflow.
  17. NYCAP123

    NYCAP123 Senior Member

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    Except that the fuel wouldn't return.:rolleyes: In fact if it burped while fueling that would be an indicator because the fuel is going in steady and as it does that the air should exit smoothly.
    Btw, they make gizmos for that overflow:
    https://www.jmsonline.net/no-spill-fuel-recovery-system.htm
  18. RichV

    RichV Member

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    I also do not believe the trim tab is rattling. I still think it's the connection between the rudder arm and connecting rod. There only seemed to be a bolt and no bushing, and it had a fair amount of play. Lambs doesn't seem to think it's an issue. It's a constant rattle over 1500 rpm.

    I did not feel any vibration when it rattles. The props were just changed and it still rattled. Two different yards and 2 different divers have not found anything wrong with the shafts or struts. But until the source is found I'm not eliminating anything.

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  19. NYCAP123

    NYCAP123 Senior Member

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    Possibly that key is worn. Possibly something isn't tight. Put someone on the helm in open waters and ride down below. Shouldn't be hard to zero in on a rattle, but there's a lot of places it could come from.
  20. bayoubud

    bayoubud Senior Member

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    Loose rudder connections would be a good place to check. The rudders are in the prop wash, with a lot of variable pressure.