Trim Tab Brace

[taildrgr]

I just bought a 2005 Carver 396 Motor Yacht. When we pulled it out for the survey, I found both trim tabs to have a metal brace on them as shown in the picture. No one in the yard knew why they were there.
Does anyone have any experience with these braces? They do not slide, but at bolted tight.

[SplashyLady]

FUBAR! Bennett Marine (Tom Marloe) will probably reply to you message, but it looks like the hydraulics were shot, so they stuck the tabs into one position so they would not flop around. Good news is that Bennett Marine has great customer service - contact them and they will get you straight. Info@BennettTrimTabs.com

[tomschauer]

That definitely make the tabs immovable!

[tomschauer]

your surveyor thought they were some kind of support and are meant to be there, please find a new surveyor.

[Viper]

I've seen these a few times. It's a tab retention device. It takes the downward load off the actuator when the vessel is in reverse as I understand it. At that time, the water forces the tab down past the point you have set it at. Eventually, the ram in the actuator will bottom out, the bracket acts as a stop so that it takes the load instead of the actuator. When properly adjusted, it is supposed to slide then bottom out at the same time the actuator does.

[tomschauer]

Ok, looking closer I see its two pieces and could slide. But if you had the mid position bolt tight enough that the tab couldn't push down while backing, how the heck would the electric actuator be able to move it any time up or down?

[Viper]

The fastener in the slot should be just tight enough so that it allows the unit to slide but prevent slop between the two pieces of the bracket. You can see in the picture that the actuator is nearly fully extended and you can see the slot visible in the top bracket indicating that the retainer is nearly bottomed out.

You don't see these very often on pleasure craft but fishing charter vessels that require reversing at a much higher rpm than we typically do usually have these because of the pressure the water exerts on the actuators. When you revere, the water wants to push the tab down. Since you're only fighting spring tension in the actuator when it is not all the way down, the water will push the tab down until the ram bottoms out on the spring in the actuator. At that point, all the load on the tab is being transferred to the bottom of the actuator casing. The bracket relieves this load off the actuator. The only thing that prevents the tab from moving past the point you set it at unless it's all the way down is spring tension. You can push the tab down with one hand so imagine how much pressure the water would put on it at a decent rpm over the entire surface of the tab. I imagine the spring in the actuator is only designed to handle a little backward pressure for maneuvering while taking into consideration the weight of the tab and force required to push all the fluid out of the actuator once the valve opens during a retraction cycle.

PS, this is not and electric tab, it's a hydraulic one.

[Midnight Sun]

Mine are set up the same way. Look closely at the nut and you will notice it is of the is of the self locking variety and must not be tightened down fully allowing the brace to extend and retract. Obviously something added to later model year tabs. Vipers explanation a couple of post up makes perfect sense as to its purpose.

[Tabman]

Yup, it is a Tab Retention Device, RD1. And it should be able to slide and take the load of the Actuator when backing down. They are very effective at preventing damage or even having a Tab come of when backing down hard.

Tom
Bennett Marine

[taildrgr]

Thanks for the replies. The nut on the brace is tight. I looked at the brace carefully to see if there were slide marks but there were none. Definitely locked in place. At next haul out I will loosen it a bit and test the actuators. Surveyor thought the braces were tight due to a failed actuator. Have to haul it out for new bottom paint in May so I will get it looked at then. Thanks again for the comments.