Trim tabs

[Al Bartlett]

My vessel (50’ OA Classico Trawler) is fitted with trim tabs operated by switches in the pilot house and fly bridge. My vessel’s top speed is 10 knots but is never taken above 8, Which is about Max hull speed. My question is, is there any value in having these trim tabs? They were installed when the vessel was built in 2007 and presumably the designers thought they would be useful, but other than eat up zinc anodes they seem to serve no purpose. Suggestions from anyone who has some insight to this would be gratefully received.

 

[rsn48]

The usual answer is to trim your boat if it is heeling to one side. I've had this happen when I drained one fuel tank, forgetting to use the other. The weight of the full tank with the loss of weight in the empty tank creates a heel, then I use the trim tab.

 

[rslifkin]

The only way to know for sure if they're doing anything useful is to try putting them down at cruise speed and see if anything changes. If you gain some speed at a given throttle position with them partly or fully down, they're helpful. If not, they're not really useful. But removing them won't gain you anything other than 1 less set of anodes.

 

[Al Bartlett]

Thanks for the replies. I always have both tanks common feeding the engine, but I can see how tabs could be useful if heeling was an issue. I really couldn’t see any appreciable difference while experimenting with their settings - just concerned about adding drag and increasing fuel useage. I guess they can just sit there for the next owner of the boat to play with - or not.

 

[rslifkin]

If they're fully retracted they shouldn't add any measurable drag compared to them being removed, so I wouldn't worry about that.

 

[Comodave]

We have tabs on our boat but it will do 17 knots full out. We never go over 10 knots and have never used the tabs even for trimming side to side. But I am not planning to take them off since they really aren’t hurting anything. I do have to replace the anodes every couple of years though.

 

[C lectric]

My boat is a 7K vessel. Said this many times. THey can and do help. Can even out a list while running, knock down the big rolling stern wave, I can hear the engine unload slightly although this won't necessarily increase speed since the governor will maintain the same revs.

As said you need to try them out.

When I first got my boat a long time ago I too thought , useless. Well, I played with them and realized they do have an effect on the boats running.

In a rough following sea they are fully retracted.

 

[Alaskaflyer]

On plane, I would use them in choppy head seas to smooth things out a bit, at the cost of some additional drag (not that fuel efficiency could be much worse in those conditions anyhow.) In a heavier vessel at hull speed or less, has anyone noticed any benefit in this regard? My guess would be no, but...