410 DA Trim Tabs-for Tabman

[HUMPH]

Yes, Trim Tabs with the drop fins built into them are available. They are also available as add ons for existing flat Tabs.

Tom
Bennett Marine

I would be very interested in the larger tabs with drop fins. How does one go about getting pricing and ordering?

 

[Tabman]

I would be very interested in the larger tabs with drop fins. How does one go about getting pricing and ordering?

Tell me what size you need and I will get the part numbers for you. Then you can shop the dealers for your best deal (try BOE!).

Tom
Bennett Marine

 

[HUMPH]

Tell me what size you need and I will get the part numbers for you. Then you can shop the dealers for your best deal (try BOE!).

Tom
Bennett Marine

I have the same tabs as Rick but I am not sure what size I need. I guess I can get in the water and measure? Do these replace the existing or attach to them? Sorry for the nasty look in this picture, this is when I "saved" her in Newport Beach. Looks a bit different now.

 

[osd9]

Would putting tabs directly over the props and rudders cause other issues? Possibly cavitation or changes in water movement when the rudders are turned?

 

[Tabman]

I have the same tabs as Rick but I am not sure what size I need. I guess I can get in the water and measure? Do these replace the existing or attach to them? Sorry for the nasty look in this picture, this is when I "saved" her in Newport Beach. Looks a bit different now.

HUMPH,

We do make bolt on drop fins that could be added to your existing Trim Tabs. In theory adding larger Trim Tabs that ran all the way to the end of the tunnels would be better.

Tom
Bennett Marine

 

[HUMPH]

Sounds good, I'll get measurements and touch base. I would love to throw the bow down a bit easier.

 

[Tabman]

Would putting tabs directly over the props and rudders cause other issues? Possibly cavitation or changes in water movement when the rudders are turned?

OSD9,

No, if you think about it most inboards without pockets have Trim Tabs that run across the transom over the rudders and props, and they work fine. I would not suggest drop fins in that location since the prop wash is turbulent and spreads out as it exits the pocket and may cause vibration.

I love this picture of great big Trim Tabs on this old Roamer, the owner said they were like Viagra for his old boat! You can see how they run across the the props. This is about the most efficient Trim Tab installation there can be. They are only 9" chord (fore to aft measurement) but use the entire width of the transom.

It's interesting to note that Hatteras incorporates Trim Tabs into the "roof" of their propeller pockets. They think that the accelerated water flow there generates more lift when it is deflected by the Trim Tab, and I agree.

Here is a picture:

Tom
Bennett Marine

 

[HUMPH]

Very interesting having the tabs in the tunnel. I never would have thought of that but, of course, that is why they build great boats and I don't I guess.

 

[mistercomputerman]

How about the first 410DA owner who has their boat out of the water or who physically gets in the water does the measurements and shares them with everyone else?

Water is pretty cold here right now and I have already been out 3x this year messing with props.

However, I am getting ready to run to NY in July so if this could improve my efficiency a bit more, I might be able to save enough fuel on a 700 mile round trip to pay for itself.

 

[HUMPH]

If the diver has not yet put my props back on I could ask him to measure for me.

 

[mistercomputerman]

That would be good if the diver could measure.

My question is going to be:

Is it better to buy the add-on tab plate for the existing tabs or to replace the tab altogether?

What is the difference in price?

 

[rondds]

Tom and I have had preliminary discussions about my old tub. I not obsessed enough that I would add an additional set of tabs. Increasing size of existing and adding the 3" drop fins is appetizing. BUT would that require adding additional trim cylinders to each larger tab?

Also, at what point do you give up on the tabs you have? ie: I could certainly apply more tab and drop my running angle, but I'm losing speed in the process. Would a larger tab do the job with less tab dropping? (does this question make sense?)

 

[Tabman]

A few notes:

The whole point is to get more surface area since it will need to be deflected less than a smaller Trim Tab to generate the same or more lift. It sounds counter intuitive, but larger Trim Tabs equal less drag. You will be able to hold the bow down with less Trim Tab deflection and that is way more efficient. On a straight inboard less bow angle also translates to less shaft angle and the props will be running at a more effective angle of attack. This also equates to less prop slip. Although the tunnels mitigate this a bit, it is still a factor.

We can use a single actuator up to a 42 x 12" Trim Tab with drop fins.

If I know the sizes of the Trim Tabs you want I can provide you with a list of all the parts needed and the "list prices". You can shop for them from a dealer like BOE and decide what will be the best choice for your situation.

But the overriding idea is to get as much surface area as you can for the best results.

Since properly installed Trim Tabs angle up from the bottom of the hull when they are fully retracted, your boat will still run the same with the larger Tabs up as it did with the smaller ones up.

Tom
Bennett Marine

 

[mistercomputerman]

Tom

HUMPH and I have the same tabs:

566059 TRIM TAB, ASSY 12X24 W/ZINC 400EC271452 TRIM TAB

If we just want the bolt on component, what is the part number for a set of those?

​

 

[Tabman]

The Drop Fin add on kit is part #DF12, with a list price of $29.00. It consists of 4 fins, enough to do 2 Trim Tabs.

Since your Trim Tabs have a small fin facing up on the inboard side and one facing down on the outboard side, you will need to bolt the inboard fin to the bottom of the Tab on the inboard side, either on top on the outboard side "overlapping" existing fin, or on the bottom of the Tab, pushed up against the inboard of the Tab.

I would suggest that adding the Drop Fins to the existing Trim Tabs will make a very small difference in the lift generated. It will be the least effective part of the other suggestions and the change will be hardly noticeable. The Drop Fins help, and their effect on smaller boats with smaller Tabs is noticeable since the additional lift is a larger percentage of the the total lift created by a small Trim Tab than it is of a larger Trim Tab.

The Drop Fins are included in my suggestions as part of a total approach to provide as much additional lift as possible. Adding larger outboard Tabs and additional inboard Tabs will have a far greater impact.

Here are a few pictures:

Tom
Bennett Marine

 

[mistercomputerman]

Thanks

So, all the other "bolt-on" larger tab photos we have seen are something someone fabricated for themself?

 

[HUMPH]

I was thinking the same thing. Are there tabs that I can bolt onto my existing or are there some larger ones to replace my existing that would bolt up to the existing ram?

 

[Tabman]

Some guys have made their own larger Trim Tabs or extensions that bolt or weld onto the existing Trim Tabs . And they have fabricated drop fins for them as well. Usually they make them bigger fore to aft, so that they may utilize the same hinge and not have to change the actuator location.

While there results have been very good I cannot help with that nor fully endorse it. This is because when the fore to aft measurement is increased it puts addition strain on the actuator. Whenever we make Trim Tabs with more than 12" chord we use two actuators to account for the addition stress. The stress of a longer chord on the actuator is the greatest when the boat is backed down hard. Water piles up on the Trim Tab and will force it downwards and can break the actuator, usually resulting in the loss of the Trim Tab. This is the reason that most sport fishing boats have 2 or more actuators per Trim Tab and also often employ a Retention Device to help support the Tabs when backing down hard on a fish.

It is worth noting that a Trim Tab that is longer side to side is more efficient than on that is longer fore to aft. This is because less water pressure is lost out the sides as compared to the amount of water flowing over the Trim Tab.

So when making your own extensions or Tabs I can't comment too much, and if other parts of the system, such as an actuator is damaged we can't really warranty it.

But looking at the results of these extensions is interesting!

Tom
Bennett Marine

 

[mistercomputerman]

Are there tabs that I can bolt onto my existing or are there some larger ones to replace my existing that would bolt up to the existing ram?

Did he say "No"?

 

[HUMPH]

Did he say "No"?

He did say no. He does recommend if we install larger tabs to add an additional actuator. I would be interested to see how much work it would be to add an actuator to each side?