Trim Selection-Does size matter??

P

Peter_BDA

New member
Hi all, pretty much decided on Bennett M120 "Super Sport" trim tabs for my 22' Cruiser, but I see that there are similar models with different size tabs all around the same price.

Does (tab) size matter? What will work best for the 22'?

All advice welcome!!

Thanks
Peter
Bermuda

PS Yes, it is warmer here than where you are (probably). :tux
 
You have pretty much decided on the best choice. The M120 tabs might as well have been designed for the CD22.
 
"Does size matter?"
Click to expand...

The short answer is ALWAYS, I think.

I have Lenco tabs, and though they do work, I think they are smaller than what would be more efficient. think about it. they are there to provide lift to the stern of the boat. Water passing under the plate, lifts as it moves across the under surface of the tab. The larger the tab the more lift provided given the same speed of the boat. Also, the greater angle of deflection, the more lift. OK, so also, the greater the angle of deflection, the more drag. So, there is the rub. With a larger plate, the angle of deflection required to provide lift will be a less steep angle. And the larger the plate, the more lift for a slower speed.

As a side benefit, a larger plate might serve as an emergency boarding step when climbing into the boat from the stern.

That's my whole $0.02 on trim tab size :arrow: :?

Harvey
SleepyC :moon

SSC_CPR_and_Patient_005.thumb.jpg
 
You will never use 100% of what the M120s will do for the CD22 so they are big enough. And having 120% of what you need is much better than 80%. I think the trouble with the Lencos I have is that they have too little stroke. I believe if you think through all the geometry stuff you'll see that the size vs. angle question isn't that big of a factor. You gotta do what you gotta do so the cost will be the same according to the physics stuff.

Another plus with the Sport Tabs is the turned down edges. It really does help the slow speed tracking around the docks even though you wouldn't think such a simple thing could make a difference.
 
I have the Lenco's and they are a little small size wise and coupled with
the shorter stroke they fall short of the efficiency that the M120's offer.
I put wings on my Lenco's with turned down edges to give more surface
and channel the water. The increase in efficiency was very significant
and I'm very pleased with them now.
 
OK - I want to take back part of my comments, or at least qualify them by saying I am unqualified to do the geometry/physics analysis. I typed it on my phone at work and now it looks like I think I know what I am talking about.

The point I really want to make is that it should be illegal to put anything but Bennett M120 Sport Tabs on a C-Dory 22 hull. However, others will work just fine.
 
What?? With all the great tab choices you get suckered into these so easy?

Great choice! I put them on my CD22 and really, really wish I had put them on my CD25 instead of the larger Lencos.
 
I have not been able to find a travel length for the Bennett's anywhere on their web site. I did find that the lencos can be ordered in 2 1/4 or 4 1/2 inch travel lengths. So what is the length of the Bennett's.

I have had the lencos before and cant see any reason not to get them again. They are fast and easy to use. install is easier with out a hydraulic pump to find a place for, You can run the control cables outside the hull and not have to drill a hole in the hull to run the hydraulic lines thru.
 
Peter - You will find the customer service at Bennetts to be as good as it gets. Just be careful when you drill for your wiring and hydraulic line that you don't drill into the well (outside)l where the contour runs into the transom. You will have to remove your tanks and filler hoses - also based on your model year, your hoses may need replacing. John
 
starcrafttom":fivgmrk4 said:
I have not been able to find a travel length for the Bennett's anywhere on their web site. I did find that the lencos can be ordered in 2 1/4 or 4 1/2 inch travel lengths. So what is the length of the Bennett's.

I have had the lencos before and cant see any reason not to get them again. They are fast and easy to use. install is easier with out a hydraulic pump to find a place for, You can run the control cables outside the hull and not have to drill a hole in the hull to run the hydraulic lines thru.
Click to expand...

The standard stroke for Bennett actuators (rams) is 2-1/2". We do have many other length and stroke actuators to fit different installations.

The actuators that come as standard with the M120s are shorter than our other kits, making it easier to install them in limited spaces. The over all length of it is 11-1/2" with a 2-1/2" stroke. It can be modified to be 10-1/2" in length to fit in really tight spaces.

I hope this helps, I would be delighted to answer any other questions you may have .

Tom McGow
Bennett Marine
 
Tabman Tom thank you for the correct What other stroke lengths are available? James , your right that is good service and I like it, but it just confirms that I will need the lencos with more travel. My application is a little different. The base of my tabs will rest against the hull about a inch farther rear ward then the base of the ram where it connect to the hull. I would like to get wider tabs but because the shape of the aft hull I can only use 12 width, and with the kicker in the way I only have 9 inch's of depth. So I need as much movement as possible. I really need bigger tabs but don't have the room. I will lose some because of the difference in mounting surfaces so I need the longer ram movement. the length of the unit its self is not a concern.

so if the Bennett's only move 2 1/2 then thats not going to be enough.

its a ford chevy thing but the lencos served me well for 5 years on the 22. they are easier to install and the last thing I need to find a place for is a oil reserve and pump. my only complaint about the lencos was the size that was installed on the boat. I think they should have been bigger but I did not choose them. I have ran peters 22 and did think that his Bennett's provided more lift but when i looked at them later I saw that they were larger tabs then what my 22 came with. I believe that either one will work fine as long as you have the right size tabs.
 
Tom,

The maximum stroke is 3-1/2". It's important to note that the maximum amount of deflection you will want in a Trim Tab is about 20 degrees, any more than that and the amount of drag produced starts to offset any additional lift generated.

Do you have a photo of your transom and existing Trim Tabs I could look at? I'd be happy to see if I can offer any other options in order to get you more lift from them.

Tom
Bennett Marine
 
Tom,here's a link to a page of pictures of the boat. my c-dory has a aluminum off shore bracket on the back that is the width of the boat. On the outside edge is a standoff that the previous owner was going to mount the trim tabs, he never did. Its 3 or 4 inchs high and 12 inchs long. I can't go longer then that because the stern makes a slight 5 degree turn at that point.

You can see that the stand off is what makes the two mounting points ( the back edge of the tabs and the top of the actuator) uneven. this is why I know I will use some travel distance and want to have the most I can get. its always better to have more then you need and not use it then to come up short.
 
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