trim tabs

G

Georgian Bay Cruiser

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exMember
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Jul 9, 2007
RO Number
27339
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I'm hoping someone here can answer this question. I understood from installing trim tabs on my last boat that they were to be placed very near the outside edge of the transom. So I'm curious why carver installed the tabs on my 28 mariner directly in line with the props. I don't think it's just my boat. There's a 28 voyager in our marina and they're in the eaxct same place on her. I've tried to include a picture, but can't seem to get it copied here. I will have to track down the instructions for that and post it here shortly.
Thanks, I'd appreciate any insights.
Terry
 
Here you go Georgian Bay Cruiser
IMG_1798.jpg
 
it may be because the hull is relatively flat and they don't need to be out at the edges...I'm not sure. On the 3257/3297, they are mounted in different locations, and they are the same hull.
 
I'm by far no expert and this is only MY opinion but I've always believed that you should get the biggest Tab that your boat cqan accomodate.
Those look to me to be quite small for the size boat you have. Just MY opinion though. I'm sure there will more knowledgable people chiming in shortly.
 
First, Ram, thank you for importing that picture. Perhaps you could send me a quick note as to how you did it. As for the tabs, I do wish they were larger. The 28 is quite butt heavy requiring signifcant use of the tabs, and while its a fairly flat hull, it's also relatively short, which seems to create a smaller planing surface. Not having the tabs at the outer corners doesnt seem to make much of a difference for balancing the boat side to side, as the 12' beam makes her pretty stable. But I did wonder if having the tabs directly behind the props would decrease the engine efficiency at all. In other words, does having the drag and lift the tabs create in line with the thrust from the props, decrease that thrust, or would it be the same no matter where the tabs were placed?
Terry
 
Hope you guys don't mind looking at photos.

I bought my boat used. Originally it had much smaller tabs, but the previous owner had larger tabs installed on the boat. He did not like the time to plane.

I am not sure what the plane time was prevously, but I can get on plane in about 3 seconds - or so it seems.

update3.jpg


I can also put the bow down, and improve the angle of attack to the waves.

You can see the length of the tabs easier in the left tab. They go up to about 3" from the boat sides.
 
Simple Engineering says the more surface area you have the more effect that a trim tab will have. So bigger is logically better for more results. I imagine travel angle also comes into play.

If the width is less, I am not sure whether inboard or outboard location makes more difference. Probably depends on the hull. My 3607 has smaller tabs, and they are mounted outboard. If I ever replace them, I will go for larger tabs like above.
 
GBC, in your photobucket pic, to the right there are 4 lines of info stacked on top of each other. Highlight the bottom one (starting with "img.") copy, and paste onto the message box here.
 
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