Drop Fins - Do They Work?

Thanks, David. How difficult was it to remove and replace the tabs? Why did you add the 2" up-turned edge at the rear? Wouldn't that add drag? And if you don't mind my asking, how much did the welding shop charge to make the new tabs and weld them on?
 
Thanks, David. How difficult was it to remove and replace the tabs? Why did you add the 2" up-turned edge at the rear? Wouldn't that add drag? And if you don't mind my asking, how much did the welding shop charge to make the new tabs and weld them on?

Very easy to remove actually. Remove the actuator from the tab. Let the rest remain in place. If you look on the piece attached to the transom, where the hinge is formed, there is a small piece of metal turned over the edge of the tab that holds the tab portion in place. Mine was to the outboard edge. Depending on how your screen displays the picture below, it may be visible in the picture. Bend that tab down with a pair of pliers and slide the tab out.



Bennett_Trim_Tabs_TPAM120_46695XL_2.jpg

The 2" turn up at the rear was to add stiffness to the span.
I want to say the build and weld was $375 total. It paid for itself in fuel savings the first year.
 
Thanks, David! Looking at the tabs on my boat, it looks as though any extension will need to be toward the centerline, because the outer edges are already just under the edge of the swim platform. This is perhaps a question more for Tom, but will adding about 50% of the width to the inboard sides (so the actuator is off-center on the tab) work properly? Would that damage the tab system?
 
I only added length to my tabs, not width. I needed the most cost effective and least invasive means of fixing a problem. This was the way for me.
 
I cannot recommend having an actuator that far off centerline. Adding span, (side to side measurement) is a bit more effective than adding chord (fore to aft measurement). But the hinge must run the entire length and the actuator should be centered. Or you could add a second actuator to the Tab.

Tom
Bennett Marine
 
Thanks for all the help! I hadn't considered the hinge. My tabs are 10" fore-to-aft and 11" wide, so it sounds like I would be best off adding length rather than width.
 
Jeff, are you sure everything is functioning correctly and you're getting full deployment? The reason I ask is that I have the exact same boat/engine as you and I barely ever even have to use the tabs. When I do use them, they are very effective and there is very noticeable difference between using them and not using them. My boat is always loaded with lots of gear, so it's not as if I'm running light, either. I can even pull up a slalom skier with ease. I'm not saying it's bad to go with bigger tabs, but I'm offering this suggestion as maybe there's something else going on and you don't really need to do anything.

IF you did decide to do something - you'd get MUCH more of a benefit by going to a wider tab and moving the actuator to keep it centered with the new tab. There's room in the boat to do this without much hassle - not that hard of a job.
 
Dennis, I use the tabs a lot to keep the boat level while cruising, and have had to use them to get on plane when I have more than three or four people aboard. I definitely can't pull a skier. I wonder why there's such a difference in performance between our boats. We keep the boat in a boatel, so bottom growth isn't a factor. The "celery stick" is set for max down-angle. We do have quite a bit of "stuff" on board, and we have a generator -- maybe that's it.
 
Dennis, I use the tabs a lot to keep the boat level while cruising, and have had to use them to get on plane when I have more than three or four people aboard. I definitely can't pull a skier. I wonder why there's such a difference in performance between our boats. We keep the boat in a boatel, so bottom growth isn't a factor. The "celery stick" is set for max down-angle. We do have quite a bit of "stuff" on board, and we have a generator -- maybe that's it.

Hmmm. I don't know why the difference. I do use them to keep the boat level on plane, depending on conditions and where people are sitting, of course. Even with that, though, I don't need a lot of tab input. But as far as hole shot goes, even with 3 or 4 adults and a couple kids, it pops up pretty quick. Granted it's no sport boat, but it does really well. I don't have a gennie, but I do store some things in the bilge. The stuff won't equate to the weight of a gennie, but I don't think it's going to make too much of a difference.

What prop pitch (and drive ratio if you know it) do you have and what's the max RPM you can achieve?

Maybe we should PM so we don't hijack too much?
 
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Hmmm. I don't why the difference. I do use them to keep the boat level on plane, depending on conditions and where people are sitting, of course. Even with that, though, I don't need a lot of tab input. But as far as hole shot goes, even with 3 or 4 adults and a couple kids, it pops up pretty quick. Granted it's no sport boat, but it does really well. I don't have a gennie, but I do store some things in the bilge. The stuff won't equate to the weight of a gennie, but I don't think it's going to make too much of a difference.

What prop pitch (and drive ratio if you know it) do you have and what's the max RPM you can achieve?

Maybe we should PM so we don't hijack too much?

Good point...PM Sent!

Is it just me or does anyone else feel like they've been left at the prom?:huh:
 
If you really want to hear about the junk we carry and the issues I've had getting on plane, we can bring the discussion back here. Just trying to limit the hijacking of the thread!
 
If you want to talk about each others junk, that's between you two! :grin::smt100:grin:

But others may have the same boat and be experiencing the same problems you are. The prop pitch comment really piqued my interest.
 
Yes they work, but its not a dramatic difference. I just added drop fins on my 300DA that has 12" long by 18" wide tabs. I took notes on the speeds and planning at different RPM's on the way to the haul out, and then on the way back to my slip after the installation so I had a good comparison. I had about half fuel. Prior to installation I could just barely get on plane at 3400 RPM and 21 Knots. After, I could get on plane at 3200 RPM and 18 knots. At 3400 RPM it was comfortably flat. At higher RPM, I could start trimming back and stay flat. Before, I always needed full down tabs. Well worth the cost.
 
Yes they work, but its not a dramatic difference. I just added drop fins on my 300DA that has 12" long by 18" wide tabs. I took notes on the speeds and planning at different RPM's on the way to the haul out, and then on the way back to my slip after the installation so I had a good comparison. I had about half fuel. Prior to installation I could just barely get on plane at 3400 RPM and 21 Knots. After, I could get on plane at 3200 RPM and 18 knots. At 3400 RPM it was comfortably flat. At higher RPM, I could start trimming back and stay flat. Before, I always needed full down tabs. Well worth the cost.

Sorry haven't updated this post in a while, especially since I started it.

I've been running season with the drop fins and we've noticed a pretty fair improvement. The way I look at it, they were an inexpensive investment that have made a difference. I don't have metrics however, they really seem to work.

We definitely pop up on plane faster than we've done in the past. Anyone with planing problems should consider it.

-Rocco-
 

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