Anode on top and bottom of tab?

[aquaaddiction]

Hi,

My new to me 280 Sundancer has anodes fitted to the tabs, but it has them both top and bottom, I would have thought that the bottom of the tab should be as flat as possible for minimium drag and maximium effect, or maybe a profiled anode is better on the bottom that a bolt head?

Here is a pic side on, its hard to see but the anode on the bottom is exactly the same as the one on the top:

20121025_182509.jpg

Shall I put them back that way or just the one on the top with just the bolt head protruding below?

Thanks,

Anthony

[Tabman]

Anthony,

You are correct about keeping the bottom of the Trim Tab flat. At the factory we install the zinc on the top of the Trim Tab only. The pan or roundhead on the bottom creates minimal drag. So I would suggest you do the same with the half of an R-3 zinc on the tops only.

Tom
Bennett Marine

[kilroy]

When I ordered new anodes from Boatzincs.com for the trim tabs on my 260, they sent me ones that are similar to what you have in your pic. The old ones were just on the top of the trim tab but the new ones actually screw together with the tab pinched between. I re-checked my order and those are the only ones that seemed to be available.

Hi,

My new to me 280 Sundancer has anodes fitted to the tabs, but it has them both top and bottom, I would have thought that the bottom of the tab should be as flat as possible for minimium drag and maximium effect, or maybe a profiled anode is better on the bottom that a bolt head?

Here is a pic side on, its hard to see but the anode on the bottom is exactly the same as the one on the top:

20121025_182509.jpg

Shall I put them back that way or just the one on the top with just the bolt head protruding below?

Thanks,

Anthony

[Tabman]

Kilroy,

Yes they do come that way, each unit has two halves. You only need to buy one unit and use a half on the top of each Trim Tab. You simply bolt them to the Trim Tabs using 1/4 x 20 machine screws and nuts.

Tom
Bennett Marine

[kilroy]

Thanks. I haven't installed mine yet, so that's what I'll do.

[Henry Boyd]

Anthony,

Dude, dont be silly.

A. A 280 barely needs tab adjustment anyway. We hardly have to use ours.
B. The corrosion protection far exceeds any drag inefficiency
C. If I remember my fluid dynamics correctly, a point source (e.g. bolt head) will create greater drag than a smooth curve.

Let's get Gary for this one, he's the fluid dynamics expert.

Henry

[Woody]

Mine came with halves on top and bottom. I figured someone smarter than me felt they were necessary for protection so that's what I put on.

[Tabman]

For what it's worth SeaRay and just about every other boat builder specifies 1/2 of an R-3 mounted on the top of the Trim Tab. We have found that on Trim Tabs up to about the size of a 42" x 12" that this is sufficient protection. Larger than that we use R-4s or even larger "hockey puck" anodes. Additionally the waterflow over a an anode mounted on the bottom of the Trim Tab will erode them faster than the one on top. Our recommendations are based on 60 years of manufacturing over one million Trim Tab systems.

Tom
Bennett Marine

[aquaaddiction]

Thanks for the replies, if one on top works for most people then it's good enough for me; can't get better than advice from the people that designed it thsnk's Tom.

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