Anodes on Trim Tabs - Silly Questions?

[rgsmg53]

I've currently got my boat out of the water - first time for this boat in my ownership.

I'm doing all the usual stuff such as anodes, anti-fouling, etc and I was just about to replace the trim tab anodes. There is one anode per trim tab and they are on the upper side of each tab and bolted through the tabs themselves. So, here are the silly questions:

1. Is having anodes on the upper sides only the right thing to do or should there really be anode material on both upper and lower surfaces? I'm conscious that with the tabs "up" (most of the time on the berth) the lower trim tab has no line of sight to the hull anodes.

2. As neither of the trim tab anodes are bonded electrically to anything else, should the anodes be in direct contact with the trim tabs or should they be fitted with the normal insulating pads underneath.

What do you experts out there think?

 

[rafiki_]

Mine are on the upper side. On the lower side I think they would have more of a negative impact on the hydrodynamics. I also use the isolation pads. They do not need connection to the hull anodes.

 

[Plum]

I've currently got my boat out of the water - first time for this boat in my ownership.

I'm doing all the usual stuff such as anodes, anti-fouling, etc and I was just about to replace the trim tab anodes. There is one anode per trim tab and they are on the upper side of each tab and bolted through the tabs themselves. So, here are the silly questions:

1. Is having anodes on the upper sides only the right thing to do or should there really be anode material on both upper and lower surfaces? I'm conscious that with the tabs "up" (most of the time on the berth) the lower trim tab has no line of sight to the hull anodes.

2. As neither of the trim tab anodes are bonded electrically to anything else, should the anodes be in direct contact with the trim tabs or should they be fitted with the normal insulating pads underneath.

What do you experts out there think?

The anodes should be fitted to the top surface only and the central bolt must make an electrical connection between the steel core plate of the anode and the stainless steel of the trim tab (no paint!). In many cases when you put the round anode on a flat surface there is a gap between the core plate and that surface. The insulating pad seals the underside of the zinc part of the anode against the trimtab which stops the underside of the anode wasting away which in some cases can lead to the central bolt coming loose resulting in an ineffective anode. If you do not fit the insulating pad you must ensure the steel core plate is clamped direct to the trimtab by inserting a metal spacer on the bolt between the core plate and the trimtab.

Www.solocoastalsailing.co.uk

 

[rgsmg53]

Thanks to both. It looks like the previous owner had failed to ensure connectivity between the tabs and the anode bolts.