Plagued with bottom paint/dissimilar metals/halo effect problems again

Howdy Commanders. I’ve pulled my little gal out to have her trim tabs repaired. In the years I’ve owned her they have never worked. It wasn’t a priority for me because I didn’t know better. Upon some good advice from my mechanic and reading the posts here-it turns out they may be life-changing. And I’m all about that.....

Upon haul I’ve discovered a bit of a mess around the stern that appears to be part of an ongoing bottom paint/copper/dissimilar metals issue para mi. Parts one and two via this post from 2013
http://commanderclub.com/m/discussion?id=5203879%3ATopic%3A19010

Photo of her pitiful stern attached below. Seems to be a dissimilar metal issue. Again. I’m unsure what these tabs are made of  

Has anyone experienced this with the glas being affected?  It has a “welt” feel to it. I haven’t gotten into it yet and don’t want to make a wrong first move. Obviously it’s time for bottom paint again too. Oh how I dread it....

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The cylinders appear to be levelor http://insta-trim.com/ which is near me I have been in their shop for service and it was in and out with good conversation.  Give them a call telling them what you can about the system.  While it is out make sure the fluid is full see what functions and what doesn't, probably the cylinders, if so they will tell you to send them in for rebuild.  New hoses and rebuilt cylinders and you will be in good shape.

The nasty looking area around the tabs, is that after power washing or not?  If after, it may be blistering, grind, fill and paint.  Don't be discouraged these are robust hulls and those of us that are in year around learn to deal with this.  Those in the 4 month world would find this daunting.

keep the faith, Tim

Thanks for the thoughtful reply, as always Tim 

The photo shows the boat as she came out of the water and was just rinsed lightly with fresh water. Once I saw this I didn’t want them to power wash as I was afraid all of this would peel off. It feels a little more solid than that- but too thick to be just the paint affected. Unfortunately. 

And thanks for the encouragement.  A labor of love to be sure. I also did new canvas and reupholstered the V berth this year (with like-colored aqua Sunbrella)

I’ll try to get some photos. The canvas in particular turned out beautifully. 

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Beautiful, shows what you first stated as what you were looking for in a Commander and what it could become when you first entered this forum.  Bang on the transom, get the blister open if it is indeed a blister, the yard should be able to dry, fill, repair any damage.  Check your friends notices I listed my phone#, remember I am a geezer and 3 hours before you~mid-night now.

From the picture looks like "scaling" which is common in ferrous based corrosion but I personally haven't seen this in the non-ferrous metals common in marine antifouling paints. The location of the discoloration seems to scream electron exchange from the stainless trim tab plates but that is NOT able to be determined without knowing more like was there current flow occuring.The source of any electrolysis is the big question if that is in fact the root cause. Of course, that can come from your boat, a neighboring boat, the marina as you've investigated in the past. Dissimilar metals also is a separate topic that occurs faster when metals are bathed in an electrolyte. I'd doubt that this is blistering in the fiberglass but easy to determine with a scraper. As Tim said, a genuine blister is able to be drained, ground, filled and repaired by most yards or others without too much difficulty. It's very rare in older commanders from what I've seen and more common on those that were built in late 70's and 80's where they suffered from some inferior gelcoat materials as many OEM's used during that time. I know it's frustrating but you have a very solid hull there. Greg

   Looks like the SS trim tabs have an issue . The zinc on the tab looks like it is not functioning while the plate zinc is normal . Is the button zinc making good contact with the Trim Tab ? Stainless can be a problem depending on the alloy as there is many and quality ,welding,work hardening ,crevice corrosion etc. but your tabs dont appear pitted so something is protecting them ,probably the plate zinc {assume it is Zinc ,not Aluminum } ! Why bother with copper paint when alternatives are available and probably cheaper . You might break the bonding system into two sections after one haulout to better locate the problem If it was me I would put an epoxy barrier coat on the stainless tabs to slow down any electrolytic action  What you could also do is paint just the transom with a non-copper paint,I have done this often with outdrive boats .

Missy, it occurs to me that my tabs and most others I have seen are fastened to a teak spacer between the hull and the plate.  Yours seem to be fastened to the transom.  The teak spacer does two things, it adjusts for any curvature of the transom and it also isolates the plate from the hull.  It could be this minor factor is causing the problem with the bottom paint.

Tim

If it is electrolysis--I agree the source needs investigating. Often from dock wiring issues leaking into surrounding water. However I placed two quicksilver galvonic isolators on my main grounds (one for each of my 110V 30amp incoming from dock) on my boat as a safety measure. I am in brackish water and they seem to work very well. They are VERY easy to install and a guy on ebay sells them new/very reasonable. I have known others to use them with good success as well. 

HI Robert and thanks for the response. The diver just dove the boat and replaced those zincs about a week before I hauled her out. Good eye though!

robert mikes said:

   Looks like the SS trim tabs have an issue . The zinc on the tab looks like it is not functioning while the plate zinc is normal . Is the button zinc making good contact with the Trim Tab ? Stainless can be a problem depending on the alloy as there is many and quality ,welding,work hardening ,crevice corrosion etc. but your tabs dont appear pitted so something is protecting them ,probably the plate zinc {assume it is Zinc ,not Aluminum } ! Why bother with copper paint when alternatives are available and probably cheaper . You might break the bonding system into two sections after one haulout to better locate the problem If it was me I would put an epoxy barrier coat on the stainless tabs to slow down any electrolytic action  What you could also do is paint just the transom with a non-copper paint,I have done this often with outdrive boats .

Tim:

OH!  I have passed this on and we will investigate this.  I wonder if everyone's tabs have something holding them off from the gel coat?  Brilliant. It would make sense all the way around.

I tried to find your phone number today in my inbox etc on this site, but couldn't find it.

Timothy "Tim" Miller said:

Missy, it occurs to me that my tabs and most others I have seen are fastened to a teak spacer between the hull and the plate.  Yours seem to be fastened to the transom.  The teak spacer does two things, it adjusts for any curvature of the transom and it also isolates the plate from the hull.  It could be this minor factor is causing the problem with the bottom paint.

Tim

There is a piece of wood at both of my trim tabs (1968 CC Commander) spacing them about an 1" or so away from the fiberglass.

I have wood blocks between my tabs and the hull on my 27.

 Missy most of the wood shims on trim tabs are to increase the effectiveness of the trim tabs and there is no reason to isolate them from non conductive fiberglass. Here in South Florida we can not use wood as the marine organisms in the salt water would eat the wood  fairly fast .You need to quit painting the SS tabs with metallic bottom paint ! The best way would be to put a good marine barrier coat for metals on the SS plates and paint them with a NON-Metallic bottom paint and your problem will go away ! Bob

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