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What is this? blister mystery on rudder

2K views 13 replies 9 participants last post by  willyd 
#1 ·
I hauled my boat out on Monday after it had been in the water for three years. I was told by one of the men at the marina where the boat was kept when I bought it (in 2011) that they had worked on the rudder. When I hauled it, there were quarter-sized blisters all up and down the rudder, on both sides. I sliced into them and gouged them out, and it seems there's a skin consisting of several layers sheathing the rudder that has gotten water under it. This looks to me like layers of vari-colored bondo or something. Is this perhaps the original (Whitby) material, or something the local boatyard used to patch things a few years ago? Here's a photo or two:
 

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#5 ·
Do you know what "worked on the rudder" means? If that is only on one side, I suspect they peeled the skin back to rebuild the internal frame or drain water and you're seeing the fairing they used to reshape that side. Check for water intrusion. If none, it just needs to be reshaped again, then barrier coated several times and bottom painted.

Curious, in the three years she was in the water, you never dove or had a diver down to clean the bottom? Would have thought you would see this starting.
 
#6 ·
Thanks for all the replies. I noticed the blistering, but haven't had a chance to haul it until now. I'm wondering why they would have used something that was not waterproof. I'll be spending today getting this off and redoing it in epoxy. The yard wants me out by Friday...
 
#9 · (Edited)
A good possibility is that the original repair was 'rushed' when the rudder was initially barrier/epoxy coated ---- what you probably see at the exposed surface of the HUGE section that is 'flaking off'.
Probably what happened is that the yard, etc. did not remove the amine blush that normally comes to the surface of an epoxy barrier 'coating'; they didn't use HOT water and then scrub the 'blush' away; nor, did they adequately sand down with 60-80 grit paper into the new epoxy to provide 'tooth' to enhance the adhesion of the successive layers.
Another possibility could be also be that they attempted to 'hot coat' all the 'layers' together - Applying and not letting each layer fully cure before the application of the next component layer and then expecting each successive coat to bond with each other. Such 'hot-coating' sometimes works; sometimes it doesn't work with respect to adhesion of all the successive layers depending on how fast or how slow the intermediate layers take to 'cure' ..... and if there is generation of the normal amine blush from the preceding epoxy layer.

So, ...... If the surface of the this (barrier coat?) epoxy layer is still intact, not blistered nor cracked .... and the yard needs to immediately launch this boat ..... Id just 'slop on' some bottom paint and then later do a correct repair later-on when the boat is hauled.
However, If there is evidence of water intrusion into the rudder, then an immediate complete repair should be considered ..... BUT, if the rudder is water-logged, it will take some TIME for the rudder to dry out before you can do a proper repair.

IMO - slop on some bottom paint now; and, do a thorough repair job when you have the proper amount of available time to do so.
 
#10 ·
Drill a hole in the bottom and drain the water out of the rudder. If it's brown the foam is breaking down.

"No such thing as a dry rudder"

It peeled because it was not repaired done properly!
 
#11 ·
Thanks for the replies. I spent all morning down at the boat and came back at 2:00 when I got a headache from the heat (and finished getting on two coats of paint). I think I'll fill in the gouged out areas and maybe remove the rudder in the fall and work on it at home.
 
#12 ·
I've gotten an extra two days from the boatyard - it's not being put back into the water until Monday. From what I understand, if the layers of fairing material are blistering and can be pried up by sticking a scraper between them and the underlying substrate, I can expect the underlying (fiberglass from 1964) substrate to also contain water, which isn't something that's going to dry out in a day or two, even in the hot sun, correct?
 
#13 ·
Willy, if there is water intrusion, it will never dry. If you drill a hole in the bottom of the rudder, and another vent hole in the top, you can drain the majority of the water out in a day or two, however, the inner core will always remain wet. And, even though you do a great repair job, when winter comes, that moisture inside will ultimately freeze, expand and have some effect on your repair job. Eventually, you will likely have to remove the rudder, open it up and air dry it for several weeks before reassembling and reinstalling.

Good Luck,

Gary :cool:
 
#14 ·
Well, for what it's worth, I gouged out all the blisters and "skin" that I could get off with a scraper, let that dry for as much as I could, cleaned it with acetone a few times, then filled it with polyester filler (polyester resin + microballoons + fumed silica), then a top layer of epoxy plus the two thickening agents. We'll see how long it lasts.

 
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