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post #20 of Old 10-24-2017
Learning the HARD way...
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Re: Large Blister on Oday 31 Rudder

I am still waiting on @boatpoker 's "simple chemistry" explanation... (Do you know? or are you just "googling" to defend a position that you have taken.)

I am open to the fact that it may be inappropriate to recommend pouring EG into a rudder post. I am not a chemist. It is becoming clear that boatpoker is not a chemist either. I suspect that someone reading this thread may be, and hope that they will help settle this. To really answer the question, we would need to know exactly what kind of "urethane foam" (there are several) is used by Foss Foam as core in their rudders, and we would also need to qualify the type of Ethelyene Glycol (there are several of these too) in the antifreeze that I used.

However, these are FACTS:
  • Foss Foam states that their foam is not subject to damage from solvents.
  • I understand that Glycol is used as an ingredient to some urethane foams.
  • In the two years that my rudder has been exposed to it, I have not seen any indication of damage from the Ethelyene Glycol based antifreeze that was poured into my rudder post of my '87 O'day.

I do not recommend drilling a hole in one's rudder to let water out. [this is REALLY the last time I will say this, as I am unsubscribing from this thread] In fact, I advise against doing so because I believe that will assure water intrusion into the rudder, and lead to further delamination. Funny, but if I recall correctly, my surveyor suggested that I drill a hole in my rudder - eight years ago. I ignored him.

Getting back on topic, it seems that I was correct in my suspicion that the "bubble" was, in fact, in the antifouling paint. That said, I suspect that the rudder was improperly prepared for painting.

The next time that I need to clean a Polyurethane Foam Spray Insulation gun, I will heed bp's advice and use glycol ether.

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USCG Licensed OUPV Captain, ASA 101/103/104/105/106/114/118 Instructor - Also certified in Marine Electrical Systems

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