That rudder is foam cored (or was when it left the factory) I think you'll find that filling it with ethylene glycol will dissolve the foam and destroy the rudder

Then my rudder should have been destroyed by now. Ethylene Glycol has had no discernable effect on the foam in the rudder of my O'day, other than keeping the water from freezing and the rudder from delaminating, after two years.

[EDIT] adding a picture

Attached Thumbnails

 

Don't know how you are getting away with it. No production builder I know of uses epoxy foam which would be resistant to the EG, it's pretty simple chemistry.

Was your rudder rebuilt using epoxy foam ?

Perhaps you could elaborate on the simple chemistry involved... My knowledge is limited to what I have researched at the Foss Foam website, and my experience.

Quoting from the Foss Foam website; Rudder Care | NewRudders.com

Further; Ethylene Glycol - Boiling, Water, Car, and Carbon - JRank Articles

Your first reference is kind of curious in that it says solvents will not harm the "rudder blade". It make no reference to the foam.

Your second reference clearly states that ethylene glycol is a solvent !

Suggest you try another search "polyurethane foam dissolve ethylene glycol"

I had hoped that with your background as a marine surveyor that you could reply by educating us on the "simple chemistry" - rather than directing us to conduct a fruitless google search. For the benefit of others; here is that search, and I'll save other readers the trouble; it provides nothing that supports @boatpoker 's assertion;

Boatpoker, you need to read ALL the words that I cited from Foss Foam. Here, I'll help make it more obvious for you: "The urethane core is composed of a strong closed cell urethane. Water, gasoline/diesel, solvents or marine borers will not damage [the urethane core of] your rudder blade, even if the fiberglass coating has been damaged." So, Foss is claiming that solvents will not damage the urethane core. Clear enough?

Regarding my second reference, I concede that EG is a solvent (some of us recall from high school that water is frequently called the "universal solvent"), but again reading ALL THE WORDS, it states that EG is "a starting material in the production of urethane foam."

How do you get the siphon tube to the bottom of the rudder?

I have about 10-feet of 3/8" OD clear vinyl tube from the local big box store (about $3). I am not 100% sure of the length, but you could simply measure from the cockpit to the bottom of the rudder, multiply that by 2, and then add the length necessary to go from the rudder post to the cockpit coaming. Add a couple of more feet if unsure.

I feed/drop the tube all the way to the bottom of the rudder post, and over the coaming, and toward the ground. While standing on the ground I apply a vacuum to the end (I have also used the faucet to push water through the hose, and into the rudder) to get the siphon started. Then I wash out my mouth with clear water (not necessary if I used the faucet).



In the past, I have drained over a gallon.

I did not bother to siphon the rudder post out this year (I may still change my mind), as I noticed that the rudder was full of antifreeze.

Guess what they use to clean up Polyurethane guns .......
Produced by:
Professional and Specialized Services
in consultation with the Construction
Health and Safety Program,
Ministry of Labour
Alert #C11/0196
ISSN 1195-5228


HAZARD SUMMARY

BACKGROUND:

Polyurethane foam is being used more and more as an insulation
material in residential construction. Recent experience
indicates that some contractors may not be providing workers who
handle it with adequate respiratory protection or training in
proper work and hygiene practices.

Polyurethane foam is usually prepared on site in a closed system.
The following materials are mixed in a 1:1 ratio:

- base resin, comprising polyols, amines (often tertiary
amines) to act as catalyst and plasticizers; and

- isocyanate (both monomeric and polymeric), usually
methylene bisphenyl isocyanate (MDI).

Normally, two workers are involved in spraying the foam: a
sprayer and a helper who cuts off excess foam and cleans it up.

To clean the spray gun, the workers use an organic solvent such
as glycol ether (ethylene glycol monoethyl ether).

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.