A solution to permeated tubes

[Jose Venegas]

What are we missing?

Peggie, I am not "defending" against your criticisms. I am just trying to figure out if the solution proposed, as your "expert" friend suggests, truly exposes my boat to increased corrosion risks. So far, I don’t see any validity in your statements. It would be very useful if instead of reporting incomplete and physically erroneous statements, you were to ask your EXPERTS to explain the rationale and physics behind their comments. The only CONSTITUTIONAL right here is the right to seek the truth. Debating is one way to get to it. Anything else is a waist of time.

 

[Tom]

No Peggy....I love the information I have learned

from you on here. Nothing wrong with that. And I fully understand where your sources were coming from, I think they might have misinterpreted what Jose was actually doing . In general, their advise is not unwarranted. All it would take is some numbnut wrapping everything in their boat in 'metal' and "Bad things" *could* possibly start to happen. So I think in their minds its easier to say "Don't do it !" then lay all the caveats on where it might be ok (easier to be safe than sorry)Have them re-read the actual parameters of the Jose's "modification" and then have them read what I wrote and then ask them to comment.

 

[John Visser]

Where are the experts anyway?

If they can read the thread, why can't they respond directly?

 

[Peggie Hall/Head Mistress]

How can you be 100% certain

that aluminum "clad" hoses passing behind bulkheads, through all kinds of tight places, or just laying against the hull doesn't contact ANYthing metal? Even a staple can do it.You say EASIER to be safe than sorry...IMO, BETTER to be safe than sorry a year from now 10 miles offshore in a blow. And with that, I'm bowing out of this discussion. I've contributed all I have to contribute.

 

[Steve Dion]

I can't believe that this is still going on.

Dis-similar metals come in contact with each other all the time on all boats. You have stainless steel screws in aluminum masts, booms, spreaders etc. You have a stainless steel shaft stuck into a cast iron or steel hub on your tranmission and a bronze prop stuck on the other end. You strut is fastened to the hull with stainless steel bolts. There are no merits to these arguments. So if a staple comes in contact with some aluminum tape, so be it.Tape it and save yourself a couple of years of cost and labor. Eventually you will need to replace the hose but if you can do it 2,3 or 5 years later all the better. Maybe these guys that make this hose will find a way to make it fit on the fittings on the boat better and more flexible too in years from now.

 

[Chris Gonzales]

Well put, Steve

You hit it right on the nose. In recent posts there was a thread about black pipe used for exhaust coupled to a brass fitting. Now there you would have dis-similar metals and an eventual breakdown in the installation yet no one commented on it. In this case there would be considerable trouble compared to some aluminum tape wrapped around a hose or a little staple. Why is this such a charged up discussion? I guess because Peggie does a great job (on purpose or accident) keeping things "interesting". Actually, I like Peggie (as much as I can from here, anyway) she has a lot of personality and desire and makes for interesting reading. I know she will always respond to my posts and everyones elses and I always look for that. On the other hand, I feel she is often dogmatic, even off-putting and would benefit herself by doing what most of us do when we log onto this web site and forum. Learn from others.

 

[Ralph Johnstone]

The Most Overlooked Item ................

........... in this entire discussion can be found in Jose's post entitled "Saran Wrap Didn't Work for Me" where he states ........ "I point out to our guests that my wife has forbidden peeing in the standing position on our head (and at home too!!)" Now, if this isn't a violation of one's constitutional rights, when a man is forbidden from making the usual overspray in his own boat (castle), I don't know what is.Regards,s/v Island Hunter

 

[Chris Gonzales]

hehe

The problem is standing on the head! You (men in this case) would miss entirely (wrong angle) PLUS the lid would be closed ( to facilitate standing on)! No wonder the Mrs. forbade it. One should be standing near not on, no? What do YOU think, Peggie? hehe

 

[Rick D]

Certainly an interesting discussion, but...

..when it comes time to change hoses on my 40.5, and dedicate the time to pull them through all the inner liner, and replace the aluminum tank too, I'll replace the hose rather than wrap. And, not withstanding the seemingly good performance of the black sanitation hose now on board, the test by PS was pretty convincing in favor of Sealand's. So, my time is worth the money for new Sealand hoses, a poly tank, and if it won't fit, a really thick aluminum replacement. With plenty of ventilation. Peggie's comments and concerns are well taken and Jose has the experience and credentials to effect a reasonable test. So... we all come out winners, IMHO. Good discussion. Rick D.

 

[Peggie Hall/Head Mistress]

Guys...think a bit

Steve says, "You have stainless steel screws in aluminum masts, booms, spreaders etc. You have a stainless steel shaft stuck into a cast iron or steel hub on your tranmission and a bronze prop stuck on the other end. You strut is fastened to the hull with stainless steel bolts..."And all dissimilar metals are--or should be--isolated from each other with bedding compound, rubber gaskets etc. When they're not, we see another thread about disappearing zincs and other related problems.Additionally (and what is missing from Jose's expertise as a medical engineer), a boat is a VERY damp environment...sometimes downright wet through and through...and salt water is a great conductor. Think about it...

 

[Jose Venegas]

Peggie, does not get it.

With all my admiration for your expertise in sanitation systems and the great job you have done in this forum, it seems to me you are not getting it as far as galvanic corrosion. If you read again Tom's posting, you will realize that even if stray salt water or urine connected the aluminum foil to other metals in the boat, it would be the aluminum the one to disappear by corrosion, NOT the other more noble metals.And Ralph, I am glad you have been able to maintain the standing posture for evacuating your bladder in your boat. In my case, this was a battle I fought very hard at home and lost several years ago. See, Ralph, women cant understand that in some conditions, streams can become separated into more than one direction, and it becomes virtually impossible to maintain the good aim of younger times. Given the continuous grief this point brought to my life, I decided it was not worth the fight and move my battle to other more productive areas such as sailing at healing angles greater than 10 degrees.No hard fillings Peggie, this is just done for fun. On the side, before I got my Ph.D. in Medical Engineering, I had a M.Sc. in Mechanical Engineering and a few physics courses. Believe it or not, galvanic corrosion may occur at the mouth when two different metals (Silver and stainless steel) used in dentistry may be in contact with saliva. The results, as you point out, may be disastrous if you are in the middle of a nice dinner date when your teeth begin to fall apart.

 

[Tom]

OK....One more time....Aluminum touching ANY metal

will PROTECT that metal from galvanic corrosion. Basically the only metals that will not be protected by contact with aluminum is magnesium, zinc and cadmium (?) Obviuosly there are many factors involved. For instance the severity of corrosion relies on (a) the voltage differences of the two metals on the Galvanic scale and (b) the size of the exposed area of Cathodic material relative to the Anodic material. An example is that an aluminum rivet in a big piece of Stainless Steel will corrode much faster than a stainless steel rivet in a large piece of Aluminum).(Reference --> http://nsgl.gso.uri.edu/delu/delug93003.pdf )So YES, I have researched this a lot and I have thought about this quite a bit.So, It comes down to this ---Its like putting zincs on every piece of metal. And yes that aluminum touching that staple will protect that (mild steel?) staple (stupidly) put on the boat from galvanic corrosion. (doesn't mean it still won't rust though, which is different....)Let me end this by quoting some more information from the Univ. Of Delaware Sea Grant Marine Advisory Services. (See link below for complete discussion)QUOTE FROM ABOVE DOCUMENT "Finally, let's see how we can use galvanic effects to our advantage in preventing corrosion. Suppose the steel member of a structure is being damaged by contact with silicon bronze. That galvanic corrosion can be stopped by connecting both metals to a third metal more anodic than either of them. According to our Galvanic Series, the third metal in this case could be magnesium, zinc, aluminum, or cadmium. !!!!! ......................... The same principle can be used to protect steel in marine atmospheres if the anodic metal is applied to the steel as a coating. Zinc (called galvanizing) and aluminum coatings are used extensively to protect steel in marine atmospheres. !!!!!!!!! "(NOTE - I added the exclamation points)ps. And I suspect that some of the reasons that hose manufactures wouldn't put aluminum tape on these hoses is that it would a) likely be too costly, b) wouldn't hold up well in installations and its mechanical properties are lousy and c) (AND I THINK THE MOST LIKELY REASON) Is that Aluminum would tend to deteriorate rapidly in a marine environment and render itself useless..... (and how many boaters want to pay big bucks for something that would potentially disintegrate quickly).Respectfully,Tom

 

[Jose Venegas]

Wao, Tom....

Should I extend the tape to touch the through hole hardware? In the worst case replacing a bit of tape every year sure beats having to change the hardware!!!As you point out, aside from the extra cost, I agree that incorporating aluminum into, or around, the tubes during manufacture would make them quite stiff and brittle. The good thing about the tape is that it is wrapped in place and molded to the final tube shape. A limitation of the method, however, is that it requires access to wrap the tape around the tubes. If one has tube sections behind bulkheads or areas that can not be reached, wrapping the tape would require dismounting of the tube, defeating the purpose of the approach.

 

[Tom]

Jose, to your question No.....not necesarily

I wouldn't "extend the tape to touch the through hole hardware". Your real aim here is to reduce the smell from the permeated hoses, not protect the through hull hardware.

 

[Jose Venegas]

I was kidding

I was kidding Tom… it is clear that for aluminum foil to have any protective effect it would have to be in direct contact with salt water. In any case, there is only one through hull (the one to dump to sea) that is close to an aluminum covered tube. The side effect that you describe does not sound too bad any way.Thanks for your input and research on the topic.