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Old 27-10-2013, 15:06   #1
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I just purchased an a vessel built on professionally modified Ingrid 38 plans. I bought it knowing full well what I was getting into, so I thought. I am in no way disappointed with the vessel, however; after doing some research, I learned why they chose to call her a composite/steel hull rather than ferro cement. The matter of concern here is she was laid up with stainless mesh instead of galvanized. Now, at first response I thought that was a great idea. Until I remembered a job I did way back when making steps for a house for a nearby farmer. You see, when I went to his tool shed to retrieve the cement mixer, I noticed there had been a quite a bit of mix not cleaned from the drum. I questioned him but he wasn't concerned, he said that's why he built the mixer drum from stainless. He had build an new maple syrup operation, and had a lot of left over SS from building the evaporator. anyway, So when I started chipping away It all came free very easy, some even just by hand. There was almost no adhesion what so ever.... Can someone with more experience give me more technical input on how this will effect the overall integrity of the hull, perhaps the hull is fine as all the stainless is completely encapsulated, or perhaps the whole thing is one big wave away from completely disintegrating. From my understanding of stainless, it will oxidize instantaneously upon contact with oxygen or seawater so there is now way no remove the film in time to adhere the cement to it. Also, the large grid rebar I will assume is mild steel. Will this not cause electrolysis due to dissimilar metal properties in the presence of moisture... I do know this was a professional well planned build by engineers, but I also know that some engineers are brighter lit bulbs than others... Many times I has revised other engineers ideal of ergonomic, or structural integrity... I'd like to see a lot of varied input here pros/cons/concerns, I will analytically consider you take on this and not criticize anybody's brainstorming...
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Old 27-10-2013, 15:11   #2
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Worst case I will reconstruct her again from ferro to the same lines exactly again as FC, and use the hull as template. I am quite certain this is as near to perfect a world cruiser as one can build, save for the potential erroneous choice in mesh...
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Old 27-10-2013, 15:23   #3
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Re: Uh oh! Composite concrete stainless hull.

I don't have any expertise or knowledge on these types of builds, but I picture the mesh web as equivalent to glass fibers in fiberglass. In other words, adhesion isn't the main point of it - the combination of the strength of the mesh with the properties of the matrix is the goal. Are ferro boats really that wet inside the concrete? If so, it seems like mild steel would rot quickly.

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Old 27-10-2013, 15:41   #4
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Re: Uh oh! Composite concrete stainless hull.

See http://www.nickelinstitute.org/~/Med...022_.pdf#page= For a scientific study on stainless embedded in concrete. The short answer is that being buried inside concrete acts to raise the PH enough that electrolysis is pretty much shut down, which prevents crevice corrosion.

The problem is that the study deals with deeper embedment than a boat would have, and the study ends at 12 years.
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Old 27-10-2013, 15:58   #5
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Awesome input Stumble! I will review.... This is what I really like to see, good research data. Back in the old days, I never gave this stuff too much thought but now with a my first wee one on the way, and intending on cruising with a family onboard, I want to leave no stone unturned...
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Old 27-10-2013, 16:15   #6
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I don't have any expertise or knowledge on these types of builds, but I picture the mesh web as equivalent to glass fibers in fiberglass. In other words, adhesion isn't the main point of it - the combination of the strength of the mesh with the properties of the matrix is the goal. Are ferro boats really that wet inside the concrete? If so, it seems like mild steel would rot quickly.

Mark
Yes. The mesh is the same concept as glass fibres. So that takes away one negative variable, thanks.
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Old 27-10-2013, 16:34   #7
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See http://www.nickelinstitute.org/~/Med...022_.pdf#page= For a scientific study on stainless embedded in concrete. The short answer is that being buried inside concrete acts to raise the PH enough that electrolysis is pretty much shut down, which prevents crevice corrosion.

The problem is that the study deals with deeper embedment than a boat would have, and the study ends at 12 years.
Ok so I am very excited from what I read. The study by far concludes this as a superior method of construction, showing generally superficial corrosion over the 12 years study. The study shows retarded electrolytic action due to the alkalinity of the concrete, Portland cement most notably. Our vessel was laid up in a one day pour using Portland. So if the large rebar is mild steel, it will of course corrode faster than the stainless, but this saves the more vulnerable smaller gauge mesh and will promote better overall integrity. The action will be slowed by the Portland's alkalinity, but the ph will slowly fall off once the hull cures, so eventually (after a very long time) the benefit of the concrete alkalinity will be lost.

So now onto dissimilar expansion rates? ....
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Old 27-10-2013, 17:25   #8
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Re: Uh oh! Composite concrete stainless hull.

Ferro mix is 2:1 so with a good paint coat the high cement content should keep the interior dry. We just cored a hole for our diesel heater exhaust - main steel bars as new after 30 years..
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Old 27-10-2013, 17:42   #9
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Re: Uh oh! Composite concrete stainless hull.

ijiraq , Only one problem, ijiraq, I understand that polar bears just LOVE composite concrete!!
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Old 27-10-2013, 17:44   #10
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Re: Uh oh! Composite concrete stainless hull.

Come on gts - the guy just got the boat so let's let him bask in his ignorance for a while. Later we will tell him they love LIGHT BLUE composite concrete the best!

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Old 27-10-2013, 19:58   #11
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Come on gts - the guy just got the boat so let's let him bask in his ignorance for a while. Later we will tell him they love LIGHT BLUE composite concrete the best!

Mark
Ok guys, you seem to know something about the boat that I do not... Lemme in the loop? Or at least tell me if it is serious... You are giving me anxiety.
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Old 27-10-2013, 20:04   #12
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Re: Uh oh! Composite concrete stainless hull.

As long as there has been no 5200 used on it, the polar bears will probably leave you alone....

Just don't take the boat to the Nunavut region.

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Old 27-10-2013, 20:23   #13
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As long as there has been no 5200 used on it, the polar bears will probably leave you alone....

Just don't take the boat to the Nunavut region.

Mark
I googled it, I don't think the bear have an attraction to it or like to eat it... But seriously? How much of that stuff did she use on the boat??? I have vision of 5200 with blue pigment covering the boat..., now I am worried. I'm gonna have the nightmares
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Old 27-10-2013, 20:34   #14
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ijiraq , Only one problem, ijiraq, I understand that polar bears just LOVE composite concrete!!
I should say composite stainless, I found an insurance broker who says if I can now just get a surveyor to call it that, I can insure it for more than liability, till I get it to Ontario or Quebec at least. Composite can mean any variety of materials blended or layered together, I know it would almost be a lie, but it is just bending a wee bit
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Old 27-10-2013, 21:08   #15
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Re: Uh oh! Composite concrete stainless hull.

Nice looking boat. You bought it t now you should focus on regular use and upkeep. For heavens sake, just enjoy. Or...you could buy the Flying Hawaiian. Only kidding.
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