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Steel Trim Tabs (original) on Aluminum boat

Discussion in 'Chris Craft Roamer Yacht' started by roamertim, Oct 26, 2010.

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  1. roamertim

    roamertim Member

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    hi Roamers,
    While doing the bottom this year, I found something that surprised me a bit. The original equipment trim tabs on my 1969 38' aluminum Regal are made of steel. There was some rust colored corrosion on the mounting feature on each, which made me check it. Magnet sticks to the trim tab as well.

    The trim tabs themselves have no corrosion on them (aside from at the mount hole for the actuator), so not as if it is problemmatic for me. I was surprised though.
    Any thoughts on why CC put steel trim tabs on this model?
    Just seemed odd to me.
    Tim
  2. m2m

    m2m Senior Member

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    newport ri
    I am no expert but my guess is that they are poor grade of stainless steel, which a magnet will stick to.
  3. Marmot

    Marmot Senior Member

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    The magnetic property of stainless steel is not related to its quality, only its composition.
  4. m2m

    m2m Senior Member

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    I'm only trying to point out that some types of stainless steel rust
  5. 9lives

    9lives Member

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    Lake Superior
    Steel tabs

    The tabs on our boat were Steel as well and were one of the first places pitted. We converted to stainless which was an easy change. You wil find the rudder is the next place to look at converting to stainless as well.
    The cost to engineer and fabricate my tabs was a bit south of a Boat unit.
    I have an engineered drawing if you would find it helpful, just beware it is drawn for a 41 Regal.
    Mark
  6. Marmot

    Marmot Senior Member

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    "The trim tabs themselves have no corrosion on them (aside from at the mount hole for the actuator)"

    Even 316 will show rust in the heat affected zone around a weld or where drilling has created a hot spot unless it has been properly passivated. It is the nature of the material and has nothing to do with its quality or other properties.
  7. danneva

    danneva New Member

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    Stainless steel do rust, it is the fact that the presence of the chromium that provides stainless steel with the ability to repel permanent stains and keep looking fresh and clean over long period of time. The chromium essentially creates a protective layer on the alloy that prevents rusting and makes the metal resistant to any real damage. Essentially, the addition of nickel to the stainless steel compounds helps to strengthen the protective qualities of the chromium. The reason is that the presence of the nickel alters the physical structure of the stainless steel and removes or inhibits any magnetic qualities.
  8. q240z

    q240z New Member

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    zsedr
    Lotsa technical info on stainless...

    But AFAIK, all aluminum Roamers came with plain steel tabs. If you look at the galvanic series in seawater, aluminum and plain steel are more compatible than aluminum and stainless steels, the worst of which are further away (i.e. less compatible) from aluminum alloys than even copper or bronze in certain circumstances. If I had to guess, I'd say Chris Craft used steel because it could take the beating in that application and it's the most compatible option.

    But it can rust, so you gotta keep up on the barrier coats and bottom paint.
  9. JOE.B

    JOE.B New Member

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    Specking of trim Tabs.. I reticently acquired A 1968 Steel Roamer.. That will be run entirely in fresh water in the 9 to 12 kts range. I really can see no advantage of maintaining the tabs in that environment. I am I missing something??. I'm hoping to be able to adjust trim with fuel and other ballast techniques.
  10. NYCAP123

    NYCAP123 Senior Member

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    I'm not familiar with the handling characteristics of your particular boat, and at those speeds the effect of tabs are generally more minimal, but you want to be able to do more than just lay your boat to one side all day. You want to adjust to circumstances as they arise (raise the bow when running with the seas, lower it when running into them, lean into a beam sea, etc.). I've come through some inlets where the use of tabs was critical for maintaining control.