Ok everyone, it's that time of the year again: time to talk about concrete

Discussion in 'Materials' started by dsigned, Sep 21, 2017.

  1. Rumars
    Joined: Mar 2013
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    Rumars Senior Member

    May I ask what you are trying to achieve with this test panels? Just seeing how low you can get the weight? Or can you actually test them for other properties?

    If you really want to build a small boat in ferro and want something else than a canoe I recommend following aproach:
    1. Buy Jay Benford plans for his 12' keelboat. Benford Design Group http://www.benford.us/index.html?scp/ They are 60$ and the smallest FC boat I know of outside canoes.
    2. Buy or borrow Jay Benfords book about FC construction.
    3. Build a really sturdy strip plank male mold out of common lumber and fair it to perfection.
    4.Reverse engineer the boats structure.
    5. Invent some cement mixtures that are lighter than the original one while keeping the strength.
    6. Replace armature with something else while keeping the strength.
    7. Plaster test panels on said mold over armature. The original boat had 1/4" skin thickness and mirror finish. That's your benchmark.
    8. Test panels to destruction.
    9. When you are satisfied plaster a complete boat.
    10. Test boat to destruction, then repeat step 9.

    Microspheres (glass or phenolic) you can get for example from the epoxy vendors, they are used as fillers. Google everything and buy online.
     
  2. dsigned
    Joined: Aug 2017
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    Location: United States

    dsigned O.R.C. Hunter

    The condescension and bad (or mundane to the point of headache) advice continues.

    "Trying" to achieve...sigh...

    Right now I'm primarily trying to learn about the mixes that I have available to me cheaply. How much water they take, what kind of workability I can expect, how they cure, how different things affect the color, what kind of porosity I'm looking at.

    As far as destructive testing, I can and may rig up a legitimate flexural test, but I think most of the properties are going to be qualitatively apparent. The weight is actually an interesting one, as I mentioned above. I forgot where the MK II was, but I think it was something like 80 ish lbs per cu ft. Not bouyant, but way lighter than normal concrete (even the MKI panel). Part of the reason that I'm not too concerned with the quantitative testing just yet is that I haven't added any pozzolans or water reducers/superplasticizers to the mix, and I haven't really done anything with the curing (although I may use some sort of set accelerator: 28 days is a friggin lifetime). Plus, the mix kind of is what it is. I'll make it as good as I can, and see if the result is good enough to sail around on. If it's not, then I might go back and evaluate where I can improve (which I expect there will be many areas, even without focusing on destructive testing). I'm not doing this for a project: there's no old codger evaluating whether I did the proper 12 test cubes for destructive compression testing.

    1. There is no good reason to go with a 45+ year old keelboat design. Other than the fact that it's small and that someone else made one out of ferro 45 years ago, it doesn't have much going for it. There are a million other boats I'd rather build that would be faster, easier to build, easier to rig, and easier to transport. Not to mention that I could potentially find and make a female mold from...
    2. Maybe? I'll ask the canoe engineer if he recommends it, but I'm guessing there will be enough disanalogies that it's not going to contain much that is directly applicable that I don't already know (or won't learn along the way). Especially since I'm not actually working with ferrocement, and the information contained therein likely hasn't been updated in decades.
    3. No, there is no reason to do this when I have closed cell styrene on hand. It's slower, more expensive, harder to work with and of dubious benefit for my purposes.
    4. Again, since the boat offers no appeal other than having been built by someone else out of ferrocement 45 years ago, not likely.
    5. Thank you, Captain Obvious.
    6. It's a good thing you mentioned this, otherwise I might have forgotten that I had previously mentioned fiberglass and basalt meshes, and PVA fibers.
    7. I love how you mention thickness but not weight or strength.
    8. K thanks.
    9. Oh, this was another step I might have forgotten had you not pointed it out. I was actually posting here and doing all this work to build a structural mammalian feline. That's what I thought "cat" was short for.
    10. I'll probably just sail it around on a lake or something.
     
  3. Rumars
    Joined: Mar 2013
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    Rumars Senior Member

    Ok i'll stop giving unrequested advice. You obviosly have enough of an ideea about boat scantlings that having an actual boat designed by an actual NA as a base reference is unnecessary.
     
  4. dsigned
    Joined: Aug 2017
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    Location: United States

    dsigned O.R.C. Hunter

    Test panel #2 is down to 780g after drying out. I seem to remember after working it out that it comes to something like 71lbs/cuft 9 or maybe 68?) which is pretty darn close to my target weight (or maybe more accurately, getting a lot closer). Anecdotally, the panel is really stiff, and feels almost hollow. Lots of efflourescence. I tried some of the stain, but didn't do any prep, and so got inconsistent absorption.

    The latest pour is with more ground glass, and with some of the superplasticizer I got years ago added. Not sure if it's still any good. It definitely didn't affect the mix as much as I thought it would (I couldn't say that there was a drastic difference). This is actually a refractory mix to make myself a little forge, so I won't be testing it.

    I spoke with a regional lightweight aggregate guy, who said he would give me a sample of fine aggregate (which is a 5 gal bucket). It's actually not that light, so I'm not sure how useful it will be for me, but it's free.

    Haven't heard from the concrete canoe advisor, so I'll need to send my prof a follow up email.
     
  5. DAVID HOE
    Joined: May 2018
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    Location: HONOLULU, HAWAII

    DAVID HOE New Member

    I would like to get in touch with O.R. Hunter (designed) the author of this thread via email ... David K. Hoe tocsvs@gmail.com ... I build wooden Chinese Junkboats ... light weight hulls are not an issue ... maintenance is the bigger issue ... concrete hulls would be immortal and relatively maintenance free .... thanks.
     
  6. SamSam
    Joined: Feb 2005
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    Location: Coastal Georgia

    SamSam Senior Member

    You can click on his name and then send him a private message by 'starting a conservation'.
     
  7. dsigned
    Joined: Aug 2017
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    Location: United States

    dsigned O.R.C. Hunter

    I did just that, thanks.
     

  8. dsigned
    Joined: Aug 2017
    Posts: 130
    Likes: 6, Points: 18
    Location: United States

    dsigned O.R.C. Hunter

    Since it apparently looks like I was just being a jerk and ignoring you, I'm just going to leave this note saying I did in fact email you.
     
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