Any Colorado opponauts have concrete connections?

"dsigned001 - O.R.C. hunter" (dsigned001) 01/19/2018 at 23:59 • Filed to: #concretelopnik #boatlopnik

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Looking to build a concrete sailboat with a similar mix design to what the concrete canoe guys use. Having trouble finding expanded glass spheres, and VCAS (pozzolonic powder) and fine sand. Anyone work in concrete who knows where I could score some? Trying to avoid paying shipping costs for what will amount to a dinghy.

TheRealBicycleBuck > dsigned001 - O.R.C. hunter 01/20/2018 at 14:18

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Are you doing this for a design competition?

dsigned001 - O.R.C. hunter > TheRealBicycleBuck 01/20/2018 at 15:14

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No, this is self-inflicted.

TheRealBicycleBuck > dsigned001 - O.R.C. hunter 01/20/2018 at 18:01

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I’ve thought about building a skin-on-frame canoe. After watching one of my old girlfriends go through a concrete canoe competition, I wouldn’t want to build one of those.

dsigned001 - O.R.C. hunter > TheRealBicycleBuck 01/21/2018 at 01:21

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Haha. Why is that?

TheRealBicycleBuck > dsigned001 - O.R.C. hunter 01/21/2018 at 11:09

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Exceedingly complicated build process for the end result which was, as I recall, rather fragile. It seems to me that there are cheaper/easier/faster ways to build a boat that produce a lighter and more robust hull. If you drop a concrete boat, it’s going to crack. Just about any other common build material won’t.

dsigned001 - O.R.C. hunter > TheRealBicycleBuck 01/21/2018 at 12:13

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They impetus is that, as you scale up, the cost of materials for the hull becomes a much larger percentage of the total cost, and the build complexity scales poorly for other materials compared to concrete. I’m building a small one as a proof of concept (and mostly just for the hell of it), but I’d really like to build something in the 40-50ft range, where fiberglass and even plywood are much more expensive and labor intensive.

But some of the complexity in the build for competition is due to it being a design competition (and a senior design project). Source: was junior engineering student in civil program.

TheRealBicycleBuck > dsigned001 - O.R.C. hunter 01/21/2018 at 22:08

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I haven’t spent enough time looking at the designs and scaling issues. It seems to me that building the forms would be just as complex as the other options. Even if you did a spray-on concrete, there would still be the internal structure that would require placement and tying.

Some of the considerations for the design competition were physical such as weight, minimum dimensions, minimum cargo capacity, etc. They also had to complete a course which included a portage and a paddling section, all the while carrying a load which was adjusted so that everyone had the same total weight. This really stresses the hulls and and she told it, many of the teams suffered hull failures.

It would be interesting to see how different materials scale with cost, complexity, weight, and durability.