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Post by jeff on Aug 2, 2017 20:37:14 GMT
Think of the rebar as the rib cage. It provides structural support against pressure, the same as studs in a wall. Even concrete filled cavities in a cinder block wall have rebar. But it allows for a thinner covering, by redistributing stress, as well. By removing the rebar, you may well need triple the amount of cement.
One thing I came across (it's either in here, or on TSI) is a thermoplastic enamel that could be used instead of resin, to make reshapable composite rebar. Heat, bend into place, allow to cool. The reason I searched for it is that Basalt rebar is strait. Comes in coils that are under tension, ready to unwind and be straight, much like an archers bow is under tension from the bow-string. Steel rebar can be bent into shape and will hold that shape. Composite rebar that can be reshaped would allow any outside forces to create that tension, and resist deformation.
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Post by thebastidge on Aug 2, 2017 21:46:00 GMT
Think of the rebar as the rib cage. It provides structural support against pressure, the same as studs in a wall. Not saying don't have any rebar at all. Bulkheads and ribs. I'm just talking about skinning the hull. The scantlings. There have been ferro boats with pre-cast ribs, pre-cast cross-bracing bulkheads. I would think that a heavy basalt cloth provides as much or probably more tensile skin integrity as .5" or 1" chicken wire mesh would. Especially in addition to the greater flexural modulus (5x?) of geopoly over portland cement. You form the hull with geopoly concrete cloth over an inner hull mold, cure it, flip it over, and pour your bulkheads and ribs inside the hollow shell of the hull. With nice, straight basalt rebar in them. Perhaps the inner hull mold has grooves formed in it to leave slots where the bulkheads and ribs will go. A lip intrudes inward from the hull on each side of a bulkhead, and the bulkhead is cast in place inside the groove formed by those two lips. It makes the inner mold more of a precision job than just casting over a smooth mound. But the ribs and bulkheads bond with the hull material as well as having a mechanical joint with basalt rebar inside. Although, if you had just a rib, and no bulkhead, some basalt rebar bent from port to starboard inside the rib (u shape) under tension might not be bad either. The pressure of water outside the hull is in opposition.
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Post by thebastidge on Aug 2, 2017 23:19:09 GMT
My thought is a mold and concrete cloth make an easily-repeatable process without a LOT of infrastructure and tooling, not too much expertise necessary, and moderate to good quality control.
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Post by thebastidge on Aug 2, 2017 23:39:00 GMT
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Post by jeff on Aug 3, 2017 3:52:18 GMT
Take the method of "C" and follow the pattern for "F". I've done that to lash poles for a trellis. Outstanding!
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Post by thebastidge on Aug 3, 2017 16:20:38 GMT
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Post by thebastidge on Aug 3, 2017 19:45:50 GMT
infrastructure.milliken.com/geospray-geopolymer-mortar/These guys (Milliken) also hold the US-licensed distributorship for the UK's Concrete Canvas product. I could see an inner mold, covered with basalt cloth, spray on a layer of geopoly using a X,Y,Z axis controlled arm for precision coverage, pretty easy to build. Layer on another basalt cloth piece, press it down and eliminate any wrinkles or flaws, spray again, etc. until you have a 1" hull crisscrossed with fibers embedded in geopoly. Probably two to four days of labour with 2 or 3 people for this stage. If you can pre-cut the fabric pieces with some kind of template, probably saves some time and reduces error. Maybe one comes up with a way of stitching basalt fabric pieces into shapes, not just dimensions. If it takes a little time to get the next layer of fabric absolutely smooth, no worries because geopoly bonds to itself and to basalt even when the first layer is dry. If a wrinkle sneaks into the fabric and shows up after it's dry, just sand/grind it down before spraying the next layer. The final layer gets individual hands laid on to make a smooth finish. Maybe coated with a sealant to make it slippery-smooth for better performance. The shell gets flipped over. The initial mold had grooves in it. Now you cast tongued bulkheads and ribs into those grooves, with basalt rebar cross-reinforcement. Some of the bulkheads eventually get fitted for water tight compartments (something most pleasure vessels lack, even in the high end yacht market). Your compartments are now roughed out, you put a deck on it. Maybe that's geopoly too, probably it's some lighter composite. Add systems, power, superstructure, and furnishings like any other boat. The big time/cost savings would be in using a mold and a spray arm for applying the geopoly. This also makes it repeatable with quality control and therefore marketable. Just need a good hull reinforcement design that works with a pre-built hull shell. If it's a sailboat, the foot of the mast gets a nice strong socket ring right in the center of a thickened keel and a crossrib. For my personal preference, I'd go with a modified daggerboard/leeboard setup because it's easy enough to automate such things these days- far less likely to fail than a canting keel, less expensive to replace, can be operated manually, and allows for much shallower draft.
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Post by jeff on Aug 3, 2017 21:16:01 GMT
I have the FAO one, as a pdf, somewhere. Probably the same as the UN one.
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Post by thebastidge on Aug 4, 2017 4:16:55 GMT
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Post by thebastidge on Aug 4, 2017 16:09:50 GMT
Discussion on sheathing wooden boats in ferro that stirred my interest in using a male mold method with geopolymer and basalt cloth in place of ferro and portland cement: www.ferroboats.com/sheath.html
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Post by thebastidge on Aug 4, 2017 17:44:52 GMT
From: ferrocement.net/ferro/files/lfcdefinition.pdfThis sounds conceptually similar to what I am proposing. A male mold is sprayed with a uniform thickness of geopolymer cement using an electrically-controlled x.y.z. articulating mechanical spray armature. The laminating layer of basalt cloth is overlaid, pressed into firm contact, making sure to wick up the Geopolymer. Smoothed and trimmed. The next layer is sprayed over it and another layer of cloth applied. the end result should be a light, thin, very strong laminate. The recent improvements to mechanical mortar sprayers makes it feasible to achieve a speed/cost savings not available when the original wave of FC boats were being built in the 70s, but also a level of quality control and finer application than is possible by hand. If multiple .2" layers of mortar can be applied with a 5mm (.2") or less basalt cloth between them you can have a 1" hull thickness with 5-6 layers of sandwiching, all of them chemically bonded to each other, and still be 15-16% lighter than a FC hull. If you went to 1.2" of hull thickness you would get the same weight as a 1" FC hull with a great deal more strength. This would not be possible with ferrocement because FC relies upon 1) mechanical joints between the steel and mortar that require physically larger dimensions of reinforcement with 2) no places where metal on metal with no gap between prevents the cementitious matrix from forming a mechanical connection, and 3) significant thickness of mortar to delay chlorine ion intrusion corroding the iron-based reinforcement. In addition to the better adhesion between the geopolymer mortar and the basalt reinforcement, it would also likely benefit from greater structural strength in the mortar mix itself by addition of chopped basalt fiber to the morter mix prior to spraying it on. Even standard Portland Cement benefits from this.
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Post by jeff on Aug 4, 2017 22:41:04 GMT
Think I'll stick to the tried and true. I do like those links to the fiber reinforced geopolymer spray...
Much as I would love to continue working on my formula, it's a back-burner thing, right now.
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Post by thebastidge on Aug 4, 2017 23:02:57 GMT
The Milliken guys told me they only sell their geopolymer mix to licensed partner contractors. I'm trying to find a commercial source of it so I don't have to mix my own- speaking of tried and true. I inquired about ordering in the one to two pallet range for private projects after they told me they don't sell to the home market.
I think a rowboat with outboard attachment on the transom is within my capabilities for experimentation. I know the rule of thumb for FC boats is somewhere north of 28 feet, and I don't plan to make it that big. But I think this male mold/lamination technique is worth exploring in a smaller vessel. If I can do it there, it's worth planning for a bigger vessel.
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Post by jeff on Aug 4, 2017 23:44:56 GMT
Rule of thumb, yes, but as a practice run to prep for something larger, it really makes sense to do one much smaller. Maybe create a 'tender' to go with your main squeeze.
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Post by thebastidge on Aug 5, 2017 0:08:13 GMT
Yeah I figure I can craigslist it anyway. With the Willamette, Columbia and a bunch of lakes, someone will buy it when I get ready to do a bigger one.
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