Forming Complex Items—such as NFRC Furniture

 
 

 

Natural Fiber Reinforce Concrete (NFRC) can be used to produce a number of complex items. You lay it like paper maché you used in high school to build a complex parade float, but it gets hard and permanent because it is cement. So its versatility is great, while is cost is quite small. You can paint it, shape it, make all sorts of things with it including homes, islands, and furniture. It's ideal for hand work.

 But you should do the simple projects, such as Deck Hexes to gain skill in working with NFRC first.

  There are several processes that need to be understood from both study and experience. If you are building a form of NFRC, it needs to be reusable. You need to be able to remove the final piece from the form without the piece sticking to the form, and without destroying it.

  To do that, the form should not be made such that the piece holds mechanically inside the form. Thus, the form is made such that it has proper “draft angles”, that is, the openings are slightly larger at the top and slightly smaller at the bottom, so that the hardened piece will be more easily removed from the form. This usually requires an angle of at least 2°.

  If the form is to be used in high temperatures, such as a Rotomold for plastic, use Refractory Cement, rather than Portland Cement.

  Forms can be of a single piece, or multiple pieces you have to dismantle to remove the formed product.

  The forms should have flat, slick surfaces, also to prevent the piece you are forming from being stuck mechanically to the form. Thus the NFRC form can be constructed on plastic. This produces a shiny NFRC. Also, when the form is finished, you can coat it with diesel fuel as a form-release. However, NFRC is waterproof, and will tend to not soak up the diesel as wood would.

  Therefore, coat the surface with wax. Rub Paraffin Wax into the surface where you don’t want the piece to stick to the form, but only shape the piece.

  Plastic drop cloths may also be used for this. And it can make a fine bond-breaker. The problem is the folds in the plastic tend to leave marks in the finished piece. Thus, small projects may use Plexiglas or preformed plastic, such as a plastic trash pail, to avoid such marks. Or use rolled polyethylene as it has the folds further apart.

  Some plastic is destroyed by the ultraviolet rays of the Sun, so think about how you intend to use it.

Furniture

  There are 2 types of furniture that you may wish to produce inexpensively with NFRC— Ones with multiple pieces that need to be hooked together, and those of a single piece.

  You can build a form from NFRC if you do it right. An example of a single piece is a lawn chair. These you can purchase inexpensively. That’s the easy way. But if you desire to make your own of NFRC chairs, it is possible. You only have to buy one of them.

  Notice that the commercial chairs are smartly engineered both for making the chair strong, where it’s needed, and with proper angles so that it can be removed from a form. Thus you can use a commercial one to reproduce the form that was used to make the chair. It’s tricky, but possible.

  However, plastic chairs are poured of molten plastic. And NFRC is laid by hand into a mold. Thus the mold you build needs to be open on one side so that you can access it with the fresh NFRC when building the piece you wish. Think about it!

  And the final piece needs to be smooth and comfortable to sit in, on the arms and seat where you will be sitting. Thus, the form needs to be made to produce what you desire.

  Also, plastic chairs are not fibrous, but your finished product will be. Therefore you don’t want weak spots where the fiber is not continuous, or where old NFRC is being connected to new NFRC. Will you be using Palm leaves that are more continuous, or hair that is more random. You have to adjust your method accordingly.

  The 2nd type of furniture is made of multiple pieces that must be assembled. The forms for making them must allow the final pieces to be assembled, and shaped accordingly. There are several ways for assembling the final pieces.

  1. Portland Cement will act as glue, only if you purchase the chemical additive, which makes cured cement stick to fresh cement. And then allowed to cure together for a week or more.

     A separate glue, such as Liquid Nails can be used too.

  2. Fasteners can be used between properly aligned finished pieces. The biggest problem is alignment. In theory, you could simply put a wing nut in one, and a hole in its mate for a screw. But it’s difficult to get the two aligned, unless you allow for it. Two fasteners can be used, but one may fit and the other not. The second one may be slightly out of alignment, and thus too tight to connect without breaking the NFRC, or they may not match at all.

     If you use wing nuts, keep them in alignment by putting a screw through the form, while the wing nut is held in place in the NFRC. You may have to add a plastic sheet to act as a bond-breaker at that position. Or you may have a nut fixture that allows movement of the nut after the NFRC hardens.

      Another way to connect pieces, is to allow for such displacements by the type of fastener chosen. One piece can have a piece of wood inserted in it and the other a hole for inserting a screw, you can then screw into the wood rather than the NFRC itself. The screw may need a washer to prevent the screw from just sliding through the one piece as you tighten the screw into the wood. Oblong screw holes can use washers too.

      The piece of wood you insert should not come loose when you put the furniture together, so it may need nails or a special shape to keep it tight. Or if you just make a hole in the NFRC then insert toothpick pieces of wood to hold the screw.

      Drawers can be made also. Such moving parts can have wheels, or simply a lump of NFRC to reduce the sliding surface area, or a fixture made for drawers can be used. The smooth slide surface can later be coated with wax, or soap to make the drawer move smoothly.

      These slides are often screwed in place. In that case you can insert some wood in place, or the NFRC can be made to hold the screws. In that case use some masking tape to temporally hold the screws in place while their threads are being cured into the NFRC. Consider, if the final screw it to be removable, then coat it with wax. If not, the cured NFRC can be made to hold the screw tight. This depends on what the screw is made of, steel, plastic, brass, or whatever. Try it to learn which one you want.

Surfacing

  The surface may be colored, or coated with a material as you like. This may be flat, for painting, or textured for spray painting. Coloring may be placed in the NFRC. The availability of colors is limited, but readily available.

  Some of your options for surfacing include materials, such as

  1. Old cotton clothes you cut up from a yard sale. But be careful to keep it clean, yet submerged in the NFRC at the edges. And stretched tight.

  2. Leaves pressed into the NFRC.

  3. Paint

  4. Paper, newspaper, old magazines or other such things we used to glue onto wood.

  5. Objects, such a pretty stones or loose things as are often placed under glass on a table.

  6. Glass or plastic windows. In that case think about the final location and use. If used underwater, it will have water pressure on it, so use Tempered Glass, such as from a commercial patio door, or safety glass, which has a layer of plastic inside to prevent the glass from shattering. Skylights are another example. And a table’s edges need to be ground so you don’t cut yourself at breakfast.

     Aluminum window frames will cause the NFRC next to them to expand, due to corrosion. So you may need to paint them first. Steel windows made for embedment in concrete are a good idea too. You can get both kinds at your local hardware store.

      If you expect wildlife such a fish, you may need access for cleaning and feeding, and you need to plan the design for it.

      If table tops or regular windows are to be used, then regular glass can be used, however your island moves, and thus rough-service glass or plastic may be in order. And a window frame may be used, not only so the window or whatever can be opened, but changed if need be. And, what happens when it rains? Also, remember that plastic scratches much worse than glass, but if it is removable this will allow for this.

  Some of these surfaces are applied after curing, and some can be applied before. How you make it depends on how you intend to apply the final surface. If you just think about it, there are many options open to you, and inexpensive ones too.

  If your project needs compressive strength, or to spread out the Portland Cement, sand can be added at the traditional level of twice the volume of the Portland. However, it will affect its waterproofness, and must be mixed well. Where the gravel in the traditional mix is replaced with fiber. However, if you get your sand from the bottom of the sea, it first needs to be washed with fresh water.

  When Portland Cement cures it needs to be kept moist. One way is cover your NFRC project with a plastic drop cloth to keep it moist for at least a week. Then you can let it dry out.

  Afterward, NFRC can also be changed with a jackhammer. However, a little thinking ahead of time can eliminate that step.

  It can also be fun and fruitful.

 

    Thanks for your interest.

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