In this installment of my Captain America ball chair project I have been working on the construction of the mold that will be needed for the six inner curved triangular pieces that will make up the interior of the chair.
The images above are what I hope to succeed at making with the mold. This will be a first for me as I have never made a mold before in fiberglass. Hard to believe with all of the projects that I have created over the years but with the construction I have done in fiberglass it has all been composite mold-less in nature. A much simpler way to make things and if I don't get this mold to work right I will have to go back to what I know and try again. So this is the process for now.
I had to do a lot of calculations and checking of my design in my CAD software to work out the mold I need for the six inner wedge pieces for the chair. All of the wedges need to be exactly the same so what better way to do this than with a mold. I started with five inner curved pieces to give me the shape I will need for the inner ball wedge surfaces. These curved pieces were joined together with a horizontal curved piece and then evenly space at 15 degrees each to get the right shape that I wanted.
These five curved pieces were then mated to an upper foam piece to get a connection point that would tie all of them together. I had to join a two inch pink piece of foam with a one inch piece to make up the three inch joint to match up to the width of the curved pieces. All of the parts at this point were simply hot glued together to hold them all in place for the mold. I did not bother fiberglassing any of the parts before I assembled them as the structure did not need to be terribly strong to make the mold.
Additional foam pieces were added at this point to the outer perimeter of the wedge mold to help make the lip of the part that will be molded. This will make more sense in the next few photos.
Here's a good shot of the upper joints of the mold. You can easily see the joints that were made for the curved pieces of the mold and how they mate up at the tip. Wrapped around this tip is the outer form to help create the lips that will run around the outer perimeter of the wedge parts that I need to make. The outer pieces are three inches taller than the curved ribs and the lip for the parts being made will only be two inches tall. So it gives me a good surface to easily make this portion of the parts. Once the parts have been removed from the mold they will be trimmed to the size I need.
Next I stared gluing in the Styrofoam strips that will create the compound curved surface of the wedges in the mold. Each of these strips needed to be hot glued into place after carefully measuring and trial fitting each of them first. A long and slow process but interesting to work on just the same.
Here all of the foam strips have been added to the mold. It took me roughly nine hours just to complete this portion of the construction. As I said a slow process to be sure.
Once I had all of the foam strips in place to my liking I turned the assembly over and fiberglassed the spaces between the curved ribs of the mold with eight ounce fiberglass cloth. I let this cure overnight so that it would be good and strong for the following steps in the assembly.
I then sanded the inner surface of the mold to get a nice uniform curved surface. The fiberglassing that I had installed on the back surface of the mold gave me a strong surface to easily perform this part of the build. I next cut a large piece of eight ounce fiberglass cloth so that I could glass the interior of the mold all in one seamless piece. Being that the mold is triangular in shape it was just simpler to cut a rectangular pieces of cloth and lay it in the mold so that it would fit correctly first time out. I had filleted all inner edges with fiberglass epoxy and micro-balloon mixture to get a good edge before I wetted out the cloth.
Here is what the mold looked like after the glassing had been completed. The cloth turns transparent when enough resin is applied to the cloth. It makes it easy to see what is enough or not enough resin when doing this part of the job. I had also trimmed off the excess fiberglass cloth that was hanging over the outer edges of the mold as it made things easier to get the inner cloth to stay where I needed it at this point in the construction.
Here the mold is completed. You can see the white of the inner fillets that were applied to the mold before I laid the glass into place. I had also fiberglassed the outer surfaces of the mold as well so that it had a nice strong structure now. You can see another white strip of putty mixture that I had built into the upper lips of the mold so that the outer fiberglass cloth could be attached securely to the assembly and give me a good 90 degree edge at the same time. The next step in the process to complete the mold is to use additional fiber glass resin putty to fill the weave of the fiberglass cloth on the inner surfaces of the mold. Once this has cured it will be sanded smooth and prepped to make the parts for the chair. If all goes will I will end up with six identical parts for the interior of the chair that will match the first images in this post.
I will need to keep my fingers crossed at this point and hope that I have my calculations right for the design and that I can get the parts out of the mold without any problems. As I said this is another learning process that I hope will work out for me. Just will have to see when I get that far with this portion of the build. Wish me luck.