Super Reaper Composite Fuel Tank Mold Construction

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Mold Construction - Day 4

The time has come now to make the second half of the mold. The first mold half and plug have been given 5 to 7 coats of mold release wax as well as the boards that will form the fencing.

Since the process of applying the Fibreglast 1099 epoxy surface coat tool resin has already been explained previously I will skip the details. The picture below shows the tooling resin having been applied and I put up the fencing. On the second mold half I decided to put the fencing up after I applied the tooling resin. Although it was easier to apply without the fencing I'm not sure I like the thickness that was achieved. Another note is that I used a popsicle stick to spread the tooling resin out like icing a cake.

Because the temperature was a little lower then what I thought was appropriate I decided to apply some heat with a work light that I have.

After the tooling resin setup for about 4 hours I again mixed up some epoxy and cabosil to help soften the edges and corners of my mold. This will allow the fiber glass cloth to conform better.

I gave the epoxy cabosil filler mix about 2 hours to setup before I laid down 2 layers of 6 oz fiber glass cloth. After the cloth was laid down I started mixing sand and epoxy. I achieved a good wetness to the sand by pumping 4 pumps of West Systems resin and hardener to 36 oz of sand. To achieve this I pumped the epoxy into a large bowl and added 9 oz cups of sand one at time mixing between each cupful. The bowls I used for epoxy sand mixing were purchase from Walmart for under $3.00 for a set of 4.

The picture below shows the results after 1 bowl of sand was shoveled on to the mold. As you can see the sand looks like brown sugar after being mixed with epoxy.

Just a picture showing my overall work area along with the materials I am working with.

After I think 5 bowls of sand I ended up with the results as seen below. Before I put the last bowl of sand down I did use my hands to pack it down really good. Then I shoveled the last bowl over the mold and used a wooden block to pack and level the top everything off.

Just another picture showing a full view of everything. Oh, I gave up on using a plastic spoon to mix the epoxy and sand because I broke 3 of them. So I started using a paint stirring stick and things worked out very well.

Here is a close up of the epoxy sand mix. It may look a little dry because I sprinkled a lot sand over the top to soak up any extra resin. TIP: Make sure you let the epoxy and sand cure out before applying the fiber glass cloth. If you start too early the cloth will not stick down to the sand.

I went ahead and let the epoxy and sand mix cure over night with the help of a light. Then the next morning I applied 2 layers of 6 oz fiberglass cloth.

I allowed the fiberglass cloth to cure over night too. I started the second mold half on Saturday morning and started to take off the fencing Monday at around 4:00pm.

After al screws were removed I inserted a plastics putty knife between the mold and fencing.

After sounds of cracking and a little force I had the first fence side off. This picture shows the layers of the mold making process. The tooling resin is shown in gray, followed by the white epoxy cabosil mix and finally the epoxy sand mix. Later I will clean up the mold halves and get them looking more professional.

Using the putty knife I worked my way around the mold to remove the fencing.

Ok, the fencing is removed and now the hard part of separating the two mold halves.

I tried with the putty knife first, but I was unsuccessful at getting the two halves apart. After looking and trying various other means to separate the halves I carefully used a flat head screw driver on the corners. I was able to get an opening large enough that I could hammer in some 1/8" lite ply.

Using the lite ply I went around the mold until I had an even separation.

I worked the opening enough until I was able to fit some 1/4" MDF between the two mold halves. Then I worked with the MDF to separate the mold halves.

Finally the two halves were separated!

I took both mold halves outside the garage and hosed them down with water to remove the PVA residue. A soft sponge or wash cloth makes the PVA removal process easier.

Overall I am very pleased with my results. There is some primer from the plug that appears to have transferred to the mold halves, but that can easily be scraped off.

I do have to report that I damaged my plug quite severely in an effort to separate it from the second mold half. Since the molds came out so well I'm not to worried about it. But next time I decide to do a fuel tank I will probably make it out of foam covered with fiberglass so I can remove it easier. The tank I made was from 1/4" plywood that was glued together and fiberglassed. Although because of the tank shape and depth of the mold I was not surprised with the trouble I had removing the plug.

The next step will be to clean out the primer that transferred and then wet sand the mold to prepare the surfaces for wax so I can try laying up my first fuel tank.

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