Super Reaper Composite Fuel Tank Mold Construction

Ahead to Day 4 or back to Day 2

Mold Construction - Day 3

With the PVA dried I was now ready to apply the tooling resin. Here are the materials that I will be using today to make the mold. They are West System epoxy, small scale, 9 oz Dixie cups, black pigment, and Fibre Glast 1099 tooling resin.

I found the best way to work with the tooling resin was to mix it out on a paper plate. I tried mixing it in a cup but did not like the results. This stuff is a lot like taffy until you pour in the hardener. I went ahead and zeroed out the scale with the paper plate and popsicle stick on the scale. See how I finally arrived at using a paper plate to work with the 1099 Epoxy Surface Coat / Tooling Resin.

I dished out 100 grams of tooling resin. Because the resin and hardener are mixed at a ratio of 100:11 this meant I would use 11 grams of hardener to the amount of resin I dished out.

Using a drinking straw and placing my finger on top to trap the liquid inside I used that method to measure out 11 grams of hardener into a small 3 oz Dixie cup.

I then stirred the the resin and hardener together making sure to mix everything as well as possible. The resin is very tough to stir and it will eventually soften up as you add in the hardener. As it mixes it will become like toothpaste consistency or very thick icing.

After the hardener and resin was completely mixed I got ready to add the black pigment. The pigment will help make the molds turn out grayish in color and make it easier to see the wet epoxy when making molded parts. I purchased this black pigment from US Composites and I am very happy with the results.

Using a popsicle stick I dripped the black pigment over the tooling resin. It is probably a good idea to actually measure out an amount of pigment to add, but I used the T.L.A.R method (That Look About Right). If doing a large piece it might be better to measure the pigment to be added so that you can keep a consistent color throughout.

Make sure to mix in the pigment really good so that there will not be any streaks after you apply it to the plug. IMPORTANT NOTE: You have to be quick when mixing the tooling resin with hardener and also the pigment. It has a total pot life of about 20 to 25 minutes and after about 15 minutes it starts to really get gummy. So while it is still toothpaste like, use a brush to work fast and spread this stuff out.

I used a small hobby epoxy brush to apply the tooling resin. Like I mentioned above you really have to work fast and make sure that you get enough brush on the plug and parting board before it starts to get gummy..

I had to mix up two batches of tooling resin because I was not fast enough and it got gummy on me. Thus the reason I noted it up above in RED and I'm telling you once again --- Work Fast! The tooling resin takes about 16 hours to fully cure out so you need to wait at least 3 or 4 before you start building up the mold with sand / epoxy so you will not get any print through.

Next I will be coating the tooling resin with West System epoxy and actually using this to build up the mold thickness mixing it with sand. Before brushing on some epoxy I let the tooling resin cure for about 3 hours.

To allow the 6 oz cloth to conform to the plug and fencing better I mixed up some epoxy with cabosil and applied it around the corners of the fencing and plug. This creates nice curved corners instead of a 90 degree ones which would make hand laying the cloth difficult.

Another picture showing the application of the epoxy cabosil mix applied to all corners.

After the mix of epoxy and cabosil was applied I let that cure for about 2 hours before I started laying down the 6 oz fiber glass cloth. Using a brush I brushed on a thin layer of epoxy over everything so I could lay down the cloth.

Both layers of 6 oz cloth have now been applied and wetted out. I decided I would let that set up for about 2 hours before building up the mold thickness with sand.

After dumping in several cupfuls of epoxy and sand mixed together I ended with what is shown in the picture below. When I first started out mixing the epoxy together with sand I did not pour in enough sand so the mix was turning out a bit too wet. Plus the coverage was not as thick as I wanted. So I started adding more sand until I got the sand to a point where it was just damp looking. This worked out really well because I was able to get more coverage and build it up quicker. It was late and thinking I might run out of epoxy, I went ahead and used my hands to pack the sand down and form it to my plug. Earlier I had planned to dump in enough sand epoxy mix to have level coverage within the fenced area but since I had only purchased a quart of resin I did not know if I was going to have enough epoxy left to wet out the cloth that goes on top of the sand.

Another picture showing the sand epoxy mix covering the plug. The sand I used was sand blasting sand #5 that I purchased at my local Ace Hardware store. I ended up mixing 1 pump of resin and hardener with 2 3 oz cupfuls of sand into a 9 oz cup. Stirring the mix in a 9 oz cup was a bit of a chore and now that I know how the sand should look, next time I will mix everything in a large bowl.

Here is a close up of the sand epoxy mix. As you can see the sand is only damp and not too wet looking. Using my hands it was easy to form and pack down the sand making sure I had enough coverage over the plug. Next time I will use more planning and make sure I have more then enough epoxy and build the sand up enough to level it across instead of having a hump in this case.

Since it was now very late I decide to let the sand sit for only 1 hour before applying the fiber glass cloth. The cloth is only used to give the bottom mold surface a smoother feel instead of the rough texture sand alone would yield.

I laid down 2 layers of 6 oz cloth over the sand and wetted it out with brush and epoxy. Because the sand was damp and not too wet, some of the epoxy from the cloth was soaked up into the sand. This was ok since I figured that would happen and I applied more epoxy over the cloth to compensate for it.

Another picture showing the cloth after it was applied over the sand.

Now I will let this sit and harden for at least 3 days before I attempt to remove the parting board and fencing from the plug and newly formed mold half. Removing the fencing will be simply a matter of unscrewing the screws attaching the fence panel to the parting board and cutting away the tape. Then I should be able to slide the parting board over the opposite plug side.

Ahead to Day 4 or back to Day 2

Back to Composite page