Composite molds

Making a composite mold is all about preparation,like anything else if the foundation is good you have a good start. Mold making for a composite aircraft is no different, see what materials are available ask questions and try it. Composite materials vary and it’s always best to find the right stuff for the job.

I constantly strive to find new ways of doing things and over the years I have found some things work better than others. This time round I need to thank Mike (aka mikegbogh) for the recommendation of using a Farecla product called G6 Regular Grade Paste Compound. I contacted the local Agent, and they gave me some samples to try needless to say, two days later I bought the products, Wow!!!!. This product is available from most good Automotive paint store, if you are stuck try the Local Agent Gondolier they have a list of distributors per region. Internationally you will need to go to Farecla Products/ and track down a distributor.

Farecla G6 Regular Grade Paste Compound

Evan Shaw (jnb) at AMT Composites, always have great advice on new composite products and composite materials. They have Stores in all major centers

See the post Plug Preparation if you missed how I got the Plug to this state.

Once you have completed the steps to get the fuselage sanded, don’t wait too long before polishing as it will polish easier. Using a soft cloth apply the G6 Ultra, with a little rubbing and within 3 minutes the entire fuselage will be gleaming. I then used G18 wax to polish the fuselage more to provide the desired luster, I used this as I was given a sample of it to try. These products are all water based and are fully compatible with composite molding much to my surprise. They really do work well and are worth the cost thereof. Sadly, I didn’t take a picture of the Fuselage alone, but there will be more images of that later.

Preparing the splitter plates

My next job was to prepare the splitter plates. The take a little longer because of the wood and Method I use, I’m sure there are faster ways but this I can Guarantee works. What you will need is 12mm MDF (medium Fibre Particle Board), I source this from my Local Lumbercity and had it cut to a size that would be big enough to cover the glider and then some. I also had 4 sides cut to make a frame. A few reasons for this is that I want to back fill the mold with sand so I can put a bladder in the mold and mostly that when the mold is complete the two halves will sit flat on a table. Once this was cut I set the fuselage on the splitter plate and using an engineer square, with a pencil taped to the point of the 90 degree, I traced the profile. The profile left no gap. I then cut the shape out with a Scroll-saw but a jigsaw would work equally as well. Be sure to cut on the line, a little wider than the shape drawn to fit the fuselage perfectly. Sand the edges smooth inside to prevent scratching the Fuselage. Nice thing about MDF it’s actually quite soft to the tough and does little damage to the planes.
To Prepare the splitter plates to a mirror finish you first need to spray sanding sealer onto the MDF, leave it to dry and then wet sand it flat. One or Preferable two coats should do the trick.Just as with everything else the time and effort you put in now will show on your final product later. The sanding sealer must be the wetted Flat with 1500 grain wet and dry paper. After this has happened out comes a trusty 2K paint again, this time I used a clear 2K finish thinned down a little more then usual as it flows flat better, and helps you to sand easier. Once sprayed leave it to harden.
Here you can see the results of this exercise.
one layer of 2K clear applied

In the direct sun it will take round 40 minutes or leave it overnight. Wet it down to 1500grn and then polish the splitter plate. With G6 this takes round 20 minutes and it’s perfect, as can be seen in the pictures. The sides of the splitter plate is done in the same way as the main plate, I did it all at the same time.
polished splitter plate

polished splitter plate

Setting the Plug

Setting the fuselage in the splitter is relatively fast and is done by placing the plug into the opening. The gap around the fuselage is filled with modelling clay that is available from AMT.

nice small gap to close

To get it in roll a small roll, and push it into the gap with your fingers. To square of the edge because we would like the gap to be as square as possible, take an old bank card and an engine square and cut the card square. This you use as a scraper and to clean out the excess clay. Once this process has been completed you will have a perfectly square edge. This clay is polished with Ram wax along with the rest of the mold.

following images shows the results:
gap with clay applied

gap with clay applied

Polishing the assembly is now a matter of apply 5 to 10 layers of Ram wax this is done so that you don’t miss anything and also if there is imperfections the wax will close and build up the items in layers leaving a perfectly flat, error free surface. Use a soft cloth and just apply and polish, it goes pretty quick. Images shows the results so they can speak for themselves.

no gap

Wax on

Wax off

In the next installment we will look at the laying up the composite mold.

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