Plug Building for Fiberglass Molds

Its funny how we do things that we think are not only the right way but the only way only to find out later that there are better ways.  Years ago, when I first discovered the use of dry foam, ( No I had no experience with surf  boards), as a medium for plug construction, I thought that I had found the perfect plug building material.

I easily carved out complex structures in a fraction of the time that it used to take when I used plaster and wood.  Then my bubble burst.  I finished carving the foam for my new plug, covered it with resin and sea glass from the hobby store and let it cure.

To my surprise, when I was applying bondo and glazing putty to level the surface of my plug, the plastic putty knife that I used easily went through the surface of my plug.  It was then that I realized that the outer skin of this plug was too weak and needed re-enforcement.

I fixed this problem by removing the thin layer of glass that I used to cover the foam and applying a 1/8 inch layer of bondo over the entire surface of my now less than pretty plug.  Since this episode, I have always used foam in my plug construction but I always took that extra step with shaving down the foam and covering it with a layer of bondo before I start the final finish.

Recently, I began to evaluate my plug building procedures.  While my tried and true method described above never failed me, I wanted to try something new.  I recently was building a plug that I wanted to move quickly with.  After carving the foam, I went ahead and decided to cover it as it was with 1 ½ ounce chopped mat and resin.

I remembered when I had my bad experience with this method I had used very light material from my hobby shop.  The 1 ½ ounce mat worked perfectly.  It provided a very solid surface to work with without adding excessive size to the plug that I had carved from the foam.

I basically did two things differently with the foam.  The first thing that I did was thoroughly saturate the surface with resin.  The second thing that I did was use a much heavier chopped mat to cover the plug.

I always read and research fiberglassing techniques.  I had not really researched or evaluated my plug construction techniques for years.  This “new to me method” saved me a TON of time and materials (bondo).  I don’t believe that this way of plug building affected the quality of my final product at all.

You might want to try this method for your next project.

Till next time…


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