There of course are several ways to go about building a basic structure to use for the basic shape.  This video gave lots of good ideas and examples of materials that are relatively inexpensive.

The second part of the video shows some of the actual fiberglass work.  This video of less than eight minutes does not nearly do justice to the amount of work and effort that went into finishing this project!  It was great that the author documented his work and shared with all.  This was a major project that is not for the faint of heart.

He does a very good job explaining the process and materials used in this construction. Every project is unique, however. When discussing the thickness of the fiberglass skin, there are many variables that determine the finished strength. The number of layers to use is dependent on the amount of underlying support structures, part geometry, and required load bearing capacity of the structure. Some areas may need to be stronger for impact resistance and structural loads.

The video author discusses only using epoxy resin with Styrofoam as opposed to polyester resin which will react with the Styrofoam.  Polyester resin can be used if separated from the Styrofoam with an additional layer.  While I have only seen it advertised, there are new spray on primer materials available to cover the Styrofoam and allow polyester resins to be utilized afterward.

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Chopped Strand Mat

The chopped strand mat is made up of random glass fibers held together with a light binding material.  A good pair of scissors can cut the glass into manageable sizes, though the scissors will be dull when you are finished.  The chopped strand mat can also be torn by hand.  This leaves a “feathered” edge to create nice transitions between the patched areas and the existing surface.  Pieces that are cut will leave a silhouette that will show and may require other methods to make it disappear.

The first thing that I checked was to make sure the glass was compatible with the epoxy resin.  The package told me so, but I also did a small test sample to ensure that the epoxy would mix with it, was workable, and would harden properly.  Testing away from the actual part can save many potential headaches and pitfalls.

Applying the glass and resin is relatively easy.  Thoroughly mix some resin and apply it to the properly prepared surface (clean, dry, and sanded).  Tear off an appropriate size piece of glass and place it on a piece of cardboard.  Use a cheap paintbrush to get the glass wet with resin.  Flip the glass over, and wet the backside.  The glass will go from white to transparent on the cardboard.  Now lift the glass from the cardboard and apply it to the area with the resin recently-applied resin.  Use the brush to push it down against the surface to get as much contact area as possible.

Additional layers can be applied on top to build thickness, making sure to create a nice transition and limiting air bubbles in the laminate.

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One of the considerations that needs to be taken into account is that the ratios are different and the glass and resin are more compacted by the process. Using the same layup schedule would result in a thinner laminate that is lighter weight and uses less resin. One drawback to this is that the cross sectional area is less, usually resulting in a loss of stiffness. This can be regained by increasing the core thickness to compensate for that loss and to restore overall panel thickness.

Infusion processing does require specialized equipment, consumables, and materials. The resins need to have much lower viscosity(flow like water). The core and glass need to have holes and channels for the resin to flow. A bag needs to be created to cover and seal off the laminate to the mold with out ANY air leaks. The mold needs to be able to be sealed to the bag and be airtight. A high vacuum needs to be able to be drawn on the bagged mold to move the resin. The vacuum pump or venturi needs to be able to achieve a minimum of 28 inches of mercury.

The basic process is that the mold is gelcoated abd skinned with a good, low-shrink resin and chopped strand mat. Then layers of dry glass are added. Coring is placed nice and tight and glued if needed. And the final layers of glass are placed. During the process, any gaps in coring or glass will “bridge” where the vacuum doesnt pull them down, and solid resin will fill them. So good fit is very important. The the bag is placed and sealed after auxililary runner strips are added and resin feed hoses are placed. The perimeter vacuum channel is plumbed to the vacuum pump.

Air is removed from the laminate for a good amount of time before the resin lines are opened up and resin flows into the part (do not forget to catalyze it). This is part of the art of flowing resin to fill the whole laminate with resin before an area gets cutoff from the vacuum or the resin begins to harden. There are some tricks and practice is key.

Resin is stopped just before fill and hopefully resin doesnt run into the vacuum line too far, but that is what resin traps are for. The vacuum is left running as the part hardens and gets to full cure in a couple of hours.

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