Fillets and Fairing for the Ice Box

Once in place all the inside corners of the ice box were bonded together by laying a 4” wide strip of 6 oz fiberglass cloth atop a large fillet of epoxy thickened with cabosil (West 406 filler.)

Using 6oz fiberglass cloth over thickened epoxy to structurally join the ice box panels. 

The three butt joints (floor, forward wall, and ceiling) were filled with thickened epoxy and then covered with a 3” wide strip of fiberglass cloth.

Once cured the epoxy and fiberglass combination created structurally sound, watertight joints with a rough faces and irregular edges.    If left in this state the fiberglass joints would be difficult to clean and aesthetically unpleasing. 

Time for fillets and fairing. 

Fillets equate to filling an angular inside corner with thickened epoxy to create a nice even radius between the two faces.

Round on of  fairing and fillets applied.

Fairing is laying thickened epoxy (or other fairing compound) atop a rough or irregular surface in an effort to smooth the surface and hide any irregularities.

For the ice box project I used West Systems Epoxy thickened with a generic brand of micro-balloon filler (similar to West Systems 410).  This type of fairing filler adds little strength to the joint, but it sands easily and creates a smooth even surface.

Round one of fillets and fairing after sanding with 80 grit paper.

When applying fairing or creating fillets I prefer to begin by spreading the wet epoxy out scrap piece of cardboard, approximately one foot square, similar to a painter’s pallet.  Spreading the epoxy out extends the working time and working off the “pallet” creates less mess on the spreaders.

Various spreaders used in ice box project.

The choice of spreader is dictated by the dimensions of the surface to be faired or the size of fillet to be created.  Unable to find a spreader to match the fillets I wished to create in the ice box, I cut down a larger plastic spreader to the desired size. (small yellow spreader on left in image above.)

Another method of applying epoxy to a corner for creating fillets is the “icing bag” technique.  Place the thickened epoxy into a thick walled plastic bag (or two).  Cut an opening slightly smaller than the fillet you wish to create in one corner of the bag.  Start with a small opening; it can always be made larger if needed.  Twist the top of the bag to seal. Apply pressure to bag or continue to add twists to the top to force epoxy out the small opening.  I’m certain there are better descriptions of this technique with images and videos available on-line.  I chose not to use this method for the ice box because the desired fillets were very large.

Large fillets in ice box will make cleaning easier.

Applying fairing and using the spreader to smooth out the fillets is akin to icing a cake.  To carry the icing analogy further… just as the world has cadre of pastry chefs and artists that can create wonders with icing, there are individuals with the ability to efficiently and deftly apply thickened epoxy to a surface and create long, flawless fillets.  My skills have not yet evolved to this point (doubtful if they ever will.)  If you desire additional instruction in applying fairing or creating fillets, then again suggest searching the internet or youtube.

Each application of fairing is followed by a round of sanding.  The first and second rounds of fairing, I used 80 grit sand paper to quickly remove excess material.  On the third and final round of fairing, I used 80 grit paper to eliminate a few rough spots then switched to 120 grit.

Three rounds of filling and sanding complete.  Now read for primer.

The plan is to paint the majority of the interior of the box prior to installing the aft wall.  This will create two rounds of fairing and painting, but I believe the finished product will be of higher quality if the painting is not done while hanging into the box from above.

Three rounds of filling and sanding completed.  Now ready for primer.

The next step is to fit the aft wall of the ice box in place so it can be painted prior to installation.  It is also time to begin work adding insulation to the lid.

More images and notes from this on-going project as available in the Ice Box Rebuild Photo Album.