Instructions for making multiple wet lay-ups:

    Create a pattern from paper or light weight cardboard (cake box weight) of the area to be glassed, or place the nylon film (vacuum bagging material) directly on the surface area and free hand draw a pattern with a Sharpie" marking pen.

    Place your cardboard (or paper) pattern under the nylon film over a white or light colored bench surface. Trace the pattern to the nylon then remove the paper pattern. This will leave only the nylon material in place through which you will clearly see the traced pattern. Tape this securely by each end to  the bench surface using regular masking tape.

    

Click on picture to enlarge.  You may print a copy if you have a color printer.

    Using the pattern for size, pre-cut all layers of the glass slightly over size not being concerned with shape--only that the pieces are large enough to cover the area of the final pattern. Cut the fiberglass pieces with the bid direction correct for the application.

    Next, weigh the glass pieces to determine the exact amount of resin needed. Burt Rutan determined that the optimum ratio of glass and resin is 40% resin and 60% glass. If you mix an equal amount of resin + 10% it will work perfect for you every time.

    Lay the glass pieces over the nylon pattern completely covering the drawn pattern lines. It helps to use small pieces of masking tape on each outside corner to keep the layers in place as you build them up. This will keep the glass from shifting as you move the squeegee back and forth across the layers while letting the resin soak into the cloth.

Note: It should be obvious that your aircraft surface be properly prepared, clean and sanded with at least 80 grit sandpaper. Do not pre-apply resin on the aircraft surface before applying the pre-wet panel.  (See below)

    The styrene in the resin begins to evaporate quickly and the surface becomes sticky. If it is sticky when you attempt to apply the "panel" of pre-wet glass, it will be more difficult to put it into place. At times it may be necessary to pre-apply resin in the corners or areas that are recessed to aid in the removal of air from under the applied panel. You will need a "freshly wet" resin surface under the panel so that, as you work the surface with the squeegee, dry brush, or a rag wet with acetone, the trapped air can be moved to the edge or to a hole easily and quickly.

    Mix the resin and pour it over the fiberglass panels.  Move the resin with a squeegee back and forth over the entire surface until the pattern lines show completely through.  (You will be able to see every air bubble through the clear nylon film).  Now, lay the second pre-cut piece of nylon film over the wet surface and, using a clean, dry squeegee, force the extra resin and all the air from the layers to the sides of the panel.   You will also be able move resin from an extra wet area to a dryer one with the squeegee.

    When you are satisfied with the wetted panel, using large upholstery type shears, cut through the layers following the pattern lines.  It is important that you have pre-determined the position of and cut all the gussets, holes, or special cuts that are to be made before applying the panel.

    Make certain that you remove the layer of nylon film from the side that becomes the bonded surface. You don't want to find you have removed the wrong side when you get to the work area. (I have done that). Leave the other layer of nylon on as a "carrier" and as the surface that you will rub on to apply the panel. Once the panel is in place, use a squeegee, dry brush, or a rag wet with acetone to work the surface and remove the air from under the layers. You may also use a pointed punch to make bleed holes through these layers to allow air removal if necessary.  

    Do not remove the nylon until you are happy with the placement and position of the wet panel.

    Once the nylon surface is removed, begin to apply resin with a brush and work out any left over air. When ready, apply the peel ply material and wet it out completely checking for and removing any trapped air.

 Do not remove the peel ply until the surface is cured and not sticky. The peel ply can be left on and removed months later so there is no rush.  However, make certain that all subsequent glass layers are put on glass, not peelply.

To encourage the curing of the resin, I suggest you apply heat using quartz halogen lamps, regular light bulbs, or place the part in the direct sunlight. Caution: If air is trapped under the surface and you apply heat, the air will expand and leave you with air bubbles you did not expect.  If this occurs, you can drill small holes in the bubble as an inlet and a vent into which you can inject resin using a small syringe to fill the void.  Remember that air will expand as you gain altitude when flying.  That can create potential structural problems. Fill the voids!

   Recently, when helping Bruce Newlan in Napa, CA., we were able to cure the resin and remove the peel ply within two hours by encouraging the cure with heat lamps. This means that a lot of work can be done quickly when there is a need to do so.  Caution!  Heat can also be your enemy. Above 165 degerees the resin and glass layers can be damaged.  Be carefull !

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Happy glassing!

Question or comments can be addressed to me at:
Jerry Sjostrand
email to: gsjostrand@sierratel.com