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Q1 Plans Chapter 3 Page 3-10

Apply Skin Barrier Cream

Do not start a large layup if tired. Get some rest and do it when fresh. It's best to have three people for any large layup, two laminators and one person to mix epoxy. Be sure the shop is clean before you start.

Take the recommended health precautione (discussed later in detail) using gloves or barrier skin cream. Get your grubby, old clothes on or at least a shop apron. Make sure that your tools are clean from the last layup and ready to use. Your working area should be between 60°F and 90°F. Best results are obtained at 70 to 75°F. Below 70°F the epoxy is thicker making it more difficult to wet the cloth. Above 85°F, the possibility of an exotherm is greater.

Step 2: Cut Fiberglass Cloth

The fine points of glass cutting have been covered on page 3-3. Remember that there isn’t any requirement to cut accurate dimensions. Cloth dimensions are given well oversize. You scissor trim them as you go, while laying the cloth up. It is a good ides to keep two pair of scissors, one clean and in the glass storage area and one in the shop that gets epoxy on it. After cutting, roll or fold the material: keep it clean and handy for the layup.


Prepare Foam Surface

Step 3: Prepare Surface

The only difference between layups over different materials is in surface preparation. The layup over Foam will be covered here since you will be doing more of it, and other surface preparations will be covered separately.

The foam surface is prepared by leveling uneven areas with a sanding block and brushing or blowing any dust off the surface. Use a compressed air or vacuum to remove dust.

Now is the time to accurately check that the foam core is the correct size, shape and contour. Refer to the section views of the part - be sure your core looks exactly like that on the section view. Lay a 12-inch straightedge spanwise on all critical areas of the flying surfaces (see sketches pg 3-13) and be sure you don’t have any high or low places or joggles. Measure any areas that involve fiberglass buildups to check for correct depth. Build up is 0.009 inch per ply for UNI and 0.013 inch per ply for BID.


Step 4: Mix Epoxy

Mix epoxy when you need it, not before. Micro, dry micro, and flox will be required at various stages of the layup. Mixing and composition details were covered on page 3-5. Apply a coat of micro slurry to the foam surface before the first glass ply is laid over it. The slurry can be poured on the foam and spread thin with a squeegee or it can be brushed on with a brush. Fill any dings or gouges in the foam core with dry micro.


Step 5: Lay on the Cloth

Lay on the cloth in the specified orientation. Pull the edges to straighten the cloth out and to remove wrinkles. Maximum strength and stiffness is obtained if the fibers are not wavy or wrinkled. If the cloth is to be applied around and into a sharp corner, you will find the job easier to do if the fiber orientation is at 45° to the corner. Don’t get depressed if the layup looks like a hopeless mess at this point. Press on with patience and things will work out fine. To remove wrinkles, study the direction of fibers. Follow the fibers to the outeredge of the cloth and pull on the outside edge. Pushing a wrinkle off the part is incorrect. Once the part is free of wrinkles use a squeege and make light passes from the center outwards to smooth the cloth.


Smooth Wrinkles


Step 6: Wet Out the Cloth

Wet out the cloth by brushing on a thin coat of epoxy. Do not use micro between plies of cloth. This may nut be necessary if there is enough epoxy under the cloth to be brought to the surface. This is done by "strippling," which involves a vertical stabbing motion of a paint brush over the cloth. This brings excess epoxy up from below to wet out the cloth, resulting in a weight savings as compared to adding more epoxy on top. REMEMBER, epoxy adds no strength beyond what is needed to wet out the white color of the cloth and fill air voids; any further addition of epoxy is only dead weight.

Where multiple plies are required, the first plies may be laid up wet and the excess resin brought up by squeegeeing and stippling to help wet out the middle plies. To do this, pour epoxy onto the part and move it around the surface with a squeegee. Your work will go much faster if you make the layup too wet, then remove excess epoxy with many light passes with the squeegee. Do not squeegee too hard, as this can starve the surface of micro and introduce sir. Continue to inspect for air (tiny white flecks or bubbles) and stipple or squeegee in more epoxy to remove the air. A handy squeegee can be cut from the flexible plastic found on a coffee can lid. You may also find a paint roller handy for spreading around the epoxy. Special stipple rollers are available at VariEze distributors. The final plies are ambitiously stippled and additional epoxy is applied sparingly. When in doubt - stipple it out.


When in doubt - stipple it out!

Q1 Plans Chapter 3 Page 3-11

As you wet out each ply, scissor trim to within ½” of any overhang (trailing edge, etc.). This ½” will be knife trimmed after the layup cures. If an overhanging ply isn’t trimmed, it lifts the edge up and makes a bubble. After scissor trimming, restipple the edges to be sure there are no voids. Wet the cloth beyond the trim line at least ¾” to allow easy knife trimming later.


Quickie Untrimmed Fiberglass Edge

Step 7: Squeegeeing

Squeegee out excess epoxy. This involves drawing a plastic or rubber squeegee over the layup as shown. Plastic squeegees (scrapers) are available at any paint store. If excess spoxy exists, it will be pushed off the edge of the piece. Remember, excess epoxy is much better on the floor than on the airplane. It is possible to squeegee too hard and make the layup too dry. If this occurs, the surface will appear white, indicating the presence of air. If this occurs, wet the cloth by painting on a little epoxy and stippling it down into the layup. The best quality layup is obtained if each layer of a multilayer layup is squeegeed. The excess epoxy which is pushed off the edge can be recovered and returned into the cup. This is easily done by catching the epoxy on the squeegee and scraping it on the side of the cup.

The finished layup should appear smooth and green so that the weave of the cloth is clearly visible, but not so dry that any area appears white in color. If you’ve done an excellent job, the weight of resin will be about 2/3 of the weight of cloth used.

To check if there is too much epoxy in the lsyup, pull a squeegee across the surface, stopping before you reach the edge. Lift the squeegee up and look for a large “ridge” of epoxy where the squeegee stopped. The ridge under the top ply indicates that the layup is too wet and you should spend time with the squeegee to remove epoxy off to the sides.

Don’t hesitate to use your stippling roller or brush on an area after squeegeeing. Some places are not suited to the use of a squeegee and the dry brush or roller must be used to expel the excess epoxy. On a given layup, about ½ of your time should be spent stippling or squeegeeing.


Quickie Squeegee Fiberglass


Step 8: General Inspection

After you have finished the layup, take a few minutes and give it a general inspection for trapped air, dry glass, excess epoxy, and delamination. It is much easier to correct these things while the layup is wet than to repair the cured layup. Also, have someone else inspect it. usually a different person can find air flecs or bubbles that are missed by one inspector. Carry a good light around for the inspection. Glance the light off the suriace at various angles to look for airflecks. If any air is visible, stipple it out. Be sure the overlaps on the edges are perfect. If, due to a-sharp corner etc, you have a problem eliminating an air bubble, use one of the following two methods; (1) Lift the cloth up off the foam, trowel some wet micro into the troublesome area, add more epoxy as you stipple the cloth back down. (2) Add excess epoxy over the bubble, cover the surface with Saran wrap (thin plastic wrap) then push firmly outwards to force the air out to the sides. The Saran wrap will seal the surface to keep air from being drawn in. This method will force the cloth to stay down, even around a sharp corner.



Step 9: Preliminary Contour Fill

Certain areas, like over the spar and a along the trailing edge (see cross—section views) require a dry micro fill. It is preferred to apply this fill within 2—3 hours of finishing the fiberglass layup. However, where the micro filler obscures the structure underneath, like over the spar cap, FAA inspection should be completed before dry micro filling. Areas like the trailing edge where the structure can be inspected from the other side should be filled while the layup is still tacky (within three hours of the layup). If you wait until the layup cures, you will have to sand the fiberglass surface to a dull finish before applying the micro. So, mix up a "dry" micro mix and trowel it into the low areas while the layup is still wet and save the work of sanding where feasible.



Step 10: Cleanup

Brushes can be used two to three times if after each layup they are washed with soap and water. Wipe excess epoxy off with a paper towel. Wet the brush & work soap into all fibers by mashing it into a bar of soap (Lava brand is best). Rinse with hot water and repeat 3 times. Be sure they are dry before next use. We generally use a cheap brush (approximately $2.00 to $4.00 per dozen) and discard after two or three layups. Clean squeegees the same way.

If you use skin barrier cream (Ply No. 9) the epoxy and cream will wash off easily with soap and water. When you get epoxy on unprotected skin, Epocleanse is used to remove the epoxy. Both of these products are available through RAF distributors and are listed in the bill of materials. Once you are sure your skin is clean, wash again thoroughly with soap & water, even if your hands were protected with plastic gloves. If you get epoxy on tools or metal parts, clean them with acetone or MEK before the epoxy cures.