glasair 1.2 newsletter

SCOPE

The purpose of this section of the Manual is to explain the construction techniques required to build the G1asair airplane.It describes in detail standard lamination procedures. ge1coating. and riveting. This section should be used as a reference while proceeding through individual assembly sections. Time spent in preparation and organization will greatly enhance productivity and give safe high quality assemblies. Reasonable skill with basic shop tools and power machines is assumed. Pay close attention to the following helpful hints.

~ STODDARD-HAMILTON

AIRCRAFT, INCORPORATED MODEL

GLASAIR TD ASSEMBLY NAME

FABRICATION TECHNIQUES REVISION DATE VOLUME

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TOOLS AND MATERIALS REQUIRED

1. 3/8" drill motor 2. Small drill bit set 3. No. 10, 20, 30, & 40 drill bits. 4. Saber saw . 5. Assorted files 6. Hack saw 7. Rotary file for drill 8. Chalk line 9. Plywood 1/2" sheet

10. Level (carpenter's) 11. Razor trim knife 12. Gram scale, 0-500 grams

(available at most drug stores) 13. Syringe 1-5cc without needle 14. Paint brushes, 1" & 2" 15. Tape Measure, 12' 16. Straight edge, 8' 17. C-clamps 18. 12" ruler 19. Centerpunch 20. Carpenter's square 21. (20) clecos, 1/8" diameter

h22. Machine stop countersink tool and a 1/8 diameter 100 degree countersink bit

23. Putty knife 24. Cleco pliers 25. Plumb bob 26. Vise 27. Masking tape 28. Flashlight 29. Unwaxed mixing cups and tongue depressor mix1ng sticks 30. Sanding blocks and sand paper; grit: 50, 60, 80, 180, 220,

320, 400, 600, and 900. 31. Body putty (Ultralite Plastic Filler No. 394, made by

Dynatrin/Bondo Corp. or equivalent) 32. Acetone 33. "Pop rivet gun" for pull rivets 34. Modeling clay 35. Non-toxic particle masks 36. Vapor spray mask 37. Power buffing compound, and buffer attachment for drill

motor 38. Wax - paste 39. Ventilation fan 40. Trouble light

~ STODDARD-HAMILTON

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Access to

1. Bench grinder 2. Spray gun with narrow nozzle (small siphon units with

disposable paper cups work fine) 3. Bandsaw 4. Right angle drill attach 5. Rivet gun, bucking bar, and small compressor

NOTE: This list is not "exhaustive and only lists the essential tools required. Builder preference will dictate what other tools will be used.

SPECIAL TOOLS

FIGURE (L)

Cut the handles of two 1/2" diameter varnish brushes to fit into some 3/8" diameter tubing. Cut and bend a piece of tubing to the dimensions shown above. Insert the brushes into the ends and crimp in place.

~ 5TODDARD-HAMILTON

AIRCRAFT. INCORPORATED MODEL PAGE

GLASAIR TD 2-3 ASSEMBLY NAME


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BRUSH EXTENSION

'1r

SEAM TAPE APPLICATOR

FIGURE (ii)

Cut a piece of 1/2" diameter wood dowel 60" long. Bevel one end 45 degrees as shown above. Drive a hole in the other end and press fit a 1/16" diameter finishing nail into it so the pointed end is sticking out. This applicator is used to position the seam tape on the horizontal stabilizer leading edge.

CLOTH ALIGNl1ENT PROBE

FI'GURE (iii)

From 1/8" thick wood or plexiglass cut out the probe to the above shape and dimension. Make the tips sharp enough to poke through fiBerglass cloth.

FOAM ROUTER TOOLS

FIGURE (iv)

Bend a medium sized nail to the above dimensions. Cut the head off first. This tool is used to route out the foam core on wing ribs, etc.

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FIBERGLASSING

WHAT IS FIBERGLASS?

Glass fiber is produced by drawing single fibers of special glass (largely silicon, calcium, and aluminum dioxides) into very small diameter strands. The glass itself has very high tensile strength, little corrosion resistance, and is vulnerable to attack by both acids and alkalies. However, when the properties of glass fioers are properly complemented with the corrosion resistance and toughness of res in, the end product is a strong, lightweight. corrosion-resistant laminate. During the lamination procesS', resin is impregnated between the glass strands or fibers using various saturation techniques.

FIBERGLASS PRODUCTS

Glass fiber is woven into many different styles or types of weaves. We use two different styles of bidirectional type weave. One is a loose weave style and the other is a tighter weave which is our standard fiberglass cloth. Fiberglass products come in various forms such as: bidirectional cloth ~idirectional cloth, chopped strand mat, woven roving, mill' f~bers, and seam tape. The Glasair is constructed from 2 different styles of bidirectional cloth unidirectional cloth mill fibers, seam tape, and mat.' ,

FIBERGLASS LAMINATION

The secret to fiberglass lamination is impregnating enough resin between the glass fibers to remove all the air present in the cloth, but not over saturating the cloth. Fiberglass lamination is an art and takes some practice. The idea is to remove any air bubbles present in the cloth which will detract from the strength and corrosion resistance of the laminate. In an attempt to completely saturate the cloth (i.e. remove all of the air bubbles) over saturation may result. This results in a heavy resin rich laminate. A middle ground is desired. Not under or over saturation, but proper cloth saturation.

~ STODDARD-HAMILTON

AIRCRAFT. INCORPORATED MODEL ASSEMBLY NAME

GLASAIR TD FABRICATION TECHNIQUES REVISION DATE VOLUME

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FIBERGLASS STORAGE

Fiberglass products should be stored so they will be kept clean and free of water absorption. Glass that is dirty, or that has absorbed moisture, will retard resin pick-up and may result in a defective application. Glass that has been wet, or that is dirty, should not be used.

RESIN PROMOTION

Our resin uses a 3 part catalytic system. This system consists of a methyl ethyl ketone peroxide or MEKP catalyst, cobalt naphthenate or CoNap promoter, and dimethylaniline or DMA accelerator. The catalyzed resin mixture consists of resin, CoNap, DMA, and MEKP. The promoting agents are CoNap and DMA.

NOTE: At high temperatures (80°_ 100°F) as listed below DMA is not required to cure the resin and may be left out of the promotion step.

WARNING: CoNap should never be mixed directly with MEKP catalyst.A violent reaction will occur which m~y result in fire or explosion. CoNap should be stored separately from the catalyst.

Before the resin can be catalyzed it has to be promoted. No noticeable change will occur in the resin upon promotion except the color will change. Unpromoted resin has a shelf life of approximately 6 months. The shelf life of promoted resin is slightly less, depending upon storage conditions. Resin is promoted with CoNap, and then DMA. Resin should only be promoted in 1 gallon quantities at a time, because promoted resin has a shorter shelf life than unpromoted resin. From the 1 gallon master batch of promoted resin smaller quantities are taken as needed and catalyzed with MEKP just prior to use. The master batch of promoted resin is convenient and economical. The resin supply lasts longer and the resin doesn't have to be promoted each time before use.

Use a plastic syringe graduated in increments of .1 cc to measure the CoNap and DMA. Use clean plastic containers that can be sealed, preferably with a closable spout. Promote resin in one gallon quantities as needed to the following ratios:

TEMPERATURE : 65-85° F 80-100° F RESIN: 1 gallon 1 gallon (goldish-brown in color) CONAP: 5 cc 5 cc (purple in color) DMA: 3 cc o cc (orangish-yellowin color)

~ STODDARD-HAMILTON

AIRCRAFT, INCORPORATED

MODEL ASSEMBLY NAME REVISION DATE VOLUME PAGE

GLASAIR TD FABRICATION TECHNIQUES I 2-6

NOTE: Be accurate when measuring the promoting agents. A small error will drastically alter gel time. Thoroughly mix each ingredient into the resin scraping the sides and bottom of the mixing vessel.

CUTTING FOAM PARTS

All full size templates, due to the fact that every airplane is different, are only approximate outlines of the parts. It is therefore advisable to cut all foam bulkheads, ribs, and spars a little oversize to allow enough material to fit the part to the assembly.

The foam is very easily cut and sanded. We supply a white 4.5 lb/ft~ and a light brown 20 Ib/ft.3 and 40 Ib/ft.3 foam. Most foam parts are made from the lighter 4.5 lb. foam. The 20 and 40 lb. foam is only used when high bearing loads are present.

PREPARATION OF FIBERGLASS PARTS

MOLD LIP r--~

~SANDING BLOCK

CORRECT INCORRECT

FIGURE (v)

Many of the fiberglass parts, when removed from the mold, have a small lip remaining as shown in Figure (v). This lip should be removed by sanding, as shown. Sand only enough to remove the lip.

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GEL TIMES

Gel time or pot life is the time it takes the resin to set up in the container after proper and thorough mixing with promoters, accelerators, and catalysts. Gel times can be adjusted significantly by varying the amounts of these materials. Gel times also will vary significantly with changesin ambient temperature and humidity.

NOTE: The gel times given below will vary from the actual working time of the catalyzed resin.

Working time is the time after catalysis and before the start of gelation, when the resin can be applied successfully to the fiberglass cloth.

Due to many variables affecting gel time the working life can vary considerably from the gel time.

Factors affecting the working life of the resin:

A. Higher temperatures will result in a shorter working life whereas cooler temperatures will result in a longer working life.

B. Warm resin will have a shorter working life whereas cool resin will have a longer one.

C. Large batch sizes will tend to have a shorter working life.

D. Large heat sinks (landing gear struts) will extend working life.

E. High humidity conditions will lengthen working life.

F. Thick laminates will decrease working life.

G. Brisk winds will increase working life.

H. Direct sunlight will shorten working life.

~ STODDARD-HAMILTON


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-- - -- --

-

TYPICAL GEL TIMES -

Amount Amount % Catalyst Resin Catalyst 50° F 60° F 70° F 80° F

. 75% 100 gm . 8 cc 1-1.5 hr 50-60 min. 20-40 min . 15-20 min

1.00% 100 gm 1.1 cc 45 min. 30 min. 20 min. 10-15 min

2.00% 100 gm 2.1 cc 30-40 min. 20 min. 15 min. 10 min OJ:: less

NOTE: The above gel times are only approximate and may vary significantly due to the above mentioned conditions. Be careful at first by using the longest (slowest) gel time to get a feel for the actual working time under the existing conditions.

WARNING: Under no circumstances should more than 2.0% catalystmixture be used. Do not use less than the recommended minimum amount of catalyst (.75%) or the resin may never completely cure resulting in a reduction of strength.

We have found that when laminating the most common mixing ratio is a 1% catalyst ratio. This ratio works for most situations, but there are exceptions which will be up to the builder to decide.

~ STODDARD-HAMILTON

AIRCRAFT.INCORI'ORATED MODEL ASSEMBL Y NAME REVISION DATE VOLUME PAGE

GLASAIR TD FABRICATION TECHNIQUES I 2-9

STANDARD LAMINATING PROCEDURES

CUTTING TIlE CLOTH

Take a piece of bidirectional cloth and examine it. The weave goes in two directions and will easily shift to match any compound curved surface such as a sphere or the like. Bidirectional cloth has approximately the same strength in both directions of the weave of the cloth. Unidirectional cloth has all its strength in one direction and has virtually no strength in the other direction. The two weaves or directions in the cloth are at 90° to one another. Fill is defined as the direction in the cloth with the lesser percentage of strength. Warp is defined as the direction of the cloth weave with the greater percentage of strength. So in bidirect~onal cloth warp strength is slightly greater than fill strength, whereas in unidirectional cloth warp strength is much greater than fill strength. To gain full structural advantage of fiberglass cloth, its orientation to load paths is important. Orientation to load paths is defined as oias. Bias is measured in degrees from the longitudinal axis of the pattern. We use a 45° or 0° bias. See Figure (vi).

FILLFILL WARP

WARP

(45° BIAS) (0° BIAS)

FIGURE (vi)

All cloth is cut on the 45° bias with excepcions noted. Cutting bidirectional cloth on the 45° bias has certain advantages not only related to strength. The edges of 'a piece of cloth

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when cut on the 0° bias tend to separate and cause obvious problems. Cloth cut on the 45° bias alleviates this problem. When forming the cloth over compound curves it adapts to contours much more easily when cut on the 45° bias.

Be careful with long narrow cloth strips cut on the 45° bias. If stretched they will become too narrow to be used for seams or splices. All cloth dimensions allow for some narrowing due to stretching But even with some excess built into the dimensions the cloth can still be stretched too narrow. It is hard to try to stretch the cloth strips back to their original width once they have been elongated. The long narrow seam strips for the wing, stabilizer, and fuselage fall into this category.

NOTE: These strips could be cut a little "more" oversize to allow some excess if problems arise.

SURFACE PREPARATION FOR BONDING

When bonding to fiber glass surfaces proper surface preparation is required.

NOTE: When bonding to outside mold surfaces sanding preparation is always required. l~en bonding to inside laminate surfaces sanding preparation may be required.

A green colored coating called PVA may be present on the outside of parts supplied. PVA is used to keep parts from sticking to the molds when new molds are being broken in. PVA can easily be seen on parts that are ge1coated. On surfaces next to the mold that are not gelcoated (such as the landing gear struts, leading edge of the wing, and middle portion of the horizontal stabilizer) the PVA may be barely visible. Check closely and remove any PVA with water and paper towels prior to bonding. Dry thoroughly.

Any surface that is smooth from being next to the mold must be sanded with 80 grit sandpaper when bonding is required. Ge1coat, when present, must be completely removed with sandpaper when bonding is required. Be careful when sanding not to go through any of the fiberglass layers such as when bonding the stabilizer to the fuselage.

When bonding to the inside surface of the composite shells (those surfaces not against the mold) sanding preparation mayor may not be required. With resins such as ours, oxygen actually

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inhibits chemical curing of the surface exposed to the air. This creates a gummy surface layer with hardened resin below the surface. With time, however, these surfaces will cure completely even when exposed to air. Soft gummy surfaces do not require sanding whereas hard cured surfaces do. To test whether the surface needs preparation sand a small portion of the surface with sandpaper. If the sandpaper gums up quickly preparation is not needed. If the sandpaper does not gum up preparation is needed. This means sanding the whole surface to be laminated until it is dull or has no shine. The surface gnly needs to be roughed up, not any material below the surface.

o not sand into the fiberglass layers thereby weakening the structure.

After the surface has been prepared properly, it must be kept clean and dry until laminating can be started. Dust, moisture or traces of oil which come in contact with the surface may act to inhibit the cure, thus preventing a good bond.

NOTE: Most inside surfaces will not require prep sanding unless the kit sits for a long period of time (8-12 months) causing the surfaces to harden. This does not refer to smooth outside mold surfaces.

MIXING THE RESIN

1.) DETERMINING THE MIXING RATIO

After the resin is promoted it requires MEKP catalyst to cause gelation and then final curing. Many variables affect gel time as described in the Gel Times section. Discretion is advised when determining the mixing ratio of resin to catalyst. If temperatures are high use the minimum amount of catalyst. If temperatures are low and the lay up is small, use the maximum amount of catalyst. When the conditions are indeterminate, always use the minimum amount of catalyst allowing the slowest gel time. The builder will have to use his own judgment as to what ratio to use.

2 . ) ACCURACY

When mixing the catalyst with the resin, be accurate. Small deviations will greatly alter gel time. Use a gram scale purchased from any health food store or drug store and a small plastic syringe. Plastic syringes without needles can be

~ STODDARD-HAMILTON


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purchased from most drug stores. Syringes with a capacity of 3 cc graduated in .1 cc increments work fine for measuring the catalyst.

WARNING: Be careful with the MEKP catalyst. Contact with eyes must be avoided.

3.) BATCH SIZES

Once the mixing ratio is determined the batch size will have to be determined depending on the size of the lay up. In the instructions many batch sizes are given. Some batch sizes are not given but left up to the builder to determine. These are described here.

We recommend using resin in small quantities of 50 grams, 100 grams, and 200 grams. Small quantities are preferred over large quantities except where noted. This is especially helpful when first becoming familiar with gel times and laminating techniques. A typical step will read, "To start with, mix a 50 gram batch of resin to get a feel for how much resin will be needed for this step. Once this is determined mix in small amounts only enough resin to complete this step". Fifty grams is a good quantity to start with. In time the builder will get a good "feel" for how much resin to mix up for a laminate depending on temperature, size of laminate, and number of layers.

There are several reasons for using small quantities of resin. Small batches limit the area that can be saturated with resin. In this way more time is allowed for laying up a laminate. If a large area is 1ayed up all at once the whole laminate will begin to gel at once. By dividing the lay up into sections by the use of small batch sizes, it will also gel in sections. With each additional batch that much more time is added to the total lay up time.

NOTE: Be careful; if a part gels before it is saturated it must be reworked. Remove the unsaturated layer by sanding with roughsandpaper. Do not sand into the previous layer. A small percentage of air bubbles in a laminate is acceptable, but should be avoided if possible. The parts have a large safety factor to allow for some air bubbles although not a lot. Once the area is repaired, start over.

The advantage to small quantities is that once the area is saturated, the next area can be worked even if the previous area starts to gel. This way the builder never gets ahead of himself.

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Sm~ll batch sizes allow enough time to do a good job before the resin gels. Large batches of resin tend to cure faster than small ones b~cause of the heat concentration due to the larger mass of resin.

4.) MIXING

Mix thoroughly and scrape the sides and bottom of the mixing vessel while mixing the catalyst into the resin. This mixing step should take approximately 30 to 60 seconds. Mixing should be done to entrap the least possible amount of air. After mixing let the resin sit a couple of minutes to de-air. Use unwaxed paper mixing cups and wooden tongue depressors for mixing the resin. Any clean container will work for a mixing vessel. Do not reuse containers until the resin in them has cured because the leftover uncured resin in the containers will upset the gel time of the present batch.

SATURATING THE CLOTH

1 .) PROPER CLOTH SATURATION

The proper amount of resin to be applied when saturating the fiberglass cloth is described as when the cloth looks wet, rich in color, but is without puddles. The cloth pattern should still be visible on the surface and not glazed over. White, or pale dry areas need more resin.

NOTE: Once the laminate begins to cure it is too late to add more resin to "touch" it up.

2.) MINIMIZING AIR BUBBLES

Air bubbles in a laminate detract from its strength and corrosion resistant properties. Air bubbles may be minimized by the following practices:

A. Avoid violent mixing of the resin while catalyzing it. However, thorough mixing is required.

B. Apply a thin coat of resin to the area to be laminated first before laying the cloth down. Then lay the cloth

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down, rolling the cloth into the resin. Application of resin to dry surfaces inevitably causes air bubbles.

C. When laying up a cloth layer start in the middle of the strip and work to the outer edges. Use firm but not excessive pressure when brushing or squeegeeing the resin into the cloth. Excessive pressures may fracture existing air bubbles and make them more difficult to remove.

D. Always eliminate all air bubbles from one ply before proceeding to the next ply.

3. ) SATURATION TECHNIQUES

On flat surfaces such as bulkheads, ribs, etc., a squeegee technique is used. To begin with when laying up a part, a splice, or a seam, apply a thin layer of resin to the area to be laminated. This will help saturate the first layer of cloth with resin. Lay the cloth down as neat as possible making sure it is centered on the seam or part with no wrinkles or folds present. Then brush on more resin getting the entire lay up wet. With a rubber squeegee, spread the resin out using medium pressure, raking across the surface of the cloth removing any bubbles, air pockets, or excess resin. Be sure not to add too much resin, causing the laminate to float. Be careful not to shift the laminate on the part when raking, but still apply enough pressure to remove any excess resin.

On surfaces where the use of a squeegee is impossible, a varnish brush is used. The majority of the surfaces on the Glasair will use the varnish brush technique for saturating the cloth. Some seams will require a brush extension to allow access, such as the wheel pant assembly, vertical fin, and leading edge of the horizontal stabilizer. To saturate the cloth using a brush, a dabbing or stippling technique is used. First wet the area to be laminated and apply the fiberglass cloth. Then apply the resin with the brush being careful not to put too much resin on, because excess resin is hard to remove with a brush. Once the cloth is wet, start removing the air bubbles using a rapid stabbing (same as dabbing or stippling) technique with the tip of the brush. The air will bleed through the cloth eliminating the bubbles in this manner.

NOTE: On large lay ups consisting of long narrow strips or large areas, do not WE't the entire surface at once. Work in small sections. Saturate one section at a time, then move on to the next section. This way the cloth is sure to be saturated before

~ STODDARD-HAMILTON

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gelation. If a section starts to gel behind the one in work it is not ruined because it is already completely saturated. In this manner the builder never gets ahead of himself.

During lamination air bubbles may disappear and reappear as if from nowhere. Any trick or method is fair in eliminating air bubbles. Finger, sticks, etc. work well too.

4.) APPLICATION OF FIRST LAYER AND ADDITIONAL LAYERS OF FIBERGLASS

After the surface to be laminated is properly prepared it is ready for the lay up process. Prior to laying the first layer onto the area to be laminated a coat of catalyzed resin needs to be applied. Spread this on with a varnish brush. The idea is to completely saturate the cloth with resin. With resin applied to the area to be laminated prior to laying down the cloth the first layer is saturated more easily. Laying the cloth down on a dry surface will obviously create more air bubbles and make saturation time longer.

NOTE: Let each layer become tacky to the touch before applying the next layer. When laying up additional layers of cloth there is no need to wet the area again because the surface will still be wet from the previous layer of cloth.

NOTE: If the previous layer has dried and cured, then the area to be laminated will have to be wetted again to aid in cloth saturation.

NOTE: Exceptions to wetting the area to be laminated first are when laying up large flat laminates such as the firewall bulkhead, and any laminates that are layed up on an aluminum plate. These laminates will become resin rich or over saturated if wetted first.

GELATION VERSES CURE

Upon mixing the promoted resin with the MEKP catalyst an exothermic reaction takes place. An exothermic reaction is one in which energy in the form of heat is released as a result of a chemical reaction. The catalyzed resin will go through various stages of hardness. These stages are gel, exotherm, cool, green cure, initial cure, and cure. There are no rapid

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hardness changes except when the resin begins to gel. At this stage the resin begins to change from a liquid to a solid. Depending on the mixing ratio, temperature, batch size, etc., the gel time can vary anywhere from 10 minutes to 1.5 hours. To gain approximately 75% strength, the resin must cure for 16-24 hours. This is called initial cure. To gain full strength the resin must cure for 3-4 days at 74° F. Green cure is defined as when the resin is hard or stiff enough to allow trimming off excess cloth with a knife. Green cure is obtained or reached anywhere from 15-45 minutes after gelation, depending upon temperature.

NOTE: When a batch of resin begins to gel in a container it will begin to develop a paste like consistency for approximately 2 to 3 minutes, and then suddenly solidify. Just before the resin begins to gel it will be unworkable on cloth, but there will still be enough time to save the brush with acetone solvent. When the resin goes off or starts to gel, acetone loses its effectiveness to dissolve the resin, so be sure clean-up is accomplished before the resin gels.

While laying up a laminate special attention should be given to the time elapsed (i.e. time from initial resin catalysis to present). "Working time" is the time after catalysis and before the start of gelation. Pot life is the time specified in the Gel Times section. Actual conditions may vary due to· the many variables affecting gel time. Therefore, working time will not always agree with quoted pot life times.

A "cooking timer" would be a help to keep track of elapsed time.

CLEAN UP AND DISPOSAL OF WASTES

The best solvent to use with resin and gelcoat is acetone, which is available at most hardware stores. As noted in the GELATION VERSES CURE section, acetone loses its effectiveness as a solvent when the resin and gelcoat begin to gel, so be careful to start clean up before the resin starts to gel.

NOTE: If the resin begins to gel while still on the brush, the brush may be ruined unless immediately immersed in acetone.

Use acetone for cleaning resin from brushes, squeegees, hands, etc.

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WARNING: Acetone is highly flammable. It is harmful to the eyes and skin and should not be inhaled. It is also poisonous if swallowed. Carefully read all safety precautions on the outside of the container.

Care should be taken when disposing of catalyzed resin. An exothermic reaction is set in motion when catalyst is mixed into resin. Enough heat can be generated in this reaction to cause a fire under the right conditions, depending upon the depth of the resin in the mixing vessel and the amount of catalyst used.

WARl~ING: Do not throwaway catalyzed resin until it has gelled, exothermed, and cooled. This will prevent any fires being started in trash cans or waste bins.

We suggest pouring excess catalyzed resin onto plastic sheets outdoors in a shaded area away from anything flammable. Make sure that it forms a thin layer only, to keep the heat levels down. After the mixture gels, exotherms, and cools, fold up the sheet and discard.

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Q-CELL, MILL FIBER, AND Q-CELL MILL FIBER COMBINATION MIXTURES

Q-cell mixtures are made up of catalyzed resin and Q-cell powder.Q-cell mixtures are used primarily for sealing foam panels, and filling holes and corners.

When mixing to use as a sealant for foam panels add Q-cell powder to a batch of catalyzed resin until a thin milkshake consistency is achieved. This is called a "wet mix". When sealing bulkheads and the like apply a thin layer of wet Q-cell mixture to the foam. Apply only enough to seal the foam. Use a squeegee to rake the mixture over the foam when applying.

When making a Q-cell mixture to use as a filler add Q-cell powder until a thick milkshake consistency is achieved. This is called a "thick mix".

Mill fiber mixtures consist of catalyzed resin and an appropriate amount of fiberglass mill fibers. Mill fibers are very short fiberglass strands. Mill fiber mixtures are used when strong adhesion bonding is required. To mix add mill fibers to catalyzed resin until a slightly less than paste consistency is achieved. The consistency should be thick enough to stay on a wood tongue depressor without running off, altheugn still be fully saturated with resin.

Also used is a combination mixture of both Q-cells and mill fibers. Add Q-cell powder and mill fibers in equal quantities to a batch of catalyzed resin. The consistency should be similar to a wet Q-cell mixture. The mixture should be well saturated and not dry. This mixture is used for seaming together the trailing edgesof the elevators, flaps, ailerons, and rudder.

GELCOATING

All of the exposed surfaces on the Glasair kit are gelcoated except for the seams, leading edges, and landing gear struts. These areas must be prepared and gelcoated by the builder himself. Gelcoating is similar to spraying enamel or catalyzed polyurethane, but can be sprayed much more thickly

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before it runs or sags. Cured gelcoat is quite flexible, tough, and will not peel like paint.

NOTE: Be careful not to scratch the gelcoat during construction. Protect the surface with paper and masking tape as required. When using the saber saw, tape the base of it to prevent scratching the gelcoat.

The composite shells are made first by spraying the gelcoat into the mold, then laminating on top of it. The gelcoat and resin are both styrene based, so they actually become an integral part of one another. When touching up the seams and splices witn gelcoat from the outside, the same process happens. The gelcoat on the Glasair is 12-14 mil thick. It serves as an ultraviolet ray barrier and its white color prevents heat absorbtion from the sun. Heat will ultimately weaken the composite skin. Dark trim lines are fine as long as they are kept fairly small, however we recommend the use of light reflective colors for trim. Gelcoat is compatible with any type of trim paint. Prep the surface to be trimmed by sanding and keeping it clean.

NOTE: The shelf life of gelcoat is approximately 6 months. Store in a cool dry place.

LANDING GEAR STRUTS

To become familiar with gelcoating techniques we suggest gelcoating the landing gear struts first.

NOTE: Prior to gelcoating the landing gear struts they are wrapped with a fiberglass cloth laminate, filled with body putty, and then sanded smooth. This procedure is described in the fuselage assembly section.

To spray the gelcoat with conventional spray guns some thinning may be required. To thin the gelcoat add just enough acetone so the spray gun will push it. Thinning is only necessary to allow the spray gun to function. Before thinning the gelcoat add catalyst to the gelcoat in a 2% ratio (2.1 cc catalyst to 100 grams gelcoat in the same manner as done with resin). Be ready to immediately test the spray gun to see if it will push the gelcoat. If not, add some acetone to thin the gelcoat. Leave enough room in the spray gun pot to add some acetone thinner. Some practice spraying may be necessary. The gelcoat never runs out perfectly smooth on the surface as do normal paints. It will have to be sanded and buffed to be glossy.

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NOTE: The catalytic rate of gelcoat is similar to resin. If temperatures are 75° F or higher be v~ry careful that the gelcoat doesn't gel in the spray gun or ~t will be ruined. We suggest spraying small batches of gelcoat to alleviate this if spraying has to be done at these temperatures. It is recommended that spraying gelcoat be done on colder days (50-65° F). Pay careful attention to how long the gelcoat has been in the gun. Immediately after spraying dissassemble gun and clean thoroughly with acetone.

When the gelcoat has cured enough to run a brush over it without smearing (about an hour), take a foam brush and coat all the gelcoat with a thin layer of PVA. Remember PVA is green in color and water soluble. This will seal the gelcoated surface from oxygen so that it will cure with a hard surface. Be sure not to wait too long before doing this or the surface will not harden causing the sandpaper to gum up. A hard surface is required to sand and buff the gelcoat. Let the gelcoat cure 24 hours with the PVA coating before washing it off.

NOTE: If too much time has elapsed the PVA release won't harden the gelcoat surface. Use acetone to wipe off the gummy layerof gelcoat and let dry. The uncured gummy portion on the surface will come off with acetone. Acetone will not dissolve the cured gelcoat beneath the surface. In this way sanding can be accomplished.

Then wet sand the strut with 180 grit sandpaper. Follow wet sanding with 220, 320, 400, 600 grit and then buff with rubbing or buffing compound. Ditzler n~X-16 or equivalent works fine.

JOINTS, SEAMS, AND LEADING EDGES

The following techniques are very effective in creating quality feathered edges. With care the edges, joints and seams can be completely disguised.

~ STODDARD-HAMILTON


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8· TO 10" --1-h: SANDING 1" OVERLAP ~ ZONE

~ MASKING~t\....... V- TAPE

( -, PAPER

I ~ -

I I I I6.PVA 6"PVAI--- ......,~ZONE~ ZONE

FIGURE (vii)

STEP 1 Fill the joints and leading edges with body putty and sand smooth and flush before gelcoating. Wet sand an area centered on the joint 8-10 inches wide with 320 grit sandpaper (See the above figure). Sand the surface until there are no shiny areas present Do not sand any deeper than it takes to dull the surface. Wash with water and allow to dry.

STEP 2 Apply a thin coat of PVA 6" wide as shown above with a foam orush so that it overlaps approximately 1" onto the sanded area. The PVA will protect the surface from overspray and will come off later with water. Use paper and masking tape to cover areas not to be sprayed outside of the release area.

STEP 3 Spray the gelcoat onto the seam. Concentrate the gelcoat spray onto the seam joint area and allow the overspray to overlap onto the PVA zone Be sure to spray the gelcoat thick enough to allow for future sanding and buffing.

STEP 4 When the gelcoat cures enough to run a brush over it with-out smearing, take a foam brush and apply a light coat of PVA over the gelcoat and overspray area. Let the gelcoat cure 24 hours and then clean the PVA coating off with water.

~ STODDARD-HAMILTON


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NOTE: If the PVA was forgotten and not applied. use acetone to remove the gummy surface layer of gelcoat.

STEP ~ The surface should now be hard enough to sand without gumming the sandpaper. There should be approximately a I" wide green layer of PVA underneath the gelcoat where the PVA and gelcoat overlap (see Step 2). This green overlap area is a perfect indicator to show how far and how much to sand to get a perfect featheredge and matchup. Wet sand with 220 then 320 grit sandpaper until the green band of PVA disappears. At this point sand with 400 then 600 grit paper and then buff out with buffing compound .

NOTE: On areas such as th~ horizontal stabilizer and elevator tips sand and spray the entire tip. joint. and 3-4" past the joint.

After gelcoating the leading edges and seams. to give the plane a high gloss look wet sand lightly with 600-900 grit sandpaper and buff out using a power buffer and buffing compound.

NOTE: Any scratches. chips. or similarly damaged areas on the gelcoat surface may easily be repaired with gelcoat. Fill the crack with gelcoat. sand. and buff smooth. Make sure the surrounding area is freshly sanded and absolutely clean for the best results.

RIVETING

The essential tools for riveting are rivet guns. dies. compressors. and bucking bars. The rivet gun is used to deliver rapid. hammerlike blows that quickly drive the rivet when it is backed by a suitable bucking bar. Three basic types of rivets are used in building the Glasair; universal round head. countersunk flush head. and the blind pull type. For each type of rivet different techniques and tools are required. The round head and flush head rivets obviously require different gun dies. The blind rivets only require pop rivet pliers for pulling them. When using air rivet guns ear plugs are recommended.

~ STODDARD-HAMILTON


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DRILLING

For 3/32" diameter rivets use a no. 40 drill bit, and for 1/8" use a no. 30 bit. Proper hole size is essential in attaining maximum design strength. When a fastener does not fill the hole, it is the weak link in a chain of several fasteners. The holes must not be oversize. An oversize hole will not be filled by extra driving of a rivet. It will only ruin the rivet and the surrounding structure. Use only sharp straight drill bits. Defective drill bits create oversize holes. A rivet should just slide in with finger pressure only. There should be no looseness. When drilling keep the drill perpendicular to the surface being drilled. Also make sure when drilling that the parts to be drilled through are securely clamped together and aligned using cleco's and "C" clamps. For counte r s LnkIng the exposed 1/8" diameter rivets use the machine stop cO'lmtersink tool. Adjust it to the proper depth by practicing with a rivet on a scrap piece of material. When countersinking the 3/32" diameter rivets for nut plates, use a large drill bit if the proper bit is not available for the stop cO'lmtersink tool.

DRIVING THE RIVETS

G'lmS and bucking bars should be large enough to drive rivets in a reasonable length of time with minimum distortion to structure. AVDid using too many bursts because it will cause the rivet to work harden and crack. Driving a rivet should only take 1 to 3 seconds. When driving the rivets make sure that the rivet gun and bucking bar are perpendicular to the surface being riveted to keep from damaging th~ rivet and the surface finish of the part. When using the flush rivethead die on the cO'lmters'lmk rivets tape the die with masking tape to protect the gelcoat finish and keep the driving head from floating. The bucking bar should clear surro'lmding obstructions to allow the bucking surface to rest squarely against the tip of the rivet shank. Avoid having the point of contact too close to the edge of the bucking bar since it may slip off. Before a rivet is driven it should extend through the hole roughly l~ times the diameter. The driven head of the rivet must be formed to the proper size as shown.

~ STODDARD-HAMILTON

I AIRCRAFT. INCORPORATED

VOLUME PAGEREVISIONMODEL ASSEMBLY NAME DATE

IGLASAIR TD FABRICATION TECHNIQUES 2-24

f»»~ CORRECT CORRECT

FIGURE (viii)

RIVET REMOVAL

When removing defective rivets care should be taken not to damagethe surrounding structure by drilling off center to the hole. Before drilling centerpuncn tne rivet in the center of the manufactured head. Use the same size drill bit as the rivet hole to drill tne rivet out.

~~:~~ ~~~ r«<[f«(<3 HOLE TOO LARGE MIS-ALIGNMENT DIE NOT .L COUNTERSUNK

TOO DEEP

INCORRECT EXAMPLES

FIGURE (ix)

~ STODDARD-HAMILTON


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- --

TOLERANCES

There are many dimensions that are given throughout the instruction manual. Dimensions are given in either decimal or fractional form. All dimensions are in inches. The fractional dimensions given should have a tolerance of no more than plus or minus 1/32". All decimal dimensions given should have a tolerance of no more than plus or minus .030". We suggest procuring a scale that is graduated in 1/50 of an inch or converting the decimal dimensions to fractional equivalents when working with the decimal dimensions.

SHUR-LOK INSERTS

OUTSIDE GELCOATED SKIN

FILL WITH RESIN

",""-===::::j 1- -I--

11" DIA.

INSERT

UP

+ TAB

(REMOVE '---___ AFTER CURED)

I;

- _. -:1•••• ..J, II

I I ----, (REMOVE FOAM)

'------j SL607-3-7S

'---FILL WITH RESIN

TYPICAL CROSS-SECTION OF SHUR-LOK INSTALLATION

FIGURE (x)

~ STODDARD-HAMILTON


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Shur-lok inserts are used in several areas of the Glasair airframe to provide solid mounting points for fastening various components. These instructions detail a typical Shur-lok installation.

After the location for the fastener has been determined, drill a 1/2" diameter hole through the inner skin only of the composite structure.

With a foam router tool (such as a bent nail chucked in a drill motor), rout out the foam core 1/4" larger radially than the 1/2" holes, creating 1" diameter voids from skin to skin as shown in FIGURE (x).

NOTE: Make sure to remove all the foam from the skin surfaces to create a good bonding surface.

VENT AND FI LLER HOLES

ADHESIVE COATING

FIGURE (xi)

The SL607 Shur-lok inserts come with a disposable tab that has an adhesive coating on (1) side. Peel off the protective paper coating and press the tabs onto the inserts as needed. Make sure to line up the vent and filler holes with the slots in the insert. (See FIGURE xi.)

With the inserts stuck to the tabs, press the inserts and tabs into their proper locations in the structure. The adhesive coating on the tabs will hold the inserts and tabs to the structure. (See FIGURE x.)

~ STODDARD-HAMILTON

AIRCRAFT. INCClRPORATEO

REVISION DATE VOLUME PAGEMODEL


FABRICATION TECHNIQUES I 2-27

Mix up a batch of resin and fill a sizable syringe or the equivalent with it. Inject the resin into the 1" diameter voids in the panels around the inserts via the bottom filler hole until resin oozes out the top vent holes, as shown in FIGURE (x). Tape the holes closed with masking tape until the resin cures so it won't run out. Let cure and then remove the tabs and masking tape.

NOTE: Do not install any fasteners into the inserts until the resIn around them has fully cured. The 1" diameter voids can be partially filled with a combination mill fiber, Q-cell mixture before installing the inserts, to make injection easier if desired.

An alternate Shur-lok installation procedure that is used in the Glasair airframe construction is to dispense with the adhesive tab and fasten the Shur-lok directly to the component being mounted. The void in the airframe is filled with mill fiber mixture and the component is clamped in its proper position with the Shur-lok(s) inserted into the mill fiber-filled voids. This procedure is used when a very precise location of the Shur10k is needed.

~ STODDARD-HAMILTON

AIRCRAFT. INCOR~ATED

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