A word of warning!

Both fiberglass and talc have been used as fillers in body work, in combination with either polyester or epoxy resins. Working with fiberglass warrants precautions to avoid inhalation.

The Occupational Safety and Health Administration (OSHA) has a work place standard for fibrous glass because the fibers slide by the defenses of the respiratory system and become deposited in the lungs.

Styrene, a respiratory irritant, is often used in making polyester resins. Epoxy resins cause allergic sensitivity reactions on the skin. Some epoxy resins produce an asthma-like condition.

Spray painting after fiber glassing or using other surface preparations may cause a number of air contaminants to be released into the environment of a body shop.

Lead and zinc chromates are common primer pigments that can cause lung irritation if inhaled and skin irritation on contact. These pigments have been implicated in causing cancer.

Solvents present in primers and paints may cause respiratory irritation. Solvents may also affect the blood, liver, kidneys and central nervous system. Polyurethane paints for automobile exteriors may contain chemicals that can cause an asthma-like condition.

I bought a bunch of cheap crappy ½” paint brushes (for .35 cents each), use them and throw them away.

I use these cutters for cutting my glass mats, it seems to hold out better then standard scissors.

Gloves – surgical cheap and easy, you can’t beat it.

Prep:

• Clean the surface area of the body that you are going to work on, I use a cleaner/degreaser (Castrol Super Cleaner).  Anytime you add fiberglass (a secondary bond) you are relying upon the adhesive quality of the resin and your new surface for their strength.
• Lay newspaper down.
• Have plenty of pre cut piece ready to use.  I find that I never have enough, so with experience I now have many different sizes to choose from when I glassing.
• Put on the gloves, and mask you are ready to work.

Glassing:

I mix the polyester resin in a coffee can (since my wife goes through a can every few weeks – I am happy to replace the old can – it gets messy).  Add the hardener, and start working!

• Spread the resin on the surface with the paint brush
• Lay down the fiberglass mat
• Brush on more resin

Tips:

Wear a mask... what’s the use in building a car if you’re not around to enjoy it.  I did not use a mask at first (I am to macho for that) and whenever I glassed I would wonder why the next day I had this horrible headache… I now wear a mask.

Craig Nadeau - Repairing the small air pockets

I had an aircraft body mechanic over on the weekend. She gave me tons of information related to the bodies of our cars. I will start by saying that not everyone will agree with what she offers but airplanes fly alot higher and faster than Diablos.

First, the NAERC body is built entirely from "10 ply" fabric and is 6 plys thick. Apparently the 10 ply is the strongest of the fibergl *** fabrics. Even the center console, seats and dash are made the same way. She said that the strength would exceed the requirements for many light aircraft.

She told me that the correct way to repair the small air pockets that exist below the gel coat is to die grinder them open and then just use resin to fill them.

Bondo will work but will not work as well. She said you simply apply it with a popscicle stick and build it up in several layers.

The gel coat is mostly just a colored resin product. So long as there is no contamination between the gel coat and the fabric layers (incredibly rare), there is no reason to remove the gel coat to perform body work. Also, there is no reason to re apply the gel coat o­n top of the body work, you treat it the same as any surface, prime and paint.

Please note that the information I have provided came from "my research & experimentation, working experience with people knowledgeable on building homebuilt aircraft's, speaking with tech reps of fiberglass product manufacturers and of course technical info sheets gathered from anywhere and everywhere I could obtain them". Also, to advise everyone that they should gather as much info as they feel they need to make their decision - not base it on one persons' info. As I already mentioned I know very little but am always glad to assist if I can.

Fiber Glassing Methods - by Ernie

Bonding Fiber Glass Doors Skins Together:
The question was asked about how and what type of materials do you need to bond the fiberglass door skins together…

The glass door skins aren't that heavy but require substantial adhesion just the same.

Epoxy/polyester resins, both are brittle without a supporting matrix. Epoxy resin allows for more flex than polyester. Supporting matrix are fillers, such as glass balloons, phenolic powder, chopped fiberglass, etc.. Use these as fillers not as an adhesive!

Here's a few products you might look into for bonding your 'glass door skins over your stock doors:

3M Automix SMC/fiberglass panel adhesive part #8219; This is a 2-part urethane adhesive use to bond FRP ('glass) body panels to each other and to metal frames - though the metal needs to be primed with a good 2-part primer (DP!!) 30 minute work time - handle the part in 2 hours and cure time is 24 hours

Duramix Universal structural adhesive part #4125; This is a flexible urethane adhesive for bonding plastic add-on parts like spoilers, flares, ground effects. It's provides a tough, flexible bond that resists cracking. 10-minute work time sets up in 30 minutes and cures in 4 hours. "Duramix" had been purchased by 3M in August of this year 2002. I haven't heard if 3M plans on keeping Duramix products separate from their 3M products.

SEM makes a multipurpose adhesive, #39957 that bonds different composites, 'glass, aluminum and many types of rubber. I don't know how thick this material is.

As with these suggestions, I ask that you please do further research by asking the appropriate tech rep, gathering the tech sheet data etc., before making your decisions.

Also, inspect the door skin to check consistency between 'glass skin and steel door skin. There may be larger gaps that require a thicker type of adhesive or a non-sag type. Never bond 'glass using adhesive to a bare steel panel!!!

To comment about DynaGlass

This is a fiberglass reinforced "body filler" not to be used as an adhesive!!! It will crack, the same as plastic fillers. Don't use these as adhesives.

You don't need to drill holes into the steel for better adhesion - you'll be losing surface area -which you need as much surface area as possible to aid the adhesion factor. Just sand the metal with #80 or #180 grit sandpaper (dry - don't ever sand bare metal using water!) Preferably with a DA sander but hand sanding is satisfactory - just make sure there are no shiny spots left on the steel. Wipe clean with lacquer thinner a few times to ensure its contaminant free.

As for the bonded 'glass panels surviving - I don't believe it will last in the long run due to the different expansion characteristics - eventually you will start seeing fatigue cracking and stuff. This has been my experience. Lightweight stuff like hood scoops seem to last a bit longer because they're lighter - though the hood vibration could cause the bond to prematurely crack if a poor adhesive was used - such as plastic filler employed as the bonding agent. Of course, being on the top surface it gets the most heat from the direct sunlight causing it to expand and contract more so than glued on 'glass door skins. Color of the car makes a difference also. Very dark colors are not recommended - lighter colors are better.

Check with a 3M tech rep for their suggested 2-part primer. I like to use PPG's DP epoxy primer!

Can vibration cause the glass body cap to crack prematurely?

My findings on the stress cracking of fiberglass caps that are used on rebodying cars are not due to vibration primarily - especially if one uses an adhesive designed for the part and its usage.

It comes from the lack of torsional rigidity. For example, on a convertible, you can brace, triangulate, etc., a frame structure to virtually eliminate linear load stress; meaning if you inspect the gaps at the door and then apply force on the front end or rear, if the reinforcement was fabricated correctly you wouldn't find a door gap change weather loaded or not.

Torsional rigidity is something else. I've found the only way to completely eliminate the twisting action of the vehicle is to build a complete roll cage such as you see in a "real race cars" - thus you also take away from the appearance and practicality of the car for street usage. It is the twisting motion of the vehicle when you go in and out of driveways that is the culprit of the stress fractures and sometimes complete delimitation of the body cap!

Even on factory built convertibles you will sometimes find stress fractures in the lead seams on the tops of the quarter panels. Even the GTO convertible that our shop recently finished restoring had the tops of the quarter panels where we releaded the seams stress fractured due to the going in and out of our shop for delivery to the upholsterer and just getting the mechanical problems solved. We repaired it once already and has been holding up but it will fracture again!

You can duplicate the efforts of the aerospace industry by applying the adhesive with rivets, which will obviously be a stronger bond and most likely last longer than just the adhesive bond alone. One mistake some people make is when using rivets you must be sure to use the same material rivet as the anchor material is made of e.g., steel body=steel rivets, aluminum body=aluminum rivets.

When looking to purchase adhesives I suggest you look at the tech sheet for the product to ensure the adhesive has the strength properties required for your usage. There are three basic strengths you must observe:

Peel strength = just as the name implies, peeling the bonded panels apart at one end

Shear strength = pull and push loading. Imagine sliding bonded panels in opposite directions.

Tensile strength = the pulling apart of two bonded panels

I'll give you an example of an adhesive that I use. You've probably heard of the "Stud Gun, Spitznegal" etc.. This is a device that will weld a metal stud onto the metal panel of a car to assist in the pulling out of a dent. Then you cut off the stud and grind the remaining head of the stud from the panel. This is an improvement over the drill a hole and then screw in the dent puller, then weld up the holes.

I use an adhesive that has tremendous tensile strength - which I apply a drop of the adhesive onto the panel I need to pull on - wait a few moments, stick the metal stud into the drop of adhesive - wait a few more moments. I then take my stud puller and attach it to the stud and pull out the panel. Then I take a metal spreader or scraper and just peel/scrape the adhesive drop and stud off the panel. Nothing to grind off (which is a bad thing to do to metal panels) or holes to weld up.

This is a great adhesive for this but definitely wouldn't use it for bonding flares and stuff!

So, take your time and research the material you need.

If I may offer a primer on how adhesives works (I feel this may help in your search for the appropriate adhesive)

Adhesives need to perform two contradictory functions during their operating cycle. When the adhesive is applied it needs to make essential contact with the surface or using the industries term "wet" the surface.

The adhesive needs to be mobile enough to flow into all the crevices and corners of the substrate. If the adhesive doesn't wet well onto the substrate, poor adhesion is the corollary. A good example of poor wetting is the way beads of water run off on a freshly waxed car.

Once you achieve good wetting, the adhesive needs to cease flowing and become solid. This is called setting or cure. There are a variety of ways to achieve this. Heat catalyzed adhesives solidify when they cool down. Structural adhesives used for permanent assembly of composites cure through chemical reaction (cross linking). The final cured adhesive becomes a solid, tough, stable medium that tenaciously bonds two surfaces together.

But you must understand that even the best adhesive may fail if placed in unworkable joint design or if applied 2 inches or more away from the intended bonding area. The most important rule is to have adequate surface contact area.

One other note is that in the real world the loads placed on the bonded panels hardly ever consist of one stress type, but rather two or more stress load: Peel, shear, compression and tensile loads. But the design of the application can be optimized to minimize unwanted loads.

Types of Adhesives

One part urethanes are usually used as sealants. These products cure by ambient moisture absorption and their cure rates can vary in relation to humidity. These cure slower than two part urethanes.

Common applications for one part urethanes include marine, bath and shower products and in construction.

Acrylic adhesives are less common than other adhesive families, at least in my experience. Acrylic adhesives do offer the fastest ambient room temp cure while at the same time offering a suitable work time. They will also bond difficult substrates with the minimum amount of surface preparation. They're easy to use and will work just as well even if there is a slight variation in the mix ratio. These products are highly flammable and emit a certain odor.

Two-part urethanes adhesives have just recently been given more exposure. These are available in a variety of cure rates and physical characteristics; from flexible to very hard. Two-part urethane adhesives are usually best for bonding incompatible substrates (different materials). They don't have the best heat resistance so keep in mind that you may not want to use adhesive in your engine compartment applications.

Epoxy adhesives have a wide application usage. It cures at ambient room temp or with a mild heat bake cycle. Using heat to aid the epoxy curing significantly improves the bonding properties. It has low shrinkage during it cure cycle and is resistant to water and other environmental conditions. The disadvantage of epoxy adhesives is that it usually requires meticulous surface prep and the mix ratio has to be exact!!

My understanding of your mount setup is that it is a joint design. Can it be bolted together somehow? My concern is that even the best adhesive is likely to perform poorly when used in an application that is designed for mechanical fastening. Mechanical joining methods like bolting, welding, riveting are great at carrying tensile and peel loads but adhesives usually perform their best when loaded in shear and compression.

If you're interested in converting joints that use the conventional fasteners to one designed for adhesives - it doesn't require too much.

You will need to consider stress loads; tensile, compressive and shear can be easily visualized, but peel loads might not be too obvious. A peel load is created when bending occurs in one or both of the joined materials. This generates an extremely concentrated area of load stress at the bond edge. Tensile loads are often accompanied by or eventually turn into, peel loads. This is especially true for flexible substrates.

If I may offer some things to take into consideration for your adhesive design usage:

• the operating temperature and exposure to the environment
• the expansion and contraction characteristics between the dissimilar materials
• the strength of an adhesive in one type of joint design may be entirely different when the same adhesive is used in different joint designs
• thinner applications of adhesive layers will produce stronger bonding joints than thick adhesive layers. There must be enough of an adhesive layer to wet the intended bonding surface
• make it a point to design the joint for predominantly shear and compressive loads
• use the maximum bonding area

It is important to test the adhesive for its validity in a particular application. A common error is to evaluate an adhesive product using a testing method that is quite different from the actual usage.

Testing should be done using the same materials as the real thing. Conduct the testing under the same environment and temperatures, which it will actually be used.

In reference to your bonding the perforated angle iron to the fiberglass, it would be advisable to use solid angle iron because you have more surface bonding area.

Also, if possible, it would make a much stronger bond if you bonded a sheet of metal or aluminum that would cover at least twice the surface area of your angle iron, onto the 'glass, then bond the solid angle iron onto the metal sheet.

Just a thought or perhaps I've misinterpreted your design?

I just wanted to inform you that you can recoat polyester resin base 'glass with polyester or epoxy resin. You can recoat epoxy resin based 'glass with epoxy but "not" with polyester resin. FYI

Carbon Fiber

Carbon Fiber layup can be composed of a variety of "weaves" depending upon the part and it's usage etc:

• Carbon Fiber "Plain" weave usually is employed when fabricating lightweight non structural parts.
• Carbon Fiber "Twill" weave is slightly stronger than the plain weave and is commonly used as the "cosmetic weave" due to the unique appearance desired by those who wish to display their carbon fiber parts. You'll see this weave used on hoods, after market interior trim, engine compartment accessories etc.,
• There's also the Carbon Fiber "basketweave" which has twice the fiber density of the plain and twill weaves. This particular fabric weave is superb in structural applications.

I believe the roof and doors on the "real" Lambos are aluminum whilst the other components are of the composite variety. Carbon Fiber construction especially the method employed in the construction of structural components is going to vary from each manufacturer from hand layup to applying C-fiber over shaped aluminum panels to autclaved epoxy pre-impregnated fabric to carbon fiber sandwiches; this is a method where carbon fiber is employed on both sides of a supporting structural panel, e.g., a fiberglass honeycomb panel, used primarily for maintaining lightweight but with tremendous rigidity. I do recall a few years ago that my instructor mentioned that in order for carbon fiber to be impact resistant, it must be plied with fiberglass (composite?). I don't know if that is still true due to technological progress.

The clear coating that you see is from the epoxy resin. As with any hand layup it is very difficult to control the resin saturation onto the fabric, be it carbon fiber or fiberglass but in either case the resin is what gives you that clear look. You can even sand the resin after it as cured and clear coat it with automotive 2-part urethane clear then sand/polish it to achieve that extra glass smooth depth. I've done it for some customers that had carbon fiber pieces for their race car.

It is the automotive clear coat that you sand and polish - of course you will sand the resin prior to topcoating with the automotive clear! You can also purchase carbon fiber board from Tap plastics - comes in sheets cut to your specifications - be forewarned - it won't be cheap! Tap Plastics recommend using spray adhesive for the c-fiber board to cover your aluminum part - then they recommend going over it with their resin. I have just clear coated directly on top since the piece we made was strictly comestic anyway. Im' helping my brother-in-law with a project of his - which is to cover his aluminum airbox with the c-fiber board and we're using the Tap Plastics process.

You will have to clear coat the c-fiber coat a few times though - sand and clear, sand and clear, sand and polish. The reason for this is because the initial clear coats you apply will not saturate the weave tows (intersecting fibers) completely and will leave you with what looks like fish eyes - when actually it is the indentation of the clear filling the gaps between the weaves. Then you'll have to sand the clear as flat as possible then reapply the clear again to allow for more film build. Then when you come back to sand - it will have enough film build that you can then polish to a nice finish. You'll have to see some of the sample pieces I've done - not just c-fiber but other painted items. By the way, I've painted many a unique item - from pearlescent on dishwasher door, oven, refrigerator and trash compactor for a interior designer doing a custom kitchen, to custom built railings for a stereo company painted in glow in the dark neon, and the most unique is the walls of an entire room done in dark gray metallic and clear coated with neon, candy and pearl music notes and related symbols for another stereo company - a week later someone keyed the walls!!! What a shame. I'm doing some R&E on the flexing limits of the new urethane clears without the flex agent additive - I don't believe in using flex agents anyway.

"If you are planning on fabricating a lightweight non-structural part from carbon fiber, perhaps something comestic, I would suggest that you use epoxy resin. You can use the marine type epoxy resin for the cosmetic pieces but when it comes to fabricating a structural part you MUST use a carbon fiber specific epoxy resin and ask a professional for advice. You will need to understand the layup process of incorporating the different type of fiber weave such as unidirectional and multi-directional, when combined can offer substantial strength but again you will also need to understand the directional stress factors of the structural part you are fabricating. Again, this is from my own personal research and experimentation. I make no claim on being an expert on carbon fiber."

Forming Thermoplastic:

For those of you interested, here is basic info, procedure, and techniques for forming thermoplastic.

Transparent acrylic plastics will get soft and pliable when they are heated to their forming temperatures and can be formed to almost any shape.

Before you heat any transparent plastic, be sure to remove all of the protective masking paper and adhesive from the plastic. The plastic should be free of dust and dirt. If the plastic is dusty or dirty, wash it with clean cool water and rinse it well. Dry the sheet thoroughly by blotting it with soft absorbent paper towels. Do not wipe back and forth or up and down because of the possibility of scratching the plastic if there is any residual dirt that was missed. I like to use Scott brand blue shop towels.

A couple of notes:

- Wear cotton gloves when you're handling the plastic to prevent leaving finger marks on the surface.

- Never use hot water or steam directly on the plastic to heat it because it will cause the acrylic to become milky or cloudy.

For small forming jobs, such as headlight covers, you can use the kitchen oven. You can also use infrared heatlamps, like the ones used in paintshops to fastdry paint spot repairs. I have a single filament infrared lamp about 28 inches in length. This seems to work well for me.

Heated acrylic plastic will mold with almost no pressure when heated to its forming temperature. So, the forms used can be made of a variety of simple constructed materials. For simple curves you can shape forms from plaster, plywood, or pressed wood. (I may try balsawood as an experiment.) For complex or compound curves you'll need to use reinforced plastic or plaster.

Hot acrylic plastic will conform to any waviness or uneveness, so be sure the form being used is as straight or smooth as possible. To help alleviate this, sand the form smooth and cover it with a soft cloth like flannel or felt.

The acrylic plastic should be large enough to extend past the trim line of the form being made. Also, you must have a method of holding the heated plastic against the form as it cools.

Here is the procedure I used for making headlight covers for a home built airplane. This method would work if you wanted to make acrylic headlight covers for the stock Z headlight buckets.

Fill the headlight bucket with plaster so you have enough material to start sanding to shape. I use #80 grit sandpaper on a pad and sanded the plaster until I was close to the desired shape. I then switched to #180 grit sandpaper and did the final sanding to shape.

I then wiped the mold (form) with a damp sponge and blot dried it with papertowels. Then I took my clear acrylic sheet, which was larger than the mold and balanced it on the form. My heatlamp was warmed up and I placed it over the plastic and the mold. After a few minutes I watched as the plastic started to soften and actually draped itself over the headlight bucket. Then I shut the heatlamp off and allowed the part to cool. (Do not force cool, allow to cool naturally.) You can also use a kitchen oven for this. After the plastic cooled, I scribed my trim line and pulled the plastic from the form.

Acrylic Plastic:

If you are planning to make a acrylic plastic lens to cover the entire stock rear expanse after removing the stock tail lights and finish plates - you wouldn't need to use a form mold for this. There is a subtle curvature but due to the length of the plastic panel I feel you wouldn't have a problem with bending the plastic panel to fit unless you're going to use a 1" thick or thicker piece of plastic.

This insulating foam you mention, is it the stuff you spray out of a aerosol can and then it expands and then hardens when dry? If so, No, you cannot use this for form molds. It will melt due to the heat required to form the acrylic plastic.

Here some heating info:

Acrylic plastics become thermoelastic (stretchy) at about 120 degrees F -
so watch out where you store your acrylic plastic sheets!

Forming simple curves require approximately 235 degrees F -
while stretch/mold forming require approx 285 degrees F using a 0.125 sheet thickness

If you decide to use 0.250 sheet thickness:

Forming simple curves require approximately 275 degrees F -
while stretch/mold forming require approx 300 degrees F.

Be sure to keep an eye on the plastic sheet as you are forming because every heat source is different in its displacement of heat. You may have to move the heat source or the part you're heating further away or closer to each other depending on how the part is reacting.

Always do a test panel!!

Finally, do not rub plastics (such as your tail light lens) with a dry cloth - like after you've washed the car and you are wiping it down with a terrycloth towel. If done over a period of time without dressing the plastic it will cause scratches and result in a dull finish. Also, you'll build up an electrostatic charge that will attract dust particles to the surface.

My suggestion would be to polish the lens with a good plastic cleaner follwed by a plastic polish if your lens are slightly dull. Use a soft cloth (used, clean, baby diapers from a diaper service work well) Then follow up with a good wax or sealant (no glaze!!! - stuff doesn't work well to me. If you're lens are pretty dull, then you'll need to get out some sandpaper, sand down, and get some rouge for plastic polishing and a polishing wheel on a bench grinder and get to polishing! Or another alternative instead of using a polishing wheel is to actually spray an acrylic clearcoat on the lens after you've cleaned the part well, then sanded with a grit appropriate for your clear coat you will apply.

Thanks so much for trusting me in what little I know. I need to inform you that the information I provide is based solely on my personal experience, training, observation/opinion and R&D. Although I make every effort to provide you with accurate info I may not always fully understand the background to the questions and therefore not able to promise/guarantee the accuracy of my answers/information. So, I 'm asking that you please accept my answers/info as a guide and I urge you to PLEASE make additional inquiries before you pursue a course of action to resolve your situation and not just based on the information I provide. Thanks again for allowing me share info with you guys.

Hope this helps,

RacerX - (Ernie)

Fiber Glassing Ideas - by Ron Boudreau

I thought this might be useful, our fiber glass guy used to use cardboard tubes to make arches. The tubes can be cut in half and are easy to conform to curves and odd shapes. They also absorb resin and become part of the structure.

This is a picture of my old Formula V top mold. It now resides in the woods and is giving mice a home, but you can see how he stiffened up the sides and flat surfaces. He used this technique on all his master molds and a lot of the parts he built, it is strong and easy to do without adding a lot of weight.