Got holes to weld shut? Check out our dvd on welding. You'll find a couple of great techniques you can use to weld holes.
Which is better, a MIG or a flux core welder? Flux core welders work much hotter than MIG so warpage is much more likely.
Got safety equipment? Always wear ear plugs and safety glasses when you work. I also like the Mechanic's Gloves. Buy one size too small for a tight fit.
Removing ball joints can be a killer. Try drilling through the retaining rivets instead of cutting them with an air hammer, or use a die grinder to cut a slot through the top of the rivet then use the air hammer to finish removing the top.
Grinding welds is tiresome? Try stacking 3-inch cut off wheels - 3 deep - on your die grinder and using that to smooth welds. Works great.
Got a rusted nut that just won't budge? Try drilling through the side of the nut with a small bit then graduate up in drill bit size until you have drilled out most of the side of the nut. That will let you remove the nut.
Foam pad or wool pad? I use them both, but lately I"ve been leaning towards foam pads. They have been improved and may even work better than the old wool pads. They don't produce any lint either. A good thing when it comes time for clean up.
Which is better, dry sanding primer or wet sanding primer? Either will get the job done. You have to decide between dust everywhere or water puddles. I lean towards dry sanding primer.
I took a tip from those frequent cursing bike builders on TV and tried an electricl high speed mini grinder. It does a nice job smoothing welds on frames.
Can't stand the noise from an air chisel? Me neither. I rarely use one any more, opting instead for a die grinder with a 3 inch cut off wheel attached.
Cars built in the '50's had crappy fuel pumps. I often run into the problem of fuel starvation on these cars. The solution is to add an electric fuel pump inline to give the mechanical pump a boost.
Is a Mig Welder better than a wire welder? Yes, for the simple reason that a Mig Welder can weld thinner metals without the problems of burn through and extensive metal warpage.
Forgot to purchase some weld-thru primer? Try two coats of epoxy instead. You will still need to wire brush the spot welds for a clean weld.
I"ve heard all kinds of horror stories about bodies twisting and flexing out of shape when put on a rotisserie, especially when replacing floor pans. Personally, and that would be 30+ years of experience, I've never had a body twist or flex out of shape just because I cut out the floor pans. It is a different story if you need to replace the rocker panels, those are structural and the body will flex and twist when you cut them out. But, to ease your mind you can add supports inside the body to hold it rigid when on a rotisserie, and you can add door braces (Eastwood sells them) across the door openings for added strength. The only bodies I"ve ever witnessed flexing is convertible bodies. THOSE MUST BE BRACED BEFORE HANGING ON A ROTISSERIE.
I installed 3 point seat belts in a Mustang article in Auto Restorer and received a number of inquires about this conversion. You will find a number of 3 point seat belts kits out there for a lot of old rides.
Do you own a shrinker/stretcher device? If you plan to do much in the way of sheet metal repair this device is a must have. Check Eastwood. They have a good unit in their catalog.
We all know after market sheet metal parts just don't fit. Be prepared to do some hammer and dolly work to get them to fit and don't hesitate to consider moving or reshaping attachment points.
Sometimes parts just don't fit. Often the problem is due to the builder having tightened some of the bolts before all of the adjacent parts have been installed. Loose bolts on EVERYTHING can make fitting ill-fitting parts fit.
It ain't easy shrinking metal. Start by heating the stretch to a dull red. Then quench the area with cold water immediately. Repeat. Repeat as many times as necessary to remove the stretch. Don't worry about over working the metal. That rarely happens.
Locating spider cracking in a gel coat can be very difficult. I've learned to spray on a contrasting color over the suspected spider cracking area then lightly sand the area with 320. Any spider cracks show right up.
Previously published in Auto Restorer Magazine.
When old car guys think of fiberglass they instantly think of Corvettes. But gluing the old Corvette back together after several years of use and abuse isn’t the only occasion for breaking out the sticky resin. Many vintage rides have header panels, headlamp housings, rear body finish panels and trim pieces made of fiberglass or the new stuff, SMC, and every one of these parts is prone to the same maladies that infect old Corvettes, such as cracking, spider webbing and chunks missing.
Let’s start by explaining the difference between fiberglass and the new stuff, SMC.
Fiberglass, or FRP (fiberglass reinforced panels) has been around for many years. Older Corvettes (pre ‘80’s) are made of it, as are countless other items such as boats, surf boards, skis and ground effects for your kid’s Honda just to name a few. FRP panels are cast from molds and the easiest way to recognize FRP is to look on the backside of the object being repaired. The surface will be somewhat rough and the short strand fiberglass mat used to reinforce the panel will be noticeable.
In most cases a polyester based resin was used to form the panels which means repairs can be made using either a polyester or an epoxy based resin. The drawback to working with FRP is that the panels tend to become wavy once removed from the mold and that these types of panels never stop shrinking. Got surface cracks in the vintage Vette? That’s why.
The advantage to using FRP is that with a little skill and patience a good restoration enthusiast can make any part necessary to reconstruct everything from the hood on the old Vette to the door scoops found on the ’70 Charger.
SMC, or Sheet Molded Compound, is the modern day equivalent to fiberglass and has taken the place of FRP where casting automotive panels is concerned. SMC panels are made in compression molds, meaning the panel being fabricated is squeezed between an outer mold and an inner mold making the panel extremely smooth on both the inside and outside. Compression molding allows the panel to be formed without the use of a gel coat and offers a stronger, more rigid and smooth panel than FRP fabrication. If sanded the SMC panel will exhibit a marbled appearance and if broken will expose the short strand glass fibers imbedded within the compound. This is the best way to identify SMC when repairs are in order.
SMC is also a polyester based material but must be repaired using epoxy based resins and adhesives. By the way, don’t try spraying lacquer or enamel based products over bare SMC. SMC is formulated with a built in mold release (to speed up the molding process) and the chemical make up of the releasing agent can cause adhesion problems for non-catalyzed finishes.
SMC doesn’t really have any drawbacks, other than the layman’s inability to produce it. The good side is that SMC isn’t prone to the amount of shrinkage FRP experiences and the panels are as smooth as glass once removed from the molds.
Fiberglass – SMC repair rules.
Both fiberglass and SMC are repaired using the same methods. The basic difference as mentioned above is the type of resins used to make the repairs. When purchasing repair resin the can will state whether the contents are polyester or epoxy based and if the product is for use on fiberglass or SMC type panels.
The actual repair begins by recognizing and understanding the difference between a repair and the original piece. When this fender was first fabricated the entire piece was laid up in a mold and allowed to cure as a single, roughly 3/16-inch thick, layer of fiber reinforced resin. At this point the fender is as strong as it will ever be. Any repairs subsequently made to the fender could become the weak link in the panel so the first order of business is to insure whatever types of repairs we make to the panel are as strong as the original structure.
This starts by maintaining the strength of the panel and that begins by tapering the edges of the damage to prevent a build up of new materials around the repair. We don’t want the repair to be twice as strong as the original piece by piling on the resin and mat any more than we want the repair to be weaker than the original piece by failing to apply enough resin and mat. Second, the edges of the break must be cleaned up to eliminate panel stress caused by the broken fibers pushing against each other once the pieces are rejoined.
Not sure how much damage the panel has suffered? This can be a tricky problem. Tears, holes and cracks are often accompanied by delamination of the fiberglass layers. What may appear as a small crack in the outer surface may actually extend an inch or more over the backside of the panel. Consider how a rock hitting a glass can cause a small hole at the point of impact but blow out a very large circle of glass on the backside of the impact. That’s how delamination works. An easy way to determine the full extent of the damage present is to tap the area around the damage with the edge of a quarter. Try it, an audible difference can be heard between solid material and delaminated material.
Repairing the damage.
In the case of a break or tear the first step is to realign the damaged pieces of the panel. Since broken fiberglass tends to fray and leave jagged edges along the break line we begin by cleaning up the break with a die grinder. Getting rid of the rough edges allows the two pieces to realign. Don’t forget to do the coin test to determine how much delamination has occurred. Once solid material is found mark the outer borders of the good material using a marker. This identifies the actual width of the repair area as any portion of the panel that has delaminated must be ground back and removed.
Next use a grinder with a 24-grit disk to taper the repair area. Areas that have delaminated must be ground deep enough to expose and remove the delaminated material before beginning the taper.
The bulk of the work is being performed on the back of the panel. This is preferable in that the outer surface is left basically intact reducing the amount of cosmetic repairs required. In some cases this work must be performed on the outside of the panel with the only consequence being additional cosmetic work. Also notice the width of the taper. Our panel could have five layers or more of laminate. If each layer is ground back one half inch to form the taper the actual width of the repair quickly spreads to a minimum of five inches, or two and one half inches on either side of the break.
Tip: Grinding fiberglass is an unpleasant task. The fine dust created during the grinding process goes everywhere and gets onto everything. Dress for the occasion just like you would dress for spray painting, with a NOISH approved respirator, paint suit and latex gloves. Turn on the shop vacuum to collect the dust as you grind. You can even tape the vacuum hose to the panel being ground to better collect the dust. Finally, clean the area using acetone before and after grinding to remove oil, grease, wax and grinding dust before applying new resin.
Before the pieces can be repaired the break must be supported and aligned. Whether working with a small, medium or large repair I prefer using wooden paint stir sticks to bridge, support and aligned broken panels. The sticks are cut to length and clamped into place using C-clamp Vise Grip pliers.
This is the most critical aspect of repairing fiberglass damage. If the broken pieces are not placed and secured precisely prior to bonding the repair area will stand out as a wavy ripple on the surface of the panel and no amount of blocking and sanding will correct the problem.
Reinforcement plies.
All of those broken strands of fiberglass found when inspecting the initial damage make up the reinforcing structure of the panel. Without those strands the panel would be weak and brittle. To make our repair strong these strands must be replaced. Automotive body supply centers will have packages of fiberglass mat and rolls of fiberglass mesh for making repairs. Mesh repair rolls come 2-inches wide and fiberglass mat is available in various sizes of square sheets and rolls. Mesh rolls are great for making smaller repairs whereas sheets of mat are better for making larger repairs.
As mentioned earlier the choices of resins are either polyester or epoxy based and the stated use must be for either fiberglass or SMC panels. Do not mix and match repair resins, they may not be compatible with the panel being repaired and delamination of the repair could eventually occur.
If the panel being repaired is made of fiberglass you have the additional choice of using a finish resin and a lay up resin. Lay up resins are used primarily for molding and repairing large panels, such as when building an entire body for the old ’36 Dodge hot rod, or when trying to reconstruct the headlamp mounting panel on a ’67 Corvette. Lay up resins remain sticky to the touch after curing in order to allow additional layers of laminate to be applied to complete the repair without having to sand the surface to promote bonding.
Finish resins dry to the touch and if additional laminate is required to make the repair the surface must be sanded to promote bonding of the subsequent layers. This is the most commonly used resin out there for making repairs.
Note: A finish resin must be used as the final layer when lay up resins are used to construct or repair fiberglass panels.
Laminating the repair area.
Begin by cutting a strip of fiberglass mat or cloth just wide enough to fill the width of the repair and long enough to extend just beyond the ends of the damage. The next strip is cut a little wider and longer and the next even wider and longer until you have enough strips to complete the repair, usually five strips are sufficient.
Lay these strips out on a sheet of plastic like you were frying bacon. Next mix a small amount of resin and catalyze it according to the directions printed on the resin can then wet soak the strips with resin. I prefer using a disposable brush for this task. Next coat the entire bonding area with resin.
Starting with the narrowest strip of mat begin laying the replacement mat over the repair area. Using the brush, pat down each strip as you apply it to remove excess resin and prevent air from being trapped between the layers. Patting also helps to compact the layers into a solid mass of resin and fiber for a stronger bond. The final layer of mat should cover the entire repair and the overall thickness of the repair should not appear as a bump in the panel. If so, you have applied too many layers of mat and one or more of the internal layers should be removed. Allow the repair to cure, usually two to three days, before making cosmetic repairs to the outside of the panel.
Tip. Fiberglass resin tends to shrink as it dries and cures, the reason for the two to three day cure time. This shrinking and curing process can be sped up by using a heat gun to warm the repair area.
Cosmetic repair.
Begin by grinding the repair area smooth using a 24-grit grinding disk and finish sanding using a DA sander with 180-grit sandpaper to remove all traces of any scratches or broken paint edges.
To complete the repair I prefer using Evercoat Fiber Tech. This is a heavy bodied material similar to plastic body filler that can be used on either fiberglass or SMC panels to bond with, fill and smooth the outside of the repair. Fiber Tech does not shrink and can be applied with a plastic squeegee the same way plastic body filler is applied. Sand Fiber Tech using 40-grit sand paper and finish sanding with 80 then 180-grit sandpaper before priming.
Repairing spider web cracks.
The best example of this type of crack is found around the headlamp openings on later model Corvettes, and around the tail lamps on early model Corvettes. Recall I said fiberglass never stops shrinking? That’s what causes this type of damage. Over time the resin shrinks and small hairline cracks develop in the surface.
To repair this type of damage the individual cracks must be ground open in the form of a “V” to eliminate any stress in the area plus remove any contamination that may have found its way into the crack. Once the cracks have been opened and cleaned the surface area around the cracks must be ground down slightly to accept a single layer of fiberglass mesh, much like putting a band aid over a cut. But before the band aid can be applied the cracks must once again be cleaned of debris and once cleaned can be filled with Evercoat Fiber Tech Adhesive. After the cracks are filled the layer of fiberglass mesh is laid over the repair area and pressed into the Fiber Tech to form a secure bond. Additional Fiber Tech is used to cover the mesh and complete the repair. Allow the repair area to cure over night before sanding and priming.
Bonding adjoining panels.
This may seem like a massive undertaking, whacking off a chunk of the car and replacing it with a new panel, but it is actually a very simple process. GM made it even easier by using a contrasting color bonding material along the seam line that makes finding the seams a snap. Since I don’t have a complete Corvette in the shop, the last one left a few months ago and I’m still itching from the repair, we’ll continue to use our discarded fender to go through the process.
To begin with, replacement fiberglass and SMC parts are always molded oversize. The makers of these parts aren’t concerned about panel shrinkage as the part lies on the shelf, their concern is fit. Like cutting a board too short, you can’t water the part and get it to grow a half inch if it is too small. So with that concern for your state of mind, fiberglass parts makers always give you plenty of panel to work with. All you have to do is trim the panel to fit once it is in place and never before.
Let’s look at our fiberglass fender. Where is the seam line? It is located about four inches down from the peak of the fender and the best way to find it is to sand away the paint and expose the seam. The seam will appear as a dark line along the length of the fender. Once the seam is exposed the damaged panel can be ground away along the seam line to remove it. You will know the panel has been completely ground away when the area beneath the panel begins to darken. You have reached the bonding strip holding the two panels together. Stop grinding.
At this point the bonding strip can be cleaned up using a grinder in preparation for installing the new panel. The new panel must be prepped for installation by lightly grinding the back of the panel where it meets the bonding strip. Just like preparing a metal panel for installation, fit is everything so the new panel should be mounted into place for a test fit before any adhesive can be applied.
Once a good fit has been made the replacement panel can be removed, lightly sanded using 80-grit sandpaper on both sides to promote adhesion and Evercoat Fiber Tech Adhesive applied along the bonding strip. The replacement piece can then be clamped and screwed into place, allowed to cure then finish worked on the outside using Fiber Tech prior to being primed.
Of course in the real world problems do arise. Here are a few of the most common along with a few remedies.
Polyester Resin problems.
Hardener was added in the correct proportion (per instructions on the can) but the resin remains tacky even after the proper cure time has elapsed: Check to be sure the resin used was a finish resin and not a lay up resin. If the resin used was a lay up resin cover the repair with a layer of finish resin to promote curing and hardening.
If a finish resin fails to cure put a heat lamp on the repair area at 120F, two feet away for two hours to promote curing.
Epoxy Resin problems.
Hardener was added in the correct proportion and the repair is hard in most areas but has soft spots throughout: Epoxy systems are designed to react in specific proportions to one another. Extra care must be taken to insure you have the correct ratio of components and that those components be thoroughly mixed together in order to promote proper curing. The areas in question must be cleaned, sanded, recleaned and additional resin applied.
Urethane adhesives work great for a number of applications. How you you remove something that has been urethane glued into place? Try a little heat. Heat will soften urethane and let you remove whatever has been glued into place.
Never apply masking tape directly to rubber weatherstripping. The strong adhesive on the tape can tear the weatherstripping and ruin it.
Often overlooked is the need to apply white lub to all of your new hinges, door latches, trunk latches and hood latches during assembly of the car. Sometimes they items just don't seem to work properly out of the box. Usually that is because they need some lub.
When installing hidden door hinges try tab welding the door to the car to keep it in alignment while you position and tack weld in the new hinges.
To mount the battery under the cab of a resto truck try a street rod battery box. Some have built in adjustable lifts to help position the battery, others allow you to slide the battery out from the side for removal. Mount the box just behind the frame mounted master cylinder or under the seat area. Exactly where you mount the box depends upon frame clearance. Be sure you test fit the box before welding it into place.
