07.31.08

Sticky Stuff

Posted in Fiberglass Work at 8:00 am by Administrator

Epoxy PumpI’m nearing the end of the clean-up phase of the fiberglass pieces and I’m approaching the point at which I’m going to need to start the fiberglass repair work. As such, I thought I’d post some information on the techniques that I’m going to use to do the fiberglass repairs.

As I’ve mentioned before, the method that I’m going to describe is known as “Moldless Composite Construction” — a technique developed by the German sailplane industry but popularized in the U.S. by Burt Rutan. The word “Composite” refers to any structure in which the end result is better than the sum of its parts. By this definition, a peanutbutter and jelly sandwich is a composite structure.

Expanding the idea a bit, composite structures are usually composed of a fabric, an adhesive and perhaps one or more types of core materials. The fabrics are usually fiberglass, carbon fiber or an aramid fiber such as Kevlar. Combinations of these fibers can also be used. The Bradley uses chopped strands of fiberglass for their “fabric.”

The adhesive is usually a polyester resin system, a vinylester resin system or an epoxy system. The Bradley kit car used a polyester resin system. Resin and epoxy systems must not be mixed before they cure. However, once cured, you can use any of the systems to adhere new parts or repair old ones. I’ll be using an epoxy system to repair the damage to my car over the Bradley’s polyester system.

The core materials can be any number of types of foams (urethane, PVC, polystyrene, or proprietary foams such as Clark Foam or Last-A-Foam), or they can be cork, balsa wood, plywood, or corregated cardboards or metals. Most of the Bradley was constructed without core materials. However, plywood is used as a core material in certain portions of the body such as the forward and aft longitudinal ribs.

The main thing to remember about a composite is that we build our structures so as to take advantage of the materials’ beneficial properties while down-playing their detrimental ones. For example, adhesives have both good properties and bad ones. On the positive side, they’re strong and hard when cured, and they flow easily so that we can wet out our fabrics efficiently. On the negative side, they can be brittle and heavy. Foams are lightweight, which is good, but they are weak, which isn’t. Fiberglass is strong in tension, but less so in torsion and shear and it is weak in compression. So, we need to design our structures so that the fiberglass is in tension as much as possible. We need to use the foams as lightweight spacers between the layers (plies) of fiberglass so that the fiberglass takes the loads and the foams do not. We need to use the adhesives to bond the fabrics to the foams so that there is minimal tendency for the fabrics to delaminate from the foam structures and weaken them. That’s a lot to ask from these materials but, by being clever in how how use them, we can maximize the properties of our composite structures in the areas where we need them to perform.

Today, we’ll start our discussion by looking at the adhesives. Adhesives come in three families — vinylester systems, polyester systems and true epoxies. That order is important — its an order of increasng cost and an order of decreasing weight. For an electric car, low weight is good. There is a natural tendency to think of any adhesive that is composed of two parts (which you mix together to activate) as an epoxy, but this is not true. Vinylester and polyester resin systems are catylized whereas true epoxies are mixed. What’s the difference?

Have you ever worked with Bondo? Bondo is a non-structural cosmetic filler that is a part of the polyester resin family. It is non-structural — meaning that it is not intended to take loads — it is intended to fill dips and depressions to produce a pleasing cosmetic appearance. Because it is part of the polyester resin family, it needs to be catylized to be activated. When you mix Bondo, you add a very small amount of a red cream “hardener” to activate the material. The use of the word “hardener” here is unfortunate because, from a chemist’s standpoint, it is not a hardener — it is a catylist called MEKP (methyl ethyl ketone peroxide). In the strict sense of the term, hardeners are components of true epoxy systems — not of catylized resin systems.

In resin systems, all of the chemicals needed to harden the mixture already exist in the mixture. In Bondo, the grey stuff that comes in the can has all of the chemicals that are needed to produce a hard sbstance — but, they need a kick to get the reaction started. That’s what the catylist does. A catylist is a material that promotes a chemical reaction but does not enter into the reaction itself. Technically, a catylist lowers the energy barrier that keeps the chemicals from reacting. When you mix in the catylist, the energy barrier that keeps the chemicals from reacting is lowered by the catylist and the chemicals react, forming a hard substance. The amount of catylist required to kick off the reaction is not critical — you need to use enough to do the job but if you add too much, it’s just wasted. That’s why the mix ratio for Bondo (around 1/2% to 3%) isn’t that critical.

Now, contrast that to a true epoxy system. True epoxies contain a resin and a hardener. Here, the use of the word “hardener” is appropriate. Both components are required to create the chemical reaction, so there is no need for a catylist to promote the reaction. The mix ratios for true epoxies are fairly critical. If you have too much resin or too much hardener, they go unreacted and weaken the physical properties of the hardened material.

The epoxy that I like to use is called MGS 335 and you can learn more about it here…

http://www.aircraftspruce.com/catalog/cmpages/mgsresin.php

I use the L335 resin with the H340S slow hardener and mix the material with a 100:45 resin:hardener ratio by volume. This gives me a pot life of over 2 hours before the epoxy starts to gel. The long pot life means that I can only do one lay-up per day on any one given piece. I have to let the material cure overnight in warm weather and for two days if the weather is cold, but that’s a condition that I’m willing to endure. The long pot life means that I can take my time doing each lay-up and do a good job. I don’t feel rushed as I would if my epoxy had a 30-minute pot life.

Now, how do you mix the stuff to get the exact ratio that you need? I use a Sticky Stuff Dispenser by Michael Engineering:

http://www.michaelengineering.com/sticky_stuff/SSD.html

You need to purchase the pump for the particular epoxy system that you plan on using, so that it will mix the materials in the proper ratio. If you change materials, you may need to have the pump modified to accomodate a different mixing ratio, but Michael Engineering will sell you the proper parts so that you can do this yourself. With the pump, you simply put the hardener in the smaller container, the resin in the larger one and then pump the handle. The materials are delivered into your mixing cup via the two aluminum spouts on the pump.

Use unwaxed paper cups to mix the epoxy — the wax from waxed cups will contaminate and weaken the epoxy. Popsicle sticks or tongue depressors work great as mixing sticks. Mix the material for 2 minutes, scraping the sides of the cup every 15 seconds — that’s the standard Rutan protocol. After your lay-up, wipe any excess epoxy off the mixing stick with a paper towel and let any excess epoxy harden in the cup. You can re-use the cup for the next lay-up after the epoxy hardens. Used cups and sticks actually work better than new ones because they tend to soak up less of the hardener (which has a lower viscosity than the resin.

In the photo, you’ll notice that I keep my pump — and a spare gallon of epoxy — and some 5-minute epoxy — and some 30-minute epoxy — we’ll talk about those another time — in a wooden box. We call these things epoxy incubators. There’s a 60-watt lightbulb in the box which is connected to a dimmer. There’s also a thermometer in the box. By futzing with the dimmer, I can heat the box to keep the epoxy warm. I keep mine at about 95F year round, which means that I need to crank up the dimmer in the winter. By keeping the epoxy warm, you lower the viscosity of the two components. This makes it easier to pump and mix the material and it seems to wet out the fiberglass a bit better.

One problem that many of us have had with the Sticky Stuff Dispenser is that some chemical in the hardener embrittles the plastic Tupperware container that holds it. You go down to the shop one morning to work on a lay-up and discover that your pump is leaking hardener into the bottom of your incubator. This results in a lot of colorful language, an abnormally large consumption of paper towels and wasted hardener. As a result, some of us have started to replace the hardener container on these pumps with 1-quart uncoated paint cans from the local big-box hardware store. The down side is that you can’t tell when your hardener container is nearing “empty.” I draw marks on the resin container to give me hints as to when I might need to replenish the hardener.

Another problem with the Sticky-Stuff Dispenser is that the Tupperware containers are apparently porous to carbon dioxide gas. CO2 filters in thru the container and reacts with the hardener, forming a crystalline sludge at the bottom of the container. This only happens if you let the hardener sit unused in the pump for months on end. If you’re a fairly regular user of the epoxy, you don’t need to worry about this. However, if it happens to you, you must throw out the hardener and clean your pump because the hardener is defective at that point. Using a meal paint can to replace the Tupperware container helps with this problem a lot. Some builders, including yours truly, keep an argon blanket over the hardener and this eliminates the problem.

If you don’t feel like ponying up $300 bucks for an epoxy pump, you can mix the epoxy by weight using a postal gram scale. Figure out how much epoxy you want (say, for example, 3 ounces) and then weight out 100 parts of the resin in your mixing cup. Re-zero the postage scale and then add in 38 parts of hardener and mix the material. Note that you have to use different mixing ratios if you’re mixing by weight instead of by volume. Builders who use this technique claim that it’s just as easy to use as a pump once they get into the rhythm of things. Most builders make up a chart that shows how many grams of resin and hardener are required to mix up a batch of a certain size.

By the way, it seems appropriate to mention that, when working with epoxy, get used to the idea of mixing many small batches instead of a few large ones. This extends your working time. Large batches can generate their own internal heat from the curing reaction. The heat accelerates the curing rate and, in extreme cases, can result in something called an exotherm where the epoxy flash-cures. In some cases, exotherms have been known to cause a fire.

The MGS epoxy requires a shop temperature of at least 70F. Anything lower than that and it won’t cure properly. It may look cured, but it won’t have developed the advertised strength. There are ways that you can overcome this by post-curing, but that’s an advanced technique for another day’s discussion. For now, just keep your shop over 70F.

This brings us to the last topic of the day: Safety. The hardeners in true epoxy systems contain a chemical which is an allergic sensitizer. Some people can work up to their elbows in this stuff and never have an allergic reaction. Others only need to walk into a room where the epoxy is curing and they start itching and caughing up green guck. I’m of the latter persuasion. Problem is — you don’t know what your own reaction will be until it happens. Like hay fever, some people never react, some react after a few years and some people get sensitized fairly quickly. Once you become sensitized, you’re sensitized for life. Lucky you. Reactions also vary from one individual to another. Some people itch a bit, some get holes in their fingernails and some wind up in the hospital for a week or more with bad reactions in their lungs. So, if you’re going to work with this material, you MUST protect yourself properly. Here’s my drill…

1.) A Tyvek suit with hood — always. No exceptions.
2.) An MSA-approved, carbon canister organic vapor respirator. No lee-way here either. Just use it.
3.) Butyl rubber gloves. They’re the only ones that have been proven to work. Not latex, not nitrile, not anything else. Butyl! Latex gloves are porous — they aren’t to bacteria and viruses (which are large) but they are to molicules (which are a LOT smaller).
4.) Latex rubber gloves over the butyl rubber gloves. This keeps the butyl gloves clean. The butyl gloves are expensive — about $20 bucks a pair, so we use inexpensive latex gloves over them and just throw out the latex gloves when they get messy.
5.) Some form of eye protection. I use labratory splash goggles.

If you have access to a system that feeds fresh outside air into a respirator, you can use that instead of the organic vapor mask. Just make sure that your fresh air supply doesn’t draw in vapors from the epoxy.

The MGS epoxy is a great material, but is has almost no odor, so you can’t use your nose to determine if you need the organic vapor mask. You also can’t use it to determine when the carbon canisters in the mask are shot, so change the canisters frequently. Once you’ve done your lay-ups for the day, keep the shop well ventilated and don’t re-enter the shop withour some form of lung protection until the epoxy has cured.

I have found that in winter, when the epoxy cures slowly, I need to let the material cure for 48 hours before I can sand it. It’s just too gummy otherwise. Also, you need to use your organic vapor mask when enterng the shop if it contains partially cured epoxy. Make sure to use a dust mask when sanding cured epoxy.

If you’d like to work with this material, I recommend that you purchase it from The Composite Store (CST):

http://www.cstsales.com/

For some reason that we haven’t been able to figure out, both Aircraft Spruce & Specialty and Wicks Aircraft Supply (who also sell MGS epoxy) have outrageous shipping charges for this material. They claim that they can’t ship it by UPS and that it must be shipped by truck. The Composite Store has worked out a system with UPS to ship it and buying it from them will save you mucho dinero. You do have to pay the hazmat charges (as you would with other vendors), but the shipping charges from CST are far more reasonable.

Enough for now. Next time out, we’ll look at the fabric side of the equation.

07.27.08

Hot Air

Posted in Refurbishment at 10:24 am by Administrator

Defroster Heating CoilsDefroster Blower Motor & RelaysDefroster Plenum CoverDefroster Assembly & Plenum CoverThe Bradley GT II Electric was equipped with a defroster but not a heater. The defroster unit was positioned under the dashboard in a fiberglass plenum that was integral with the firewall and molded into the body of the car. Fresh air was drawn by a fan thru a hole in the forward face of the plenum (the car’s firewall), was warmed by a set of three resistance coils and was ducted to a pair of outlets on the top of the car’s glare shield. One relay controlled power to the blower motor and a second relay controlled power to the heating coils. Switches on the instrument panel controlled the relays.

When I received my car, several modifications had been made to the system. The air inlet hole in the firewall had been blocked off with, of all things, a round amber lens from a school bus’ turn signal. Hey — it was the right size! A smaller inlet hole was drilled into the plenum on the passenger-side of the firewall, reducing the fresh air feed from outside the car. Two trapezoidal holes were cut into the plenum cover. You can see these in the photos above. Adding these holes had the effect of recirculating cabin air thru the defroster. Presumably, the cabin air would have been warmer, making the defroster more effective. There were no valves or dampers in the system, so the relative amounts of recirculated and fresh air were determined simply by the sizes of the holes thru which the air flowed.

The outlet side of the system was also altered. One of the outlets in the plenum chamber cover was ducted to both defroster outlets with hoses and a tee fitting. The other outlet in the plenum chamber cover had a small louvre. This had the effect of directing some of the air from the defroster down towards the driver’s feet. Again, there were no dampers in the system but by closing the defroster vents, all of the air would have been directed towards the floor of the car under the instrument panel. The modifications were really quite clever and probably aided in improving the comfort of the occuppants.

The photos show how the whole thing was assembled. I’m toying with the idea of adding a few further modifications. I’d like to put dampers on the trapezoidal holes. I’d also like to re-open the original hole thru the firewall and add a damper there. Finally, the smaller hole thru the firewall — the one added by a previous builder — would be sealed off. This would have the effect of controlling the relative mix of inside and outside air — similar to what you find in most production cars. I don’t know if I can do this, but I’m going to start thinking about it.

07.17.08

Hard Points

Posted in Fiberglass Work at 4:43 pm by Administrator

Seat Bucket Attach Hard PointsFront Slider BracketsRear Slider BracketsBracketry for Mounting Seat Buckets to SlidersWhile I’m growing new fingertips, I decided to put a bit of work into figuring out how to mount the seat buckets to the seat sliders today. In the original Bradley design, left and right sliders were bolted directly to the seat bucket. In the car I purchased, a previous owner had modified the design by attaching the sliders to the buckets with a set of custom brackets (see the photo of the seat slider in yesterday’s post).

When I removed the foam and fabric from my seats and discovered how the sliders had been mounted, I knew that I wanted to do something different. The idea of having bolts protruding thru the seat buckets in the vicinity of my posterior didn’t exactly thrill me. Granted, there is roughly 2 inches of foam padding that overlies the bolts, but it just seemed like there ought to be a better way.

In the fourth photo, you can see a pair of metal strips. Each strip has two bolts tack welded to it. The nearer one shows the bolt threads and is just thrown in the bucket; it is positioned in a set of holes that are in the lower right corner of the photo. The far one is properly positioned so that it can be attached to the rear two brackets on the sliders. A bolt was run thru the center hole in each strip and fastened to the seat bucket with a nut. In this way, the strip was held in position and wouldn’t go flopping around (under the upholstery) if the two outside nuts were loosened. Also note the wallowed-out holes for the bolts that secure the rear brackets to the seat sliders. How would you like to sit on one of those? Ouch!

In the third photo, you can see how the bolts welded to the strip protrude thru the seat bucket and attach to the rear-most slider brackets. The second photo shows how the bolts in the second strap are supposed to attach to the front two slider brackets.

I decided to try a different approach — one that would result in no hardware contained inside the seat buckets and under the upholstery. I made a set of 8 hard points out of 1/2-inch mild steel plate. The hard points are 1-1/2-inches square and are drilled and tapped for a 5/16-18 bolt. The parts were cut from steel plate on a band saw, trued up on a small mill-drill, drilled on the mill-drill and then tapped by hand. Four of these will be attached to the bottom of each seat bucket.

If you’re familiar with Moldless Composite Construction, the hard points are just floxed in position and glassed over. If that’s Greek to you, they’re held in position with a material called flox, which is a mixture of pure epoxy and flocked cotton fibers. Flox is a structural adhesive — meaning that it can accomodate loads. When it cures, it has the hardness of concrete. Many of Burt Rutan’s airplanes are held together with flox joints and some of them have been flying for over 30 years now. Once the hard points are floxed into position, I’ll lay 12 plies of bidirectional fiberglass over them and then peel-ply the glass for a smooth transition onto the surrounding seat pans. I’ll have more to say about flox when I do the lay-ups and, by then, we will already be familiar with the different types of fiberglass and epoxies from having done some simple lay-ups. I’ll post pictures when the job is actually undertaken. Until then, this should tweak your curiosity on some of the techniques that we’ll be learning here.

It took about 6 hours to make the hard points but the end result should be worth it — rock-hard mounting points for the seat buckets where all of the hardware can be accessed from the outside of the bucket.

07.16.08

Safe Cracker Available for Hire

Posted in Fiberglass Work at 1:22 pm by Administrator

Before and After — Cleaning the Upholstery Cement off the Seat BucketsHoley Seat-Buckets!New Seat Sliders with Old BracketryFor the last few days, I’ve been sanding all of the old upholstery cemet off the seat buckets, seatback shells, glare shields, door panels, etc. and, at this point, I’ve sanded the fingerprints off my fingers. It may be a few days before I resume that task. The left photo shows a before-and-after comparison on the seat buckets.

The center picture shows how many holes were drilled in the buckets over their 28-year lifespan and that prompts a tale…

The original plans for the GT II show seat sliders that are mounted to the sides of the buckets. I didn’t receive these when I bought the car, but the holes for the stock sliders had been drilled into the buckets. My guess is that the original seat sliders were replaced by a prior owner — and for an understandable reason. The original sliders — there was a left one and a right one on each bucket — were not connected to each other in any way. They were just bolted to the fiberglass buckets. It’s easy for me to see how this could cause a big problem in adjusting the seat positions. There would be a tendency for the seat to twist left-to-right with the two sliders operating independently of each other. One might lock in while the other didn’t. Thankfully, the car I received had a different design.

The picture with the seat slider shows a new slider (bought from Chirco in Tucson) with the old mounting hardware. The black cross-straps ensure that the two sliders move in unison, eliminating the tendency for the seat bucket to twist. This is the setup that came with my car — vastly superior to the original Bradley design.

The sliders that I received were rusted shut — having been in contact with wet carpeting in the car — so I had to buy two new pairs. I was hoping that the original bracketry (shown in the photo) would work with the new sliders but, alas, it was not to be. The rear brackets come pretty close to being OK — if I’m willing to allow those big wallowd-out holes that someone cut into the buckets to allow for bolt clearances — which I’m not (see the center photo). The front brackets are way off with the new sliders. Also, the seat sits a tad too low — resting directly on the spring wire that connects the two locking cams on the sliders.

I’m going to need to devise some new bracketry to hold the seat buckets but, before I do that — or, maybe in conjunction with that — I’m going to need to patch all of the holes in the buckets and reinforce the areas where the buckets will attach to the sliders. This isn’t a big deal — just one more task to undertake.

Then again, a little metalwork might be just the thing to do while I’m growing a new set of fingerprints.

07.15.08

Delamination

Posted in Fiberglass Work at 6:46 am by Administrator

Delamination on Left Front Rib — Outboard SideDelamination On Left Front Rib — Inboard SideDelamination on Front Right RibDamaged Area On Left Rear FenderThe body came back from Plastic Media Stripping yesterday — pretty amazing service. It took them about 3 hours to bead blast the underside of the vehicle and get it down to raw fiberglass so that I can start the repairs on the main body. I also asked them to remove the gel coat in the area where the left rear fender had been damaged and this came out nicely (see the picture).

By removing all of the paint on the underside of the vehicle, I was able to locate certain defects in the body that weren’t visible before. One of the main concerns has to do with the two longitudinal stiffening ribs located in the front of the car — at either side of the hood. Both of these ribs have delaminated from the body for about the forward-most 8 inches and it’s easy to see why.

The electric version of the GT II has a special set of instructions that have you modify the body of the car in a different way than you would have done had you been building the gasoline-powered version. One of those change-orders has to do with how the hood is cut out and the change has you cut it very close to the stiffening ribs. A portion of the weight of the forward battery box is tranferred into these ribs by a pair of brackets — one each side — that connect the forward battery box to the ribs. These brackets also hold the mounts for the front bumper. With the dynamic loading of the batteries constantly bouncing and pulling on these ribs, it’s a wonder that they didn’t delaminate further. There is very little overlap between the glass on the ribs and the glass on the body — especially on the inboard sides of the ribs, where less than an inch of overlap exists.

Somehow, I’m going to have to grind away the delaminated fiberglass and reinforce the joints. Reinforcing the outboard sides will be easy — there’s lots of surface area there to make a good, strong structural lay-up. Reinforcing the inboard sides is something else again. I may need to wrap fiberglass onto the top (outside) of the body to make these joints strong. That will require a lot of cosmetic work on the outside of the body — on either side of the hood hole — to fix the joints.

The good news is that it’s better to find out now than when the car is on the road.

By the way — take a look at the first photo in yesterday’s entry. It shows the front end of the car with the two longitudinal stiffening ribs. My blog editor has a 4-photo-per-day limit, so I had to place this last photo in yesterday’s entry.

07.13.08

Glasswork

Posted in Fiberglass Work at 3:49 pm by Administrator

Front End of Car Showing Longitudinal Reinforcing RibsOriginal Seat UpholsterySeatback Shells — One Clean, One NotGlare Shield After more weeks than I care to remember, all of the hardware for both the VW donor chassis and the Bradley kit car have been refurbished and inspected. I’ll need to purchase some basic hardware items to replace some of the bolts, nuts, screws and washers that rusted to the point of being unuseable but about 80% of what came with the car was salvageable.

The next job is to restore all of the fiberglass parts. As many readers may not be familiar with the procedures and materials used to do basic fiberglass work, I’m going to add quite a bit of detail to the description. To begin, there are 25 pieces of fiberglass (or ABS plastic) that must be reconditioned:

(1) Main Car Body
(1) T-Top for Main Car Body
(1) T-Top Liner (For Headliner)
(4) Upholstery Shells (For Areas Surrounding Small Rear Windows)
(1) Center Console (ABS)
(1) Glove Box
(1) Defroster Shroud (ABS)
(2) Door Panels (ABS)
(1) Hood
(2) Headlight Buckets
(1) Trunk
(2) Gull-Wing Doors
(2) Bumpers
(2) Seat Buckets
(2) Seat Bucket Back Panels
(1) Glare Shield (Goes On top of Dashboard)

Some of these parts just need to be cleaned up. This usually consists of having the old upholstery stripped and the upholstery cement removed. The Glare Shield and Seat Bucket Back Panels would fall into this category. Other parts may need structural repair or reinforcement (my rear bumper took a bad hit on the left side) and most, if not all, will need cosmetic work (filling, sanding, contouring, priming and painting. There’s an order to doing this work and cleaning up the parts comes first. All of the old upholstery and rubber cement needs to be removed from all of the fiberglass parts — down to the bare fiberglass in some cases or down to the gel-coat in others. Once the parts are cleaned up, structural repairs are next. This may require removal of gel-coat or paint in damaged areas because you cannot perform an adequate structural repair over gel-coat or paint — you have to get down to the raw fiberglass. Once the structural work is done, then the cosmetic repairs can be done.

The method of fiberglass work that I use is called Moldless Composite Construction and, as the name implies, no molds need to be made to repair any of the parts or, for that matter, even to fabricate new parts. We’ll demonstrate this latter concept by scratch-building an overhead center console for the T-Top without building any molds. Moldless Composite Construction was developed by the German sailplane industry but was popularized in the U.S. by Burt Rutan, designer of the Vari-EZ, Long-EZ, Defiant, Voyager, and numerous other experimental and factory-certificated aircraft. The technique was recently used in the construction of Space Ship One and its mother ship — White Knight. The techniques are easy to learn, the materials are readily available and the methods produce strong and lightweight structures. If you’re not familiar with the techniques and would like to get some hands-on experience as I describe them, Aircraft Spruce and Specialty sells a practice kit, a demonstration video and all of the materials that you will need. You can purchase similar items from Wicks Aircraft Supply or The Composite Store (in Tehachapie, CA). Other techniques and materials may be equally applicable here. However, I’m most familiar with the procedures developed and the materials recomended by Burt Rutan — so those are the techniques and materials that I am going to describe.

Back to Step 1: — Cleaning the Parts
You’ll need to strip all of the upholstery and backing foam from all of the fiberglass parts, including the main body of the kit car. Ripping and shredding works well for the bulk of the material but remove the fabric with sufficient care that you can trace patterns on a roll of art paper. Be sure to mark the outline of each fabric piece along with the locations of any folds and seams that have been stitched into the fabric. If the fabric parts aren’t in too bad a condition, you might want to save them for use as models when you are making up the new upholstery. My upholstery was so deteriorated and soaked with pigeon and cat urine that I just made paper patterns and got rid of the original material as fast as I could.

Once the foam and fabric have been removed, you’ll need to remove any excess upholstery cement. A lot of this cement may have partially deteriorated (oxidized or powdered) and trying to fasten new upholstery over the old glue is a waste of your time. Also, if any structural repairs are required for the part, you will need to remove everythng (foam, cement, fabric, bondo, paint, primers, gel-coat…) right down to the bare fiberglass — on both the inside and outside of the damaged areas.

Upholstery cement is basically just a special formulation of rubber cement. As such, Acetone is the best solvent to soften (not remove) the old glue. You can use mineral spirits, but acetone works better. Make sure that you use the proper safety precautions when working with acetone (butyl rubber gloves, respirator with organic vapor cartridge, no open flames nearby, etc… Read the precautions on the can.) I use a paper towel to saturate the old glue with acetone to soften it and then use a single-edged razor blade to scrape the glue off the fiberglass. Once all of the glue has been removed, I sand the entire part with 60-grit aluminum oxide paper. This helps identify any glue that I might have missed and roughens up the part so that the new glue will adhere well. Removing the old glue takes time — it took me about 5 hours to do each of the seatback shells, for example — but it’s a lot easier and more pleasant to repair and upholster a clean part than a messy one.

To date, I’ve got the two seatback shells finished and the glare shield about half-way done. I’ve also got most of the headliner shell cleaned off and I’ve cleaned up the glove box. (In the original Bradley instructions, the glove box is glued to the back face of the dashboard with a structural adhesive. The joint was not glassed over with fiberglass tapes, as it should have been. Bradley left the installation of the glove box as an option, for builders who might prefer to install a radio in this location. I found that my glove box fell off after a couple of whacks with a rubber mallet. The adhesive was very brittle and the glove box popped off easily without any damage. Once on my workbench, I was able to sand off the old structural adhesive in short order. I’m going to use a flocking kit that I obtained from Woodworker’s Supply to flock the inside of the glove box. I’ve done this before and it comes out looking very professional — even for first time users — and it sure beats the carpet that was originally used.)

After you have all of the glue removed from all of the parts, you’ll be ready to start the structural repairs. In the next blog entry, we’ll do a couple of easy ones to introduce you to the materials and procedures.