Body: An Introduction to Scratch Building
From The Scratch-Built Hot Rod
Chapter 6: Body - An Introduction to Scratch Building
A short history of scratch building
|Scratch building has a long and storied history. Our earliest historical references date back to about 1450, when Hungarian craftsmen began building horse-drawn carriages and coaches for the aristocracy and wealthy land owners (Photo 6-1). In those very early years, the craft was known as the "carriage trade". By the 1600's, carriage making had spread far and wide, becoming more affordable to the masses, and over time, the process became known as coachbuilding (Photo 6-2). Coachbuilding was an honored and profitable business. So profitable, in fact, that in 1637, King Charles I of England imposed the first known tax on the coachbuilding industry. Source|
|By the 1770's, coachbuilding had come to North America. The "Beekman Carriage" shown in Photo 6-3 was owned by wealthy merchant James Beekman, and the carriage was reportedly used to transport George Washington. Early coach construction consisted primarily of fabricating a wooden substructure or skeleton, and then attaching some sort of weather-resistant fabric or material, to "skin" over the skeleton and protect the passengers from the elements. Photo 6-4 is a blueprint of an early coach in which you can make out the wooden framework or skeleton for the body.|
|By 1900, horse-drawn coaches had become quite common; there were 400,000 of them in England alone. Business was booming for coachbuilders, and almost every town of any size had at least one resident coachbuilder. Source Examples of coaches from this era include:
The carriage of Kathrine Wright, sister of Orville and Wilbur Wright, in front of the Wright home. (Photo 6-6)
|A wide variety of coaches and carriages on New York's 5th Avenue and 42nd Street. (Photo 6-7)
A Landau-type coach parked in the stable area of the White House. (Photo 6-8)
With the invention of the automobile at the turn of the century, coachbuilders found a whole new outlet for their skills. Prior to the creation of assembly line production by Henry Ford, it was not unusual for automobiles to be purchased as two separate units. The buyer would obtain a rolling chassis, including engine, gearbox, differential, axles, wheels, suspension, steering system and the radiator, from a chassis manufacturer. Then, the chassis would be taken to a coachbuilder, and there a body would be built to the customer's specifications. Designs for these bodies ranged from less-expensive traditional models to more exotic models that were custom-designed for buyers. Source
|Many of these early automobile coachbuilders trace their roots directly to the carriage industry. John B. McFarlan, for example, became an Ohio blacksmith's apprentice in 1840 at the age of 18. He then went to work as a carriage blacksmith and eventually moved to Connersville, IN in 1856 where he organized the McFarlan Carriage company, which produced a variety of horse-drawn carriages and coaches (Photo 6-9). McFarlan died in 1909, but under his grandson Harry's direction, the company completed its transition to the production of automobiles and automobile coaches that same year. Source: Historic American Engineering Record, U.S. Dept. Of InteriorFurther Source The McFarlan company produced luxury automobiles under its own name, as well as building coach bodies for well-known names such as Duesenberg, Auburn and Auburn/Cord. The McFarlan Roadster can be seen here. The company also created a racing version of their car, and entered the Indianapolis 500 from 1910-1912, wrecking their car in that final year, as shown in Photo 6-10. The McFarlan company was hard hit by the depression and the factory was sold to Auburn in 1929.|
|Early automobile coaches were almost indistinguishable from their horse-drawn counterparts. Photo 6-11 is an early Mercedes Benz automobile carriage. For many years automobile bodies were built using the exact same technique used for the horse-drawn carriages: a wood or metal skeleton covered with a skin made of wood, fabric or metal to keep out the elements, and in some cases, to give the coach a unique appearance (Photo 6-12).
Even after the manufacturing revolution created Ford's assembly line and the widespread availability of the low-cost but somewhat boxy Model T, the more wealthy in both the U.S. and throughout Europe continued to utilize the traditional method of car ownership, buying the rolling chassis from one maker and then having a custom body built by a coachbuilder. In fact, the tradition remained so prevalent that the Model T and even Ford's Model A continued to be offered to the public with the option of just purchasing the rolling chassis.
However, it was in Europe where the coachbuilding tradition held out the longest. In spite of the economic advantages of an assembly line model with a mass-manufactured body already attached, European coachbuilders continued, even after WWII, to produce their bodies one at a time, using the age-old method of hammering out metal panels over stumps, sand bags and wooden bucks. In addition, they continued to use the skeleton and skin construction techniques, replacing wood as the predominant skeleton material with thin-wall metal tubing or small diameter steel rod. In almost all cases, the skin was now metal rather than wood or fabric. Source Even Model T and Model A bodies, which were stamped out and assembled in a uniform fashion, still retained a basic skeleton and skin configuration, having either a wooden or metal substructure that held the stamped steel parts rigidly in place.
|From 1920 to 1950, the U.S. automobile industry methodically moved from skeleton and skin bodies to the monocoque or unibody type of construction, and then to the modern-day welded unit body. However, a few authentic coachmakers continued their tradition, and a few remain even to this day, including Crailville Ltd. which meticulously crafts their skeleton frames from ash to make the Bugatti and Alpine Eagle Silver Ghost being constructed in Photos 6-13 and 6-14.|
Modern-day coachbuilding methods
There are seven basic methods that modern-day builders can use for constructing an automobile body.
- Fiberglass molding - 3 step process
- Fiberglass molding - 2 step process
- Fiberglass sandwiching
- Freestanding component panels
- "Heavy metal"
- "Frankenstein fabrication"
- Skeleton and skin
Fiberglass molding - 3 step process
Most fiberglass bodies are built using a three-step process.
- 1. The builder constructs what is commonly referred to as a "mock-up"," plug" or "male mold". This is an exact representation of the body or object to be made. Builders can also use an actual, pre-existing body or part as their "plug".
- 2. The builder creates a "female-mold" by casting fiberglass cloth and resin over the outer surface of the plug.
- 3. The builder removes the plug from the female mold and then creates the final body or component by casting fiberglass cloth and resin over the inner surface of the female mold. When the female mold is removed, the component will be a smooth and nearly-finished replica of the plug.
This is just a very quick synopsis of the process. In actual practice, each of these steps must be done with great care and preparation. Check these sites and videos for details on fiberglass body fabrication.
Photos 6-15 to 6-17 show a hot rod body built by Randy at Randy's Street Rods in Southern Louisiana, using the traditional three-step fabrication process. Randy works principally in his backyard shop, using tools that can be found in virtually any hot rodder's garage. He provides an easy-to-follow tutorial on fiberglass part making beginning here.
Fiberglass molding - 2 step process
|A variation on the fiberglass mold process described above is what I call the "Big Daddy" method. This method was used in the construction of some, but not all, of Ed "Big Daddy" Roth's iconic hot rod bodies made in the 1960's and 1970's (Photo 6-18).
Basically, this method skips step 2 of the process outlined above. No female mold is cast. Instead, the final shell of the car is cast in fiberglass directly over the plug. After the resin hardens, the plug is removed from the back side. The outer "finished" surface will still be quite rough and must be straightened and smoothed using body filler and block sanding.Roth came up with the unique concept of using plaster of Paris to make his plugs. After the fiberglass shell hardened, the plaster was beaten with hammers and mallets to remove it from the inside of the shell. Builders, such as Robert Q. Riley Enterprises, who employ this technique today often use lightweight foam to create their plugs as described here. In some cases the foam is removed and in other cases the foam is left in place and "sandwiched" between inside and outside layers of fiberglass. The body shown in photo 6-19 was made using the two-step process leaving the foam plug in place.
|Yet another technique employing fiberglass is the sandwich or "core" method. The builder first constructs the body using lightweight materials such as wood, wood veneer, cardboard, aluminum, sheet metal, plastics or foam to create the general shape of the car. Then, fiberglass is cast over the inside and the outside of that structure, forming a "sandwich" with the lightweight panels acting as an armature or core. This core remains as a part of the body, although it is typically not considered a structural element. Once cured, the outer surface of the fiberglass will be quite rough, and must then be coated with body filler and sanded smooth.
The rather homely body shown in photo 6-20 was created by the author using the sandwich method in the early 1990's. This was my very first foray into scratch building and clearly left a lot to be desired from a design perspective. Nevertheless, it served quite well as a learning tool. The car was sold before completion, and I have my doubts it ever saw actual road travel.Photo 6-20a shows another body designed by Robert Q. Riley Enterprises, created with a thin foam core encapsulated inside and out with a fiberglass shell.
Freestanding component panels
This is one of the more difficult methods of body fabrication, and is often reserved for the highly-skilled metal craftsman. Typically, the builder begins with an existing body which he/she then replicates. This is done by drawing an imaginary grid over the outside or the inside of the body, and then forming a myriad of individual panels from thin aluminum or sheet metal to mimic the shape within each section of that grid. The individual panels are welded together and then smoothed to create large sections of the body.
|This grid is often not just imaginary. Many builders first build a wire form "buck" on which the individual metal panels can be shaped and formed. The wire form is created by a grid pattern of 1/4" steel rod, which is shaped to the inside surface of the existing body. The grid is tack welded together and then removed.
Master builder Randy Ferguson provides an excellent and detailed tutorial for this process on his website. The photos here simply preview that process. Photo 6-21 shows the Willys roof Ferguson will use as his original and Photo 6-22 shows the underside of the roof with the wire form buck being made.
"It is very important to study the panel well before starting to design the buck," notes Ferguson. "Most panels will not allow for the buck to be made in a single piece. They need to be of a modular design in order to get them removed from the original part as well as each new panel that is made using the buck."In addition Randy suggests that "wherever possible, it's a good plan to use steel along the edges of the buck, especially in areas where flanges will be turned directly on the buck. This will allow the buck to be used many times without needing to be repaired."
|Once the wire form is welded together the form is removed and the inside surface of the original panel is coated with a "release agent". Ferguson recommends S.C. Johnson Paste Wax. The wire form is placed back in the panel and body filler, such as Bondo, is applied around the 1/4" rods and allowed to cure. In areas where the buck may be used as a hammerform, Ferguson notes that fiberglass reinforced body filler is preferred, as it is far more durable than regular body fillers. When the wire form is removed, the Bondo will provide an exact match to the inside surface of the roof.
With the "buck" completed, Ferguson then begins to form metal sections of the roof using the traditional metalshaping techniques of hammer and bag, hammer and stump, English wheel and planishing hammer. The wire form buck is used to ensure the panel is in the exact correct shape (Photo 6-23).The various panels are then welded together (Photo 6-24) and ground or hammer welded smooth.
The nearly completed roof is shown in Photo 6-25.The same process is used by Ferguson for all the other sections of the car. The fender fabrication process is shown in Photos 6-26 through 6-28.
|Instead of welding, the freestanding panels created using this method can also be bolted together by adding flanges to the edge of adjoining panels. This is typically used for making removable fenders, hoods, trunks or other parts of the car. Depending on their size and shape, panels will sometimes be reinforced with beads, which are pressed into the panels with special rolling machines to give the panel strength and rigidity. This is often seen in the construction of floor panels.
For building custom bodies, Ferguson creates a freeform buck such as the one shown in Photo 6-29.
No, this method has nothing to do with loud and raucous music. I call this method "Heavy Metal" because, typically, it does not use a skeleton or framework on which to build. And instead of using thin, freestanding sheet metal sections which often require special machinery and techniques to give the body strength and rigidity, the panels or body sections of a "Heavy Metal" car are made of thicker-gauge steel, which is inherently stronger and more rigid than sheet metal. This also reduces the need for a complete skeleton.
|The drawback is that the heavier steel is more difficult to form into compound curves and corners. On the flip side, heavy skin bodies usually allow for much quicker construction times than a body made using freestanding sheet metal panels. We will be looking at this method in greater detail in the Gallery section which follows, but, for now, here are a couple of examples of Heavy Metal body fabrication.
The first is this pickup built by Randy at Randy's Street Rods. This car was completed within an incredible 100 hour timeframe (Photo 6-30).The second is a "woody" built by Randy's friend from Southern Louisiana, Iron Man Joe (Photo 6-31).
|Just as Dr. Frankenstein built his creation out of a wide assortment of human body parts, the Frankenstein fabricator uses a wide assortment of existing body parts to create something entirely new and different. Instead of shaping a flat section of sheet metal into curves and corners using an English wheel or hammer and beater bag, the Frankenstein builder heads to the boneyard to find that exact same curve on some existing junker.
Frankenstein builders become experts at spotting usable curves, corners, angles and flat section on all sorts of old vehicles, from buses to vans to motorcycles. These sections are then cut, trimmed and welded until they blend together into a smooth-flowing body of the builder's own design.Australia's Rob (Chuck) Berry built his incredible '34 Ford replica primarily from cutting the various curves and forms he needed from an abandoned bus (Photo 6-32).
Skeleton and skin
|This is a very traditional method of building coaches described above and dating back to the construction of horse-drawn carriages. The basic shape of the body is fabricated with a framework of wood, metal or other material. A weather-resistant skin is then shaped to fit over and attach to the framework. Photo 6-33 and 6-34 offer a preview of the amazing work done by Shin Yoshikawa as he builds very modern, sports car type bodies. You can see the lightweight skeleton as well as the aluminum skin work in these photos. Visit Shin's website to see the entire process he uses in much greater detail.|
Needless to say, none of these fabrication methods is mutually exclusive. Builders will often combine the various methods into one car, perhaps forming the body using skeleton-and-skin and then forming other components, like fenders, using freestanding panels, and yet other parts will be cast with fiberglass. Also, Heavy Metal cars will often utilize a bit of reinforcing framework here and there, as will fiberglass shell cars. These methods are identified here not to imply that you need to choose just one, but rather to provide you with the range of options you can incorporate into the fabrication of your own car.
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