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CHAPTER 1

EVOLUTION OF THE CONVERTIBLE TOP

Everyone knows that there is nothing more romantic than driving along a country road on a moonlit evening with the top down. What most people don’t remember is that the automobile started out as a modified horse carriage. These primitive buggies were commonly referred to as an open car because they had no doors, windows, windshield, or roof.

An open carriage meant that the driver and passengers were directly exposed to the elements. And, because most early roads were unpaved, road dirt, rain, and the often-unpleasant scent of nature would envelop the occupants. By wearing heavy slickers, protective goggles, and gloves, the auto enthusiast could endure this modern convenience of driving.

As the automobile evolved with internal combustion and electric engines, passengers also wanted more creature comforts, such as being shielded from the elements. This soon led to the addition of a glass windscreen and, later, a folding top and side curtains. These crude devices limited the amount of road dirt and rain that fell on the occupants, but there was still a desire for more comfort. That eventually led to the development of the fully enclosed cab.

Early American cars, like this 1906 REO, were not much more than a rolling chassis with little comfort other than the sofa taken from Grandma’s parlor. Passengers were exposed to the weather and the open road with very little protection.

Early Top Frames

Before the automobile, horse-drawn buggies and wagons were used to transport people and goods from place to place. Having a top on the vehicle kept the sun and rain off of passengers, and having it fold out of the way when it wasn’t needed aided in hauling larger parcels.

Early buggy top frames were very crude but functional. The frames were fashioned by a blacksmith out of smaller pieces of forged iron, and then they were assembled to create the articulating side rails. The side irons were connected parallel to each other by wooden bows, usually hand hewn from ash or oak. These wood species made the best choice for top bows due to their tight grain and strength.

Because the bows were made from wood, the attachment of the canvas cover material with tacks was almost effortless. All a blacksmith had to do was drive the tack into the wooden bow instead of making attachment holes in a metal frame so that the canvas cover could be tacked on.

The Ford Model T was introduced in 1908. This popular car offered the driver some shielding from inclement weather with a split windscreen and a folding top, but the Model T still left its passengers exposed due to the lack of side windows.

Taking a cue from the horse-drawn buggies, the convertible top frames were very similar on early model cars. Steel frame components would soon be mass-produced by stamping the pieces from sheets of metal and then bending and welding them together.

Enclosed Cabs

Between 1910 and the early 1920s, many of the cars produced were being enclosed with fitted doors and windows. This made the riding experience a lot more enjoyable by keeping the road dirt and weather out, but some occupants felt boxed in and eventually became claustrophobic because of the nature of the enclosed cab.

It wasn’t long before car owners and passengers wanted the option to open up the car by dropping the top to allow for a more-natural airflow through the car. This option of a folding top was soon adopted as a standard throughout the automotive world.

Fitted doors with side windows met the public’s demand for a vehicle with an enclosed cabin but resulted in a car that left the occupants with a feeling of being closed in. Drivers began to look for options that would give them a car that would convert to an open car.

Early convertible top frames used wooden bows to support the roofing fabric. The cross bows also tied the side irons together, keeping them parallel with each other. After World War II, car manufacturers began using stamped steel for top bows.

Folding Tops

Until the mid-1940s, American convertible top frames were constructed with wooden bows and iron rails with articulating hinge components. The simple frames were covered in canvas to allow the folding of the articulated top without damaging the cover material. These early convertibles were also very drafty and noisy, and because they did not seal well, they also leaked when it would rain.

As factory tooling improved, better-fitting windows and rubber door seals were added to make the riding experience much more comfortable, but it just wasn’t the solution motorists were looking for. It wasn’t until after World War II, when an abundance of superior materials became available, that the convertible top took on a better shape. With an ample supply of steel and aluminum, convertible top frames began to function and seal much better. The topping materials used to cover the frame also improved, and additional color choices were available.

Modern Innovations

The ultimate convertible top wouldn’t be realized until the mid-1950s, when Ford Motor Company introduced the first fully retractable hard top. Solving the problem of leaking and noise, the rigid top would not only fit better but it was able to disappear completely into the trunk of the car, transforming the sedan into a modern open-concept roadster. This engineering marvel was used by Ford on several models until the mid-1960s.

This Ford Skyliner was a modern marvel in the mid-1950s with its fully retractable hardtop roof. Was it a sedan or a roadster? Drivers have said that this design was the best of both worlds all in one package. A quiet, leak-free top or no top at all!

One of the most unique convertible top designs that the General Motors Corporation made was the scissor top. Appearing in 1971 and lasting until 1976, the top design was created to give the car more passenger space by eliminating the traditional hydraulic cylinders that occupied the rear seating area.

A new concept in convertible tops was realized in 1971. That year, General Motors came up with a sleek convertible top with an unusual operating system for its full-size car line. The top was referred to as a scissor top, mainly because of the way it would fold into itself.

The scissor top sported a low, swept-back profile with a glass rear curtain. The operating system that was used on these cars was also changed from the standard hydraulic pump and cylinders to a cable-driven system operated by electric motors.

The main reason for this dramatic redesign was to get more seating area in the rear of the car and appeal to the growing family of many car owners. Traditionally, the rear seat was narrower on a convertible to accommodate the convertible top frame and fitment of the hydraulic cylinders that moved the top up and down. Changing to a slimmer and more compactable top frame allowed for the fitment of a full-size rear seat. In 1976, the design was dropped with the last of the tops being used by Cadillac.

Convertible Top Components

There are many elements that make up a convertible top. Each part has an important function, and they all work in unison to keep the weather out as well as allow the top to articulate and stow away.

This complex assembly needs to be properly serviced to keep it in peak operating condition. If any part of the system fails to do its job, it can damage the top. Making repairs on a convertible top can seem overwhelming, but if you understand how each component functions, you will have no trouble putting a top back into perfect working order.

The Frame

A convertible top frame is made up of a complex mix of pieces. Rails, bows, hoses, and fabric are all components that make up the articulating convertible top. These parts all interconnect and serve a specific task. The convertible top frame also defines the shape of the top, giving the car its distinct look and character.

A standard convertible top frame supports the vinyl or canvas topping material and defines the roofline of the car. Each frame is comprised of many simple components that work in unison, allowing the frame to fold and resume its shape without damaging the top material.

Bows

The horizontal pieces that connect to the side rails are called bows. These bows support the bulk of the top material and keep it from falling into the car. Early model convertible top cross bows were typically made of wood. With advancements in modern manufacturing methods, postwar cars had bows made of stamped and formed steel.

The number of cross bows used varied upon the size of the roof and model of the car. Generally, there would be at least two cross bows in addition to the header bow.

Header Bow: One key element of a convertible top frame is the header bow. Header bows have been constructed from wood, steel, aluminum, and even ABS plastic. The header bow is the leading component of the convertible top frame and it serves many functions. Latches mounted on the header bow secure the top frame to the windshield of the car. The convertible top cover material is also fastened to the header bow along with a weather seal that helps keep out the wind and rain.

Cross Bows: Support for the top material comes from the second and third bows. They are usually smaller than the other bows, yet they are equally important parts of the top. The convertible top pads are connected from the header bow and attach to the cross bows, giving the top a smooth outward appearance. They also prevent the top material from wearing out due to rubbing against the bows.

Rear Bow: This is the last horizontal bow on the frame. The top of the rear curtain attaches to the rear bow along with the back ends of the protective top pads. The rear bow also defines the rear roof line and is adorned with a decorative trim that conceals the fasteners across the outside of the top.

To allow for additional passenger room in the cab of the car, the rear bow on a two-piece top frame is also set higher, allowing for the separate rear curtain. This rear bow is designed to support the extra weight of the panel containing the glass or clear vinyl window.

Every convertible top frame has bows that help define the roofline of the car, and they are essential to the support of the convertible topping material and protective pads. While adding to the stability of the entire frame, each bow performs a specific job.

The height of the rear bow is also critical to the function of the folding top. An incorrect height for the rear bow can result in the top not fitting the car properly. It may cause damage to the rear curtain when the top is lowered into the well of the car.

Side Rails

Convertible top side rails are usually comprised of three separate members. Smaller links are attached to the side rails to help them articulate properly. Each side rail runs parallel to the cross bows and forms the outer perimeter of the top frame.

The hydraulic-powered cylinders are attached to the side rails and aid in raising and lowering the top. Also attached to the side rails is the rubber weatherstrip molding. This molding prevents wind and rain from entering the car.

Top Cover

Unlike a sedan or coupe, the convertible has a soft top. A fabric or vinyl covering forms the actual roof over the articulated frame of the passenger car. This material was most likely made by the Haartz Manufacturing Company.

A convertible top cover is specifically tailored to fit the frame of the car so it can fold without tearing. The sewing and seaming process also strengthens the top, allowing it to conform to the shape of the frame.

Two-Piece Top: A standard two-piece top refers to a convertible that has a separate rear curtain. This curtain can have a window made of heavy-gauge clear plastic or a piece of tempered glass. Many of today’s late-model cars are fit with a curtain that is made of glass, and it may also have an electric heating element feature built into them to keep the window defrosted. This allows the car to be driven all year with clear visibility.

The rear bow is heavier in design so that it can take on the weight of the rear curtain. It also has a wider tack strip embedded to accept multiple rows of staples for the attachment of the top pads, curtain, top material, and wire-on welt.

The side rails of the convertible top frame are made up of three main sections. The smaller, flat links help tension the frame and help it return to its correct position when the top is raised and latched. The rubber roof rail seals also attach to the side rails.

This is a premade, ready-to-install convertible top just taken out of the box. The vinyl has box wrinkles and does not look at all appealing. After it is properly installed, the wrinkles will vanish, and it will become the crown jewel of the car.

Derived from early European sports cars, this classic Corvette is sporting a one-piece convertible top. The rear window is built into the top and then fitted as a single unit to the top frame. This style of top works well on smaller two-seater cars.

Almost all American-made cars were created with a two-piece top. These tops are much easier to fit than a one-piece top and are more cost effective to service if the rear window becomes damaged.

One-Piece Top: A convertible top that has the rear curtain integrated into the top is called a one-piece top. This style of top originated from European sports cars. The one-piece top is generally smaller in size due in part because they are usually found on a two-seater car.

The one-piece top is almost always manually operated because of the limited space that is available in the car. There is just not enough room for the components of a hydraulic system.

Most American cars are designed with a two-piece convertible top. The large rear vinyl window of this top is made as a separate component, and it is installed onto the top frame before the outer topping material is applied.

Curtains

Windows on a convertible are called curtains and are most commonly found in the rear panel of the convertible top. The term curtain actually evolved from the use of a roll-up window covering or curtain that was used to cover the rear and side windows in the car. The curtain was used to shade the occupants of the vehicle, and it also provided some privacy for those who wanted to park and get to know each other better.

The window in the top curtain can vary and change in size and shape with different top styles. The earliest cars had a fixed or folding top with a smaller framed glass window set into two pieces of matching top fabric. This curtain style was referred to as a double-blind curtain. The window frame and size were subject to the owner’s personal choice.

In the rear of this Pierce-Arrow is an actual curtain that is rolled up over the beveled-glass window. It was used to block sunlight and create privacy for the occupants of the car. Details like this are no longer used in modern cars.

In addition to a fitted top being added to an open car, side curtains were added to help divert wind and rain from passengers in the car. Side curtains would often roll down from the side rail and fasten to the body of the car. Removable side curtains had an internal wire frame that mounted to the door and could be stored away when they were not in use.

Pads

One of the most overlooked parts to be replaced on a convertible are the pads. Most people do not know what they are or what purpose they serve. This could be why they are not replaced with the new top material. Do not overlook the importance of the pads.

The main function of a convertible top pad is to protect the convertible top material from being damaged by the articulating frame. The pad also helps smooth the appearance of the convertible top along the top of the bows. The convertible top pads are held in place on the top frame with staples and screws.

Top pads help support the top material and keep it from falling into the car. Wide straps were used on buggies and evolved into the soft, wide pads we use today. A convertible top pad is a soft material sandwiched between the convertible top frame and the outer convertible top fabric. The construction of a convertible top pad varies by manufacturer.

Most original top pads were made up of a layer of cotton batting laid over jute webbing and then covered by a color-matched bow drill fabric. The exception is Ford, which used a heavy woven fabric on many of its convertible models. The pad still protected the top from wearing against the frame.

Modern convertible top pads are made from the same material as the top. The fabric is an exact match, making them appear invisible from inside the car. The padding material supplied with a modern pad is made of medium-density foam. The foam compresses just enough to create a smooth appearance and yet allow the correct amount of protection needed for the outer top.

The convertible top pad is the unsung hero of the convertible top. This simple component separates the top material from the underlying metal frame. It allows the top material to move and flow without being damaged when the top is folded.

An original convertible top pad was constructed of bow drill cloth with a base layer of jute webbing material. The inner padding was made of cotton batting. Modern pads are made from convertible top material with a foam inner liner.

Top pads vary in shape, width, and length, depending on the frame and model of car that is being worked on. Pads are simple to make, or they can be ordered with the top for your car.

Rear Pads

Some car models require an additional set of pads in the rear-quarter section to help give the top a nicer shape. Without the additional pad, the top would develop a gaunt or starved look with the rear-quarter section of the top curving inward. These pads are constructed the same way as the main top pad, and they are attached to the rear tack rail, extending upward, and are secured to the rear bow.

Some car models are equipped with rear pads. These special components help round out the rear sail area of the convertible top to give it a full and rounder appearance. They stretch from the rear bow down to the rear tack rail.

Hydraulic System

Not all convertibles have a hydraulic system. Early convertible top frames were manually raised and lowered. These tops were best operated with two people until the addition of heavy-duty assist springs, which made the task of raising and lowering the top much easier.

As cars evolved and luxury became an important part of the driving experience, power windows, power seats, and power tops were much more desirable and became a necessary option. A typical power system consisted of a motorized pump, high-pressure hoses, and hydraulically driven cylinders to make interior parts move with the touch of a switch. The power top made it possible for just one person to raise and lower the top and never leave the front seat of the car.

This is a typical hydraulic pump found behind the rear seat of a convertible. The simple components that make the top go up and down on a modern convertible include a hydroelectric pump, high-pressure lines, and lift cylinders.

Well Liner

The area located behind the rear seat of the car is referred to as the well. When the convertible top is lowered and folds into the down position, it is stowed in the well. The well liner is actually the material that protects the top from the hard surrounding surfaces of the well area.

After World War II, when car bodies and the convertible top styles changed, the convertible top began to lower into a space behind the rear seat. This area was also open to the trunk area of the car. The modern-style well liner now refers to the sewn material that separates the trunk from the cab area.

When the convertible top is lowered, it is stowed behind the rear seat in the well area of the car. The durable cloth material of the modern well liner separates the space between the cab of the car and the trunk.

Rain Gutter

A vital component to the preservation of the body on a convertible car is the rain gutter. The convertible top is designed to be water resistant, and since rain is a part of the driving experience, watershed and seepage is inevitable.

In an attempt to prevent the inner structure of the car from rusting, channels or gutters were added into the beltline well area of the convertible. They help redirect any water that is not shed by the convertible top to an opening in front of the rear wheel well. It then exits the body through a weep hole underneath the car.

The gutter system can consist of a metal or a plastic channel that is welded or screwed to the upper inside of the well area. The gutter should be checked periodically for debris and cracks. Any problems found should be repaired as necessary so that the system will continue to perform as it was designed.

The rain gutter is found inside the well area of your car. Its main purpose is to divert water out of the car and prevent the cab from flooding during a rainstorm. Rain gutters can vary in design and material, but they are all designed to do the same job.

Weatherstrip

To keep the wind and weather out of the car, rubber seals are attached to the side rails of the frame. These rubber seals make contact with the glass to help keep the cabin of the car weathertight. The problem with all convertible tops is that the frames are hinged, and they will leak air and water at any connecting joint. It is because the top is not rigid that the best weather seal that you can hope for will be about 85 to 90 percent.

Not all rubber weatherstrip roof rail sets are good. Some fit better than others, and the quality of the rubber varies greatly among manufacturers. The better-quality weatherstrip that you can buy is soft and pliable. The rubber will compress and allow the frame to latch without difficulty and yet be rigid enough to hold its shape and spring back to seal against the side glass. As the rubber ages, it will begin to get harder and develop cracks. This condition will also cause leaks and make the top more difficult to latch.

Some of the higher-end classic cars have weather seals that are covered in a matching bow drill cloth. Even though they worked the same as the plain rubber weather seals, the bow drill cloth did not have a function other than to give the car a finished and tailored look of luxury along the length of the outer frame rail.

Keeping the car dry on the inside is accomplished with high-quality rubber weatherstripping. This is a basic roof rail weatherstrip kit. It contains the side rail pieces along with a form-fit header seal. It is always wise to install a new roof rail set with your new top.

Sometimes the rubber weather seal is covered in a fabric that matches the interior lining of the convertible top. This treatment of wrapping the rubber in bowdrill cloth is strictly a cosmetic detail used on higher-end cars.