SL-C Manual: Accessibility & Usability
If your car does not have a floor under the fuel tank, consider fabricating one, or buying one from the factory. You could use tapped holes and bolts, or use Dzus fasteners. Welding would provide somewhat more rigidity at the expense of easy removal.
A floor in this area reduces the risk that an errant stone or other debris thrown up on the road could puncture the fuel tank, and may also help to reduce noise.
The optional lift kit typically lifts one end of the car (the front, normally), but additional rams can be obtained to lift the entire car if necessary. Most SL-C owners find that the front end lift is adequate, as there is very little rear overhang, and normally sufficient ground clearance.
Due to the space that the hydraulic rams take up on the shock absorbers you will need to fit shorter springs to accommodate them. The optimal spring length is 4” when using the lift kit, though some builders have reportedly found 6” springs to work. Alternate springs can be obtained from the usual sources like Hyperco, Eibach, Swift, and QA1.
Begin with the same spring rate as your kit has originally. Most springs have a tag of some sort, are marked on the spring with paint, or have the spring rating engraved on the spring tang. Additional springs in a wide range of spring rates are readily available. Contact the factory if you need assistance finding these springs.
On the front, the rams can be fitted on top of the springs or below the springs. On the rear, the rams can only be run on the bottom of the shock. Below are photos of an example installation.
The preferred mounting position is to have the rams mounted on top of the spring, opposite to the picture above. This places the rams in an unsprung position, puts the grub screws where they are most useful for bleeding and improves access to the fittings. Either way will work, but mounting at the top of the spring is the optimal solution.
The next picture shows how the rams can be used to lift not only the front of the car, but also the rear, in cases where that is desirable. For most situations, just the fronts need rams as the rear of the car has very good approach and departure angles, unlike the front. However, rear-mounted rams can improve ground clearance at the back of the car in cases where that is needed.
Note the location of the pump in the following picture. This is a typical installation, though the pump is mounted on its side. This is acceptable, but the pump manufacturer recommends a “motor up” configuration.
Plan your installation to keep the lines as short as reasonably possible.
The next photo shows one possible mounting hole placement for the reservoir (top) and the mounting holes for the hydraulic pump.
The pump unit has 3 ports in it. The “R” port is for connection to the fluid reservoir. Plug one of the remaining ports (either A or B) and using a “T” connector, pressurize the rams from the other port as shown in the picture below.
The switch supplied with the kit is pre-configured for the lift kit, and there is wiring for this switch in the standard chassis harness. It reverses the polarity to the pump to make the pump either push fluid or retract fluid. You can use the DPDT switch provided with the kit, or substitute your own. Actually wiring the lift kit is trivial- there are two wires in the front chassis harness marked for the lift pump; connect them (in either orientation- it doesn't matter) to the pump wires and that's it for the pump. The chassis harness in the cockpit already has the DPDT switch and wiring done for you, so you just have to mount the switch where you prefer it.
The lift kit rams have air bleed outlets in them, in the form of grub screws. To successfully bleed the air out, these will need to be positioned at the top of the ram. It may be necessary on the front to bleed the rams before final installation or to orient the ram so that the bleed outlets are at the highest point. If you do decide to mount the rams at the bottom of the shock, you can sometimes bench bleed the rams by opening the grub screws and pumping fluid through them until no air bubbles are present in the stream. Close the grub screws and bleed the rams on the car as necessary.
Use only a high quality 10 to 40 CST hydraulic mineral oil, and replace it every two years or so to purge it of any contaminants. If you aren’t sure where to source good quality hydraulic fluid, the manufacturer recommends a good quality power steering fluid. Never run the pump without oil as it will destroy itself in short order.
The picture below shows how to connect the system. This picture shows a newer pump design; not all pumps look the same, but all work in essentially the same manner. Your pump may not have a visible relief valve as shown here.
Note the plugged port on one side, and the use of a “T” fitting to pressurize and drain the two rams (the yellow line represents an actual braided line connection to the rams from the pump). The red hose in the picture goes to the plastic fluid reservoir.
Door Light Switches
You may want to use door switches in your car to turn on interior lights when the doors are open, etc. These can be sourced anywhere, including from cars in junk yards. There are no chassis harness connectors for these switches. If you have an Infinitybox system, they will need to be wired to a Mastercell input if you use them and the outputs programmed to use them as required. Consult the Infinitybox documentation if you have questions about this. The other default harnesses can use one or more of the extra circuits for this purpose.
Door light switches can be mounted behind the body where the door hinges will trigger them when fully closed.
Approximate positioning for the switches is 85mm up from the door opening and 42mm from the outside edge.
If you fit door switches and are using the Infinitybox electrical system to control the affected lights, the switches will typically need to run to one of the open inputs on the Mastercell.
Note that most door switches are designed for steel-bodies cars, and as such, need to have an additional wire from the switch chassis added as well as the floating wire that moves with the plunger or pin. Remember, fiberglass is not a conductor!
Insulation & Waterproofing
The SL-C cabin can be warm, or even hot, in an uninsulated car. If you have a 500 HP engine for example, it generates about 372 KW of power, most of which is actually emitted as heat. Insulate accordingly! A lack of insulation also makes for a noisier car, so insulating is a good idea to reduce noise as well as heat. The car should also be as waterproof as possible.
In general, to ensure effective waterproofing and noise reduction, you should seal every opening, and every interface between the body and the chassis, and between body parts.
There are a couple of articles on the SL-C wiki that discuss noise reduction. Those are a great source of information about structure-borne noise reduction.
This section includes suggestions for insulating against structure-borne vibration, heat and noise as well as waterproofing ideas.
For heat insulation, areas to focus on are the rear bulkhead & associated covers. The removable aluminum cover over the fuel tank can be insulated with up to 1” thick insulation, such as heavy felt carpet insulation etc. The same goes for the space in front of the upper rear bulkhead where the main rollover hoop runs. You can use the same felt material in many layers in this section. The engine side of this bulkhead should also be insulated to reduce heat transfer. A popular choice for both the rear bulkhead and other places like the fuel tank is Lava Mat, from DEI, available at Heat shield products and elsewhere.
A key area to seal is where the bulkhead (behind the insulation in the photo below) touches the body. Use a bulb seal here that clips over the edge of the bulkhead. This area can be a great source of noise and heat unless it is properly sealed. You may need to trim the aluminum bulkhead panel to ensure even fit so the seal can fit correctly.
To reduce interior noise and drumming, insulate the entire inside cockpit. A thin damping material like Dynamat works well in this regard. You should also insulate the inside of the outer door panels.
A word about Dynamat and similar materials: These composite materials usually consist of a thin aluminum sheet attached to a layer of butyl rubber or asphalt-like material. They are typically used to reduce the thrumming sound that an exposed flat panel can make, and are a great way to reduce noise in the interior, at the expense of weight. You should strongly consider applying these materials only when you are finished with the area in question. For example, many builders choose to apply this to the fuel tank to reduce transmitted noise. Best practice is to wait until all the holes are drilled, the tank in cleaned, and it is ready for a final install before you cover it. Otherwise, you may have to drill, tap, cut or shape the underlying material (the tank in this case) with the Dynamat on top. This is extremely messy, and will clog your drills, taps and other tools with rubber or asphalt that is very time-consuming to get off. Worse, seams and edges will leak the butyl or asphalt onto every piece of clothing that touches the surface. It’s usually impossible to get off, especially if it has gone through a cleaning/drying cycle. The best way to apply these materials is just before the surface is closed off. In the tank example, apply it just before you are finished there, and will be installing the tank cover in the interior. For the interior, especially the floors and walls, refrain from installing it until the interior is about to be installed. Better yet, leave it to the interior shop! Please resist the temptation to apply it everywhere early in the build- it can make it look like you’ve accomplished something very visible, but you will regret it for the rest of the build!
You should also consider sealing the sides of the body just below the doors where they meet the chassis. Below is a photo of one way to do this. You could also put this panel in a horizontal orientation and have it stretch straight outward from chassis to the body. With this method you end up with pockets that can be utilized by cutting and lining the side trim panels. This is much more important than you might think, in terms of reducing noise in the cabin.
Waterproofing should be performed by using silicone adhesive to seal all areas where the cabin section of the body seals against the chassis where it meets the interior. You should also seal the floor section to the chassis where stitch welding is performed. Also ensure that if you cut into the roof scoop inner panel, that the panel still seals water out of the interior.
As described in the Coolant Pipe section, the coolant pipes should be heavily insulated where they run through the body and under the door openings next to the cabin section.
You should install heat shield material to protect critical parts from excessive heat. Items that you should be insulating and protecting are wiring harness, shifter cables, rubber hose, body panels and fuel lines. It is also a good idea to check for sources of heat that could heat the fuel system after shutdown (“heat soak”).
It's a good idea to keep wires or plastic components away from contact with, or near the radiator. You should also make sure that all holes that are drilled into the front wall of the cabin are well-sealed.
Many builders forget to seal the top of the radiator to the body. This is a mistake, especially for powerful engines. All the air that comes into the radiator opening needs to go through the radiator, not over it. Not sealing this area lets a significant amount of air do just that. It's easy to do, and depending on how you detail that area, can be as simple as using a bulb seal.
Heat shields are generally constructed of aluminum panels lined with insulating material. The insulating material used depends on the areas being insulated and the sides that will be exposed to the heat.
One product that has tremendous heat rejection properties is TeknoFibra, available from Essex Racing and sold by the foot in 4.75 ft. widths. While expensive, it can be used in critical heat situations.
As discussed above, Lava shield mat is also a popular choice. You can also use aluminum fiberglass sandwich construction insulation that can be formed in a variety of shapes.
Clear Paint Protection Film
To help protect your new paint finish, you can apply clear paint protection film to the areas of the body that will be prone to stone chips and rubbing. You can have the film professionally installed or do it yourself at home. 3M and Xpel make this kind of film available to the home builder.
The areas you should concentrate on for stone chips are the air exhaust vents on the front sides of the body, and any forward facing area, especially those close to the road surface.
For rubbing and chafing, you should look at the areas where the front shell closes on the body just below the windshield and also on the area where the rear shell closes around the end of the roof scoop.
If you using one of the factory wings, consider using helicopter tape on the leading edge of the wing to protect it against flying debris. This tape can be obtained from a number of sources, including Pegasus.
Body Protection & Road Noise
Tires can pick up and throw road debris up onto the inner body panels causing damage. Such damage will show itself on the top side of the guards as star cracks, stress fractures etc. This is especially a problem with race tires. Optional inner fender panels are available from Superlite Cars to prevent this. Other builders have built their own from fiberglass.
Whether or not you use inner fender panels, it’s a good idea to install a barrier to protect the body from potentially damaging impacts in this area. Be sure to apply 3M or similar clear film to the back of the front wheel openings. That's the first place debris and rocks will start to destroy your paint or gelcoat.
Underbody paint finishes do help in this regard, so they are a recommended first step in protection. For more information on underbody paint finishes see the section Underbody Treatment
The material will also reduce road noise from both small debris hitting the body surfaces and reduces tire noise
If you are using the optional fender vents in the front fenders, you should protect them by installing screens or other protective material under the vents. This also helps keep large objects from coming through the vents and hitting the outside of the car body.