Background

The raw aluminum panels provided in the Smyth Ute kit can be assembled “as is”. However, there are a number of refinements that enhance both the appearance and robustness of the build. Multiple trial fitments are suggested to determine exactly what needs to be done.

The first task is to drill out all the small pierces to accommodate M8 bolts. The M8 diameter is 0.315″ so a 3/8 drill bit (0.375″) makes a sufficient hole. However, it may be advantageous to drill slightly smaller holes — 11/32 bit or 0.344″ — for a more precise alignment. Note that 5/16 bits (0.313″) are too small.

The only pierces that should not be drilled to fit the M8 bolt are

1. the two pin holes for the rotating hinge on the side walls
2. the lower row along the front wall that is designed for 3/16 rivets
3. (optional) cabin-facing and two most-forward front tray holes if removable
4. (optional) front wall holes for removable front tray

Side walls

Fender arch brace

Arch brace protrudes near the bed floor support

Very early New Beetles lack any fender brace. After a few years of real world road use, VW engineers apparently concluded that some additional support was needed so a complex curved arch was added in the early 2000s.

After 2005, the arch was re-engineered again and enlongated! Unfortunately, the location of this brace interferes with the placement of the side walls.

Without access to the engineering work behind this design, it is impossible to ascertain exactly what structural role this arch plays, but it surely looks important! For post-2005 cars there isn’t much of an option: the arch just has to be bashed in enough to make the side wall fit. A bit ugly.

However, for pre-2006 models including our 2004 Turbo S, there is another approach: namely fit a wood floor to hide about an inch of arch brace “invasion”. (There are other very good reasons to install a wood floor, including esthetics.)

Wood floor cutaway for fender arch obstruction (not to scale)

A wood floor with 3/4″ planks (actual thickness is 16mm or 5/8″) plus an angle bed strip (about 1.5″ width) is enough to hide the cutaway.

Cutaway detail around arch brace

The wood plank is offset from the wall by about a half inch so it should lay flat without a problem. Perhaps some minor filing on the inside of the strip may be required (but not enough to impact any structural stability or alter the visual appearance).

End flange

The side walls terminate in an 1/8″ edge that butts up against the fiberglass quarter panel. Adding a riveted flange fabricated from 1×1 aluminum angle provides a better surface for mating the fiberglass shell to the truck bed frame.

Pie cuts (larger one near M8 bolt hole) help match end curvature

“Pie cuts” can be made in the aluminum L-angle to better match the slight curvature of the side wall end.

Riveted end flange matches end curvature

An end flange also adds stiffness to the edge for better cable connection stability. Take care to make the “pie cut” near the cable attachment hole large enough to clear the M8 bolt and washer.

Trial fitment

Multiple trial fitments of all the panels is highly recommended to refine minor points of conflict. Common issues are

1. impact bumper and flange notches at the end of the bed walls

Rear impact bumper notch needs enlargement

2. fender flanges and studs that touch the side walls
3. front wall bottom tabs that may a little too long and hit the chassis

Front wall bottom tabs may hit the chassis

4. right fender bump (wheel side indent where fuel lines are routed)

Right side fender bump out may need hammering in

In addition, aluminum edges should be sanded to allow easy fitting of U-channels and other braces.

Front tray

The entire truck bed frame can be bolted together off the vehicle and then installed as a single assembly. Assuming all the fitment trials have been done and suitable adjustments made, the assembly should fit well. However, there is one singular disadvantage to this method: the front tray prevents access to the chassis near the front wall, and as a result, carefully sealing the gap between the inside cabin and the front wall is virtually impossible. The best that can be done is to reach in with a finger of sealant and hope all the crevices are filled in.

If the front tray is fastened with M8 bolts per kit instructions, the tray then cannot be removed because the four bolts along the front wall and the two side bolts nearest the front wall are not accessible. An alternative is to substitute nutserts (or rivnuts) so that these bolt hole locations can be easily reached without the need to fit nuts.

With a removable tray, the bed can be assembled first without the tray so that all the gaps along the front wall can be completely filled and sealed.

Front wall

The top railing of the front wall is the only horizontal surface not covered by fiberglass and/or separate rail top caps.

Polished SMYTH logo lettering on front wall

The “SMYTH” cutout logo needs filing and sanding for a finished look. Also it’s easier to polish up the exposed aluminum rail before assembly; protect the finished surface with tape.

If 1/4-20 rivnuts will be used in lieu of M8 bolts (refer to Front tray discussion above), drill the four tray holes to fit 1/4-20 bolts. Alternatively, nutserts can be used to accommodate a bolt size larger than 1/4″. Also drill the bottom row of holes for 3/16 rivets.

Exterior bed lights

If exterior bed lights are planned, drill a wiring access hole in an appropriate hidden location. Fabricate an appropriate mount for the light fixture.

Some LED light bars have magnetic strips for mounting, but these will not work on aluminum unless a steel strip is added (see galvanic corrosion). If magnetic mounts are not used, some sort of bracket or suitable adhesive will be required. Make sure to plan for easy removal of the light for servicing.

Speaker cutouts

If speakers will be installed in the back wall (recommended), then mark and cut the appropriate holes as close to the center and top as possible: horizontal movement towards the center is limited by the side walls and vertical movement up is limited by the step side indentation in the fiberglass quarter panel.

While it is possible to fit 6.5″ speakers, the grille tends to conflict with the interior side panels. A more comfortable speaker diameter is 5.25″ (hole cutout is typically about 4.5″).

Surface treatment

As previously discussed, there are a number of options for treating the exposed surfaces of the truck bed (two side walls, front wall, and tailgate inner skin).

Follow these steps for a bed liner option.

1. sand all exposed surfaces with 150-180 grit to remove imperfections
2. clean surfaces with panel wipe or appropriate substitute
3. spray on aluminum etching primer (Raptor UP5023)
4. clear surfaces again with panel wipe
5. mix tintable Raptor (UP4802) with binder-free paint
6. lay the panels flat and apply liner with rollers
7. in corners and hard-to-reach areas apply liner with brush
8. repeat steps 6-7 as required to get desired coat thickness

Galvanic corrosion

The combination of aluminum and stainless steel causes galvanic corrosion; the Smyth kit truck bed aluminum panels and stainless steel fasteners will interact unless there is a non-conductive barrier between them. As discussed above, a surface treatment like Raptor on visible truck bed aluminum panels mitigates the problem somewhat, but all (hidden) bolt holes where there is aluminum/steel contact should be coated with primer first before assembly. For added protection, paint the zinc-coated washers in the Smyth kit with primer.

The aluminum surfaces under the tailgate latches and hinges should also be coated with primer, especially if the tailgate aluminum skin is not painted (that is, left “raw”).