The Process

It is apparent that the bottom sheeting of the GT40 tub must be removed to properly restore and preserve the structure. The hidden areas need to be completely opened up and cleaned to bare metal. Necessary repairs can then be made and the chassis treated with a rust-inhibiting epoxy coating before re-assembly. A GT40 tub reconditioned in this manner will resist corrosion indefinitely.

Removing the bottom sheeting prior to cleaning requires several days to drill and grind thousands of spot welds. A simple rotating frame holds the tub during this tedious process.

The tub is then mounted in a larger fixture for the trip to the stripper's shop. This fixture provides protection during transport and hoist points for handling. Also, the sheet metal of the tub is far too thin for proper electrical connections for electro-chemical stripping. The heavy steel tubing of the fixture provides a good deal of surface area for the connection and transfers the current through numerous pickup points all around the tub. The multiple attachments ensure even cleaning action and eliminate the possibility of a current burn on the 0.035" thick sheet metal.

GT40 Tub on Fixture
Figure 1 - GT40 tub mounted in disassembly fixture
with sheeting removed.
GT40 Tub in Transport/Stripping Fixture
Figure 2 - The additional structure on this cleaning fixture
surrounds the tub during cleaning.

Chassis cleaning can be acomplished by media ('sand') blasting, an abrasive process, or by chemical stripping. The stripping operation consists of a chemical solution to remove old paint and coatings, then an electro-chemical process that removes the rust, followed by a rinse operation. Again, it is most important that the outer sheeting of the chassis be removed to allow both complete penetration of the chemical baths and proper drainage. Any chemicals that remain trapped in the structure will restart the corrosion.

GT40 Tub Being readied for stripping. Figure 3 - GT40 tub being readied for a swim.
Into the Stripper's Vat Figure 4 - Down it goes...

Cleaned and Drained...Ready for Repairs
Figure 5 - The tub emerges ready for structural refurbishment.

Repair and restoration of the GT40 monocoque chassis frequently involves creating many complex stampings to replace those lost to time. It is important that the replacement parts duplicate the originals exactly in all details, not only for fit and finish, but also to restore the strength of the original design. Shortcuts in rib stampings and bead forming can greatly diminish not only historical correctness but the structural integrity of the chassis.
Fuel Sponson Ribs Figure 6 - A group of fuel sponson ribs are produced...
Rib Welding Figure 7 - ...and welded in pairs with dozens of correct spot welds.

Fuel Sponson Top Sheet Figure 8 - New top rocker sheets with correct size and shape reinforcing beads...
Ribs Welded to Top Sheets Figure 9 - ...have the ribs added using authentic spot welding patterns.

A technical gem is hidden in the details:
All original 1960's GT40'S had formed reinforcing ribs along the length of the fuel sponsons. These ribs measured 1.060" wide by 0.240" high (+/- a few thousands for manufacturing tolerances). If a GT40 tub does not have these specific dimension reinforcing ribs then it is either not an original 1960's GT40, or the fuel sponsons have some non-authentic replacement outer panels.

Sponson Sheets Figure 10 - Authenticity demands correct radius
and contour be used in stamping...
Sponson Sheet Detail Figure 11 - ...the stiffening ribs on this sponson top sheet.

Rocker Sheets Figure 12 - New die-stamped rocker panel skins with correct beads, tapered flange and pinch weld plus...
New Floor Pan Figure 13 - ...and a newly stamped main floor pan with the correct rib pattern.

A third fixture is used during reassembly. This heavy (1500 lbs.) fixture consists of a main structure of 4"x8" rectangular tube with 3" and 4" square tube connectors that locate the tub at 20 pickup points. The stout structure holds the critical alignment geometry of all of the chassis' dimensional and structural points as the structure is reassembled.

This fixture is mounted on a mobile cart & it can be rotated 360 degrees for access to all areas of the tub during the structural panel replacement and welding process.

Assembly Fixture [Top] Figure 14 - The massive assembly fixture holds everything
in alignment.
Assembly Fixture [Bottom] Figure 15 - The thousands of welds complete
the restoration of the structure to its
original torsional rigidity of an incredible
12,500 pound-feet per degree.

Bottom View GT40 Tub
Figure 16 - The refurbished tub structure
with the appearance and strength of the original.

In addition to repairing corrosion damage, even more complex "Bits & Pieces" may need to be fabricated to repair evidence of the "Car Wars".

As is always the case, each assembly is constructed exactly as original.

Newly stamped and formed Greenhouse top sheet
Figure 17 - Newly stamped and formed
Greenhouse top sheet
Front Rail Stamping
Figure 18 - Front Rail Stamping

32 Pieces are required for this rear crossmember assembly
Figure 19 - 32 Pieces are required for this
rear crossmember assembly
Sponson Bulkhead Assmbly
Figure 20 - Sponson Bulkhead Assmbly

Miscellaneous Panels Exactly as Original
Figure 21 - Miscellaneous Panels Exactly as Original
Replacement for a Damaged Firewall
Figure 22 - Replacement for a Damaged Firewall

GT40 Center Tunnel Stamping
Figure 23 - GT40 Center Tunnel Stamping
Stamped & Assembled GT40 Bulkhead
Figure 24 - Stamped & Assembled GT40 Bulkhead

New front clip insert
Figure 25 - GT40 front clip insert is fabricated
by pains-taking english wheel work...

Assembled & Primed with Protective Epoxy Coating
Figure 26 - Assembled & Primed with
Protective Epoxy Coating
Bottom View
Figure 27 - Bottom View

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