By Chris Wantuck
Can there be a product on the market that solves many of the problems we encounter when restoring our antique autos? Is there a "universal" way to tackle wood, metal, filling, sanding, and finishing for structural and cosmetic problems? Kwik Poly maybe that product.
Carrying over from the manufacture of wagons and stage coaches, early auto manufacturers often used wood as a means of providing a frame for the body and this practice was common well into the 1930s. Wood was plentiful, it could be cut, shaped and joined together using available tools. Depending on the era, the exterior of this wooden frame was covered with aluminum or steel sheet metal (and in rare instances fabric) where it could be easily nailed along the edges. Only in the late 1930's did wood eventually give way to all-steel bodies, but wood continued to be used as either trim or for fastening interior trim moldings.
Restorers of these collector cars are faced with the likely possibility that over the decades, the wood has rotted and and will require repair. This article examines a liquid (epoxy) type product called Kwik Poly, its many features and uses. As an example of it's ability to solve difficult problems, we will show you how to repair a body frame rail (sill) that has rotted where it mates with the chassis and body shims.
Kwik Poly is a Polyol product using two agents, a base and a catalyst. It is packaged in two separate metal containers, each having a viscosity similar to water (Photo 1). It has a mixing ratio of 1:1, equal parts of the base (Part A) and the catalyst (Part B). Thick or thin, Kwik Poly can be used as a combination filler, coating or bonding agent. One practical tip is to dispense Kwik Poly into smaller size containers for use around the shop and use small plastic pipettes to dispense Part A and B in equal amounts (Photos 2 & 3).
Photo 1: Kwik Poly Parts A (red) and B (blue), a few 30 cc mixing cups, disposable flux brushes, and disposable gloves are included in each kit. Durham's wood putty (purchased locally) is used as a general filler.
Photo 2: Kwik Poly is filled into small glass bottles for easier dispensing around the shop, maintaining the same Part A (red) and Part B (blue-black) legends for the bottles and the pipettes. Each bottle has its own drinking straw taped to the side and each pipette is colored with a Sharpie marker to avoid contamination. Also shown are wooden coffee mixing stirrers, 7 ml pipettes, and 3 Oz paper cups. Pipettes range in size from 3 ml to 30 ml and are available at hobby stores and directly from vendors offering chemistry supplies.
Photo 3: Small and larger syringes (such as a deep fried turkey flavor injector) and larger size pipettes are helpful when applying Kwik Poly into hard to reach areas.
When Part A and Part B are mixed together it creates a thermo-chemical reaction that will cure in approximately 5 minutes; it will be cured enough to be handled in about 10 minutes (or less) and full cure is well under 12 hours.
The low viscosity of Kwik Poly makes it ideal for wood and other porous materials. It absorbs well into the wood fibers and makes a strong bond, not just on the surface, but deep into the wood material. It adheres to wood or to itself, which allows for it to be applied in layers — an especially important benefit when building up a particular area. It can be tinted with dry pigments (Photos 4 & 5), mixed with various dry fillers such as Durham's Wood Putty powder or your own fillers such as fine saw dust (Photo 6).
Photo 4: Kwik Poly can be tinted using dry additives. Shown is an assortment of non-toxic dry pigments from Earth Pigment Supply. A little goes a long way in coloring KP and requires thorough mixing.
Photo 5: Two small batches of KP are mixed with two different color pigments Burnt Umber and Pistachio Green to illustrate its ability to be tinted.
Photo 6: Another example of adding dry material to KP. A small batch of KP is mixed with fine oak saw dust (recovered from a belt sander).
Photos 7 & 8 show the results of mixing Kwik Poly with white powder (from the powder coating trade) and its ability to form/cure around the threads of a 1/4 X 20 bolt. Aluminum powder was used as a dry mix to repair a fractured aluminum light pole (Photo 9).
Photo 7: Kwik Poly's low viscosity sets well around intricate shapes or small areas. Here a 1/4 X 20 bolt was immersed into a batch of KP that included white powder from powder coating. The shrinkage around the threads required a wrench to free the bolt.
Photo 8: Close up picture of the bolt and threads left in the white sample.
Photo 9: An aluminum light pole was damaged when a tree fell onto it. Kwik Poly mixed with aluminum powder and steel shavings (from a lathe) was used to make the repair.
Other possible fillers are steel shot or glass shot granules from the glass bead cabinet. Adding fillers increases the mixture volume, improves its cured strength and provides a texture of the desired application (e.g. aluminum in Photo 9). The amount of filler added depends on the application, a little to provide some extra body to the joint or cavity to a hefty amount where the mix has the consistency of a paste.
Applying Kwik Poly to vertical surfaces requires a little thought and preparation. Photo 10 shows a vertical wooden piece with a hole (from a stripped out wood screw) and a means to make a trough to pour the mixed Kwik Poly to completely fill the damaged area.
Photo 10: Kwik Poly can be used to fill holes in vertical surfaces by creating a dam or trough around the hole while kwik Poly is poured. The excess Kwik Poly can be sanded down after it cures.
Cured Kwik Poly Polyol can be sanded, shaped and even polished using rotary tools such as a Dremel.
Kwik Poly can also be mixed with colored pigments at different times. One color can be added to a single mixture of Polyol or two different mixes of Polyol having two different colors can be prepared. The intent of the multi-color multi-mix is to inlay a different color mix just as its curing. Swirling the darker color into the lighter color just as the Polyol is setting recreates colored lines in plastic type repairs (such as steering wheels). Start with dispensing the required amount of Part A and add the desired filler or pigment and mix thoroughly. When ready, add the appropriate amount of Part B into the mix and again mix thoroughly. If doing a two part repair, time the points when mixing Part B into each mix at 60-90 seconds so that the base color cures slightly ahead of the accent color Polyol. When the base is nearing set-up, simply swirl in the accent color. Photo 11 shows a white and black sample.
Photo 11: Example of white base and black accent two tone Polyol mixed in a paper cup. Timing of the mixtures is important. The black was added as the white was beginning to set.
Car bodies that have a wooden frame usually are built on substantial structural pieces on the left and right sides called frame rails or sills. Depending on the car manufacturer, the body rests on special fibrous shims that are wedged between the underside of the body and the chassis metal frame. The number of locations along the body frame rail where shims are inserted can vary, but five to seven per side are common. Adding or removing the number of shims at each location will effect the alignment of the body to the hood and more importantly, the alignment and spacing of the doors. On a sedan for example, adding shims under the front door post "pushes the door" upwards in the event of a sagging door.
The wood rotting out at the point where the shim is located is a common problem. There are probably several reasons why this occurred but the most plausible is the fibrous shims retained moisture. The result is the shim stack collapsed into the cavity created by the rotted wood or a secton of the body is resting on the chassis frame (Photo 12). Since shims play such an important role in overall body alignment, the wooden area must be repaired, hopefully without disturbing to the remainder of the body frame rail/sill. Repair of a rotted sill traditionally required the removal of the rotted wood and custom forming a replacement piece. That is if you can get to the effected area.
Photo 12: Cross section side view of a typical body wooden sill resting on a chassis and body shims that have fallen into the rotted wood cavity.
With a bit of special preparation this repair can be made using Kwik Poly as a filler. The body bolt and nut assembly are removed and the body is lifted slightly to permit the placement of small blocks of wood in front and in back of the area to be repaired. These small blocks temporarily carry the weight of the body while keeping it relatively aligned.
Next a thin piece of 1/8 inch Luan plywood wrapped with several layers of wax paper is wedged into the underside of the area to be repaired. The wax paper prevents the Kwik Poly Polyol from adhering to the plywood, which will be removed after the Polyol has cured. Depending on the cavity to be filled, small amounts of cotton can be wedged at the very front and rear of the cavity where the plywood meets the underside of the body to act as a seal for the Polyol (Photo 13). An alternative is to form a ring of Pla-Doh putty placed on the wax paper to seal the area. The intent here is to pour the Polyol into the existing body bolt hole and fill the cavity from above. Any area where the Polyol can seep out needs to be sealed and every repair is slightly different. The cotton trick seems to work well. While pouring the Polyol into the hole, make sure it is "topped off" at the top of the hole. You want to be sure that the cavity gets completely filled.
Photo 13: Cross section side view of prepared area. Body is temporarily supported by wooden blocks and Luan plywood coated with wax paper with cotton wadding is underneath the sill to hold & contain the Polyol while it cures. Polyol is poured in through the existing bolt hole.
After the Kwik Poly Polyol has completely cured, the hole can be drilled out and the correct number of shims needed to correctly align the body can be installed. (Photos 14 & 15).
Photo 14: Cross section side view of the repair after the Polyol is cured (24 hours is recommended), the hole has been re-drilled and shims put back underneath.
Photo 15: Cross section rear view of the same repair.
When deciding how much Polyol to mix, estimate the amount needed to fill the cavity plus a bit more. It's better to have a little left over than to not have enough. The viscosity of the mixture of Polyol should be as low (pourable) as possible so care should be taken with the amount of filler added. If you have access to the underside, one suggested method is to lightly coat the inside area of the cavity with a coating of Polyol (containing no filler) using disposable flux brushes. This coating will promote adhesion for the filler.
Some practical tips working with Kwik Poly include:
Kwik Poly LLC,
300 St. Cecelia Court,
Old Monroe, MOÂ 63369
The Earth Pigments Company,
PO Box 1172,
Cortaro, AZ 85652