Tiger 700 Project: #25 Building the Body: Plaster & Epoxy

[@ryale7174]

I realize that putting polyester resin directly on to most types of foam will cause the foam to melt and you needed to achieve a smooth finish. But why not use epoxy resin directly on to the foam as a barrier you can sand then build up using standard polyester resins and fabrics?

[@BillPhillips4]

Excellent question! In most cases that is exactly what you would want to do. Just build up the laminate with numerous layers of fiberglass and then apply body filler to achieve a smooth surface. The down side of this method is that the body filler adds weight and any thick sections of body filler may crack later on. The target weight for my Tiger is 600 pounds, so keeping it's body light is critical. Building the mold is a time consuming and expensive step, but eliminates most of the body filler and keeps the body light.

[@ryale7174]

@@BillPhillips4 Thank you for your response. Looking forward to seeing your videos of taking a mold from off of your "plug", and the steps involved to making it. There are very few detailed videos on doing a complete car body. Please continue with your comprehensive approach. All the best.

[@BillPhillips4]

Thanks. One more point. In an effort to preserve the fine details of my plug, I used just 2 layers of very light 2oz layers of fiberglass for the shell. This turned out to be too fragile and I experienced blisters later where the fiberglass lifted from the plaster/foam plug. I now recommend 2 layers or 4oz - 6 oz fiberglass at a minimum. Quick update: I'm a little behind on posting videos, but will post soon. I have completed the molding process, which yielded a 16 part interlocking mold. I've started building the final body panels from the molds as well.

[@ryale7174]

@@BillPhillips4 Bill, this may be the "old" way of making a plug....but making a finished shape made from smooth and painted joint compound over an armature was the way to go. I don't fully understand the multiple layers for just a plug. It seemed to me that you were going to do moldless construction. When you have a moment please explain your thought process...I am flipping back and forth between moldless construction vs the "traditional" male plug...female mold...finished panel approach. However, there is an appeal of a precise finished product that can be reproduced multiple times.

[@BillPhillips4]

R Yale, In the vast majority of cases, moldless is the way to go for a one-off custom body. Building a mold is time consuming and expensive, so you should have a good reason to justify going that route. The key reasons for molded construction are a need for a light weight body or you want to make multiple copies. Each of the layers in the plug had a purpose: 1. Plywood: Solid foundation to attach the plug to the chassis 2. Foam: Quickly fill out the rough shape of the body. 3. Joint Compound: Refine and smooth the shape. It is possible to build a body from this step, but I have found that plaster is a bit soft to get well contoured and smooth shapes. 4. Epoxy resin: Protects the foam from the polyester resin. It is possible to skip step 5 and simply use epoxy resin to set the fiberglass. However, epoxy resin is more expensive than polyester. 5. Polyester resin and fiberglass: Provides a hard shell to enable effective block sanding. This is the point where you can choose to go with mold-less or molded construction. If you want to go moldless, just apply more layers of fiberglass. 6. Gelcoat: This an optional layer, but it reduces the amount of body filler needed to smooth the surface and reduces the risk of thick body filler cracking. 7. Body filler: Refine the surface with a thin coat.