Gelcoat Question
Thread Starter
Intermediate
Joined: Aug 2016
Posts: 35
Likes: 5
From: Scottsdale, AZ
Gelcoat Question
I'm making some body repairs on my '69 convertible. Since it is gelcoated, do I need to finish repairs with gelcoat or is a thin coat of bondo ok before primer?
Melting Slicks
Joined: Nov 2006
Posts: 3,358
Likes: 1,782
From: Apple Valley, MN
The purpose of gelcoat arose during the manufacturing process where a smooth surface finish was desired and the old methods of hand-layup of fiberglass matte wasn’t providing the needed results. The gelcoat is applied to the mold first, then the fiberglass/resin. FRP and SMC panel fabrication processes are such that the use of gelcoat isn’t necessary.
The use of a high solids primer surfacer, in effect, is a substitute for the gelcoat. It affords the ability to localized repairs and is the standard for providing a suitable substrate for the top coats. Using polyester based products are more compatible with the polyester resins that were used in the production of the FRP panels on the 72 and earlier cars. For the SMC panels that were introduced in 73, you can still use a polyester product but epoxies are generally selected in these applications. That said, many people use epoxies on the earlier cars and there’s nothing wrong with that-more a matter of personal preference.
The use of a high solids primer surfacer, in effect, is a substitute for the gelcoat. It affords the ability to localized repairs and is the standard for providing a suitable substrate for the top coats. Using polyester based products are more compatible with the polyester resins that were used in the production of the FRP panels on the 72 and earlier cars. For the SMC panels that were introduced in 73, you can still use a polyester product but epoxies are generally selected in these applications. That said, many people use epoxies on the earlier cars and there’s nothing wrong with that-more a matter of personal preference.
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