I have a curved area on fibreglass with a dent in it. I have filled it with body filler but when I sand it back there is still an obvious ridge where the filler meets the body. I have sanded it down and repeated this many times but still get the same result. I have tried course and fine sand paper but each time I apply primer the ridge is obvious.

Does anyone have any tips on how to overcome this?


2 Answers 2


Years ago we used something called "red putty" it is made by 3M available at autobody supply shops.. It was applied over the bondo. It acted like a thick primer that came in a can. It was smoother and thinner than filler so the edges feathered smoother.


I got a tip from a friend that was also helpful: wet the sand paper and use a wide circular motion over the area with light to medium pressure. Keep dipping the sand paper in the water to remove build up of grit. Repeat with varying degrees of course to fine sand paper.

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .