Sanding epoxy

Quite a few previous posts on this forum have suggested sanding epoxy after a long delay between coats in order to promote a better bond. My question is this: Does sanding simply roughen the glossy surface or is there another reason? I am returning to my WD10 hybrid after a year hiatus (you know how it is with multiple projects) and am not sure whether to sand. The cockpit fiberglassing is complete, the stern section is tacked, and the transom is filleted. I have not filled the weave in the cockpit so am hesitant about sanding there for fear of sanding into the fiberglass. And it is not glossy since the weave itself provides some roughness. Is that enough? And the fillets in the transom -- Is there any reason to sand them?

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RE: Sanding epoxy

Before the resin has fully cured, a new coat can make a chemical bond with the one below it, but once that lower coat has fully cured, the new coat can only make a mechanicial bond.  Sanding increases the surface area and gives the old epoxy a "tooth" for the new to hold onto

RE: Sanding epoxy

If I could just finish my thought before i hit post.

In the case of glass with no fill coat on it, and just needing to "fill the weave" not make a structural bond, I would not sand

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